There are several factors that determine whether a stretch of coastline is protected from erosion or not. Hard engineering approaches like groynes, sea walls, gabions, revetments, and rock armor are expensive options to prevent erosion but may not be aesthetically pleasing. Softer engineering techniques like beach nourishment, stabilizing sand dunes, and managed retreat are generally less expensive and more sustainable as they work with natural coastal processes. The Holderness Coast in England is an example of an eroding coastline where various hard and soft engineering strategies have been used to protect vulnerable areas from erosion over the past few centuries.
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Coastal Management Holderness Ap
1. What determines whether a particular stretch of coastline is protected or not? Protected Unprotected Robin Hood’s Bay 1770-1994, 200 houses went over the cliffs Caravans/cheap housing that is sparsely distributed Whether land is protected or not comes down to the economic value of the land
4. Stop longshore drift What are they designed to do? Further down the coast this may mean that beaches are starved of sand and shingle 1) Groynes £10,000 each (wooden groynes) £1.5m each (rock groynes) A) Hard engineering Mappleton, Yorks. coast
7. Expensive at £5,000/m Designed to stop erosion, but what landforms would that prevent being created? Would you rather go on holiday and see Old Harry or a sea wall? 2) Sea Walls Energy is reflected (not absorbed). Over time the energy scours the base of the sea wall undermining it, causing it to collapse This is reduced by absorbing the energy and angling the wall
9. 3) Gabions Much cheaper than sea walls £1000/m, but do you think they are attractive? Small rocks, bound in place by cages absorb the wave energy and reduce erosion
20. 5) Rock armour or Rip Rap Relatively cheap £1,000/m, but considered environmentally ugly When resting on sand and shingle they may be moved out of position by waves
22. 6) Gabions and groynes together Why might you choose to implement more than one coastal management strategy at a time? To protect against erosion and longshore drift
23. B) “Soft” Engineering Less expensive than hard strategies Longer term, more attractive and sustainable as they work with natural processes How attractive do you consider these to be?
24. 1) Beach Nourishment The beach is widened; how will this affect the energy of the waves? Sand and/or pebbles are brought in to replace material that has eroded away. Where do you think this replacement material has come from? It has been dredged from the sea bed. In some cases it is pumped onto the shore. It will reduce the energy that the wave has meaning less erosion. Cost: £100/m/yr
25. 2) Stabilising Sand Dunes Grasses are planted in the sand dunes to bind them together, holding them in place. Footpaths may be designated. Why might this be? To reduce trampling of the dunes by people, which erodes them
26. 3) Managed Retreat When the land by the sea is of low economic value it may be allowed to erode. In some cases this eroded material forms beaches which naturally protect the coast.
28. Why protect/manage the coast?: Case Study Holderness Coast Over 30 villages have been lost since Roman times, erosion has been taking place for last 6000 yrs Holderness Coast is fastest eroding stretch of coastline in Europe – an average of 2 metres fall into the North Sea each year Locally, rates of erosion have been up to 10-20m with waves biting coast away
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31. Soft boulder clay High energy waves because of long fetch Thin, narrow beaches do little to absorb wave energy The beaches are thin because the material is carried away by longshore drift Why are the beaches thin and narrow? Chunks of coast slump down the cliff Holbeck Hall, Scarborough
32. Holderness Coast – Cliff Processes Material slumps down the cliff Rain water enters cracks Boulder Clay Cliff Beach Sea Cracks formed by wetting and drying Removal of slumped material by sea Slip plane developing
