Coasts at a glance
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Coasts at a glance

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Coasts at a glance Coasts at a glance Presentation Transcript

  • Things you should know off by heart! When I saw off by heart I mean anything that’s written in this PowerPoint you should be able to write in your exam!!
  • Constructive and Destructive Waves• At least two differences between constructive and destructive waves e.g. – Constructive waves are long, low waves that build up the beach. – Destructive waves are much more frequent waves with a shorter wave length and erode the beach.
  • Erosion• Hydraulic action – air gets forced into cracks and then pops like air from a champagne bottle• Abrasion – rocks hit the cliff• Attrition – rocks hit other rocks wearing each other away• Corrosion – sea water dissolves the rock
  • Mass Movement • Bottom of the cliff eroded by waves and undercut • Rainfall saturates cliff and makes it heavier •Rocks slide down cliff •Often happens in clay • Rocks are weathered on the cliff face • They break loose and fall under the influence of gravity
  • Wave Cut Platforms• Hydraulic action erodes the coastline causing undercutting.• Rocks above the notch are unsupported and collapse.• The rocks from the cliff are eroded by abrasion and attrition causing a wave cut platform.• The cliff retreats inland
  • Rate of cliff recession• The longer the fetch, the further the wave has to travel. It picks up more energy and so erodes the cliff quicker• The softer the geology (rock) the easier it is to erode so cliff recession happens more quickly
  • Cave, arch, stack, stump
  • Longshore Drift • The direction of the wind forces waves onto the beach at an angle • Swash carries sediment (sand and rocks) up the cliff • Backwash pulls material off the beach under gravity. • Sediment is transported along the coast
  • Formation of a spit• Longshore drift carries material along the coastline• When the coastline changes direction, longshore drift continues and extends the beach into open water• The end of the spit often becomes curved because of changes in the wind direction• Sediment often builds up in the sheltered water behind the spit to form a salt marsh
  • Effects of coastal recessionHuman• Loss of land• Loss of property and belongings• Insurance has to pay out a lot of moneyEnvironmental• Loss of habitat for animals• Loss of breeding grounds for birds
  • Coastal Flooding and Protection Thames Barrier build to protect the city of People in Bangladesh plan for flooding by London. Barriers closed during bad building their houses on stilts. This weather and high tide to protect peoples protects their houses and belongings. businesses and property.Met office predicts heavy rain. People can ring Floodline to see if their property is at risk. Can then protect property with sand bags, evacuating or moving belongings upstairs.
  • Hard Engineering• Groynes – stop longshore drift• Revetments – protect the cliff and capture sediment• Seawall – protects the cliff• Riprap – absorbs wave energy and protects the cliff• Offshore reefs – absorb wave energy to allow a wide beach to develop.
  • Soft Engineering• Beach replenishment – taking sand from the bottom of the ocean and putting it back on the beach• Managed retreat – coastal erosion is allowed to happen• Cliff regrading – making the cliff face longer and less steep to stop slumping.
  • Coastal Protection - You should know at least 2advantages and 2 disadvantages for hard and soft Hard Engineering Soft Engineering Advantages Advantages (1) protects the land and (1) Looks completely natural buildings behind the cliff. (2) Managed retreat and cliff (2) absorb wave energy and regrading are much stop material from the cheaper beach being eroded. Disadvantages Disadvantages (1) Erosion will continue to (1) Very expensive to build happen and maintain (2) They have be to replaced (2) They often look ugly much more often
  • SwanageSwanage is build on clay which is susceptible to erosion. To protect Swanage:• A seawall was built as a barrier to wave attack• The cliff was regraded to prevent slumping• A series of groynes were installed to reduce longshore drift.• 90000m3 of sand was pumped onto the beach.