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Beach Erosion in the Rives Manche
The East Sussex Coastline
The East Sussex coastline stretches for some 75 km from Brighton in the west to beyond Camber in the east. Generally southerly facing throughout its length, individual sections of the coast vary in aspect from south southwest to east southeast. The coast comprises bold cliffs of chalk and sandstone separated by alluvial lowlands.
In the west, between Brighton and Eastbourne there are 27 km of vertical chalk cliffs that are divided into three blocks by the wide mouths of the rivers Ouse and Cuckmere. They reach a maximum height of 165m at Beachy Head. At the base of the cliffs gently sloping shore platforms extend seawards for up to 200m to below low water mark. The upper parts of the platforms are often covered with a pebble or shingle beach, but the lower part is bare except for a covering of seaweed. The platform surface is often dissected by a system of runnels along which flint pebbles are rolled during each tidal cycle, especially during storms.
Further east, around Hastings there are tall cliffs composed predominantly of Cretaceous sandstone. The rocks here are more variable in composition than the chalk, with intervening beds of silt and clay lying between and below the beds of sandstone. This results in extensive coastal landslipping. Erosion of the cliffs produces large blocks of sandstone that litter the beaches at the foot of the cliffs. However, marine action rapidly reduces the blocks to sand and pebbles of sandstone occur only locally.
The Sussex beaches are composed predominantly of flint derived from the chalk. Fresh, new flint is added to the beaches by erosion and retreat of the chalk cliffs and the shore platforms at their base. Secondary, iron-stained, pre-worn flints, some of which are frost-damaged, are added to the beaches from the erosion of Tertiary and Quaternary deposits that locally overlie the chalk.
Along low-lying stretches of coast a sand beach frequently underlies the pebble beach and is often exposed at low tide. Restricted stretches of beach composed entirely of sand also occur, notably in the far east of the county at Camber where a wide, sandy beach is backed by sand dunes.
The prevailing wind direction is from the south west and waves generally approach the Sussex shore from this direction. As a consequence sand and shingle moves eastwards along the beaches. In past centuries this led to the growth of shingle spits and bars across bays and estuaries. The mouths of rivers such as the Ouse and Cuckmere were deflected eastwards and often partially blocked by drifting shoals of sand and shingle. Today this has largely been stopped by extensive groyning of the beaches and the protection of harbour mouths by breakwaters. Today all except those sections of coast backed by high cliffs are groyned and immediately to the east of Brighton groynes have been installed even in front of tall cliffs to help reduce coastal retreat that threatens cliff-top properties and the coastal highway.
In recent years, problems of beach depletion, coastal erosion and the risks of flooding has led to the recharging of several beaches with flint from offshore shingle banks most notably from the Owers bank off West Sussex.
Last updated 12/JUL/2001 MAW |