The Negative Impacts of Groynes and Revetments on the Beaches

The Negative Impacts of Groynes and Revetments on the Beaches
They spoil the natural scenery (visual pollution). They are expensive to build and maintain. They can cause accelerated erosion further along the coast if they starve areas of beach material by maintaining a beach at that point. Old metal groynes can go rusty and cause accidents for holidaymakers. Therefore local authorities have to consider all these implications before investing in expensive coastal management and protection schemes. Our coastline is constantly changing and is under threat from both the physical processes of weathering and erosion and human pressures caused by its use as a popular recreational area for holidays and day trips. In the UK local authorities like Norfolk have tried to protect our coasts by managing them to stabilise cliffs and slow down their erosion, to slow down the loss of beach caused by longshore drift and to prevent damage to fragile coastal environments caused by trampling and litter. Management basically means to look after and protect. They have done this in a number of ways.
Where the erosion of cliffs is seen as a serious problem because of its speed, or the land and buildings it threatens are seen as important or valuable, then attempts have often been made to slow down or stop the erosion. These can include one of a number of methods. Sea walls made of concrete or stone prevent waves from hitting the bottom of the cliff but are expensive to construct and spoil the natural appearance of the coast. This has a negative impact on the visual landscape of the area. Gabions are wire cages filled with stones that act like a sea wall but are much cheaper and can look more natural. A beach is the best protection for a cliff and where beach material is being lost through longshore drift. Breakwaters or groynes being built can slow longshore drift down. Groynes are walls that stick out into the sea at right angles. They can be made from wood, concrete or stone boulders. They encourage the local build up of sand on one side but can result in a loss of material on the other side, which can have effects further along the coast. This is one of the negative impacts that your question refers to. As to the cost of any of these options, they might involve both building and maintenance costs, in both the short and longer term. Each situation is different so it is very hard to say how much each type of structure would cost. Presumably you must have some information about the Norfolk coast and the management methods that have been used there so that you can answer the question. If not here are a few sites to research on: http://www1.npm.ac.uk/lois/Education/defen.htm Labelled diagrams of methods of coastal protection. http://www.angliacampus.com/tour/sec/ge A Hi Pritesh, An interesting question! First you need to consider erosion by wave attack. If the sea defences are a substantial sea wall with a wide beach in front ( possibly kept there by groynes), then the waves should no longer reach the cliff and so they cannot erode it. If the defences are less than this, gabions (wire cages filled with stones) or rip rap (natural or concrete boulders) then high tides and strong waves might go over the defences or damage them. Next you need to think about water erosion. Unless you completely cover the cliff face with something like concrete, then water is still going to run down it when it rains and cause erosion. How much depends on how weak or strong the rock of the cliff face is. This can lead to gullying which can wear back the cliff face as quickly as waves. Finally, you could conclude your answer by considering the effect that protecting the coastline in one place has on other places. If you build groynes to hold back longshore drift on one part of the coastline, it no longer supplies the beach further along. Here the beach can become narrow and disappear, taking away the cliffs natural protection from wave attack and leading to faster erosion. Good sites to research this would be: og/coastal/page13.htm#28 Detail on coastal protection with photos. Ben - There are a variety of coastal defences that can be implemented in order to help save a coastline. Each one has its benefits and costs - like visual impact, cost and how long it is expected to last. The schemes include: 1. Gabions ? wire cages filled with pebbles that are built into a wall to protect or reinforce a cliff or coastline. 2. Groynes ? built at right angles to the coastline, to try to prevent the transportation of material via long shore drift. 3. Revetments ? wooden fences built at 45 degree angles to try to reflect wave energy 4. Bore holes and drainage systems ? to stop the cliffs from becoming saturated with water and slumping due to the weight 5. Sea walls 6. Do nothing ? let nature take its course and surrender the land to the sea. It seems like you know the example that you have been set well. Think about each of the above, and try and decide which one(s) would be best suited to this area of coast and why! This is quite an involved subject, because it concerns not only the environment and people?s livelihood, but also economics! Arguments against include: 1. Defences against erosion interfere with natural processes, and in the end even the defences will get eroded away. You may even make matters worse further down the coast. [Eroded material on our east coast actually gets transported to the other side of the North Sea and helps to protect the Dutch coast]. 2. It costs too much money to defend coasts, unless there are particularly valuable things to defend, like a town or a nuclear power station. 3. Defences are ugly, creating ?visual pollution? e.g. groynes down a beach, high sea walls etc. 4. They may alter or damage wildlife habitats. Arguments for include: 1. You need to defend certain land uses and installations which, if destroyed, would cost a great deal of money to replace. 2. Beaches need to be protected to keep holidaymakers in a resort. 3. Some wildlife habitats might need protection against increasing danger from erosion due to rising sea levels. The government now thinks that it is too expensive to protect coastlines except where particular things need to be preserved for economic reasons.

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