Case Study of Coastal Erosion and Coastal Defence:
The Holderness Coast, NE Yorkshire Coast
Where is the Holderness Coast? What is the problem?
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The Holderness Coast is on the NE coast of the UK, facing the North Sea. |
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The coastline is mainly made up of cliffs (20-30m high), consisting of soft, easily eroded boulder clay. Where the cliff line meets the Humber Estuary, a spit has formed due to the change in the direction of the coastline - Spurn Head. |
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The cliff line is retreating at an alarming rate - greater than 1m / yr (fastest rate in Europe) - 4km of land have been lost since Roman Times, including many villages and farm buildings. |
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Easington Gas Station (a North Sea Gas terminal) is situated on the cliffs top and its position is under threat. |
Why is Cliff Erosion such a problem here?
1. The cliffs are made up of soft glacial material (Boulder Clay - made up of sands and gravels). This is easily eroded by the waves and the cliffs are easily undermined.
2. The Holderness Coast is very exposed, approaching waves have a long fetch over the North Sea.
3. The waves are mainly destructive - eroding the base of the cliffs (hydraulic action etc.)
4. Most of the Material eroded from the cliffs is washed out to sea, the rest is moved by longshore drift - the beaches are therefore narrow and do little to protect the coastline. (If the beaches were wider, the waves would break on the beaches reducing their erosive power).
5. The coastline is threatened further by sea-level rise.
Attempts at Coastal Management along the Holderness Coast include:
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use of groynes to trap moving beach material and provide a protective beach in front of the cliff |
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the construction of sea walls and revetments as wave-resistant structures at the base of the cliffs |
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artificial off-shore breakwaters like tyres and concrete blocks, forcing waves to break off-shore. |
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sea wall used to protect Easington Gas Station (cost £4.5 million) |
Due to extensive costs - only the most valuable areas of land are protected. Much of the area is farmland which is not protected.
Example of the impacts of Coastal Management: Mappleton
The village of Mappleton is greatly underthreat by coastal erosion along the coastline and by 1998, the main road running through the village was only 500m from the cliff top and in places it is now only 50m. The village is under threat due to the easily eroded boulder clay (glacial till) which makes up the cliff line. The area suffers from erosion rates of up to 2m per year.
Protecting Mappleton
To reduce the amount of erosion threatening Mappleton, 2 rock groynes were constructed in 1991 to encourage the build up of beach in front of Mappleton by trapping longshore drift. This meant that that waves would break on the beach rather than attacking the cliffs.
Problems for further down coast
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Those living south of Mappleton village have experienced the 'knock-on' effects of the coastal management. |
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The groynes at Mappleton have disturbed the natural longshore drift movement, trapping the coastal material. |
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Therefore whilst material is still being moved south of Mappleton, there is no fresh sediment to replace it. |
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Beaches have become even narrower and the cliffs are unprotected. |
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Estimates suggest that it has accelerated cliff erosion south of Mappleton to 10m / yr. |