The Coastal Zone

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  • Created by: Catherine
  • Created on: 25-03-13 20:17

The Coastal Zone

Longer fetch = more powerful wave

Constructive waves- swash > backwash

Destructive waves- backwash > swash

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Freeze thaw weathering

Onion skin weathering

chemical weathering

Biological weathering

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Mass Movement

Downhill movement of material acting with gravity



Rotational Slip


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Coastal Erosion

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

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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

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Wave cut platforms

sea erodes cliff face

cliff face unsupported - collapses

Pulled back into sea forming a platform

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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

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Longshore drift

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
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Bar and Barriers

Bar casestudy -  Slapton Ley

Barrier casestudy - Chesil Beach

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Spit casestudy

Hurst castle spit and Keyhaven Saltmarshes

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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

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Sea level rise

Ice glaciers melting

Casestudy- Torres Strait Islands

 Cause- Flooding

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Coastal Erosion


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

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Soft engineering

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.

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Hard Engineering

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.

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