The Isle of Wight
Managing the Coast
Sandown is made from wealden which is either sand stone or clay. These two materials are easily eroded. Large quantities of sediment which replenishes the beach of the bay but much is also transported away eastwards. The sandy shoreline is essential to the tourist economy of the town and must be sustained.
The Undercliff made out of Green sand and soft rocks, including chalk.There were two main landslides after the last Ice age (8000–4500 years and 2500–1800 years ago). The main section is more stable, though there are on going concerns over coastal erosion. The main through road, Undercliff Drive, was disrupted by a mud slide near St Lawrence in 2001, requiring 18 months to build a new road section and in 2014 more erosion after heavy rain fell and the road was under repair, leading to more damage, and nine houses being evacuated.
River Medinsi helping deposition in that area. Sediments, soil and rocks are added to a land form or land mass which is carried through the water of the river. Wind, ice, and water, as well as sediment flowing via gravity, transport previously eroded sediment, is deposited, building up layers of sediment.
There are many different materials in the sea, these can be, eroded from cliffs,transported by long-shore drift along the coastline and brought inland from offshore by constructive waves. Even by being carried to the coastline by rivers. The waves always come to the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash lets it go back to the sea in a straight line at 90° because of gravity.Continual swash and backwash transports material sideways along the coast. This movement of material is called long-shore drift and occurs in a zigzag.
In constructive waves swash is stronger than backwash. Deposition is greater than erosion, there is a smaller fetch and weaker winds. Destructive waves have a weak swash and a stronger backwash, erosion is greater than decomposition. There is a large fetch and stronger winds.There are four ways that waves and tidal currents transport sediment. These can then contribute to the movement of sediment by long-shore drift.
Solution - Is when minerals are dissolved in sea water, this is called a solution, it not visible in the water. This solution can erode from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution which is what most of the isle of wight is made from.
Suspension -Small particles are carried in water such as clay can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds which generate high energy waves.
Saltation- small pieces of shingle or large grains of sand is bounced along the sea bed. Currents cannot keep the larger and heavier sediment a float within the sea for long periods.
Traction -Pebbles and larger sediment are rolled along the sea bed leading to a build up.
Monks bay: Offshore breakwater, six rock groynes, beach nourishment using 17,000 cubic metres of sand and gravel and rock revetment to reinforce the existing sea wall. 25,000 tonnes of Swedish granite
Wheeler Bay: 5, 500 tonnes of Norwegian granite was placed seaward of the existing defenses to form a rock revetment and the coastal slopes were regraded to make a shallower profile before installing land drainage.
Seagrove Bay: The £900,000 scheme included a new concrete sea wall, with 200 meters of rock revetment placed in front of the wall to dissipate the energy of the waves. Rock groynes were constructed as a further layer of protection. Mass movement on the soft clay cliffs has significantly reduced by installing land drainage.