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groynes material cannot be collected equally on both sides, and that by commencing with low groynes, and gradually increasing them in height as the beach accumulates, not only will the bays fill equally and to a natural slope, but when the construction of the beach is finished the accumulated material will retain its form under all conditions of wind and tide; and that low groynes, being less subject to the action of the waves, and becoming soon buried, may be economically and quickly constructed.

On these principles Mr. Case constructed a number of groynes at Dymchurch which have been very successful, a description of which will be found in Chapter VII. He also laid down similar groynes at other parts of the coast.

He further advocated that groynes should not be carried up the bank beyond the point to which the mean high water reaches. It is doubtful if the stopping of the groynes at this

CASE GROYNE

FIG. 22.

point will be found satisfactory, especially when the beach consists principally of sand. An examination of some of the groynes erected on this principle shows that the waves running round the end of these tend to scour out the beach; and it is to be apprehended that these shortened groynes will aid in developing those lows or hollows running parallel with the coast which are produced by the waves in gales on sandy beaches at or about the point reached by high water.

The author has inspected most of the places where the Case system of groyning has been adopted.

Local opinion as to their efficiency varies very considerably. Fishermen, boatmen, and others engaged on the shore appear to have not only a very strong prejudice against them, but consider

that, while they are dangerous for the boats, they are ineffective in improving the beach.

The general conclusion arrived at by the author is, that while their beneficial effect has been exaggerated, yet that, in the majority of cases, they have given the same satisfactory results as have always been obtained by the use of low groynes, and have had a good effect in building up the beach where they have been down a sufficient time. The conditions of littoral drift, however, vary so much that the application of any one particular system of groyning to all parts of the coast cannot be expected to give satisfactory results on all the beaches to which it may be applied.

The principle on which these long low groynes are designed is in the author's opinion correct, except as to their only commencing at the line of mean high water; and it has been proved that under certain conditions they are capable of moulding the shape of a sandy beach into a natural form by taking away the sand from where it is not wanted, and putting it where it is required; and, by filling up lows and swills, converting wet sands into dry hard beach.

Groynes constructed on this or any other system cannot be expected to collect beach material when it does not exist; but these low groynes are more calculated to alter the contour of the beach advantageously than the short high groynes that are so frequently to be met with.

In the construction of groynes, Mr. Case adopted the plan of fixing the uprights to which the planking was attached in concrete blocks, and he claimed that by this means the groynes could be constructed more easily and rapidly, and at less cost than by driving piles into the beach. The saving in cost has, however, been disputed; and it has also been questioned whether groynes fixed in this manner will stand the wear and tear of storms as well as those supported by piles; but it must be borne in mind that low groynes of this character offer far less resistance to the waves than those which extend further above the beach, and so far as experience has gone, results seem to show that groynes fastened into concrete blocks are not subject to more accidents than those supported by piles.

In 1896, a patent was taken out for this system as an "improved construction or arrangement of shore groynes." The validity of this patent was contested in an action brought in 1900,

in the Court of Chancery, by the representatives of Mr. Case against the Clacton Sea Defence Commissioners (Case v. Cressy), who had constructed groynes of a similar character and refused to pay the royalty claimed. It was held by the Court that, although, according to the evidence, the mode of construction has advantages that make it useful, and that it is cheaper than the ordinary way of constructing groynes by driving piles, yet the system, being merely an adaptation of well-known methods of construction, does not contain the elements of novelty of design or of inventive faculty on the part of the patentee to constitute it subject matter for a patent, and that therefore the patent that had been obtained was not valid; and this decision was confirmed by the Court of Appeal at a hearing in July, 1901.

In 1899 and 1900 fresh patents were applied for, relating to the securing of the uprights by bolts and cross bars to a box buried in a hole in the foreshore and filled with any ordinary material, thus dispensing with the use of concrete, the later patent applying to the fixing of the uprights by projecting

iron bars.

Beard's System.-Mr. E. T. Beard, the surveyor of the Pevensey Level, who has under his charge the sea defences of about 10 miles of coast in that part of the country, has also taken out a patent for the "improvement in shore groynes." He differs from Mr. Case in considering that groynes should only commence at about the level of mean tides. His system, which consists of a combination of high and low groynes, is described in the patent specification as consisting of two levels, the upper part being horizontal and carried above high water, and the lower part being placed below high water, the two levels being connected by a ramp sloping at the same angle as the beach. This ramped part is intended to be moved outwards as the bank of shingle next the shore grows up. It is claimed for this system that "the beach which passes over a groyne is caused to accumulate at both sides to any desired extent, and to render a single groyne self-supporting." The object to be gained in joining the two portions of the groyne by a ramp is "to control the passage of beach, causing it to pass at or below the junction at the two parts." With groynes constructed in this manner, Mr. Beard claims to have moved the high-water mark on the beach at Cooding, near Bexhill, a maximum distance of 120 feet, and an average distance of 90 feet,

further seaward, and raised the level of the beach 20 feet on the windward side and over 16 feet on the lee side. These groynes are spaced 250 yards apart. The same class of groynes have been put down at the Crumbles near Eastbourne, and it is claimed that the shingle has been raised near the shore 20 feet on the windward side, and 14 feet on the lee side, leaving a drop of 6 feet between the two sides.

Conclusions. The conclusion arrived at by the author after an inspection of the principal works of groyning along the coasts of England, Belgium, and Holland, is as follows:

(1) That in many instances where the length of coast to be protected is not great, a single groyne placed at the extreme leeward end of the beach, and carried as far below low-water mark as practicable, and raised from time to time as the shingle accumulates, is sufficient to prevent the drift of material, and will provide a level and even beach.

(2) That if groynes be placed at short intervals, they should consist of low inexpensive structures of wood, extending out from the sea-wall or cliff to low water of neap or spring tides, according to the condition of the beach.

(3) That there is no advantage derived from placing groynes near together. As a general rule, it may be taken that the distance should never be less than the space lying between extreme high and low water of spring tides, but may with advantage be made greater than this.

(4) That the tops of groynes should not rise more than about 2 feet, or at the most 3 feet, above the natural surface of the beach, provision being made for raising them as the beach accumulates.

(5) That the best direction for groynes is at right angles to

the line of coast.

(6) That the inclination of groynes should vary as they proceed seaward, in harmony with the natural slope of the beach.

(7) That as regards the length, they should extend from high water to low water of spring tides, and when they are placed at short intervals, the leeward groyne should extend from the cliff, or extreme high-water mark, to a short distance below low water, each windward groyne being shorter than the one preceding it, and lengthened as the beach grows up.

Crown Rights. It may be as well to point out that, as the

shore between ordinary high water and low water belongs to the Crown, unless it has been alienated by grant to the lord of the manor or frontager, no groynes or erections of any kind for coast protection can be constructed below high water without consent being first obtained from the Board of Trade or the owner of the foreshore.

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