Coastal Deposition & Defence

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  • Created on: 12-11-12 16:38
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Coastal deposition and defence
A spit is an accumulation of sand with one end attached to the land and
the other reaching out across an estuary or into the sea. They are features
of coastal deposition. They are formed where large amounts of sediment
are deposited by longshore drift and where the coastline suddenly
changes direction to leave a sheltered, shallow area of water. Due to an
increase in friction more deposition can occur in the water sheltered by the
headland and the spit slowly builds up to sea level and extends in length.
When the wind changes direction it causes the waves to alter their
direction and this may result in some of the material at the end of the spit
being forced inland to form a curved end. Salt marsh often develops behind
the spit and spits cannot grow across an estuary as the river current carries
material out to sea.
Q.How can government defend us against coastal erosion?
A.It is impossible to prevent coastal erosion but there are measurements
currently in place to help reduce the amount of coastal erosion. These
A sea wall- this reflects waves and can hold the waves breaking on it.
£6,000 per metre.
Revetment- a concrete wall that is laid like a carpet along the coast.
£2,000 per metre.
Gabions- Wire baskets filled with stones. £100 per metre.
Groynes- a low wall that traps sand and reduces erosion. £10,000
Rip-rap- man made boulders that break up the waves. £3,500 per
Beach rebuilding- replaces material lost by erosion. £3 per cubic
Offshore breakwater- protects shore from all waves. £5,000 per
The least effective if that above is generally beach rebuilding as this would
need to be done regularly to keep the beach material maintained. The
most effective are groynes. They are the strongest and one of the only
ways to reduce the amount of beach sediment lost through erosion and
longshore drift.


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