Tuesday, January 17, 2012


When managing the coastline there are two main options:

- this is where man made coastal defence structures are used to reflect large amounts of wave energy and hence protect the coastline.

- this is where beaches or naturally formed materials are used to control / re-direct erosion processes.
Hard Engineering Techniques:
1. Re-Curved Sea Wall
- concrete wall which is curved on the underside to deflect the power of the waves
- these can be very expensive (up to £1-2 million per km) and the deflected waves can scour material at the base of the wall causing them to become undermined
- these are however a very effective means of preventing erosion and they reflect rather than absorb wave energy.

2. Rip Rap
- large boulders on the beach absorb wave energy and break the power of the waves
- although movement of the boulders is expensive this can be a much cheaper method than some other solutions
- the boulders can however be undermined easily by waves washing away sand and shingle beneath them. They also can be quite ugly, changing the appearance of a coastline.

3. Groynes
- these structures (usually either wooden or steel) are designed to top longshore drift and therefore act to build up and anchor beach material, protecting the base of cliffs.
- they are effective at reducing erosion in the area they are constructed in by causing significant build up of beach material
- groynes may however starve areas further down the coast of material by stopping longshore drift, resulting in an increase in erosion in these areas

4. Gabions
- these cages of boulders are built into cliff faces to protect the cliff from the force of the waves;
- they are cheaper than sea walls and can be very effective where severe erosion is a problem
- they are however visually intrusive

5. Revetments 
- these wooden structures break the force of waves and beach material builds up behind them
- they are cheap and effective at breaking waves
- as well as being visually intrusive however they do need replacing more frequently than most other defense methods.

Soft Engineering Techniques
Soft engineering includes beach replenishment in which beach material is added to provide a "natural solution". Environmentally this is a preferred option as it maintains the beauty of the landscape and avoids visual intrusion, however it can be expensive to maintain as longshore drift continues to move beach material down the coast and therefore regular replenishment is required.

Sand Dunes and salt marshes can also be encouraged to act as natural barriers to the waves. 

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