The Coastal Zone
Longer fetch = more powerful wave
Constructive waves- swash > backwash
Destructive waves- backwash > swash
Freeze thaw weathering
Onion skin weathering
Downhill movement of material acting with gravity
Corrosion - rock dissolves
Hydraulic Action - rocks thrown against cliff
Attrition - rocks erode and become pebbles
Abrasion - material thrown against cliff and erodes the cliff face
Solution disolved chemicals
Suspension - particales carried by water
Traction - large pebbles rolled along seabed
Saltation - hopping of the pebbles along the seabed
Headlands and Bays
Soft rock gets eroded to form bays, inlets along the coastline.
Hard rock, harder to erode and is left jutting out to sea forming a headland
Wave cut platforms
sea erodes cliff face
cliff face unsupported - collapses
Pulled back into sea forming a platform
Caves, Arches, Stacks and stumps
- crack in cliff erodes to form a cave
- cave enlarges to form an arch
- arch erodes to form a stack
- stack erodes and collapses to form a stump
Casestudy - Flamborough Head
Transportation of materials
- Wave approaches beach at an angle
- swash carries sediment up the beach
- backwash carries sediment back into the sea
- continued process carries sediment further up the beach
Bar and Barriers
Bar casestudy - Slapton Ley
Barrier casestudy - Chesil Beach
Hurst castle spit and Keyhaven Saltmarshes
Saltmarsh animal adaptaions
Ringed plover - long legs, webbed feet, camoflage
Oytser catcher- strong beak
Wold spider- strong legs
Butterfly- live higher up in the marshes
Sea oysters and Corgrass - make salt water more seline for other organisms to grow
Sea level rise
Ice glaciers melting
Casestudy- Torres Strait Islands
Holderness Coastline- Mappleton
Mappleton installed Groynes to prevent longshore drift - less build up of material south of the Groynes - cliff collapse - loss of houses, buisinesses, jobs, income
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.
Marsh Creation: Planting vegetation in mudflats reduce speed of waves and creates new habitats. However it’s expensive and it isn’t useful where erosion rates are high.
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.