How does our Coastline Change?

The coast is a scene of 'conflict' between the land and sea. This causes erosion and the creation, transport and deposition of sediment. Through these activities the shape of the land (the coast) slowly changes and the water moves and shapes the sediment eroded from the land. The forces that determine the shore profile; the beach and/or cliff overtime tend to reach a steady state.

The erosion of the coast occurs due to Destructive waves and can cause the formation of headlands and bays, caves arches and stacks and wave cut platforms, all of which are discussed in more detail within the links on the left.

The deposition of material is generally caused by Constructive waves that carrying sediment either up or along the shoreline. These give rise to features such as beaches, sand dune formation, spits bars and tombolas.

Coastal Transport
One other important factor in the creation of coastal landforms is coastal transport.

Material eroded by the sea is carried within the water in a number of ways; minerals dissolved from rocks are carried in solution, whilst small rock fragments, light enough to be held within the water, float in suspension.

The largest rock fragments which are too heavy to be picked up by the waves, are transported by the process of traction, this is where they roll along the bed when the waves pick up enough energy. Finally, medium sized rock particles, which cannot be carried by the waves all the time, are moved by saltation. This is where during times of higher wave energy the particles are picked up and then dropped again as the wave looses its energy.

The main form of transport operating at the coast is that of Longshore Drift. This is the process by which sand and pebbles are moved along a beach by the movement of the waves.

Material is moved up the beach by the swash at an angle which is controlled by the prevailing wind.The backwash then carries material back down the beach at right angles to the coastline under the influence of gravity.

Gradually the material is moved along the coastline, its direction being controlled by the prevailing wind direction. This video show longshore drift in action.