COASTS

COASTS

Erosion
1. Weathering
  1. Freeze thaw - water gets in cracks and freezes, expanding the crack
  2. The breaking down of man made things by weather
2. Mass Movement
  1. The downhill movement of material under the influence of gravity
  2. Impacting factors:
    1. Undercutting the cliff
    2. Building on the cliff top increases the weight
    3. Rain saturates the rock which increases the weight
    4. Weaker rocks (eg. clay) are more likely to collapse than srong rocks (eg. granite)
3. Coastal erosion
  1. Hydraulic action - waves trap air in rock forcing it apart
  2. Abrasion - rocks thrown at cliff face by waves scraping it away
  3. Attrition - rocks bump into each other and get smaller
  4. Solution - sea water dissolves the rocks
4. Erosional landforms
  1. Headlands and bays
    1. Soft rock (eg. clay) erodes quickly to make bays
      1. Swanage bay - Dorset
    2. Hard rocks (eg. limestone) erodes slowly to make headlands
      1. The Foreland - Dorset
  2. Caves, arches, stacks and stumps
    1. 1. A crack in the headland is expanded by hydraulic action
    2. 2. The crack becomes a cave
    3. 3. The cave is opened up to form an arch
      1. Durdle door - Dorset
    4. 4. The top of the arch collapses to form a stack
      1. Old Harry -Dorset
    5. 5. The stack is eroded to form a stump
      1. Old Harry's wife - Dorset
  3. Wave cut notches and platforms
    1. Waves undercut a cliff to leave an overhanging platform above a wave cut notch.
      1. The platform eventually collapses and the process happens again
Transportation
1. Transportation of different rocks
  1. Traction - big rocks roll along the sea bed
  2. Saltation - pebbles bounce along the sea bed
  3. Suspension - sediment is small enough to be carried along by the water
  4. Solution - tiny particles dissolve in the water and move with it
2. Longshore drift
  1. Direction depends on the prevailing wind
  2. Constructive waves have a strong swash
  3. Destructive waves have a strong backwash
  4. Sediment is moved along the shore by a diagonal swash and a straight backwash
  5. Swash - a wave moving inland
  6. Backwash - a wave moving back towards the sea
Beaches
1. Sand beaches
  1. Formed by constructive waves
  2. Can have sand dunes
  3. Shallow gradient, almost flat
2. Pebble beaches
  1. Formed by destructive waves
  2. Steep gradient, often has berms
  3. Large pebbles at the back of the beach
3. Depositional landforms
  1. Spit
    1. A finger of sand formed by longshore drift
    2. Hook
      1. A spit with a marsh behind it curves due to the low energy of the marsh to create a hook
    3. Bar
      1. A spit grows between headlands to create a bar
4. Sand dunes
  1. 1. Embryo dune
    1. Small dune closest to the water
    2. Plant found: Couch grass
  2. 2. Fore dune/yellow dune
    1. Plant found: Marram grass
  3. 3. Grey dune
    1. Plant found: Willow
  4. 4. Dune slack
    1. A big dip between high dunes where water can get trapped
    2. Plant found: Common sallow
  5. 5. Mature dune
    1. Big dune furthest from the water
    2. Plant found: Pine
Coastal management
1. Hard engineering - building defenses
  1. Sea wall
    1. Absorbs energy from waves and can redirect them (if curved at the top)
    2. Advantage: Strong and effective
    3. Disadvantage: Expensive - £6000 per meter
  2. Rip rap
    1. Absorbs energy from waves
    2. Advantage: Simple to maintain
    3. Disadvantage: Expensive - £1000 per meter, can look messy, can be dangerous
  3. Groynes
    1. Traps sediment from longshore drift and absorbs energy from waves
    2. Advantage: Helps to build up a natural defence
    3. Disadvantage: Expensive - £10000
2. Soft engineering - in line with the natural environment
  1. Cliff regrading
    1. Makes a cliff less steep
    2. Advantage: Cheap
    3. Disadvantage: Loss of some cliff
  2. Dune stabalisation
    1. Planting marram grass to hold dunes together
    2. Advantage: Cheap, sustainable, looks natural
    3. Disadvantage: Doesn't always work
3. Managed retreat
  1. Allowing an area to become flooded by removing costal protection
  2. Aims
    1. Improve costal stability
    2. Protect areas further inland
    3. Rely on natural defences
    4. Creates saltmarsh - a low energy environment
  3. Northen Island, Essex - River Blackwater flooded in 1991, 8000sq metres, nature reserve
  4. Advantages
    1. Earth banks develop
    2. Maintinence costs are low
    3. Saltmarsh and vegitation provide protection from storms
    4. Beaches can naturally replenish
  5. Disadvantages
    1. Land will be lost
    2. Settlements will be destroyed
    3. Not socially acceptable and compensasion will be needed for land owners
    4. Schemes are unpredictable
4. Case study
  1. Minehead
    1. A coastal town on the Bristol channel and the north-west coast of Somerset
    2. Coastal management strategies used
      1. A 0.6m high seawall with a curve to deflect waves
        Expensive but the walkway build beside it is popular with tourists
      2. Rock armour
        Expensive but low maintenance and asthentically pleasing
        Wildlife can benefit by creating new habitats in it
      3. More sand put on the beach (beach nourishment)
        Forces waves to break further out to sea
        Attracts tourists
      4. Four rock groynes
        Helps to stop sand movement from longshore drift
        Provides wind shelter for tourists
        Can increas erosion further down the coast

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	Created by Amy Taylor about 4 years ago