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Coastal Defence

Coastal Defence. These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates that the slide contains activities created in Flash. These activities are not editable.

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Coastal Defence

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  1. Coastal Defence These icons indicate that teacher’s notes or useful web addresses are available in the Notes Page. This icon indicates that the slide contains activities created in Flash. These activities are not editable. For more detailed instructions, see the Getting Started presentation. 1 of 24 © Boardworks Ltd 2005

  2. Learning objectives • Why does cliff recession occur? • What are the effects of cliff recession? • How can the coastline be protected? • What are the disadvantages of coastal protection? • What is the best method of coastal protection?

  3. Why does cliff recession occur?

  4. Why does cliff recession occur? What are the two main causes of this cliff collapsing?

  5. Learning objectives • Why does cliff recession occur? • What are the effects of cliff recession? • How can the coastline be protected? • What are the disadvantages of coastal protection? • What is the best method of coastal protection?

  6. What are the effects of cliff recession?

  7. Learning objectives • Why does cliff recession occur? • What are the effects of cliff recession? • How can the coastline be protected? • What are the disadvantages of coastal protection? • What is the best method of coastal protection?

  8. How can the coastline be protected?

  9. How do groynes work? Groynes trap the sand which is carried along the coast by longshore drift. The sand acts as a natural protection against the force of the waves. The waves break onto the beach and not the cliffs.

  10. Managed Retreat Managed retreat is also known as managed realignment. It involves breaching an existing coastal defence, such as a sea wall, and allowing the land behind to be flooded. This land is then left to be colonised by saltmarsh vegetation. When established, the vegetation disperses wave energy, reduces erosion rates and provides new habitats. The first attempt at managed retreat in the UK was on Northey Island, located in the Blackwater Estuary in Essex.

  11. How can the coastline be protected? Hard engineering techniques aim to stop coastal processes from occurring. Soft engineering methods try to work with nature to protect the coast.

  12. Swanage Bay Study the photo and map extract. Is this Peveril or Ballard Point? pier

  13. What has been done to protect Swanage?

  14. What has been done to protect Swanage? What is the purpose of each scheme at Swanage? Match the correct scheme to its purpose!

  15. Learning objectives • Why does cliff recession occur? • What are the effects of cliff recession? • How can the coastline be protected? • What are the disadvantages of coastal protection? • What is the best method of coastal protection?

  16. What problems do sea walls create? Why might a sea wall cause more coastal erosion?

  17. In 1991 a rock revetment and two rock groynes were built. Sand accumulated and halted erosion. • South of Mappleton, the rate of erosion has increased significantly. • Material that usually moves south via longshore drift is becoming trapped within the groynes. • Now there is no beach to protect the cliffs - the sea reaches the base of the soft cliffs and erosion occurs. What are the disadvantages of groynes? Mappleton is located on the Holderness Coastline.

  18. Learning objectives • Why does cliff recession occur? • What are the effects of cliff recession? • How can the coastline be protected? • What are the disadvantages of coastal protection? • What is the best method of coastal protection?

  19. What is the best method of coastal protection? This is the imaginary coastal town of ‘Seaview’. Seaview has been suffering from coastal erosion for the last 15 years since the nearby larger town of ‘Engleton’ had groynes built to protect its own coastline.

  20. What is the best method of coastal protection? There are strong feelings about what should be done to protect Seaview!

  21. What is the best method of coastal protection? Give each scheme a score from 1 (poor) to 5 (good). For example, an expensive scheme should have a low score. Would you choose the scheme with the highest score? Why? Which is the most important criteria?

  22. Examination question • Choose two of the sea defences and explain how they are used to protect cliffs from collapse. • List three disadvantages of hard engineering solutions. • Suggest one reason why some coastlines are not protected from the sea.

  23. What do you know about coastal defences?

  24. Key Ideas Cliff recession is caused by wave action and sub-aerial processes. Cliff recession can have major economic and social effects. Hardengineering solutions include sea walls, groynes, revetments, rip rap and gabions. Soft engineering solutions include cliff drainage, beach nourishment and managed retreat. All sea defence schemes have advantages and disadvantages.

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