Coastlines display enormous diversity. This is due to the variety and complexity of the factors influencing coastal morphology. In very general Davisian terms, any shoreline is a product of “structure, stage and process”. In other words, in analysing any shoreline, one must take into account structural factors such as the arrangement of different rock types and their resistance to wave attack and solution, as well as other geological considerations such as the angle of dip and pattern of bedding and jointing of sedimentary strata, The form of any shoreline is also a product of its age and the stage reached in its evolution; that is to say, one must take into account former geological processes and earlier changes of climate and sea-level which may have produced particular features of the present coastline.
Finally, the contemporary processes of coastal erosion and deposition operating on the shoreline are obviously important in determining its form, as are various other physical, chemical and biological processes operating above the tidal zone, together with human activity which is a rather specialized but important cause of coastal change. The multiplicity of factors involved and their local variations result in a wide variety of coastal landforms. Thus, “even within the small compass of Britain, one can contrast sinuous inlets of the South-West, the great sea lochs of Scotland, the low glacial coastline of East Anglia, the marshes of the Thames Estuary and the imposing chalk and limestone cliffs of the south coast” (Goudie, 1993).
It has frequently been argued that systems of classifications are simply aids to description and understanding. By reducing large bodies of information down to a relatively small number of categories, order is imposed on apparent chaos, complexity is reduced to relative simplicity, and description and analysis are thereby facilitated. For these reasons, geomorphologists have long been interested in reducing the variety and complexity of coastal landforms to a relatively small number of distinctive types. C.A.M. King (1980) has suggested that systems of coastal classification are of two types, descriptive and genetic, and argues that the genetic type is preferred, as it is important to know something of the origin of present coasts. She has also suggested that systems of coastal classification ought to take three factors into account; first, the form of the land surface against which the sea is resting; secondly, the direction of the long-term movement of sea-level relative to the land; thirdly, the modifying effects of contemporary marine processes.
Probably the earliest system of coastal classification was that proposed by E. Suess in his book “The Face of the Earth” (1888). This was based on the form of the land surface against which the sea is resting, and simply divided the world’s shorelines into Atlantic and Pacific types. In the former, structural trends are supposed to run at right angles to the coastline, while in the latter, structural trends are supposed to run parallel to the coast. Such a scheme is obviously very generalised and of no value for application to small areas. A less generalised system of classification was that proposed by the American geomorphologist, D.W. Johnson, in his book, “Shoreline Processes and Shoreline Development” (1919). This was based on the second of the factors mentioned by C.A.M. King (1980); namely, the movement of sea-level relative to the land. Thus, Johnson identified four main categories of coastline: submerged coasts, emergent coasts, neutral coasts, and compound coasts. These main categories are then sub-divided where appropriate (Figure 1).
1) Submerged Coasts
a) Ria coasts
b) Fjord coasts
2) Emergent Coasts
3) Neutral Coasts
a) Delta coasts
b) Alluvial plain coasts
c) Volcanic coasts
d) Coral reef coasts
e) Fault-line coasts
4) Compound Coasts (any combination of the above types) e.g. Ria coast with fronting offshore bars (considered by Johnson to be evidence of a coast which had first undergone submergence followed by emergence).
Figure 1. D.W. Johnson’s System of Coastal Classification
Johnson’s system of classification was criticised for its inadequate treatment of emergent coasts. In this group Johnson only recognised coasts with a broad flat coastal plain, such as that of the Eastern United States, and made no reference to steep emergent coasts of the type found in Western Scotland. It has also been suggested that another problem with Johnson’s scheme is that, if strictly applied, virtually all coasts are of the compound type found in Western Scotland. It has also been suggested that another problem with Johnson’s scheme is that, if strictly applied, virtually all coasts are of the compound type. That is to say, at some time in their history, almost all coasts will have been affected by both positive and negative movements of base level.
Another approach is that of F.P. Shepard whose “Revised Classification of Marine Shorelines” (1945) placed greater emphasis on contemporary shoreline processes rather that the evidence of former emergence or submergence. Thus, Shepard makes a broad distinction between Primary or Youthful Coasts shaped primarily by non-marine processes, and Secondary or Mature Coasts shaped primarily by marine processes (Figure 2).
1) Primary or Youthful Coast (shaped primarily by non-marine processes)
a) Shaped by terrestrial erosion and then drowned
e.g. Ria coast, Dalmatian coast, fjord coast, etc.
b) Shaped by terrestrial deposition
e.g. Delta coast, dune coast, mangrove coast, etc.
c) Shaped by volcanic activity
e.g. Coast of volcanic deposition, volcanic explosion coast.
d) Shaped by diastrophism
e.g. Fault scarp coast, fold mountain coast
2) Secondary or Mature Coast (Shaped primarily by Marine processes)
a) Shaped by marine erosion
e.g. Coasts made more regular by erosion, coasts made less regular by erosion.
b) Shaped by marine deposition
e.g. Sand spits, cuspate forelands, barrier reef coasts, etc.
Figure 2. F.P. Shepard’s System for Coastal Classification
Shepard’s scheme has been criticised for failing to include a category for emergent coasts. Another problem is that of knowing when a coast moves from the Primary to the Secondary category. Often it is no easy matter to assess whether a particular section of coast is predominantly a product of marine or non-marine processes. In any case, coasts are subject to short-term changes, and a period of erosion and recession may be followed by one of deposition and advance.
In order to deal with these problems and the limitations of earlier schemes of classification, a more sophisticated proposal was made by H. Valentin in “Die Kuste Der Erde” (1952). His system was based on the contemporary advance or retreat of the coast. Each of these two main categories was then subdivided according to the causes of advance (i.e. emergence or deposition) and the causes of retreat (i.e. submergence or erosion).
This brief review of a selection of schemes of coastal classification has served to highlight some of the problems involved. Early proposals tended to be descriptive, inflexible and incomplete. In contrast, Valentin’s scheme emphasises the dynamic nature of coastlines, and provided data are available for rates of change, allows for a more precise and scientific classification. It is probably the most useful system of classification proposed to date. Before moving onto to some of the specifics of coastal defence in the UK it is useful at this conjunction to examine the institutions and policies which have been, and still are, tackling the complexities surrounding coastal management in terms of coastal defence.
Land Drainage is defined under the Water Resources Act 1991 (amended by the Environment Agency Act 1995) to include defence against water, warping, irrigation, and the continuation of any other practice that involves the management of the level of water in a watercourse (Clark, 1996). The term has evolved alongside the divisions that manage its policy and operations. The Land Drainage Branch of the Board of Agriculture was responsible for land drainage and sea defence works from 1889, when it assumed control of the work carried out by the Land Commission of England that had been established under the Land Drainage Act 1861.
The Land Drainage Act 1926 re-allocated certain powers in relation to land drainage from the Ministry of Agriculture and Fisheries, to county councils and county boroughs. The Land Drainage Act 1930 unified the various river catchment boards and drainage boards concerned with land drainage and sea defence, established a Land Drainage code of law, and increased funding available to the land drainage authorities. The Commercial, Land Drainage and Rural Life Division of the Ministry changed to become the Land Drainage, Publicity and Rural Life Division in 1935, and then the Land Drainage Division in 1938. This division focused solely on land drainage and sea defence issues, before it expanded to become the Land Drainage and Water Supply Division in 1944, and again in 1959, when it became the Land Drainage, Water Supply and Machinery Division.
Responsibility for flood protection and land drainage continued to shift, and in 1984 was held by the Land Drainage Division; in 1986 by the Flood Defence and Land Sales Division; and in 1989 by the Flood Defence Division. A Flood and Coastal Defence Division was established in 1993 within the Environment Policy Group of MAFF’s Countryside, Marine Environment and Fisheries Directorate. By 1997, as a result of reorganisation within MAFF, it had been transferred to the Regional Services and Defence Group of the Agricultural, Crops and Commodities Directorate. Around 1995 it absorbed an Emergency Unit dealing with emergency planning in relation to national food supplies, and became known as Flood and Coastal Defence with Emergencies Division (FCDE) (Defra, 2005).
Until MAFF’s replacement by DEFRA in 2001 (the Department for Environment, Food and Rural Affairs was created in June 2001 from the then Ministry of Agriculture, Fisheries and Food (MAFF) and from the environmental and countryside business areas of the then Department of the Environment, Transport and the Regions (DETR)), FCDE ran MAFF’s flood and coastal defence programme. The National Assembly for Wales (exercising powers formerly held by the Welsh Office) worked with MAFF to monitor the progress made towards reaching policy objectives. These aimed to minimise flooding and coastal erosion in England and Wales, and to reduce the associated risks to people and the developed and natural environment.