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- Coasts: people, defences and Holderness
Coasts: people, defences and Holderness
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People live, work and build on the coast. Protecting it costs money and can cause problems further along the shore.
Hard engineering
Sea walls: concrete walls, often curved, that reflect waves. They work well but are very expensive.
Groynes: wooden or rock barriers built down the beach. They trap sediment moving by longshore drift, so the beach grows, but beaches further along the coast get less sand and erode faster.
Rip rap (rock armour): large boulders that absorb wave energy.
Groynes: wooden or rock barriers built down the beach. They trap sediment moving by longshore drift, so the beach grows, but beaches further along the coast get less sand and erode faster.
Rip rap (rock armour): large boulders that absorb wave energy.
Soft engineering
Beach nourishment: adding sand or shingle to a beach so it absorbs wave energy. It looks natural but must be repeated.
Managed retreat: allowing the sea to flood low-value land, which becomes salt marsh and acts as a natural defence.
Soft engineering works with nature and usually costs less, but it does not stop erosion completely.
Managed retreat: allowing the sea to flood low-value land, which becomes salt marsh and acts as a natural defence.
Soft engineering works with nature and usually costs less, but it does not stop erosion completely.
Example: the Holderness coast
The Holderness coast in East Yorkshire is one of the fastest-eroding coastlines in Europe.
Its cliffs are made of soft boulder clay (till) left by glaciers, which slumps easily, and powerful North Sea waves attack it.
At Mappleton, rock armour and two rock groynes were built in 1991 to protect the village and its road. The beach there grew, but erosion increased to the south, because less sediment reached it.
Sediment carried south by longshore drift builds the spit at Spurn Head.
Its cliffs are made of soft boulder clay (till) left by glaciers, which slumps easily, and powerful North Sea waves attack it.
At Mappleton, rock armour and two rock groynes were built in 1991 to protect the village and its road. The beach there grew, but erosion increased to the south, because less sediment reached it.
Sediment carried south by longshore drift builds the spit at Spurn Head.
Give one advantage and one disadvantage of groynes.
- Advantage: they trap sediment, building a wider beach that protects the cliff.
- Disadvantage: less sediment moves further along the coast, so beaches there shrink and erosion increases.
Answer: They protect one place but can increase erosion further along the coast.
Hard engineering (sea walls, groynes, rip rap) is strong but costly and can move the problem along the coast. Soft engineering (beach nourishment, managed retreat) works with nature. At Holderness, soft boulder clay erodes fast; the 1991 Mappleton groynes increased erosion to the south.
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