« AnteriorContinuar »
with a thin covering in some places of sand, and in others it is bare. There is a bank of shingle skirting the shore all the way from Wademarsh, about a mile west of Birchington, to Faversham, the pebbles being collected in a mound at and above the level of mean high water. The sea face lies in ridges from 6 to 9 feet wide, with slopes varying from 1£ to 1 to 3 to 1, denoting the heights of successive tides. Towards the sea-wall the shingle rises about 6 feet above H.W.O.S.T., the total width of the shingle-bank being about 80 feet.
At Heme Bay, east of the town, the shingle reaches to the foot of the clay cliffs, the highest part being from 4 to 6 feet above high water, and from 40 to 50 feet wide. Along the frontage of the town the shingle is about 8 to 10 feet below the top of the sea-wall at the east end, and from 2 to 3 feet at the west end.
The drift of the shingle is from east to west, the same as the set of the flood tide, but from the shape and appearance of the pebbles there does not seem to be much movement. The pebbles consist almost entirely of rounded flints, varying in size from \ to 3 inches in diameter. They closely resemble, both in size, colour, shape, and appearance, those contained in the Thanet sands of which the cliffs are composed, and in the gravel pits more inland. Occasionally, during on-shore gales, large unworn flints with seaweed attached are cast up on the beach, and these no doubt come from the flint bed which underlies the Thanet sands.
The origin of the flints on the beach must be purely local, as the beach in front of Westgate consists of chalk covered with seaweed, and is devoid of both shingle and sand except in Margate Bay.
Although the layers of flint in the cliffs of the Thanet sand do not exceed from 6 to 9 inches in thickness, considering the immense amount of erosion that has taken place along this part of the coast, the quantity of flints thrown down on to the beach from the cliffs would appear to be sufficient to account for the shingle which now lies along the coast, and which probably is supplemented in storms by the flints loosened on the beach below low water, but within range of the breaking waves.
The loss of land along this part of the coast has been very great. It is stated that in Henry VIII.'s time the church at Reculvers was a mile from the sea. Leland, writing in 1530-37, says that the village of Reculvers stood within a quarter of a mile of the seaside. In 1809 the sea had so far encroached that the church on the top of the cliff had to be removed, and later on the sea made a total wreck of the village which then existed. The two towers of the ancient church now stand on a mound about 36 fathoms from high-water mark, and, being a wellrecognized sea-mark at the entrance of the Thames, the Trinity House purchased them for about £100 in 1811, and spent £500 on groynes and other works for their protection; and in 1866, to prevent any further fall of the cliff, and the exposure of bones from the old churchyard, the cliff was protected by an extension of the stone-pitched apron on the shore, and the construction of a curved revetment of Kentish rag stone carried up to about highwater mark on the face of the cliff below the towers. From thence a concrete wall, boxed in with timber, extends about 60 yards to the westward.
Between Birchington and Heme Bay the sea-wall and coast has been protected by groynes maintained by the Commissioners of Sewers, and the same kind of groynes are maintained along the frontage of Heme Bay, and are being extended further to the west. These groynes consist of oak posts, many of which are made from old ship timbers, 10 feet long and spaced from 4 to 5 feet apart, driven into the clay beach, to which are spiked 2-inch horizontal planks. Those used in recent repairs are of oak 6 inches square. The groynes extend out at right angles from the shore, and their length, measured from the cliff, may be taken at about 130 feet. They are spaced at about 30 feet apart, and rake at an inclination of 1 in 8.
In front of Heme Bay there are ninety-one groynes, spaced from 100 to 120 feet apart. They consist of 3-inch planking spiked to 7-inch by 6-inch oak posts, spaced from 4£ to 5 feet apart, placed on alternate sides of the boarding, and extend at right angles to the sea-wall, to about the line of mean high water, their length varying from 50 to 200 feet.
These groynes have been the means of stopping the drift of the shingle to the west, and causing a considerable accumulation above high-water level. In heavy on-shore or north-east gales the shingle is driven up shorewards, and during the great gale and high tide of November, 1897, the waves breaking on the shore carried very large quantities of the shingle on to the roadway, the road being covered 3 feet deep in places.
On the eastern side of the old pier at Hampton (about 2 miles west of Heme Bay), in the angle formed by its junction with the shore, an extensive accumulation of shingle has taken place, notwithstanding the carting away of large quantities for various purposes.
The beach generally, along the Heme Bay frontage, has wasted away considerably during the last few years. A comparison of the Ordnance Survey of 1872 and 1896 shows that the low-water mark is now from 1000 to 1300 feet nearer the parade than it was twenty-four years ago.
The gradient of the foreshore between the lines of H.W.S.T. and mean high water is steep, the inclination being about 1 in 7. In order to raise the beach and give it a uniform slope of 1 in 12, it is proposed to replace the present groynes by others spaced further apart and carried down to low water, their length varying from 500 to 900 feet.
Isle of Sheppey and Sheerness.—Further up the estuary of the Thames, on the north of the Isle of Sheppey, which consists of cliffs composed of London Clay from 60 to 80 feet in height, considerable erosion has taken place. Between 1856-59 a great slip took place in the cliff, and the site of Warden Church, the tower of which was built from the stones of old London Bridge, together with the churchyard, fields, and a coastguard house, disappeared, the church having been removed inland. Three coastguard stations have also had to be pulled down. Minster Church, which at the end of the last century was in the middle of the island, or about 2 miles from the coast, is now close to it. Between 1810 and 1830 it was estimated that 30 acres of land had disappeared, and it is stated that within the last forty years the coast-line has been set back by the sea 80 feet.
In 1885 Colonel Sim, R.E., reported that from Shellness Point, at the eastern end of the island, to Sheerness the coast was being gradually undermined by the action of the sea, and the debris conveyed by the tide towards Sheerness, the limestone nodules washed out of the cliff being collected by the fisherman for cement-making.
The movement of the shingle on the beach has been from east to west, and runs out in a spit at Garrison Fort Point. In 1737 this shingle spit was half a mile east of Garrison Point, and since that date it has grown out about 1000 yards. This part of the coast has been protected by wooden groynes put down when the fort was erected; they point in a north-easterly direction, the accumulation of shingle being from 6 to 7 ieet higher on the east than on the west side. The southern bank of the Medway from the dockyard to Queenborough has also been protected by groynes, to prevent the erosion that was then going on. On the opposite side of the Medway, at the Isle of Grain, where the action of the sea is very destructive with north-east winds, groynes and a sea-wall have been built to prevent the erosion in front of the fort. The groynes were made to point in a north-easterly direction, the accumulation of shingle to windward often being from 6 to 7 feet higher than on the other side. These groynes are described as consisting of two parallel rows of small round oak piles driven down about half their length through the sand and shingle into the clay, battering on the outside, their heads inclining inwards, the intervening space being filled with rough Kentish rag stone, the top being from 2 to 3 feet above the beach. The groynes run out at right angles to the shore, at a rake of 1 in 7 to 1 in 10, corresponding with that of the beach. Some groynes which extend a greater distance outward have a rake of 1 in 30. They are spaced at distances equal to one-half to onefourth their length.
Large quantities of shingle have been removed for concrete, roads, and other Government works from the accumulation at Garrison Point, and also by the landowners at Cheney Point. The septaria which fall from the cliffs was formerly collected and removed for cement-making.
Sandwich and Deal.—The cliffs consisting of chalk with flints end about half a mile south of Ramsgate, and beyond this the coastline sets back more than 2 miles. Between the point where the cliffs end and the outfall of the river Stour is Pegwell Bay, a low flat beach 1J miles wide, which is left dry at low water. The bay is skirted by low cliffs consisting of Thanet beds.
The report made to the British Association in 1895 states that since the previous report, made in 1884, there had been a continuous and large amount of erosion going on along the shore in Pegwell Bay, the sea having removed the talus of the cliff and the shore accumulation, the cliff itself being cut back at a rapid rate, more especially at Cliff End. Within the previous three years nearly all the trees that fringed the top of the clay beds had been thrown down and washed away; the chalk cliff to Pegwell and on to Bamsgate having suffered from many falls. There had then been no attempt at groyning or other protection. At Ramsgate, both east and west of the harbour, there had also been many falls, the cliff being perpendicular and free from talus, the waves breaking at its foot. North of Ramsgate to Dumpton gap there had also been several falls of cliff. Round the north promontory of the Isle of Thanet the erosion had been less, but generally there was an absence of beach.
The Goodwin Sands, which run parallel with this coast for a length of 10 miles, and at a distanco of from 4 to 5 miles from the shore, are generally supposed to have been at one time joined to the mainland.
Between Peg well Bay and Deal there is a large tract of salt marsh, and bordering on this are sand-hills from 10 to 15 feet high.
From Shingle End, on the south side of the river Stour, a large shingle-bank extends southward to Sandown Castle, a distance of 5 miles. The width of this bank varies from 500 yards at the northern end to three-quarters of a mile at the widest part opposite Sandwich, and diminishes to 100 yards at the southern end. The top of this bank is about 10 feet above mean high water. The shingle continues along the beach in front of Deal to St. Margaret's Bay, 5 miles south of Deal.
This shingle is derived from the waste of the cliffs, which commence near King's Down about 2 miles south of Deal, and consist of chalk with many flints, their height between King's Down and St. Margaret's Bay being from 80 to 100 feet. During recent years the beach in this bay and along the South Foreland has become very much denuded, and the waves now break on the cliffs, causing great destruction. The cause of this denudation has been ascribed to the effect of the projection at Dungeness, which has stopped the drift along the coast, which used to come from the west.1
The collection of shingle at Dungeness has, however, been taking place for a period long anterior to the denudation that has within recent years prevailed in St. Margaret's Bay; there are causes nearer to the bay which are sufficient to account for the denudation of its beach. The drift of shingle along this part of the coast has been arrested by the groynes which have been constructed at Hythe, Seabrooke, Sandgate, and Folkestone. The harbour wall at the latter place traps all the shingle which