Coasts Gateway 3 (managing coastal areas) Flashcards
HARD ENGINEERING MEASURES: Seawalls
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Seawalls are walls made of concrete that are built parallel to the coast, separating land and water areas. They are constructed to protect coastlines against wave attacks by abosrbing energy, which helps to reduce coastal erosion.
Ex: Skara Brae in Scotland UK, had its first seawalls constructed in late 1920s, which were 4 metres in height. They act as a protective barrier that absorbs the brunt of wave action, protecting infrastructure from getting eroded.
A: Curved or stepped seawalls dissipate wave energy and repel waves back into the sea, preventing waves from overtopping the wall and providing additional protection for the toe of the wall. The steep slope enables maximum dissipation of wave energy.
L: Seawalls are costly to build and have to be constantly repaired to prevent them from collapsing. As the waves are reflected back, the strong backwash washes away beach material at the foot of and beneath the seawall, undermining the base and causing them to collapse. This causes water to flood in and towards the houses.
HARD ENGINEERING MEASURES: Gabions
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Gabions are wire cages filled with crushed rocks, built along a shore or behind a beach to prevent or reduce coastal erosion by weaking wave energy (usually more successful than seawalls)
Ex: Gabions are installed at East Coast Park in Singapore when it was first reclaimed in the 1970s. They were to prevent further erosion of Singapore’s coasts.
A: Gabions absorb wave energy better than seawalls as the gaps between the rocks allow water to filter through, proving to be successful defences againse high energy waves.
L: They are unsightly which may deter tourists from coming to the coast. They need to be maintained regularly and is hence costly. Excessive trampling and vandalism and seawater also corrode the gabions.
HARD ENGINEERING MEASURES: Breakwaters
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Breakwaters are structures built either parallel to the coast or with one end attached to the coast, breaking the force of oncoming waves. They are built offshore to create a zone of calm water behind them, causing water to be deposited.
Ex: Portland Harbour, England, consists of 4 breakwaters, having a total length of 4.57km and about 1000 hectares of water. With one end attached to the coast, an enclosed area is formed.
A: They prevent destructive waves from reaching the beaches, greatly reducing erosion of sediments due to wave action. The zone of calm water enables beaches to be formed for tourists to use.
L: They also protect coasts unevenly as zones not protected by breakwaters are still vunerable to wave action and erosion, while areas protected by breakwaters are protected. This may result in flooding problems as well.
HARD ENGINEERING MEASURES: Groynes
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Groynes are low walls constructed at right angles to the coast to retain sediments that can be removed by longshore drfit. They reduce wave energy of the waves and cause materials to be deposited on the updrift side facing oncoming longshore drift.
Ex: In Sandy Hook New Jersey, United States, Groynes are built perpendicular to the beach that trap sand flowing north towards Sandy Hook in the direction of Longshore drift.
A: A groyne functions as a physical barrier by intercepting sand moving along the shore, sustaining and extending beach areas, by preventing or reducing the erosion of beach materials on the downdrift side of the groyne. The accumulation of sand on the updrift side forms a wider beach.
L: They are unsightly and hard to maintain. The downdrift side is not protected and hence no new material is deposited there, and erosion of sediments there by longshore drift occurs.
HARD ENGINEERING MEASURES: Tetrapods
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Tetrapods are 4 pronged concrete structures that help disspate and abosrb wave energy. They are stacked offshore in an interlocking position. They are pre-casted and can be placed quicky compared to other structures.
Ex: In Crescent City Northern California, they have used tetrapods to defend against coastal erosion and to reduce the impact of tsunamis which occured 31 times between 1933 and 2008.
A: They reduce wave energy as they allow water to pass through them, hence no powerful backwash is generated, reducing erosion by the waves.
L: They look ugly. They also pose as a danger for swimmers and surfers and boasters due to its sharp edges and shape. They are expensive, hence poorer countries may not be able to afford them.
SOFT ENGINNERING MEASURES: Beach Nourishment
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Beach nourishment involves using sand from an external source such as another beach to replenish the sand on a depleted beach.
Ex: In Sentosa Singapore, where beach material of fine sand was brought to replenish Siliso, Palawan and Tanjong beaches, making them look nice
A: Beach nourishment can successfully change a coast into a wide, sandy beach that offers protection to the inland area. It attracts more visitors due to its enhanced looks. It also reduces the damage caused by storms, and a very efficient energy absorber.
L: Piping in sand for beach nourishment is time consuming. Coral reefs are also stressed and suffocate as sand is dumped onto them. Overtime, re-nourished beaches are also erode unless other management measures are put in place.
SOFT ENGINNERING MEASURES: Planting Vegetation and Stabilising Dunes
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Planting vegetation is used to stabilise coastlines, such as grasses which stabilise sand dunes. The roots of the grasses anchor the sand and prevent erosion. Matting is put over the dunes and also used to plant the sand.
Ex: Along the west Bali beach, mangroves help to stabilise coastlines as the dense root systems anchor the sand to the ground and absorb wave energy
A: The vegetation help to reduce the high wave energy on oncoming waves, making the impact of erosion from the waves less severe. Mangroves also act as habitats to sustain marine life ecosystems. The matting rots away and provides nutrients to the sand.
L: Vegetation may take a very long time for it to be fully established, and it is prone to trampling and vandalism by humans. To prevent this, fences and access paths must be built which may be expensive and hard to maintain as sand accumulates.
SOFT ENGINNERING MEASURES: Encouraging coral growth
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Coral reefs can help to weakn wave energy and serve as a breeding ground and nursery for fish. The corals, together with other marine creatures function as a natural barrier and protects the coasts from being easily eroded.
Ex: In Ihuru, Maldives, since 1996, a coral-growing programme was started to reduce beach erosion. Steel rods with solar generated electricity is used to speed up coral growth.
A: With increasing corals and more marine animals, there are more barriers to help absorb wave energy and protect the coasts from wave action and storm surges. Properties in coastal areas are also protected.
L: Coral reefs take 20 to 30 years to grwo before visible results, and may not be significant. Sites also need to be surveyed to ensure maximum opportunity for growth.
LAWS AND REGULATIONS: Limiting damaging activities
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Limiting and reducing activities that interrupt the functioning of natural systems, such as blasting coral reefs to create channel for boats and dumping waste into coastal areas. This is done through management that is aligns the needs and demands of people working together with the nature of the coastal environment.
Ex: In Port Phillip, Melbourne, sand dunes were often trampled by visitors. To combat this, authorities fenced off the dunes and built separate access paths to the beach, allowing for coastal areas to recover.
A: They provide favourable conditions that facilitate the recovery of the coasts, attracting more visitors to the place and generating revenue.
L: Limiting access to parts of the beach may cause the beach to be less popular amongst tourists, causing business to suffer due to lack of people visiting the beach.
LAWS AND REGULATIONS: Protecting coastal resources
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Protecing coastal resources is a management strategy using Laws and Regulations to prevent resources from being exploited or depleted as a result of visitors using them.
Ex: In Goat Island Marine Reserve in New Zealand, zones have been marked off to prevent commercial fishing, through local management or establishment, protecting fish from being vulnerable to overfishing.
A: This prevents fish from being extinct and continue to breed and grow, sustaining the ecosystem near coasts.
L: The establishment may be strongly opposed to many fisheermen as they see fishing as their source of income and food being denied. Hence they may become poor and not have sufficient food
LAWS AND REGULATIONS: Restricting development in areas prone to natural hazards
Ask yourself for D: What are they made of? How are they constructed? Where are they constructed? Why are they constructed?
D: Limiting development and construction of buildings and houses near coastal areas. The government must do a research about the threat of natural hazards in the areas and make and enforce laws.
Ex: In USA, the Federal Emergency Management Agency steers development away from areas prone to flooding or coastal erosion, and retreating from the coasts to prevent natural hazards from destroying structures
A: There will be less destruction of property and infrasturcture, as well as loss of lives as buildings will not collapse on top of humans as a result of strong wave action or strom surges. Less human activities also results in less trampling and weaking of the sand
L: People may not comply with the laws and build businesses near coastlines, causing damage and loss of lives and creating problems for the government.
