COASTS AS A SYSTEM

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The coast is a SYSTEM

It has INPUTS, PROCESSES AND OUTPUTS of energy

It is an OPEN SYSTEM. That means that it has inputs from outside, like sediment brought down by rivers and outputs to other systems such as sand dunes which migrate inland.

The coastal system is COMPLEX, many of the factors inter-relate and it is also very DYNAMIC, in that it is constantly changing, sometimes within a single day.

 

INPUTS

  • wave energy
  • wind
  • storm surges
  • tides
  • currents (eg rip currents)
  • sea level change
  • sediment
  • human activity
  • tidal waves (tsunamis)

Spatial variations in energy as a result of wind DIRECTION and STRENGTH.

The contribution of storms

Temporal variations - daily, seasonally, annually

 

PROCESSES

  • erosion
  • transportation
  • deposition

HIGH ENERGY COASTLINES

  1. dominated by erosion
  2. high wave activity
  3. coast exposed to prevailing wind
  4. long fetch

example of a UK high energy coastline Orkeney Islands, NW Scotland

wave direction map

OUTPUTS

  • erosional landforms: cliffs, wave cut platforms, headlands and bays, caves, arches, stacks, blow holes
  • depositional landforms: beaches, sand dunes, spits, bars, tombolos, mudflats, salt marshes, coral reefs

 

 

LOW ENERGY COASTLINES

  1. dominated by deposition
  2. sheltered
  3. low wave activity

example of a UK low energy coastline Shetland Islands

Sediment Cells

Where does the sediment come from?

Beach sediments can come from

  • cliff sources, for example Flamborough Head in Yorkshire

  • off shore bars of sediment, brought onshore by wave action

  • brought down by river systems, for example Morfa Harlech sand dune system in Cardigan Bay

  • relic sources from the last glaciation