coastal landscapes

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  • Created by: Devika_C
  • Created on: 05-01-20 15:53
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  • coastal landscapes
    • waves
      • waves FORM when wind is blown over the sea : the friction causes ripples which turn into waves
      • WHEN THE WAVE REACHES THE COAST : the water is in a circular orbit which is broken down due to the friction with the seabed.
        • crest of wave moves faster and water becomes shallower and the wave moves forward
          • the wave breaks and collapses on the beach
            • water which rushes UP the beach : SWASH
            • water which returns: BACKWASH
      • two types
        • constructive
          • FORMED : by storms far away COMMON : in the summer
            • waves are far apart
              • low waves + gently sloping wave front
                • strong swash + weak backwash
        • destructive
          • FORMED : by local storms close to the coast COMMON : in the winter
            • waves are close together
              • high waves + steep wave front
                • weak swash + strong backwash
      • FETCH : the distance the wave-generating  winds blow across the water
        • the longer the fetch the bigger the wave
    • weathering
      • Weathering: the weakening or decay of rock due to the weather
      • three types
        • mechanical
          • freeze-thaw : water collects in cracks - water freezes and expands = larger cracks - temp rises = ice thaws and water seeps deeper - repeated process = fragments break off
        • chemical
          • carbonation : rainwater absorbs CO2 and becomes slightly acidic - contact with alkaline rocks = dissolves due to a chemical reaction
        • biological
          • plant roots grow in cracks in rocks and animals burrow into weaker rocks
    • mass movement
      • the downward movement of weathered material
      • 4 examples
        • ROCKFALL : rock breaks away due to freeze-thaw
        • LANDSLIDE : blocks of rock slide downhill
        • MUDFLOW : saturated soil and weak rock flows downhill
        • ROTATIONAL SLIP : slump of saturated soil and weak rock along a curved surface
    • erosion processes
      • SOLUTION : dissolving of soluble chemicals in rock
      • CORASSION: rock pieces are picked up by the sea and thrown at the cliff where it scrapes away rock
      • ABRASION : sandpaper effect - making a rocky platform smooth
      • ATTRITION: rock fragments knock into each other in the sea making them smaller
      • HYDRAULIC POWER : power of waves onto a cliff moves trapped air into cracks which causes the rock to break
    • coastal transport
      • SOLUTION: dissolved chemicals
      • SUSPENSION : particles carried within the water
      • TRACTION: large pebbles rolled along the seabed
      • SALTATION: bouncing motion of particles too heavy to be suspended
      • LONGSHORE DRIFT: moves sediment along the beach in a zig-zag pattern
    • landforms
      • deposition landforms
        • BEACHES: are deposits of sand and shingle
        • SAND DUNES: at the back of the beach, sand blown inland can build up to form dunes
        • SPITS & BARS: - spit = long finger of sand jutting out into sea - bars =  form when long-shore drift causes spits to grow across a bay
          • barrier beaches = when offshore bars have been driven on shore by rising sea levels [ eg: Chesil Beach in Dorset]
      • erosion landforms
        • - influenced by rock type and geological structure - different rocks erode at different rates
        • HEADLANDS & BAYS : more resistant rock is eroded slowly to form headlands + weaker rock erodes easily to form bays
        • CAVES, ARCHES & STACKS: - crack - abrasion and hydraulic action = cave - erosion = arch - roof collapses = stack - more erosion = stump
        • CLIFFS & WAVE CUT PLATFORMS: erosion against the cliff will eventually form a wave-cut notch - this repeats until the overlaying cliff collapses - this happens again and again, leaving a wave-cut platform
      • SWANAGE, DORSET [south coast of england]
        • important factors of the formation = rock types and geological structure
        • discordant coastline = alternating bands of harder and softer rock = headlands and bays
          • (concordant coastline = one band of rock which is parallel to the coast) { not swanage }
        • examples
          • HEADLANDS: The Foreland, Ballard Point, Peveril Point & Durlston Head
          • BAYS: Studland Bay, Swanage Bay & Durlston Bay
          • BEACHES: in Studland Bay & Swanage Bay
          • STACK: Old Harry
    • management
      • HARD engineering
        • SEA WALL - concrete or rock barrier at the top of beaches to reflect waves out to sea
          • [+] -effective -creates a walkway
          • [-] - looks unnatural - very expensive + high maintenance costs
        • GROYNES - rock structures built at right angles to the beach which traps sediment from moving from longshore drift
          • [+] - creates a wider beach which is good for tourism - not expensive
          • [-] - unnatural and unattractive - erosion elsewhere
        • GABIONS - rock-filled cages that support a cliff and provide a buffer against the sea
          • [+] - cheap - improve cliff drainage
          • [-] - unattractive - cages rust
        • ROCK ARMOUR - piles of large boulders at foot of cliff (rocks absorb wave energy)
          • [+]  - cheap -adds interest - easy to maintain
          • [-] - expensive to transport rock - obtrusive - not local geology
      • SOFT engineering
        • BEACH NOURISHMENT - sand or shingle is dredged offshore and transported to the coast by barge
          • [+] - cheap - blends in with landscape - bigger beach means more tourism
          • [-] - needs constant maintenance
        • DUNE REGENERATION - grass is planted to stabilise dunes and help them develop
          • [+] - natural environment which is good for wildlife - cheap
          • [-] - time-consuming - can be damaged by storms
        • DUNE FENCING - fences are used to encourage new dune formation and keeps people off newly planted areas
          • [+] - using this method helps other ecosystems - little impacts on natural systems
          • [-] - unsightly -regular maintenance
      • managed retreat
        • allows the sea to flood or erode an area of relatively low-value
        • people living in these areas must adapt by moving further inland & scientists monitor thee stretches of coast
        • MEDMERRY MANAGED RETREAT
          • flat low-lying land in southern England
          • land is low value so the sea wall was allowed to breach in 2013
          • costs : £28 million to - create a large natural saltmarsh - help to protect surrounding lands - wildlife habitats and encourages visitors to the area
          • embankments have been built inland to protect farmland, roads and settlements
      • LYME REGIS : small coastal town in Dorset on England's south coast
        • issues: unstable cliffs + powerful waves cause rapid erosion + sea walls breached many times
        • the lyme regis environmental improvement scheme was set up in the early 1900s to provide long-term coastal protection and reduce the threat of landslips. completed in 2015
        • features of the scheme: - new sea walls -cliff stabilised  - extension of rock armour -creation of beaches COSTS: £43 million
        • [+} - new beaches = increased visitors - defences withstood winters - harbour is better protected
        • [-]  - more visitors = conflict due to traffic congestion and litter - defences spoil the landscape - sea wall interferes with natural processes

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