Coastal Defences

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  • Topic: North Norfolk, Coastal management, Rock
  • Pages : 3 (733 words )
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  • Published : March 25, 2013
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Sea Walls are an example of Happisburgh’s coastal defences. They reflect the energy of the waves back into the sea and work best at high tide. But as the wave backwashes; it erodes the base of the wall. This area weakens and could eventually collapse A sea wall will be necessary at a large beach, as the sea wall will come into actions during high tides and storm surges Cost= £2000-£5000 per metre

Timber Groynes are mainly used to act against long-shore drift. They do this by interrupting the sediment’s course with perpendicular dividers. They also can help to build up the beach as they encourage to backwash to flow parallel to the groyne, lengthening it Impermeable groynes do not allow any material to pass through them and this deprives parts of the beach of sediment. Permeable groynes allow some sediment to pass through them and build up down-drift sides Cost = £1000 per metre Found in Cromer, Overstrand, Trimingham and Sheringham

It should last for 100 years, but if it gets damaged it needs to be repaired every 20 years Sea Walls are found in Sheringham, Cromer, Cart Gap and Mundesley

North Norfolk Coastal Defences Revision Guide Side 1

Rock armour absorbs the energy of the waves like revetments but use hard igneous and metamorphic rocks to last longer and resist erosion better. Rock is also used to build groynes known as Rip-Rap The wave hits the rocks and pass around them with less energy to erode the coastline. This means that the beach behind the armour is kept nourished and allows an even spread of sediment Easy to replace moved rock if there’s a storm. Often used to protect the sea walls and it provides support and stability to the base Cost = £1200 per metre As it costs the same amount as revetments, they are better value for money as they last 100 years. Although their main drawback is aesthetics Found in Sheringham

Timber revetments break the force of the wave and are built at the front of the beach, to absorb wave energy during high...
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