The Hasborough Sands probably increase in breadth if not in length, since every year they receive fresh accessions from vessels buried in their vortex, which afford a nucleus for retaining the sand lodging against them.
The Cockle Sands, off Caistor, [39] have increased since 1836 one mile and a half in extent to the northward.
The deposition of sands, stones, shingle, &c., upon our coast, especially during the summer months, when easterly, southerly, and westerly winds prevail, would strike the beholder unaccustomed to witness the contrary effects, as an apparent impossibility, that the water could remove such an immense quantity of material especially in the short time that it does when a north-west gale prevails.
Shoals of sand of various length, breadth, and depth, appear and disappear, form and re-form, in the offing.—In north-westerly gales only are they solid, stable, and compact, and increase in breadth, while the materials on the beach are swept away. They extend in a direction parallel with the shore, and present an inclined plane, on each side of their base a corresponding shallow exists, and the tidal current will not allow materials to rest on their surface sufficiently to increase their elevation, and render them more efficient. As it is, however, they are natural breakwaters, but from their irregularity in extent, dimensions, and situation, they afford only a partial protection to the coast.
The incursions of the sea at Aldborough, in Suffolk, were formerly very destructive; and this borough is known to have been once situated a quarter of a mile east of the present shore. The inhabitants continued to build further inland, till they arrived at the extremity of their property, and then the town decayed greatly; but two sandbanks thrown up at a short distance, now afford a temporary safeguard to the coast. Between these banks and the present shore, where the current now flows, the sea is twenty-four feet deep on the spot where the town formerly stood.
Immediately off Yarmouth, [40a] and parallel to the shore, is a range of sand-banks, the shape of which varies slowly from year to year, and often suddenly after great storms. The late Captain Hewett, R.N., found in these banks, in 1836, a broad channel sixty-five feet deep, where there was only a depth of four feet during a prior survey in 1822. The sea had excavated to the depth of sixty feet in the course of fourteen years, or perhaps a shorter period. [40b]
Wherever a shoal of sand exists in the offing, at a distance beyond where the ebbing of the tide recedes to its greatest extent, denominated low water mark, there the innermost shallow will probably be: another shoal immediately forms, the base commencing at low water mark, and a gradual rise takes place towards the cliffs, terminating at or beyond the extent of the flowing of the tide denominated high water mark. Here, then, the shoal will be more efficient; the tidal wave and current will be checked and broken against the ascending bank.
But should a shoal of sand form whose superior surface terminates at low water mark, the innermost shallow [41] will be observed nearer to, and its course frequently terminate in, an angular direction to the cliffs; and between the intermediate spaces of the shoals existing in the offing, a current frequently sets in towards the shore, which will aid the force of the tidal wave and current, when called into excessive action, in its attack either upon the cliff opposite, or a partial shoal nearest it. Under these circumstances, the one will soon lose its inclined surface, and the other will become undermined.
Where shoals of sand exist in the offing, there the beach is widest, and where they do not exist, there the beach is narrowest.