Every year land is both lost and gained in coastal areas due to physical processes, including the action of the sea. Much time and money is spent in an attempt to limit the change, seen as "damage", that occurs. More advanced methods of coastal defence are tested and put into place and research is carried out. Yet coastal management remains as a piece-meal approach, with different areas of coast dealt with using widely varying methods, some of which are the cause of this "damage" further along the coast.
"Coastal defences, by their very nature, disrupt the natural processes operating on the coastline" (www. orth-norfolk. gov. uk) and it is this fundamental fact that should be considered by all those responsible for coastal management. Although this disruption is sometimes intentional, often it is not and thus more coastal defences must be put in place in order to correct the harm done by the original scheme. Conversely, there exists much land that is considered to be valuable in terms of its economic, social and environmental significance. It may seem a waste to simply watch this land being taken by the sea when there are preventative measures that can be employed.
This essay will look at why the coast is protected, from what, and will give some examples of how as well as the advantages and disadvantages of coastal management strategies including taking no action against the work of the sea. The uses of the coastal area are numerous and diverse, making it difficult to prioritise on what should and should not warrant protection. Land that is situated close to the sea is often the location of homes with a high economic value in addition to the obvious emotional attachment of the owners. Historically valuable features such as buildings or monuments are important in terms of heritage and in turn tourism.
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Land that provides an income, i. e. farmland and camping ground is often situated along the coast and due to the natural beauty of coastal areas, attracts tourists as well as being aesthetically appealing for those that live close to it. Another natural feature is, of course, the precious habitats that are contained by the cliffs, and the scientific interest in those habitats. Settlements were originally located close to the sea for the purpose of transport and for many coastal locations, the import and export of both people and goods remains their principal function.
Indeed, it is estimated that around 60 percent of the global population live within 50 km of the sea (Briggs, Smithson, Addison and Atkinson 1997). Consequently all of these activities and uses have strong arguments as to why they justify the time, expense and risk of affecting other locations in a detrimental way, that coastal defence schemes entail. The purpose of this essay is not to evaluate which of these is the most deserving but simply to acknowledge that all of these valuable features can be found in coastal locations and are therefore at risk from erosion by the sea.
The processes that affect the coastline involve the action of the sea against the vulnerable beach and cliffs. Waves attack the coast in two fundamental ways. Firstly waves are formed and their energy increased by a combination of wind, tide and current. The force of this wave action is often enough to cause fractures in the rock and sometimes failures and de-stabilization through the trapping of air. The structure and geology are obviously major contributing factors when the severity of "damage" is considered.
The second way in which the waves attack the coastline is really a strengthening of the first method and this is by the transport of sediments in the water. A wave that is carrying material that it has eroded or that is originally from the seabed has more power to potentially erode. This shoreline abrasion relies on both wave energy as well as a supply of material with which to attack (Summerfield 1991). Another coastal process is weathering which also occurs inland but is exacerbated at the coast due to the very nature of the area. This includes the wetting and drying cycles and also the existence of salt.
Salt weathering has a greater effect on rock that can absorb seawater as this allows the salt to penetrate the rock and so work on its structure as opposed to only the external surfaces. Coastal defences obviously do not directly combat weathering as even if the land behind is protected from the sea, salt is ubiquitous and so will still reach it. So it is this persistent force from which the shoreline is, in some locations, protected. The methods used in this protection vary in construction and purpose but also in their efficiency, with each method exhibiting both positive and negative aspects.
The best defence against erosion... by the sea is a natural wide beach topped off at the inshore end with either high deep sand dunes or a shingle bank" (www. north-norfolk. gov. uk). Unfortunately not every coastal location has this advantage either for natural reasons or where the beach material has been removed for human use, for example building. In the case where there is erosion occurring and shoreline assets are threatened, artificial defences are put into place. One example of a coastal engineering method is the sea wall.
These were widely used in the early stages of coastline management and some modern designs have since emerged which now play a major role in defence from the sea. The sea wall is intended to reflect the wave away from the land behind as opposed to a natural beach which absorbs and dissipates the wave energy. Another form that is frequently seen is the utilization of groynes. Groynes prevent the loss of beach material by creating an obstacle. They also encourage the build-up of sediment by interrupting and thus slowing the inshore tidal current.
Combined, this means that there is a "natural" defence in the form of a more substantial beach in order to dissipate wave energy, consequently less erosion occurs at that particular site (see figure 1). Revetments are another commonly employed type of defence, constructed mainly from wood or concrete. The idea is that a surface sloping towards the beach dissipates wave energy meaning that less energy is available for erosion and also that sediment builds up in front of the revetment (www. north-norfolk. gov. uk). Type of defence Cost per metre (i??) Revetment 500 Seawall 5000 Groyne 1000 There are, of course, many more coastal engineering methods but for the purpose of this essay, only three have been outlined. All methods, however, have their advantages and disadvantages. Management of the coastline in the UK, in terms of erosion, is generally taken as a piece-meal approach. That is to say each area is dealt with almost in isolation, and only relatively recently have the relevant authorities become aware that the interference in one place is likely to have a considerable effect on another, further along the coast.
An example of this is the implementation of groynes. The prevention of material loss and the subsequent build-up of sediment through interruption of the inshore tidal current can, in some cases, starve beaches further along, of the material that is required to maintain size and stability. So although one area is benefiting and a "problem" being solved, other areas can lose out and thus another problem is created. Conversely if groynes are correctly designed, they can work very well and they essentially do exactly what they are designed to.
As many were constructed before it was realised that harm could be caused as well as good, the knock-on effects were not taken into account. Modern groynes are designed to be permeable in order that some sediment may pass through them and reach beaches further along. These have been used successfully on the north Norfolk coast where erosion and its prevention is of great significance. Sea walls work best on large beaches, where the sea only reaches the highest point of the beach during a storm (www. orth-norfolk. gov. uk).
Then, should it happen that high tide and a storm coincide, the land behind the sea wall is protected from flooding and erosion. Sea walls require regular maintenance such as in the case of Ostend in north Norfolk, where annual maintenance is required (see figure 2 for approximate cost of initial building of sea defences). In addition to the costliness, there exists the situation of beach scouring caused by the waves reflected from the sea wall.
This can, over time, lead to the collapse of the wall but also means that valuable sediment is being taken away from the beach - so reducing what little natural defence there was. A controversial approach to coastal management is that of leaving it to nature. This "do nothing" strategy has been adopted in numerous locations on the north Norfolk coast, including the area between Cromer and Overstrand where the present groynes are not being maintained and will eventually fail and be removed (see figure 3). A variation of this "do nothing" policy is the so-called managed retreat.
This is where, again, the existing defences are no longer maintained or their maintenance is limited but in some locations a method of soft engineering is employed for example beach replenishment. The issues surrounding these types of "management" are not as simple as may be first thought. For example the financial benefit arising from either no defence being put in place or no longer maintaining the existing defence seems rather insignificant when the loss of valuable assets is taken into consideration. It is, however, almost completely natural, with material that is eroded form one location being accreted at another.
The natural processes are, in this way, allowed to continue and the lack of interference would eventually ensure that there are no negative consequences at other locations as a result of coastal defence action. Despite this, it must be considered that once action is taken to defend the coast from the erosive power of the sea, it creates an issue as to at what point the management should cease and where. To suddenly no longer protect an area of coast may generate new problems and perhaps more expense. So the proposal of an integrated shoreline management strategy seems appealing.
This is looked at in much depth by Karen Nichols in her paper "Coming to terms with Integrated Coastal Management". Fundamentally, it would involve the linkage of all areas of the coastline in terms of action taken upon them. One possible solution could consist of a review followed by the implementation of a fully integrated coastal defence scheme combined with managed retreat. If this was undertaken on a national scale, with the co-ordination of all resources and authorities, perhaps loss of important assets and further damage in the course of protecting those assets would gradually be reduced to a minimum.
It seems to be that the protection of our coastal locations will remain a much-debated issue, with the needs and wants of people contrasting greatly with the power of the sea's natural activities. It is interesting that the focus of coastal management is to reduce coastal erosion yet it is the erosion of coastal land that supplies the beach with much of its material. As discussed earlier, a natural beach is the best form of shoreline defence..... In conclusion it can be said that coastal protection is essential in certain localities but that it is an integrated management plan that will be most likely to succeed.
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