Coastal Protection: Groynes


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Secondary 3 Full Geography (2235/1)

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Coastal Protection: Groynes

  1. 1. Coastal Measures<br />Groynes<br />
  2. 2. What are groynes?<br />They are a form of coastal protection.<br />They are built at right angles to shore to prevent longshore drift.<br />These structures absorb energy of the sea on the shore. Like headlands. Reducing the impact of energy on the coast.<br />There are 4 types of groynes which are wooden groynes, steel groynes, Rubble-mound and sand-filled bag groynes and groynes of concrete elements .<br />
  3. 3. Positive Impacts…<br />It traps sediments from longshore drift, forming a beach which attracts tourist. Creates a positive effect on the local economy.<br />Coastal erosion on beach is significantly reduced, as the water can only reach the cliff during high tide.<br />Low maintenance.<br />Lowest cost, little money is spent to build it.<br />
  4. 4. Negative Impacts…<br />They prevent beaches down the coast from having sediments deposited there, which can lead to soil erosion. This could also destroy buildings and private land, which will cause property prices to plummet.<br />Causes the coast to be ugly and unnatural.<br />They can lead to cliff collapse.<br />Does not protect coasts from storm-driven waves approaching the shore perpendicularly.<br />Protection of the shore by use of one groyne only is most often inefficient. Therefore, shore protection by groynes is designed as a group comprising from a few to tens of individual structures. <br />
  5. 5. Interesting facts!!!<br />It cost about 5000 sterling pounds to build a groyne in Britain.<br />In addition to being costly, there is also a problem called Terminal Groyne Syndrome. The last groyne that has been built prevents longshore drift from bringing material to other nearby places. This is a common problem along the Hampshire and Sussex coastline in the UK.<br />
  6. 6. More interesting facts!!!<br />Groynes can also be used for river management bymaintaining a channel to prevent ice jamming, and more generally improve navigation and control over lateral erosion, that would form from meanders.<br />They are sometimes used as bridges to prevent bridge scour in rivers.<br />If a groyne is too large it may trap too much sediment, which can cause severe beach erosion on the down-drift side.<br />
  7. 7. Pictures!!!<br />
  8. 8. Done by:<br />Hong Sung Woo(7)<br />Lee QiZong(15)<br />Theodore Lam(14)<br />Marcus Neale Goh(20)<br />
  9. 9. Thank You For Watching!<br />