Coasts GW3 Flashcards
Define Soft Engineering Measures
It involves protecting the coast using natural processes; does not involve the construction of any physical structures
Define Hard Engineering Measures
It involves the construction of physical structures to protect coasts against the erosive power of waves
Discuss with the use of examples, the effectiveness of gabions in managing coastal areas.
D:Gabions are wire cages usually filled with crushed rocks. These cages are built along a shore or behind a beach to prevent or reduce coastal erosions by weakening wave energy. Gabions absorb wave energy better than sea walls. This is because the gaps between the rocks allow water to filter through, proving gabions to be successful against high energy waves.
Ex: Seaton in Devon, UK. The rock-filled gabions have been positioned to the side of the cliff as an additional sea defence, to prevent the high tide and stormy seas from rushing through the gap at the side and around the back of the remaining pinnacle of rock, where they could potentially undercut the remaining rock on the landward side.
A: Gabion baskets that are placed on the outside of river bends prevent river bank erosion during floods. Geotech filter fabric is placed behind and underneath the gabion baskets to prevent the movement of soil material through the gabions, and prevent or reduce coastal erosions by weakening wave energy.
L: However, the wire cages are unsightly and are costly as they need to be maintained regularly. They are also easily corroded by seawater and damaged by excessive trampling or vandalism
Discuss with the use of examples, the effectiveness of seawalls in managing coastal areas.
D - Seawalls are walls that are built along and parallel to the coasts to reflect waves that hit against the sea wall, protecting coastlines against wave attack by absorbing wave energy.
Ex - Vancouver seawall built around the perimeter of Stanley Park in Vancouver, British Columbia began in 1917 and extends 22km in total.
A - Seawalls provide a high degree of protection against coastal flooding and erosion. It fixed the boundary between the sea and land to prevent further erosion, and coastal flood protection against extreme water levels, up to their design height.
L - Seawalls are costly to built and maintain as constant repairs may have to be made to prevent their collapse. They’re also only successful initially as backwash washes away the beach materials at the foot of and beneath the seawall, eventually undermining the base of the seawalls which lead to their collapse.
Discuss with the use of examples, how beach nourishment manages coastal areas
[ D ] Beach nourishment involves using sand from an external source to replenish the sand on a depleted beach . The external sources can be sand from other beaches or sand dredged from the sea floor . This measure helps slow down the erosion of beaches and successfully change a coast into a wide , sandy beach that offers protection to the immediate inland area .
[ Ex ] Beach nourishment restored the depleted beach at the coast of Cape May Point in New Jersey , United States of America where sand from an external source is used to replenish the depleted beach .
[A] Beach nourishment is able to change a coast into a wide sandy beach that provides immediate protection to the inland area.
[L] However , it is time consuming and costly in trucking or piping in the sand . Many beach nourishment projects have also given rise to other problems . For example , the coral reefs at Waikiki Beach were destroyed because sand used for beach nourishment was washed out to the sea and suffocated the corals . Other management strategies are required to be put in place at the same time to prevent the re - nourished beaches from being eroded .
Discuss with the use of examples, how encouraging coral growth would help manage coastal areas.
D: Coral reefs help to weaken wave energy and serve as a breeding ground and nursery for fish. Artificial reefs can be created by placing lasting materials, steel or concrete onto the sea floor. Corals, together with other marine creatures and vegetation, colonise these materials and start to function as a natural reef.
Ex: Since 1996, the Maldives, which is a low-lying archipelago in the Indian Ocean, has been operating a coral-growing programme to help curb severe beach erosion on its many islands. A structure of welded construction steel rods, 45m long, 4 to 8m wide and 1.5m high, has been placed off the coast of one of its resort islands of Ihuru. The structure is charged with low-voltage solar-generated electricity to speed up coral growth.
A: Coral reefs help to weaken wave energy, hence having less energy in the destructive waves, reducing erosion.
L: It is not easy to encourage the growth of corals. Sites need to be surveyed to ensure maximum opportunity for growth. Coral growth may be slow, taking perhaps 20 to 30 years before results appear. Even then, coral growth may not be significant
Discuss with the use of examples, how tetrapods manage coastal areas.
D: Tetrapods are four-pronged concrete structures that help dissipate wave energy. They are stacked offshore in an interlocking position. As they are pre-casted, they can be replaced quickly compared to other structures.
EX: The tetrapods at Yin Yang Sea, Taiwan. The tetrapods were introduced in 2006 to protect the area from typhoons, which occur on average, three to four times each year.
A: Tetrapods allow water to pass around them instead of hitting against them, hence no powerful backwash is generated, reducing damage by waves.
L: Tetrapods are aesthetically unappealing. They are also expensive to build so countries may not be able to afford. They can pose danger to swimmers and boaters due to its shape.
Discuss with the use of examples, how groynes manage coastal areas.
D: Groynes are low walls constructed at right angles to the shore to retain sediments that would otherwise be removed by longshore drift. They reduce the energy of the waves and cause materials to be deposited on the updrift side of the groyne facing the longshore drift.
Ex: Groynes were built along Sandy Hook in New Jersey，United States of America. Groynes(often called jetties)are perpendicular to the beach to trap sand flowing north towards Sandy Hook due to longshore currents.
A: It reduces the energy of waves and cause materials to be deposited on updrift side. The groynes also act as barriers and prevent materials from being transported away by longshore drift. Successful implementation can sustain and even extend beach areas.
L: However, they are unsightly and expensive to build and maintain. No new materials deposited on downdrift side which is not protected, limiting beach formation on the downdrift side.
Discuss with the use of examples, how breakwaters manage coastal areas
D: Breakwaters are structures built parallel to the coast or with one end attached to the coast, which help to break the force of oncoming waves. When constructed offshore, they create a zone of calm water behind it which are often used as a sheltered harbour for boats.
Ex: In Almera, Spain, breakwaters are built offshore to break the force of oncoming waves. The land behind the breakwaters are protected from erosion caused by corrasion and hydraulic action. A zone of calm water is created behind them, where sediments are deposited to build up the beach.
A: Breakwaters break the force of oncoming waves and create a zone of calm water behind them, protecting the coast successfully. They also tend to prevent beach erosion for short-term periods. Materials are deposited and built up in the done of calm water forming beaches.
L: However, Breakwaters are costly to build and maintain and as such, developing countries may not be able to afford it. Breakwaters protect the coast unevenly. Due to that, materials deposited in the zones behind breakwaters are protected but those located away from breakwaters maybe be subjected to wave action and erosion.
Discuss with example, how planting vegetation and stabilising dunes manage coastal areas.
D: Planting vegetation such as mangroves can stabilise coastlines, as mangroves wave energy through their dense root system. Sand dunes can be stabilised through planting grasses, which have roots that anchor the sand and prevent erosion.
Ex - the coast of Triton Place, Western Australia has vegetated sand dunes that stabilise the dunes, and grass that anchor the soil and prevent them from being eroded away.
A - As the wave energy is reduced by the mangroves, there will be less erosion, thus protecting the coastal areas.
L - However, the vegetation take many years to grown and are unable to protect immediate protection. It is also expensive the maintain the fences and paths to protect the sand dunes.
Discuss with the use of examples, how limiting damaging activities manage the coastal areas?
D: Damaging activities are activities that interrupt the functioning of natural systems. Banning of these damaging activities might be costly and inefficient, many national and local government bodies instead try to limit these activities. This is done through management that aligns the needs and demands of people together with the nature of the coastal environment.
Ex: One example of how damaging activities can be limited is the management of sand dunes in Port Phillip, Melbourne. The sand dunes were often trampled on by visitors, destroying the dune vegetation. Houses behind the dunes are also in danger if being partially buried by the sand being blown by wind. To combat this, authorities fenced off the dunes and built separate access paths to the beach, allowing the coastal environment to recover.
A: Through limiting of damaging activities but he coast, it allows the coastal areas to recover to before, reducing of erosion of coast by prevention or reducing of activities by the sea. With lesser activities on the coast, it results in lesser pollution and damage on coasts. Thus, limiting of damaging activities shows a positive impact on protecting of the coasts.
L: However, by limiting damaging activities by the coast, it reduces the number of people having fun by the coast, it will look less attractive and does not allow visitors to enter. This will cost the government economy loss through lack of tourist income. By reducing construction of facilities like docks and marines, it will result in lesser trade between counties and worsening of economy.
Discuss with example how protecting coastal resources help manage coastal areas.
D: Protecting coastal resources is a management strategy that aims to prevent resources from being exploited or depleted. An example of coastal resource that needs to be protected is fish. Areas close to the coastline where 90% of all marine fish are caught are vulnerable to overfishing. This occurs especially in the coral reef areas of SEA where destructive fishing methods of blasting and poison fishing are used.
Ex: One way to protect fishes, which are coastal resources, is to reduce plastic usage and water pollution. This can help reduce the amount of plastic ending up in the ocean. This reduces the chances of the marine animals mistaking them for food or being suffocated by them. The One Less Plastic campaign, launched in 2018, is a campaign to reduce plastic bag usage in SG.
A: Marine reserves protect marine ecosystems which allows fish and endangered species to breed and thrive. There are up to 14 times more snappers within the reserve then outside it. This demonstrates the positive management impact of protecting coastal resources.
L: However, the establishment of marine reserves is often strongly opposed by local fishermen. This is because the fishermen see their access to a valuable resource, and possibly a major source of food, being denied. The potential long term benefits of a marine reserve may not be significant to locals who can no longer fish in an area that has supported them for a long time.
Discuss with an example, how restricting development in areas prone to natural hazards help manage coastal areas.
D: Many national governments and local authorities have developed management policies to deal with the threat of natural hazards in coastal areas. They research on how severe or widespread the problem is, plan for it, then make and enforce laws. The laws and policies usually involve a combination of retreat, avoidance, and defence. These protect both the coastal environment from damage and erosion by humans and also protect people from the natural hazards.
Ex: In USA, the Federal Emergency Management Agency (FEMA) steers development away form areas prone to flooding or coastal erosion.
[retreat]
A: By restricting development in areas prone to natural hazards near the coastline, there will be less destruction of property and infrastructure, as well as less loss of lives. with less human activities near the coastline, less erosion will occur on the beaches and less sand will be lost.
L: People may not comply with the laws and may continue to illegally build businesses and infrastructure near the coastlines. This may cause problems for the government in charge of regulating the coastlines. The businesses built near the coastlines may also cause damage to infrastructure and loss of lives.
