Description:
For many centuries, man has developed the coastline and its immediate hinterland for hoth commercial and cultural reasons. Flat land adjacent to the sea is in great demand for many purposes, including agriculture, ports, roads and railways, power stations and refineries, and residential properties. In many areas, substantial tracts have been reclaimed from the sea to increase the land available for development. A substantial part of the national economy of the UK, and many other countries, is now generated in the coastal zone.However, the areas of the coastal zone of greatest value, i.e. that on top of low cliffs, reclaimed areas and low-lying coastal plains, are often at greatest risk from the sea. The continuing action of waves and tides, together with the slow increase in global sea level relative to the land, results in the majority of the shorelines around the world suffering recession. Because of this, risks to the developed areas from marine flooding, and erosion of the land itself, increase with time and may be growing faster due to the changing climate. It is widely expected that global warming will cause both acceleration in sea-level rise, and changes in the frequency and intensity of storms, thus altering both wave conditions and tidal surges.For many centuries, the response to these risks has been to resist the action of the sea by the construction of coastal defences, i.e. structures designed to reduce the risks of erosion or flooding. These range from simple earth embankments to sophisticated civil engineering structures such as tidal barrages. The construction of coastal defences is expensive, and carries the risk of substantial damage to the environment. This is often an important consideration because the coastline often also provides very important habitats for a very wide range of flora and fauna, as well as opportunities for tourism, formal and informal recreation.In addition, it can be difficult to design and build a structure that will be both effective and long lasting. This guide aims to introduce the reader to the process of considering and, if appropriate, choosing, designing, building and maintaining coastal defences appropriate to a particular situation.The guide starts with a review of the history of coastal defences in the UK, and of the legal administrative arrangements for their construction. This is followed by a description of the important processes causing changes to the coast, and examples of the commonest types of coastal defences. After this the guide goes on to discuss the information needed to decide whether installing defences is justifiable, and how to choose appropriate types of defence for further consideration. These decisions have to take account of the technical, environmental and economic aspects of any proposed scheme. In the remainder of the report, the issues of detailed design, construction and post-construction activities are explained.Managing the coastline involves many issues, both technical and non-technical, and it is unlikely that any individual coastal engineer will have sufficient depth of knowledge in all of the disciplines required. In addition to civil engineering, expertise will be required in geology and geomorphology, environmental or ecological science, archaeology, risk analysis and project management. There may also need to be an involvement from oceanographers, marine biologists, information technologists, meteorologists, economists and others.A considerable body of knowledge and expertise on coastal defence in the UK, and in many other countries, already exists. Much of the knowledge that has gradually been built up over many years has been set down in reference books and technical papers, but research continues apace with new publications appearing regularly. Even against this background, the problems encountered at each site are often unique, and require a carefully tailored solution requiring experienced specialists to achieve cost effective and technically sound coastal defences. Use of general technical guidance documents is no substitute for specialist expertise and site-specific investigation.