coastal landscapes

natural/ physical elements
1. WAVES
  1. formed due to the transfer of energy and the direction of the prevailing wind
    1. DEPENDS ON: the distance the wind has blown, the speed its travelling, and how long its been travelling.
      1. destructive waves
        occur in stormy conditions, high wave height in proportion to length, high frequency, high energy, large fetch, responsible for erosion, greater backwash than swash, steep beach
      2. constructive waves
        occur in calm conditions, low wave height in proportion to length, low frequency, low energy, transport material via long shore drift, responsible for deposition, greater swash than back wash
        LONG SHORE DRIFT
        beach sediment is transported along the coast by waves .
2. LANDFORMS
  1. BEACHES
    1. DEPOSITIONAL LANDFORM, formed by CONSTRUCTIVE WAVES, consist of SAND OR SHINGLE, made up of VARYINGLY SIZED SEDIMENT DUE TO LOCAL GEOLOGY AND WAVE ENERGY
  2. BAYS & HEADLANDS
    1. EROSIONAL LANDFORM: bays and headlands develop on discordant coastlines, eg. a mixture of hard and soft rock. commonly found where cliffs have fault lines/ distinctive joints.
      1. the soft rock eg. gravel, sand and clay erode quickly, forming bays, eg. lulworth cove, devon.
        the hard (resistant) rocks eg. limestone and chalk take much longer to erode and are left jutting out into the sea, as headlands-, eg. lands end, cornwall
  3. WAVE CUT PLATFORMS
    1. EROSIONAL LANDFORM: the erosion of cliffs by undercut waves at their base creates a wave cut notch- this leaves an overhang.
      1. the overhanging rock collapses and the cliff retreats inland, resulting in a wace cut platform
  4. CAVES, ARCHES, STACKS & STUMPS
    1. EROSIONAL LANDFORM: CAVES. formed by hydraulic action widening cracks in the cliff face , generally found on headlands formed from harder resistant rock.
      1. ARCHES: a cave that is eroded all the way through the cliff face, eg. durdle door.
        STACKS: the apex of the arch collapses as it is weakened by weathering, leaving a singular pillar out to sea, eg. canna stack
        STUMPS: the stack collapses due to erosion and weathering, resulting in a collapsed stack, or a stump . (eg. old harry, dorset.)
  5. SPITS, BARS & TOMBOLOS
    1. DEPOSITIONAL LANDFORMS: SPITS. created by longshore drift, a stretch of beach material is carried out to sea from the mainland, eg. spurn point, yorkshire. the spit can change shape dependent on wind direction.
      1. BARS: in the same way as a spit, a stretch of beach sediment reaches across a bay, connecting two headlands eg. Loe bar. a lagoon forms behind the bar, which eventually becomes a salt marsh.
        TOMBOLO: a bar or spit that reaches an island, eg. st ninians
3. COASTAL PROCESSES
  1. EROSION- wears away rock and removes eroded material
    1. abrasion
      1. pebbles picked up by waves are flung at cliffs , wearing the cliffs away
    2. attrition
      1. pebbles carried by waves collide with other particles and become round and smooth
    3. corrosion
      1. rocks and minerals are dissolved by water
    4. hydraulic action
      1. waves hitting the cliffs force air into cracks- the pressure created breaks up the rocks.
  2. WEATHERING- wears away rocks but leaves weathered material in situ
    1. biological
      1. tree roots and burrowing animals break soil structure
    2. physical
      1. eg. freeze thaw (water damage), onion skin (expanding and contracting due to temperature)
    3. chemical
      1. eg. acid rain, attacking alkali limestone
  3. MASS MOVEMENT
    1. rock falls
      1. FRAGMENTS OF ROCK created by WEATHERING FALL to the CLIFF BASE
    2. slumping
      1. the CLIFF BASE is ERODED BY THE SEA and the TOP IS SATURATED BY RAIN- the cliff starts to slide.
    3. soil creep
      1. SLOW MOVEMENT of SATURATED SOIL creeping down a slope, resulting in TERRACETTES
4. COASTAL RECESSION
  1. CLIFF EROSION CAUSES CLIFFS TO RECEDE, AND THEREFORE THE COASTLINE
    1. IMPACTS
      1. NATURAL:
        LOSS OF HABITAT (durlston bay, dorset, home to 250 species of birds)
      2. HUMAN:
        LOSS OF PROPERTY (durlston bay, dorset, Happisburg, norfolk) LOSS OF BUSINESSES (holbeck hotel, yorkshire, 1993.)
        issues caused: DIFFICULT TO GET INSURANCE, LOWERS PROPERTY PRICES, LIMITED GOVERNMENT SUPPORT FOR HOME OWNERS
    2. CAUSES
      1. FETCH- a larger open body of water eg. the atlantic means a larger fetch, s o bigger more destructive waves cause more erosion
        GEOLOGY- harder more resistant rock eg. in the north west of the UK erodes slowly compared to soft rocks aka clay and sand in th south east of the uk.
        COASTAL MANAGEMENT- coastal defences can slow down the rate of erosion and protect the coastline.
5. COASTAL FLOODING
  1. CAUSES
    1. causes are: HIGH TIDE LEVELS, STORM SURGES the ACTION OF WAVES (influenced by wind speed) and RISING SEA LEVELS (caused by global warming and thermal expansion)
  2. PREVENTION
    1. BARRIERS to protect against high tides, aka the thames barrier, FLOOD PLAINS- areas of open space to allow floodwater to spill over. FLOOD WALLS built long rivers, eg. the thames
  3. PLANNING
    1. PREDICTION: the EA monitors sea conditions to help predict potential flooding, EARLY WARNING SYSTEMS are put in place, FLOOD EDUCATION eg. what to do in the event of a flood , ESCAPE ROUTES, ADVICE from services such as the EA nand the health protection agency.
  4. areas at risk are LOWLYING, aka the NETHERLANDS, the MALDIVES, BANGLADESH, NORFOLK
manmade elements
1. COASTAL ENGINEERING
  1. HARD
    1. traditional approach, involves building structures
      1. CURVED SEA WALLS
        PROS: protects cliffs and buildings, reassures home owners, can prevent coastal flooding
        CONS: ugly, can cause erosion of beach in front, wall may erode, maintenance is constant and expensive. costs £5000- £100000 to build per linear metre
        eg. blackpool, porthleven
      2. GROYNES
        PROS: prevents long shore drift, builds up beach (acts as natural defense against erosion, attracts tourists), cheapish to build at £2000 per m
        CONS: can cause erosion further along the coast, ugly, needs replacing regularly
        eg. eastbourne
      3. RIP RAP
        PROS: absorbs wave energy, helps build up the beach, relatively cheap (£1000- £3000 per m)
        CONS: not as effective as other methods, transport can be difficult
        eg. dawlish warren
      4. OFFSHORE REEF
        PROS: prevents erosion of beach, disperses wave power
        CONS: expensive (£5000 per m), interferes with fishing,
        eg. bournemouth, happisburgh
  2. SOFT
    1. better for nature, focuses on tourism and the environment
      1. CLIFF REGRADING
        PROS: reduces slippage, looks natural, doesn't discourage tourists
        CONS: doesnt protect base of cliff
        eg. swanage bay
      2. BEACH REPLENISHMENT
        PROS: beaches reduce wave energy and cliff erosion, attracts tourists, cheapish (£2000 per m)
        CONS: lorries are noisy and pollutive, disturb residents
        eg. carlyon bay
      3. MANAGED RETREAT
        PROS: moving people avoids erosion, creates new wetland habitats, needs no maintenance and offers an actual solution
        CONS: compensation can be expensive, farming and residential land can be lost
        eg. san mateo, california
case studies
1. the cornish coast
  1. the cornish coastline is manly granite, a hard resistant rock, however it is eroded by a long fetch and high energy destructive waves .
    1. HARD ENGINEERING USED
      1. GABIONS, PORT GWIDDEN- wire meshed baskets filled with rocks that absorb wave energy
      2. SEA WALLS, MOUSEHOLE & MARAZION- protect harbours important for recreation and industry
      3. RIP RAP REVETMENTS, WIDEMOUTH BAY- absorb energy, reduce erosion and landslides
    2. SOFT ENGINEERING USED
      1. DUNE STABILISATION, LONG ROCK- sand dunes absorb wave energy and educe coastal erosion- stabiliation prevents them from receeding
      2. BEACH REPLENISHMENT, CARLYON BAY- prevents the loss of coastal footpaths, a natural defense against erosion
2. happisburgh
  1. SMALL TOWN, on NORFOLKS NORTH COAST
    1. THE ISSUE: one of the fastest eroding places globally, at 9m per year
      1. WHY: the village is built on soft rock which erodes quickly. the cliffs are only 6-10m high and are made of laminated clay. the north sea has a large fetch, resulting in large destructive waves .
        IMPACTS: house prices have dropped from £80 000 to £1, residents will be made homeless, over 20 square miles of farming land would be lost.
        PREVENTION: wooden revetments, no longer maintained as too expensive. off shore reef, only partially effective. the government is recommending managed retreatt as happisburgh not worth saving- CCAG and local residents disagree

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	Created by meg watts about 8 years ago

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