Beaches Research Paper

Beaches

1. Over the three fourth of the coastline is beach-fringed, the principle determinant of these being waves, supply of beach materials, contour and lithology of the coastline, and nature of coastal and sub-marine landforms. Most of the beaches of the island are barriers backed by lagoons, swamps and ill-drained terrains and are sometimes contained between headlands or river outfalls. Some barriers are island at both ends, e.g. Karatiu Island. Chenier characteristic of shorelines destroyed by erosion are found at Akurala and East of Weligama.

2. Most of the beaches in the island are sandy although beaches of pebble, rubble and boulders sometimes occur along restricted stretches, e.g. Galle Buck. Pocket beaches formed by deposition of sand in small embayments of coastal bedrock stretches are also found, e.g.

Owing to the small tidal range and relatively low energy, the beaches in Sri Lanka are generally narrow. The beach deposits increase in width from the South-Western corner of the island in both directions reaching maximum width on the West coast near Chillaw and on the East coast near Kalkuda. The berm which is a reservoir of sand which supports the coastline against wave attack is variable around the island depending on the effectiveness of the constructive waves, where the waves deliver large quantities of sand the beach develops negative gradient landwards. The width of the seaward sloping swash zone which is constantly washed by waves is also variable depending on the presence of a berm and energy of the waves. Swash zone gradients range from 2°- 6°, steep swash zones are characteristic of beaches undergoing accretion and also indicate degrading berms. While the swash zone and berm usually seem parallel to one another, at times the boundary between them may be thrown into seaward facing concave cups. Beach cups may be observed during the monsoon and inter-monsoon seasons especially where the swash zone is developing at the expense of the