The Holderness Coastline


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The factors that have led to the Holderness coast suffering from erosion and the potential costs of this eroding coastline. Perfect for AS Level Geography.

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The Holderness Coastline

  1. 1. The factors that have led to the Holderness coast suffering from erosion and the potential costs of this eroding coastline The Holderness Coastline ______________________________________________________
  2. 2. An Overview of the Coastline <ul><li>This area of coastline is found between Flamborough head and Bridlington on the Yorkshire Coast. </li></ul><ul><li>On average, over 2 metres of coastline is lost every year and since roman times it has lost 4km of land, and 29 villages, with this number rising even now. </li></ul>
  3. 3. The Factors Affecting Erosion <ul><li>There are three main reasons for this erosion: </li></ul><ul><li>1. Geology (rock type) </li></ul><ul><li>2. The fetch </li></ul><ul><li>3. Longshore drift and beach material </li></ul>
  4. 4. Geology The two main types of rock on the Holderness coast are Boulder clay and chalk The boulder clay has very little resistance to erosion, especially when wet, making it very susceptible to erosion
  5. 5. Fetch <ul><li>Holderness is exposed to winds and waves from the north-east, which have a small fetch of about 500-800km. This is not far, but the coast at Holderness is attacked by other factors, affecting the ferocity of the waves. </li></ul>
  6. 6. Factors Affecting the Fetch <ul><li>Currents – or swell – which circulate around the UK from the Atlantic and into the North sea. The Atlantic fetch is 5000km or more, and its currents add energy to waves in the North sea. Therefore, there are often powerful destructive waves along this coastline. </li></ul><ul><li>Low pressure weather systems passing over the North sea are often intense, and locally produce very strong winds and waves. </li></ul><ul><li>Small, almost enclosed seas , like the North sea, often generate huge waves during storms. Waves move within the sea but cannot disperse their energy – rather like water slopping up against the side of a washbasin </li></ul><ul><li>The sea floor is deep along the Holderness coast. Therefore, the waves reach the cliffs without first being weakened by friction with shallow beaches. </li></ul>
  7. 7. Longshore Drift and Beach Material <ul><li>The beaches at Holderness are its main problem. Boulder clay erodes to produce mainly clay particles, which are easily transported out to sea, rather than accumulating close to the cliffs as beach sand. Although there are beaches, there is never enough sand to stop the waves reaching the cliff base at high tide. </li></ul><ul><li>What little sand is produced is taken southwards by longshore drift, leaving the Holderness cliffs poorly protected against wave attack. Eventually, a small amount of beach material reaches a spit at Spurn Head, where it accumulates. </li></ul>
  8. 9. Managing Erosion at Holderness <ul><li>Hard Engineering Techniques: </li></ul><ul><li>Wooden groynes at Hornsea </li></ul><ul><li>These have been built to trap sediment carried by longshore drift, keeping the beach in place at Hornsea, which in turn protects both the cliffs and the town. </li></ul><ul><li>However, south of Hornsea the village of Mappleton was being starved of sediment being trapped due to the groynes. Waves eroded the cliffs so much in the early 1990’s that nearly 4 metres was being lost every year and the village was in danger of disappearing. </li></ul>
  9. 10. <ul><li>Rock Groynes at Mappleton </li></ul><ul><li>After a campaign by residents to protect Mappleton, Humberside council built two rock groynes to protect the village. These are boulders of granite, laid out like groynes, and cost almost £2million. The cliff face was also rebuilt to make it less steep and therefore more stable. </li></ul><ul><li>After this, at Cowden (3km south of Mappleton) sediment starvation was also causing these cliffs to be eroded, with the rate of erosion increasing from 2.5 metres per year in 1991 to 3.8 metres per year in 2007. This process is called terminal groyne syndrome and happens frequently when groynes are stopped. </li></ul>
  10. 11. <ul><li>Revetments at Easington </li></ul><ul><li>A rock revetment has been built to protect Easington’s gas terminal. Like stone groynes, a revetment consists of large granite boulders. The boulders are placed like a wall in a line of defence along the shoreline/ It works by absorbing – not reflecting – wave energy using large air spaces between the boulders and a broad surface area. Revetments are very expensive but lone lasting. </li></ul>
  11. 12. <ul><li>Soft Engineering Techniques </li></ul><ul><li>Beach nourishment at Hornsea </li></ul><ul><li>This had added sediment to the beach at Hornsea, by dredging and pumping from offshore straight onto the beach. </li></ul><ul><li>This was to: </li></ul><ul><li>- create a wider beach to protect the cliff line </li></ul><ul><li>- to add sediment into the coastal system so that areas downdrift benefit. </li></ul><ul><li>The downside is that its sediment can be taken away in a single storm, and so it has to be replenished every one or two years. </li></ul>
  12. 13. <ul><li>Coastal Zoning </li></ul><ul><li>This is also known as red-lining, and is a device used by planners to divide stretches of coast into land use zones. Red-lining identifies those zones at risk to erosion where the costs of protection exceed the possible benefits. Decisions are then made as to which areas need protecting, and zones that are decided to not, are denied planning permission for anything along the coast that may protect the coast. </li></ul>