L1 coastal management strategies.1pptx


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L1 coastal management strategies.1pptx

  1. 1. Coastal Management
  2. 2. Complete your A3 sheet as we go
  3. 3. Key Terms relating to coastal management • Advance the Line: – A strategy to move the defence of an area seaward of its position, e.g. land reclamation. • Hold the line: – A strategy to hold the current line of the coast. E.g. Beesands in Devon. • Do Nothing: – Carry out no coastal defence activity except for safety measures. E.g. moving static caravans away from cliff edge at …………., …… • Retreat the line: – A strategy to encourage the movement of the shoreline landward of its present position in a managed or controlled manner, hence the term ‘managed retreat’. E.g …………………….
  4. 4. • Soft Engineering Makes use of natural systems, such as beaches or salt marshes, to help with coastal defences,. The advantage of soft systems is that they can absorb and adjust to wave and tidal energy and have a more natural appearance. • Hard Engineering Involves building a physical structure, usually from rocks or concrete, to protect the coast from the forces of natural. It is used to reduce erosion and the risk of flooding. Definitions
  5. 5. A. Soft engineering
  6. 6. A. Soft Engineering 1. Beach Nourishment • Sand and/or pebbles are brought in to replace material that has eroded away. • Natural looking • Expensive and never ending!
  7. 7. 1) Beach Nourishment
  8. 8. 2. Beach Re-profiling • Shape of beach changed to reduce the effects of erosion. • Cheap and simple • Only works in low energy environment.
  9. 9. 3. Dune regeneration • Wooden structures erected to encourage sand deposition and vegetation planted. • Effective if managed properly. • Only succeeds if public access is limited.
  10. 10. 4. Offshore reefs • Mining waste, old tyres and even old cars are sunk and act like speed bumps in the sea. • Cost effective and semi- natural. • Largely untested and may have pollution impacts.
  11. 11. B. Hard engineering Don’t write any of these down
  12. 12. B. Hard Engineering 1. Groynes • Groynes are designed to slow down longshore drift • The Build up of sand reduces the wave energy and thus protects the beach • They are usually made of tropical hardwoods which are more resistant to erosion. • A few are made of concrete, steel or in more recent times large rocks. • They are built at right angles to the shore and spaced about 50-100 metres apart. Groynes may have a life of 15-20 years
  13. 13. Terminal Groyne Effect • Occurs when there are piecemeal protection schemes. • For instance a groyne field is built and sediment builds up between the groynes • The coastline continues to erode. • On the downdrift side there is a sediment deficit. The erosion of non protected side continues
  14. 14. Terminal Groyne Effect In Action
  15. 15. Sea Walls • Energy is reflected (not absorbed). Over time the energy scours the base of the sea wall undermining it, causing it to collapse
  16. 16. Recurved sea wall
  17. 17. Gabions • Small rocks, bound in place by cages absorb the wave energy and reduce erosion • Cheap
  18. 18. 4) Revetments • Open structure of planks absorb wave energy, but allow sand and shingle to build up beyond
  19. 19. 5) Rock Armour / Rip Rap • Large resistant rocks placed at base of cliff to stop erosion. • Help to absorb and dissipate wave energy. • When resting on sand and shingle they may be moved out of position by waves.
  20. 20. Your turn! • Now using p 241 in the text book complete the hard engineering section of your A3 sheet.