Coastal Defences
MAFF (2000) confirmed that the government guidelines for the appraisal of coastal defence schemes in the UK do not require that non-market amenity benefits are to be considered. However, new options in the coastal defence management would provide opportunities for the integration of coastal defence with amenity provision. This will tackle the findings of a choice study that will evaluate the amenity benefit of alternative coastal defence system that are currently being considered. It is important that these benefits are for all the local community members and the industries as well. MAFF (2001) commented that the management and guidelines for the appraisal of coastal defence projects should be amended to incorporate amenity benefits. The integration of the planning and management of the coastal land and associated inshore waters are the strategic and comprehensive attempts at the issues affecting the countrys coastline. Since coastal defence has been unplanned in the past 10 years, a more strategic approach had been taken through the Shoreline Management Plan and the Coastal Defence Strategies.
The coastline of East England is comprised of soft erodible sedimentary geology. The coastline is diverse with areas of low-lying land that are very susceptible to flooding. Foreshore materials are variable which includes sand, gravel mud and bedrock. Brooke, (2002) commented that the risk to loss of land, property and life is high, especially in the eastern part of England. David (2007) cleared the issue regarding the systematic region-wide assessment of the coastal risks has made a risk base regional monitoring framework to be in the development process.
Bathymetric Map of East England
This is a bathymetric map or a topographic map of East, South East England. The red colour represents the coastal land. The colour blue represents the sea bed or the earths surface. The deviation of the colour blue means that the darker the colour becomes, the deeper the water is. Thus, this also represents the topography of the earths surface.
A low lying coastal area located at the mouth of an estuary near an industrialized and urban area, consists of a low cliffdune and soft eroding sedimentary materials. There is long shore drift moving fine medium sand along the coast from north to south. The sand movement maintains beaches of the North and South of the area. This will help to protect the upper shore areas from erosion. Due to the sea level rise and cliff erosion, the local municipality and industries demanded for coastal protection in order to protect their dwellings, industries and their major roads that passes along the coast.
Shoreline Management Coastal Defence (2004) stated that there are several planning options to consider for the protection of the coastline. Holding the line would be one. Holding the line is a coastline protection scheme that involves the construction of a seawall. Houses use the seawall as sea defence. The overflow of sea water is being prevented by the seawall when water flows over the beach to the land lying behind. Overflow usually occurs during high tides and intense storms. Seawall prevented erosion problems and reduce the risk of overflow. Seawalls have also a negative scenic impact on the beach as much as reducing the views of the sea from peoples homes, but if a walkway is to be created on top of the seawall, there would be some recreational benefit of it. Another option would be advancing the line. This method is the building of a new defence seaward of the existing defence line. Retreating the line is the method of managed realignment, allowing retreat of the shoreline thus with management control or limit movement. The do nothing approach is the decision of not investing anything in providing or maintaining the defences.
Coastal defence issues and strategies (2009) claimed that the techniques to be applied in coastal management which involves the cost benefit approach to hard engineering and soft engineering are the following. The construction of groynes is viable. Groynes are wooden, concrete, rock barriers or walls built perpendicular to the sea. Groynes creates a wider and plentiful beach, thus protecting the coast because the sand would filter and absorb the wave energy. Groynes require a very minimal maintenance, and it is one of the most common coastal defence structures. The construction of seawall is another option. Seawalls reflect the energy of waves back to the sea. It destroys the incident energy that results to a reduced turbulence. Seawalls are ordinarily made of concrete rocks which are built at the back of a beach or at the base of a cliff. The use of seawalls is a one of the traditional methods used in coastal management. Revetments are wooden slanted upright blockades. These are built on the coast parallel to the sea towards the back of the beach. This is used to protect a cliff or a settlement behind. Timber is the usual material used with rock infill. Revetments dissipate and absorb the energy when waves break against revetments. Revetment traps the materials behind barriers that protect the base of the cliff. Revetments could be watertight, and covers the slope completely, allowing water to filter through after the dissipation of the wave energy. According to the Environmental Agency (2010), major maintenance is required within a moderate time of being built. This is determined by the quality of the materials used for its construction. The rock armour, known as riprap, is a pile of large rocks at the foot of dunes or cliffs with native stones from the beach. Generally, ripraps are constructed to areas that are prone to erosion to absorb the wave energy and hold beach materials. Using riprap is effective but it is not popular because of the fact that it does not look good on the coastline and reduces the recreational value of the beach. Gabions are boulders and rocks wired into a mesh cage and placed in front of areas that are vulnerable to heavy erosions. When the seawater strikes on the gabion, the water is drained, leaving sediments. The boulders and rocks absorb wave energy. The disadvantages are that they get worn out very quickly and are not attractive.
Hence, gabions are not a good source of coastal management. Offshore breakwaters are concrete blocks and boulders, sunk offshore to redirect waves and filter energy waves and tides. The waves break offshore and reduce their erosive power. This activity leads to wider beaches, in turn, will absorb the reduced wave energy to protect cliff and settlements behind. Cliff stabilization is used to help prevent landslides and other natural disasters. This can be done through the drainage of excess rainwater, terracing or planting and wiring in order to hold cliffs in place. Entrance training walls are rock or concrete walls which are built to constrain a creek or a river that discharges across a sandy coastline.
These walls help in stabilizing and deepening of the channel that benefits navigation, flood management, river erosion and quality of water. Due to interruption of longshore drift, this can cause coastal erosion. The installation of a sand bypassing system to pump sand under and around the entrance training wall is to be done. The cost of construction is very expensive. Floodgates are storm barriers which were introduced after the North Sea Flood of 1953. This is a prophylactic method to prevent damage from storm surges. They are habitually open, and they allow free passage, but close when the land is under a threat of a storm surge. One of the most common soft engineering techniques of coastal defence management scheme is beach nourishment or replenishment. The method is importing alien sand off the beach and piling it on top of the existing sand. This method requires constant maintenance. The cost of construction is not expensive, but requires control structures and ongoing management and minor works. Sand dunes stabilization needs vegetation that can be used to encourage the growth of dunes needed to trap and establish blown sand. As of today, the research will have to be carried out, because the rough estimate is not yet established. The beach drainage or beach dewatering lowers the water table beneath the beach face. A lower water table facilitates the deposition by the reduction of the flow velocity during the backwash and prolonged laminar flow. A very useful effect of the system is that the collected seawater is very pure due to the effect of the sand filtration. It may be used to oxygenate stagnant inland lagoons, desalination plants, land-based aquaculture, aquariums or seawater swimming pools. The cost of installation and operations of the offshore protection differs. The costs that are associated with a drainage system of a beach are lower that the hard engineered structures. If compared to beach nourishment, the economics of building a beach, drainage is considered.
Evidence has a clear demonstration that there are significant differences in the value of amenity benefit that is associated with the alternative types of coastal defence options. The values should not be disregarded in the coastal defence projects which is the current situation in East of England. Flood and Coastal Defence (2008), confirmed that recommendations are made that Defra must modify its guidance for the appraisal for coastal defence projects in order to include a requirement to consider the non-market benefits of the alternative option. These non-market benefits should include the amenity benefits to local residents, together with the benefits by the present and potential visitorstourists especially in locations where tourism is a significant contributor to a local economy. The amenity benefits in the coastal defence will help to ensure the best value for money that is going to be attained.
In consideration of the optimal solution of the coastal defence in Eastern England, the management solutions that were carried out should be environmentally sustainable. A long term strategic view is needed, if a shoreline management plan is to lead a sustainable coastal defence. In order to achieve environmental sustainability, the minimal use of finite natural resources and environment as a whole is encouraged. There must be an understanding of the importance of appropriate environmental practices and using the best practice to sustain and maintain the present environment and further enhance the preservation of the environment. The coastal area can be technologically feasible in many ways. Technological developments are likely to happen in the future. Being adjacent to an industrialized and urban area, we can foresee the growth towards automation and robotics. Thus, the coastal defence system must be feasible to possible technological growth or development. As the technology improves its growth, the desire for the preservation of the assets in the coastal zone had resulted in the widespread installation of feasible coastal modern technologies. A very good example of this is the installation of optic communications. Measures for economical viability are not to be neglected in the process. As tourism grows in the area, the economic situation improves. The creation of more local jobs follows. The whole task of planning, designing, building the management of coastal defences is cost effective. Shoreline Management (2006), clarified the matter that based from the contributions of experienced coastal defence specialists, the management solution is economically viable. We can absolutely confirm that the measure taken is socially desirable or tolerable because of the effectiveness of the coast management scheme. Monitoring provides the information to let you know whether the management solution is socially desirable. The East Coasts of England are very suitable for surfing. The beach composition, which comprises of the surface materials such as silt, mud, sand, gravel, boulders, rocks and boulders or the combination of both, and the gradual slope of the sea bed along the surfing area, add to the effectiveness to the protection of the coasts, making the waves suitable for surfing, swimming and other family activities on the beaches. These factors lead the coasts to be legally permissible. From the stated factors, it is likely that the coastal area is administratively achievable, and lastly, it is politically expedient.
Today, we know that the problem in coastal management is getting more complicated. Some of us believe that we must not build hard defences, and that the environment should be left alone. Policy of managed retreatment would only result in more lands being lost to the sea since dunes and marshland, eventually forming natural barrier. We need to look at a new range of options in our shoreline management. The present government is committed to defend where it is sustainable and affordable to do. Let us not assume that building the coastline defences are the best options. Neither can we assume these defences will completely remove the risks. We need to look at the other ways that the coastline communities can cope with the risks. We can work on effective town planning to ensure that the new developments will not increase flood and coastal erosion. Household members and business along the coasts can protect themselves against flooding with their property level protection measures. Entertaining the different methods of land management will surely slow down the rate of rainwater to travel across land, and into watercourses in order to reduce the incidence of flooding. Using the natural features such as sand dunes, saltmarshes and flood plain storage areas can help reduce the potential of flooding and coastal erosion. Using different approaches in supporting communities to adapt to the rapid changing of the coastlines is to be considered.
Finally, the Shoreline Management Plan (2009) insisted that the proper education of the people living along the coast for possible flooding is very important. Defra is funding the environmental agency to advise the planning authorities on proposals developments to ensure that flood risk is properly taken into account. In addition, Mangor,(2001) agreed to the fact that consultation have been extended to the environmental agency, and made a standing plan so that if the planning authority proposes to grant permission for major development, the coastal defence will likely to be advancing to the properly coordinated means of protection.
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