Presentation on theme: "Case study: coastal management in Holderness The Holderness coast is 61km long in the north east of England. This is one of the most vulnerable coastlines."— Presentation transcript:
Case study: coastal management in Holderness The Holderness coast is 61km long in the north east of England. This is one of the most vulnerable coastlines in the world and it retreats at a rate of one to two metres every year. About 1.8m of land is lost every year. The problem is caused by 4 main reasons: - Strong prevailing winds creating longshore drift that moves material south along the coastline. - Naturally narrow beaches. Beaches slow down waves, reducing their erosive power and acting as a barrier. Narrow beaches give less protection towards the coast. - The cliffs are made of a soft boulder clay. It will therefore erode quickly, especially when saturated. - The village of Mappleton, perched on a cliff top on the Holderness coast, has approximately 50 properties. Due to the erosion of the cliffs, the village is under threat. In 1991, the decision was taken to protect Mappleton. A coastal management scheme costing £2 million was introduced involving two types of hard engineering - placing rock armour along the base of the cliff and building two rock groynes. Mappleton and the cliffs are no longer at great risk from erosion. The rock groynes have stopped beach material being moved south from Mappleton along the coast. However, this has increased erosion south of Mappleton. Benefits in one area might have a negative effect on another. The increased threat of sea level rise due to climate change, means that other places will need to consider the sustainability of coastal defence strategies for the future.
Case Study: Holderness coast erosion impacts Impacts on people: Homes near cliffs are at risk of collapsing into the sea which means insurance is literally impossible to get. Property prices have fallen The gas terminal in Easington is at risk as it’s only 25m from the cliff and it counts for 25% of britains gas supply. Accessibily to settlements have been affected along the coast as roads have collapsed into the sea, Impacts on environment: Some sites special scientific interest (SSSI’S) have been threatened e.g. Lagoons near Easington. The lagoons are seperated from the sea by a narrow bar however if the bar is eroded the lagoons will be destroyed. Some sites of special scientific interest (SSSI’S) have been threatened e.g. Lagoons near Easington. The lagoons are seperated from the sea by a narrow bar however if the bar is eroded the lagoons will be destroyed.
Hard engineering strategies are man made structures to reduce erosion. (Advantages & Dis-advantages) Sea wall: A wall made out of hard material that reflects waves back out to sea. It prevents erosion on the coast and acts like a barrier. On the other hand it creates a strong backwash which erodes under the wall and is very expensive to build and maintain. Rock Armour: Rock armour are large boulders that are built up along the coast. The boulders absorb the wave energy they reduce the risk of erosion against the coast. They are fairly cheap however they can be moved around by strong waves so they need to be replaced frequently. Groynes: Groynes are wooden or stone fences that are built at right angles to the coast. They trap material transported by longshore drift. They create wider beaches which slow the waves down and give bigger protection along the coast. On the other hand beaches further down the coast suffer as there is no beach being deposited. This means the beaches are narrower and more prone to erosion. Case Study: Holderness coast management schemes.
Soft engineering strategies are schemes to reduce the effects of erosion. (Advantages & Dis-advantages) Beach Nourishment. Beach nourishment is sand and shingles that are added to the beach from out to sea. It creates wider beaches which slow waves down and protect the coast from further erosion. On the other hand taking material from the seabed can kill habitats and is very expensive and has to be managed frequently. Managed Retread: Managaed retreat is removing an existing defence and allowing the land behind to flood. Over time the land will become marshland and new habitats will occur. Also erosion is reduced behind the marshland and it’s cheap. However, people disagree over what land is allowed to flood as flooding farmland would affect farmers. Sand Dunes: Creating dunes by nourishment or plating vegetation provides a better barrier between land and sea as wave energy is absorbed preventing erosion. Also stabalisation is cheap. On the other hand the protection area is limited and nourishment can be expensive.
Case Study: Holderness coast management strategy problems Groynes protect local area but cause narrow beaches to form further down the Holderness coast which increase erosion further down the coast e.g. Cowden Farm is now at risk of falling into the sea. The material produced from the erosion of Holderness is normally transported south into the Humber estuary and down the Lincolnshire coast. Reducing the amount of material that’s eroded and transported south increases risk of flooding in the Humber estuary as there is less material to slow the flood water down. Also the rate of coastal retreat along the Lincolnshire coast has increased because less new material is being added. Spurn head is at risk of being eroded away because less material is being added. Bays are forming between the protected areas and the protected areas and becoming headlands which are being eroded more heavily, which means maintaining the defences in the protected areas is becoming more expensive.