3.3.2

Coastal Retreat

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Coastal Recession

The rapid recession of coastlines is caused by a combination of physical and human factors.

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Dredging

  • Dredging involves the removal of sediment for use in construction. But this process has been linked to increased rates of coastal retreat.
  • Removal of the sediment causes the depth of the ocean to increase.
  • This can cause an increase in the occurrence of destructive waves at the coast because they can maintain their energy further towards the shoreline.
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Hard engineering

  • The construction of hard engineering structures at the coastline can disrupt sediment cells.
  • This means that by disrupting one bit of coast, areas further along the coast may be starved of sediment supply, which can then result in the destruction of beaches.
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Dredging in California

  • Dredging along the coastline of California has had long-term implications on the supply of sediment to the Santa Barbara littoral cell.
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Subaerial processes

  • Weathering and mass movement processes combine to increase the rate of coastal recession.
  • Long periods of rainfall weaken rock structure and in turn, leads to mass movement of material.
  • This collapsed material is then eroded and transported away by wave action.

Rate of Coastal Recession

The rate of coastal recession varies and caused by several factors. These include: short and long-term wind direction, tides, seasons, weather systems and storm occurrence.

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Wind direction

  • Wind direction controls the movement of waves, influencing the rate of coastal erosion.
  • A dominant wind direction causes powerful destructive waves to attack the coastline.
    • E.g. the south-westerly wind directing waves across the Atlantic Ocean towards Land’s End in Cornwall.
  • This happens because the waves have travelled a long distance, influenced by the dominant wind, which is linked to the fetch of a wave.
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Tides

  • Tides are linked to gravitational pull. When the pull is at its strongest, there are high tides. When the pull is at its weakest, there are low tides.
  • During periods of high tide, the rate of coastal recession can increase because waves can reach further towards the shore.
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Seasons

  • During the winter season, the rate of coastal recession tends to be greater than during the summer season.
  • This is because winter brings stormy weather, linked with higher tides and long wave fetch.
  • The average rate of erosion increases at this time of the year.
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Weather systems

  • Weather systems are influenced by areas of high pressure, creating anticyclones, and areas of low pressure, creating depressions.
  • Increased belts of high pressure reduce the rate of coastal recession because this leads to calmer weather.
  • Belts of low pressure systems cause unsettled weather conditions.

Jump to other topics

1Tectonic Processes & Hazards

2Option 2A: Glaciated Landscapes & Change

3Option 2B: Coastal Landscapes & Change

4Globalisation

5Option 4A: Regenerating Places

6Option 4B: Diverse Places

7The Water Cycle & Water Insecurity (A2 only)

8The Carbon Cycle & Energy Security (A2 only)

9Superpowers (A2 only)

10Option 8A: Health & Human Rights (A2 only)

11Option 8B: Migration & Identity (A2 only)

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