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
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
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
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
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?
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
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
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.
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
Holderness Coastline Video - Answers <ul><li>Chalk deposits </li></ul><ul><li>Wave cut notch erosion </li></ul><ul><li>Boulder clay- left by the ice sheet </li></ul><ul><li>The boulder clay is easily eroded as it is a soft rock </li></ul><ul><li>Longshore drift </li></ul><ul><li>Groynes </li></ul><ul><li>RipRap, they stop the waves eroding the coastline by allowing the wave to break on them and spread out the energy </li></ul>
Holderness Coastline Video cont’d <ul><li>As there is no erosion, down the coastline there will be no deposits and so more erosion occurs </li></ul><ul><li>16m has eroded in 35 years </li></ul><ul><li>Sea wall and rip rap. Sue Earl does not live in a settlement, her farm was deemed as not worth protecting. </li></ul><ul><li>Spit- longshore drift deposition formed it. Groynes were built to maintain it. </li></ul><ul><li>Shifting mudbanks </li></ul><ul><li>Too expensive, and there are no important settlements. </li></ul>
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
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