coastal management 4
DESCRIPTION
coastal managementTRANSCRIPT
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Coastal Management
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• Large scale development of coastal areas will bring about problems if development is not properly planned and managed.
• Proper coastal management and protection are needed to preserve quality of coastal environment.
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Lost Villages Due to Coastal Erosion
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Types of Approach
• Hard engineering
- Refers to the construction of physical structures to defend against the erosive power of waves.
- Also known as the structural approach.
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Types of Approach• Soft Engineering- Focuses on planning and management
so that both coastal areas and properties will not be damaged by erosion.
- Also aims to change individual behaviour or attitude towards coastal protection by encouraging minimal human interference and allowing nature to take its course.
- Also known as the non-structural approach.
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Hard Engineering Measures• Seawalls (+)
- Seawalls absorb the energy of waves before they can erode away loose materials.
- Seawalls can be made of concrete, rocks or wood.
- They are effective in protecting cliffs from erosion.
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Hard Engineering Measures
• Seawalls (-)
- 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.
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Hard Engineering Measures
• Seawalls (-)
- Base of seawalls will be undermined (weakened) and leads to their collapse.
- Seawalls are costly to build and maintain as constant repairs have to be made to prevent their collapse.
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Hard Engineering Measures
• Breakwaters
- Protect coast and harbour by reducing force of high energy waves before they reach the shore.
- They can either be built with one end attached to the coast or built away from coast.
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Hard Engineering Measures• Breakwaters (+)
• Breakwaters
- Protect coast and harbour by reducing force of high energy waves before they reach the shore.
- They can either be built with one end attached to the coast or built away from coast.
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Hard Engineering Measures
• Breakwaters (-)
- Materials deposited in the zones behind the breakwater are protected while those in the zones located away from the breakwater are not.
- Zones will not receive any new supply and thus be eroded away.
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DEPOSITION
EROSION
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Hard Engineering Measures
• Groynes
- Built at right angles to the shore to prevent longshore drift.
- 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.
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Hard Engineering Measures
• Groynes (-)
- Erosion can still take place on the part of the coast that is not protected by groynes.
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Hard Engineering Measures
• Gabions
- 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.
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Hard Engineering Measures
• Gabions (-)
- This method offers only short-term protection (about five to ten years).
- Wire cages need regular maintenance as they are easily corroded by sea water.
- Affected by excessive trampling and vandalism.
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Hard Engineering Measures
• Gabions (-)
- Can be unsightly and become a danger along the beach.
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Soft Engineering Measures
• Beach nourishment
- Refers to constant replenishment of large quantities of sand to the beach system.
- Beach is therefore extended seawards, leading to improvement of both beach quality and storm protection.
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Soft Engineering Measures
• Beach nourishment (-)
- Very expensive and impractical to constantly transport large quantities of sand to fill up beach.
- Imported sand that can be continuously eroded and transported away could have serious consequences on wildlife living within coastal environment.
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Soft Engineering Measures
• Beach nourishment (-)
- E.g. Coral reefs at Waikiki Beach of Hawaii are destroyed as imported sand gets washed out to sea and covers the corals.
- Corals are deprived of sunlight they need to survive
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Soft Engineering Measures
• Beach nourishment (-)
- E.g. Singapore – Large scale land reclamation along coast has led to muddy and polluted water and has destroyed coral reefs.
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Soft Engineering Measures• Relocation of Property
- Coastal planners protect man-made structures (e.g. buildings) by relocating them and letting nature reclaim the beach in its own time.
- No building of new properties of structures would be allowed in coastal areas that are vulnerable to coastal erosion.
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Soft Engineering Measures
• Relocation of Property
- 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.
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Soft Engineering Measures
• Relocation of Property (-)
- Opposition by people with considerable investments in coastal areas.
- This approach will be important in future coastal management due to rising sea level as a result of global warming.
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Soft Engineering Measures
• Planting of Mangroves
- Mangroves have long and curved roots that prop up from soil. It traps sediments and reduce coastal erosion.
- Mangoves can secure and trap enough sediments to form small islands – extend coastal land seawards.
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Soft Engineering Measures
• Planting of Mangroves
• E.g. Aceh – More than 5,000 mangrove seedlings were planted to rehabilitate coast devastated by 2004 tsunami.
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Soft Engineering Measures• Planting of Mangroves (-)
- Not all coastal regions can support mangroves, especially in coastal regions with destructive waves.
- 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.)
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Soft Engineering Measures• Stabilising dunes
- Dunes are so fragile that delicate shrubs struggle to hold them in place.
- Access points to the beach should be controlled and designated so as to prevent dunes from being disturbed by human traffic.
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Soft Engineering Measures• Stabilising dunes
- Shrubs and trees can be planted to stabilise dunes because roots can reach downwards to tap groundwater and thereby anchoring the sand.
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Soft Engineering Measures• Growth of coral reefs
- Coral reefs weaken wave energy.
- Artificial reefs can be created along coast by placing environmentally friendly and durable materials such as steel or concrete on sea floor.
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Soft Engineering Measures• Growth of coral reefs
- These man-made reefs enhance fishing opportunities and serve as undersea barriers to reduce impact of wave energy.
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Tyres used as man-made structure for coral reefs
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Another example of man made structure as coral reef