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Books of special value and gift books, when the giver wishes it, are not allowed to circulate. Readers are asked to re- port all cases of books “marked or mutilated. Do not deface books by marks and writing. ilies University Library fii Tidal lands, a study 3 952 8 aig i I TIDAL LANDS A STUDY OF SHORE PROBLEMS sor “MY QOUAVE WlOOd ‘AVE SHTOH ONIGVANI ‘W/O NYSNALOL PNIZLVFdS AO SHINAI Buss Vy AW “wud an WAN a TIDAL LANDS A STUDY OF SHORE PROBLEMS BY ALFRED E. CAREY, M.Inst.C.E. - Fellow of the Royal Geographical, Geological, and Chemical Societies AND F. W. OLIVER, F.R.S. Quain Professor of Botany in University College, London NEW YORK D. VAN NOSTRAND CO. TWENTY-FIVE PARK PLACE ron PRINTED IN GREAT BRITAIN By Blackie & Son, Limited, Glasgow To CAPTAIN G. C. FREDERICK R.N, A.LCE. Late Naval Adviser to the Harbour Department Board of Trade PREFACE The title of this handbook may be regarded as enshrining a solecism. The Standing Orders of Parliament, however, employ the same phrase, and in so doing perpetrate a paradox. They lay down rules regulating the deposit of plans, such plans being for ‘‘work which is to be situate on tidal lands within the ordinary spring tides”. They then go on to direct that the documents so defined shall be duly lodged at the Office of the Harbour Department, Board of Trade, and marked “‘Tidal Waters”. Ancient Roman writers betray a similar confusion of phrase. Describing the phenomenon of diurnal tides, a wonder migrants from the almost tideless waters of the Mediterranean could not fathom, they state that they were puzzled to say whether such territory was to be appropriately called land or water. Shakespeare’s index of man’s incon- stancy was summed in the phrase, ‘‘one foot in sea, and one on shore”. This work is primarily concerned with those problems which underlie the maintenance of coastal and riparian lands, and, as a factor in such control, the extent to which horticulture may be enlisted in the cause of conservation. The original charter of the Institution of Civil Engineers defines the pro- fession of the civil engineer as ‘‘the art of directing the great sources of power in Nature for the use and convenience of man”. British engineers have perhaps been somewhat apt to disregard those transformations which are capable of being vil Vii PREFACE brought about by vegetation. The chain of physical cause and effect is universal. Every dewdrop has its tidal ebb and flow, a subtle alchemy of force that links our earth with other worlds. De minimis curat Natura. Nature is conquered by obeying her, and man is but her puppet until he learns the lesson of obedience. Whilst Zidal Lands is based primarily on the results of our own observations, experiments, and practice, spread over a long series of years, we have become indebted to many persons for information and help on particular points, for facilities of access to certain localities, and especially for the provision of many of the photographs here reproduced. Among those of whose courtesy in these various ways we desire to make particular acknowledgment are: the late Dr. Sarah Baker; Dr. Winifred Brenchley; Miss Lilian Britten, of Port Elizabeth; Mr. G. O. Case; Mr. Linn Chilvers; Dr. L. Cockayne, F.R.S., of New Zealand; Mr. A. D. Cotton; Mrs. Cowles, of Chicago; Mr. E. P. Farrow; Sir Francis Fox; Dr. Somerville Hastings; Prof. Augustine Henry; Major T. G. Hill; Lord Ichester; Mr. Alleyne Leechman, of British Guiana; Mr. J. H. Maiden, F.R.S., of the Botanic Gardens, Sydney; Prof. J. Massart, of the University of Brussels; Dr. C. H. Ostenfeld, of Copenhagen; Mr. William Rowan; Dr. E. J. Salisbury; Prof. William Somerville; Prof. C. Schroeter, of Zurich; Mr. R. V. Sherring; and Mr. R. Hansford Worth. By the courtesy of the Council of the Linnean Society we are able to republish from their Journal fig. 42 and Plate XV, 2. Fig. 3 has been reproduced from the diagram accompanying Mr. G. C. Churchward’s letter published in the Daily Mail, 18th July, 1907. Cuap. II. Ill. IV. VI. VII. VIII. IX. XI. XII. XIII. XIV. Il. III. IV. Vi. VIL. CONTENTS TIDAL AND CurRENT Data - 7 * =, a THe TIDAL COMPARTMENT OF A RIVER - - THE FORESHORE - - - . = ~ THE FUNCTION OF VEGETATION - - - - Sanp DuNES - - 3 ‘ = s = = THE FixaTION AND PLANT PROTECTION OF SAND DUNES SHINGLE BEACHES AND THEIR FIXATION - Tipat Lanp RECLAMATION (WoRKS)~ - - - EROSION AND ACCRETION (WoRKS)- - -~— - Pant WINNING OF TiDAL LANDS—SALT MARSHES MISCELLANEA (CLIFFS, RIVERS, CHANNELS) - - BLAKENEY Point, NORFOLK, FROM AN ENGINEERING oF VIEW - - = L - s THE STATE AND LOCAL CONTROL - - - - COMPLEMENTARY PROBLEMS~ - = S e 2 APPENDICES List or Dune PLANTS - -~— = = Types oF SHINGLE BEACH (ENGLISH) - - PLANTS OF THE SHINGLE BEACH - - : v1 PLANTS OF THE SALT MARSH - - = é = Sat MarsH DEVELOPMENT - - - - - On THE DISTRIBUTION OF SUAZDA FRUTICOSA BLAKENEY BEACH - - x z < Point ON THE List or AUTHORITIES IN ENGLAND AND WALES HAVING Powers AND DUTIES IN RELATION TO DEFENCE AGAINST THE SEA - - = = s ws = e INDEX - - -+- += - = 2+ + = Paor 26 57 71 87 120 143 164 204 218 242 256 263 265 265 268 270 274 279 Prats Il. III. IV. VI. VIL. VII. IX. XI. XII. XIII. XIV. XV, XVI. XVII. XVII. XIX. XX. LIST OF PLATES Paag Progressive Underwater Erosion, River Thames - - 10 River Thames, Cross-sections: Long Reach and St. Clement’s Reach - e = “i . - 22 Pea Plant growing in a Water-culture Solution, with Extensive Development of Root-system - - - 44 1, The Scolt Head Dune Massive; 2. Young Dunes, Blakeney Point - - - - - + = = 58 Dunes Colonized by Carex arenaria and Salix repens, Coxyde, Belgium - = S = 2 « - 62 Wandering Dunes - - - - - = - - 66 Dune Planting at Port Fairy, Victoria © - © = & 1. Embryo Psamma Dune at Blakeney Point; 2. Wander- ing Dune at Southport - - is a! < - 86 The Chesil Bank - - - - = e * - 96 . Shingle Plants - - - - - + += = = 98 Views of Tamarisk Hedge - - - += + - += 116 Elevation of Timber Gantry for shutting up River Breach- 140 Elevation of Typical High Groyne - - - = = 140 Boundary between High and Low Salt Marsh - - - 166 Alge as Pioneers on Mud- - + - += + + 4a Obione portulacoides - - 2 2 2+ + = = 196 Clumps of Spartina Townsendss, invading Holes Bay, Poole Harbour, 1912 - - - - - = Frontispiece Spartina Townsendit - - - - : - o - 180 Hummock Development (Bouche d’Erquy, Brittany) - 190 Bouche d’Erquy, Brittany - - + 2 s é - 192 xi xii LIST OF PLATES PLaTE Pace XXI. Shingle Reclamation - - - - - - - - 216 XXII. Blakeney Point - = Z - - a = - 224 XXIII. The Beachway, Blakeney Point, looking N.E. - + 426 XXIV. Rabbit Phenomena (Blakeney Point) - = = = 228 XXV. Blakeney Point - : = = 5 = = - 230 XXVI. Landward side of Blakeney Main Beach (Marams section) 236 XXVII. Blakeney Point - 7 7 - s a = - 238 XXVIII. Hallsands in 1894 and 1904. (After R. Hansford Worth) - 248 XXIX. Hallsands in 1917 - - + - = + = = 250 Fic. om = O 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. $8) OOS SE -OMGE ER IG IS LIST OF TEXT ILLUSTRATIONS Foreign Tide Standards - - - + - - =| -@ Diagram of Prevailing Winds, Newhaven, Sussex, 1847-83 - Diagram of Subsoils, St. Paul’s Cathedral - - - = = Essex Sea-wall - - = - - - - — Cross-section of Training Wall, Tampico Harbour - - Cross-section of Training Wall, River Mississippi <= Diagram of Torquay Harbour = Ss 8 oe oe . Profile of Chesil Bank - - = - - ss “ 2 Diagram of a Plant in the Soil - - - - - - Diagram of Perennial Herb - cy ns ch wh wm: 1 Diagrammatic Longitudinal Section of Tree or Shrub - Seedlings and Mobile Ground - : 2 e Diagrams showing Relation of Psamma to an Intermittently Rising Ground Level - - - . és = Section of Sand Dune Formation, Rhyl - - - - An Early Experimental Dune Planting - - - - Diagram showing Stages in the Creation of a Littoral Dune Standard Squares for Psamma Planting - - - Proposed Coast Road, Rhyl: Tree-planting Diagram Sketch Map of Chesil Beach - - - - - - - Apposition Beaches - - - - = = = « “ Profiles of Chesil and Blakeney Beaches - 2 2s Shingle Spit with Hooks (Hurst Castle) - - = Profile through Shoreham Beach, showing Displacement of Shingle - - - - - - - Charts showing Persistence and Spread of Silene maritima - Sueda fruticosa rejuvenated from Prostrated Branches; also a twig of same, nat. size - = - - = 5 = = Mode of Ascent of Sueda fruticosa in a Travelling Beach - Successive Positions of a Single Specimen of Su@eda rruticosa in a Travelling Beach - - Ss = : 5 FEET. LONDON. THAMES DATUM TRINITY HIOH WATER + 12-50 HOLLAND PIEL D’AMSTERDAM. A.P. + 0-93. ENGLISH ORDNANCE DATUM. MEAN SEA LEVEL AT LIVERPOOL 0-00. FRENCH DATUM MEAN SEA LEVEL AT MARSEILLES. 0.00. BELGIUM. ZERO DU DEPOT DE LA GUERRE. - 6-50. IRISH ORONANCE DATUM - 7°46. SCALE FOOT fe] Ss 10 _ 3 FEET Fig. 1.—Foreign Tide Standards World, and this work is the accepted official authority on the subject. Port Establishment.—The high velocity of the great primary tidal wave is reduced when, in sailors’ parlance, ‘‘it smells land”. Thus in the North Sea it runs at 50 or 60 miles per hour. Entangled in local retardation, and subject to local dis- 4 TIDAL AND CURRENT DATA turbance, tidal travel becomes a matter of observation rather than of calculation. If such observations are sufficiently long continued, an empirical basis for foretelling the periods of high and low water at a given port may be arrived at. The interval at each port between the passage of the moon and the actual time of high water F. and C. is known as ‘‘the establishment” of that port. From this record a time-table of tides may be calculated, the conhection between the periods of F. and C. following a defined sequence. The Admiralty charts supply this information at every port. Taking as an illustration the chart of the Rivers Orwell and Stour, the following phrase will be found:— “H. W. F. and C. at Harwich XI hours 56 minutes. Springs rise 122 feet, neaps 10} feet, neaps range 74 feet.” This phrase indicates the hour of high water at Harwich at the periods of new and full moon and the amounts of mean tidal lift. The National Physical Laboratory has designed the India Office Tide Predicting Machine, which is a modification of Lord Kelvin’s apparatus now in South Kensington Museum. It can be used for predicting the tides, and preparing tide- tables, for any year, for any port for which the constants requisite for setting the machine have been determined by observation. The principle of the method may be briefly stated as follows: The tidal motion at any port can be analysed into a number of simple tides, i.e. simple harmonic oscillations of sea-level. The periods of these oscillations for the different component tides are determined from astronomical data, and are the same for all ports. The amplitudes and the phases of the several component tides are different for different ports. Twenty-four such components are included in the machine at the National Physical Laboratory. The amplitudes and phases of these twenty-four components are the constants above referred to, which it is necessary to know for any particular port in order to set the machine for predicting the tides. These amplitudes and phases are determined from actual WIND EFFECTS 5 tide-gauge records taken at the port in question. A single year’s records are sufficient to give fairly good values of the constants, but for the more important ports it is desirable to analyse a longer period, and at some ports, e.g. Bombay, records are taken continuously. The height of mean sea-level above some datum is also determined from the analysis, and is employed in setting the machine. The machine, when correctly set for any particular year, will run off a curve giving the height of sea-level above datum at any instant throughout the year. In preparing the usual tide- tables, the times and heights of the high and low waters are read off from this curve. Wind Effects.— Winds cause much perturbation in the range of tidal lift. Long-continued gales heap up or depress water-levels many feet. In the North Sea the maximum effect is produced when an N.N.W. gale is blowing, accompanied by an S.W. gale in the English Channel. This conjunction of causes in 1905 produced a tide on the Suffolk coast 6 feet 3 inches above normal. At Liverpool tides abnormal, by reason of wind con- ditions, to the extent of 5 feet have been recorded. In 1876-7 three record tides in the Thames gorged the river to such a degree that large districts within the Metropolitan area were submerged. The maximum floods reached a level of 4 feet 3 inches above Trinity. The Thames Conservancy, who then controlled riparian problems in the lower river, as a consequence of these successive floods compelled the owners of all riverside premises to raise their fronts to a minimum height of 5 feet 6 inches above Trinity standard. It is roughly estimated that a heavy gale may increase the tidal height by one-twelfth of the normal calculated height at the point of observation. Gales are usually synchronous with low barometric pressure, and it is stated, on French official authority, that a variation of atmos- pheric pressure of one inch coincides with a + or — variation of about one-third of an inch per foot of tidal range. In tropical localities wind action usually follows a well- defined cycle, the monsoons on the Asiatic coast, for instance, recurring with great precision. In temperate regions the seasonal disturbances are apt to be irregular. 6 TIDAL AND CURRENT DATA PERIODS OF GREATEST DISTURBANCE English Channel, Irish Sea, and Atlantic Seaboards wee sis ib ... November-February. North Sea __... as oe oa ... January-April. Cyclones in Indian Ocean ... aa ... May-November. Typhoons in China Sea... tee ... June-November. Hurricanes in Caribbean Sea sag es. July-October. Hurricanes in South Seas ... oa ..» January-April. The genesis of wave disturbance is wind action, and long- continued wind records are, therefore, of much value, but it SCALE DAYS 10 5 oO 10 DAYS Me Fig. 2.—Diagram showing average Prevalence of Winds at Newhaven, 1847-83 must be borne in mind that they furnish little clue to the effect produced by periodic storms of exceptional severity. Diagrams of the average prevalence of winds, as shown in fig. 2, should be plotted, where the necessary data are obtainable. Ina paper by Dr. Stanton, ‘‘On the Resistance of Plane Surfaces in a Uniform Current of Air”,! much accurate observation in respect of wind velocities is collected. Probably 90-100 miles an hour is the extreme limit of wind velocity. The pressure due to wind force is constantly fluctu- 1 Proc. last. C. £., Vol. CLVI, pp. 78-139. CURRENTS 7 ating and not a uniform and steady pressure. In the Report of the Committee on Wind Pressure on Railway Structures (1881), the following formula is adopted to indicate the relation between wind velocity and pressure :— 2 ‘_ = P, 100 V being miles per hour, P maximum pressure, the lowest value of V being 40 miles per hour. The results obtained by this formula between 40-80 miles per hour show a close approxi- mation with experimental observation. Thus, with a wind having a maximum hourly run of 80 miles, the maximum pressure by formula is 64 lb. per square foot; according to experiment, 65.5 lb. per square foot. Currents.—Current scour may be either the slave or the tyrant of the designer of harbour and river works. Dr. J. S. Owens, in a paper entitled ‘‘ Experiments on the Transporting Power of Sea Currents”,! evolved the following formula:— If d@ = diameter of a flint stone in inches, V = velocity required to move it in feet per second. 2: a approximately. For ordinary pebbles d = Fine sand #5 to y$o inch diameter begins to move under a current of 0.60 to 0.80 foot per second. 1 Journal of the Royal Geographical Society, April, 1908, p. 417. CHAPTER II The Tidal Compartment of a River The tidal compartment of a river may be defined as that portion of the stream which intervenes between the area of unimpeded tidal action and that in which there is a complete cessation or absence of tidal action. On the seaward side of the tidal compartment the accession and recession of the tides follow conditions similar to those of the contiguous open sea, unless these are modified by what may be termed acci- dental, or by local causes, such as shoals, races, or the gorging action of wind. Rain and Rivers.—There is infinite variety in the régzme of rivers, due to the contour and gradient of their bed and other physical conditions. The variations of rainfall on the earth’s surface lie between nil and about 300 inches per year. On portions of the Essex coast the average is as low as 13 or 14 inches, and the Highlander’s remark that the rainfall in his district was ‘‘aboot twelve fut” was under the mark in respect of the actual fall in some mountain districts of England. The extent to which percolation takes place varies relatively with the degree of impermeability of the subsoil, stiff clay or rock being water-arresting subsoils, whereas sand is pene- trative in a high degree, until its pores become water-logged or choked with argillaceous matter. There is a wide range in the percentages of rainfall which reach their respective river systems. The average annual percentage of infiltration in England is about 42 per cent; the mean daily evaporation is 0.08 inch. These figures, however, have little value in rela- tion to the problems of specific localities. River Contours.—The force of the ebb current in a river 8 ARTIFICIAL CUTS 9 is the principal determining factor in its contour on plan. A sluggish stream of slight gradient will be found to follow a devious course, winding across the tract of country with many bends and pools. The degree of straightness in the course of a stream is an index of its velocity and of the tenacity of the soil through which it flows to resist the impact of water. Under normal conditions a river is perpetually subject to change of contour, due to land freshets or extreme tidal move- ments, which erode the banks or bed of its stream irregularly. Approximate stabilization of a river is usually brought about by the prolonged action of natural forces. The effect of such action is a mean sectional area in the river bed, which, being protected by the accretion of detrital matter, results in slopes of repose such that the banks are capable of resisting abnormal tidal impact. The curvatures in the course of a river are due to the force of gravitation acting on the inclined plane of the surface of the stream. The measure of the force is represented by the formula g x sin 7, 7 being the inclination of the surface of the channel in degrees. h height fallen Sin z = > or oe oe ee ee Ae ee ee length under observation Z Artificial Cuts.—From the fact that the natural course of a river is curvilinear may be deduced the inference that artificial rectilinear cuts should be avoided. Works for the amelioration of a deep river channel are, as a rule, more effective if, instead of endeavouring to cut a straight course, flat curves are em- ployed. From London Bridge to the sea bends in the course of the Thames occur approximately every two miles. At Black- wall the river is about 1ooo feet wide, and its curvature has a radius of about 1900 feet. In the instances in which it has been attempted to abolish curvature in the channel of a river, the shoaling, which in- evitably takes place, tends to become irregular and produce a tortuous waterway. The fairway of a river under such con- ditions oscillates, to the detriment of navigation. The art of remoulding the tidal compartment of a river presupposes float observations spread over a considerable period. From these 10 THE TIDAL COMPARTMENT OF A RIVER the measures necessary for humouring the stream, so as to produce continuity of current effect, may be evolved. S curves should be avoided, as at points of contrary flexure shoals are likely to result. The relation between the widths and depths of the channel and the distance apart of lengths of inflexion are the cardinal features to be studied. A channel should be widest at the summit of a curve and narrowed when curves change. Dredging Disturbance in the Thames.—In the years 1906-9 the Thames Conservancy and the Port of London Authority carried out dredging operations in the Thames, whereby a channel 30 feet in depth at low water and 1000 feet in width was dredged from the Nore to the Albert Docks. Through the lower reaches of the Thames the river flows for many miles between artificial clay embankments, the land in rear of these averaging 9 or Io feet below high-water level. The standard of the Port of London Authority for the height of these pro- tective embankments is 5 feet 6 inches above Trinity high water, equivalent to 18 feet above O.D. Operations on a scale of magnitude such as those defined above necessarily produced local changes in the configuration of the river bed, owing to the varying strata underlying the channel. Plate I shows a typical fluctuation in underwater depths along one short length of the frontage of the Thames. This same frontage is now slowly becoming re-stabilized, but, as a result of the changes in contour, heavy defensive works have been rendered necessary to conserve the marsh embankments, which are the protection against flooding of many hundreds of acres of land. The river for untold ages has wandered in devious channels throughout its estuary, redistributing diluvium of a patchy character irregularly. During the Human Period the level of the river has probably been lowered not less than 60 feet, the stream having sawn its way down, leaving, tier above tier, terraces of sand and gravel. The flood-loam of ancient periods constitutes those vast areas of brick earth which now occur on both banks of the river. The regrouping of these deposits of “drift”, or ‘‘high-level gravels”, was probably the work of floods toward the termination of the Glacial Epochs. Plate I - ", Lys 2 wee | rs \ “2-2 —2 N 7 ee "2. é | Met gai oe o dias f | (sf SURVEY) Ne : . SPE tt 1 SS 53 338 35 I BELO a Tr = rte ; = a \ oor \ 4, 40 so 7 YEARS ELAPSED BETWEEN FIRST ano SECOND SURVEYS 2 YEARS ELAPSED BETWEEN SECOND ano THIRD SURVEYS SCALE FEET 100 0 100 200 300 400 500 600 FEET 50 PROGRESSIVE UNDERWATER EROSION, RIVER THAMES LAND RECLAMATION Il In the lower reaches of the river, a deposit locally called ‘moor log” lies mostly about 4 feet below marsh level. It may be found about low-water level, when the outer toe of the river wall is scoured away or excavated. Moor log consists of small tree trunks, interspersed with brushwood, yew and willow forming a considerable proportion of the trees. These are strewn pell-mell horizontally, and are in diameter up to 14 or 16 inches. The stratum runs up to to feet in thickness, having often beneath it 12 to 15 inches of blue clay, and under this sand and gravel. At Deptford, it is stated to be 6 feet thick; in Woolwich Reach, 7 to 8 feet; and at Barking, 9 feet. It increases in thickness in passing down stream. From its appearance the origin of the deposit may be sur- mised. A dense woodland, consisting of small trees and undergrowth, must have clothed the estuary of that which is now the Thames valley—then a tract of swamp and eyot. This tract of land and water probably slowly subsided, or became submerged by inundation, and a hurricane or successive tem- pests subsequently uprooted and strewed the trees in a confused medley. The existence of remains of the Irish elk above the moor log seems to indicate that its formation may have been coeval with palzolithic man. Tidal Penetration.—The pressure of the diurnal tidal pulse penetrates wherever a vein of sand or pervious material exists abutting on a river, and this action sets up disintegration, and the consequent slipping of its banks. A notable instance of this action was seen in the settlement of St. Paul’s Cathedral, which is founded on beds of sand overlying brick earth (fig. 3). The river toe of these beds for a short frontage opposite the cathedral having been cut away, the influx and efflux of the tide started a sort of sand-glass action, and the effect of this was a serious disturbance of the equilibrium of the structure, until leakage was stanched by detrital accretion. Land Reclamation.—In the design of training works, one of the most important factors is to conserve the maximum effective tidal reserve capable of inducing scour on the ebb. Many examples exist of a short-sighted policy of land reclama- tion. The temptation to shut off areas of estuarial slob in 12 THE TIDAL COMPARTMENT OF A RIVER order to make land for agricultural or other purposes is some- times insistent. This practice has been the fruitful source of river deterioration, in some cases amounting almost to extinc- tion. From half-ebb onwards the scouring force of a stream is doing its best work. The greater the volume of effluent water impounded in reaches and by-channels, the stronger and longer will be such action. They constitute in effect a FORMATION BOTTOM OF FOUNDATIONS 7 7 — 30 —4 HIGHEST RANGE | OF TIDES 20 —- LEVEL OF SATURATION TWICE DAILY 10 — THAMES BALLAST ORONANCE |} OaTuUM 0 ISTANDING 2 = = WATERLEVEL (10 eae 5 LONDON CLAY za — FEET30 — Fig. 3-—Diagram of Subsoils, St. Paul's Cathedral natural reservoir, the water from which, under the force of gravitation as the tide falls, tends to throw into suspension and carry off superficial silt. The winning of tidal lands is, however, a perfectly legitimate and sound engineering under- taking, and, if carried out judiciously, innocuous so far as the maintenance of the river channel is concerned. Take the case of a river which zigzags, constantly shifting its route across alluvial flats. A big proportion of its waters will probably escape seawards uselessly, so far as the maintenance of the bed of the stream proper is concerned. Such waters wander across shoals, or fill depressions, and thus fail in the function ENTRANCE CHANNEL 13 of scour. The severance of swampy lands where such action occurs may cause little or no diminution of effective effluent scour. When tidal lift is small, and its action consequently only capable of traversing a short range of the lower reaches of a river, dredging must pretty generally be relied upon to keep down artificially the accretion of deposits. A free move- ment of tidal waters up the course of a river should be jealously conserved, as this condition is normally one of the most impor- tant factors in securing the maintenance of deep water for navigation. Under these conditions, the work of the dredger is in the main to attack the bar at the exit of the river into the sea, and to cut away hard shoals in the course of the stream. Entrance Channel.—If the section of the entrance channel is, owing to injudicious design, insufficient, the body of inflow- ing water is restricted, and the flood height of the river reduced, a condition tending to progressive and irregular shoaling. The goal to be attained is so to model the navigable channel that the maximum velocity and volume of tidal water may travel up the river bed to the extreme distance practicable. Captain Calver has laid it down as an axiom that the free access of tidal water is essential to a sea outlet and to keep down the tendency to bar formation, a result which the unaided flow of the stream cannot achieve. This generalization breaks down in the case of such rivers as the Amazon, from which a fresh-water stream is projected many miles into the Atlantic, the rise of tide being small. Broadly speaking, it is a sound rule to construct the entrance piers to a harbour parallel, projected an equal distance seawards, and bell-mouthed at the extremity. A study of the littoral conditions is essential to combat the accretion of drift. In many instances it is judicious to lay out entrance piers at such an angle that the prevailing columns of littoral drift striking the windward pier ricochet into deeper water. If entrance piers are not carried into deep water, and if a high and constantly recurring bar exists, it is permissible slightly to converge the entrance piers at their sea extremity, but so as to diminish the tidal flow as little as may be. If this is done judiciously, its effect may be to guide and augment the force of the ebb scour so as to check the formation of the most 14 THE TIDAL COMPARTMENT OF A RIVER troublesome portion of the bar. In a small harbour, it frequently hap- pens that a few feet of water more or less at low tide make all the dif- ference to its effectiveness in respect of the navigation to be catered for, and that after gales the bar, being heaped up as a narrow ridge, limits efficiency. By somewhat reinforcing the power of the ebb current, this tendency may often be successfully kept under. Thames Estuary Walls.—Fig. 4 represents a typical section of the river walling or clay embankments on the Essex shore of the Thames. There is difference of practice in detail, the relative thickness of the chalk and stone pitching varying. Some engineers carry the stone i pitching of the face to the crest of the wall, but commonly such walls are only pitched to 3 feet from the crest. Walls of this type protect many miles of marsh land from inun- dation. Along frontages of special exposure sheet piling is added at the toe of the sea slope. The em- bankment of the Thames through London has resulted in a quicker and stronger tidal force in the lower river. ‘ One curious feature in connec- tion with some of these walls is the fact that the clay of which they are composed appears to differ from that now to be dug in the vicinity. The Romans are believed to have commenced the reclamation of tidal lands in the estuary Fig. 4.—Essex Sea-wall WALL RIveER DATUM ORDNANCE RIVER TRAINING 15 of the Thames. In a recent discussion at the Institution of Civil Engineers’ the difficulty of arriving at a definition of the term ‘‘clay” and the ambiguity prevalent as to the angle of repose which may be safely assigned to it under varying physical conditions were emphasized. A few years ago a suggestion was put forward for the con- struction of a barrage in the vicinity of Gravesend. Happily the proposal was vetoed by the shipping authorities of the port. Apart from the beneficial effect on the health conditions of London of the scavenging action of the tide, apart also from the cheap form of propulsion for barge traffic a tideway affords, the creation of an impediment to the free and unrestricted move- ment of tidal forces would almost certainly have resulted in a disastrous transformation of the estuary, setting up shoals, deep pools, and causing an erratic and tortuous channel. Every great waterway enshrines a compromise. Trade requirements, the amenities and hygiene of the towns upon its banks, the maintenance of a section such that accretion is kept under with a minimum of expense—these are the main factors in the prob- lem. The function of the port authority of control is to hold the balance fairly between these often-conflicting elements. When a river runs abruptly into the sea with deep water close inshore, its regulation is a simpler problem than is the case when a wide and shifting estuary forms the connecting link between sea and river. In the latter case the primary con- sideration is usually to deepen artificially one outlet channel at the expense of subsidiary channels, so as to concentrate the action of effluent scour and force it to yield its best service. River Training.—On rivers serving an inland port or ports the desiderata are:— 1. Sectional areas progressively lessening in passing up- stream from the embouchure. 2. A river contour in which curves exist, alternately con- cave and convex, with straights tangential to the same. The contour should be laid out as regularly as possible, and the radii of curves should not exceed 3000 feet. 1 ‘The Lateral Pressure and Resistance of Clay and the Supporting Power of Clay Foun- dations” (A. L. Bell), Proc. Just. C. EB., Vol. CXCIX, pp. 233-336. 16 THE TIDAL COMPARTMENT OF A RIVER 3. An entrance so planned and such absence of obstruction in the channel that the tide level at the port is at least as high as that at the entrance. The questions of the velocity of the ebb current and the period of time of the tidal flow are, within limits, local in character, the great aim being to secure by regulated control such conditions that the shipping normally frequenting the river shall be navigated without let or hindrance, predetermined depths of waterway being automatically maintained. Granted an adequate backwater and maximum depths once secured, the ideal of a channel self-maintained by the scour of the ebb is the goal to be attained. Dredging is the usual mechanical expedient by which water- ways are improved or created. The advent of the modern suction dredger has transformed problems which baffled engi- neering science even thirty years ago. These machines are now constructed capable of lifting 10,000 tons of sand from a depth of 70 feet below low-water line in fifty minutes. Estimates of cost of dredging operations depend so largely on local con- ditions that the figures often current are delusive. It must be borne in mind that hopper measurements of spoil average about twice that of the material zm stu. A typical instance of waterways across sandy flats is that of the Dee from Chester to the sea. The present route of the Dee is in great degree artificial. The natural channel of the river anciently hugged the Cheshire shore of the estuary, following a serpentine course and having a depth of 6 feet and upwards. In 1732 an Act was obtained ostensibly for the improvement of the river. Under the powers so conferred a straight canal was cut from Chester to Connah’s Quay. At the same time extensive land reclamations on both sides of the stream were carried out. In all about 7000 acres were thus ‘‘inned”. The result was the decline of the river as a trade route. With the object of increasing its depth a series of jetties were subse- quently built, projecting at right angles from the Cheshire side, the Flintshire shore being mostly embanked. The effect of these jetties was to set up a swirling action at the extremity of each jetty or groyne. At such points deep pools were thus TAMPICO HARBOUR 17 created, and in the intermediate spaces shoaling took place. A weir has also been built below Chester, the level of the crest of which is 11 feet 6 inches above the level of the bed of the river. The engineering blunders perpetrated have had a disas- trous effect on what should have been a great artery of com- merce. There is no physical or geographical reason why the Dee should not carry as large a volume of trade as the Mersey; but to correct the errors of the past will involve heavy expendi- ture and works requiring a long period in execution. A strikingly successful dispersal of shoals in advance of a harbour occurred at Tampico, Mexico.1 At this spot the tidal movement is almost negligible, averaging 2 feet to 2 feet a - ——- a0uT 350° OF —- —— - —- ——- —— Fig. 5.—Cross-section of Training Wall, Tampico Harbour 6 inches. The river has at mean-flood stage a cross-section of about 25,000 square feet and a slope of about 7 inches in the mile. Owing to the drift of the Gulf Stream vast deposits of sand blocked the outlet of the river. A dredger was brought into play to loosen the bar, and jetties about 7000 feet in length and 950 feet apart were carried across the obstruction. The bar was of a stubborn character, and had numerous wrecks em- bedded in it. Depths of water before the works commenced were in places only a few feet. An opportune flood in July, 1893, continuing for twenty-two days, carried away the wrecks, and left a depth of 27 feet in its wake within and without the harbour entrance. The velocity of the flood was 8.2 miles per hour, and the total amount of material it carried into the Gulf of Mexico and dispersed was nearly 9,000,000 cubic yards. The maximum section of the jetty constructed on the windward side of the channel is shown in fig. 5. 1 “The Tampico Harbour Works, Mexico” (Dr. E. L. Corthell), Proc. /zst. C. £., Vol. CXXV, pp. 243-81. (0924) 3 18 THE TIDAL COMPARTMENT OF A RIVER The training of the mouth of the Mississippi affords a notable In this case two parallel jetties example of a similar character. FLOOD LEVEL RIVER SIDE OF | , -— AVERAGE 25:0 — BOTTOM 3 AVERAGE 45-0” sen Fig. 6.—Cross-section of Training Wall, River Mississippi TITS et es GULF SIDE were run seawards a distance of 24 miles. The effective width of the channel through the jetties was about 700 feet. In this instance willow mattresses and fascines on the Dutch system were adopted. These were par- tially loaded with stone, and, where the sea exposure is heaviest, with concrete blocks weighing from 20 to zo tons. The depth of water in the entrance is now about 30 feet. A section of the fascine wall so constructed is shown in fig. 6. Estuarial sand-bars, when dispersed, are apt to recur. They consist in section of under-water peaks, some- times rising steeply to great heights above the sea bed. Although the tidal ebb and flow passes across them at high-current velocities, they often maintain an inclination steeper than the angle of repose of the sand compos- ing them. When a gale of exceptional violence disturbs or partially levels them, with the recurrence of normal weather conditions they will pile up afresh in remarkably short intervals of time. The problem of keeping down a harbour bar, unless expendi- UPLAND AND TIDAL WATERS 19 ture on an ample scale is forthcoming, is one of the most troublesome in the engineering of sea works. This is especially the case in small harbours, the tidal compartments of the rivers behind which are perhaps studded with obstructions to tidal flow. Such harbours are usually slowly evolved, and depend on annual revenue for improvement, a condition under which hand-to-mouth methods of finance are imperative. The Firth of Forth affords an instance of a barless waterway, a condition due (1) to the gradual contraction of the inlet from the sea landwards, (2) its land shelter, (3) a conformation such that heavy seas cannot plough up the bed of its channel. On the East Anglian coast a notable contrast exists between the harbours of Yarmouth and Lowestoft, only a few miles apart. At the former harbour the outlet and approaches are deep by reason of the fact that the Yare and its tributaries bring down a great volume of land backwater and afford vast areas for the tidal flow to fill. At Lowestoft comparatively little tidal water enters the harbour, with the result that heavy dredging has to be resorted to to keep even the shifting and dangerous approaches to the port in being. Upland and Tidal Waters.—The question of the relative value of land waters and tidal ebb and flow in producing stability and equilibrium in the ~égzme of a river has been much discussed. The outlet of a river is the proper section to be first attacked in carrying out a system of regulation, and every step taken should be part of a comprehensive scheme of operations. The entrance of a river may consist of:— 1. Piers running into the sea, generally barred or impeded with shoal water. 2. A natural channel debouching directly into the sea. 3. The same cutting its way through flats of sand and mud. 4. An estuary. Estuarial conditions may exist in combination with either of the others. Entrance piers may be either solid constructions of timber or concrete, forming walls approximating to the vertical; or skele- ton structures, the lower tiers of which are carried up solid to a 20 THE TIDAL COMPARTMENT OF A RIVER few feet above low water. Piers projected across shingle or sandy foreshores constitute in effect groynes arresting the littoral movement of drift. As such, unless designed with skill, they are apt to set up irregular shoaling and bars out- side the harbour mouth. The contours of the bars which form in advance of them are in plan mostly sickle- or horseshoe- shaped. The relative lengths and overlapping of entrance piers are matters which have frequently made or marred a harbour design. Thus at Durban harbour, South Africa,! the governing authority overruled the judgment of the engineers as to the design of the entrance piers, and, for a period of nearly sixty years, the harbour was of inadequate depth and one of the most uneasy on the South African littoral. This was mainly by reason of the fact that the south pier, as built and extended, persistently overlapped the north pier. Ultimately piers of equal length were adopted. The economy of the drift was thus changed, and the harbour now shows progressive deepening and commercial value. In some instances a leeward pier has been so laid out as to act as a sand trap, thus threatening with extinction the harbour it was built to serve. The ratio between the necessary tidal volume of water enter- ing a harbour and the sectional area below low water of its entrance, in order to attain and maintain a given working depth of water, is variable. It appears that at Durban 1400 cubic yards of tidal volume per square foot of section of low- water channel sufficed to maintain or slightly increase depths of 33 feet and upwards, whereas, at the entrance channel of Cork harbour, 1050 cubic yards per foot of section secured complete scouring effect up to depths of 60 feet. Flushing reservoirs have been devised in many localities, but their effects are apt to be capricious and irregular. The sudden release of a large volume of effluent water under a con- siderable head will dig deep pits in the vicinity of the reservoir and redeposit the scoured material in ridges or shoals, unless 1 “Durban Harbour, South Africa” (C. W. Methven), Proc, /nst. C. E., Vol. CXCIII, pp. 1-122, RIVER THAMES 21 the works are designed with much care. Experiments made with pneumatic erosion point to that expedient as a probable means of disturbing and throwing into suspension troublesome shoals, so that the force of the ebb may be enabled to carry them seawards. Mechanical erosion on the same principle has been applied successfully. When remodelling the route of a tortuous river one matter of importance to be studied is the variation of geological for- mation along its course. In laying out channel curves full advantage should be taken of the comparative resistances of the strata to the impact of flow of tidal water. Broad principles only can be predicated in relation to the design of such schemes, as each problem has to be evolved on its individual merits. The motion of flowing water under the force of gravitation follows a rotative path, and its particles ricochet on meeting an obstruction. The resultant of these combined motions in the deeper areas of a stream is a downward, boring action tending to erode soft soil and redeposit it in slacker water. The dynamic force of a stream is particularly active on its concave surfaces by reason of the transverse swirling action set up as it swings round a bend. The water gradient thus created results in a raking effect across the bed of the river, producing a deepening of the inner area of concavity and a shoaling on its outer area on or near the opposite shore. Plate II shows the cross-section of the Thames in a straight run at Long Reach. It will be noted that on both shores the batter of the river banks is coincident and the river bed fairly uniform in depth. Plate II also shows a section of the river through St. Clement’s Reach, Greenhithe. The currents on the concave (Essex) shore have in this section produced a steep gradient and excavated the river bed to great depths. On the Kentish (convex) shore the gradient of the river bank is rela- tively flat and the river bed shoal. The navigation channel, or thalweg, for large vessels round such bends naturally follows the deeper water or the track of concavity. If the river section shown in this plate had been unduly contracted at the bend its lack of symmetry would have been relatively increased both on its shoal and scoured sides. 22 THE TIDAL COMPARTMENT OF A RIVER The welling up of the water caused by this action may be quite considerable. In the proximity of the entrance of the Alexandra Dock, Hull, the water-level at spring tides is about 19 inches higher than that of the opposite shore, two miles away. The transverse raking effect thus set up in the bed of a stream does not, however, appear to affect materially the flow of the main body of the river. Owing to the character of its alluvial deposits the Thames, below London, has been moulded into an admirable carrier of world trade by reason both of its natural economy and of the prevision of its authorities of control. With the growth of the size of merchant ships the problem of the classification of their traffic has become more serious. It is probable that the tendency to cater by means of deep- water quays for vessels of extreme draught at points near the mouth of rivers, where greater depths of water naturally exist, reserving up-river accommodation for ships of less draught, will be accentuated. Trade will inevitably follow geographical conditions. River Velocities.—Observations have been made by many investigators with the object of defining by formula the laws of stream velocity at varying depths of a channel and also the retardation of velocity due to obstructions in its course. The formule thus evolved are to be found in many handbooks. In any serious problem of river regulation exhaustive current observations are essential. The volume of discharge of a waterway is obtained by multiplying its cross-sectional area by its mean velocity. To ascertain mean velocity observations by current meter or the velocity rod may be taken. Inference from surface velocity is more often resorted to. Owing to the varying rugosity of the bed of a stream, the above expedients furnish, however, an approximation only. It is obvious that the shape of the channel and the obstruction of weeds and other under-water impediments are varying factors which affect the issue. The problem can, nevertheless, be worked out with sufficient close- ness for practical purposes by observation and the assistance of the published hydraulic tables. Plate II east O FEES. CROSS SECTION OF R.THAMES at LONG REACH FEET 109) «0. 100 300. soo 1000 1500 2100 FEET. ker 4} } fp ft jo} J} pf 4 Vv wv Ss & rs : e 20 FEET. Ww ‘ <€ fs J al bea o. S. ‘7. N q 10. 2 y = Ss 5 i O. FEET _B : ORDNANCE DATUM, - 5. . : oO. , - 19, KENT. E ss ex. ‘is 2 (CONVEX BANK.) (CONCAVE BANK) 25 \ 30. - 35. ao. i 4s 50 FEET ‘ CROSS SECTION oF RIVER THAMES «t ST CLEMENTS REACH ¢ 2000. 2500 3000, 3500. 4000. 4500 FEET. TIDAL BORE 23 The following formule may be quoted:— V = Velocity of water at surface in inches per second. Velocity at bottom = (V + 1) — 2,/V. Mean velocity = (V+o0.5) —./V. = 0.8 V in sluggish rivers. In rivers heavily charged with detritus the velocity is less than in clear streams. Broadly speaking, in a normal stream say of 15 feet depth the bottom velocity will be about one-half that of the surface. Observations on the Elbe, the Danube, and the Parana showed the bottom velocities to be 85 per cent of those of the surface. Tidal Bore.—This phenomenon occurs in many localities in which tidal flow passes into a shallow or contracted channel. The conditions most favourable are a swift river, sand flats in- tersected by the river in advance of the same, outside a funnel- shaped estuary. Under such conditions a wave or wall of travelling water advances at high velocity up-stream. The in- rushing tidal water is skidded in passing the obstruction set up by the bottom of the stream or is checked by the impetus of the undertow of the outflowing land water, with the result that it wells up and travels as a roller inland. In embayments, such as those of St. Malo and Fundy, the tidal impulse is crowded into horn-shaped recessions of the coast-line. The waters cannot escape laterally, and are forced to pile themselves up, with the result that they bring about abnormal tidal range. At Granville the tidal lift is 37 feet; in the Bay of Fundy it is sometimes 60 feet, and the tidal current there runs at 1o miles an hour. The rise at Chepstow from the Bristol Channel at springs is 38 feet. The bore in the Severn runs as a column of water 5 or 6 feet high along the banks and 34 feet in the centre of the river. In the Seine at Tancarville there was formerly a bore in height 10 feet, in velocity 12 miles per hour. The training of the river has, however, greatly reduced this. Wherever, by deepening or other modification of channel section, the tidal flow meets a lesser obstruction in travelling up-stream, bore effects tend to 24 THE TIDAL COMPARTMENT OF A RIVER abate or disappear. On the river Tsien-tang-Kiang' bore effects exist in an unexampled degree. As the flood travels across the sand there is a difference of level of 19 feet at springs between the water on the outside of the bar and that in the mouth of the river, a distance of about 20 miles. The measured speed of this flood having a gradient of about one foot per mile is 14.6 miles per hour. The bore has a breadth of 1800 yards, and forms a cascade 8 to 12 feet high. It strikes the outlet of the river at an angle of 40 to 70 degrees, and its roar is audible 14 or 15 miles away, an hour and twenty minutes before arriv- ing. The bore maintains its breadth, height, speed, and regular appearance for 12 to 15 miles above the mouth of the river. At the city of Hang-chau, 24 miles from the mouth, the tidal range drops from 194 feet to 6 feet. The ancient devices of the Chinese to protect the native river boats from the effects of the bore have been adopted for the last eight or nine hundred years and still persist. The river is embanked for a distance of about 30 miles, and the top of the sea-wall is 3 to 9 feet above high-water spring tides. The em- bankment is faced with stone, and at numerous places by the river-side stone platforms enclosed by piles are constructed. One such platform is 1100 yards long and 20 feet wide. At both ends of these platforms buttresses are constructed parallel to the river wall. The bore as it travels along the banks is deflected by these buttresses into the middle of the river, and the junk master is thus enabled to take shelter from the destruc- tive force of the tidal wave. Within the shield of a platform his junk slides harmlessly up and down the face of the slope of the embankment. Working Models.—Within the last thirty years the practice of experimenting with working models of a tidal estuary before laying out new works for regulating it, has been initiated. Professor Osborne Reynolds’s paper before the British Associa- tion in 1887 first called attention to the utility of this procedure. The British Association in 1889 appointed a committee to inves- tigate, by means of working models, the action of waves and 1«The Bore of the Tsien-tang-Kiang’ (Commander W. U. Moore, R.N.), Proc. Inst. C. £., Vol. XCIX, pp. 297-304. WORKING MODELS 25 currents on the beds and foreshores of estuaries. The late L. F. Vernon-Harcourt adopted this expedient when studying the problem of training walls for the sea outlet of the River Seine, and in 1889 communicated the results of his investigations to the Royal Society... The French Government subsequently had a model constructed under the advice of M. Mengin, the engineer in charge. Experience of tests made with such models has shown their use to be highly valuable. Notwithstanding the fact that the vertical and horizontal scales employed for making such models are necessarily different, the records so obtained afford a close insight into the prospective effects of a defined scheme of works. In a model of the Mersey the horizontal scale adopted was 2 inches to the mile, the vertical scale 80 feet to the inch. The tide period was 42 seconds. After running the model for a period of 2000 tides, the existing natural contours and channels of the river were found to be reproduced with remarkable fidelity. By working a model for a few hours, and simulating repeated tidal effect, data can be demonstrated which would involve long periods of costly observation. While exceptional gales cause temporary derangement of estuarial conditions, the regular movements of the forces of Nature bring such conditions back to the normal, and the play of this action can be watched by operating a model. The reports above specified describe how such models can be constructed. It is probable that no scheme of operations for the regulation of estuaries or tidal flats involving large outlay will in the future be organized without supplementing the pre- liminary investigations on the site by the evidence of working models. 1 “The Principle of Training Rivers through Tidal Estuaries, as illustrated by Investi- gations into the Methods of Improving the Navigation Channels of the Estuary of the Seine” (L. F. Vernon-Harcourt), Proc. Royal Society, 1889. CHAPTER III The Foreshore According to the Office of Woods the United Kingdom possesses a total frontage of coast foreshore at high-water line of 7906 miles; the total area between high-water and low-water mark is 619,999 acres. On the same authority the total length of river frontage at high-water line is 11,081 miles; the acreage between high-water and low-water mark of rivers is 175,722 acres. The Director-General of Ordnance Survey (Colonel R. C. Hellard, R.E.) stated in evidence before the Coast Erosion Commission that in thirty-three years (between 1863 and 1896), so far as the official surveys enabled him to ascertain, there had been in England an accretion of land of 35,444 acres, an erosion of 4692 acres, or a net gain of about 30,750 acres of rateable land. A definition of the term ‘coast foreshore” is not easy. It is synonymous with the word ‘‘seashore”. In legal documents the /zt¢us mars is defined as ‘‘ that ground between the ordinary high-water and low-water mark”. Otherwise stated, the shore ‘is confined to the flux and reflux of the sea at ordinary tides”. The ambiguity of the above definitions has been the cause of endless litigation. It is obvious that the term ‘ordinary tides” is capable of several definitions. The highest equinoctial spring tides occur in the natural order of things, and are in this sense “ordinary”. From the evidence of the Director-General, it would appear that there has been a lack of continuity of method in the mapping of the coast-line of Great Britain below high-water level. After the legal limits of the foreshore were defined by 26 ‘““FORESHORE” 27 Court decision as those ‘‘ between high- and low-water marks of ordinary tides”, the basis of survey appears to have been modified. The Director-General points out that although in a given locality high-water line might remain constant the simultaneous position of low-water line might fluctuate, causing, as the case might be, a steepening or flattening of the gradient of the shore, which in its turn would affect its area. In estimat- ing the aggregate gain or loss due to accretion and erosion the question of the inclusion or exclusion of the foreshore consti- tutes an important and precarious factor, as, if the foreshore be excluded and the area of terra firma only be considered, obviously this element of uncertainty would be to a large extent eliminated. The Ordnance Survey authorities were in fact faced with the primitive dilemma as to what constitutes land and what water. Moreover, in many instances land re- clamation was carried out, increasing the area of the soil of Great Britain by artificial means. Mean sea-level is the most reliable datum in respect of plotting the contours of tidal range, and on Ordnance maps it is stated that the altitudes are given in feet above the assumed mean level of the sea at Liverpool, which is 0.650 feet below the general mean level of the sea. Apparently until 1913 mean sea-level was not ascertained with accuracy. It would appear, therefore, to be legitimate to take the official statements with regard to the estimated increase in land area of the kingdom with considerable qualification. The recommendation of the Commission under this head is as follows :— “It would be of advantage if the Ordnance and Geological Surveys could take steps to ascertain from time to time whether, and, if so, to what extent, changes in the relative levels of land and sea are taking place”. Arising out of a recent case, a paper read before the Law Society’ is of interest. It may perhaps be noted that the Ordnance Survey Department relies upon the case of Attorney- General v. Chambers for a definition of the term ‘‘ foreshore”. In this case the coastal area overflowed by the average of 1 “The Foreshore" (J. W. F. Jacques), Law Society's Birmingham Meeting, 1908. (Spottis- woode & Co.) 28 THE FORESHORE medium tides in each quarter of the lunar revolution during the year was assumed to delimit the rights of the Crown on the seashore. In the specific case above referred to (‘‘ Pierson v. Burnham, U.D.C.”), the Board of Trade had granted in 1897 a lease of ‘‘the foreshore” to the Burnham (Somerset) U.D.C., using the Ordnance Survey map as indicating its boundary. The Ordnance Survey Department had revised their map in 1897, and again in 1902. The case turned upon the right of the contiguous owner to fence his land, which was above the flood- ing limit of all save extraordinary spring tides. In answer to inquiry by the plaintiff's solicitor, the Director-General of Ordnance Surveys stated that, in the preparation of Ordnance maps, tide lines were not referred to any datum, but were re- presented by the contour of mean tidal flow between springs and neaps. In reply to subsequent inquiry he stated that high-water contours were obtained by actual survey taken at the fourth tide before new and full moon. It further appeared that, as must obviously have been the case, the Ordnance sur- veyors actually took their observations on a ‘‘selected tide”. Now unless wind conditions are absolutely still when such survey is undertaken, it is obvious that the range of the tide might be materially raised or depressed from this cause. Again, the summit flow of tidal travel is so transient that its exact definition by survey would be wellnigh impossible. From the above considerations it appeared to those engaged in the case that the only practicable method of delimiting tidal flow was that of survey plus calculation. The perpendicular height of the ‘‘medium tide” having been taken from the nearest observation point given in the Admiralty tide-tables of the year, and the necessary correction made for its variation, as ascertained by survey, for the point actually under obser- vation, the contour line on the foreshore would by this method be ascertained by levelling from the Ordnance bench marks. Thus would contour lines indicating high-water level be accu- rately defined on a plan, and such contours would be based upon the known data of tidal gauges, disregarding the pre- carious observations of a fleeting line of tideway. CASES 29 The difficulty of giving verbal expression to the delimitation of foreshore rights is doubtless considerable, for definition is ever an ill-fitting garment. The first consideration of litigants may pretty frequently be expressed in the following question: To what extent can we with legal security remove our neigh- bour’s landmark? The ownership of lands contiguous to a shifting foreshore has been the cause of many legal decisions, for the law in Great Britain in this connection appears to rest largely on custom. In the case of Scratton v. Brown, it was held that the frontier of a freehold held under grants from the Crown advances or recedes with the corresponding accretion or erosion of the foreshore. In the case of Rex v. Lord Yarborough, it was decided that ‘‘accretion, if gradual, belongs to the owner of the adjoining property”. In the case of Lowe v. Govett, the decision was: ‘‘A piece of land covered with land and sea weed, and overflowed by extraordinary spring tides, but not by the mean ordinary tides, belongs to the adjoining owner, and that without the exercise of any acts of ownership”. Grounds upon which claim to ownership has been founded are numerous, but the legal issue in this respect is somewhat wide of the present discussion. The latest decision would appear to be summed thus, in the case Attorney-General v. Emerson: ‘A subject can only establish a title to any part of the fore- shore, either by proving an express grant thereof from the Crown, or by giving evidence from which such a grant, though not capable of being produced, can be presumed”. The rights of the public to wander at will over the sea beach, and to use the foreshore for walking, riding, driving, drying nets, hauling up boats, bathing, and sport, have given rise to much litigation. In the case quoted above (Pierson v. Burn- ham, U.D.C.), it was held that to assume the rights of the public over a shore to be similar to those over a highway dedicated to public use was unreasonable and untenable; that because an owner of waste land adjoining a foreshore and oc- casionally overflowed allowed the public to wander at will over the same, he thereby created no public right. If it were at- tempted to establish such a right, the only result would be that 30 THE FORESHORE owners of littoral lands would be compelled to fence them, in order to avoid establishing inconvenient rights. Such admission would be distinctly to the detriment of the public, as, if con- ceded, lands capable of being developed into the sea front of a prospective watering-place would be jealously fended from the incursion of the public. The state of the law in respect of the ownership of seaside lands in foreign countries may be briefly summarized as follows :1— France.—Foreshore lands covered at high water form part of the Domaine Public National, and are administered by the Département des Travaux Publics. The State stands aloof from responsibility in respect of erosion, except that where owners form Associations Syndicales de Défense the State sometimes grants subventions. The landowners have no right to remove sand or shingle except with the authority of the Préfet or Ministre des Travaux Publics, the price for same being fixed by the Domaines de l’Etat. If the sea recedes, such recession becomes the property of the State; if the sea encroaches, the landowner receives no indemnity from the State. Belgium.—The ownership of the foreshore is vested as in France. The definition of the phrase “foreshore” given by the Ordonnance de la Marine of 1681, is that area covered and uncovered at new and full moons by the greatest flood in the month of March. The limit actually adopted to-day is the line assumed by the tidal curve on the coast 5.21 metres above zero, Ostend, which mark corresponds with the average level of low- water spring tides. From the tidal curve thus indicated is defined the dividing line between private property and that under the control of the Domaine Public. Thus it will be noted that the practice adopted by the State Departments of Belgium accords with the method evolved by those engaged in the Burnham case, cited above, as the only plan of delimitation consistent with accuracy. The State in Belgium assumes no responsibility in respect of protection of the coast-line or the effects of erosion. The rights of littoral owners do not extend beyond the boundaries defined above, and foreshore lands 1 “Coast Erosion” (A. E. Carey), Proc. /nst. C. Z., Vol. CLIX, pp. 1-103. LEGAL STATUS 31 formed by the insensible recession of the sea become the property of the State, unless there is some title or prescrip- tive right to the contrary—i.e. unless these lands are possessed by virtue of an act of acquisition or by thirty years’ occu- pation. Italy.—Under the Civil Code, ports, harbours, foreshores, and waterways in connection with same, are the property of the Crown. This principle is based upon that of Roman law, whereby property essential to public utility cannot become the exclusive property of anyone, but is vested in the State. Owing to the difference between tidal conditions in the Mediterranean and the Ocean, the period for the observation of delimitation between private and public ownership in the former case is that of winter, when tidal range is at its maximum. The foreshore comes under the jurisdiction of the Minister of Finance, its use and control under the Minister of Marine, and all works affecting it must be sanctioned by the Minister of Public Works. Sand and shingle can only be removed with official consent. In the event of either recession or erosion of a coast-line, the trans- formed foreshore becomes Crown property. A landowner whose land is washed away has no redress against the State, unless such encroachment is due to dredging or the removal of pro- tective embankments, when those responsible for the damage would be legally liable. Denmark.—Foreshores are private property: their control is in the hands of adjoining landowners. Norway.—The Danish rule holds good, private rights ex- tending, moreover, to a depth 2 metres below low water. United States.—In the United States the legal status of the foreshore is subject to the varying law of particular States. In the States of Maine, New Hampshire, and Massachusetts the law provides that private ownership on the foreshore extends to low-water mark, where the sea does not ebb more than Ioo rods, but not beyond this limit, subject, however, to the rights of navigation. Littoral proprietors may thus exclude navigation from their own flats by building wharves or other structures to low-water mark, and it has been held that they may fill up their frontage, and thus prevent the ebb and flow of the tide, without 32 THE FORESHORE being liable in damages. In Connecticut the rights and privi- leges of littoral proprietors extend to low-water mark, subject to State regulation. In New York the landowner has no right of property between high-water and low-water mark. He has no right to reclaim, as against the State, and is not entitled to compensation should a railway be constructed along the water- front of his premises. In New Jersey the State owns the shore, and the littoral proprietors have no legal right to carry out works upon it. The State may groyne any portion of the shore without making compensation to the owners of the adjacent lands, but when shore lands are reclaimed they become the pro- perty of the littoral proprietor, and cannot be taken for public usage or granted by the State to other persons without com- pensation. In Virginia the littoral owner possesses exclusive rights and privileges to low-water mark, and, if not interfering with navigation, may build wharves below low-water mark. In North Carolina the State can only grant land under navi- gable water for wharf purposes, but for this purpose the littoral owner may carry his works ‘‘as far as deep water”, and they then become his absolute property. In South Carolina the State owns the land under navigable waters by common law. In Florida the shore is vested by statute in the littoral owners. In Louisiana strips of land near the mouth of the Mississippi, including land not submerged but subject to overflow, belong to the State. In California private ownership extends to high-water mark, the shore being the property of the State; and in Oregon similar rights exist to those in the State of Florida. Turning aside from legal subtleties, the foreshore constitutes to the engineer a terrain generally covered by a travelling medium of defence, consisting of sand, shingle, or both. In its rear may be sea-walls, cliffs, or embankments. From the slope of the sea marge, and the nature of the material with which it is clothed, the degree of its storm exposure may be safely surmised. If the shore be flat, consisting of wide stretches of muddy sand, with or without a narrow fringe of shingle or stone along its landward frontage, it is safe to infer the absence of severe gale conditions. If, on the other hand, a foreshore con- GLACIAL DRIFT 33 sists of steep ridges of shingle or boulders, intermixed with little or no sand, such economy points to its being subject to periodical wave-battering. One of the first matters to be studied in gauging a coast-line régime is its geological economy. Obviously, the existence of primary or igneous rocks spells resistance to erosive forces; the presence of clay or friable sandstone means that under- mining by or invasion of the sea can only be counteracted by artificial expedient. The presence of vast accumulations of sand and shingle, forming a buffer territory between land and water, is a phe- nomenon which requires some comment. The explanation of its existence usually offered is that it represents the degradation of contiguous land; that as cliffs fall, or fresh tracts of coast- line are attacked by encroachment of the sea, the flint and stone they contain are riddled out, and thus is amassed a capital of protective medium of defence. Attrition, due to wind-waves, then breaks down boulders into shingle, and shingle into sand. This explanation is, however, only half the story. The fall of chalk cliffs is intermittent, and the amount of flint derived from this source would be relatively insignificant. East of Folkestone the white chalk dies out, and the grey chalk running towards Dover is flintless. The only solution of the problem which fits the facts is that in our south-east coast shingle deposits we have the débris of the denudation of Tertiary gravels and sands, which overlay the chalk before the floods succeeding the Glacial epochs scoured and moulded the surface of the chalk. It is probable that the crest of the dome of deposit reached a height of 2000 feet above present sea-level, when the North and South Downs formed one continuous sheet of chalk, covered by gravel deposits. On other portions of the coast-line (notably the east coast), the shingle deposits have in the main been derived from Glacial Drift, which assumed vast proportions in the late Glacial Period. The result of these remote geological events has been that our coast-line is fendered by a belt of protecting medium. It is obvious that this medium, which is kept in circulation by natural forces, constitutes in effect a bank in which our capital (09%) 4 34 THE FORESHORE of safety is lodged, and that its serious depletion amounts to an act of criminal folly, which the State should intervene to prevent. The depth at which mud reposes on a sea bed is good evidence as an index of the severity of wave conditions. Airy has shown by calculation that heavy ground-swell scours the sea bed at a depth of 100 fathoms. Lobster pots on the Devon- shire coast become filled with sand at a depth of 30 fathoms. Off the west coast of Ireland mud comes to rest in 40 to 60 fathoms water. In the sheltered parts of the east coast loughs it lies at depths of 5 fathoms. A wave trap or spending beach is indispensable to the tranquillity of an enclosed harbour or landlocked basin, espe- cially where tidal range is considerable. The run of the sea, after passing the entrance piers of a harbour, assumes the aspect of a miniature bore. Its impetus is cumulative. When the wave thus developed reaches a shelving heach, or a recess leading to slob land, its force is dissipated. If a harbour be so designed that the run entering it encounters a wall or other barrier approximating to the vertical, the recoil of the oncoming wave induces prolonged oscillation. It has been proved ex- perimentally, that in a box 20 feet long, 4-inch to 4-inch waves beat backwards and forwards at least sixty times. Such action causes the accumulation of a transverse ridge or bar running centrally across the middle of the area of disturbance, at right angles to the line of the run of the waves. A notable instance of this effect is that of the harbour at Torquay (fig. 7). The small inner harbour is of ancient con- struction, and sufficed for the minor traffic of the district. In order to enclose a larger area of water, the western arm was subsequently built. The opening of the new harbour faces west- south-west. Concurrently a reclamation of foreshore land was carried out, a nearly vertical wall being substituted for the old sloping sea marge, which previously constituted an efficient wave-breaker. The result of these works has been that both the inner and outer harbours have for practical purposes been gutted, as the mud and sand which formerly lay in the harbour have been scoured away and carried to sea. Between the nearly SEA WORK 35 vertical faces of the western arm and of the new alignment of foreshore, any undulations which pass into the harbour are repeatedly reflected. The result is an uneasy harbour under normal conditions, and in gales, a condition of things such that the harbour is almost unsafe for the small craft frequenting it. It is probable that quite a moderate expenditure, repro- ducing conditions which make for tranquillity, would be effective. The charm of sea work consists largely in the fact of its Fig. 7.—Diagram of Torquay Harbour infinite variety. Its merit is that it cannot be standardized. No two stretches of coast-line are alike. Each novel set of conditions has to be absorbed into the inner consciousness of the engineer who would successfully evolve a scheme of arti- ficial control. It is the interaction of the forces and the apparent caprice of sea action that puzzle him. The man to whom the pitfalls of such a problem have grown instinctive in some measure recovers the primary faculty which civilization is apt to blunt. Unconsciously, he sets to work to weave a chain of cause and effect by which storm and current may be brought into subjection to his purpose. There are two schools of foreshore engineers. One school seeks to establish as an axiom the theory that the travel of 36 THE FORESHORE littoral drift is due to tidal action, the other that it is caused by wave action. The march of the circulating medium of defence is, in fact, represented by the sum of all the forces operating on a coast-line. Wind-waves are the prime cause. The tidal impulse plays its part. Wind creates great sand-storms, pro- ducing vast deposits above high-water line, and the recoil from a cliff or sea-wall of heavy swell scours and drags down shingle, bringing it within reach of the oblique stroke of running seas. That the tidal force is not the sole or principal operative action in the travel of drift is evidenced by the fact that on coast-lines where tidal lift is negligible the same familiar phenomena are to be met with. The column of drift oscillates coastwise, and on the recession of the tide is left alternately heaped into terraces and dragged down into slopes. The prevailing wind in Northern Europe is west-south-west. Taking an exposed coast-line, such as that fronting the English Channel, running roughly east and west, _ the effect of wind-waves varies greatly. An off-shore wind causes the beach material to heap up, a due on-shore wind sweeps it down. Between these two extremes the variations of angle of stroke cause all the familiar gradations of phenomena. Where the trend of a coast affords protection from sea exposure and the worst conditions of wind, the severity of the problem of erosion is lessened. Thus under the lee of an outstanding headland, such as the Start, the shore can be maintained with comparatively little difficulty. It is beyond the zone of such protection that the full rigour of erosion results. For instance, between the Start and Sidmouth the inroads of the sea are less acute than is the case on the frontage to the east, by reason of the fact that the former strip of foreshore is partially sheltered. / Oceanic waves advance in columns from the open sea. As they approach the shore their diagram of forces changes. From waves of oscillation they become waves of translation. A wave of oscillation is a mere carrier of momentum. The impetus it has acquired sets up a vertical spinning action. Its motion is the resultant of the horizontal force of the wind and the vertical force of gravitation. The contour of a deep-sea wave BEACH TRAVEL 37 is cycloidal, and this approximates to an ellipse in approach- ing shoal water. The force conveyed in an oscillatory wave revolves in a circular movement at the crest. As may be readily observed, an object floating on an oscillatory wave is not im- pelled forward by that wave—it drifts with the current. From the point when the wave becomes translatory in form its whole mass travels onward in the manner of a flowing stream. When its height attains one-third of its length the wave breaks. The translatory waves that affect a foreshore plough up the beach constituents, and the problem of defence works is to hold the shingle and sand up to their work, so that the shore shall not be denuded of its natural protection. Obviously the shape of the shore in section is a factor of first-rate importance. The normal forces of attack and the contours of a sea marge are complementary. If a shore be neglected its contour changes, its gradient grows dangerously steep, and the coast-line suffers erosion. The mechanical action of the off-shore wind in heaping up a foreshore is somewhat obscure. Presumably by checking the onrush of the crest it upsets the equilibrium of the wave. The motion of the crest being retarded, the base of the wave sets up an undertowing action. The beach materials are thus pushed up the under-water slope, and, the scouring action of the crest being absent, they accumulate. It must be borne in mind that the flood tide is both longer and stronger than the ebb, and therefore that, so far as the action of the tidal current is effective, it operates by driving the beach constituents in the direction of the flood. Wave action, when oblique to the shore, causes a series of unsymmetrical impulses. The impinging wave drives a column of shingle up the slope of the foreshore, the impelling force becomes exhausted, and the water escapes through the beach. The recoil of the spent water follows the most direct line of travel, i.e. that at right angles to the coast-line. It has pushed a certain quantity of beach material beyond the power of the recoil and dragged the balance down again, and thus the march of that material follows a zigzag, saw-tooth line of travel. The operative wind- waves in the English Channel are those produced by the 38 THE FORESHORE impulsion of the winds from west to south-west. In the North Sea, owing to the land shelter from the west, winds round about the north-east are those setting up the severest wind- waves. Land springs frequently disintegrate the base of a cliff or disturb a foreshore to such a degree that the recurrent effect of gales is increased. Wherever cliffs of Tertiary clay abut on a foreshore their plasticity is a constant source of danger. They are apt to slide in the fashion of a glacier, and the pressures they cause can only be counteracted by heavy works. Another action seldom allowed for is that set up where sea-walls or other littoral defences are built at or near the foot of a cliff. The weight of the cliff then causes the strata on which it is based to buckle, and the foundations of the sea-wall may thus be crushed out of line and the wall ruptured. Another action which is certainly not negligible is the effect of the concussion of waves on the crust of the earth. The record of seismic disturbance is a registration of the ripple of oscillation conveyed by this action to a spot perhaps on the opposite side of the globe. Professor Milne’s instruments proved that rela- tively trifling displacements of weight cause an appreciable tilting of the earth’s crust, and Sir George Darwin calculated that the movement of the tide, the addition and subtraction of the weight of its waters, set up oscillatory disturbance inland for a distance of 100 miles. In the planning of a seaside town these considerations are important. At some of the older watering-places the building area is pushed forward to within a few yards of high-water line. The wise course is to leave a wide belt of lawns or gardens between the sea beach and the houses; thus can long flat slopes be substituted for high sea-walls. A line of such walling is one of the best expedients conceivable for producing dangerous scour, and perforce it has to be supplemented by heavy groyning. The art of Dutch foreshore engineers relies on the methods which are the antithesis of such expedients. In that country of nicely adjusted equilibrium between land and sea Nature CHESIL BANK 39 is copied with fidelity, and easy slopes on which sea forces may spend themselves are universally substituted for the mere dead weight of upright walls, against which the momentum of waves may be absorbed by shattering blows. The phenomenon of vast accumulations of shingle heaped to abnormal heights above high water by periodic gales requires some comment. In this connection a study of the geological antecedents of the coast-line under consideration is important. On the east coast what are termed ‘‘swashways” occur opposite lines of cliff. These consist of ridges of shingle and sand run- ning parallel to the coast-line, distant some few hundred yards from it, with a waterway between such shingle bank and the shore. The cause of this, which is a fleeting effect, is the beat- ing of ground-swell broadside on the coast-line. When such ground-swell ceases a swashway disappears. By direct impinge- ment the breakers drag down the shingle and form a tempor- ary ridge seawards. Formations such as the Chesil Bank fall under a completely different category. They are the result of geological upheaval and subsidence, being the remnants of ancient raised beaches. Starting from Start Point, and skirting the present coast-line, there is strong evidence of the existence of an ancient raised beach which once fringed the coast-line almost continuously.1. Opposite the hamlet of Hallsands a rem- nant of this raised beach formerly existed until the unfortunate official permission for artificial denudation was given, as will be detailed later. On the west side of the River Dart a second raised beach exists, and remnants of others in the vicinity of Bury Head, Brixham. At Hope’s Nose, Torquay, another raised beach exists, and at the point of Portland Bill a raised beach is again in evidence. The conformation of the Chesil Bank is in many respects unique.? It is a vast breakwater of stones assembled from many sources. In the Dorchester Museum there is a collection 1“'On the Origin of the Chesil Bank” (Joseph Prestwich), Proc. Inst. C. E., Vol. XL, pp. 61-114. 2 “Description of the Chesil Bank, with Remarks upon its Origin, the Causes which have contributed to its Formation and to the Movement of Shingle generally" (Sir John Coode), Proc. Inst. C. E., Vol. XII, pp. 520-57. 40 THE FORESHORE of stones from the Bank, and these are in the following order of abundance :— (2) Chalk flints; (6) Greensand chert; (c) Portland limestone and chert; (d) Quartzites resembling those at Budleigh Salterton, and other far-travelled rocks of doubtful source. In rear of the Bank is the Fleet, a fiord running between it and the mainland, and varying from } mile to 1 mile in width. In this fiord tidal influences are insignificant save at its opening. By forces set up under the Channel currents the line of the ancient raised beach already described has been forced shore- wards, the Chesil Bank being a remnant of it, the west end of the beach having been driven up to the shore opposite Abbots- bury. Between Plymouth and the coast of Brittany the Channel is about 112 miles wide. Between Portland Bill and Cap de la Hague the width is suddenly reduced to 60 miles, widening to the eastward again to over 100 miles. The effect of this sudden contraction is the creation of the Race of Portland on the north side and the Race of Alderney on the south side of the Channel. Off Portland Bill the velocity of the race is 5 or 6 knots. Under the stress of its currents, combined with the blow of heavy gales, the old shingle beach has been steadily pushed back and the present contours of the coast-line created. The Bank runs from Abbotsbury eastwards for a distance of 103 miles, having a width at the base of 500 feet at the west end, increasing to 600 feet at the east end. At the west end the crest normally rises 23 feet above high-water level; at the east end to a height of 43 feet. The foundation of the Bank is Kim- meridge clay, at a depth of 8 fathoms of water. The section of this natural mole is highly instructive. At its east end, from the crest to a depth of 44 fathoms, it has a mean seaward slope of 1 in 54; for the next 2 fathoms this flattens to 1 in 8, and to the base in 8 fathoms to 1 in 30. At its west end toa depth of 34 fathoms the mean slope is 1 in 7; for the next 2 fathoms 1 in 11, and to the base in 6 fathoms 1 in 30. After the great storm of 1852 Sir John Coode took a series of sections, which showed that nearly 4,000,000 tons of shingle had been swept THE FLEET 41 down into deep water. In severe onshore gales the crest assumes a slope of 1 in 9. After a period of slack weather or offshore winds it is sometimes as steep as t in 2}. One curious phenomenon on the Bank is the automatic grading of the stones composing it. Starting from the west end at Abbotsbury, the stones average about 14 ounces, whereas at the east end they increase to about 13 ounces. The late Mr. Clement Reid, F.R.S., has noted the great difference between the wear of pebbles from varying geological deposits. He points out the curious fact that on coast-lines which are entirely of chalk, the sand is not flint sand but quartz sand, and he states that the distinction between the two classes of sand under the microscope is quite easy. -----— > oy NY oo aaae pS eo oc a er 4 pp os oe fh th ee coe ne a4 Ls) Bos Se 4 4 ccciemaed fa eR SST Sc minmieln. eas Galea at AN si anal Macias a NE ene ag Seca aoa 4 = So { Seat ee ons, oe tr Baie aon —- Vee ee L—} }-—_ pas ae ee a = seven [oer IN See ed |= pe nM - =} OP CR 1 a) ee 4 i —<<--— -—+——- 8 mee --— 4 ----==- iE oF Aamo nod teh Sereda pr ae 5 Pies eee ncs fie fo gee FC fo: ee a Gr] po a 4 ets ee aS -" fp == ===! educa > - -—+ jer —— 8 caeaeeeg en sa eas a ++ -—Y reg Zee pS 4 eee ee fi poe eee Se SS eee i Ep == eee - C3 pare eee 2 SS ey, coe Gad Pe oe a Pe SSeS ee e | bee toto Ht 3 CTE 4 A I ee or RE = tee ee NIN i ca a masa seee a a i ema eee cy js “+ po ee ey a on 1 pata RS a ato a MN eet Sod ee eee fe Brot 1 eee eee ee a See ee See s i sama mS Ey = N 5 eeu aioe cae 6 « SCAL to 10. FEET, ELEVATION OF TYPICAL HIGH GROYNE MIDDLE LEVEL DRAINAGE 141 with the flowing tide. This operation was successfully carried out, and the subsequent procedure resolved itself into providing for the escape of water still impounded through a sluice fixed in the timber staging with that object. Thus, little by little, the volume of water impounded was lowered, and at the same time a constant stream of clay was tipped behind the stage, large quantities of stone having been thrown in front of the toe of the stage to weight it in position and prevent pressure from behind driving it forward. The ground immediately in rear of the breach was so precarious that when the stability of the temporary works was assured an inset wall in rear of these was constructed. By this time the drowned marshes had become to a moderate degree ¢erra firma, and the first operation was to cut away the surface of the natural soil for a few feet, so that the inset wall might rest upon a fairly solid platform. The wall was then built up in puddle clay tier by tier. An operation of this character requires the most exact care. Theclay has to be dumped in layers of about 12 inches to a uniform level, and then well trodden and punned into the stratum of clay below. In Australia it is a common practice to drive a flock of sheep backwards and for- wards over a wall of this kind when under construction. The object to be attained is a complete blending and amalgamation of the layers of clay, so that no veins or fissures remain through which water may percolate and thus cause slips. The inset wall so constructed was laid out to a slope of 2 to 1 on the river face, and 14 to 1 on the back, and for several lengths, where there was a tendency to slip, short elm piles were driven along the toe. The whole of the face of the inset was subsequently pitched with block chalk 8 inches thick and Kentish ragstone 12 inches thick, carried to within 3 feet of the crest of the wall. The apex of the wall was left 3 feet wide. The unstoned portion of the wall was sown with grass seed. When the inset wall had been completed, and allowed several months to consolidate and season, the timber dam was removed. This required much caution, as small gaps in the timber work would have caused rushes of water, which might have disturbed the equili- brium of the finished work. The paper of the late Sir John Hawkshaw describing the 142 TIDAL LAND RECLAMATION bursting of the St. Germains sluice on the Middle Level Drain- age near King’s Lynn, and the subsequent measures taken to stop the breach, which inundated upwards of g square miles, or about 6000 acres, will be found in the Proceedings of the Institution of Civil Engineers, Vol. XXII, pp. 497-508. The tidal influx was shut out by the methods detailed above, the impounded water was then drained away and the wall restored. Following on the lines indicated above, it is safe to say that almost any breach in a sea or river wall may be successfully shut up. There are, however, so many side issues and con- tingent possibilities that it is an operation requiring experience and skill to avert disaster. CHAPTER IX Erosion and Accretion (Works) Although an inlander, Shakespeare in his sixty-fourth Sonnet has defined with precision the problem of the action of sea forces on a mobile line of foreshore, thus:— ‘*T have seen the hungry ocean gain Advantage on the kingdom of the shore, And the firm soil win of the watery main, Increasing store with loss and loss with store”. According to the evidence of the Director of Ordnance Sur- veys before the Coast Erosion Commission, it would appear that the balance of gain of land over loss of land in the United Kingdom and Ireland, taking the respective dates of the Ord- nance surveys detailed by him, was a gain of 41,362 acres. On the basis of the reports of the Board of Agriculture, the total area of land, not including tidal lands, showed a comparative falling off in acreage. In thirty-three years this falling off in the United Kingdom amounted to 182,000 acres. The Director explained the discrepancy as due to the fact that some of the figures in the reports of the Board of Agriculture were esti- mated. The element of uncertainty already referred to in respect of the delimitation of high-water line on the Ordnance Survey tends to throw some doubt on the accuracy of the official figures in each connection. The notorious fact remains that, whereas large areas of land are disappearing under attacks of the sea, corresponding areas of reclamations or innings are not in evidence. Whichever way the balance of area goes, it is obvious that the land which is being washed into the sea is for the most part good agricultural land, and, in some cases, 143 144 EROSION AND ACCRETION valuable town land; while the land from which the sea recedes is in the main a sandy swamp of little intrinsic value. The foreshore is a plateau of land and water, varying from wide sandy wastes, such as the Shoeburyness sands, to lengths of coast-line which the tide barely leaves. The sea is nibbling on many fronts, but there are comparatively few spots on the British coast where, at the present time, there is marked reces- sion. In the Persian Gulf, blown sand from the desert comes down in such volumes that it is shoaling the Gulf. The vast sand travel along the north-east coast of Brazil is overwhelming, as the sea for several miles from shore is laden with sand in suspension. Movements of sand such as these are almost be- yond human control, and any obstruction placed in their way is quickly obliterated. The most striking record of both accretion and erosion is that of Madras harbour. Along the eastern coast-line of the Indian peninsula, under the impact of the north-east and south- west monsoons respectively, sand had travelled up and down the coast-line almost harmlessly from time immemorial. The Indian Government in 1876 determined to construct an enclosed harbour at Madras. Careful observations were made of the volume of sand travel, and it was estimated that it would take 180 years for the travelling sand to fill a triangular area between the coast-line and a breakwater running out 1200 yards from the shore. No sooner, however, were the works commenced than it became obvious that the above estimate of sand travel was completely unreliable. The wave-borne sand, travelling up from the south, was about sixty times greater in volume than the corresponding amount brought down by the north-east monsoons. The original estimate of sand in motion was 243,000 tons per annum; a second estimate in 1904 was 550,000 tons per annum. The accumulation at the present time shows that about 1,000,000 tons per annum travel along the coast-line. Low-water line between 1876 and 1912 has crept seawards for a distance of 2500 feet (fig. 35a). In 1881 a terrific cyclone wrecked the harbour works, then nearly completed, but a some- what similarly outlined harbour has since been carried out on altered lines. For a distance of more than 3 miles severe SHINGLE BANKS 145 erosion has taken place on the north side of the harbour, due to the arrest of the normal column of travelling sand, and whole towns and villages have thus been swept away. This experi- ence is an extreme instance of the action which goes on in a greater or less degree at every headland, river mouth, or solid projection from a foreshore into the sea.? The ameliorative artificial works by which a coast-line is maintained are in the main sea-walls and groynes. Stability may also be assisted by fostering the growth of foreshore vege- tation. When once such vegetation has secured good hold of a coastal area, its effects materially aid the pre- servation of artificial works. The bane of coastal defence is often the procrastination of Ae landowners and _ local f pee” authorities. In num- berless cases action has been deferred until the ae ee problem of defence has Fig. 354.—Madras Harbour—Change in Low-water Line become tenfold more acute than it would otherwise have been. Moderate expenditure on preventive measures are postponed until costly remedial measures become necessary. It has often happened that a shingle bank has existed and acted as a barrier of defence such that, had steps been taken to avert its dispersal, this state of affairs would have continued for an indefinite time. The com- paratively small expenditure necessary for securing this object, however, has not been forthcoming, with the result that such shingle bank has been spread, and its crest lowered, so that it no longer acts as a line of defence in heavy gales. Extreme weather conditions are what do the mischief in such cases. In a single tide, a protective barrier of this class may have its LINE OF FORESHORE !875 QO. 5 9 ro00 2000 FEET 1 “The Sanding-up of Tidal Harbours” (A. E. Carey), Proc. /nst. C. £., Vol. CLVI, PP. 1-90. (0924) 11 146 EROSION AND ACCRETION utility destroyed by reason of the crest being driven shorewards, the rollers then passing clean over the bank. Had the problem been taken in time, a light concrete wall, acting as a fence to hold up the barricade of shingle, would probably have saved the situation. By putting such light wall well in rear of the shingle barrier, the process of heaping up goes on, and the sea forces are ultimately powerless to disturb the defence pro- vided by Nature. It is too often forgotten that shingle banks are a definite asset in defence. Once lost they can never be restored or replenished, except by costly measures, involving dumping material from other localities. On a normal coast-line on the south of England, a sea beach will be heaped up by the forces of the waves to a height of about 23 or 24 O.D., that is, 5 or 6 feet above mean spring-tide high water. This action often goes on to 27 O.D. or higher. As regards the strength of sea-walls, obviously if a good shingle bank exists in its front a lighter wall suffices. It is desirable in most cases to carry the level of the top of such sea-wall to a height of 8 or 10 feet above mean spring-tide high-water level. The contours of sea-walls have furnished much debate. It is extremely doubtful if the large additional expenditure neces- sitated by many abnormal designs is justified. A sea-wall and its allied natural defences of the foreshore are, after all, intended to stop the run of the sea in the same fashion that a bullet is stopped by a target. It is a question of weight versus momen- tum, and mere finesse of design under these circumstances is not worth paying for. Many of the sections adopted are based on sound theoretical lines, but it is probable that an ordinary straight-fronted wall, having a batter of about 1 in 8, would have given better value for the expenditure involved. Curvi- linear and stepped walls necessitate undue capital outlay in construction. By a somewhat thickened section stability could be equally well obtained at less cost. Destruction of a sea-wall has frequently been brought about by the digging action due to the cascade of water recoiling from the face of such wall, and striking its pervious foundation at the toe. In this case a trench is excavated along the front TOWN PLANNING 147 edge of the wall by the rush of water, and the wall falls out- wards. In the majority of instances this effect is due to the fact that proper measures have not been taken to conserve the accumulations in front of the wall, or, as an alternative, todump shingle or stone along its frontage, which method would have created a buffer between the stroke of the waves and the wall. In a great number of cases, the first idea of those responsible for works of this class is to build a structure as massive, and therefore almost as expensive as a breakwater. From the rate- payers’ point of view this may be magnificent, but it is not business. The art of design is to effect the desired end by making Nature do your work for you as far as that is practic- able. There are exposed positions where, almost inevitably, a sea-wall has to bear the brunt of the full momentum of heavy seas. Under such conditions, no doubt a curved or stepped wall is more effective than a wall with a nearly vertical face, but it is in the main doubtful if the ratio of its efficiency in this respect could not be achieved by less costly methods. One expedient of this character is the formation of an apron at the toe of such wall. Reinforced concrete will probably be found the most efficient material in its construction. Great care has to be taken to carry the apron sufficiently seawards, and to build its front edge sufficiently deep to counteract the effect of the scour induced by recoil from the wall, which is apt to set up a guttering action, thus tearing out and undermining the front edge of the apron and causing its collapse. An apron built with this object should be constituent with the wall, and the reinforcement between the wall and the apron fairly massive, to counteract the tendency to cracking by unequal settlement at the junction of the apron and the wall. The apron also requires to be built with expansion joints, so that minor settle- ment may not cause dislocation and thus disintegration. In nine cases out of ten the policy of pushing the edge of a parade to the extreme limit seawards is the cause of much of the useless expenditure entailed on the fronts of sea towns. It is a form of greed which recoils upon itself, as the amenities of a seaside resort are greatly enhanced by leaving a strip of open ground between its houses and the actual foreshore. By 148 EROSION AND ACCRETION this means the growth of the natural protecting medium of defence can generally be so fostered as to obviate the necessity y O Fig. 36.—Bull-nose Coping of massive works fronting the beach. The question of a bull-nose coping to a parade wall is also one which has given rise to much discussion (fig. 36). This design is intended to throw back the spray tangentially from the crest of a wall, and thus prevent its sweeping over the parade. It is obvious that in so doing the blow of the sea is largely resisted by the coping, which action must set up severe stresses in the wall. By dumping, if a sufficiency of shingle or sand does not exist, and a well-devised system of groyning to hold the accumulation, the momentum of the sea can be, to a large extent, absorbed before the waves actually strike the wall, BBE and thus the whole razson MATERIAL @étre of the bull-nose coping disappears. Recent investigations on wave impact! have brought to light the fact that, where [eines aurtress fissures or open joints exist on rove CENTRES a sea-wall, the dynamic pres- sure of a wave may multiply the force of the blow fifteen times. A dynamometer pres- sure of 2 tons per square foot would, on this basis, be equal to a pressure of 465 lb. per GORE FILLING edldcacigacs square inch, a force which 10 5 ea I would severely stress an or- Fig. 37.—Carnarvon Sea-wall (Reinforced Concrete) inary masonry joint. The introduction of rein- forced concrete is revolutionizing marine construction. Fig. 37 represents the section of a sea-wall recently erected on the North 1 ‘Wave Impact on Engineering Structures” (Professor Gibson), Proc. Just. C. E., Vol. CLXXXVI, pp. 274-91. GENERAL CONDITIONS 146 Wales coast. The cost of this wall was £6. ros. per lineal foot, and not only had the wall to withstand severe sea attack, but, owing to the fact that the filling behind it could not be deposited at the time of its construction, to be left unsupported. It has fulfilled its function with complete success. Fig. 38 is a section of the sea-wall built at Hove. Fig. 39 represents that of the west spur of Newhaven breakwater. In these instances a solid concrete structure has cheaply fulfilled the prime function of a y LOWEST KNOWN LEVEL y BEFORE CONSTRUCTION OF WALL SCALE OF reeT o & to ! Fig. 38.—Hove Sea-wall (Mass Concrete) Fig. 39. Newhaven Sea-wall (Mass Concrete) sea-wall under severe conditions of exposure. Wherever prac- ticable, it is eminently desirable to build a sea-wall in mass concrete rather than in blocks, as a monolithic structure is less liable to dislocation than a structure intersected by joints. In many of the textbooks the question of sea defence is treated as a matter of mere cash debit and credit. On the one hand, the cost of constructing foreshore works of defence is defined, and the assumed value of the land to be protected is set in an opposite column, and schemes are either approved or condemned on the standard of direct profit and loss. It is probable that in the near future these problems will be dealt with in a different spirit. So far as the cost of foreshore works 150 EROSION AND ACCRETION is concerned, the figures of a year or two back no longer hold good. On the other hand, it is likely that issues deeper than the mere money value of the land concerned will be the dominant factor in future proposals of this class. It has been calculated that if three-fourths of the cost of groyning those portions of the coast-line of English counties most affected by erosion were charged on the respective counties, they would represent the following rates:— Sussex, 1d. in the £; Norfolk and Suffolk, 1d. in the £. The assumption in this case is that the landowners immediately affected would provide one-fourth of the total cost, the counties pay the balance. At a rough approximation, about 500 miles of the coast-line of England and Wales are in varying degrees subject to erosion. The action of depletion is due in the main to oblique littoral drift. Where a coast-line is sandy, the wind-waves throw the sand into suspension, and the currents drive it along the shore. On a shingle coast-line wind-waves are the prime motor in its movement. Rollers bring in shingle and sometimes large masses of rock from deep water. It frequently happens that, after a severe gale in the Channel, boulders weighing several hundredweight will be found strewn along the strand. These are mostly weed-covered. The growth of weed evidences the fact that the action of the waves has reached sea depths normally tranquil. In exposed portions of the coast-line of Scotland, boulders upwards of 2 tons in weight are similarly thrown up after storms, and their occurrence on these spots is so much a matter of course that they go by the name of ‘‘travellers”. Their buoyancy being increased by the crop of seaweed they carry, they are pushed along the sea bed under the impulsion of the deep-water rollers. As an instance of deep- sea wave action may be cited the fact that concrete blocks at Peterhead harbour, weighing 47 tons, were forced out of position at a depth of 4o feet below low water. Under normal weather conditions, shingle’ or sand on a foreshore hugs the coast-line, moving to windward or leeward DANGEROUS GROYNING 151 under the alternation of the wind-waves. On the English Channel, the prevailing wind exposure being from the west and south-west, eastward littoral drift is the normal condition. In a few instances, however, due to recoil under the lee of salient points, wave action and the currents are locally reversed. Thus at Newhaven, before the breakwater to the west of the harbour was built, the uniform movement of the beach was from west to east, but for a distance of some three miles to the east of New- haven the shore forces now swing round in the opposite direc- tion, driving the beach, and more especially the sand, from east to west. In the North Sea the severest wind conditions are those from the north-east, gales from the south-west being off-shore. The coastal phenomena of the English Channel are there repeated, as from the quarter of greatest exposure. The building of groynes has been, broadly speaking, a matter of trial and error. The expedient is coeval with foreshore defence. Groynes laid out to all sorts of angles, and of every variation of design, occur along the English coast-line; in fact, some lengths of shore-line are almost museums of devices of this type. The established standard practice of twenty or thirty years ago was to lay out groynes at right angles to the shore- line. As, however, the direction of a groyne and the coincident stroke of wind-waves are collateral, it is obvious that no uniform rule adequately applies to a coast-line which may be infinitely varied in trend. Theoretically, if the stroke of the maximum wind-waves on a groyne impinges at an angle of 45 degrees, this would be the ideal condition. Groynage is, however, governed by so many local considerations that no broad uni- versal rule can be established. The factor which proves good design in groynage is the equality of accumulation to windward and leeward of the structure. Wherever a foreshore consists of a series of steps, shingle being banked up to a great height on one side of its groynes, alternating with bare patches of fore- shore, it is safe to say that the trend of the groynes is badly designed. Where a line of groynes is deflected to form an acute re-entrant angle with the windward stroke of the waves, a con- dition of danger is created, as the run of the sea is thus 152 EROSION AND ACCRETION impounded in the angle between the groyne and the barrier of defence behind it. The sea being gorged, its force is con- centrated, and the danger of the destruction of the groynes by direct impact increased, as well as the scouring effect. Under these conditions the force of recoil is intensified, with the result that beach is dragged down along the line of the groyne and a deep gutter created, tending to undermine its foundations. Probably, in the majority of instances, a groyne placed nearly at right angles to the maximum force of the wind-waves gives the best results. Its direction may be modified a few degrees to windward or leeward of this line, as observation of the action on a particular stretch of coast-line indicates. The tendency of the designers of groynes protecting one particular stretch of coast is to trap all littoral drift. This is in effect to starve the coast-line to leeward. The ideal con- dition is that of circulation in compartments, the column of drift oscillating under the varying conditions of wind and weather, and leaving, as nearly as practicable, a uniform in- cline on which the sea forces may spend themselves harm- lessly. At the outlet of a harbour or river the construction of spur groynes is one of the most efficient devices. It achieves two results :— (a) The arrest of the travel of the circulating medium, thus preventing the formation of bars or spits, which distort the contour of the outfall of the harbour or river, cause an impediment to its flow, and set up conditions detri- mental to navigation. (6) A well-formed spur groyne forms an embayment, and if a series of these is constructed, retardation of travel is brought about, so that on the windward side of a harbour or river an artificial ness is created, sheltering the foreshore. The action of coastwise retardation of shingle or sand may by this expedient be prolonged and a dangerous coast-line effectively defended. The critical portion of a spur groyne is on the outer edge at its junction with the main groyne. It there receives the full stroke of on-shore seas, and the tendency to ROMNEY MARSH 153 scour is greatest. At this point, therefore, special precautions in design have to be taken. With regard to the determination of the height of groynes, their purpose and situation have to be carefully studied. The classic instance of defence of a low-lying sea frontage is that of Romney Marsh. From points of vantage in the town of Rye, the vast expanse of this marsh, dotted with cattle and sheep, may be realized. The low-lying area is about 60,000 acres, much of it 1o or 11 feet below high water. The severest seas strike from the south-east, as Dungeness affords shelter from the south-west. The marsh includes some of the fattest pas- turage in England, and measures for defending it go back to Roman days. About a hundred years ago, Sir John Rennie advised on a system of groyning carried out with brushwood held in position by hop poles. Thereafter the bank appears to have been neglected and left very much to chance conditions. At the commencement of the Victorian era, a new régime of defence was inaugurated, the sea slopes being paved with stone pitching laid on concrete, the lower slopes at a gradient of 1 in 9, the upper at 1 in 7. As far as practicable, the stone- work was flushed with cement. This system was followed by pronounced erosion, heavy storms in 1859 and 1869 tearing out great areas of the stone pitching, an effect induced by the action of underwater scour, set up by the recoil from the paved fore- shore, or that described by Captain Calver as ‘‘ scavenging”. During the next twenty years, a sum of nearly £70,000 was expended on patching the foreshore, but on the appointment of the late Mr. Case as expenditor its condition had grown serious, as in the year of his appointment areas of over 8 acres of stone pitching were scoured out. Heavy groyning was recommended, but Mr. Case eventually carried through a complete system of low groynage. The timber scantlings he adopted, though of an unusually flimsy description, proved effective. He embedded the groyne uprights in concrete pits sunk in the foreshore. He thus built 420 groynes, and sometimes completed a groyne in the day. The result of the system he adopted has been the preservation of this dangerous coast-line, and the accumulation 154 EROSION AND ACCRETION of several million yards of drift, mostly sand, at relatively small cost. The protection of Romney Marsh affords a striking in- stance of success achieved by economical expedients, and of the abandonment of costly heroic measures which would have eventually led to disaster. The system of low groynes, although in the majority of instances desirable, is not universally so. The art of building up a foreshore is to adjust the height of the groyne system to its accumulating volume of littoral drift. After depletion it is often prudent to remove planking from groynes in order to cause less obstruction to the run of the sea. Conversely, when rapid accumulation takes place, additional planking should be added to capture such travelling medium of defence.! On foreshores where extreme artificial conditions exist, high groynes are sometimes essential, and if such groynes were lowered erosion would at once commence. The sea front of Brighton is a case in point. The cliffs to the east of Brighton having by groynage been starved of their natural protection, have been severely eroded, the coast-line being set back in a deep indent, which involved a detour of the high road to New- haven. The bank of shingle thus accumulated to the westward of Kemp Town is an artificial barrier, which would be quickly lost and the front of the town threatened if the groynes were lowered. By prolonging a system of groynes seawards, and thus creating a plateau of foreshore at a flat gradient, the most efficient defence is secured. Plate XIII (p. 140) shows a groyne constructed on a point of maximum erosion on the East Coast. The building of this groyne involved much difficulty, as during its construction the width of foreshore was only 26 feet at low tide, and seas of extreme violence were rapidly undermining and causing landslides in the glacial-deposit cliff in rear. By a system of low adjustable groynes the safety of the threatened section of sea frontage has been completely secured, the coast-line for about a mile being thus rendered safe at an expenditure of about £2000. At the present time the groyne shown in Plate XIII is high and dry at low tide, and a flatly shelving foreshore, with wide stretches of velvet sand, 1 Protection of Seashores from Erosion (A. E. Carey). Greening & Co. GROYNE TYPES 155 exists in advance of it, recent accumulation being several hundred feet in width. In building some of the old groynes, more especially on the South Coast, an armoury of oak timbering was used, the prac- tice being to drive a secondary row of piles and connect the main structure with these by sticks of unsquared oak timber. These ponderous structures are, however, now few and far between. They were excessively costly, and proved no more effective than groynes built with ordinary piling and planking. The substitution in groynes of reinforced concrete piles in lieu of timber has been recommended, and in one or two in- stances adopted. It is, however, open to the objection that piles of this character are costly, that the difficulty of varying the height of such groyne is increased, and that the attrition of the shingle where much sea action takes place tends to scour the skin of concrete away and bare the steel reinforcement, which, in its turn, corrodes. In all probability, on the English coast creosoted pitch-pine piling will be found in the great majority of instances the cheapest expedient practicable. The depth to which these piles have to be driven, and the scantlings necessary, must be gauged by the local conditions prevailing at the particular spot. The patent system of the late Mr. Case, arising out of that adopted at Romney, whereby piles were embedded in concrete founda- tions, has on exposed foreshores proved unsatisfactory, as entire structures so built have in several instances been rooted out bodily by the sea. Taking the normal type of timber groyne, piles can either be driven in pairs, the planking being secured between, or alter- nately on either side of the planking, and on a coast-line of small exposure a single row of piles will sometimes suffice. Probably the most efficient structure results from fairly deep piles and longitudinal planking bolted alternately to right and left of such piling. The head of groynes should be carried to a fore-and-aft line of defence—either a sea-wall, a cliff-line, or an embankment. The practice which has sometimes been adopted, of leaving a gap between the shoreward end of the piling and the fore-and-aft defence is disastrous, as the swirl of the sea 156 EROSION AND ACCRETION running up the face of the groyne roots out and scours away the material at the head of the groyne and sets up destruction along the shore-line. The length to which groynes should be carried seawards depends largely on local conditions. Normally, on an exposed foreshore to be defended by a system of groyning it is desirable to carry at any rate some of the groynes from 50 to 70 feet beyond low water. It is this portion of the groyne which is most effective in building up the beach and preventing the dispersal of the material. The result, moreover, is the flattening of the foreshore slope, which is a great end to be attained. One of the most difficult problems in connection with coast defence is the protection of the coast-line of British Guiana. The low-lying portion of the colony consists in the main of deltaic alluvium, and its soil, agriculturally fertile, is unsuited to resist the inroads of the sea. The wind régime on this coast follows a regular sequence. During three months of the year attacks of the Nortes recur. When these hurricanes sweep down their effect is incredibly severe. The North-east Trade winds blow steadily for the rest of the year, but in the autumn months the sudden stroke of the Nortes is a recognized pheno- menon. Under the impulsion of these winds a furious rolling sea strikes the coast-line. According to the Report (dated 1910) of the Colonial Commissioners appointed to enquire into the subject, it would appear that the average annual expenditure on sea and river defences for the previous ten years had been not less than £12,000. In the previous forty years the average rate of coast erosion had in some localities been 32 feet per annum, and many vital fagades of the colony were thus threatened. A lack of continuity of defensive measures to cope with the trouble seems to have rendered the efforts of the colony some- what ineffective. The problem of the Guiana coast-line would appear to resolve itself into three elements :— 1. Measures to render the crest of the coast-line immune from the actual transit of the seas. 2. Measures for safeguarding the visible foreshore of the coast-line. In this respect systematic plantation, supplemented by some defensive work, would appear to be necessary. DANISH GROYNES 157 3. Below the visible foreshore the most promising expedient would appear to be that of fascines, but fascines of special design, in view of the extreme conditions. The most recent systematic construction of groynes on a large scale is that carried out on the coast of Jutland between Ferring and Agger.!| The physical characteristics of the land in rear of the coast-line along this frontage of about twenty miles greatly resemble the conformation of the coast-line of Suffolk and Norfolk. In both cases the superficial deposits are those left on the melting of the ice after the Glacial epochs. Extensive areas of marshy country and lakes with connecting streams have in each instance thus been dammed back. The principal impounded waters on the Danish side are those of the Limfjord. This is a wide expanse of mere, and the Thyborén Canal has been cut out as a navigable approach to it. The Limfjord is a valuable fishing area, and had the attenuated coast-line between it and the North Sea been breached, much rich agricultural land would have been converted into swamp and the fisheries destroyed. The sea bed consists of fine sand with a little shingle, and here and there, at a depth varying from 16 to 32 feet, of sandy alluvial clay. The total expenditure incurred by the Danish Government on the defence of this strip of coast up to July, 1913, was £666,000. Of this sum about 455,000 was spent on what are termed ‘preliminary works”. The Danish authorities, not having had previous experience in groyne construction, deposited blocks of concrete, in which the sand-mortar varied in proportion with the aggregate, and in many cases these blocks subsequently disintegrated. Up to 1894 the practice had been to mix the concrete 1:3:6 and even 1:4:8, but after this date the aggregates were mixed 1:2:4, and subsequently 1:2}:54. The final proportion for the mortar appears to have been a mixture of 37} Ib. of cement to the cubic foot of sand. The sand was white quartz sand, nearly all passing a sieve of 774 meshes per square inch, and nearly all retained on 5800 meshes per square inch. A longitudinal dike or embankment in concrete was constructed, and the 1 ‘(Experiments upon Mortar, and Diatomaceous Earth as Puzzolana, in Sea-water; with special reference to Groynes in Denmark" (A. Poulsen), Proc. /nst. C. £., Vol. CC, pp. 409-20. 158 EROSION AND ACCRETION groynes were placed 1230 feet apart. The longitudinal em- bankment cost about £5 per lineal metre of coast. The groynes were 620 feet long; at the shore end 14} feet above mean water- level, and with a mean fall of 1 in 60. The part nearest the shore had a slope of 1 in 20, the seaward end of 1 in 80. The size of the concrete blocks used in the groynes was about 62 cubic feet, each weighing about 4 tons. In the early stages of the work the granite boulders strewn on the sea bed of the Cattegat were used. For some portions of the front the dike was carried considerably in rear of the coast-line, and the inter- vening space became filled with blown sand. One matter of interest in connection with these works was the disintegration of the blocks. Unless complete water-tight- ness is secured in forming concrete structures, the percolation of the sea water is liable to cause disastrous disintegration, its effect being that the free lime under these circumstances is attacked by the sulphate of magnesia in the sea water and a chemical combination results, which causes the rupture of the concrete. In order to circumvent such mischief, which has been fully investigated on its chemical side in England, the Danish engineers experimented with the addition of various siliceous earths occurring in the peat districts. The difficulty to be overcome is in its ultimate issue a physical one, as if the concrete used is free of intersticial porosity, the penetration of the magnesium salts is prevented. The diatomaceous earth thus used as a diluent and pore-filler passes under a number of different names in various localities. Its essential ingredient is silicic acid in an active condition. The material which the Danes call Mo-ler is found in the Thyboron district, containing about 70 per cent of silicic acid. To each cubic metre (say 3080 Ib.) of Portland cement, 1320 lb. of the local earth were added, and the two ingredients ground together. The effect of the combination appears to have been satisfactory in preserv- ing the resultant concrete from disintegration. One broad issue in respect of policy is to be noted. Den- mark, a relatively poor country, in order to safeguard agri- cultural and fishing industries, has constructed from national funds seventy groynes, with intervening dikes, at a large BOX GROYNES 159 capital outlay. The area behind the corresponding English coast-line, relatively of greater value, is left without systematic defence against the inroads of the sea. The principal types of groynes on the English coast, other than those already described, may be summarized as follows :— Type No. z consists of piles about 12 inches square, driven from 8 to 10 feet apart, planked on one side, and with a single waling on the other, and held down by land ties secured by rows of short piles to right and left. The planking has to be carried a few feet below the lowest beach level, and the piles are sometimes stiffened by having short strips of railway metal bolted to them. In Zype Vo. 2 the vertical timbers of the groyne proper are carried by transverse sole pieces attached to two rows of piling, the uprights being in pairs and the planking placed between them, with rakers as in the last instance. This is an undesir- able type of construction. Type No. 3 is similar to Type No. 1, but instead of timber piles old railway metals in pairs, with planking between, are used, and the ties are also of iron. This type is not to be commended, as it is difficult of adjustment, the iron corrodes, and after a heavy gale is apt to become twisted out of shape. Another system is a modification of the Case groyne, already described, its essence being to embed the uprights of the piles in concrete pockets. The lower half of the uprights of the groynes in St. Margaret’s Bay are so embedded, the upper half of the piling being driven in the ordinary way. Sometimes raking timbers are only fixed on one side of groynes of this character. Some years ago the patent Dowson groyne was exploited, and a few such groynes were erected. The principle of this is to substitute for planking a steel mesh between the piles, the theory being that the shingle would be caught on the mesh and the weight of the water allowed to pass through the groyne. These groynes, though highly ingenious in design, have not commended themselves in practice. A distinct form of groyne is the box groyne, which consists of two rows of piling, both being planked, and the intervening space filled either with beach or rock. This type is doubly 160 EROSION AND ACCRETION expensive, and very liable to disintegration. It approximates to the practice in Holland, where the groynes (golfbrekers) are usually about 500 feet long, spaced about 200 yards apart, and run at right angles to the shore. Golfbrekers are elaborate structures, in fact breakwaters in miniature. They are some- times laid in the form of a mound reaching at the sea end a few feet above low-water level, and they rest upon fascines. The summit of the mound is basalt-pitched, with two pairs of rows of piling, one on either side; brick rubbish is placed over the fascines, and the basalt pitching laid on edge on the brick-work, the outer slopes being protected by dumping loose masses of stone pitching, either basalt or limestone. In some cases the crest of such groyne or breakwater is protected with concrete slabs instead of basalt pitching, the other portions of the section being as already described. On the Brighton front groynes of the most formidable char- acter have been erected. These are in effect massive stone piers faced with flint and with a hearting of mass concrete. The sides of these piers are mostly built at a batter of about 1 in 4, and sometimes they are laid out as promenades. At Dover a somewhat similar pier, 10 feet in width at the top, running almost level for about 100 feet, and then dipping at inclinations of 1 in 5, 1 in 64, and 1 in 8 down to low-water line, the total length of the pier being 289 feet, was built in 1860. At Hastings a concrete pier was built at the spot which was, at the date of its construction, the extreme east end of the fore- shore of the Corporation. The result of this obstruction has been the arrest and impoundage of an enormous mass of shingle. Immediately to the east of the pier there is a sheer drop of about 25 feet, and the foreshore of sandstone rock is severely eroded. The east cliffs, purchased by the town for the purposes of a recreation ground, are now vigorously attacked by the sea, as they have no protection at their foot. Almost every winter great landslips take place there. In the instances of these three towns, which are fairly typical, is demonstrated the vicious circle of original bad planning which has brought about so much destruction of the coast-line. The towns have gradually grown up to an arbitrary sea con- LAND DRAINAGE 161 tour, and there is nothing for it but to maintain that artificial frontage. Those who are responsible for thus keeping intact dangerous salients are compelled to resort to sea-walls and groyning of so massive a character that they are unassailable. The defences of the town in effect constitute a blockade, which starves the coast-line to leeward and destroys the regular sweep of the shore, a factor setting up the familiar phenomenon of irregular inroads of the sea. The distance apart of groynes is a matter which must be dealt with on purely empiric lines. If it were attempted to evolve a formula or general law on the subject such formula would have to be in terms of the angle of inclination of the foreshore to the horizon and the local rise of tide. These are the main factors in determining the point. A rule commonly stated is that of placing the groynes a distance apart equal to their length, but such spacing is purely arbitrary, and is not based upon any physical reason. The average inclination of the foreshore on the English East Coast is about 1 in 15, the inclination on the English Channel averaging about 1 in Ir. Where the foreshore runs down into sandy flats the gradients of these are up to I in 100. The profile of the foreshore of the Dutch coast is variant, but along its sandy flats the ruling gradient may be probably taken as about 1 in 30 to 1 in 40, and on the sea marge as flat as I in 100. One matter of serious moment in connection with the conser- vation of a coast-line is that of land drainage, more especially where high ground or cliffs abut on the seashore. The instances of the North Parade at Scarborough and of the sea front at Frinton may be quoted. In the former case, with the object of diverting land drainage, an expenditure of £26,000 was incurred, and in the case of Frinton an intercepting drain was laid for a length of 3860 feet at a cost of £1390. It is probable that by systematic and scientific planting a threatened land slope contiguous to a foreshore may to a large extent be par- tially unwatered, and the expense of heavy drainage works thus lessened. (0924) 12 162 EROSION AND ACCRETION With regard to the life of foreshore structures, this varies to a great extent with the exposure and the nature of the materials of which they are built. The Local Government Board has no standing rule on the subject in respect of the periods for which they give authority for loans, but the following are their usual terms, which are rarely departed from, and they furnish a fair index, being based upon long experience :— Esplanades ... tea aes eee +s 30 to 20 years. Concrete groynes ... eee +. 20 years. Reinforced concrete sencnies one oe 15 years. Wooden groynes_... es oes +. =o years, Pitching sles eee an eae one 5 years. Sea-walls ... os 08 ws «. 20 years. A rough approximation of the average cost of normal wooden groynes in the past may be taken at 25s. per lineal foot, but the variations in this figure were extreme, and ancient history has little value in respect of current work. Below low-water mark the travel of sand goes on almost un- impeded. This travel is one of the most troublesome problems. In a few hours the results of many laborious months of dredging may be completely obliterated. In older engineering practice the problem of sanding up has been perennial. Harbour engineers and those responsible for navigation have been com- pletely baffled, and many a promising harbour, on which a large expenditure has been incurred, rendered almost useless for the special traffic to be catered for. The underwater movement of sand and the ease with which it adjusts itself to altered con- ditions may be illustrated by a parable. In the folk-lore of present-day Yorkshire, and going back thence to remote Scandinavian legend, is a belief in a domestic attendant sprite, Hob by name. Shakespeare calls him Puck. The exploits of this demon are sometimes malicious, sometimes beneficent. After a period of vexatious ill-luck, obviously the handiwork of Hob, the story runs that once on a time a troubled farmer determined to find safety in flight. With his household gods on a cart, a neighbour meets him. ‘‘Ah sees thou’s flittin’,” Saye the neighbour. ‘‘ Ay,” Hob pipes out of a churn, ‘ay, we’se flittin’.” SAND TRAVEL 163 In the ports on both sides of the Channel, as the sand travel has perplexed harbour authorities their traditional policy has been to push the entrance piers into deeper water as a means of eluding sand travel. Inevitably, as the piers are extended seawards, so the sand has crept out after them. The sum of the palliative measures may be stated as— (1) To conserve and concentrate the tidal scour of the ebb tide; (2) To train the sea outfall; (3) To dredge. CHAPTER X Plant Winning of Tidal Lands—Salt Marshes The Salt Marsh is tidal land par excellence. Its basis consists of silt and mud, that is, of the most finely-divided erosion pro- ducts. These materials carried in suspension into estuaries or other sheltered positions, such as the lee side of spits, &c., tend to be precipitated at slack water. In these positions the mud is normally colonized by vegetation to form salt marsh. When in fullness of time a vigorous mixed vegetation has arisen, occupying a level overrun by the spring tides only, the marshes are termed ‘“‘saltings”’. Salt marshes, more than any other type of maritime land, show continuous change, both in the details of their topography and in their vegetation covering. In the case of shingle it is the exceptional storm or super-tide that determines important topographic re-arrangements, whilst for effective movements of sand on a dune system winds of considerable velocity are necessary. With mud, on the other hand, the normal daily flow and ebb of the tide are entirely adequate to transport and redistribute the particles. The most gentle of currents will lift and carry particles of clay, e.g. one flowing at 0.17 mile per hour (0.25 foot per second). The process operates at every tide; mud is being moved from one place and deposited in another. The aggregate result is topographic change. Creeks meander like rivers; ground is eroded away; silt is deposited on the saltings and their level rises. The change in level affects the physical character of the soil, whilst, with a rising level, the period of tidal submergence is shortened. Such changes unfit 164 ORIGIN OF SILT 165 the ground for the pioneer plants, and make it suitable for the establishment of other species, which operation finds expression in vegetation change. The more important salt-marsh areas in England include the estuary of the Severn, the waters about the Isle of Wight, the mouth of the Thames, the north coast of Norfolk between the shingle fringe and the mainland, the Wash, the Humber, Morecambe Bay, and the Solway. The original source of the materials is by no means easy to trace in all cases, for its determination depends either on following the particles in transit, or it has to be inferred from a detailed examination of the silt. Thus, there has been and indeed still exists a difference of opinion as to the origin of the ‘‘warp” in the Humber. According to one view it is derived from the rivers which converge to form this estuary; according to another it is brought up from the coast, where it is derived from the erosion of the soft cliffs which stretch northward from Spurn Point. Final decisions on such matters cannot be reached by guesswork, but must depend on long- continued systematic observations analogous to the records of the meteorologists. Broadly speaking, there can be little doubt that the materials in question are derived largely from the products of land erosion brought down to the sea by rivers, and that this source is supplemented by a greater or lesser amount of silt produced locally on the shore. The ratio between these two components will vary in different cases according to the hardness of the rocks involved and to other circumstances. In process of time the materials of all grades, shingle, sand, and mud, will be separated and classified by the sea. Whilst the heavier elements will in large part be thrown up as shingle beaches or sand- banks, and only under very exceptional circumstances pass beyond the zone of wave mobility, the mud which is long held in suspension will be deposited as to a part in sheltered estuaries, whilst the rest will drift out to sea, where it will fall in deep water and be lost to the coastal zone. Data illustrating the muddiness of tidal waters in the British Isles are not very abundant. The following figures refer to the 166 PLANT WINNING OF TIDAL LANDS shore waters of the Bristol Channel, where it has been ascer- tained that on the average every gallon of water in a flowing tide holds in suspension 4o grains. As the area involved in these observations was roughly 225 square miles, and reckoning the depth of water at 6 feet, there would be some 700,000 tons of mud on the move. Put in another way, for every square foot of ground there are 4 oz. of mud in suspension in the 6 cubic feet of water which stand above it. The circulation of mud is thus considerable, though, of course, in the British Isles there is nothing comparable to the huge amounts of suspended matter discharged from the mouths of great continental rivers. The Mississippi, for example, is stated to convey into the Gulf of Mexico every year 363,000,000 tons of detritus, enough to cover an area of 240 square miles to a depth of 1 foot.} But in any case it is hardly to be expected that the coast-line of Britain should provide the conditions of salt-marsh formation on the grandest scale. These belong to large continents with vast interior reserves of erosible mountain chains and highlands, not to small islands. Speaking quite generally, and without reference to the nature of the rocks, the erosible materials yielded by any land area will be proportionate to its area. That is to say, the volumes of detritus eventually brought down to the shore, per unit length of coast-line, will be functions of the radii of the land areas involved. Topography of a Salt Marsh.—Commonly the ground of an estuary or other inlet occupied by salt marsh falls into two principal areas, i.e. the higher level terrace or salt marsh proper, covered only at the spring tides; and the lower flats in part bare, which are covered by every tide (Plate XIV). These regions are distinguished by us as ‘Saltings” and ‘Slob lands”, by the Dutch as Schorre and Siskke. Here they will be referred to as High and Low Marsh, respectively. It is a character of high marsh to be carpeted with a con- tinuous turf of vegetation, the basis of which is the common Salt-marsh Grass (Glyceria maritima), and mingled in this turf is a considerable variety of plants, of which the most frequent 1W. H. Wheeler, Tidal Rivers, 1893, p. 60. Plate XIV Photo. J. Massart BOUNDARY BETWEEN HIGH AND LOW SALT MARSH High Marsh with turf of Glycerta maritima and much Aracria maritima; Low Marsh bare with scattered Sweda maritima (Right-bank, Estuary of Yser, Belgium) HIGH MARSH 167 are the Sea Plantain (Plantago maritima), Sea Lavender (Statice Limonium), Sea Pink (Armeria maritima), Sea Purslane (Odione portulacoides), Sea Aster (Aster Trifolium), and Sea Spurrey (Spergularia media). High marsh is traversed by numerous creeks or channels, by means of which the tide gains access to and drains off the marsh. There are usually one or more principal creeks and numerous subsidiary ones into which these branch. The tribu- taries get shallower and shallower till they die out on the marsh surface. On many salt marshes they end in low, wide depres- sions termed ‘‘pans”. These pans are apt to be bare of vegeta- tion and usually retain sea water after the tide has run off. The beds of the creeks are bare of vegetation except where the sides have caved and fallen in. The system of creeks is the circu- latory system of the marsh, and provides not only for the move- ment of water but also of silt. Much silt is transported by the creeks, and when they overflow the silt is carried on to the surface of the marsh, where it is fixed by the vegetation. High marsh on the side towards the main channel of the estuary generally ends abruptly in a low cliff 2-3 feet high. This cliff, like the sides of the smaller creeks, is liable to erosion. Where high marsh adjoins the mainland the ground rises slightly, and is usually characterized by the presence of dense tufts of the Sea Rush (Juncus maritimus), with which the low- growing Sea Milkwort (Glaux maritima) is often associated. This peripheral zone, termed the Juncus zone, is covered by the higher spring tides only. Its chief interest, in relation to the economic exploitation of salt marshes, depends on the fact that the rush being a most obstinate and deep-rooted plant, it has to be specially grubbed up in marsh reclamation, otherwise it may persist for half a century or more, to the great detriment of the grazing value of the area it occupies. Low marsh is covered by every tide; its lower stretches consist of bare mud, whilst the higher parts are colonized by pioneer flowering plants, of which the most characteristic are several annual species of Marsh Samphire (Salicornia annua, S. ramosissima), at once recognized by their cylindrical, leafless stems, recalling in habit a small, smooth cactus (fig. go). These 168 PLANT WINNING OF TIDAL LANDS plants occur in more or less open formation, that is to, say, the bare mud is visible between them. Some species (e.g. S. ramo- sissima) are liable to be coloured red, especially in autumn, by a pigment which masks the natural green Fig. 40.—Salicornia annua, half nat. size coloration. Where the plants grow at all thickly they form vivid crimson patches, a most tell- ing feature in the sunlit landscape. Another annual plant that occurs on the same ground is Sueda maritima (fig. 41). Both these plants drop their seed on the mud in the late autumn and die, though their dead stalks gene- rally resist weather- ing till the follow- ing spring, when the next crop of seedlings appears. Another very characteristic plant of the low marsh is the Grass-wrack (Zostera marina and Z. nana), with nar- row, _ribbon-like Fig. 41.—Suaeda maritima, half nat. size leaves spread out on the mud. Zostera reaches a lower level than either Salicornia or Suceda maritima, and most commonly occupies mud too soft to walk upon without sinking. Besides these flowering plants the low marsh bears a quantity of Algz, especially Enteromorpha, Rhizoclonium, and Vau- EROSION AND ACCRETION 169 cheria. The two latter are filamentous, whilst Enteromorpha, at first ribbon-like, may, when full-grown, become a hollow cylinder. As we shall see, Algw are by no means excluded from the high marsh, but undoubtedly they are most abundantly produced at a lower level. They play an important part both mechanically as mud-binders, and, later, as manurial agents when they are washed up with the drift. Between the two types of marsh no hard-and-fast line exists, for low marsh is continually in process of transformation into high by accretion of mud and the entry of other species of plants. At the same time the converse process is in operation, and high marsh gives place to low as a result of undercutting. This process is aggravated when from any cause, such as the disappearance of a protecting point of sand or shingle, some part of the marsh becomes exposed to increased scour by the sea. Under these altered conditions areas of high marsh may be rapidly degraded. In rare cases, as when shingle is washed to and fro on the actual surface, the tufty covering may be abraded to such an extent that the marsh suffers erosion super- ficially as well as by undercutting. However, increased local erosion is usually counterbalanced by increased accretion some- where else. A marsh is always able to assimilate much greater quantities of silt than are normally forthcoming. This power to accrete depends on the mud-holding faculty of the vegetation, and is dealt with more fully in a separate section at page 198. The question is sometimes asked whether in process of time the level of a salt marsh may not be raised so high by silting that the sea is automatically excluded; in other words, whether a marsh may not naturally reclaim itself? So far as we know salt marshes are never reclaimed unless the sea is banked off either artificially by the construction of sea-walls, or naturally by the throwing up of shingle beaches or sand dunes. Pro- vided the level of the land is not rising, the sea would never appear to abdicate the prerogative of undoing its own handi- work. Peculiarities of Salt-marsh Vegetation.—The plants which inhabit salt marshes belong to two great classes of plants, the Algze and the Spermophytes or higher plants. 170 PLANT WINNING OF TIDAL LANDS The Algz.—The normal vegetation of the sea consists of the seaweeds or Algz, of which there are some 770 species on the coasts of Britain.! These plants fall into four groups according to their colour—blue-green, green, brown, and red, and they occur in the greatest profusion where a rocky shore provides a firm substratum for attachment. The majority of Algz, in contradistinction to land plants, have no need of an absorbing root to penetrate the ground in the case of attached forms; a disk or attachment sucker suffices to hold them to the rock, whilst the operation of absorption of water and dissolved salts is effected by the whole surface. The capacity of marine Algz to exist in sea water, which contains in solution nearly 3 per cent of common salt, is rendered possible by the high internal pressure of their sap. If, for example, freshwater Algee are transferred to sea water, they undergo collapse and disorganization, because the relatively high concentration of the sea water brings about the outflow of the water of the cell sap of the Algz. The higher concentrations normal to seaweeds, however, render them immune from this danger. Salt marshes and other aggregations of coastal detritus are physically unsuited to the requirements of most seaweeds. The great majority of such as are met with occur attached to the shells of mussels, which afford a firm anchorage. A few occur on pebbles in sheltered positions, but in the case of Alge attaining any considerable dimensions the pebbles are liable to be drifted up to high-water mark, which is a position not usually suitable for most Alge. A certain number of Algz, however, have fitted themselves for existence on muddy shores, and these, though specifically few, occupy a great expanse of ground. Biologically, it is convenient to distinguish two groups: (1) those that merely cling to the surface of the mud; (2) those that penetrate into the mud, becoming, as it were, part of its fabric. Of the surface dwellers the most conspicuous are Entero- morpha, Rhizoclonium, and Ulva. Enteromorpha forms tiny ribbons which may expand into hollow tubes. It occurs on low marsh reaching down to the 1 We are indebted to Mr. A. D. Cotton of Kew for this estimate. ULVA AND RHIZOCLONIUM 171 low-water mark of the larger channels. The young plants are attached at one end to the soil particles, but as soon as they attain visible dimensions they are drifted to higher levels by the tide. Vast quantities of Enteromorpha are thus continually produced at lower levels, and make their way eventually to the drift line, generally rolled by the tide into ropes. Here they disintegrate into humus, and contribute to the maintenance of other plants in the way already described (cf. p. 111). Rhizoclonium is a filamentous Alga found especially on the wetter parts of high marsh. In winter and spring it grows with the greatest luxuriance, and is of great importance in covering and anchoring the seed of the spermophytes of the salt marsh. The annual plants in particular derive an evident advantage from their algal nurse. Ulva latissima deserves mention here on account of the nuisance caused by its putrefaction on certain foreshores. This Alga has a thin, membranous, expanded thallus of variable size, often reaching 1 foot in length and 4 to 6 inches in width. To stones or rock it is fixed by its attachment disk, but on the sheltered, muddy foreshores of estuaries, where extensive mussel beds are present, Ulva may occur in vast quantities attached to the byssoid threads excreted by the mussels. These threads form a very favourable mechanism for the purpose, and in brackish estuarial waters contaminated by sewage, such as Belfast Lough, where mussels are widely distributed, the Alga flourishes with the greatest luxuriance between half-tide level and low-water mark. The ammonia from the sewage promotes the rapid growth of the Ulva, especially during the summer months, whilst the extensive mussel beds provide the necessary anchorage. When in autumn the Alga becomes detached from its moor- ings it is heaped up in banks on the shore; it undergoes putre- faction, and by the evolution of sulphuretted hydrogen creates at times an intolerable nuisance. Experiments on a fairly large scale show that the nuisance can best be mitigated by the 1 See in particular Royal Commission on Sewage Disposal, 7th Report, Vol. II, Appendices, pt. i, r91x. For the botanical report on Ulva in relation to this nuisance, by Mr. A. D. Cotton, see ibid., pp. 121-42. 172 PLANT WINNING OF TIDAL LANDS removal of the mussels, or by their destruction zm s¢tu by the application of copper sulphate. The most important of the bedded-in Algae are Fucus vesiculosus, form limicola, Vaucheria Thuretii, and Microcoleus chthonoplastes, each of which deserves a word of description. Fucus vesiculosus limicola is really a form of the common Bladder-wrack seaweed (/. vesiculosus), which occurs on every rocky shore. It appears to originate from the parent type in a purely vegetative manner, and assumes its remarkable growth habit in response to the special marsh conditions. Fucus fimicola occurs on the upper 3 feet of the low marsh, the Fig. 42.—Fucus vesiculosus, form limicola, bedded in mud and proliferating to the surface. (After Dr. Sarah Baker.) upper limit of its range being at or slightly above the high- water mark of the neap tides. It occurs in part on bare mud (as in Plate XV, lower photo.), and also mingled with the pioneer colonists of the high marsh. It is distinguished by the narrow segments of its frond, by its sterility, and especially by the liability of the segments to be spirally coiled. Lying prone on the surface it becomes embedded in the mud, through which, however, it always pushes up numerous branches (fig. 42). Within the limits of its zone the plant carries on in this vege- tative fashion, the parts that become embedded undergoing decomposition and enriching the soil. As level rises and other plants come in it assumes the secondary réle of undergrowth; eventually it is crowded out by taller plants. In the history of marsh development Fucus limicola plays an important part in catching and holding silt, and also in the enrichment of the soil. Plate 3 Photo, E. J. Sansbury Sun-cracked Mud with the \lga JWécrocolews chthonoplastes ; Seed- lings of Swed maritima arising in the cracks Photo. supphed by Dr. 5. M. Baker Mud Slope covered with “cus dimicola; Aster and Salicornia are beginning to settle (Mersea Island, L’ssex) ALG, AS PIOSEERA ON AUD VAUCHERIA AND MICROCOLEUS 173 Vaucheria Thuretit is a green filamentous Alga and Micro- coleus chthonoplastes a blue-green. Otherwise they play closely similar réles in mud-fixing, the Vaucheria on low marsh, Micro- coleus over a wider range—from ordinary low-water mark to ordinary high-tide level. The embedded portions form a close meshwork of mucilaginous consistency, which holds the mud so tenaciously that practically none of it is washed out even when the surface layer is rubbed between the finger and thumb under a tap of water. The ends of the algal tubules project above the surface as a short-piled velvet, and trap any silt that the tide drifts along. These two Algze between them occupy extensive surfaces otherwise bare, and within the limits of their zones are most efficient catchers and holders of mud. Microcoleus sometimes does its work so well that the surface cake is impenetrable to germinating seedlings. However, in dry weather the cake is apt to crack in hexagonal fissures, and seeds, finding their way into these fissures, germinate and establish under the most favourable conditions. (Plate XV, upper photo., seedlings of Suceda maritima are arising in this fashion in the cracks of Microcoleus-covered ground.) The relation of almost all plants to the silting process is fundamentally the same as these two Alge. The portions of the plants which project above the surface tend to slow down the rate of flow of the layers of water that pass over them, with the result that the silt in course of transport is dropped and becomes entangled. The plant continues its growth through the new surface, and the process is resumed. The principle is just the same when Marram grass catches wind-borne sand, or Sueda fruticosa shingle from a passing wave. It is the eternal tendency of plants to stabilize the ground they occupy and to detain such fresh particles as enter their net. The Higher Plants.—These are technically called ‘‘ Halo- phytes”, to distinguish them from the ordinary terrestrial and freshwater flowering plants.1. Numerically, the halophytes form not more than 14 per cent of the total flora. Higher plants 1 The term ‘“‘halophytes” is used to designate plants that grow rooted in soils impregnated with salts. Strictly, marine Algae are excluded, though it is evident the two groups have in common their relation to a saline environment. 174 PLANT WINNING OF TIDAL LANDS number about 2000 species in the British flora, and of these not more than 30 occur between tide limits, some 20 only being really common. Though the species that occur on salt marshes are thus in point of numbers markedly inferior to those of the sand dune and shingle beach, they carpet the ground more densely. It is hardly necessary to explain that these plants are able to thrive in saline habitats in virtue of the high sap concentrations which they oppose to the sea water, concentrations which are found to vary according to the degree of salinity of the ground. Sea water contains approximately 3 per cent of common salt, but during dry periods between the spring tides the soil water may undergo concentration, reaching a strength of even 6 per cent NaCl. On the other hand, if heavy rains follow the spring- tide cycle much of the salt will be washed out (especially where much sand is present), and the concentration may fall to 1 per cent NaCl. It was proved by T. G. Hill that halophytes are able to accommodate their sap concentrations to the rise and fall of salinity in the environment, and that these adjustments are even rapidly effected. Probably all plants show these adjust- ments within limits; what characterizes the halophytes being the high upward extension of which they are capable. A great feature of most halophytes is their succulence, a character they tend to lose when grown in ordinary soil. For the most part halophytes of the salt marsh are smooth and succulent, but this is not invariable, as the Sea Purslane (Odzone portulacoides) is covered with scurfy, and the Sea Wormwood (Artemisia mari- tima) with woolly hairs. In Appendix IV, p. 267, a fairly full list of British salt-marsh halophytes is given, with the addition of the restricted number of families to which they belong. The most important of these families is that of the Chenopodiacez, a family always repre- sented wherever plants of the salt marsh or other saline soils occur. Next in importance come the Grasses, Crucifers, the Plantaginacez, and the Plumbaginacee. A few of these plants demand special mention from their importance in various ways. The occurrence of these plants, as with the Alga, is zonal, that is to say, each has a definite and restricted vertical distribution SALICORNIA 175 in its locality. Probably no other plants are so defined in their positions as are the halophytes. Salicornia annua is the staple plant of the earlier phases of salt-marsh development and especially of low marsh (fig. 40, p. 168). In young high marsh S. annua often occurs densely crowded in almost pure formation. Later on it is largely super- seded by other plants, except on the barer places. It is renewed each year from seed, and dies in the autumn. S. dolichostachya, closely related to S. annua, has long, tapering flowér spikes. This species is preferred for pickling as ‘‘ Sam- phire” on the east coast, as at Blakeney (Plate XXV, 1, p. 232). Fig. 43.—Obrone portulacotdes; a young trailing specimen, } nat. size Salicornia ramosissima plays the same part as S. annua in other localities. There are several other annual species of Salicornia in Britain, but of less importance than the foregoing. Salicornia radicans is a perennial species rooting from the procumbent shoots. In sandy salt marshes it is important as a hummock builder (cf. p. 189), and is apt to persist for many years. Obtone portulacoides follows Salicornia annua when the latter has raised the level of the marsh appreciably by silting. It forms a low, grey, straggling bush about 1 foot high, and characteristically occupies the banks of the creeks. In sandy marshes it often raises the height of the banks by filtering off the sand as the tide overflows them (Plate XVI, 1). Occa- 176 PLANT WINNING OF TIDAL LANDS sionally Obione overruns a whole marsh, and in virtue of its size and density obliterates the other plants (Plate XVI, 2). It is a perennial, and its prostrated branches root from the nodes the second spring. The branches being brittle become detached easily, and are apt to lodge and root elsewhere. Seedlings are also formed, but appear in quantity only in occasional years. The reason for its rather striking preference for the banks of creeks has not been ascertained. This plant contributes much material to the tidal drift; its ash is rich in potash. A trailing specimen is represented in fig. 43. Grasses.—The most widely distributed of all salt-marsh grasses is Glyceria maritima. On Salicornia marshes it follows the pioneer, gradually establishing a turf. It forms the general matrix of most high marsh, and is of value for grazing in the later phases. The closeness of its texture and its capacity to grow through make it a most efficient accretor of silt (Plate XIV, p. 166). On sandy marshes it often occurs as a pioneer forming hummocks. Here, and on other surfaces which it covers, it arrests the silt and continues its peripheral growth. Festuca ovina v. rubra is another grass found on the higher levels of the salting, and especially on banks and beaches liable to occasional tidal inundation. It has great value in holding the ground; also for pasture. Triticum pungens likewise occurs on the higher levels, and is perfectly halophytic. Spartina Townsendit is a grass of particular importance, and claims the attention of all who are interested in the utilization of salt marshes. Being of recent apparition, and its poten- tialities not yet fully gauged, we deal with it here at some little length. The existence of this plant first attracted general atten- tion when Lord Montagu of Beaulieu reported on its occurrence in 1907 to the Royal Commission on Coast Erosion.1 Having property on the Solent between the Beaulieu River and Lymington, Lord Montagu had witnessed the early coloniza- tion and gradual spread of Spartina Townsendi (known locally as ‘‘Rice Grass”) over the tidal flats till it had come to occupy 1 Royal Commission on Coast Erosion and the Reclamation of Tidal Lands, Minutes of Evidence, Vol. I, rr2g0-300, 11341-62. Plate NVI aay Photo. Dr. S. Hastings Small Creek bordered by Obione, which has raised banks by trapping the silt (Bouche d'Terquy) al ea Ne Ys Photo. Mrs. Cowles Mixed Salting invaded by Obione, which has overrun the flat, all but the strip intersected by the seated figure. The bushes on the bank are Sveda fruticosa (Blakeney Point) OBIONE PORTULACOIDES HISTORY OF SPARTINA 177 thousands of acres, and was consolidating and building up the ground. The appearance of this plant was a comparatively recent phenomenon, and its spread was still in active progress. The matter was at once referred by the Commission to the authorities of the Royal Gardens, Kew, for more information, and Dr. Otto Stapf took up the enquiry from the botanical and topographical points of view.! The description which follows is based largely on Dr. Stapf’s account. Of the small group of species which constitutes the genus Spartina, most are natives of the Atlantic coast of America. One species, Spartina stricta, is indigenous to Europe, occur- ring in salt marshes from the Wash to the Mediterranean. A second species, Spartina alternifiora, of American origin, has been established in Southampton Water for a hundred years, no doubt accidentally introduced. The first record of Spartina Townsend, the species which claims our attention, was at Hythe, on Southampton Water, in 1870. Twenty years later it was spreading rapidly, and it now occupies enormous areas in the waters around Southampton and the Isle of Wight. In 1899 a few plants were detected in Poole Harbour, and these are still spreading everywhere over its intricate system of creeks and mud flats. To the east it has spread in the same way to Chichester Harbour, whilst latterly it has found its way to the estuaries of the Rivers Saire and Vire, which discharge on the eastern side of the Cherbourg Peninsula. Spartina Townsendit ‘is a vigorous, stout, stiff grass, stand- ing usually about 2 to 2} feet high, but occasionally much dwarfed, or drawn out, and then attaining a height of from 3 to 4 feet. It grows mainly in the soft ground of the mud flats, which are so common on the Hampshire coast and the adjoining portions of the coasts of Dorset and Sussex, and in the tidal reaches of their rivers. It anchors itself in the mud by long, vertically-descending roots, whilst another set of roots, 1 See Dr. Stapf’s Evidence before the Royal Commission on Coast Eroston, Vol. I, 16284-381. Also Stapf in Gardener's Chronicle, Jan. 18, 1908, p. 33, and Proc. Bournemouth Nat. Sct. Soc., Vol. V, p. 76,1913. Also R. V. Sherring, #did., Vol. IV, p. 49; Vol. V, p. 48; and Vol. VII, p. 42. Mr. Sherring’s notes form a most valuable record of the gradual spread of the plant in Poole Harbour. It is to be hoped that later on it may be possible for them to be thrown together into a continuous narrative. (0924) 138 178 PLANT WINNING OF TIDAL LANDS short but abundantly divided and interlaced, spreads all round from the base of the stems and the nodes of stolons close to the surface of the mud (fig. 44). It grows in tufts (Plate XVII. See frontispiece), which often assume great dimen- sions and a remarkably circular shape. Such patches may measure anything between 3 and 15 feet in diameter, and even more. The grass owes this peculiar growth to the production of numerous underground branches or stolons, which grow out from the buried stem bases radially, and measure from a few inches to several feet. Inequality in the density of the mud, admixture of sand, pebbles, or larger stones, and other con- ditions may favour development in one or the other direction, when the circular shape of the clumps gives way to irregular shapes, or it may be that two or more clumps meet in the course of expansion and fuse, and finally many clumps may unite and form regular meadows with a dense matted growth. ‘The leaf-blades are rigid, long, and long-pointed, standing off at angles of 60 to 70 degrees, and bright green or slightly glaucous. Like all the Spartinas, it has the spikelets closely arranged in stiff, one-sided spikes, which spring from a common axis, and are erect, so that they are almost or quite applied to each other. There are usually four to seven of them, but starved specimens may have only two, and luxuriant specimens as many as eleven. ... The grass begins to flower in the latter part of July, and the flowering is most profuse in August and Sep- tember. Some individuals, however, lag much behind, and may be found in bloom as late as the end of December. As each spikelet contains only one flower, it also has only one grain, which remains tightly enclosed in its husks. ... The spikelets become easily detached when ripe, drop into the water, and leave the bare spindles standing up stiff like spears until they break down along with the stems, which gradually decay during the winter and spring. The ripening of the grain takes place mostly in October.” 4 As with many other seaside plants, the output of seed is rather uncertain, and appears to be influenced to a marked degree by the weather during the flowering season. Doubtless 10. Stapf, Proc. Bournemouth Nat, Sci. Soc., Vol. V, pp. 77-8. 179 SPARTINA TOWNSENDII Autunm condition, One-fifth nat. size Fig. 44.—Spartina Townsendiz, complete plant with stolons, long anchoring roots, and interlacing surface roots. 180 PLANT WINNING OF TIDAL LANDS the occurrence of bumper years accounts for the sudden inva- sion of new areas, for which the plant is famous, whilst in the following years the numerous seedlings thus established will expand into clumps, which eventually join to form extensive meadows. Dr. Stapf reports that filamentous green Alge are instrumental in anchoring the seeds to the mud, so that they remain and germinate—a process we have noted in the case of several other halophytes, e.g. Rhizoclonium, p. 171. Plate XVII (see frontispiece) shows an early and charac- teristic stage of colonization in Holes Bay, Poole Harbour,’ whilst the upper picture (Plate XVIII) was taken in the adjacent Lytchett Bay. In addition to Spartina Townsendit (marked Sp.), this photograph shows belts of Scirpus maritt- mus (Sc.), and Phragmites communis (P.) growing in the foreground. The latter plant is the familiar reed of freshwater rivers and lakes; on the salt marsh, however, it behaves asa halophyte, being perfectly tolerant of saline submersion. The lower picture on the same plate shows a tongue of meadowed Spartina advancing into an arm of Poole Harbour. The outstanding feature which makes Spartina Townsendit pre-eminent among the halophytes is the extraordinary vigour with which it spreads into new ground. The flats which it invades form the upper tidal zone, extending downwards some 4 to 6 feet from the high-water mark. This ground in the Southampton area consists mainly of soft mud flats, into which a man walking sinks knee-deep. It was formerly covered mainly by Zostera. Where the Spartina has united to form continuous meadow the ground gradually becomes firmer, and at places in Poole Harbour cattle walk down on to the marshes to browse on the plant. At present Spartina sweeps all before it in this zone, and is rapidly raising the level of the ground. Of course this cannot go on indefinitely. Judging by analogous cases, a time must come when the level has been raised to a height less favourable to Spartina than the present mud flats, and it will then be gradually ousted by other plants better adapted to the new conditions. At present, however, Spartina 1 Taken by Mr. R. V. Sherring, as also Plate XVIII, lower picture, to whom we are in- debted for the use of the photographs. Prte NVI Spartina Townsendti (Sp.), Scirpus maritimus (Se.), and Phragmites communis (P.) growing together in Lytchett Bay, Poole Harbour A dense tongue of Spartina advancing into an arm of Poole I]arbour SPARTINA TOWNSEND SPARTINA AND NAVIGATION 181 is in the phase of youth, and it is too early to say with certainty by what plant or plants its place will be taken. Experimental cultivations have already been made in the Medway, in Somerset, at Wells in Norfolk, on the Firth of Forth, and in New Zealand. As the plant has established satisfactorily in these various stations, it is evident that it tolerates a wide range of conditions. Of its capacities as a natural reclaimer much has still to be learnt; in fact, Spartina has as yet hardly begun to be exploited. In due time, no doubt, some ‘agency will be established for its export to distant coun- tries, a desideratum in view of its capriciousness in seed produc- tion. It is necessary that experts should be ready on the spot to take advantage of another bumper harvest like that of 1911. The effect of Spartina Townsendit upon navigation only time can show. Not that there is any fear of its occupying and block- ing navigable channels, for Spartina operates in a higher zone. But the presence of a plant which invades the mud flats, and promises to raise their level to a marked extent, must encroach by just so much on the space formerly accessible to tidal waters. In other words, after Spartina has done its work, less water will flow up the channels than was formerly the case, and less will flow down again. Should this mean a deficiency of scour on the ebb, there is a likelihood of the channels silting up, as has happened in many other cases. As the natural reclama- tion of many square miles of marsh land would ill compensate for impaired facilities of navigation, it behoves the appropriate authorities to use great vigilance. Carefully planned observa- tions at the present time, or in the near future, should be capable of detecting what may be the trend in this matter, and if trouble is brewing, steps could be taken to restrict or eradicate the Spar- tina, e.g. by gas poisoning or other chemical agencies. We are referring, of course, to Southampton Water and Poole Harbour. Curious as it may appear, the colonization of the mud flats of Poole Harbour is reported to be accompanied at first by an appreciable deepening of the creeks and channels. This effect is probably due to the fact that the travelling silt of the creeks, which formerly moved up and down with the flow and ebb of the tide, is now fixed on the mud flats by the Spartina—the 182 PLANT WINNING OF TIDAL LANDS creeks being to this extent depleted of mud and deepened. It would be a serious error, however, to suppose that this effect will continue. As the Spartina flats rise by silting, the storage space for tidal water will undergo a corresponding diminution, and the volume of water available to scour out the channels at the ebb will grow less. If we assume that through the agency of Spartina the mud flats rise only 1 foot, and that the area of Poole Harbour involved is 10 square miles, this amount of accretion will diminish the capacity of the harbour to accom- modate tidal water to the extent of about ten million cubic yards—in other words, there will be this deficiency in the volume of the ebb for the purpose of scouring the channels. The Origin of Spartina Townsendit.—Nothing is certainly known on this point except that its appearance was first re- corded near Southampton in 1870. At that time the two other species, S. stricta and S. alterniflora, existed together on the area, and as S. Zownsendit is in many respects intermediate in its structural characters, it has been pretty generally assumed to be a cross or hybrid between the two.? This view finds strong corroboration in the fact that at the only other spot in the world where these two species are known to overlap in their distribution, viz. the mouth of the Bidassoa River, south of Bayonne, in the Bay of Biscay, a form of Spartina closely similar to S. Zownsendit was found in 1895. This form, which was named S. Veyrauti, is regarded by experts as a naturally-produced hybrid of S. stricta and S. alterniflora. All that can be said is that the coincidence is remarkable, and that the inference that both S. Zownsendit and S. Neyrautit are hybrid forms, derived from the same pair of species, is almost irresistible. The matter can only be settled by breeding experi- ments in competent hands. To recapitulate so far as Spartina Townsendiz is concerned. This plant appeared for the first time in Southampton Water nearly fifty years ago. Since that date, owing to its remarkable constitutional vigour, and suited by the ground, it has spread in a miraculous way on the mud flats of the Southampton system and in adjacent estuaries to east and west so as to threaten 10, Stapf, Proc. Bournemouth Nat, Sci. Soc., Vol. V, p. 81. USES OF SPARTINA 183 entirely to cover them with dense continuous meadows. At the same time, by its accreting action the level of these flats is being raised and their consistence consolidated. The area occupied is already to be measured by thousands of acres, and the only limit to its future spread is the extent of suitable ground available. In 1907 attention was directed to the phenomenon by Lord Mon- tagu’s evidence before the Royal Commission on Coast Erosion, and since that date the plant has been kept under observation. At the same time, serious attempts on a proper scale have yet to be made to determine the economic value of this remark- able plant—whether it can be employed profitably, and under what conditions, for forage, litter, hay-making, or the manu- facture of paper, in addition to the provision of means for its distribution as a reclaiming agent. Moreover, its marked in- crease in navigable waters raises the question whether its spread in some of the localities already occupied may not develop into a serious menace. These are all matters that should long since have received close attention from an authority in a position to take action. Were our coast-line properly supervised there should be no fear of such a matter being overlooked. Occasional isolated cases of the employment of Spartina in accretion and coast defence are on record. The Californian town of Reclamation is stated to be laid out on ground built up from the sea by Spartina glabra, whilst on the Demerara River (British Guiana) another species, Spartina brasiliensts, has been employed in an ingenious way by Mr. John Junor, the manager of certain estates in the district. The method consists in planting the foreshore with Spartina, and when it has become established and collected soil, Man- groves (Rhizophora) are planted amongst it, with the result that a forest springs up and no further attention is required. The details are as follows :1— “Mr. Junor informs me that he plants the tufts of the grass (Spartina brasiliensts) in rows, the rows being six feet apart, and the plants in the rows separated by a distance of two feet. The depth at which the tufts are planted 1 The account quoted was written by Mr. A. W. Bartlett in the Journal of the Board of: Agriculture of British Guiana, Vol. 1, No. 3, January, 1908. It is reprinted in Vol. IX of the same journal, July, 1916, pp. 180-2; the reprint alone has been seen by us. We are indebted to Mr. Alleyne Leechman for calling our attention to the matter. 184 PLANT WINNING OF TIDAL LANDS is about one foot below the surface. The grass spreads quickly, so that in a short time the plants meet to form a patch, the numerous stems of which serve to fix the mud and prevent it from being washed away by the sea. Even should the mud cover up the plants after they have been planted they are able to make their way through it in time.” ‘“When the grass is firmly established Mr. Junor’s plan is to plant the seedlings of the mangrove in amongst it. There follows a great development of roots both from the trunk and the branches of the mangrove, which, after the manner of flying buttresses, firmly support the tree in the soft mud and enable it to withstand the strongest breezes and the heaviest seas. These aerial roots being more or less curved allow a certain amount of ‘give’ or play, which is often of advantage in enabling a structure to withstand pressure without collapsing. So the mangrove tree is in many ways particularly adapted for growing along muddy sea coasts which are exposed to winds and waves. The young plants grow rapidly, and in a few years will them- selves produce a crop of seedlings. The club-shaped seedlings are obtainable in abundance along the coast, and should be gathered for planting when they are nearly ready to fall.1 All the planting that is required is merely to insert the lower pointed end of the seedling in the mud. When the mangrove trees have grown to a fair size they form a close shade, and so far as my observation goes they kill out the ‘wild rice’ (Spartina), which appears to require full exposure of the sun’s rays for at least a part of the daytime for its successful growth. But by the time that the mangrove trees have reached a sufficiently large size to do this, they will themselves have taken over the functions of the ‘wild rice’ in preventing coast erosion, and hence the latter is no longer required.” Other Perennial Halophytes.—This short review of the plants of the salt marsh may conclude with some mention of a number of common perennials, most or all of which are to be met with on nearly every marsh. They include the following species :— Sea Pink or Thrift (Avmeria maritima) (fig. 45), Sea Lavender (Statice Limontum), Sea Plantain (Plantago maritima), Sea Arrow Grass (Zriglochin maritimum), Sea Aster (Aster Tri- polium), Sea Spurrey (Spergularia media). In their typical occurrence all these plants first appear as seedlings relatively early in salt-marsh development, some even when the marsh is still in the Salicornia phase. As the level of the surface rises by accretion, the individuals already established persist, whilst new ones continue to establish, at any rate for a time. In this way the pioneer phase, in which annual Salicornias and perhaps 1 One of tbe peculiarities of Rhizophora is its vivipary, ie. its seeds germinate whilst still attached to the parent plant. ROSETTE PLANTS 185 Suaeda maritima play a chief part, gives place to a secondary phase or ‘‘succession” in which the ground is mainly held by perennials, of which the above-named, along with the ubi- quitous grass Glyceria maritima, are examples. The whole of these forms are rosette-plants, that is to say, the foliage is produced in tufts at the surface of the ground. Branches rising above the surface only occur in connection with flowering, and the inflorescence axes so produced (whether leafy, ~~ No Se SSeS BeOS Fig. 45.—Armeria maritima, a typical perennial halophyte with rosette-like habit. § nat. size as in Aster, or otherwise) are non-permanent structures. As the surface slowly rises, these plants hold their place by pro- ducing their successive rosettes of leaves at slightly higher levels. Commonly this adjustment to changing level coincides with branching of the original crown, so that the area occupied by the plant undergoes peripheral expansion (cf. fig. 45). In this manner numerous perennials will be brought into strenuous competition with one another for the limited space available, and it is to be expected that sometimes one species and sometimes another will prove successful in the struggle, according as one or other is favoured by the particular con- ditions of the habitat. Though the elements of the struggle have yet to be ascertained, it is probable that such types of high 186 PLANT WINNING OF TIDAL LANDS marsh as consist predominantly of Armeria (as on the Dovey estuary in Wales and elsewhere), or of Statice (as is so frequently the case in East Anglia), are examples of a survival of the fittest under the given conditions. At the same time, however, it has to be borne in mind that a like result (i.e. a relatively pure sward of a given species of plant) may in some cases arise in the absence of competition, when other plants for any reason are unable to establish, or when their seeds fail to invade the particular area. Spergularia media differs somewhat in habit from the other species enumerated in that the cylindrical fleshy leaves are borne in whorls on spreading, straggling axes which arise from the summit of the subterranean rhizome. As these axes become bedded in, they in turn originate fresh branches in the same manner. The Reproductive Methods of Salt-marsh Plants.—The annual plants, of which the Salicornias (S. annua, S. ramostis- stma) and Sueda maritima are the best examples, depend for their power of holding their place upon their huge seed output. When these plants die in autumn the seeds fall in the mud and become anchored by the filamentous Algz (Rhizoclonium, &c.). Under cover of these they germinate in early spring, coming up in beds, thick like mustard and cress. Germination under this protection is considerably earlier and under more favourable conditions than on bare mud. Thermometers placed beneath the algal network on a cold day in March showed a mean excess of 2° C. over the temperatures given by simultaneous readings from other thermometers similarly placed, except that the algz had been cleared away. By no means the whole of the seeds are thus entrapped; many drift and are carried to a variety of situations. Thus if slabs of the soft, bare mud of creek bottoms be removed and placed under appropriate conditions, seedlings will often appear (Suzeda, Salicornia), which under ordinary circumstances hardly ever establish on account of the high mobility of the mud. These annuals are able to hold their own year after year even when embedded in a turfy matrix of the Salt-marsh Grass (Glycerta maritima). This they appear to do in virtue of their REPRODUCTIVE METHODS 187 power of early germination, by which the root zone of the turf is penetrated before the grass has aroused itself from its winter anesthesia. In this connection the circumstances under which annual plants are sometimes able to carry on in non-maritime turf would probably repay investigation. The halophytes other than annuals, whilst showing the highest capacity to hold their own and spread by vegetative means, are all of them, so far as our investigations go, satisfac- tory producers of seed. At the same time, in not a few cases, seed output tends to be concentrated in bumper years separated by series of years of low or moderate production. The cases of Suaeda fruticosa (p. 116) and of Spartina Townsendit (p. 180) have already been referred to. Another case in point is Obzone portulacoides, of which for years no seedlings can be found in particular localities, and then comes a year in which tons of fruits accumulate everywhere in the drift and seedlings are most abundant. Another well-ascertained case of a plant liable to bumper years is Statice binervosa. It is probable that the bumper years are accountable for the spread of these plants into fresh localities (cf. the case of Spartina Townsendi, p. 180), whilst the strongly-marked vegetative methods permit the newly-established seedlings to expand into tufts or clusters and thoroughly occupy the ground. The halophytes thus afford an example of the way in which the versatility of the life histories of the individuals enables them to invade and establish in new terrain, and then to occupy it in the most exclusive manner. It is not to be doubted that analogous relations are also to be found in the case of ordinary terrestrial plants. The Developmental Phases of the Salt Marsh.—Whilst the individuals which collectively make up any natural vegeta- tion are inevitably liable to change, those of the salt-marsh covering fluctuate to a pre-eminent degree. The pioneer plants, whether of a mud flat or of a sand-bank, endure only for a limited period, and as the conditions change the ground becomes suit- able for the entry of other species which replace the pioneers, and in their turn are superseded by yet others. A vegetation thus undergoes progressive development, passing through a series of definite phases termed ‘‘successions”, which lead to 188 PLANT WINNING OF TIDAL LANDS a terminal succession, technically known as the “climax” vege- tation. This is commonly the last and most enduring phase. On the salt marsh such terminal successions include the Glyceria and Armeria swards, the Statice marsh, the Juncus belt, and doubtless others. The detailed history of development has been followed only in a few cases, and even in these we are for the most part ignorant of the causes which determine the several successions. Attention is only just beginning to be directed to the intensive study of the habitat, and little more has come to hand than the names of the species and the order in which they supplant one another in a certain number of instances. In the case of the salt marsh we know that these changes are accompanied by a rise in level, and this of course must mean increased drainage and a less amount of tidal immersion. These alone are factors which will react favourably on certain plants and unfavourably on others—plants being on the whole rather exacting in their water requirements. Whether, how- ever, such changes are by themselves decisive, or whether, on the other hand, plants may not produce in the soil toxic bodies prejudicial to themselves, and thus indirectly favourable to the advent of the next succession, must remain for the present an open question (cf. pp. 63, 64). The developmental sequence of a salt marsh is not necessarily obvious at a glance. Quite possibly the area visible from a given point is all in the same phase of development, i.e. is all in the same succession. The only chance in a case like this is the possibility that the remains of previous vegetations may be preserved below the surface still in a recognizable state—as frequently happens in peat bogs. Generally, however, different parts of the marsh are in different phases, and if these are present in sufficient numbers it will be possible, by listing the constituent plants, to arrange the phases in their order. All that is necessary then is to be certain as to which is the relatively initial and which the relatively final phase. In a marsh undergoing local erosion by undercutting with a migration of its creeks, much of the eroded material is apt to be deposited as a bank on the following side of the creek whilst the advancing side carries on. If the creek continue for some HUMMOCK DEVELOPMENT 189 years advancing in the same direction, a series of banks are left in succession, side by side, that nearest the creek being the youngest. These banks commonly become recolonized by vegetation, and by comparing the vegetations of a series a close approximation is obtained of the various successions through which the marsh as a whole has passed. It was partly in this way, and partly by comparing the changes in the vegetation of the individual banks over a period of six years, that the broad outlines of marsh development in the salt marsh at the Bouche d’Erquy in Brittany were elucidated. As the case is typical of the sandy type of salt marsh, and the history of the colonization of a single sand-bank provides an epitome of the colonization of the whole marsh, a short illus- trated account will not be out of place here. Colonization of Sand-banks in the Bouche d’Erquy.—1rst Phase.—Banks of sand are deposited near points in certain creeks where the bank is being eroded by the meandering of the creek. The sand-bank illustrated here was oval in form, 20 feet wide at the broadest point, and 40-50 feet long. The position was such that the sand-bank was not covered at the lower neap tides. All the spring tides covered it, the highest ones with at least 6 feet of water. The flow of the water in the creek often reached a velocity of 3 to 34 miles an hour. The first flowering plants to appear on the bank were a scattering of two species of Salicornia, viz. the annual species, S. ramosissima, and the perennial, S. radicans. These plants on establishment at once accrete hummocks of sand, in much the same way as a Psamma tuft accretes an embryo dune (cf. p. 60); with this difference, that here water is the agent of trans- port whilst in the case of the dune it is wind. By August the hummock-forming plants have attained their maximum growth for the season, and the hummocks will likewise be at full size. On the approach of winter the plants of Salicornia ramostssima die, their skeletons remain in place till the following spring, and serve to shelter the hummocks that have accreted around them. Ultimately these plants disintegrate and weather, and their hummocks, no longer sheltered by an organic nucleus, are dispersed. Other seedlings of the same species establish 190 PLANT WINNING OF TIDAL LANDS each spring at other points on the sand-bank, but from the nature of the case their hummocks are ephemeral, and make no conspicuous permanent contribution to the relief of the marsh. The Salicornia radicans hummocks behave quite differently. After the winter rest the plant increases in size, and the hum- mock undergoes a corresponding extension. It is characteristic of S. radicans in this position that it not only grows in height but also spreads laterally to form a belt placed at right angles to the flow of the current (cf. the black bands in fig. 46, a). The result is that the hummocks show marked expansion. At this stage they are pyramidal in form, 8 inches to 1 foot in height, and rest on a kite-shaped base, occasionally reaching 7 feet in length and 4 feet in width (Plate XIX, 2). These S. radicans hummocks are the fundamental units from which the future relief of the salt marsh is built up. Sand-banks may remain bare for a number of years, or they may undergo primary colonization almost at once, according to the facilities for the bringing and attachment of seeds. The presence on the sand-bank of a plexus of the alga Rhizoclonium is an essential factor in anchoring the seed and sheltering the seedlings in the early stages. 2nd Phase.—The beginning of this is marked by the colon- ization of the hummocks by other species of halophytes. By far the most important of these is the grass Glyceria maritima, but Suceda maritima, Obione portulacotdes, &c., settle in at the same time. The hummocks, which are at first vegetated in patches (as in fig. 46, a), become entirely clothed with vigorous turf in the course of one or two seasons (fig. 46, B and c), and as an immediate consequence expand in all directions by the incorporation of particles of sand between the shoots and leaves of the plants. This expansion, which continues as long as the hummocks are fed with sand by the flowing tide, leads to adjacent hummocks coalescing to form continuous turfy hum- mock systems (as in fig. 46, C), which are added to the general sward of the marsh as the creek abandons the original sand-bank in its further meandering. Two stages of the area charted are shown in the photographs Plate NIN Part of Bank charted in fig. 46 photographed three years before Chart 46.\ was made ; it shows the earliest phase of colonization by Sadicornia radécans, which in places has already orientated itself transversely to the current Well-developed hummocks in phase 1 (ef. fig. 46A) with their belts of S. radicans. The white wisps consist of bleached Zostera leaves entangled from the drift HUMMOCK DEVELOPMENT (BOUCHE D'ERQUY, BRITTANY) 1gl HUMMOCK DEVELOPMENT tobr/t aTeIG “I “XTX 23e][q Ul UMOYsS st Base ayy jo a3¥3s Jala Uy ‘We217s sUMOP quIod SMOIIE BYT, “Jaad] fes1aUVT 2q3 VAOge 400} 1 ynogeE 03 asis SYDOMUINY ysaTIE] OY} JO SyWUINS >YT “payzIWo a1e O pue g UF S}s1N0;0D Teuorses9Q) ‘syDOWWNY yUa}sSISJod-uoU ‘TTeUIS YIM SEIUIOOITeS feNnuUe ase a PUE V UI SaHOIYS [BOQIaA = "HL499A7H ‘seaIE payOp !suvIpH4 vI1LL0I 3170S 'SIPQ Wig ‘wwurpepUe vr4vI247H Aq sysowumny asay} jo uoIyezIUCjOD yuaNbasqns 9y} pue ‘suv2pv4 vI~WL0I217VS Aq YUEQ-puES a1eq EB UO uonEWs0y yOOUWINY AOYs 07 6061 pue ‘go6r ‘Lo6r si¥a4 |aissaz0ns 943 UI paAeaans asenbs j00j-Sz aures jo seYD Teag—"o pur ‘a ty ‘oh 31g 26 93y3A09- aunt Y4n, ve 192 PLANT WINNING OF TIDAL LANDS on Plate XIX. The upper picture shows the hummocks begin- ning in 1903, the lower a detail of a later phase corresponding to fig. 46, a (1907). In many cases the original sand-banks remain separated by low depressions which often retain water after the tide has ebbed. Where growth has been very regular, and the original sand-banks were laid down side by side to form a point of land following the advance of the creek, the depressions are curved and parallel, and when filled with water at once betray the origin of the relief. (Cf. the three advancing points, Plate XVI, 1, p. 176.) In the later stages of this grass-hummock phase two ant- agonistic tendencies are manifest. The ground colonized being undulating and hummocky, there will be certain lines which the tide will follow invariably as it swills over on to the marsh from the larger creeks. These natural irrigation lines take the form of shallow channels, a few inches wide, generally bordered at Erquy by a bright-green form of Salicornia ramosissima. Now water flowing along defined lines over undulating terrain will exhibit the phenomena appropriate to stream flow, and will tend to undercut the banks, and to bring about a migration of its channels. At the same time the exuberant vegetation as a whole will conflict with this tendency, and where the cutting power of the water is small will often obliterate the channel altogether. The channels thus tend to become discontinuous, the surviving portions taking the form of chains of ‘‘ pans”. These pans are depressions largely bare of vegetation and having no outlet; the water circulates in eddies as they fill, so that pans are apt to widen or enlarge irregularly. In the aggregate quite an appreciable area of the marsh may be occu- pied by pans. The above much-abbreviated account of the development of a sandy salt marsh should suffice to show that the process is a complex and continuous one, and that all the stages are closely interrelated. Apart from the interest which attaches to any related series of natural phenomena, the matter has a bearing on the exploitation of the salt marsh. Thus, when bare 1Cf. R. H. Yapp and others, ‘‘ The Salt Marshes of the Dovey Estuary”, Journal of Ecology, Vol. V, p. 65, 1917. Pinte SN Artificial inoculation of Sadicornia radicans on a bare sand-bank; hummocks beginning Cart-tracks colonized by Salicornia and Sv@da maritima BOUCHE D'ERQUY, BRITTANY ARTIFICIAL HUMMOCK PRODUCTION 193 sand-banks are deposited in the beds of channels, several years may elapse before seedlings of Salicornia radicans become established and the hummock stage is inaugurated. These interruptions can be avoided by planting S. radicans dug from some other part of the marsh. Such an experimental plantation on a sand-bank in the main channel of the estuary is shown at Plate XX (above), after the clumps had settled in. In due course hummocks wereformed, but this particular experiment was destined to be over- “6 s whelmed ultimately, owing to | * Pe flood water from the land after rain undercutting the ES 5 entire bank on which the ori- s " ginal plantation had been es- : tablished. In another creek CEA a similar plantation survived. fly The hummock system charted in fig. 47 arose in two years from the date of planting the . : * . . o123 45 sandbank with Salicornia radt- Ge Bebe ae ‘ cans, and is identical in all FEET T1909. respects with a naturally-pro- Fig. 47.—Chart of Salicornia radicans Hum- duced system of hummocks. mocks, showing beginning of secondary coloniza- Df tion two years after plantation made. Black The phenomena of these belts = S. radicans; G = Ghyceria maritima; sand-banks are constantly in fiasuemkack operation on the bare flats towards. the mouth of the estuary (Bouche d’Erquy), where the colonized and bare unstable areas abut. Roughly a zone some 10 feet wide of the latter is occupied each year by the pioneer plants. The chief obstacle to rapid colonization in this region is mobility of ground, for where this is overcome by accidental causes, colonization proceeds apace. Thus carts sometimes cross a corner of the marsh, on their way to and from a place in the dunes where sand is dug, and in the ruts so formed a vegetation springs up forthwith (Plate XX, below). The rut acts as a trap which catches the drifting seed, and the soil below the rut is consolidated by pressure so as to give the (0924) 14 194 PLANT WINNING OF TIDAL LANDS plants a foothold. A striking manifestation of this consolidation is sometimes to be seen at places where the uncompressed soil has weathered out, leaving the consolidated soi! beneath the rut as a ridge standing out in relief. By no means every sandy salt marsh is colonized quite in the manner described. Frequently the species of plants are not the same, though they play substantially the same parts. For instance, near Silverdale, in Morecambe Bay, and elsewhere, Glyceria maritima is the actual hummock- building pioneer (phase 1), and is followed by the grasses Lepturus filiformis, Agrostis alba v. maritima, and Festuca rubra v. prutnosa, together with Plantago and Armeria. (Cf. Appendix V, p. 269.) Muddy Salt Marshes.—There are different consistences of mud, and this character has a marked influence on the nature of the pioneer colonists. Soft mud and relatively hard mud, however, contrast with sand, in that they show little tendency to develop hummocks in the manner described in the preceding pages. The material does not collect rapidly at particular spots as in the case of sand. Where hummocks are a very prominent feature on mud, they are in part residual, i.e. have been ex- aggerated by the cutting away of the intervening ground. (See also p. 195.) Soft mud? is relatively more obstinate to colonization than firm mud—(r1) because it is not easy for many otherwise suitable species of plants to get a proper foothold; (2) because its water- logged state retards the diffusion of oxygen needed for the res- piration of the embedded parts of the plants. Consequently it is not surprising that the pioneers on soft mud are usually specialist plants capable of dealing with these peculiarities of the habitat. By means of creeping rhizomes rooting all along, they get a good hold of the ground, whilst, by the provision of an ample system of internal lacunz throughout the plant, the oxygen dissociated from carbon dioxide in the process of chlorophyll assimilation is able to diffuse readily to the embedded portions of the plant. The commonest pioneer on soft mud is the Grass-wrack 1 “Soft mud” may be defined roughly as mud into which the foot sinks ankle-deep or more; ‘firm mud”, not beyond the sole of the boot. COLONIZATION OF MUD 195 (Zostera marina and Z. nana), a curious plant with ribbon-like leaves and creeping rhizomes. The latter form a dense plexus, holding the plant in place in the mobile ground. Propagation is carried out freely by seed in the localities we have examined, and this is doubtless supplemented by fragments of rhizome broken loose in heavy weather. Zostera, which occupies the lowest zone of all phanerogamic halophytes in Britain, is re- markable in being one of the very few plants whose flowers are adapted to cross-pollination by the agency of water. When the mud has been sufficiently consolidated, Zostera may be followed by one of the annual species of Salicornia, e.g. Salicornia annua. WHenceforward the history of development follows substantially that described below for firm mud. Another plant which follows Zostera is Spartina Townsendtt, and we should not be surprised to hear that it could colonize soft mud even in the absence of this plant. It is adapted to the habitat both by its creeping rhizomes and by its ample lacune. The history of the spread of this remarkable grass in the Southampton region and its importance as a land builder have already been fully described (pp. 175-183). Another plant often colonizing soft mud is Scirpus maritimus (Plate XVIII, p. 180, marked Sc. in upper photo.). In some districts (e.g. Poole Harbour) it is cut for thatching. Firm mud, generally consolidated by the action of Alge, sooner or later will show a thin scattering of Salicornia (e.g. S. annua). In successive years this covering, renewed annually from seed, becomes more and more compact, until a pure sward of Marsh Samphire, the first ‘‘succession” of the series, is estab- lished. If the area be at all extensive the marsh will be irrigated by creeks, the original lines of which are frequently laid down in advance of the appearance of the vegetation covering. Where flats undissected by creeks and previously bare pro- duce rather suddenly stretches of Salicornia, the vegetated areas become appreciably convex by accretion within one or two years. The tidal waters running over such areas naturally follow the less densely vegetated and slightly lower regions between, which thus become the natural primitive creeks. In 196 PLANT WINNING OF TIDAL LANDS such cases the lines of irrigation are determined more by the accidents of colonization than by any special pre-existing features in the relief. On salt marshes where Fucoids (e.g. Fucus limicola) play an important part, these plants are especially conspicuous at the lower levels, and their occurrence synchronizes with the pre-Salicornia phase and persists into the Salicornia phase itself (Plate XV, p. 172, below). As the level rises and other halophytes come in, the Fucoids tend to disappear, or at best to survive only locally. During the period of their domin- ance, however, they are of great importance as accretors of silt (cf. p. 172). In due course the Salicornia phase gives place to the next succession, and this is by no means the same in all cases. It is possible also that the Aster is one of the plants liable to become prominent in salt marshes undergoing down-grade changes or retrogression, and if this be the case a certain difficulty will be found in determining the status of an Aster marsh when its previous history is unknown. Although the detailed study of plant assemblages is relatively recent, more attention has been given to their progressive development (i.e. first establishment to climax) than to their degeneration. Sometimes the history of a vegetation comes to an end suddenly by erosion, as when a marsh is undercut by a meandering creek, whilst in other cases a vegetation may slowly go back in its footsteps, with variations. It is these latter retrogressive phases, whether in salt marsh or other vegetation types, that have been so little studied, and which are liable, in the absence of more precise data, to be confounded with true ‘‘ successions”. In other cases, and this is the more typical history of muddy salt marshes, the Aster enters only in moderate degree, and is accompanied by a variety of halophytes, such as Plantago maritima, Spergularia media, Statice Limonium, Armeria, Tri- glochin, and Glyceria maritima. The last-named grass where present tends to form a plexus everywhere, and here, as in more sandy marshes, is a most important component. Under the sway of these perennial plants the marsh grows up into typical high marsh or ‘‘mixed salting”, the Salicornia being VARIETY OF COLONISTS 197 gradually crowded out, or surviving only in special, favourable spots. On different parts of the coast the mature phases of salt marshes wear a distinctive facies. Sometimes it is Sea Lavender (Statice), sometimes Thrift or Sea Pink (Armeria) that is the out- standing element, whilst in other cases the turfy Glyceria matrix holds its own in relative purity. Another plant frequent on salt marshes is the Sea Purslane (Obtone portulacoides), a low prostrate bush with glaucous leaves, which commonly outlines the banks of creeks. Occasionally Obione spreads over the marsh from its ordinary station, overrun- ning and obliterating most of the other plants (PI. XVI, p. 176). Indeed, no two salt-marsh systems are quite equivalent when their plant coverings are analysed in detail. To attempt to explain these things, which depend on many factors, is im- possible at present. Food and climatic differences are no doubt partly accountable, giving this or that plant a relative advantage over its competitors, whilst what is termed the ‘‘ historic factor” —whether the agents of distribution have brought a given plant on to the scene sooner or later—must also have an important bearing. It is probable that a certain species of plant will have its best chance of establishing itself in a marsh at a certain stage in the development of the marsh, and if at the critical moment its seed be not forthcoming the marsh will continue to develop without it, and this result will not be affected by any belated supply of seed. A very characteristic region of the salt marsh is the Juncus zone, which commonly occurs on the rising ground adjacent to the dry land or sand dunes backing the marsh. /uncus maritimus and the lower-growing Juncus Gerardi are the characteristic species, and associated with these are other halo- phytes, of which the Sea Milkwort (Glaux maritima) is the most usual. The Juncus zone is overrun by the higher spring tides only. It is most tenacious and resistant of erosion, and doubtless has considerable mechanical value in screening from scour whatever ground happens to border the marsh, and is especially useful in protecting the foot of such readily erosible terrain as sand dunes. Except where salt marshes are in 198 PLANT WINNING OF TIDAL LANDS process of occupying new frontages the phases antecedent to the Juncus zone are not readily observed, though in cases that have come under our observation Glaux maritima was the pioneer plant. In view of the mechanical value of the Juncus zone in protecting the shore, fuller knowledge of the circum- stances which control its development is much to be desired. The Process of Accretion.—The foregoing account of the salt marsh and the details of its structure and development show that the vegetation covering plays a part both in the accretion of silt, and in resistance to erosion, the importance of which it would be difficult to exaggerate. At every level on the shore of sheltered inlets and estuaries plants establish between the high-water marks of the neap and spring tides. These vegetated areas form the collecting surfaces where silt is retained and permanent rise in level effected. Indeed, this co-operation of plants is practically universal where new land is being organized from supplies of mud or sand transported by the agency of water currents and wind. The vegetation contributes to the operation in two ways. Firstly, it provides a shaggy covering to the ground which entangles the silt upon and between the plants; secondly, by its inherent capacity to grow through these increments (anarhizophytism), the newly- won material is bound and fixed by the roots and underground stems of the halophytes. In other words, the silt forms the soil and the plants keep pace by their growth. At the same time the vegetation of previous years becomes in large part buried, thus enriching or manuring these soils with organic matter, and accounting for one factor in their recognized bound- less fertility. The following unpublished data derived from the Blakeney marshes illustrate the foregoing: these determinations, together with those of garden soils, were made for us by the late Dr. S. M. Baker, whose great knowledge of salt-marsh algz was always freely placed at our disposal. The table gives the losses undergone on ignition by the surface soils expressed as percentages of their original dry weights, and may be taken as giving an approximate clue to the organic matter present. ORGANIC MATTER 199 Mean Loss on Ignition, Nature of Marsh Vegetation. per cent of Dry Weight. Mature salting with Obione nae a 21.39 Pelvetia-Salicornia marsh... ane 17.85 Young marsh under Fucus limicola aes 8.39 Mud with Vaucheria Thuretit ie bas 7.30 Mud with Microcoleus chthonoplastes aes 4.86 For comparison with these results the corresponding losses in dune sand fixed by the moss Zortula ruralis was 0.69 per cent; and in a sample of heavy clay loam in a kitchen garden manured in spring the following percentage losses on ignition were determined, six months after manuring: Runner beans, 13.32; potatoes followed by cabbage, 16.26; maize with leaf mould, 21.55. We find generally that the soils of Obione saltings are very rich in organic matter; so, too, is the soil of a large Salicornia marsh, the surface of which is densely covered with the curious, non-attached fucoid Pe/vetia canaliculata, forma libera (cf. p. 227). The three other determinations in the table are of interest, as they refer to quite young marsh soils occupied by various species of Algz. The source of the organic matter in these cases is, doubtless, the filaments and thalli of the Algz which have become buried in the ordinary process of accretion. Mud and sand-banks, of course, often arise without the inter- vention of plants, but these are turned over by every tide and are liable to be shifted from one place to another with changing winds and currents. The process of warping, too, as practised in the Bay of Fundy marshes (and presumably elsewhere), is also stated to be quite independent of the presence of vegetation.1 This shows that the marsh reclaimer is able by technical skill in his art to dispense on occasion with the services of plants. It is the power which plants have of organizing and retaining ground which gives them value in this connection, and makes it desirable to ascertain in detail the part which each species of 1 See Ganong, ‘‘ Vegetation of the Bay of Fundy Marshes”, Botanical Gazette, Vol. XXXVI, p. 167, Chicago, 1903. 200 PLANT WINNING OF TIDAL LANDS plant plays in its own particular zone. For, armed with this knowledge, it becomes possible by artificially introducing a given species at the appropriate moment to hasten the passage of one phase into the next, and thus promote accretion without pauses or delays. Should this practice be adopted we should look forward to a time when, by vegetation methods, combined with temporary engineering constructions for protection from scour and the control of currents, tidal lands would mature for final reclamation not only more rapidly than is at present the case, but also in topographical distribution conveniently for the purpose. It has been a principal object in writing this book to emphasize the importance of plants from an engineering point of view. The Measurement of Vertical Rise in Level of Salt Marshes.—Information on this subject is hard to come by, except in districts like the Isle of Axholme in N.W. Lincs, where the operation of warping is practised. Warping consists in admitting tidal waters heavily charged with silt on to banked lands which lie below high-water mark, and allowing the silt to deposit. By continuing the operation for a period of two or three years (two tides a day for some ten days per month) a thickness of 1, 2, or occasionally even 3 feet of silt is thus de- posited, the thickness depending on the richness in silt of the tidal waters employed and the skill with which they are led to and distributed over the lands to be warped. On the Blakeney marshes a few experiments extending over a period of two and a half years have been made, and as the results are sufficiently numerous and consistent to be accepted as reliable a few of them may be quoted here. It will be under- stood, of course, that these are records of the natural silting process unassisted by any of the artifices of warping, and that the tides, unlike those of the Humber, are not heavily burdened with silt. The texture of the deposit is fine, and sand is prac- tically absent. Example 1.—High salting bearing Obione covered by the higher spring tides, say 120 tides a year. Rise of level in 2 years 5 months, 0.4 inch. At this rate the rise would be 1 foot in 72 years. RATES OF ACCRETION 201 Example 2,—Low marsh which in 1g1o bore only a thin scattering of Salicornia annua (Marsh Samphire), Fucus limicola, and a few plants of Aster Trifolium. Since 1910 the vegetation has rapidly increased, until at the present time (1917) the Sali- cornia has reached maximum density and Asters are every- where abundant. Other halophytes are also making their appearance. The marsh is covered by almost every tide, say 700 a year. Rise of level in 2 years 5 months, 2.5 inches under Salicornia, 3 inches under Fucus limicola. At the latter rate the rise would be 1 foot in 9} years. This is the largest result yet obtained. Example 3.—Salicornia-Pelvetia marsh, covered by all spring tides (240 tides a year) and in the centre by the higher neap tides as well (making about 600 tides a year). Determina- tions were obtained at stations every 10 feet along a line crossing the long axis of the marsh at right angles, i.e. from bank to bank. The rise in level after 2 years ranged from o.2 inch at the edge to I-1.25 inches at the centre, the intervening stations, according to their position, giving readings intermediate be- tween these extremes. At these rates of silting the rise in level ranged from 1 foot in 120 years, at the edge, to 1 foot in 19 years at the centre. The distribution of silting here is in con- formity with the fact that young marshes are generally concave (i.e. slope down gently to the creek), whilst old high saltings are practically dead level. We are indebted to Dr. M. C. Stopes for organizing the series of accretion stations (in August, 1914) in Example 3, and to Dr. E. J. Salisbury and Mr. B. K. Hunter for measuring up the results (in August, 1916). The above, and other preliminary results that have come to hand, all point to the importance of the number of tidal immer- sions in determining the amount of silt deposited. Whilst this is no doubt the most important factor, we are impressed with the high efficiency of the embedded Fucus dimicola in promoting accretion. In Example 2 (and other cases bear out these results) ground with Fucus grew 0.5 inch more in 2 years 5 months 202 PLANT WINNING OF TIDAL LANDS than similar ground close by carrying Salicornia annua only. This difference is roughly equivalent to a vertical rise of 1 foot in about 60 years. The method by which these results were obtained was not that of placing the levelling staff on the same spot at convenient intervals of time and comparing the readings with a fixed bench mark. The expansion and con- traction to which tidal soils are liable and the varying state of muddiness of the surface render such a method quite unreliable for the determination of small increments. Driving a peg and measuring the length projecting from the surface is also open to objection, as the peg may be trodden on, moved, or pulled out of the ground, and in any event is liable to promote scour and erosion in its immediate neighbourhood, or to collect seaweed and other drifting matter. We lay a new surface closely similar in texture to the actual ground, harmless to vegetation, and of a distinctive and permanent colour. For this purpose we experimented with a series of the well-known coloured Alum Bay sands, from which the plum-coloured sand was finally selected as being quite unlike any silt occurring in the Blakeney area. The method of procedure was as follows :— Places or stations for accretion observations having been selected, e.g. at measured distances along a straight line joining two known points, the coloured sand, previously pulverized in a mortar and passed through a sieve of about 50-60 meshes to the inch, is laid on the ground in circular areas, 6 inches in diameter, to a thickness of 1 millimetre. As a rule at each point these areas are laid in duplicate, right and left of the line and touching one another. That the coloured sand may lie evenly on the ground, and that losses by wind may be avoided, the sand is applied from a conical Cerebos salt-cellar of the ordinary pattern on to a sieve (6 inches in diameter and having 30 meshes to the inch) lying on the ground. The frame of the sieve should have at least 2 inches of freeboard, under cover of which shelter from the wind is obtained during application. From the sieve the sand falls on to the ground. For additional assistance in rediscovering the area after lapse of time three little pegs in the circumference of each area should be driven into the ground till almost flush with the surface. Even if entirely bedded over by accretion when the time comes for re-examination the pegs can generally be located by probing. For the recovery of the stations it is of great importance to mark the ends of the line by visible posts, and to measure and book accu- rately the distances. To determine the amount of accretion a vertical slice is cut out from the area and measurement made from the upper surface of the coloured layer to the new surface of the ground, It is essential that the slices so measured be cut vertically, otherwise the results are exaggerated. If the holes made in removing these slices be filled in with mud the same area can be used on future occasions. It is well to avoid replacing the actual slices cut out, as the pigmented zone is difficult of adjustment. RATES OF ACCRETION 203 On bare ground or ground containing algal filaments there is a liability that the first tide may wash away the coloured area. To avoid this another device is employed. A perforated sheet of metal 6 inches in diameter is laid on the area, the perforations following a convenient pattern, e.g. a doubly- outlined Geneva cross, with.one limb parallel to the line of direction. Two- inch pins with coloured glass heads are pressed through the holes into the ground, and when the sheet of metal is removed the heads of the pins are made flush with the surface. Subsequent slicing of the area will show the height of accretion above the heads of the pins. To fix down on the soil permanently a disk of metal, &c., would give a false result, because it would interfere with the free colonization of the area by Algze or other vegetation. CHAPTER XI Miscellanea (Cliffs, Rivers, Channels) There remains for consideration the special treatment of certain particular types of terrain to which no detailed allusion has yet been made. These include cliffs by the sea, the banks of creeks and tidal rivers, stony river beds liable to sudden floods and migration of channel, &c. Of these by far the most important in practice are the sea cliffs, in view of their liability to erosion by the sea. Sea Cliffs.—Two principal causes combine in the destruction of cliffs, viz. sub-aerial agencies and the undercutting of the base by direct wave action. The sub-aertal agencies include especially land drainage, percolation, frost, and chemical action. Where these operate in the absence of wave action the face of the cliff tends to assume the angle of repose proper to the materials. By appro- priate treatment, especially of the drainage from the land, such cliffs may be rendered relatively stable, for under these con- ditions a spontaneous vegetation will arise, protecting the surface and minimizing or obliterating all liability to erosion from rain impact and the like. The inherent tendency of ali sloping ground to undergo a certain amount of slip cannot be entirely eliminated, as all hygroscopic movements of the soil must under the action of gravity tend in the downward direction. Apart, however, from special cases in which the soil becomes viscous with imbibition of water, sloping ground at the angle of repose may, if properly covered with vegetation, be regarded as sub- stantially at rest. The frontages where Tertiary deposits abut on an exposed 204 SLIPS 205 coast-line or estuary are peculiarly liable to destruction, by reason of the double effect of under-scour and the simultaneous pressure forwards, in the manner of an avalanche, of the plastic clays of which they are largely composed. Frequently veins of sand or gravel are sandwiched between the clay deposits, and such veins are denuded by rain or sea wash. Even without the predisposing cause of undercutting at their base, such cliffs of clay tend by gravitation to collapse. The New Cross railway cutting is an object lesson in this respect to Londoners. Ever since the construction of this length of the Brighton Railway seventy years ago, the clay slopes running two or three miles south of New Cross have been in a condition of unstable equilibrium. The gradient of the line being heavy, and the oscillation due to express trains extreme, these banks were until comparatively recently actively mobile. Their movement has been arrested in the main by cutting drainage grips at the most dangerous spots, and either burning the clay in such grips, or laying block chalk in them to enable the land water to get away. The coast-lines at Herne Bay, Yarmouth (I. W.), and Walton- on-the-Naze are notable instances of the danger of the movement of what in Essex is locally termed ‘‘ blue slipper”. At Herne Bay one of the authors saw a field of turnips, which had slid bodily from the crest of the cliff to the shore, the turnips growing undisturbed in their new habitat. The vagaries of coastal landslips often appear inconsequent. Telford’s practice in building reservoir embankments was to mix with his puddle clay clean gravel, with the object, by adding weight, to prevent its tendency to slip. The puddle clay of a dam is of necessity absorbent of water, and it is upon this saturation that its weight and water-holding properties largely depend. Frequently, in order to economize in the mass of materials used in the construction of a reservoir embankment, a thin hearting of puddle clay is weighted with stone or concrete blocks, pitched on both sides to prevent the spreading and settle- ment of the clay. The true cure for a tendency to slip in the design of a clay structure, is not to attempt to lay out walls at a steeper inclination than that of the angle of repose of the 206 MISCELLANEA material employed. Sea and river walls in the Thames estuary are mostly laid out at an inclination of 2 to 1 on the outer face, and 1} to 1 on the inner face where stiff puddle clay is obtain- able. Many plastic élays will not stand at anything like so steep an inclination, 5 to 1 or 7 to 1, or even flatter still, being often necessary to stability. One of the most potent agencies in conserving artificial slopes is that of systematic planting, the close network of roots of the plants creating a mat of immobility. It frequently happens that landslides occur with great sudden- ness, and apparently long after predisposing causes should have ceased to operate. Such subsidence is in the main due to the underground passage of water of percolation. An area of soft silt underlying a mass of clay may remain for a long period in a condition of relative stability, owing to the incompressi- bility of its liquid constituent. As its moisture is gradually reinforced by percolation, it slowly develops the attributes of a semi-liquid body, and the varying pressures of the super- incumbent earth cause its displacement, producing lateral and vertical stresses, until the equilibrium of the overlying strata is disturbed. The resistance of friction, due to masses of soil over such a cushion of semi-plastic silt, is ultimately overcome, and a landslide results. This action is repeated, it may be at considerable intervals, periodically, as the liquidity of the subsoil becomes such that it follows the laws of hydrostatic equilibrium. To counteract this action, ample drainage to check the tendency to the formation of subterranean pools of semi-liquid slurry is the first requirement. Rats and rabbits infesting a bank, by disturbing its superficial resistance to percolation, may set up areas of potential under-surface slip. The infinite variation in the physical economy of the con- stituent materials of earth banks renders generalization difficult and formule precarious. Mr. W. Airy’s remarks on the varia- bility of clay resistance are of interest in this connection :} ‘He exhibited a little rough machine he had used for testing earthwork and taking the cohesion of the ground. The block of wood might be taken to represent a block of raw clay taken out of a cutting. There was e common lever-balance, and a couple of movable cheeks were fitted into chases cut in 1 Proc, Inst. C. E., Vol. LXV, p. 188. UNDERCUTTING OF CLIFFS 207 the sides of the clay block; and the clay having been rammed in a box so that it could not move, weights were put in the scale until the head was torn off. After subtracting the weight of the piece that was torn off, and measuring the area of the cross-section that was broken, the constant of cohesion was determined. For the constant of friction he arranged a certain number of blocks of the same clay in a tray, and scraped them off smooth; then he had another block of clay with a smooth surface which he put on it, and then tilted the tray until the loose block slid; that gave the coefficient of friction. He should like to refer to the exceedingly wide range of tenacity shown by different kinds of clay. In one set of experiments with ordinary brick loam, that clay gave a coefficient of cohesion of 168 lb. per square foot, and a co- efficient of friction of 1.15. With some shaly clay out of a cutting in the Midlands, he had found a coefficient of tenacity of 800 Ib. per square foot, and a coefficient of friction of 0.36. That was a very wide range, but it was only a part of what was actually to be found in practice.” In respect of the protection of the toe of a clay embankment against the danger of wash, the practice in the construction of reservoirs in India is of interest. Pitching is carried in such ““tanks” or reservoirs to a level of about 2 feet above the antici- pated maximum wave wash. The thickness of pitching used for this purpose in feet is taken as a mean at o.74/ fetch of waves in miles. In practice it varies from 6 inches at the bottom to 18 inches at the top of the highest dams. At the crest of the stone pitching, thus forming a wave breaker, there is usually a step of 9 inches in the pitching of the slope of the tank. The object of this break in contour is to check the run of the waves up the slope. Ondercutting by the sea is the serious cause of cliff erosion, and its degree is closely related to the texture of the material forming the base of the cliff. Where this is friable, as com- monly on the East Coast, the falls of cliff are both extensive and frequent. Protection from this class of encroachment is obtained in two ways: (1) By fortifying the cliff base against erosion by engineering constructions, such as sea-walls, breastworks, and the like, the cliff base is enabled more effectively to resist the direct attack of the sea. (2) Indirectly, by bringing about the accumulation, by natural methods, of obstacles which keep the 208 MISCELLANEA sea from working on the cliff base. In other words, causing beach materials (shingle, &c.) to collect so that the high-water mark is set back. This result is commonly effected by means of groynes, which both catch and tend to retain the travelling drift. Artificial Dumping.—There are many localities where, by means of artificial dumping of shingle, a threatened coast-line may be economically conserved; in fact, there are few spots where a judicious application of this method would fail to result in permanent protection, provided simultaneously a system of groyning were carried out. Such dumping has not, however, been resorted to in many instances. At Hove the sea-wall enclosing the Lawns was threatened, immediately after its erection, with destruction by under-scour. The expedient of depositing along the front some of the surplus shingle encroaching on the port of Shoreham was resorted to, with complete success. Similarly, at Newhaven, the low-lying eastern frontage of the harbour was rendered perma- nently secure by bringing shingle from the west side in railway trucks and tipping it on that foreshore, a scheme of groynage being also carried throughout. All that is really required is at high water to discharge the shingly soil of dredging operations from hopper barges as near the coast-line as practicable. If such works are judiciously carried out, the sea washes up and redistributes the material so dumped to the best advantage as a protection. Some ten years ago the condition of the frontages of Lowes- toft and Pakefield was desperate, the inroads of the sea being of an alarming character, and expenditure on the fronts an overwhelming burden on the local bodies concerned. Simul- taneously a new Herring Basin was constructed at Lowestoft. The dredged material from this basin, which consisted mainly of clean shingle, was taken to sea and deposited in deep water. Had it been brought alongshore and deposited, in all probability the problem of the defence of the wrecked coast-line would have been made good at comparatively small cost. It is in the power to enforce combined operations of this nature that the utility of a central organizing authority becomes self-evident. There TREATMENT OF CLIFFS 209 are many localities, such as Dungeness and Orfordness, where shingle exists in boundless quantities, and an insignificant fraction of such accumulations, if judiciously distributed along threatened strands, would render them immune from destruc- tion. The multiplicity of conflicting authorities, coupled, in many instances, with no specific power to act, often prevents such a policy being adopted. The result is that valuable land is washed away, or works of enormous cost inaugurated, when, as at Lowestoft, a simple remedy was immediately available and disregarded. Even halophytic vegetation alone is unable to operate advan- tageously on a crumbling cliff base, because as a rule the degree of mobility is too great for its establishment. At the same time, when material collects at the base of a cliff, whether alongshore drift or talus, it should be planted, to render its removal more difficult. In exceptional cases, where sand blows, Marram Grass can be used and the formation of low sand dunes promoted at the foot of a cliff. In very many cases of falling cliffs no protective measures are taken till some valuable building or other property is threatened with destruction. Under these circumstances, both the top and foot of the cliff will probably need immediate atten- tion—drainage and planting in the case of the former, protection in the latter. As an example, the case of the Parish Church at Lyme Regis, standing near the edge of a cliff of blue lias, may be given (fig. 48). The quotations are from the report of the engineers who were consulted in the matter. Their recom- mendations were carried out in I91I, and are reported as having given complete satisfaction. “‘Owing to the serious inroad made by the sea on the cliffs and to the argillaceous nature of much of the upper portions, the ancient and historically interesting church of St. Michael is in a grave position. ‘‘Within the memory of many now living there were two fields between the graveyard of the church and the edge of the cliff; these have not only disappeared, but a portion of the graveyard itself has wasted away. (0924) 15 210 MISCELLANEA “It is common knowledge that many human remains have been taken down with the slipping of the ground and have been washed away, and there is at the present time a brick vault projecting from the face of the cliff. ‘‘The church now stands at a distance of but 80 feet from the edge of the cliff, and the playground wall of the old school but 12 feet. “The inroad of the sea is one of the causes of danger to the church, and the foot of the cliff calls for attention; but the greatest immediate source of danger to the fabric is due to the condition of the upper part of the cliffs. “The graveyard, for a depth of 10-15 feet, is composed of a light, porous material, through which the water has no diffi- culty in finding its way; the old excavations for graves permit the infiltration of water, and in some cases the gravestones and surrounding iron railings are tilted over where the water has washed out in its course the underlying ground. ‘*The water that thus sinks down converts the clay and shale into a slippery condition, and then finds its way out at the face of the cliffs, carrying much of this silty matter with it. This slips down until it reaches the uppermost limestone bed, where it oozes over the edge and falls into the sea. ‘Tt is the loss of material in this manner that is the imme- diate cause of the close proximity of the top of the cliff to the church building. ““When the mixture of clay and shale reaches the limestone bed it has opportunity to become drier before entirely slipping over, with the result that a fresh supply, coming on with the return of wet weather, mounts up above this accumulation, and forms ridges behind which water collects in pools. The water in these pools in turn sinks in and finds its way out at a lower level, forming a slippery foundation for the partially dried portion. “This action is again repeated, and the whole amount is thrown into the sea by the pressure of the ground behind.” For the arrest of the trouble and the protection of the church the following recommendations were made:— “The first step to be taken is the insertion of rubble drains, OLD SCHOOL BUILDINGS ‘ \ < \ Pranted with \ Rillows lyard apart \ . \ \ Old rails 90 lengths’ / Section of Concrete 7 & Rubble Drain Shale 2 sf Rubble Rubble Filling Ordnance Datum Fig 48.—Type Section of Cliff (Lyme Regis) 211 212 MISCELLANEA which will serve the double purpose of draining the church- yard and slopes and of assisting the latter to remain in position. ‘‘These drains will consist of trenches filled with rubble, a pipe, of which the lower half of the joint is cemented, the upper half being left open, being laid on clay puddle throughout its length, and discharging on the beach. ‘At the foot of the cliffs a reinforced concrete wall will be required, to prevent further erosion of the limestone beds by the action of the sea. ‘‘This work will be carried from the end of the existing wall following the base of the cliff to a point 290 feet to the north. At the northern end a small groyne might be placed with advan- tage to accumulate shingle as much as possible in front of the wall. ‘‘The shale beds above will be protected at intervals by masonry.” For the consolidation of the ground on the completion of the work the slopes at the top of the cliff were planted with willows at 1-yard intervals. Though these were entirely suitable for the purpose, they were gradually replaced by a miscellaneous assortment of garden shrubs, which, proving unsatisfactory in the position, have been discarded and willows once more rein- stated. The object of vegetation in positions of this kind is by deep penetration of roots to prevent movement of the ground below, and also by its matted growth at the surface to arrest crumbling and slip. Such vegetation by its sheltering effect will further prevent the ground from cracking in dry weather. The plants most suitable for the purpose are vigorous growers, with a tendency to ‘‘run” and form numerous offsets. Willows are good, especially Salix pulchra, and so is Populus deltoidea, on account of its deep-rooting capacity. In climates free from danger of severe frosts Tamarisks may be used with advantage, whilst species of Spirzea and the Snowball plant (Svmphoricarpus racemosus and vulgaris) are recommended on account of their free ‘‘running” habit. In many situations the Red Valerian (Centranthus ruber) very rapidly covers the steep broken sur- TREATMENT OF CLIFFS 213 faces of cliffs, and as it occurs in three colours—pink, crimson, and white—it lends itself to attractive decorative effects. As the study of vegetation in connection with the stabilizing and protection of cliffs and steeply-sloping ground is only in its infancy, there is no doubt that bold experiments among a wide selection of plants would lead to discoveries of great utility in the treatment of ground of this kind. Moreover, it has to be borne in mind that a plant which thrives in one exposure and climate will not necessarily adapt itself to other localities where these are different. Cliff gardening as a hobby has much to recommend it for its own sake as well. The case just cited so fully is a good example of the value of sound diagnosis preceding treatment—a method which must always be followed to secure successful results. The wasting cliffs of soft incoherent material, clay and sand, such as those south of Cromer in Norfolk, the Bouldnor Cliff near Yarmouth, Isle of Wight, and the Bournemouth Cliffs, present certain out- standing problems. Primarily, no doubt, lack of protection at the base is the root of the evil, but given this, good judgment will be needed to heal the mobile face. The natural vegetation on these cliffs is by itself quite inadequate to hold the ground. The Cromer cliffs are infested by Coltsfoot (Zussilago Farfara), which develops everywhere its rhizomes, but these have no appreciable effect in stemming the flow of the viscous clay as it makes its way in sluggish cataracts to the foreshore. The same holds good of the Giant Horsetail (Eguzsetum Telmateia) on the Bouldnor Cliff. Ground like this needs drainage to eliminate the larger sources of water and planting with deep-rooting and spreading plants. Whilst there are many plants that should be tried, from want of knowledge we are only prepared definitely to recommend Willows and Poplars. When a department comes into existence to deal with coastal problems experi- mentally here is a matter that lies to its hands. Analogous in many ways to the cliff face is the treatment of the slopes of railway cuttings and embankments where the materials have a tendency to slip—an effect due to the clay at a certain depth becoming saturated with water, so that the ground above slides down to a lower level under the influence ar4 MISCELLANEA of gravity. Water gets access to the interior of the bank by means of cracks which develop during periods of drought, and the only remedy which engineers have discovered is the pro- vision of very complete drainage for the removal of the water. The expedient of planting various shrubs and trees has been tried, and though it may have mitigated the trouble it has hitherto failed to remove it. The problem to be solved is briefly the establishment on such places of trees or shrubs of deep- rooting habit, so that the layers of the bank may be bound together, and, in addition, the clothing of the surface with a continuous mat of low vegetation to screen it from desiccation and thus prevent cracking. Considering the very large number of plants available, it would be strange if foresters or skilled gardeners should be unable to find a satisfactory solution. Whilst it is easy to suggest the names of likely plants for the purpose, we are reluctant to do so in the absence of systematic trials. The trees employed, in addition to being deep rooters, will have to be fairly permeable to light to ensure a proper development of the ground vegetation. It will also be an advantage that the latter, when it dies off in autumn, should not too readily catch fire. These are the principal elements of the problem awaiting solution. River Banks.—Creeks and river channels traversing saltings are very prone to erode their banks, especially in reaches which allow some ‘‘ fetch” to the wind, which often springs up when the tide flows. To protect banks from the resulting “slog”, simple expedients, such as stakes and boarding, rough bundles of brushwood, or better, properly made fascines, are commonly employed. Where the degree of salinity reaches the half strength of sea water (1.5 per cent of salt) trees cannot be used, as no tree-like halophyte is available outside the tropics. Whatever the future may have in store, at the present time none of the mangrove trees of tropical mud flats has been acclimatized to serve the purpose, nor has any attempt been made to breed a form tolerant of a cool climate. A few experiments have been made with Willows (Salix alba) to accustom them to salt water. Willow cuttings were attached to corks floating in fresh water, and as roots developed CAVING OF BANKS 215 the cuttings were transferred at intervals of a few days through a series of solutions of Tidman’s sea salt, each solution being 0.1 per cent stronger than the last. The general result of this attempt to educate the willow to halophytic life was that all the cuttings survived the progressive shifts up to 1 per cent Tidman, whilst very few lived in 1.3 per cent, and none in 1.5 per cent. Still, these results are sufficiently encouraging to deserve repetition with other species of willow; for undoubtedly it would be of great utility if a willow could be found to plant on the banks of tidal creeks. At the top of an estuary the water at high tide rarely, if ever, reaches a high degree of salinity, and in such positions we are disposed to think willows might safely be planted; and even if the experiment turned out a failure not much harm would have been done. As regards the caving of river banks in cases outside the influence of the sea, the following recommendations! are of value :— ‘“‘The willow is admirably adapted to holding alluvial soil in place. It is far more serviceable for this purpose than walls of masonry, and the facility with which it reproduces itself by seed, suckers, sprouts, and cuttings, both natural and artificial, makes its use very simple and inexpensive. “The great difficulty with planting any sort of tree on perpendicular banks is that the caving of the soil is so rapid that the planted tree has no opportunity to get a start before it is undermined and precipitated into the river. An excellent scheme is as follows: Green willow poles, 18 to 20 feet long, are taken in spring and laid on the ground near the bank 2 feet apart, with their butts (ends pointed) directed towards the river. Woven fence wire is then stretched along over the poles and stapled fast to each one. Sections of wire about roo feet long can be handled to best advantage. After the wire has been securely fastened to the poles, they are all pushed over the bank together, so that the pointed butts of the poles will fall and sink into the soft mud at the water’s edge. As the bank caves off 1 Taken from U.S. Department of Agriculture, Bureau of Forestry, Circular No. 27, by G. Pinchot. 216 MISCELLANEA some of the falling soil will lodge on the wire, partially burying and weighting down the poles, which will consequently strike root and grow. The wire will serve to hold the mass of willows together until they have become firmly rooted. The ends of the woven wire should be made fast to wire cables running back over the bank some distance, and fastened to posts set firmly in the ground. The caving and erosion of the bank will soon round off its top corners, and the growing willows at the water’s edge will catch the soil as it rolls down the declivity, causing a bank to form of just the right slope to resist erosion most effectually.” Reclamation of River Sand and Shingle.—On the Continent of Europe the practice of recent years has tended to demonstrate the high value of the White Alder (A/nmus zncana) as a pioneer on all sorts of inhospitable and mobile soils. These include unstable mountain slopes, talus, river banks, and especially wastes of sand and shingle that cumber the beds of rivers liable to floods. Thus, on the River Ticino below Bellinzona, the Swiss have employed the White Alder with excellent results on the shifting shingly stretches of ground that border the actual channels. The method followed is to plant alder seedlings in their second year in double rows in shallow trenches running parallel to one another, and at right angles to the direction of stream flow. From these plantings parallel alder hedges, 6 to g feet apart, quickly arise, and acting as groynes they stabilize the ground and collect silt whereby the surface is appreciably raised. The roots spread into the spaces between the hedges, and in time the whole area is covered with a thicket of alders. A great merit of this plant is its habit of producing nitrogen- fixing tubercles on its roots, whereby the nutritive value of the soil is much increased. This type of planting requires about 5000 seedlings to the acre. As the White Alder is quite hardy in Britain, and grows with great rapidity, it evidently deserves a full trial in connection with protective and reclamation work in this country. In South Africa in the district of Oudtshoorn, in the Little 1 See F. Aubert, Schweizerische Zeitschrift fiir Forstwesen, 1914, Pp. 207. Plate SA Shingly bed of Olifant’s River, Cape Colony Pnotus, supplied by Miss L. Britten Groynes on Grobbelaar's River, Outshoorn, S_ Africa SHINGLE RECLAMATION PEBBLE GROYNES 217 Karroo, where conditions more or less comparable to the Ticino obtain, the shingly wastes along the course of Grobbelaar’s River are reclaimed by the construction of rough groynes built of water-worn boulders and pebbles, held together by coarse wire netting (Plate XXI). These groynes promote a raising of the level of the ground by silting, and the new land is taken over for ostrich farming, for which the district is famous. Lucerne is grown on the reclamations and fed to ostriches, in much the same way as sheep are folded. The foregoing examples, which by no means exhaust the river-side problems capable of solution by simple expedients, must suffice for this part of our subject. Apart from the fixation of sand dunes with its established routine, the employment of plants as agents in protection and reclamation work is still undeveloped, and it is premature to dogmatize on methods of treatment for particular cases. The whole subject needs further study and experimental exploration. But even when experience has accumulated it will be found that the special features of each case will require the most careful consideration, for the circumstances of soil, climate, and physical conditions are never identical in different cases. CHAPTER XII Blakeney Point, Norfolk, from an Engineering Point of View It is proposed in this chapter to select a suitable demonstra- tion area on the coast, and to describe its structure in relation to the dynamic phenomena which have determined and are still modifying its relief. The method pursued will be that of the guide-book, and the features recorded those with which the maritime engineer has concern. Whilst there are many localities that would serve our pur- pose, we have decided on Blakeney Point, Norfolk, as our area, for two reasons. Firstly, Blakeney Point is comprehensive, including within reasonable compass the three great systems of the shore, namely, sand dunes, shingle beaches, and salt marshes. In this respect it is unrivalled. The second reason for its selection is that Blakeney Point is a Nature Reserve under the National Trust, and hence will be available permanently for purposes of study. As a consequence of these advantages the area is much resorted to by naturalists, whilst a convenient laboratory has recently sprung up, more particularly for investigations in mari- time plant ecology. ‘Blakeney Point consists of a finger or spit of shingle some eight miles in length, which leaves the mainland near Wey- bourne on the coast road leading west from Sheringham to Wells. From the point of its departure the spit runs a trifle north of west almost parallel to the coast, and ends in the sea beyond Blakeney opposite the hamlet of Morston, from which the tip of the spit is distant about a mile and a half. The eastern part of the narrow area thus enclosed has been reclaimed 218 GENERAL TOPOGRAPHY a19 from tidal invasion by the construction of sea-walls, whilst the western part remains an open estuary, bordered by salt marshes and filling with the tide to form what is in effect an inland sea. By far the best point for a general view is the top of the tower of Blakeney Church, which crowns the hill (itself more than 100 feet above sea-level), up which creeps the ancient, red- roofed seaport of much former prosperity. Beyond the shining muds, with their winding creeks and minor shipping towards the outlet, is the great shingle beach—a broad and toilsome causeway some 400 feet in width—and outside this the North Sea and no intervening land to the Pole. The spit of shingle is the outstanding topographical feature of this shore, and all else is subordinate to it. Under its lee an interrupted fringe of salt marshes has sprung up; whilst upon its surface, especially at its western end, blown sand from the shallow waters outside has drifted to form dunes. All this diversity of contour and relief, and much besides, is plainly visible from the church tower. History relates nothing of the origin of the great beach, except that it has tended intermittently to push forward its non- attached western end. The result of the last hundred years seems to show that Blakeney Point has about reached the length of its tether; that whatever ‘‘records” it may have “broken” in the advance of its growing point in ancient times, there is little likelihood of its ever overlapping Stiffkey and Wells, as it has overlapped Cley, Blakeney, and Morston. Geologically, Blakeney Point has reached maturity. Shingle, obedient to the currents, still drifts along its seaward front from east to west, but these supplies for twenty years or more have tended rather to accumulate at and widen the distal end than to project it farther from its base. Quite lately new outer beaches have appeared overlapping the nose by several hundred yards; these in all probability will be driven inshore as were their predecessors of half a century ago. The natural and convenient point of departure for a visit to Blakeney Point is the village of Cley, four miles by road from the railway station at Holt. It is natural, because Cley lies just at the point where the River Glaven discharges into tidal waters; Cley is, in effect, the head of the estuary. It is 220 BLAKENEY POINT, NORFOLK convenient, because the traveller can choose the mode of ap- proach—by foot along a sea-wall joining Cley to a point half- way along the beach, or by water to the western extremity itself. Here we shall go out by water to the Point, and return on foot along the beach to Cley. In this the last-formed ground will be visited first, the older stages last. To do this a spring tide should be chosen. A start is made on the turn of the morning's tide. There will be water enough for the navigation NORTH SEA SKETCH MA e MAINLAND ‘BLAKENEY POINT Fig. 49.—Sketch Map of Blakeney Point, showing the general features, the relation to the mainland, and the various reclaimed areas 1, The Headland; 2, the Long Hills; 3, the Hood; 4, the Marams; 5, Cley beach. Villages from west to east: St, Stiffkey; M, Morston; B, Blakeney; C, Cley; G, Glandford; Sa, Salt- house; W, Weybourne. The reclaimed areas are dotted, the dates of reclamation prior to 1834 being conjectural. of the otherwise troublesome upper reaches, and the Point should be reached in not much over the hour. Leaving the quayside hard by the windmill the Cley channel makes its way through a narrow, residual strip of high salt marsh to the beach, nearly a mile distant. On either side of the channel, at an average distance of 300 yards from one another, run two roughly parallel sea-walls. That to the east runs from Cley to the beach, and protects from tidal influence the Cley and Salthouse marshes (aggregating approximately 1000 acres). The bank on the west of Cley channel turns west 200 yards short of the beach, and circles round to Blakeney, 22) BLAKENEY POINT, NORFOLK “SUITIE PY JO SHOOY “9-1 {2UCIGG YIM pas2a0d HUIeIB, UO YsiEUT ‘GC ‘suIBIE Pp! JO yooy usajsaM uo aNOP] YIEAA “TT AA S48se asryduieg “P's ‘ysuepy Jaysy “Py ‘AeMyoeog se uMoUY ‘'YsIEP BYV2A[og-eBius0deS 343 “Wd tmorT Apueg 3eay “yS'y HMOT xnePD “YH tA0zes0gey “qey tasnogy yEOQ-VT “YQ "T—343u 07 Ya] wos saousizjoy = ‘paddew jou $1 pUE[PEaz] 2g} UO Yveq 399N0 MoU ayy “UreYd qa] asimsayjzo yng ‘Gq peyseur sie sauNp | pazjop ase sayssew BES !yO"|G UMEIP St a[3UIYS qwiog Aauayeig jo pug usaqso4q jo depy—oS “317 222 BLAKENEY POINT, NORFOLK where the mainland is rejoined. It encloses 590 acres. Plate XXVII, 2, p. 240, gives a view of this bank looking in the direction of Cley. If to these areas be added the 240 acres lying to the south of Cley, and which constitute the original head of the Glaven estuary, banked in 1824, there results a total of some 1800 acres of land, nearly 3 square miles, reclaimed from the tidal waters of Blakeney Harbour. The Cley channel on reaching the beach turns due west. Its right or northern bank for the next 600 to 700 yards is formed by the lee talus of the main shingle beach. This section of the beach being very mobile and bare of vegetation much shingle is liable to be thrown into the channel by such high spring tides as overflow the crest. Owing to these accumulations in the bed, navigation is impossible except to small boats at the spring tides; whilst a further consequence of these obstructions is the increas- ing difficulty found in draining (by gravitation) the Cley-Salt- house system of marshes, the outfall from which discharges into the Cley channel a quarter of a mile south of the beach. Beyond this encumbered section the channel skirts a mile of high saltings fringing the beach and known as the ‘‘ Marams”’; at the western extremity of the Marams, ona high lateral shingle bank facing Blakeney, is the Watch House. (For details, cf. fig. 50.) A third of a mile west of the Watch House is another ex- crescence of the main shingle beach, the Hood, a double-headed, Psamma-covered sand-hill, forming an excellent landmark; whilst in another three-quarters of a mile Pits Point, the southerly extremity of the Long Hills, is rounded, and the boat enters the section of channel known as the Pit, where such minor shipping as frequents the harbour rides at anchor at high water and rests on the mud at low. In former times the Pit is reported to have held as many as 140 vessels at one time, floating where they lay; now, by reason of silting, hardly a tenth of that number can find accommodation.! 1W. M. Cooke, miller, of Glandford Mill, in a letter to Joseph Hume, Tidal Harbours Commissioner, dated 3rd November, 1845, states that ‘‘ Blakeney Harbour could once shelter 400 vessels; now our ablest pilots could not anchor 50 there” (Appendix to Second Report of the Commisstoners appointed to inquire into Tidal Harbours, 1846, p. 472). Cooke, though not a seaman, was a close observer of tidal phenomena, as other passages in the Report show. THE BEACH 223 Landed on the shingle of the Headland, just south of the Life-boat House, the visitor finds himself in what may be termed the residential end of Blakeney Point. Dotted about within a small area are a few huts or bungalows privately owned, the old Life-boat House, which belongs to the Department of Botany at University College, London, and the Laboratory, a red-roofed building some little distance away. Standing between the flag- staff and the old Life-boat House is a dilapidated hut, the old Pilot House. Now surrounded by sand-hills and invisible from the sea, this house was erected on its present site about 1850, because at that time it commanded the best general view of the sea outside and of the approach of shipping to the harbour. The older seamen at Blakeney remember clearly a time when there were no sand-hills obstructing the view, whilst even in the last six years the advance of the dunes in this part is apparent to everybody familiar with the spot. Blakeney Point, as a whole, from the point of departure at Weybourne to the Life-boat House at the western extremity, may be compared to a gigantic golf club, the head of which, deflected landwards, corresponds to the broad, dune-covered Headland. The line of telephone poles, which runs straight from the Life-boat House to the Bend of the beach, follows approxi- mately the south-east fringe of the dunes where they abut on the great Salicornia marsh, which occupies the valley (or ‘‘ Beach- way”) between the Headland and the Long Hills, the latter being the long finger of shingle which ends at Pits Point. Though at first sight the dune aggregate of the Headland may give the impression of being scattered without system, a stroll along the highest dune ridge parallel to the shore will suffice to show that the contrary is the case, and that the arrangement follows an orderly plan. The foundations of the Headland consist of successive shingle beaches (‘‘apposition beaches”) with furrows or “lows” between. These beaches are approximately parallel to one another and to the major axis of the Headland (the line of telephone poles). These beaches have been driven in succes- sively from the sea front, the outmost being the youngest, and they are formed of materials that have drifted along the fore- 224 BLAKENEY POINT, NORFOLK shore from farther east. The effective outside beach of the moment (which projects well beyond the Headland) appeared as recently as 1912, and when it has been pushed inshore a certain distance it is to be expected that a still younger beach will take its place. The crests of these beaches become dotted about with plant soon after they appear, and such of these plants (especiall* Psamma) as have the power of arresting sand blown in from th shore at low tide become the starting-points of sand dune- The plants settle by preference on the crest because their seed: are brought by the sea in the drift, and it is a characterist - of drift lines to reach the level of the highest tide of the cycle. Thus it has come about that the dunes form five or six suc- cessive ranges parallel to the shore. Each range as it arises tends to screen the preceding one from the source of blowing sand, consequently it is found under these conditions that verti- cal growth slows down till it becomes stationary. Later, unless the dunes become entirely covered with a turf of vegetation, they shrink gradually as sand is blown from their summits. All stages in dune development and destruction can be studied on the Headland. First, the isolated tufts of plants which collect little heaps of sand; next, the blending of these into systems as the level rises and the grass spreads. At this stage vertical growth has been found to average about one foot a year. The highest ranges do not exceed 25 feet above mean sea-level. Farther back the dunes are lower and are closely turfed over, especially by mosses and in some places by lichens. Owing to the large population of rabbits on the Head- land bare sand is being continually exposed to the wind, and the disappearance of the older dunes is only a question of time, unless the rabbits are exterminated or effective shelter be given by the planting of trees. Excellent examples of disappearing dunes are to be found as the Bend is approached along the line of telephone poles, where an extensive area of bare shingle (the ‘‘desert”) has been exposed. However, ‘‘Nature abhors a vacuum ”’, and with the lowering of the ground to tidal level the higher spring tides get access, and, bringing drift and seeds Glaux Low, looking N.E. Plate NNT Photo, W. Rowan Lows in Dune System of Headland filled by a high tide BLAKENEY POINT THE LOWS 225 (especially of Statice binervosa), this stony desert clothes itself in August with sheets of purple visible from afar. The lows separating the dune ranges differ from ordinary valleys in that they have never been excavated from a previously continuous terrain. They are gaps left from the first in the system of construction. The best example is Long Low, running from the Life-boat House to the north-west of the huts and to the south-east of the Laboratory. It dies out towards the Bend some three-quarters of a mile from its point of origin. Two hundred yards north-east of the Laboratory it is blocked by a bridge of sand blown from an adjacent dune. Glaux Low lies just north-west of the Laboratory, and can be followed for a distance of nearly half a mile in a north-east direction, where it communicates with Long Low (Plate XXII, lower picture). In the direction of the Life-boat House it has been long prac- tically obliterated by blown sand, excepting the south-west extremity which is still open. Seaward of Glaux Low is Great Sandy Low, the dominating feature of the topography on the out- side of the Headland (PI. IV, 2, p. 58). This low is essentially a long bay of some ten acres penetrating the heart of the dunes. Into Great Sandy Low the spring tides flow, and the very highest (not more than one or two a year) reach the north-east parts of Glaux and Long Lows. Owing to sand blockages the south-west parts of these lows are inaccessible except on the rarest occasions. Thus, the end of Glaux Low by the Labora- tory has been reached by the tide only twice in the years 1913-6, whilst Long Low, from the sand block to the Life-boat House, was invaded by the tide on 14th September, 1916, for the first time since November, 1897. From an engineering point of view these lows are of considerable interest, because they afford lines of access for the sea. Theoretically, each low should be an isolated valley, but as a matter of fact the sea has established points of connection between them, as a study of the ground or of the map (fig. 50, p. 221) will show. Ass the floor of the low is commonly appreciably below the level of the point of entrance by the sea, the tide pours in with a tremendous rush, under- cutting the sides and lowering the floor. In this way every tide makes it easier for the next one to gain access, and in the (92%) 16 226 BLAKENEY POINT, NORFOLK long run the whole stability of the Headland must be impaired (Plate XXII, lower picture, shows lows in the interior of the Headland dunes filled by a high tide). The remedy is fairly obvious, though in practice not always immediately successful. On several occasions the strategic points of communication between these lows have been blocked with stout brushwood fences, in the hope that wind-borne sand might accumulate in the form of artificial dunes massive enough to resist the impact of these high spring tides. On each occasion, however, a high tide came many months earlier than was ex- pected, and before the dunes had been fully built up and consolidated by Psamma. The tides here are very sensitive to windage, and a gale from the north or north-west will raise the level of high water several feet above the prediction of the tide-table. A feature of no little interest is the fact that fresh water can generally be obtained by digging wells in these shingle lows. In Long Low near the Life-boat House a row of four such wells was dug in July, 1914, and they have continued to yield an inexhaustible supply of good potable water since that date. The level of the water in these wells rises and falls with the tidal cycles, showing a lag of about three days. That is to say, three days after the highest spring tide the wells attain their highest, and three days after the lowest neap their lowest level, the oscillation in the wells being from 15 to 20 inches. It is evident that the fresh water is floating on the salt, and it is remarkable that it should not undergo appreciable contamination. Shingle beaches above tide marks are in general drenched with fresh water, and so far as our experience goes show no abatement even in seasons of prolonged drought such as the summer of 1911. It may be conjectured that shingle has the property of condensing dew internally, a property perhaps shared by the sand dune as well.} To the botanist the colonization of shingle lows is not with- out interest. The older sorts bear little save a sparing turf of the little Plantago Coronopus v. pygmea. Under moister conditions, Glaux maritima (as in Glaux Low) appears, and 1 New Phytologist, Vol. XI, p. 98; Journal of Ecology, Vol. II, p. 35. AICMIST] OI JO S19 ay) PUL SIH Suo7y yi rv ys ay ug “suqqva fq paddoss asojp BSOINJNAL VPING JO saysnq SULvag “YSIV[Y LILIOSTES ay} OJ! INO UNA spriazL] aLFulys AO] ‘asayi Jo a8pa ayy woy | purpvapy ayy jo sounp ayi are yay ayy uO ‘“A'N ONIMOOT ‘“LNIOd AMNUNWIA ‘AVAAHOVAE AHL “HINN areid SHINGLE HOOKS 227 may even spread to form a continuous covering. The estab- lishment of additional species will depend on the opportunities that occur for the bringing of seed, and whether the sea has regular access. In the latter case it is likely that the low will develop into a salt marsh. Before leaving the dunes of the Headland a general view of the large Salicornia marsh should be obtained, preferably from the sand-hill south-east of the Laboratory on which the fifth telephone pole from the Boat House stands. This point commands the whole expanse of this marsh, some 60 or 70 acres in extent, occupying the flat ground between the dunes of the Headland and the Long Hills Bank. In summer it consists of a green carpet of Salicornia annua, with which is associated the unrooted and sterile “bera form of the brown seaweed Pelvetia canaliculata. Covered by nearly all the spring tides this marsh represents an early stage in the development of a salting. Observations show that the level of the Salicornia marsh is rising yearly from one-half to three-fifths of an inch in its middle parts. On its north-west side the marsh is divided into bays or compartments by four or five low shingle beaches, conspicuous objects from the view-point (Plate XXIII). These beaches in the history of the development of the Point must formerly, each in turn, have represented the organic apex of the whole system. Successively they were deflected into their present positions be- fore the main platform of the Headland had been formed, and as each hook was overtopped by the next one formed it would be screened from direct impact of waves and pass into the dormant state. The long hook which closes in the Salicornia marsh, sepa- rating it from the main estuary, and which runs from the Life- boat House to beyond the house-boat Britannia, is still mobile. Evidence of its recent marshward travel is afforded by the stools of Suzda bushes still persisting some yards outside it; origin- ally these bushes grew on the inner fringe of the beach, which has passed completely over them. The hooks which project into the Salicornia marsh are typical of the whole system of construction of Blakeney Point from the Marams to the Life-boat House. The accompanying 228 BLAKENEY POINT, NORFOLK diagram (fig. 51) shows these lateral beaches numbered in the order of their sequence. They occur in three groups, forming the Marams, the Hood, and the Long Hills and Headland. In length, individual hooks range from a few hundred feet to half a mile, whilst the nature of the vegetation they bear varies according to the age of the hook, or what is the same thing, its position in the system as a whole. Ancient hooks, such as those of the Marams, have acquired by lapse of time a sur- face soil bearing a turfy carpet of grass; those most recently produced bear little besides that most ubiquitous of the Blakeney e )e Y € Cee Fig. 51.—Diagram of the Shingle Systems of the Distal Three Miles of Blakeney Point, to show the separate banks and their order of origin The series 1 to 12 with the enclosed marshes form an aggregate known as the Marams; Nos. 13 to 17 are covered in large part by a sand-hill termed the Hood; the Long Hills overlie Nos. 19 and 20, and the Headland occupies the area within No. 26. Between these two sets of sand dunes is the Salicornia marsh, The last-formed beach (No. 27) is dotted. All the marshes belong to the narrow-mouthed type with the exception of x, y, and z, which are of the open variety. shingle plants, Swceda fruticosa. Between these extremes the Long Hills bank of intermediate age may serve as an example of a transitional vegetation. Leaving the sand-hill which has served as view-point, we may proceed along the edge of the marsh about half-way to the Bend. Walking over the low shingle hooks, it will be noticed that the Suzeda bushes are dwarf and stunted, and, if it is several days since a tide flowed into the marsh, twigs of Suzda will be found lying about. This destruction is caused by rabbits, which throughout the season never relax the habit of pruning the Sueda. In the aggregate, the result of this constant rabbit pressure is tremendous, as the drift line testi- fies. An adequate explanation of this Sueda habit has yet to be found. The rabbits do not eat the twigs, which remain lying about till the tide sweeps them up. It is possible that the rabbits sharpen their teeth this way, or the taste may be pleasant; on the other hand it may be merely a mischievous Plate XNIV Photos. W Rowan Rabbit runs on Salicornia Marsh RABBIT PHENOMENA (BLAKENEY POINT) RABBIT PHENOMENA 229 habit. Sueda fruticosa also grows in quantity on the Chesil Bank in Dorset, and here it is bitten by hares, which travel miles for the purpose. The hare with its greater strength is able to gnaw through quite thick branches, and does not restrict itself to small twigs like the Blakeney rabbits. The Sea Purslane (Odzone) suffers in just the same way, and in some places is mowed down by the rabbits to form a beautiful lawn. It is interesting to note that in colour the rabbit-cropped Suedas are most variable, ranging through green to dull-red and crimson. Suadas, when untouched by rabbits, as on the Marams, show a slight tendency in autumn to assume these various shades, but it is only where they are habitually nibbled that a vivid colour mosaic is a constant feature. The inner cause of the phenomenon has not been investigated. Crossing the marsh some distance to the north of an old steam lighter fitted up as a house-boat (Yankee), and moored alongside the Long Hills bank, the composition and texture of the vegetation can be examined. The marginal zone of the marsh contrasts with the main area in the presence of Obione, Salicornia radicans (a perennial species), and Sueda maritima, and in the absence of Pelvetia. Salicornia annua, which with Pelvetia forms the substance of the marsh, is here only scattered and dwarfed. On the main area the Salicornia owes not a little to the Pelvetia, which nurses it in the seedling stage, and as a mulch prevents drying of the surface during the neaps. By its disintegration much humus is added to the soil and high fertility maintained. At many places rabbit runs crossing the Salicornia are evident (Plate XXIV, lower figure). If followed, they will generally be found to lead across the minor creeks at points where they are narrow, and the footprints left by the rabbits in jumping and alighting are discoverable in the soft mud of the bank. These runs lead to the Sea Asters (now becoming everywhere abundant), upon which the rabbits feed eagerly, and it is rare to find on this marsh an aster quite free from the attentions of these animals (Plate XXIV, upper photo), except in the fenced enclosure hereabouts, which serves to emphasize the effect of rabbit browsing. 230 BLAKENEY POINT, NORFOLK Arrived on the Long Hills, it will be noted that the covering of dunes is more mature than anywhere on the Headland itself. More species of plants have settled in, and the lichens (Cladonias) are relatively much more important in covering the ground. There are also numerous fine clumps of the polypody fern— not to be seen elsewhere on the Point. The main object of the visit to the Long Hills is to examine the southern extremity of the bank. Prior to 1911 the end ran straight out, but during the winter of 1911-12 continued tem- pests from the west destroyed the tip, and re-arranged the shingle as a hook pointing east. This hook is now nearly 200 feet long, and curved like a jetty (Plate XXV, lower photo). Its sudden apparition has disorganized considerably the tidal irrigation of part of the marsh to the east of the Long Hills bank, but its chief interest lies in the fact that its formation explains how the similar curved type of hooks on the Marams arose. These can be inspected on the way back to Cley. The bushes of Suceda fruticosa, now present on the crest of this new bank at its point of insertion, have been derived directly from Suzdas which flourished on the eastern slope of the old bank before the catastrophe. These, when overwhelmed, grew up through the new shingle and took root at the higher level. It is this characteristic, combined with great robustness of habit, that makes Suceda fruticosa potentially one of the most valuable of all maritime plants for purposes of coastal defence, ranking indeed with Psamma itself. The return journey to Cley will be made on foot. Leaving the Long Hills just beyond the house-boat Yankee, a line may be taken direct to the Hood across the sands, or if they are too sloppy, the fringe to the main beach may be followed. The flats on this side of the Long Hills are still for the most part bare of higher plants, except for a thin scattering of Sa/i- coruta annua, now rapidly spreading. The higher parts between the neap and spring high-water marks on the Long Hills side show very typical development of the blue-green alga Micro- coleus, an important accretor of mud. It can be recognized by a tendency shown by the surface layers to flake off during the periods of the neaps in summer. Ifa specimen be examined Plate NNV Us Photo. E. P. Farrow A Samphire Gatherer; the Hood seen on the sky-line L-shaped terminal formed in tg12 on the Long Hills bank. _ Its insertion on the latter is shown. In the distance are the mud flats and waters of the Estuary BLAKENEY POINT THE HOOD 231 in water, it will be found to consist of the matted algal filaments, with soil held in the interstices; and if it be kept moist under a bell-glass, the filaments will emerge like a blue-green velvet on the surface. The Hood is a crater-shaped sand-hill covered with Psamma, Carex arenaria, and in places with the glaucous, tufted, and rather rigid Corynephorus canescens—this last a characteristic East Anglian seaside grass. The general flora of the Hood is richer than that of either the Long Hills or Headland, in conse- quence, doubtless, of its greater age. In the summer of 1910 it was accidentally burnt over, but the grasses quickly recovered, and no ill effects supervened. The Hood stands on a complex of dormant shingle hooks, parts of some of which are exposed on the eastern side. The surface pebbles on their crests show a rich covering of lichens, Buellia colludens (black) and Physcia parietina (orange) being the principal species. In the centre of the Hood is a little bay reached by the highest spring tides, and in this a tiny Juncus maritimus marsh—the only example on Blakeney Point itself. Lying due south of the Hood, and about a quarter of a mile distant in the centre of the Horn Sands, is a newly-developed marsh known as the Samphire Marsh, for it is here especially that the people from the mainland come to collect the Marsh Samphire (Salicornia) for pickling (Plate XXV, upper picture). Up to 1910 this marsh bore only a sprinkling of Salicornias and a few Asters, but during the last few years it has advanced very rapidly indeed, the Salicornias now forming a dense carpet, whilst the Asters are all over the place. Two species of annual Salicornia are present, S. annua and S. dolichostachya. At the earlier date the latter was the more abundant, and this is the species which the Samphire gatherers especially collected. It is distinguished by its long tapering flowering spikes. In 1916, S. dolichostachya had become relatively less abundant, but it would be premature to say that this is the direct result of over- picking, although in view of the plant being an annual the explanation is plausible. It is possible, of course, that this species flourishes best in the early stages of colonization, and 232 BLAKENEY POINT, NORFOLK that the dwindling noted is a normal preparation for the next succession. The marsh is worth inspection, if only to see Fucus limicola in its prime. It may be remembered (see p. 172) that this sea- weed becomes bedded in the mud, and is most active in pro- moting accretion. The vertical growth of this marsh (which is just covered by the neap tides) was found to be approximately 1} inches per annum in 1914 and 1915, whilst the high loss on ignition (8.4 per cent of the dry weight) points to a considerable richness of the soil in humus. Pari passu with the advance of the Samphire Marsh, and doubtless causally related with it, is the colonization of the ground between the Hood and the western bank of the Marams, on which the Watch House stands. Up to 1910 Salicornia was present in moderate amount at the corners where the Hood and Watch House banks, respectively, join the main shingle beach. Since that date the plant has spread much as on the Samphire Marsh, so that now (1917) a broad continuous belt of green here runs parallel to the beach. Only a few years ago this portion of the Blakeney area was notorious for its soft and treacherous mud, the character of which will be appreciated when it is explained that it was considered a good joke on some pretext to get an unsuspicious stranger to attempt to cross the slough. The Main Beach from the Long Hills to the Watch House. —This portion of the beach, though exceptionally rich in Sea Poppy (Glauctum luteum), is, on the whole, relatively poor in the more persistent beach plants, such as Sueda fruticosa, Silene maritima, and Arenaria peploides (Plate X, 1, p. 98). It is divided by the Hood into two sections, very similar in nature and of approximately equal length. Both sections are exposed to the open harbour on the lee (south) side, and when the wind blows from the direction of Morston and Stiffkey, i.e. from the south-west, the waves at high tide disturb the shingle a good deal, and make it difficult for Suceda fruticosa to establish on the fringe. This probably accounts for the almost entire absence of this plant from the middle portions of the two open embay- ments west and east of the Hood. However, since the Samphire SHINGLE DRIFT 233 Marsh off the Hood began to rise in level, the section from the Hood to the Watch House has enjoyed some slight measure of protection, and this finds expression in the establishment of a line of Suada seedlings from the Hood for a distance of several hundred yards in the direction of the Watch House. These seedlings arose from seed ripened in 1912 and left all along the drift line. Originally the line was continuous, but by the summer of 1916 there were a good many gaps. By that time the average height of the survivors, sturdy little plants, was about 18 inches. Should the Samphire Marsh continue to rise, it is to be expected that Suzda seedlings will eventually spread all along this section of bank. Another feature of interest on both these sections is the eastward drift of the shingle along the lee fringe. This results from the south-westerly gales. As a consequence, the shingle tends to accumulate in the western corners of the Hood and Watch House bank, respectively. The accumulation by the Watch House is very striking indeed, forming a marked excrescence which has sensibly in- creased during the last six years. Should it continue, the head of the angle or recess will be isolated as a ‘‘low” when the bulge stretches across to meet the Watch House bank. These corners are also regular traps for vegetable drift (seaweed and Zostera), which is swept up here in quantities from the muds of the harbour. As a consequence, a rich humus soil is formed in which the Sueda bushes luxuriate. The shingle which accumulates to form the bulge represents attrition from the lee face of the bank; it is not replaced by drift from farther west, as the Hood stands in the way, and acts as a natural groyne. The only source from which it can be re- placed is by shingle washed down from the crest by super-tides; whether this in amount compensates for the wastage it is im- possible to say. This same section of beach exhibits occasionally, in common with the stretch between the Marams and Cley, another pheno- menon, viz. percolation ravines. With very high tides the whole top of the beach is gorged with sea water, and at the ebb much 234 BLAKENEY POINT, NORFOLK of this water discharges on the lee side, carving out ravines every few yards, and shooting out the shingle displaced in the form of talus fans on the foreshore. After ‘the high tide of 14th September, 1916, scores of these ravines appeared, resem- bling in all respects except size those of the Chesil Beach. The ravines were developed on the steep lee slope, reaching up about 6 feet from ordinary high-water mark, 2 to 3 feet deep, and 3 to 4 feet wide. A man lying down could get excellent cover in one of these ravines; and, indeed, it might have been supposed that soldiers had been practising some new system of entrenchment. The next high tide was some 2 feet lower than the tops of the ravines, and its effect was to obliterate their lower two-thirds by lateral shingle drift. The upper limb of each ravine, being above the influence of this tide, persisted as an oval hole about the size of a clothes basket. Had one not seen the ravines freshly made, the ‘‘clothes baskets” must have been quite unintelligible. The Marams.—The stretch of beach, a mile long, extending east from the Watch House to Cley beach, is perhaps the most interesting part of the area from an engineering point of view. It is known as the ‘‘Marams”’, though no blown sand enters into its construction. As, however, a few tufts of Marram Grass occur here and there on this section of the main beach, it is quite possible that the name is really significant of the presence here at some remote period of Psamma-covered sand dunes. The great features of this section of the beach are:— (1) The numerous hooks which it bears along the lee side; (2) The advanced phases of marsh building shown by the land between the hooks; and (3) The mobility of the main beach in relation to the distri- bution of the vegetation, more particularly the Suada bushes. The Hooks, which are six in number, are some of them simple and some compound, the latter consisting each of two or three hooks in lateral contact. The relief af the ground makes it possible clearly to distinguish the real nature of these THE MARAMS 235 compound hooks, whilst the interstices are commonly wider at the distal than at the proximal ends. The hook on which the Watch House stands, and the one immediately to the east of it, are good examples of simple hooks; most of the others are compound. The terminals of the hooks are all of them bent round at a right angle, so that they lie east and west. Probably this adjustment has been caused by ancient storms from the west or south-west, just as recently the tip of the Long Hills bank was turned through a right angle in the course of a single winter (cf. p. 230). The result is that the marshes between the hooks are narrow-mouthed, and sheltered from wave action on the south, a condition that must have promoted their coloniza- tion by halophytes and a rapid raising of their level by depo- sition of silt. The hooks of the Marams stand much higher than those which project into the Salicornia marsh of the Headland, and are not covered by any of the spring tides. Except for their ends, which are exposed to some extent to scour from the waters of the harbour, the shingle of the hooks has become stabilized, and carries a continuous vegetation. This vegetation is zoned, the principal zones from below upwards being characterized by Sueda fruticosa, Festuca rubra, Statice binervosa, and the vegetation of the crest. The Suazda of the hooks is continuous with that of the marginal belt of the main beach; its growth, however, is less vigorous on account of the dormancy of the ground. The marsh units of the Marams are the bays between the hooks, each irrigated and drained by its own creek. The height of these marshes is such that they are overrun by the higher spring tides only. Accretion, though still in progress, hardly exceeds } inch per annum. The westernmost marsh of the series, adjacent to the Watch House bank, is a typical ‘‘mixed salting”, bearing most of the commoner perennial halophytes. Its margin, however, has already been invaded by the Sea Purslane (Obzone portulacoides), which plant has become dominant over most of the other marshes of the series (Plate XVI, p. 176, lower). The occurrence of this 236 BLAKENEY POINT, NORFOLK invader everywhere has prevented the marshes entering on their normal terminal succession, wherein broad swards of Glyceria maritima should be the conspicuous element. To find this type we have to look at the higher saltings on the south side of the estuary, outside the diked marshes between Blakeney and Cley. That the marshes of the Marams in their earlier phases resembled the Salicornia marsh of the Headland seems prob- able. Thus, at many spots, surviving vestiges may still be found of the old Pelvetia-Salicornia community. In spite of these various accessory structures, it is the main beach which offers the principal interest in this Marams section. This part of the main beach is mobile throughout, and yet its mobility is restrained by the numerous hooks which act as stabilizing cores, over which it must necessarily progress in its landward travel. This retardation tends to make the Marams section a salient, whilst the close proximity of so considerable an area of marshes provides the lee fringe with a constant supply of vegetable drift. These factors together favour the establish- ment of a fairly rich vegetation, and this in its turn co-operates towards the same result. That is to say, the hooks and the vegetation promoted by the natural manuring by drift act reciprocally in slowing down the travel of this part of the beach. The details of the relation of the distribution of the Suzda bushes to the relief of the beach can be studied under the most favourable conditions along this section—more particularly from a point half a mile east of the Watch House to the east end of the Marams. Fans of talus brought down from the crest to the lee edge project over the marshes at frequent intervals (cf. fig. 28, p. 109), and it will be found in each case that these fans are fed by definite gullies which cross the beach at right angles—passing through gaps in the rows or zones of bushes (Plate XXVI). In several cases recent talus will be found capping older talus on these fans, thus showing that the gullies are permanent lines of transport which function intermittently according to the incidence of the super-tides which top the crest. DAQHA PINISAT PUL ‘Saprozgag VLDUILF ‘SNPOINUDASLAY NIUMN Y WVUNPIADUM auaqas Ole _EPIALL PPPNS Werpy 1ayyoO sjuyjd snonsidsuos arow ayy, ‘sauly oMUBUAP ay} puL ‘sauoZ YPaNg aeayy ay) ‘SUBJ sN]e. WAL (NOLLOGS SINVAVIN) THOVaH NIVIN AGINGUMV 1d 40 UdIsS CUVMCGNYT LAXN 98[d CLEY BEACH 237 Along the eastern half of the Marams the Suzeda bushes run in three distinct zones (Plate XX VI) :— (1) A marginal zone along the lee fringe of the beach; (2) An intermediate zone; and (3) An upper zone. The marginal zone is the one most recently established; it is continually increasing by invasion. It probably dates from 1897, the year of the last very great tidal inundation. Prior to that year the present intermediate zone probably occupied the marginal position, whilst the upper zone dates back to a much earlier period. On this view the two bare intervals of shingle between the zones of bushes correspond to advances of the shingle—the lower one to the tide of 1897, the upper to some previous unascertained date. The general relations of the Suzeda bushes to beach travel have already been fully illus- trated and described at pp. 106-110. It has frequently been stated that the lee fringe is the region of establishment of Suzeda bushes, and this is probably true as to 99 per cent of such cases. Occasional seedlings, how- ever, can and do germinate and establish in other positions— even on the crest itself. Between the Watch House and the end of the road from Cley (a distance of 1} miles) fifty such seedlings have been detected, and there is little doubt this number would be indefinitely increased did natural processes continually operate in distributing broadcast the seed and the drift. The Cley Beach Section.—Continuing east from the Marams the beach becomes bare and very mobile, the crest is uneven and liable to be overrun by the highest tides. Whenever big seas and big tides come together it is Cley Beach that suffers first, and much shingle is transported to the lee fringe, where it is shot into the channel. It is within the memory of by no means the oldest inhabitants that there was formerly a consider- able strip of saltings between the beach and the channel— perhaps 50 feet wide. This has long disappeared through the landward travel of the beach, and now every ton of shingle washed over finds its way direct into the bed of the channel, 238 BLAKENEY POINT, NORFOLK so that the discharge of the tidal water is retarded and navigation impeded. Proposals have recently been made to dig a new channel through the saltings some distance to the south of the existing one, an expedient which has much to recommend it. At the same time, for such an enterprise to have lasting value it would be necessary to plant up the beach itself; otherwise the new channel would be overtaken in a few years and the present position reproduced. The principal features in the relief of this section of beach are the gullies along which shingle is transported and the percolation ravines. Talus fans occur at the ends of the gullies after a big tide, but do not persist, as the scour of the channel soon distributes the shingle along the bed. At the point where the telephone poles turn landwards is the causeway to Cley, which is distant a mile from the beach. Just west of this point the channel turns south and runs between saltings to the same destination. Actually, the causeway lies east of the bank, which protects from the tide the marshes between Cley and Salthouse. Except for wheeled traffic the usual road is along the flat top of the dike, and this is to be recommended for its extended view. The mainland from Stiffkey to Sheringham is visible; the Harbour from the Life-boat House in the west to the reclaimed marshes beyond Salthouse; whilst the land about the ancient head of the estuary, which ran below Wiveton Church up to Glandford, lies beyond Cley windmill, which stands near where the bank joins the mainland. It will be noticed that the tidal saltings are some two feet higher than the reclaimed marshes within the bank. This difference is due in part to a slight settlement undergone by the latter after isolation, but chiefly to the continued accretion of the saltings, which are, of course, covered by all the higher spring tides. (Cf. Plate XXVII, lower photograph.) In Cley village many traces still remain of former maritime activity. The channel by the old staithe has shrunk away almost to nothing, but the old Custom-house remains; whilst facing the George Hotel is the end of what was a long row Plate ASVU Cley Beach, showing outcrop of floor of Salt Marsh (seatea figure) over which the beach has travelled. On right wrecked S.S. Fev, beached after collision with a MAINe-SWee per Sea-wall near Cley; Tidal Salt Marsh on left, reclaimed Blakeney Marshes on right. Note that level of former is higher than the latter BLAKENEY POINT CLEY MARSHES 239 of granaries, now converted into cottage tenements and a Village Institute. Cley to Weybourne.—The sea frontage east of Cley Beach and the marshes behind are well worth inspection by the engineer, on account of the inroads which the sea has made into works ambitiously conceived but inadequately maintained. A visit is most conveniently made by following the coast road east from Cley to Salthouse, and then crossing the marshes by the road which leads to the Rocket House opposite Salt- house. The round is completed by returning to Cley via Cley Beach. On leaving Cley by the Sheringham road the south end of the east bank (with stile) is passed just beyond the last house on the left, and a few yards farther on the causeway (gate) leading to Cley Beach. The road now skirts the reclaimed marshes (Cley Marshes). Five furlongs farther on a bank parallel to the last leaves the road; these two banks and a connecting wall on the front parallel to the beach protect the Cley system of reclaimed marshes. This intake dates from 1790. For a period of fifty years from this date it was possible for a boat to sail at high tide from the Cley channel at the bend between the main beach and the bank; access was thus gained to Salthouse Broad, which lay to the east of the Cley Marshes. About 1845 this entrance was closed by the advance of the beach (cf. fig. 49, p. 220). Some 500 yards east of the second bank, at a point one mile from Cley, the steep bank or bluff to the south of the road should be ascended. From this point a wide prospect of marshes is obtained closed in to the north by the Salthouse sea-wall, built in 1851 at a cost of £10,000, to exclude the sea from the Salt- house Marshes (including Salthouse Broad). This wall, as will be seen, has been broken at numerous points and has never been repaired. The view-point itself has also an interest. The soil and the plants thereon proclaim it an ancient sand dune. This means that long ago, before either the marshes or the shingle beach existed, the open sea washed the foot of this bluff, and brought the sand which was blown by the wind into its present position. 240 BLAKENEY POINT, NORFOLK Continuing along the road, past the ‘‘Dun Cow”, the wind- mill and village of Salthouse, a causeway leads across the marshes to the conspicuous Rocket House. All along this front to the corner of the Cley Marshes are the remains of the sea-wall of 1851. This wall, 2 miles in length, has been over- taken by the beach, which now lies piled up against it for a large part of the distance, and at many points is level with the top of what remains, and running over. The sea-wall is breached at numerous points, and no section over 100 yards in length remains intact. The gaps in the wall have been produced by the sea washing over the crest and eroding the mud, whilst at some spots when the marshes were in flood the wall has been undercut by scour from the south side. With the deepening of the gaps the sea began to wash the shingle through, spreading it out in the form of circular detrital fans standing about 2 feet above the marsh level. Thus, too yards east of the Rocket House, a 20-foot gap has admitted a level detrital fan 100 feet across (north to south) and 100 feet wide (east to west). The height is approximately 2 feet. Opposite the ‘‘ Dun Cow” at Salthouse there is a very broad breach with fan to correspond. In 1913 the surface of the latter was beginning to be colonized by Horned Poppy and Dock. About 400 yards farther west, opposite a pair of drains crossing the marsh, a breach was just beginning, and pebbles were already drifting over the gap. At one place a number of breaches occur close together, and much shingle has drifted through them. The lines of flow are marked by gullies like those in percolation ravines, whilst shingle is deflected and accumulates under the lee of the surviving wall fragments, reaching a height of perhaps 4 feet, and recalling the relation that obtains between a Psamma tuft and the ‘‘ tail” of sand that accumulates under its protection. In the case of the Psamma the agent of transport is wind, whilst the shingle, of course, is carried along by water. The areas of marsh covered by these detrital fans are lost for grazing, whilst the gaps have to be fenced to prevent cattle straying on to the beach. 1 These dimensions were noted in March, 1913. The damage may have increased since that date. CLEY MARSHES 241 The general consequences of the neglect of the Salthouse wall are:— (1) The frequent flooding of the marshes, which renders an appreciable proportion of the total area unproductive. (2) Increasing areas of the marshes destroyed by the intrusion of shingle. (3) Choking of the drains with flood water, thus aggravating the congestion in the obstructed Cley channel where the main drain discharges. The phenomena presented in the course of a walk along this front are decidedly instructive, and will thoroughly repay the trouble. The Cley Marshes present a different problem. The wall has never been allowed to fall into disrepair, but trouble has arisen because the north-eastern corner has developed into a salient owing to the advance of the beach. This salient is pro- jecting more and more out to sea, and the wall (concrete) is liable to damage from storms, entailing great expense in upkeep. It is probable that the position will in time become untenable, and that the wall will have to be set back and the salient aban- doned. Along this part of the beach, about the high-water mark of the neap tides, the old marsh floor can often be detected on the sea front (Plate XXVII, upper photo). The beach has passed right over it, and fragments of peaty material containing residues of plants break away as the layer is eroded by the waves. The same thing may be found at other points between Salthouse and the Marams Watch House, when the shingle on the face has been temporarily washed down to a lower level. Cley can be regained by continuing west along the sea-wall to the causeway on Cley Beach, or the bank between the Cley and Salthouse marshes can be followed to the Sheringham road. (0 924) 17 CHAPTER XIII The State and Local Control A vast literature has been evolved on every aspect of the question of coast erosion. In 1906 a Royal Commission was appointed, and their third and final report was not issued until five years later. The subject was investigated by them in an exhaustive manner, the commissioners visiting the coast-lines of England, Scotland, Ireland, Holland, and Belgium in the course of their enquiry. The references to the Royal Commission in- cluded :— (a) Facts relating to the encroachment of the sea; damage caused or likely to be caused thereby; recommendations as to preventive measures. (6) The advisability of conferring further powers on local authorities and landowners, with regard to securing more effective administration in the work of protecting the open coast and the banks of tidal rivers. (c) The legal situation with regard to the management and control of foreshores; recommendations as to modifica- tions in existing law. (d) Facilities, if any, which should be given for the reclama- tion of tidal lands. The final report dealt with the subject in the following aspects :— (1) Topographical and geological considerations. (2) The extent of erosion as compared with accretion and artificial reclamation. (3) On the technical evidence given before them. (4) Regulations relating to central and local administration. 242 CROWN LANDS 243 (5) The reclamation of tidal lands, and the use of unemployed labour in effecting such reclamation. (6) The alleged obligation of the Crown to defend all fore- shores. The contention that inroads of the sea are to be regarded in the same light as the invasion of a foreign power, and that, therefore, it is equally the function of the State to take preven- tive measures in the two cases, is doubtless theoretically sound, but the difficulty presents itself that there are no means of en- forcing. decisions. The Crown claims ownership of the strand between high- and low-water levels, and legal decisions confirm this view. Inversely, however, the Crown is not answerable to the jurisdiction of any court, and its default of duty cannot be made the ground of action, except by petition. It is obvious, therefore, that no binding right can be established by which the cost of sea defences can be thrown upon the State. The fundamental question is in effect one of meum and tuum. Who is to foot the bill? The contention on the one side is that, as the defence of the shore is legally a State matter, the private owner should be relieved of its cost. On the other hand, it is urged with reason that the owner of seaside lands in the majority of instances has purchased such lands at a capital figure based upon the risk of incursion, both buyer and seller being aware of the possibility of such inroads recurring. The same argu- ment in a somewhat lesser degree applies to throwing the obli- gation of maintenance on the particular county affected. The landowner 20 miles from the seashore asks how it can be con- sidered equitable that a scot should be levied on his land in order to provide funds for safeguarding the estate of his neigh- bour 20 miles away? Up to a few years back the legal situation was somewhat chaotic. Under the Crown Lands Act of 1866 the management of most foreshore lands passed from the Commissioners of Woods and Forests to the Board of Trade. Up to this date the removal of shingle and sand from the foreshore by authority of the lord of the manor went on almost without let or hindrance. It was often a highly profitable privilege, and the lord of the 244 THE STATE AND LOCAL CONTROL manor, having been undisturbed in the custom, legal prescrip- tive right was asserted, overriding any hypothetical claim of the Crown to exercise jurisdiction. The late Lord Farrer (then Sir Thomas Farrer), in a memorandum to officials of the Board of Trade, was careful to explain that the rights of the Crown rested on a somewhat doubtful assumption, and that, in the assertion of those supposed rights, great caution must be exercised to avoid possible litigation. The subject is now ripe for statutory action, and the recom- mendations of the Royal Commission are available as the basis of such legislation. Within the ambit of this handbook their principal recommendations are as follows :— 1. On the subject of accretion and depletion as affecting title, the law to be amended so as not to deprive the Crown of accreted ground where there is well-defined ascertainable boundary to the land of a contiguous owner. 2. That the Board of Trade should have the sole adminis- trative control of foreshores. 3. A clear right of passage by foot along the foreshore, subject to the control of the Board of Trade, is recommended; and, in respect of the rights assumed to exist for bathing, riding, driving, collecting seaweed, &c., it is suggested that the Board of Trade should be given executive authority. 4. On the wide question of the executive administration and active maintenance of the foreshore the Commission quote in summary the suggestion for creating ad hoc authorities. This scheme made provision for the division of the coast-line into districts,1 each district being administered by bodies of County Coast Commissioners and a district engineer or coast warden, whose recommendations would be subject to the central control of a chief engineer under the egis of the Board of Trade. A scheme of equitable division of the cost of shore works was also evolved. Other recommendations were for placing practically com- plete control in the hands of the respective County Councils. The report of the Commission is in favour of making the 1 “Memorandum with regard to the Proposed Creation of Coast Commissioners” (A. E. Carey), Appendix No. XVII. SEA DEFENCE AUTHORITY 248 Board of Trade the central authority in respect of coast protec- tion, giving the Board jurisdiction over— (1) The removal of shore materials; (2) The construction of works on the shore; (3) Assistance where necessary in respect of supervision of existing authorities concerned with coast protective works, and the creation of new authorities in particular areas where found to be desirable. (4) The Commissioners recommend that the Board of Trade should be ‘‘equipped with expert engineering advice, and that provision should be made by the Board for establishing suitable arrangements for the watching of the coast”. The Board of Trade would under these recommendations be constituted the sole Sea Defence Authority of the Realm. In respect of monetary assistance, the following is the finding of the majority of the Commission :— “With regard to the borrowing of money for sea-defence purposes by existing local authorities, including Commissions of Sewers in England and Wales, or by new sea-defence authorities to be formed by the Board of Trade, we recommend that the State, as represented by the Public Works Loan Commissioners in England and Scotland and by the Commissioners of Public Works in Ireland, should be empowered in suitable cases and with proper conditions to adopt the policy of making loans for sea-defence purposes on the security of the rates, where the credit, in the opinion of the Public Works Loan Commissioners or the Commissioners of Public Works in Ireland, as the case might be, was good. ‘We think that it is undesirable that the supervision of the financial transactions of local sanitary authorities, at present exercised in England and Ireland by the Local Government Boards for those countries, should be taken away from those Boards. We, however, recommend that, in fixing the periods of repayment of loans for sea-defence purposes, those Boards should accept and act upon the report of the Board of Trade with regard to the design of any proposed sea-defence works for the purpose of which a loan is being raised, and also with regard to the probable life of such works. It is desir- able to avoid as much as possible two separate inquiries in these cases by the Board of Trade and by the Local Government Boards. Moreover, the practice of the Local Government Board for England of allowing not more than ten years as the period of repayment of loans for groynes, and twenty years for solid defence works, appears to us to operate detrimentally in the case of many local authorities.” They further state: ‘‘We are not prepared on the evidence laid before us 246 THE STATE AND LOCAL CONTROL to recommend that there is any case for going further and for making grants from public funds in aid of sea defence. . . . We cannot see that there is any ground for the contention that sea defence is a national service; it is true that there is serious érosion in places, but this erosion does not affect the nation at large.” If statutory effect is given to this last recommendation it will afford but poor comfort to many harassed sea frontagers. They have in effect asked for the bread of material assistance, and will be offered the stone of departmental supervision. In the main the recommendations of the Commission amount to little beyond a delegation of authority. It is obvious that any organized system of administration must, in the interest of the State, be under the control of a State Department, the head of which is responsible to Parliament, and the Board of Trade is pre-eminently the most appropriate public authority in this connection. There is probably no department of the State which is administered with greater efficiency and absence of red-tape restrictions. All those brought into contact with the Harbour Department of that Board recognize the efficiency of its control. At the same time, the Board has at present no organized administration for dealing with the extremely varied functions which would attach to the detailed supervision of the national coast-line. In the manage- ment of every facade of seashore knowledge of local conditions is essential, in combination with special expert experience. The following sequence of events has some bearing on this point. At Hallsands (Slapton Sands), Start Bay, the cliffs and houses were fronted by a beach 150 feet wide, a width of 60 feet of which was from g to 14 feet above high-water level. Sea- walls were constructed in 1841, and the beach afforded an effective barrier against inroads of the sea. It is readily demonstrable— (1) That local conditions of coastal stability had been long- continued ; (2) That any depletion of the protecting medium of defence could not be made good by natural agencies; (3) That the balance of littoral drift was circumscribed by the Bay, and did not pass either horn of the same. HALLSANDS 247 Fig. 52.—Hallsands—Wilson’s Rock Fig. 53.—Hallsands—Northernmost House 248 THE STATE AND LOCAL CONTROL In 1896 Sir John Jackson entered into a contract with the Board of Trade, by which his firm was permitted to dredge sand and gravel opposite Hallsands for the purpose of construc- tions in Devonport Dockyard. Some 650,000 yards appear to have been removed. In 1go1 the sea-walls at the south end of the village were undermined, and the beach level was found to be reduced 7 feet in height. At Wilson’s Rock the correspond- ing reduction in height was 12 feet. In the following year the sea-wall fell, and by definite stages the wrecking of the coast-line progressed. The coup de grace to the entire hamlet of Hall- sands was given ina violent north-easterly gale in January, 1917. It will thus be noted that, under the specific authority of the Board of Trade as now constituted, authority was granted to carry out operations, the effect of which was for practical pur- poses the destruction of a coast-line of immemorial stability. Plate XXVIII and figs. 52 and 53 illustrate the sequence of events. Plate XXIX, the reproduction of a photograph of Hall- sands taken in 1917, shows the fifth act of the tragedy and the logi- cal sequel of organized denudation under departmental control. Speaking broadly, Commissioners of Levels and Sewer Commissioners are bodies whose functions are exercised, without pay or recompense, by country gentlemen. Their procedure may be in some instances antiquated in form, but public affairs in their hands are, in the vast majority of cases, administered with economy and fairness. In spite of many notable instances to the contrary, small corporations and urban district councils have not proved themselves ideal instruments of government. Men of administrative capacity are apt to hold themselves aloof from their deliberations. It would be distinctly a retrograde step to increase the power of the urban authority at the expense of that of Commissioners of Levels. In Appendix No. VII, p. 274, is given a list! of the Commis- sions of Levels and of other authorities who exercise statutory control over foreshore lands and lands liable to tidal flooding, and in the case of those marked (*) their jurisdiction abuts on the sea-coast. These authorities, however, have jurisdiction only over 1See Appendix XLIV of Report of Royal Commission on Coast Erosion. Plate NNVIL HALDLSANDS IN 1894 After R. Hansford Woith HALLSANDS IN 1go04 The two pictures are from the same view-point, and the state of the tide is the same in both. By 1904 the beach had fallen about to feet COMMISSIONERS OF LEVELS 249 isolated fragments of the foreshore. Corporations and Urban District Councils also exercise a limited control over consider- able frontages, but, eliminating the areas of local and restricted authority, there still remain great stretches of tidal and coastal facades which are left under no effective supervision. The poorer agricultural and town districts are the most neglected. The effect of this sporadic system of control is an unscientific frontier, defended in patches merely, alternating with unguarded stretches of coast-line. Thus while a township or particular estate may be carefully fended against attack, it is frequently liable to outflanking by the erosion of contiguous properties to leeward of it. It is admitted on all hands that present methods of administration need overhauling. In England and Wales, in addition to the Commissioners of Sewers appointed under the Crown, there are elective Drainage Boards constituted under the Land Drainage Act of 1861, and under private Acts of Par- liament other similar bodies of Commissioners have been nomi- nated or elected. Harbour authorities in many cases exercise jurisdiction, as well as county and borough councils, and urban, district, and rural councils. The present necessity is for an organization which will link up all these various disjointed authorities and give them co-ordinate and collective control. The powers of Commissioners of Sewers mostly date back to 23 Henry VIII. That Act has been varied by five subsequent Acts. Under the Land Drainage Act of 1861 powers are provided for the main- tenance and improvement of existing works and the construction of new works. A tract of uncontrolled frontage can, however, only be brought ‘‘under commission” by the consent of two- thirds of the landowners affected. The procedure of Commis- sions of Sewers varies in different localities. Their general borrowing powers fall under the sanction of the Board of Agri- culture and Fisheries. In some cases orders to ensure current repair are made on the respective landowners concerned, who are directed to carry out the works specified under penalty for default. On works of small cost the penalty is usually double the estimate; for works exceeding £20, 50 per cent in excess of such estimate. The Commissioners meet periodically; in most 250 THE STATE AND LOCAL CONTROL cases they are represented by a professional engineer, on whose ‘‘presentments” the Court orders are issued. One or more Marsh Bailiffs hold office, and the duty of these officers, who are resident in the area affected, is to make constant inspection and supervise the execution of orders of the Court. If organi- zations similar in procedure to these Courts could be extended over all areas affected by erosion, and some measure of con- certed action devised, it is safe to predict that the coast erosion problem would disappear. The bane of the elected authority is inefficient compromise in the face of obstruction. In many cases obvious requirements have thus been contested until disaster impended. The plea usually put forward in these cases is that of economy. It is frequently an economy of the inverted type. Scattered up and down the coast-line are many local authorities whose actions are models of business-like administration, but it is safe to say that, speaking broadly, government by Com- missioners of Levels is at the present time the most efficient form of control in respect of a threatened coast-line. In some cases the Commissioners of Levels themselves carry out the necessary defence works, and either charge the cost of the same on the individual landowner concerned or allocate the collective cost by scot over the entire level fro ra/@ on the areas of occupation. To a large extent this is a matter of custom. Probably the most economical arrangement is for each body of Commissioners to institute a works department of its own. Commissioners have skilled men in their employ, and are able to buy materials and secure the necessary plant more economically than the indi- vidual landowner. On the other hand, the landowner is gene- rally the employer of agricultural labour, and can carry out orders economically in the off seasons. Where the present system works smoothly, the principle guzefa non movere would appear to be the soundest. There is no doubt that the districts controlled by the Commissioners are in some cases badly de- limited, and that a reorganization of the whole system would be desirable. All who have had practical experience of the working of coastal bodies will agree that, as a broad principle, the government by country gentlemen compares favourably with that of elected town bodies. , fJOUL UO SpUL}S BUO}S JUO OU JEL vas oY Aq parowiar A[aitjUa OS UdIq aALvY YYW Sasnoy aUulU JO says ay} SApNpoU! AralA OUI V]fEN}ov suIMI dy} 0} UONIPpR UT,, :spuvsT[VP jo ydvsSojoyd styy YW ajou Surmoyjos ayy saywojuntuuios YOM Plojsavy “PT 4161 NE SANVSTIVH NIXN 9d LOCAL CONTROL 251 It is eminently desirable that the operations of local bodies of control should be under the zgis of a central authority, to counteract the more parochial view of the duties of governance. The whole situation is very similar to that of a campaign, in which each individual unit has to be controlled and directed by the general staff, which alone is able to co-ordinate the com- bined chain of defence. Reverting to the question of how the cost of foreshore works is to be met, and the collective apportionment of such cost, the Coast Erosion Commission has, as already stated, reported in favour of making the Board of Trade the Central Authority, and of giving the Board power to provide expert advice in London and locally. Their report carries with it in principle a recom- mendation that the State should pay what may be termed the head-quarters staff and its immediate delegates, in this case the coast wardens. By slightly extending this liability to cover the cost of requisite plant, the necessity of the case would probably be met. The defence of a threatened line of coast is surely a matter toward which a moderate contribution from the funds of the County Council concerned might be properly applied. A sound rule would appear to be that the County expenditure should be limited, say, to a halfpenny rate. The balance of expenditure might very fairly be thrown on the townships and owners (whether individuals or companies) of the affected frontages. One subsidiary source of funds might fairly be tapped. The feudal system under which, when an estate changed ownership, a defined percentage of the purchase price was payable to the overlord, would appear to be a sound one in this case. The principle is similar to that of succession duty on demise. Prob- ably if it were a standing rule that, whenever an estate on the threatened area (not being town-land) was sold, 2} per cent of the cost of purchase should be paid to the Coastal Defence Fund, such dole would not press unduly on the individual owner. Speaking generally, the sound policy would appear to be:— Local Control.—1. To strengthen and, where necessary, re- form the operations of existing Level Commissioners and re- adjust their areas of control. 252 THE STATE AND LOCAL CONTROL 2. To make provision for the effective control of the opera- tions of Corporations and Urban and District Councils, so that all parties may work in harmony. Central Control.—To organize a system of delegation of control on the following basis:— aut BOARD OF TRADE (Sea Defence Authority of the Realm). Executive Control. Administrative Control. Advising Engineer or County Council Committees Engineers. (say 5 members on each). | Coast Wardens. Commissioners Harbour Corpora- Frontagers. of Sewers. Authorities. tions. The powers which would have to be conferred on the united horities, central and local, would include the following matters :-— sur 1. To take observations, keep records, make inspections and veys, and public reports, plans, and other documents, for the collective guidance of coastal authorities. 2. To make by-laws, subject to the sanction of the Board of Trade, for the following purposes :— (a) Preventing, restricting, and regulating the removal of sand, shingle, and other materials; (6) Regulating the draining of lands contiguous to the coast- line, and as far back as may be necessary to prevent injury to the cliffs or seashore; (c) Controlling the design and construction of any works for protecting cliffs or seashore; (@) For any other purposes which in the opinion of the Board of Trade may be necessary for the due protec- tion and maintenance of the seashore and coast-line, whether above or below high-water levels. 3- To enforce such by-laws as may be approved by the BY-LAWS 253 Board of Trade, and take proceedings for any offences in respect of such by-laws. 4. With the sanction of a provisional order of the Board of Trade, confirmed by Act of Parliament, to make, maintain, remove, or alter any works designed or executed for the protec- tion of cliffs or the seashore, whether above or below high-water levels, and to formulate such conditions as will permit of the removal and transfer of surplus shingle or other materials where the surplus exists to another part of the seashore where the same is depleted. 5. To promote Provisional Orders for obtaining power to execute works, acquire lands and interests in lands compulsorily, appropriate lands reclaimed by means of coast protection works, and exercise control over a coast-line and such works within the coastal area as are affected thereby. 6. To promote and oppose bills in Parliament dealing with matters which may affect the interests or fall within the purview of the Coastal Authority. 7. By agreement with owners or local public authorities, or under powers of Provisional Orders, to plant and develop vegetation on cliffs or a seashore, whether above or below high- water level, and arrange for the cultivation and fertilization of the same, and of any coastal or tidal lands which may be thereby reclaimed. 8. To employ engineers, coast wardens, and other officers whose services would be required to carry into effect the objects of the Act. g. To devise and carry out experiments in protective and reclaiming procedure, and establish such experimental stations as may be deemed by the Board of Trade expedient, in order that the protective function of shore plants and their value in respect of land reclamation and maintenance may be investi- gated, and also to empower the publication of reports or detailed information which may be of public service in connection with the coastal or riparian regime. 10. To buy by agreement, or make provision for the recla- mation of tidal or coastal lands, or lands useful or necessary for the purposes of coast protection, or such lands as in the 254 THE STATE AND LOCAL CONTROL opinion of the Board of Trade fall within the scope of a scheme of reclamation, or be improved in value by reason of the ex- istence or in the event of the construction of coast protection works. 11. To hold, lease, sell, or otherwise deal with any land acquired or reclaimed under the operations of the Act. 12. With the sanction of a Provisional Order to enter into and carry into effect agreements with landowners or local public authorities for loans from the Public Works Loan Commis- sioners, or which may be subscribed by the public, or grants of money made by the Treasury, either as capital or annual payments, by way of contribution towards the cost of any works for coast protection to be executed by such landowners or public authorities under the direction of the Board of Trade. Funds.—1. Funds voted by Treasury. 2. Grants (for capital expenditure) from the Development Commissioners. 3. Grants (under authority of Provisional Order) for either capital or current expenditure from local public authorities, companies, or persons. 4. Rates or scots on owners of property in defined areas benefited by particular works. 5. Precepts on county funds, but such precepts not to ex- ceed a total rate of 4d. in the £ on the rateable value of such county. 6. Loans (for capital expenditure) from the Public Works Loan Commissioners, secured pro rata on the rates of the local authority concerned, or on the credit of the landowners, whether companies or individuals. 7. Income from investments representing capital grants or other capital moneys. A concrete instance of successful combined action is fur- nished in the Report of the Royal Commission. Under the Newhaven and Seaford Sea Defences Act of 1898 provision is made for a combination of local authorities, public companies, and private persons for the purpose of sea defence. The Com- missioners appointed under this Act are a body corporate with perpetual succession and power to purchase and dispose of land NEWHAVEN AND SEAFORD 255 and other property. It is noted in the report of the Commis- sion that the scheme has worked with complete smoothness. It thus constitutes an excellent object lesson in the combination of interests which is essential in dealing with a composite prob- lem such as that of coast erosion. Summarizing the situation, it may be fairly maintained that:— 1. It is admitted that the State has an exceptional duty to the owners of land contiguous to the sea, whose land is liable to its invasion. 2. The counties concerned cannot fairly adopt the policy of benevolent neutrality towards the lands threatened by irruption of the sea, as to do so would in many instances be to risk far- reaching damage to inland tracts, which in their turn would suffer if the sea broke through. 3. The municipalities bordering on a coast-line often find themselves heavily burdened by taxation to maintain their frontage intact, and it would certainly appear to be equitable that they should be parties to any concerted action in respect of defence. 4. The individual landowners or land-owning companies are in many cases in an even worse plight than corporate bodies, and, as a result, the property they own frequently drifts into a half-derelict condition. The declension of good agricultural land to prairie is a matter of prime importance to the community. It is patent to all the world that new problems and fresh methods of governance are opening out in every department of human activity. Old methods of meeting difficulties are being tacitly abandoned. New ideals are fermenting in all regions of British activity. Under the compulsion of world changes, modern England cannot be content indefinitely to traverse routes that sufficed for former generations. It is in the adoption of the principle of corporate responsibility that the problems of the future will have to be faced. CHAPTER XIV Complementary Problems The death grapple of a world war has modified many ideals and rendered obsolete panaceas springing from a national creed of lazssez-faire. Great Britain is the microcosm of the world. Her home resources of coal, iron, salt, stone, fireclay, and other earth products, combined with a virile population of ordered industry and her unrivalled system of harbours and sea inlets, gave her a long start in the race of commercial supremacy. The collapse in agricultural output, and the consequent shrinkage in the value of rural lands following on the theories of the Manchester School, accompanied, as they necessarily were, by a rapidly progressive increase in the importation of food and other essentials of life, and also in the number of unemployed in the Homeland, constituted an economic revolution of far- reaching effect. In this connection the problem of water-trans- port facilities, both overseas and coastwise, has loomed pro- gressively insistent. Great Britain led the world in a sequence of industries. She was the first to perfect her system of roads. She then led the way in the provision of water carriage by canal. Railway connection, having its inception in England, boomed there, and she became the nurse of similar undertakings in other countries. Lastly, mechanical road traction has been perfected by her. In every link in the chain of development she has been more quickly overhauled in the race by rival nations. The old days of ‘‘rest and be thankful” are at an end. An improvement made in any country becomes speedily the common property of the world, to be reproduced in remote corners of the earth, An American motor-car traversing a 256 WATERWAYS AND HARBOURS 257 native-built Chinese road is typical of the trend of economic change at the present day. In one field Great Britain has, however, hitherto assumed and retained her supremacy, namely, that of shipbuilding. She has lagged behind her competitors in the volume of production in many departments of prime industrial importance. In spite of the fact that she has held the reins as the banker and com- mercial exchange centre of the world, she has been eclipsed in some directions by her own sheer inertness, whole classes of manufacture which she originated having been let slip by her. In some quarters she has to learn to reverse her Victorian policy of masterly inactivity. War has revealed the inevitable path of ordered change. It becomes increasingly obvious that many treasured trade traditions must float away in the smoke of battle. By combined effort the State, organized Capital, and organized Labour must march together in the acute problems of the future. Amongst these problems none takes precedence of that of national waterways and harbours. How are these to be organ- ized so as to render most vital service in coming emergencies? The efficiency of a great arterial system of waterways is largely an index of commercial progress. This is essentially true in a congested country such as England. A few years ago belated proposals were put forward for bringing back the canal system of this country to its ancient position as universal carrier. It is now pretty widely admitted that the minor canal in England has more or less had its day. The railways have practically monopolized the means of transport, and canals serve in the main as feeders to the railways. Even this hybrid condition of things probably will not persist. In a certain restricted num- ber of cases, and in respect of certain minor trades, where delay in the transit of goods is of lesser importance, the older canals may continue partially to serve their original purpose. - The substitution of steam, petrol, or electric motor traction would probably necessitate heavy expenditure in the recon- struction of the banks of those designed for slow horse traffic. The ship canal is a proposition of a totally different character. It is probable that schemes for the creation of inland ports and distributing centres will become more insistent. Such towns (0924) 18 258 COMPLEMENTARY PROBLEMS as Colchester and Norwich may be instanced. Where physical conditions are favourable, and the cost of cutting a deep-water canal to a great industrial centre is likely to be low, projects for creating such facilities will certainly demand attention. Canals such as those for connecting the Clyde and the Forth will also doubtless come to the front, not only by reason of trade con- ditions, but on defensive grounds. In the matter of fishery harbours the State has come to the aid of many localities, assisting local endeavour by grants and loans. Closely connected with these problems is that of the official control of the foreshore. Matters will probably not be allowed to continue much longer on their present haphazard basis. The report of the recent Royal Commission was of a somewhat hedging and tentative character, reflecting the pre- war attitude. The upheaval of idea and method which -has resulted from war expenditure will upset the more timorous notions of the past. A national policy to be of value must be fundamental and to some extent run risks. In this connection the many problems attacked in this book will doubtless seek solution. It is obviously impossible to carry out a successful campaign on a large scale, with the object of tuning up the waterways and tidal reaches of the countryside, without syste- matic investigation. The vested interest of an inland trade centre may be best served by carrying deep-water facilities to that centre. In many instances the reverse is the case. Counsel fighting in the committee rooms over such issues constitute a poor substitute for the patient, trained, and organized investiga- tion of a scientific public authority. The trade of London is a case in point. This is fast changing in character. The manu- factures which have hitherto centred in the Metropolis are being rapidly decentralized, and the outflow of these manufacturing trades is. being spread over inland districts. Thus the domin- ance of railway transport tends to increase. The character of inland ports varies greatly. Of the trade of London about 74 per cent of the goods are lightered ex ship to warehouse. The cheap tidal transport of goods on the Thames and its vast facilities for lighterage traffic have in the past rendered London a cheap port for the bulk of the com- PORT CONDITIONS 259 modities to be catered for. On the other hand, on ships enter- ing the London docks charges have been excessive. A costly programme of works has been initiated by the Port of London Authority with the object of deepening the river and bringing the upper docks up to date. It is highly probable that a well- devised scheme under which deep-water traffic would have been concentrated in the lower reaches of the river, where deep water naturally exists, could have been evolved, the transport by lighter to warehouses and upper docks being left undisturbed. Thus economy in distribution would have been realized and vast capital expenditure avoided. However, the transfer of the docks to State ownership and the creation of the Port of London Authority have taken place, and expansion of the trade has so far kept pace with and thus justified the changes effected. Liverpool is in a totally different position. There the traffic is in the main that of vessels of great tonnage, and the goods are handled direct ex ocean-going ship to warehouse. The vast increase in recent years in the shipping facilities of Southampton demonstrates how all-important physical con- ditions are in determining the type of shipping accommodation which it is desirable to provide. The latest addition to that port was that of a deep-water basin having a total frontage of 4637 feet and a depth alongside at low water of qo feet. The principle of deep-water quayage has, by its construction, been confirmed. The peculiar tidal conditions existing at Southamp- ton, and the unique shelter due to its geographical position in regard to the Isle of Wight, have largely shaped its develop- ment. The tidal conditions at Southampton are such that at spring tides the tide, after ebbing at the rate of about 3 feet per hour to its lowest point, at once commences to rise at about the same rate. At high-water level it is practically stationary for about three hours. The double tide in Southampton Water is the result of the travel of the tide, passing first round the north- western shoulder of the Isle of Wight, and then round its north- eastern shoulder, thus encircling the island and causing a meet- ing of the consecutive floods and effecting a welling-up of the water at Southampton. The facilities of the port are thus almost unique. 260 COMPLEMENTARY PROBLEMS If a public body constituted ad hoc took in hand the control of foreshores and tidal waters for directional purposes, continuity of policy and definiteness of aim should be achieved. To form these interests into an extension of an existing department, how- ever well administered such may be, might result in an accentua- tion of existing difficulties rather than in their elimination. Such a department has in the long run to depend on the chance advice of inspectors appointed, as occasion requires, for par- ticular enquiries. Thus it often comes about that a railway engineer, or an engineer whose experience has been in some entirely different channel, has to advise the department on intri- cate physical questions in reference to a locality which he has but casually visited. What is to be aimed at is to build up a bureau which would be in a position to amass all the necessary data, to study them steadily and in sequence, and to deal with any individual problem which may arise as an organic unit in a comprehensive scheme of coastal economy. The sporadic method of disposing of difficulties leads to many complications, not the least being that conflicting and irrelevant local issues often loom far larger than their value justifies. The rule ‘‘what’s best administered is best” is after all in many direc- tions a golden rule. Indiscriminate land reclamation has frequently ruined good waterways. Over and above the training of waterways, the prevention of flooding, the maintenance of outfalls, and the inning of lands contiguous to tidal waters, there are questions of research which will probably have considerable bearing on future issues. Thus the question of the utilization of sea plants for the purposes of paper-making may well form a side issue in dealing with local conditions. The study of long-shore vegeta- tion and its function in relation to the design of public works is largely a new departure. No department can be efficient which fails to study the application of vegetal growth to specific purposes of development. It would, in fact, perform the function in respect of tidal waters which a Forestry Department does in the afforestation of land surfaces. Air Reefs.—One of the most striking departures in sea work of recent years is the Brasher system of compressed air, for AIR REEFS 261 stilling an area of disturbance in the open sea or other exposed waters. Similarly it is efficient in the protection of shores liable to erosion. This system has been adopted with success in America, notably by the Standard Oil Company at El Segundo, California. Its resultant effect is to produce an area of still water by means of the ejection of air from perforated pipes laid on the sea bed. At El Segundo the pier, as built, was 4000 feet long, and in the winter of 1914-5 a length of nearly 2000 feet of it was washed away. In this instance the submerged perforated pipes subsequently laid for its protection were served by existing compressors, and a shield or wall of air, rising from the bed of the sea to the surface, was created. This air reef neutralized the sea disturbance, producing sufficient tranquillity to permit vessels to load or discharge at the pier in stormy weather. From installations already carried out the cost of the appli- cation of the system appears to be about £2 to £4 per lineal foot. It is obviously only necessary to put the apparatus in opera- tion in rough weather. When the sea or other exposed area of water is naturally tranquil, craft can lie alongside a jetty or quay to discharge or load, without let or hindrance. On the approach of doubtful or stormy weather, the compressed air is switched on and still water results. A ship at the jetty thus lies surrounded by broken water, but in a lagoon of safety. The applications of the air method are varied. Not only is it available for protecting shipping made fast to a pier in the open sea or otherwise, but it can be used during the construction of sea-walls, piers, lighthouses, &c., to produce artificial tran- quillity, and thus enable operations to be carried on undisturbed. Stranded vessels can also be protected from the pounding action of the waves, and round lighthouses or lightships a tranquillized area of water, as occasion demands, can be created. The cost of operating the apparatus is small. At El Segundo, during a heavy winter storm, the plant was in opera- tion for twenty-three hours at a cost of £12. One important application of the system is that of protecting 262 COMPLEMENTARY PROBLEMS dredgers in exposed places during rough weather, and thus enabling them to carry on their work undisturbed. A trial of the Brasher invention during the raising of the U.S.S. Yankee was described by an eye-witness as follows:— ‘‘The heavy breaking seas were powerless to pass the line of air. Before the air was turned on the seas were boarding the ship fore and aft, causing it to grind very much on the rocky bed, and making work very disagreeable. After the air was turned on in the breakwater it was as though the ship was ina lagoon formed by the sea breakwater, while seas were breaking heavily outside.” The success of the system depends on the neutralization of the oscillatory impulse of waves in deep water. Each of the bubbles forming the air screen as it rises to the surface has an explosive action. These collectively disrupt the wave mass, and disturb the continuity of its particles in such a manner that the wave beats out of time, and losing its rhythm, its rolling motion is automatically brought to a deadlock. An ingenious explanation of the action is contained in a letter to 7he Engineer, dated 9th June, 1916. The theory evolved by the writer is that, as the effect of a current of air passing over a rounded surface is to cause some increase of pressure on the windward side and a corresponding reduction of pressure on the leeward side, the emission of a column of air rising from the bed of the sea under pressure upsets the plus and minus surface pressure conditions set up by the wind passing over wave crests, resulting in these becoming self-destructive, with the effect of stilling the forces of oscillation. APPENDIX I List of Dune Plants Pioneers on Moving Sand:— Elymus arenarius (Graminez). Psamma arenaria (Graminez). Salix repens (Salicacez). Festuca rubra (Graminez). Carex arenaria (Cyperacez). Euphorbia Paralias (Euphorbiacez). Eryngium maritimum (Umbelliferz). Pioneers Restricted to Strand:— Triticum junceum (Graminez). Arenaria peploides (Caryophyllacez). Salsola Kali (Chenopodiacez). Cakile maritima (Cruciferz). On Resting Sand:— Polypodium vulgare (Filicinez), Pteris aquilina (Filicinez). Corynephorus canescens (Graminez). Luzula campestris (Juncacez). Asparagus officinalis (Liliacez). Rumex Acetosella (Polygonacez). Cerastium semidecandrum (Caryophyllacez). Sedum acre (Crassulacez). Rosa pimpinellifolia (Rosacez). Ononis repens (Leguminosz). Lotus corniculatus (Leguminosz). Hippophae Rhamnoides (Elzagnacez). 263 264 LIST OF DUNE PLANTS Sambucus nigra (Caprifoliacez). Ligustrum vulgare (Oleacez). Convolvulus Soldanella (Convolvulacez). Cynoglossum officinale (Boraginacez). Thymus Serpyllum (Labiatz). Solanum Dulcamara (Solanacez). Euphrasia officinalis (Scrophulariacee). Galium verum (Rubiacez). Anagallis arvensis (Primulacez). Jasione montana (Campanulacez). Senecio vulgaris (Composite). Senecio Jacobza (Composite). Cnicus arvensis (Composite). Cnicus lanceolatus (Composite). Hieracium Pilosella (Composite). Taraxacum officinale (Composite). Erodium cicutarium (Geraniacez). &c. &c. Mosses :— Tortula ruraliformis. Ceratodon purpureus. Hypnum cupressiforme, &c. Lichens :— Peltigera canina. Cladonia furcata. Cladonia rangiferina, &c. Ephemerals (resting sand) :— Veronica hederifolia (Scrophulariacez). Veronica agrestis (Scrophulariacez). Saxifraga tridactylites (Saxifragacez). Cerastium glomeratum (Caryophyllacez). Cerastium tetrandrum (Caryophyllacee). Sherardia arvensis (Rubiacez). Myosotis collina (Boraginacez). Draba verna (Crucifere). Phleum arenarium (Graminez). APPENDIX III 265 APPENDIX II Types of Shingle Beach (English) Spits :— Hurst Castle and Blakeney (with hooks). Northam, Spurn, Aldeburgh, Hamstead (Isle of Wight), Cammaes (Anglesea). Bars :— Chesil, Pevensey, Slapton. Apposition :— Dungeness, Aldeburgh (Orfordness), Pevensey (Langney Point). APPENDIX III Plants of the Shingle Beach Mobile Shingle:— Silene maritima. Glaucium luteum. Rumex trigranulatus. Sedum acre. Crambe maritima. Geranium purpureum. Lathyrus maritimus. Atriplex patula. Suzeda fruticosa Artemisia maritima Statice Limonium Plantago maritima Ranunculus bulbosus foe from freshwater marshes, Polygonum amphibium and meadows. Arenaria peploides—where much sand present. Psamma and Elymus—as dune relics. Halophytic element. 266 PLANTS OF THE SHINGLE BEACH Stable Shingle :— Solanum Dulcamara. Convolvulus Soldanella. Mertensia maritima. Beta vulgaris. Festuca rubra. Triticum junceum. Arrhenatherum avenaceum. Galium Mollugo. Galium verum. Lotus corniculatus. Sedum acre. Galeopsis Ladanum. Echium vulgare. Statice binervosa. Armeria maritima. Sambucus nigra. Ulex europzus. Cytisus scoparius. Crategus monogyna. Rubus fruticosa. Prunus spinosa. Ilex Aquifolium. Triticum pungens. Inula crithmoides. Artemisia maritima. Plantago Coronopus. Plantago lanceolatus. Holcus lanatus. Festuca rubra. Agrostis maritima. Trifolium arvensis. Rumex Acetosa. Rumex Acetosella. Digitalis purpurea. Ballota nigra. Urtica dioica. APPENDIX IV 267 Lichens :—~ Verrucaria maura. Rhizocarpon confervoides. Buellia colludens. Physcia parietina. &c. APPENDIX IV Plants of the Salt Marsh Alge :— Rhizoclonium. Enteromorpha. Vaucheria Thuretii. Lyngbya. Microcoleus chthonoplastes. Fucus vesiculosus, forms—volubilis, limicola, muscoides. Fucus balticus. Pelvetia canaliculata, forma libera. Ascophyllum nodosum v. scorpioides, Bostrychia scorpioides. Angiosperms :— Salicornia annua (Chenopodiacez). Salicornia ramosissima (Chenopodiacez). Salicornia radicans, &c. (Chenopodiacez). Suzda maritima (Chenopodiacez). Obione portulacoides (Chenopodiacez). Glyceria maritima (Graminez). Spartina stricta (Graminez). Spartina Townsendii (Graminez). Triticum pungens (Graminez). Scirpus maritimus (Cyperacez). Cochlearia officinalis, &c. (Cruciferz). Statice Limonium (Plumbaginacez). Statice humilis (Plumbaginacez). Statice reticulata (Plumbaginacez). 268 SALT MARSH DEVELOPMENT Armeria maritima (Plumbaginacee). Glaux maritima (Primulacee). Samolus Valerandi (Primulacez). Aster Tripolium (Composite). Artemisia maritima (Composite). Spergularia media (Caryophyllacez). Spergularia salina (Caryophyllacez). Plantago maritima (Plantaginacez). Plantago Coronopus (Plantaginacez). Frankenia laevis (Frankeniacez). Juncus maritimus (Juncacez). Juncus Gerardi (Juncacez). Triglochin maritimum (Naiadacez). Zostera marina and nana (Naiadacez). APPENDIX V Salt Marsh Development ‘Varies with locality and substratum. In the examples given the numbers indicate the order of the phases or ‘‘ successions”. I. Mud. Bouche d’ Erquy :— (1) Salicornia ramosissima + Rhizoclonium. (2) S. ram. + Glyceria maritima (‘Crimson Plain’’). (3) S. ram. + Glyceria marit. + Suzeda maritima. (4) Glyceria + Armeria + relics of (3). Blakeney Point:— (1) Salicornia annua + Pelvetia libera. Marginal zone with accretion: Suada maritima, Salicornia radicans, Obione (dwarf), and relicts of (1). (2) Salicornia + Aster. APPENDIX V 269 (3) Mixed Salting (Statice Limonium, Spergularia media, Triglochin, Plantago, Glyceria). (4) Obione (high) + relicts of (3). Blakeney Point:— (1) Enteromorpha sp. (2) Fucus limicola, Salicornia annua (Enteromorpha). (Pelvetia libera would come in here.) (3) Salicornia + Aster. (4) Mixed Salting. II. Sand. Bouche d’Erquy:— (1) Salicornia radicans hummocks; bare between (perennial). (2) S. rad., Glyceria, Sueeda maritima, &c.; Salicornia ramosissima (annual; in the troughs). (3) Glyceria + other halophytes. (4) Rolling turf of Glyceria with Sd. mar. and other halophytes. Arnside:— (1) Glyceria maritima hummocks. (2) Glyceria + Lepturus filiformis and Agrostis alba v. marit. Spergularia media, between the hummocks, and later Aster. (3) Festuca rubra v. pruinosa, Lepturus and Agrostis + Aster, Plantago, Armeria. 270 DISTRIBUTION OF SUZDA FRUTICOSA APPENDIX VI On the Distribution of Sueda fruticosa at Blakeney Point From an inspection of the different sections of the main beach it is evident that there is great variation in their degree of sterility. For a complete explanation it would be necessary to consider every species of plant in relation to the conditions obtaining on each section of the beach—a subject too exhaustive to be entered on here. The case of Suceda fruticosa, an outstanding plant on Blake- ney Point, may, however, be taken in some detail, and will serve at the same time to illustrate the kind of circumstances that are significant in the distribution of any species of plant. The various sections of the Main Beach and the occurrence of Suzda are indicated on the accompanying diagram (fig. 54), which represents in simplified form a chart extending from the reclaimed marshes opposite Salthouse in the east to and in- cluding the Hood in the west. This stretch, actually over 4 miles in length, includes all the different types or combinations of conditions which the Blakeney beach provides. Each section will be considered here in relation to the two fundamental conditions which must be satisfied if Sueda is to become established— (a) The facilities for the introduction of seed to the lee fringe; (6) The stability of the lee fringe during the period of establishment. For brevity these are referred to as inoculation and stability, respectively. 1. Protected Bays (Sections B and £, fig. 54).—The pecu- liarities of these, already referred to (p. 235) for the Marams section (£), are as follows. The talus fans whilst washed by the spring tides, thus receiving their quota of drift and seeds, APPENDIX VI 271 are protected from erosion by the hooks. Consequently, the materials of the lee fringe remain quiescent till fresh shingle is shot down from the crest. The intervals of quiescence in recent years have been long enough for the establishment of Suzda bushes. The conditions at B resemble those at E— the fans remain and Suzda establishes. This type of lee fringe is represented on the diagram (fig. 54, B and £) by an unbroken sinuous line, the Suzda plants by dots following the scalloped edge. 2. Open Bays (Section c).—These occur east and west of A B Cc ~<(GE ~---- Sy PROTECTED OPEN BAY HOOK Fig. 54.—Diagram Map of Blakeney Main Beach from the Reclaimed Marshes to the Hood, showing the distribution of Suada bushes in zones (rows of dots 1, 2, and 3) The different types of the lee edge referred to in the text occur opposite the letters A to H. a, beach bordered by dune; B and E (sinuous line), dormant fans; c and F (broken line), edge eroded by scour; D, place of accumulation of shingle drifted east from section c; G, beach bor- dered by sea-wall; 4, shingle fan projecting through breach in sea-wall. the Hood. The lee fringe is not protected by hooks and is liable to scour when the wind blows from the south or south- west.