Coastal Management

Coastal Management Hard Engineering Strategies Building sea walls  Build vertically on the inland part of the shore  Eg. Seawalls are built at coastal areas of Seletar facing the Straits of Johor Breakwater  Made of granite  Creates a zone of shallow water between itself and the coast so that waves will break against it before reaching the coast.  At East Coast Park/Siloso beach, breakwaters were built to reduce wave erosion

Benefits/Pros  They are able to reflect and absorb the full force of waves, reducing wave effects on the shore

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When oncoming waves hit these breakwaters, their erosive power is concentrated on these structures some distance away from the coast, resulting in an area of quiet waters behind the breakwaters. Marina for yachts and other small boats can also be developed in the protected water behind the breakwaters.

Problems/Cons  Needs to be maintained to prevent it from collapsing  A strong backwash is resulted when the energy from the waves is redirected down to the base of the seawall as waves break against the seawall. This causes the seawall to weaken and collapse eventually  Sea walls make access to the beach more difficult and can discourage tourism.  The nearby unprotected section of the coast does not receive a fresh supply of deposits and is susceptible to coastal erosion.

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Breakwaters built offshore take away energy from the coast and protect marinas and harbours. They are effective at retaining sand to form beaches and also prevent the loss of artificial beaches, which otherwise are lost to deep waters.

Groynes  They can act as ‘artificial’ headlands, reducing wave energy, causing materials to be deposited on the side facing longshore  They are low walls built at right angles to prevent materials from drift, protecting coast from erosion. being transported away by the  By preventing the removal of beach materials by longshore drift, longshore drift. cliffs behind the coasts are protected as well.  They are found at East Coast Park  The beach may be extended and enlarged through accumulation in Singapore. of deposited materials Gabions  It absorbs and reduces wave energy, reducing coastal erosion  Wire cages that contain small rocks  They can dissipate energy from waves or other impacts more to form a wall to protect the coast easily than a solid wall. from erosion.  Instead of deteriorating over time, they may become more  Can be found at the Hornsea effective due to strengthening of the structure by vegetation Beach in England. growing in the voids between the rocks and materials encaged. Conclusion: best  breakwaters Seawalls and Gabions require regular maintenance whereas breakwaters do not require regular maintenance Breakwaters have an added function than groynes, which is its ability to develop marinas behind it

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Materials accumulate on the updrift side of the groynes, so beaches on the downdrift side will not receive their fresh supply of fresh beach materials by longshore drift. Erosion still occurs at the downdrift side. Beaches will be easily eroded during storms. Building more groynes spoils the natural beauty of the coastal environment. They are easily destroyed by powerful waves during storms and the wires rust easily. They also ruin the natural beauty of the environment. It is only a short-term protection of about 5-10 years

Soft Engineering Strategy Stabilising Coastal Dunes - It is a ridge of sand piled up by wind on the coast as a result of vegetation trapping and stabilising sand. - The Omaha Beach in New Zealand is stabilized by marram grass Planting mangroves - Protect the coast against strong winds and waves - In parts of Acheh, Sumatra, thousands of mangrove seedlings have been planted to rehabilitate coast devastated by tsunamis

Effectiveness - Vegetation minimizes erosion - They act as barriers along the coast and protect human property - They provide a habitat for many animals like migratory birds

Ineffectiveness - Strong winds will cause sand to skip and collide with other particles, resulting in sheet flow. - Human activities have to be minimized for coastal dunes to work well

- It absorbs wave energy, and their roots anchor the soil firmly, reducing soil erosion - It is a habitat for many animals (encourages biodiversity) - We can obtain food, medicine and wood from mangroves, giving us income - It reduced the number of casualties in 2004 Indian Ocean Tsunami successfully by reducing wave energy.

- Takes a long time to grow and take effect - Requires protection from animals while growing, and from deforestation - Takes up a lot of land - Can only be grown in tropical regions -Depth of the coast may become shallower due to sediment build-up along the coast, in turn affecting coastal transportation and port activities. - However, it deprives marine life of light they need to survive. - It only lasts for 10years, and is unsustainable. - It requires constant replenishment, and sand is a limited resource.

Beach nourishment - Adding of large amounts of sand to a beach - For example, beach nourishment on Gold Coast in Australia widened the beach, improving its quality. Growth of coral reefs - Coral reefs are grown In Maldives, coral growing has been carried out to combat beach erosion on many islands.

- Replenishes eroded sand - This extends the beach seawards, improving both beach quality and storm protection.

- They can be natural breakwaters, absorb wave energy, reducing erosion. - They provide habitat for marine life.

- However, coral reefs are easily damaged by mining, dredging and pollution. - Water pollution and land reclamation destroy coral reefs.

CONCLUSION Planting mangroves is the most effective way. Growth of coral reefs and stabilising coastal dunes only reduce wave energy, reducing erosion. However, planting mangroves reduces erosion and also traps sediment, saving coral reefs from choking due to too much sediment accumulated. Beach nourishment is not as effective as planting mangroves as it endangers marine life