On other parts of the coast the beach "travels," being driven along the underlying solid shore by the prevailing direction of the tidal currents and by the waves. The sea-waves break close to the soft cliffs of clay, sand, and sandstone. These are continually crumbling away owing to the action of land water, which soaks from the surface down to the layers of clay and forms subterranean springs and streams. They undermine the face of the cliff and cause the upper parts to topple. When there is a big, broad, growing beach in front of such a cliff, the breaking down or "toppling" of its face only leads to the formation of a slope (at the "angle of rest"), and things remain but little changed for ages. But if the beach is not being piled up and added to and growing out seawards year by year, and is, on the contrary, a travelling beach, then the sea comes close up to the cliff, and when masses of it topple on to the beach the sea washes them away, and no "slope of repose" is formed. The cliff keeps on toppling as it is undermined by springs of land water. Its natural buttress against further breakage--namely, its own fallen material--instead of resting against it as a great sloping, protective bank, is washed away by the sea as fast as it falls, and is carried down the coast by the tidal currents. This is the story of "coast erosion" about which there has recently been a Government inquiry. Where the combined action of prevailing winds and sea currents is throwing up and adding to the beach there is no coast erosion. The causes of the sea currents on our coasts are not easy to determine, as they are connected with the general contour of the land and the currents in large tracts of sea, such as the Channel and the North Sea. Coast erosion is a serious thing. Large parts of the coast of Suffolk and Norfolk are being thus washed away. It can be prevented by "holding" the beach with piles and boarding, but this costs too much to make it worth doing unless the land so preserved has a special value for the erection of houses.
At Felixstowe, where I am writing, the sea has swept away most of the flat--the "dunes," or "deans"--covered with grass, which it had itself built up by a contrary accumulating action before the time of the Romans. On this flat the ancient Roman town was built. Why the sea has reversed its action is very difficult to say. But within my knowledge of this place high-water mark has advanced as much as 300 yards nearer than it was to the old roadway and to old houses. The great town of Dunwich, which in the Middle Ages had eleven churches, strong fortifications, and a flourishing trade, stood on the flat grass-land in front of the cliff on the Suffolk coast. Its site is now under the sea, not far from here. The breaking away of the cliff (on to which part of the town extended) is still going on there. A few years ago I saw a great bricked well lying like a fallen chimney on the shore. It had been exposed by the crumbling of the cliff, and at last fell out of it. Once that well supplied fresh water to the monastery, part of the walls of which are still standing, and were formerly three-quarters of a mile distant from the seashore. The prehistoric cliffs to which the sea came before it formed the flats or links which it is now again eating away, are often traceable a mile or two inland. On the other hand, on parts of the Lincolnshire coast the sea has piled up sand and shingle and added valuable land to the extent of hundreds of acres to the property of those whose estates were bounded by the shore line, and is still doing so. Perhaps the action of the north wind in blowing back and piling up sand out of the reach of the tide is influential in producing this increase of shore-lands, which face northwards. Blown sand forms hills 30 feet and more in height on such flat lands as those of the Sandwich and Deal "links," which have been thrown up by the sea since St. Augustine landed at Richborough, then a seaport, now a couple of miles from the sea. On the French coast near Boulogne the sand has been blown inland so as to form stratified deposits on the low hill country as far as 3 or 4 miles from the sea, and the neighbouring port of Ambleteuse, which five hundred years ago had the chief trade with England--is now nothing but a vast stratified "dune" of blown sand. The great Napoleon made some attempt to reopen the harbour, but gave it up as a bad job; the blowing of sand inwards from the enormous tract of flat, sandy shore was too much for his engineers.