The isle of wight

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  • Created by: nr2021
  • Created on: 15-10-19 17:35
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  • Case Study: Isle of Wight
    • Home to 138000 people and 2/3 of the population live in around 2 meters from the coast.
    • Example town: Ventnor
      • Due to long fetch from the Atlantic ocean, there are high energy destructive waves.
        • They rapidly erode cliffs/beaches through hydraulic action and abrasion.
      • This is town is built on impermeable clay that is less resistant and is at risk of erosion and slumping.
        • Erosion rate is 0.46m/year, estimated to increase to 0.61m/year between 2025 and 2055 and to 0.71m/year between 2055 and 2085.
      • Further mass movement and erosion were caused by severe winter storms which brought storm surges and heavy rainfall.
      • This town experiences high energy destructive waves due to long fetch from the Atlantic Ocean which was rapidly eroding the cliffs and beaches by hydraulic action and abrasion.
      • Undercutting by waves and slumping meant that cliffs were at risk of landslides.
      • Existing sea defences are no longer effective and need replacing e.g. sea walls are crumbling and at risk of collapsing.
      • The town is a coastal resort attracting thousands of tourists each year, bringing jobs and income. There are many tourist attractions such as the victorian heritage museum and blackgang chine amusement park. If coastal erosion affects these there will be fewer attractions therefore a huge loss for the tourism industry.
      • People are forced to move away as over 10 million pounds of property located close to the retreating cliffs however many of these houses are unsellable due to their high risk.
      • There was a risk of life due to the dangers of rock falls and landslides which harms families and the whole community.
      • Cliff collapse and landslides could affect properties up to 200m inland with massive socio-economic coats causing damage to buildings, disrupting services and breaking utilities such as water mains and electricity connections.
      • The main east-west road and railway routes pass close to eroding coastlines. If they were to get damaged it would cause widespread disruption to transport and cost millions of pounds to repair. Businesses would be affected and it would make it extremely difficult for people to access services.
      • Hard Engineering Strategies:
        • A series of limestone rock groynes were built at 100 m intervals at the base of the cliffs, which was meant to increase deposition by trapping sediment thats was being transported by longshore drift. This would build up the beach and would add protection by dissipating wave energy and reducing abrasion and hydraulic action.
          • Positives: The beaches attract more tourists and the rock groynes are longer lasting than wooden groynes.
          • Negatives: Since it stops the longshore drift process, beaches further down the coast receive less sediment, increasing the rate of erosion there. It also has a unattractive appearance.
        • At Wheeler's Bay, rock revetment and concrete tetrapods were applied. 15000 tonnes of resistant Norwegian granite were put in front of the existing sea wall. They absorb and reflect the energy of the waves, preventing the chalk cliffs behind from being eroded by abrasion and hydraulic action.
          • Positives: They don't require as much maintenance as a sea wall and last longer. Furthermore, it maintains the sea wall that can be used as a footpath and cycle route to support tourism. Its also a place for recreational fishing. Property values increased and are worth more than the cost of the sea defences.
          • Negatives: It is expensive at 1.2 million pounds to build and also has an unattractive appearance. Tetrapods can restrict access to the beach and can be hazardous to boats on the water.
      • Soft Engineering Strategies:
        • Beach nourishment was applied at monks bay- 40000m3 of sand and gravel were added, which extends the beach, dissipating wave energy therefore reducing erosion of the cliffs by abrasion and hydraulic action.
          • Positives: Its relatively cheap to carry out compared to other hard engineering techniques and is natural. It provides a beach for tourists. Its carried out during winter moths so has a smaller impact on tourist activity as well as wildlife breeding.
          • Negatives: Dredging of sand and gravel is required offshore which disrupts marine habitats. Regular replenishment is also required which makes it expensive. Furthermore its largely ineffective at preventing erosion of the cliffs and is visually, environmentally intrusive when carried out.
    • Its located at the south of England, to the east of Bournemouth and the west of Portsmouth.

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