Coasts gateway 3 Flashcards
How to manage coastal areas in a sustainable manner?
- control the development and change in the coastal zones by following agreed on principles and criteria
- development should not compromise the quality of the coastal environment for present and future generations and should have little to no deterioration after development
Managing coastal areas in a sustainable manner through Laws and regulations
-limiting damaging activities
- damaging activities affect the functioning of natural environments (eg. blasting coral reefs)
- it is costly and ineffective to ban damaging activities so the government limits damaging activities through balancing the needs and interests of the people with the needs of the coastal environment
eg. Port Philip. sand dunes are often trampled on. Dune vegetation is destroyed and sand dunes are vulnerable to wind erosion. houses are partly buried under huge volumes of sand. The government fenced off areas and built access paths to the beach to allow the coastal environment to recover, but the fences are aesthetically unappealing and the access paths do not allow residents and visitors access to all parts of the beach
Managing coastal areas in a sustainable manner through Laws and regulations
-protecting coastal resources
- this prevents coastal resources from being exploited and depleted
- 90% of marine life are vulnerable to overfishing, especially in southeast asia
-eg New Zealand. Zones are marked off to prevent commercial fishing. This is done through the local management of a marine reserve. the marine reserve protects the coastal environment and allows fish and endangered marine life to thrive
POSITIVE IMPACT:
- The marine reserve is now a tourist attraction due to its plentiful supply of fish. There are 14 times more snappers in the reserve then outside
NEGATIVE IMPACT:
-However, local fishermen strongly opposed the establishment of the marine reserve as their access to their source of food and income is denied
-The potential long-term benefits are not significant to locals who can no longer fish there
Managing coastal areas in a sustainable manner through Laws and regulations
-restricting development in areas prone to natural hazards
- natural hazards damage coastal environments
- eg 2011 tohoku earthquake triggered a tsunami that swamped large areas of coastal japan. 20,000 people died and coastal areas and nuclear power plant were damaged. cost of rebuilding was approx US$300 billion
- Coasts provide us with natural resources like building materials and built resources like ports
- people who live there need to spend more on construction and maintenance and be prepared for emergencies
-the government researches on how widespread and severe the damage is so that they can plan and make and enforce laws
done through:
1.retreat and relocation of built services in areas prone to natural hazards. This steers development away from areas prone to flooding and coastal erosion
2. avoidance. The Indonesian law restricts developments on low-lying coastal areas
3. Defence like building sea walls or beach nourishment. Eg beaches in The Netherlands are closely monitored and undergo beach nourishment when long-term erosion is identified
Soft engineering measures
- Beach nourishment
- planting vegetation and stabilising dunes
- encouraging coral reef growth
Soft engineering measures
-beach nourishment
-uses sand from another source to replenish a depleted area. The sand is usually from the sea bed or another beach
POSITIVE IMPACTS:
-reduces rate of erosion
-can turn a beach into a white sandy beach that provides protection to the immediate inland area
-eg sentosa, sg. Siloso, Palawan, Tanjong beaches underwent beach nourishment and became aesthetically pleasing
NEGATIVE IMPACTS:
-expensive and time consuming
-sediments may spill into the ocean, suffocating the corals
-the beach will get eroded again unless some other management measure is put in place
Soft engineering measures
-planting vegetation and stabilising dunes
-planting vegetation (eg mangroves) help to stabilise dunes (eg mangroves absorb wave energy through their dense root network). However, it takes a long time for the vegetation to be established and string enough to withstand natural elements like storms and human elements like trampling
- grasses can help to stabilise sand dunes as the roots of the grasses anchor the san and prevent erosion.
- Matting can be placed over the sand dunes and the young grasses are planted through the matting.
- Over time, as the grasses become established and the dunes become more stabilised, the matting rots away, adding nutrients to the sand.
- the government builds fences and access paths to the beach to protect the sand dunes from human traffic
- fences are expensive as they require constant maintenance because they have to be replaced with taller ones as the sand accumulates
- signboards are put up to inform the public and develop positive attitudes towards these strategies
Soft engineering measures
-encouraging coral reef growth
- coral reefs absorb wave energy and act as a breeding ground and nursery for fish
- Artificial reefs are created by placing lasting materials like steel onto the sea floor. Coral, marine life and vegetation colonise it and it acts as a natural reef (eg. Pulau. Sunken ships have been naturally colonised by corals)
- Maldives is operating a coral-growing programme to curb the severe beach erosion. Welded construction steel rods are placed off the coast of one of its resort islands and is charged with low voltage, solar powered electricity to speed up coral growth. The corals grow 3-5 times faster and the island now sustains a wide variety of coral, marine life and organisms
- however, coral reefs take a long time to grow and require 20-30 years before results are seen, and the results may not be significant and the site has to surveyed beforehand to ensure maximum opportunity for growth
Hard engineering measures
- seawalls
- gabions
- breakwaters
- groynes
- tetrapods
Hard engineering measures
-seawalls
-made of concrete/steel and built parallel to the coast
POSITIVE:
-helps to absorb wave energy
NEGATIVE:
-costly to build and maintain
-only absorbs some wave energy and reflects incoming waves
-there is only initial success as the powerful backwash washes away the sediments at the foot and base of the seawall. erosion eventually undermines the base of the seawall causing it to collapse
Hard engineering measures
-gabions
-wire cages filled with crushed rocks
POSITIVE:
-reduces or prevents coastal erosion by weakening wave energy
-weakens wave energy as water travels through the holes between rocks and are successful defences against high energy waves
NEGATIVE:
-costly as they require constant maintenance, aesthetically unappealing, easily corroded by seawater, damaged by trampling or vandalism
-eg. East Coast park, Singapore used to have gabions but they were removed due to vandalism
Hard engineering measures
-breakwaters
-break the force of oncoming waves
-built parallel to the coast or with one end attached to the coast
POSITIVE:
-when built offshore, it creates a zone of calm water behind. Sediments are deposited and build up in the zone of calm water to form beaches. The zone of calm water is also used as a sheltered harbour for boats
NEGATIVE:
-costly to build and maintain, aesthetically unappealing, protects the coast unevenly
-sediments deposited away from the breakwater are subjected to wave action and erosion while those deposited behind the breakwaters are protected
-eg. England. breakwaters resulted in erosion and flooding
Hard engineering measures
-groynes
-low walls constructed at 90 degrees to the coast
-to reduce erosion on the downdrift side, tips of the groynes are tilted at 10 degrees
POSITIVE:
-retains sediments that would otherwise be carried away by longshore drift
-helps to absorb and reduce wave energy. sediments are deposited on the updrift side of the groyne facing longshore drift
NEGATIVE:
-unsightly, costly to build and maintain
-no new materials are deposited on the downdrift side of the beach not protected y the groyne. Longshore drift will erode away sediments on the unprotected parts of the beach
Hard engineering measures
-tetrapods
-dissipate wave energy
-stacked offshore in an interlocking position and allows water to pass through it so no powerful backwash is generated
POSITIVE:
-can be placed quickly
-eg. Crescent City, California. tetrapods were used to defend against coastal erosion and it helped to reduce the impact of tsunamis
NEGATIVE:
-aesthetically unappealing, costly to build and maintain, poses as a danger to swimmers, surfers and boaters
