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Coats Revision

The Coastal System

Coastal system is one of inputs and outputs:

1) The cliff system comprising of sub aerial processes of Weathering and Wind erosion

Throughputs comprising of cliff Mass movements of falls, slips and slumps

Outputs of sediment at the base of the cliff which is either deposited there or transported by marine processes.

2) The beach system with inputs of sediment from longshore drift, the cliff and offshore

Throughputs of longshore drift

Output of longshore drift and destructive waves carrying sediment offshore.

Coastal Sediment cells

Areas of the coast usually defined by headlands within which marine processes are largely confined, with limited transfer of sediment from one cell to another, They vary in size depending on the nature of the coast.

Dynamic equilibrium in the coastal system

The relationship between inputs and outputs is constantly changing, one can often outweigh the other. If the system is equal i.e. where the inputs equal the outputs this is known as 'dynamic equilibrium'.

Wave types and characteristics

Constructive waves - Strong swash, weak backwash. Usually have a long wave length and a low frequency of 6-8 waves per minute. They are responsible for berms and beach ridges.

Destructive waves - Weak swash, strong backwash. Small wave length but are quite steep with a high frequency of 13-15 waves per minute. They transport sediment back down the beach resulting in a loss of material.

Most beaches see constructive waves in the summer and destructive waves in the winter which creates a cycle of beach growth and decay.

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