Human influences at the coast
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Human influences at the coast
Humans are drawn to the coast, initially for ease of transport and industry, but increasingly for recreation purposes. The result is a need to manage and control both coastal erosion flooding which is difficult, given the dynamic nature of coastal environments.
This spans the vast array of measures, which are outlined below, and is subject to large amounts of controversy. In the UK, there are numerous organizations involved in the management of the coastline, ranging from the National Trust to the Department for Environment, Food & Rural Affairs (DEFRA).
Maritime and district councils (approximately 120) tend to coastal protection, whilst the Environment Agency is responsible for management of coastal flooding. As a result, approaches are rather disjointed. The best protection for a coast is always a beach.
These are structures that try to limit the impact on waves and their energy on a stretch of coastline. For example, a sea wall rebounds a wave's energy back to sea, limiting the impact of the waves. They are contentious due to cost and impact on other areas of the coast but do allow a reduction of cliff erosion.
Hard engineering approaches are seen at the base of cliffs (sea walls and groynes), or on the cliff face (drainage and pinning).
Aims of approaches, advantages and disadvantages:
|Sea walls||To limit erosion by creating a barrier.||Effective defence against erosion and flooding.||Reflected energy picks up sediment, which then is used in 'scouring' and can undermine the sea wall. Very expensive £2000+ per metre. Other areas left exposed.|
|Revetments and Rip Rap||To dissipate (reduce) wave energy.||Cheap and less unsightly than sea walls. Allows for more build up of sediment to protect the beach.||If wooded have a short life span. Beach scouring still occurs.|
|Groynes||Limit longshore drift, increase sedimentation rate, build up beaches.||Very efficient in trapping sediment.||Sediment input lower down coastline is reduced, limiting protection offered to cliffs lower down coast. Rapid cliff erosion can occur. For example, Barton on Sea.|
|Breakwaters||To break waves further out to sea, reducing their energy at the coast.||Effective and have less impact on other areas of the coast line.||Costly as they need to be very strong. Can be short-lived. Appreciation of local tidal conditions vital for success.|
|Cliff modification||To reduce cliff height and slope angle, reducing mass movements.||Long term solution.||Careful planning needed, and rock falls, for example, can still occur.|
|Cliff drainage||To stabilize cliffs by reducing weight of water.||Widely applicable in the UK.||Alters cliff hydrology which impacts on ecology.|
|Gabions||Stabilize foot of cliff and help drainage.||Cheap and relatively quick to install.||Unable to be used where they would be subject to wave erosion.|
Viewed as more environmentally friendly, as this approach tries to work with natural processes to reduce, rather than prevent erosion.
Approaches, aims, advantages and disadvantages:
|Beach replenishment||To build up beach via dumping sand, creating a larger area over which energy is dissipated. For example, Sherringham Norfolk.||No costly building involved, cheap and long term||New material (sand) must match the original type. Offshore dredging alters wave approach and refraction. Materials from quarries are expensive.|
|Stable bays||Bay created to trap sediment.||Works with natural processes, less expensive than hard engineering.||New approach, little known about its success.|
Sometimes seen as the 'do nothing' approach. Nature is allowed to take its course. In the UK arguments for this include the fact that coastal protection is costly and increasing. Managed retreat is cheaper and more environmentally friendly.