Coastal Erosion

Simon Abbott

With Reference to examples discuss the view that coastal erosion is caused by human intervention as a posed to natural processes.

For many decades the approach to rapid coastal erosion was to build up sea defences, to try and slow down or even stop the erosion. Initially the attempts were thought a success, however after some years it was realised that the power of the sea and waves could overcome human attempts. Only could protection be a success if huge costs were going to be involved. Many methods around the British Isles have taken place in he last 50 years with many failures occurring. It is very rare to find a coastline that shows a decrease in the rate of erosion over many years after defences are in place. In fact in places the defences seem to have speeded up the erosion process. Coastal erosion is a natural process of erosion, transportation and deposition, interfering with this balance could be to blame for the rise in erosion on the coasts of some areas.

Groynes have been built out to sea in many areas of the British coastline. Their aim is to trap material and thus slow down the rate of longshore drift. However, these groynes in some areas are been blamed for the rise in erosion rates further down the coast.

On the Holderness coastline in Humberside, erosion is taking place at a rate of about 2 metres per year. Along this coast there is a strong action of longshore drift taking place, which over centuries has produced a spit to form on the southern tip of Holderness, called Spurn Head spit. The spit is over 4km long and 100 metres wide. The majority of this coastline is glacial till, a soft fragile material, which is easily eroded. This however is not thought of as the only reason for the rapid rates of erosion. Human interference is thought to be another cause, as a result of the sea defences put in place. A rock groyne was built at Mappleton, to create a wider beach. This in turn would help protect the coastline, by absorbing the wave energy. Then at Withernsea a concrete sea wall with a splashback and boulder rip-rap in front of it was created. These defences were to cause great problems. The groyne meant that material moving down the coast by longshore drift would get stuck behind the groyne. This protected the initial area as a beach was created. Although this meant less material was heading further down the coast than it had done in the past, it created a beach as it was trapped. The sea wall and rip-rap protected the initial area, by stopping the erosion. Although in turn this meant less material was been carried down the coast, because there was less been eroded by the sea. The beaches along the Holderness coast were already very small, as only 30% of the glacial till eroded is heavy enough to be deposited and form a beach. The beaches down coast of the defences began to shrink in size, as material usually deposited there was either not eroded, or stuck behind the groyne. This meant that the waves concentrated all their energy on the base of the weak cliff, because the beaches were not big enough to absorb the waves. This caused the cliffs to erode at a faster rate, threatening many buildings once thought of as safe. At Easington, the Gas terminal is under threat sitting right on the edge of the cliff, with no beach to protect it. They will either have to move it, or build some of their own sea defences. Cowden Farm just down the coast from the Mappleton groyne, is starting to fall into the sea. Here erosion increased as a direct result of the defences, there is almost visibly no beach remaining at the foot of the cliff. Many other properties have already fallen into the sea or are about to do so soon.

Gravel extraction occurs in many offshore areas around Britain, gravel is removed in large volumes for commercial purposes each year. More than 20 million tonnes were been dredged in 1989. The removal of this gravel was thought to be a good method, as no extra quarries would have to open therefore creating no protests from any local people. The problem is removing all this sand and gravel is leading