Sea Wall (page8,Q2d)• The sea wall is a retaining wall built on and parallel to coast• It is made of concrete and rocks and can be sloping or vertical• It absorbs the energy of waves and reflects the waves from the coast to reduce the effects of strong waves. This will cut down erosion
Problems with Sea Walls• But it has a problem.• It does not reduce the energy of waves. It only reflects it to the area beneath and in front of the wall. This will cause the beach material at this area to be eroded and removed• The bottom of the wall is undercut, and will weaken and collapse. The wall will need to be repaired and replaced.
What’s the differencebetween theseawall andbreakwater
BUILDING BREAKWATER & ITS EFFECTSConcrete / rock structure built parallel to coast some distance away
BUILDING BREAKWATER & ITS EFFECTSConcrete / rock structure built with one end attached to the coast
Breakwaters • Break the force of the waves some distance from the coast • Reduce erosion along the coast • Calm waters behind the breakwater caused deposition and formation of beach • Erosion in areas not protected by the breakwater
Breakwaters• Breakwaters are made of rocks and concrete• The most common type of breakwater is built parallel to and some distance from the coast• Breakwaters break the force of waves some distance away from the coast. When waves hit the breakwaters, they will lose their energy and there will be less erosion.• The strength of the waves behind the breakwater is reduced so deposition takes place and a beach is formed behind the breakwaters.
Problems with Breakwaters• The problem with breakwaters is erosion will take place on the part of the coast that is not protected by the breakwater.• (CONCLUSION – Need to give conclusion because this is level marking question) Therefore I conclude that all the methods help to reduce erosion. However, they are not totally effective because all of them have some problems.
Groynes• Built at right angles to the sea – trap sediments on the side facing the longshore drift – stops the removal of sediments by longshore drift – build up a beach• Protects existing beaches behind the groyne from erosion• Protects cliff behind groyne from wave erosion
Problem with Groynes• Beach on the other side may disappear because there is no new addition of sediments. Also existing sediments removed by erosion• The solution is to build more groynes along the coast – but this makes it very unattractive
Gabions• Gabions are wire cages filled with crushed rocks and piled along the shore• They help to weaken wave energy and will reduce or prevent erosion
Problems with Gabions• The problems is they do not last very long because they get rusty very fast. Also, they are easily damaged because people keep stepping on it.• They have to be maintained regularly as the wires can be a danger for people walking along the beach.• Furthermore, they look quite ugly
Soft Engineering Approach• Does not involve building physical structures – no need for regular maintenance – so easier and cheaper to carry out• Also called non-structural approach• Involves proper planning, management and use of the coast
Hard vs Soft Engineering MethodsHard Engineering Methods Soft Engineering Methods• Some physical structure has to • Does not involve building any be built. Requires money, physical structure. Only manpower and technology. (eg involves the proper planning, seawall, groyne, gabion and management and use of the breakwater) coast as well as encouraging• The physical structure does not minimal human interference last very long and needs to be along the coast. So saves a regularly maintained (eg the wire lot of money. (eg stabilising cages or gabions will rust and dunes) must be changes regularly) • As it involves educating people• Protects only one part of the on how to use the coast, it is coast, but it creates new more long term problems elsewhere along the • It is environmentally friendly coast (eg breakwaters only and beautifies the environment protect the coast behind it) (eg mangrove trees are• May cause harm to humans (eg protected so that their roots gabion are steel cages that have will trap the sand) sharp edges…)
• Level Marking• Eg Do you agree that gabions are the only measures used to protect the coast from erosion? Explain gabions 3 others – hard and/or soft methods
• Assess the effectiveness of hard engineering methods to protect the coast. (8 – Level Marking)Intro- Hard engineering methods are effective only to a certain extent because it has advantages as well as problems.Para 1- Eg Describe what seawalls are, how it helps and its problems. Do the same for 3 other methodsConclusion- Therefore all the methods have advantages and problems and are not totally effective.
Video on Coastal Erosion• http://www.youtube.com/watch?v=zUh3WeilFN4• Pay attention to what the video says about Coastal Erosion.
What factors are identified in the video?[Deposition](1) Strength of waves[4 Processes of Coastal Erosion]Factors:1. Geology – type of rock present
Video on Coastal Management• http://www.youtube.com/watch? v=HiNGGwRfdMU