Coastal Retreat
Geography: Edexcel A Level, topic 3.3.2
Coastal Recession
The rapid recession of coastlines is caused by a combination of physical and human factors.
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.
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.
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.
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.
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.
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.
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.
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.
Test yourself on Coastal Retreat
Which of the following is a subaerial process that increases the rate of coastal recession?
What does dredging involve?
Impacts of Dredging
Which of the following controls the movement of waves and influences the rate of coastal erosion?