To manage a coast successfully, the effects of erosion, flooding and unwanted deposition must all be minimized as much as possible. Furthermore the protection of people and their property also forms a good basis of good coastal management. It is true that to be able to set up good defences, the natural systems surrounding the coast must be understood, as this ultimately allows the management agencies to fully examine and decide the type of management that should be used.
Coastal processes such as erosion and deposition are the main natural systems that affect our coast and thus must be monitored to ensure the best management strategy is in place. However the wave type and the amount of wave energy that is apparent at that stretch of coast ultimately decides the rate of erosion and deposition. The energy input of a wave is due to the wave height; the distance between the crest and the trough, the wave period; the time taken for a wave to travel through one wave length, and the wave steepness; the ratio of the wave height and wave length.
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Furthermore, the fetch of the wave will also influence the amount of energy that a wave has and therefore a wave with a high-energy value will potentially cause more damage than a wave with a low energy value. Spatial variations may cause this trend to fail, but even so a wave with more energy will have more impact on the coastline. Along the Kenyan coast, some small coral reefs can be found. These help to minimize wave energy and thus prevent rapid rates of erosion. However, due to tourism these are becoming destroyed and die, and as such cause more erosion on the coast of Kenya.
The shape of the beach will also determine how damaging the effects of waves are. A steeply shelving beach creates higher and steeper waves than one with a gentle gradient. And therefore to protect this area, there must be management schemes in place, such as groynes, sea walls or gabions. Beach width will affect the rate of cliff erosion as the wider the beach, the greater the loss of energy (waves take longer to pass over it) and as a result will cause less erosion on cliffs and coastal towns.
Furthermore the amount of beach material present will help to reduce wave energy and thus decrease cliff erosion. With this knowledge, planners can decide the best strategy for that particular area – if the area has a small beach with limited amount of material, then harder forms of engineering are to be used to stop erosion and transportation than in an area with a wide beach and plenty of material. The topography and geology of the coast will influence the rate of erosion. The strength of coastal rocks influences the strength of erosion.
In Britain, it is coastal areas where a glacial till was deposited which are being worn back rapidly. Therefore if the area that needs some sort of coastal management has a the knowledge of the geology, then a successful scheme can be put in place relating to the needs of the area. For example the volcanic ash of Krakatoa erodes at a rate of 40m/year whereas the granite in southwest England erodes at a rate of 0. 001m/year, and thus more coastal management would have to be in place in Krakatoa than in southwest England.
This is an extreme example, but is used to demonstrate how different geologies will affect the management strategy in place. Different areas along the coast will therefore have different erosion based landforms. Headlands and bays are most likely to be found in areas of alternating resistant and less resistant rock. The headlands will receive more wave energy and so become more vulnerable to erosion than the sheltered bays. Thus the bays experience low energy breakers that allow sand to accumulate and protect that part of the coastline.
The transportation and deposition of sediment will warrant certain areas to have a higher level of management. Due to long-shore drift, sediment is being removed from areas and being deposited in others. This therefore causes problems of erosion in the area where the sediment has been removed. Consequently many management agencies set up groynes to trap sediment and as a result help to protect their stretch of coastline. However, further down the coast, areas will be starved of sediment, hence causing much more rapid erosion and extreme problems for the coastal towns.
For that reason planners must take a holistic view of the coastline, to ensure that management schemes in one area will have extreme adverse effects on another. Sediment cells are the movement of sand and shingle-sized sediment in the near shore zone by long-shore drift. These major cells are defined as a length of coastline and it’s associated near shore area where the movement of coarse sediment is largely self-contained. Sediment cells are increasingly forming the basis for coastal management schemes, and sub cells such as near Christchurch Bay are used to repopulate the beach with sediment.
If agencies such as DEFRA and local councils appreciate the advantages of sediment cells, and how they can be used as a means to reduce erosion, then schemes would be put in place to maximise the use of sediment cells, and may therefore reduce the need for hard engineering. Even with knowledge of a particular coastline and the natural processes that are developing and affect the area, coastal management is extremely complex, with a high inter-relationship between different stretches of coasts. Furthermore, the sea and its effects are highly unpredictable, especially with rising sea levels due to climate change.
The North Sea storm surge of January and February 1953, which were expected to occur only once in 100 years, might become a 50 year, 20 year, or even 10 year event due to global warming and the melting of the ice caps. This prompted the building of the Thames Barrier, as the protection for London needed to be greatly improved. Completed in 1982, it allows for the controlling of water throughout the Thames River and the gates are raised to form a barrier across the river during flood and storm alerts. This is one case where management was needed to protect the people and property of London.
If this were not constructed, areas such as Lambeth, Newham, Southwark and Westminster would be under regular threat of flooding. With knowledge of natural systems along a coast, schemes be it hard or soft engineering will be able to work in unison with the coast and the natural effects of the sea. It would be ridiculous to retreat from a highly populated area with large industries and allow the coast to be eroded back as the economy would fall, people would lose homes and jobs and there would be political unrest.
So therefore agencies do not only look at the natural systems that affect the coast, but look at the use of land that will be affected by mismanagement. To be able to study and then act on natural systems along a coast are all linked to the development of the country and its technological advancement. The Thames Barrier as previously mentioned, if in an LEDC would not have been able to be built, and many people would die due to the lack of materials and expertise needed.
Furthermore many MEDCs have much higher level of resources that can be used on projects such as groynes, but also have the systems in place to ensure that if the area did become flooded or hit by a major storm surge, then they would be able to evacuate quickly and efficiently as many systems would be telling people in authority that a surge is likely to happen. To measure how successful the management schemes have been the effectiveness, the economy and the sustainability of the area can all be taken into account.
But firstly the decisions on the types of management must be correct, and by understanding natural systems and the ways people interact with the coast then there should be no reason why the systems in place are not effective, improve or sustain the economy and preserve the coastline. However planners must now think about changes in sea level and therefore must plan ahead as part of future management schemes to ensure that areas that are protected well today, do not become damaged or destroyed tomorrow.