Coasts as natural systems

Systems - made up of inputs, stores, processes and outputs. These components are linked together by flows of energy and materials through a system.

The coast is an interface between the land and the sea.

The coast is an open system:

• Input - Wind, waves and tides. Products of cliff erosion, sub-aerial erosion, fluvial and glacial processes.
• Storage and processes - Beaches, dunes, salt marshes, cliff and wave cut platforms, longshore drift.
• Output - Energy and material, of which, some is retained within the coastal system and some is transferred out.

Feedback mechanism:

• A process that uses the conditions of one component to regulate the function of the other.
• Done to increase or dampen the change in the system.
• When the process tends to increase the change in the system, the mechanism is known as positive feedback.
• Negative feedback is when the process seeks to counter the change and maintain equilibrium.

Dynamic equilibrium:

• The balanced state of a system when its inputs and outputs are equal.
• If one element changes because of some outside influence, this upsets the internal equilibrium and effects other components of the system.
• By a process of feedback, the system adjusts to the change and regains equilibrium.

Dynamic coasts:

• Coasts are dynamic and they change very frequently.
• These changes are principally caused by changes in energy conditions such as wave energy.
• The morphology of the coast responds to changes in energy because it aims to exist in a state of equilibrium.

All beaches exist in dynamic equilibrium involving four factors:

• The supply of sand
• The energy of the waves
• Changes in sea-level
• The location of the shoreline