Coasts KQ3 Flashcards
Evaluate how limiting damaging activities that interrupt the functioning of natural systems does to help manage coastal areas in a sustainable manner.
Damaging activities that interrupt the function of natural systems may include clearing mangroves for fish farms or agricultural land, dumping waste in to coastal areas and construction of facilities for ports and hotels which replace features at the coast. For example, Visitors trying to get to the beach in Port Philip, Australia, were trampling sand dunes and the vegetation growing on them . This led to the destruction of the vegetation and the erosion by wind of the dunes and the beach was deprived of a natural source of sand during large storms. Authorities fenced off the dunes and build access paths to the beach to allow dunes to recover. The sand dunes recovered and increased in size and the vegetation that reestablished in dunes prevented the erosion of the dunes. However, the fences made the beach look less attractive and did not allow beach goers easy access to all parts of the beach.
Evaluate how protecting coastal resources by preventing resources from being exploited and depleted helps to manage coastal areas in a sustainable manner.
This can be achieved by limiting areas where people get that resource or limit the amount of resources that can be extracted. In Wakatobi, Indonesia, certain areas were identified as locations where fish gathered to spawn. Fisherman used to target these gatherings which destroyed the population before the fish could spawn. The Wakatobi National Park was established to protect the spawning fish by marking off these areas to prevent commercial fishing during the spawning. This measure has protected the existing fish stock and increased the number of spawning fish and recovery of the entire population is expected to follow. However, establishment of marine parks is often strongly opposed by local fisherman who see their source of income and food being greatly affected.
Evaluate how the restriction for development in areas prone to natural hazards helps manage coastal areas in a sustainable manner.
This reduces the type of buildings and number of people living in areas prone to natural hazards. For example, the large earthquake that hit Tohoku, Japan, caused a tsunami that swamped large areas of the coast. By restricting the development in these areas to mainly industrial and agricultural uses, the number of deaths and cost of damage was reduced due to the lower population density and lower number of buildings in the area. However, many people are still attracted to coastal areas because it provides a source of food and building material. Coastal areas also provide ports and recreational facilities.
Evaluate the soft engineering measure that is beach nourishment.
Beach nourishment involves using sand from an external source to replenish sand on an eroded beach. For example, Siloso, Palawan and Tonjong beaches in Sentosa where sand obtained from another beach or dredged from the sea floor from Indonesia and Malaysia was brought in to replenish these beaches. This resulted in a wide sandy beach that was aesthetically pleasing and acts as a tourist attraction. However, importing sand is expensive and time consuming. Imported sand might also be washed out to sea and smother other coastal ecosystems like coral reefs. Replenished beaches may also continue to be eroded unless other protection measure are put in place.
Evaluate the soft engineering method that is plating vegetation on dunes to stabilise the sand.
Sand dunes provide a barrier to storm waves and protect the area behind the dunes from flooding. Sand dunes also provide a supply of sand to the beach, limiting the amount of erosion to the beach due to storm waves. For example, Triton Place, Western Australia, grass was planted over the dunes to stabilise the dunes along the coasts. The roots of the grass anchored the sand and prevented the erosion of the dunes by wind. The dunes became more stable, preventing the sand from being blown away and thus acted as a natural source of sand for the beach when large storm waves erode the beach. However, vegetation may take a number of years to be established before it can resist wind and wave erosion. Trampling by beach goers will destroy the vegetation planted on the dunes, unless fences and pathways are built which will cost money to build and maintain.
Evaluate the soft engineering method that is replanting mangroves
Mangrove forests can be can be helped in areas where they have suffered deforestation due to human activities such as land clearing or harvesting for wood. For example, Bintang Island, Indonesia. Since 2007, over 18,000m2 of mangroves have been replanted along the Sebung River. Dense network of roots absorb the energy of waves protecting the coast from erosion and storm waves. The network of roots also slow down the flow of water allowing sediments washed down by rivers to build up among the mangrove roots, building up land. However, mangroves take time to get established and the trees can take many years to mature leaving the coast open to erosion during this time. Also the success of using mangroves is site dependent as mangroves can only grow along sheltered coasts with brackish water and therefore may not be able to protect entire coastlines.
Evaluate the soft engineering method that is encouraging coral reef growth.
Coral reefs are massive limestone structures that grow the shallow offshore areas of coastlines. Coral reefs that have been damaged through human activities can be restored through various means. For example, in the Maldives, a coral growing program was started to curb beach erosion. Steel structures placed off the coast was charged with low-voltage solar-generated power to speed up the growth of coral on these structures. Coral reefs help absorb and weaken wave energy, reducing the amount of coastal erosion from storm waves. The island now sustains a large variety of corals, marine animals and organisms. However it is not easy to encourage coral growth, as sites have to be surveyed and carefully chosen as not all areas are suitable for coral growth and thus may not be suitable to protect entire coastlines. Corals also grow very slowly and effects may not be seen for 20-30 years.
Evaluate the hard engineering measure that are seawalls.
Seawalls are structures made of concrete or stone and are built parallel to the coast. They are constructed to protect the coast by deflecting the energy of waves away from the coasts. Seawalls are built in thousands of locations around the world, for example along the coast on the Isle of Wright, U.K. Seawalls are an effective short-term measure to protect property and buildings built behind the seawall. However, seawalls are costly to build and maintain and offer only initial success. The powerful backwash of reflected waves erodes the material at the base of the seawall leading to its eventual collapse.
Evaluate the hard engineering method that are gabions.
Gabions are wire cages filled with crushed rocks. They are built along a shore or behind a beach to prevent or reduce coastal erosion by weakening wave energy. Gabions were used to protect East Coast Park when it was first reclaimed. Gabions absorb wave energy better than sea walls as the gaps between the rocks allow the water to filter through. Thus, the backwash is as powerful reducing erosion at the base of the gabion. However wire cages are unsightly and they are costly, as the cages have to be maintained constantly due to the rusting of the wire cages. Beach goers trampling on them to get into water also easily damage them.
Evaluate the hard engineering method that are breakwaters.
Breakwaters are structures that are built either parallel to or with one end attached to the coast. Breakwaters help to break the force of the approaching waves. For example, breakwaters are built to protect the beaches at East Coast Park, Singapore. The clam water behind the breakwaters allows deposition of sediments and beaches to form and the calm water can also be used as a sheltered harbour for boats. However, breakwaters are not aesthetically appealing and are costly to build. They also protect the coast unevenly as only areas behind them are protected while exposed areas are not.
Evaluate the hard engineering method that are groynes.
Groynes are low walls built at right angles to the coast. They retain sediments that would have been removed by longshore drift. They trap beach material on the up drift side of the groyne facing longshore drift. For example, a series of groynes were built along the coast of East Bourne, U.K. Sometimes the tips of the groynes are angled according to the direction of prevailing waves and if successful, groynes can help protect and even extend beach areas. However groynes are unsightly and expensive to build and maintain and since no material is deposited on the downdrift side of the groyne, longshore drift will erode away that part of the beach.
Evaluate the hard engineering method that are tetrapods.
Tetrapods are four-pronged concrete structures. They are stacked offshore in an interlocking position like a breakwater, or at the base of a sea wall and absorb some of the energy of approaching waves. For example, tetrapods are used in Crescent City, California to defend against coastal erosion. Tetrapods allow some water to flow through the interlocking structure which reduces the powerful backwash that occurs when walls are used and can also be placed quickly into position when needed. However they are unsightly and expensive to build and are also dangerous to swimmers and boaters.
