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Of all the earth's natural environments, the coast is the most rapidly changing and dynamic. It can be defined in several ways, but at its simplest, it is the place where land and sea meet and interact. The coast is under numerous pressures due to its pull for economic activity, settlement, recreation and wildlife. Its form is greatly influenced by:
- Terrestrial: Weathering, erosion, deposition, rock type/structure.
- Human: Pollution, recreation, settlement, defences.
- Atmospheric: Climate.
- Marine: Waves, tides, salt spray.
All of the above interact to produce the enormous variety of coastlines found worldwide (from beaches and cliffs to coral reefs).
A beach can be divided into different zones, and the activities that occuron a beach can be placed within particular areas (as shown on the diagram below). The most important function of a beach is to act as a barrier between waves and the coast.
This area is not usually encroached upon by waves - unless storm conditions arise. Sand dunes and cliffs may be found as well as human activities such as golf courses, nature reserves, conservation and buildings.
Foreshore and nearshore:
The foreshore is located closest to the backshore and it is here, due to the breaking of waves that sediment transport may take place. Much of the energy of waves is reduced (dissipated). The nearshore performs similar functions, but usually only at low tide. Activities in this area include, recreation, quarrying, and coastal defences.
There is limited direct sediment movement here as tidal currents are more important than wave action. Sewage outfalls, oil extraction and fishing may occur.
On the beach itself, different features arise as a result of the action and strength of waves on sand and shingle.
Berms are formed as sand/shingleis slowly moved up a beach by successive incoming tides - they are more commonon shingle beaches, whilst ridges and runnels are found more on sandy beaches. Both form 'crests'.
These are associated with large spring tides, where, due to the time of greatest gravitational pull tides are highest (see diagram). Some material is thrown up and beyond the usual high water mark because of the large waves. The material remains at the top of the beach if it is not pulled back down the beach by 'swash'. Storm beaches are more common on steep shingle beaches that are affected by destructive waves.