Coastal Management 4


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Coastal Management 4

  1. 1. Coastal Management
  2. 2. <ul><li>Large scale development of coastal areas will bring about problems if development is not properly planned and managed. </li></ul><ul><li>Proper coastal management and protection are needed to preserve quality of coastal environment. </li></ul>
  3. 3. Lost Villages Due to Coastal Erosion
  4. 4. Types of Approach <ul><li>Hard engineering </li></ul><ul><li>Refers to the construction of physical structures to defend against the erosive power of waves. </li></ul><ul><li>- Also known as the structural approach . </li></ul>
  5. 5. Types of Approach <ul><li>Soft Engineering </li></ul><ul><li>- Focuses on planning and management so that both coastal areas and properties will not be damaged by erosion. </li></ul><ul><li>- Also aims to change individual behaviour or attitude towards coastal protection by encouraging minimal human interference and allowing nature to take its course. </li></ul><ul><li>- Also known as the non-structural approach. </li></ul>
  6. 6. Hard Engineering Measures <ul><li>Seawalls (+) </li></ul><ul><li>Seawalls absorb the energy of waves before they can erode away loose materials. </li></ul><ul><li>Seawalls can be made of concrete, rocks or wood. </li></ul><ul><li>They are effective in protecting cliffs from erosion. </li></ul>
  7. 8. Hard Engineering Measures <ul><li>Seawalls (-) </li></ul><ul><li>- They can only absorb the energy of oncoming waves. They do not prevent the powerful backwash of refracted waves from washing away the beach materials beneath the walls. </li></ul>
  8. 9. Hard Engineering Measures <ul><li>Seawalls (-) </li></ul><ul><li>- Base of seawalls will be undermined (weakened) and leads to their collapse. </li></ul><ul><li>- Seawalls are costly to build and maintain as constant repairs have to be made to prevent their collapse. </li></ul>
  9. 11. Hard Engineering Measures <ul><li>Breakwaters </li></ul><ul><li>Protect coast and harbour by reducing force of high energy waves before they reach the shore. </li></ul><ul><li>They can either be built with one end attached to the coast or built away from coast. </li></ul>
  10. 13. Hard Engineering Measures <ul><li>Breakwaters (+) </li></ul><ul><li>Breakwaters </li></ul><ul><li>Protect coast and harbour by reducing force of high energy waves before they reach the shore. </li></ul><ul><li>They can either be built with one end attached to the coast or built away from coast. </li></ul>
  11. 15. Hard Engineering Measures <ul><li>Breakwaters (-) </li></ul><ul><li>Materials deposited in the zones behind the breakwater are protected while those in the zones located away from the breakwater are not. </li></ul><ul><li>Zones will not receive any new supply and thus be eroded away . </li></ul>
  13. 17. Hard Engineering Measures <ul><li>Groynes </li></ul><ul><li>Built at right angles to the shore to prevent longshore drift . </li></ul><ul><li>These structures absorb or reduce the energy of the waves and cause materials to be deposited on the side of the groyne facing the longshore drift. </li></ul>
  14. 19. Hard Engineering Measures <ul><li>Groynes (-) </li></ul><ul><li>Erosion can still take place on the part of the coast that is not protected by groynes. </li></ul>
  15. 22. Hard Engineering Measures <ul><li>Gabions </li></ul><ul><li>- Gabions are wire cages usually filled with crushed rocks , and then piled up along the shore to prevent or reduce coastal erosion by weakening wave energy. </li></ul>
  16. 24. Hard Engineering Measures <ul><li>Gabions (-) </li></ul><ul><li>This method offers only short-term protection (about five to ten years). </li></ul><ul><li>Wire cages need regular maintenance as they are easily corroded by sea water. </li></ul><ul><li>Affected by excessive trampling and vandalism. </li></ul>
  17. 25. Hard Engineering Measures <ul><li>Gabions (-) </li></ul><ul><li>- Can be unsightly and become a danger along the beach. </li></ul>
  18. 26. Soft Engineering Measures <ul><li>Beach nourishment </li></ul><ul><li>Refers to constant replenishment of large quantities of sand to the beach system. </li></ul><ul><li>Beach is therefore extended seawards, leading to improvement of both beach quality and storm protection. </li></ul>
  19. 28. Soft Engineering Measures <ul><li>Beach nourishment (-) </li></ul><ul><li>Very expensive and impractical to constantly transport large quantities of sand to fill up beach. </li></ul><ul><li>Imported sand that can be continuously eroded and transported away could have serious consequences on wildlife living within coastal environment . </li></ul>
  20. 29. Soft Engineering Measures <ul><li>Beach nourishment (-) </li></ul><ul><li>E.g. Coral reefs at Waikiki Beach of Hawaii are destroyed as imported sand gets washed out to sea and covers the corals. </li></ul><ul><li>Corals are deprived of sunlight they need to survive </li></ul>
  21. 30. Soft Engineering Measures <ul><li>Beach nourishment (-) </li></ul><ul><li>E.g. Singapore – Large scale land reclamation along coast has led to muddy and polluted water and has destroyed coral reefs. </li></ul>
  22. 31. Soft Engineering Measures <ul><li>Relocation of Property </li></ul><ul><li>Coastal planners protect man-made structures (e.g. buildings) by relocating them and letting nature reclaim the beach in its own time. </li></ul><ul><li>No building of new properties of structures would be allowed in coastal areas that are vulnerable to coastal erosion. </li></ul>
  23. 32. Soft Engineering Measures <ul><li>Relocation of Property </li></ul><ul><li>- E.g. England – “Green Line” policy which discourages any building beyond a given line. Any properties built beyond the given line will not be defended or protected should they be threatened by coastal erosion. </li></ul>
  24. 33. Soft Engineering Measures <ul><li>Relocation of Property (-) </li></ul><ul><li>Opposition by people with considerable investments in coastal areas . </li></ul><ul><li>This approach will be important in future coastal management due to rising sea level as a result of global warming. </li></ul>
  25. 34. Soft Engineering Measures <ul><li>Planting of Mangroves </li></ul><ul><li>Mangroves have long and curved roots that prop up from soil. It traps sediments and reduce coastal erosion . </li></ul><ul><li>Mangoves can secure and trap enough sediments to form small islands – extend coastal land seawards. </li></ul>
  26. 36. Soft Engineering Measures <ul><li>Planting of Mangroves </li></ul><ul><li>E.g. Aceh – More than 5,000 mangrove seedlings were planted to rehabilitate coast devastated by 2004 tsunami. </li></ul>
  27. 37. Soft Engineering Measures <ul><li>Planting of Mangroves (-) </li></ul><ul><li>Not all coastal regions can support mangroves, especially in coastal regions with destructive waves. </li></ul><ul><li>As sediments build up along coast after planting mangroves, depth of coast may become shallower and thus affect port activities – (E.g. Pose a problem for countries like Singapore that depends heavily on maritime trade.) </li></ul>
  28. 38. Soft Engineering Measures <ul><li>Stabilising dunes </li></ul><ul><li>Dunes are so fragile that delicate shrubs struggle to hold them in place. </li></ul><ul><li>Access points to the beach should be controlled and designated so as to prevent dunes from being disturbed by human traffic. </li></ul>
  29. 40. Soft Engineering Measures <ul><li>Stabilising dunes </li></ul><ul><li>- Shrubs and trees can be planted to stabilise dunes because roots can reach downwards to tap groundwater and thereby anchoring the sand. </li></ul>
  30. 41. Soft Engineering Measures <ul><li>Growth of coral reefs </li></ul><ul><li>Coral reefs weaken wave energy. </li></ul><ul><li>Artificial reefs can be created along coast by placing environmentally friendly and durable materials such as steel or concrete on sea floor. </li></ul>
  31. 43. Soft Engineering Measures <ul><li>Growth of coral reefs </li></ul><ul><li>- These man-made reefs enhance fishing opportunities and serve as undersea barriers to reduce impact of wave energy. </li></ul>
  32. 45. Tyres used as man-made structure for coral reefs
  33. 46. Another example of man made structure as coral reef