THE ROLE OF POLLUTANTS AND SEDIMENTARY PROCESSES IN FLOOD DEFENSE - A CASE-STUDY - SALT MARSHES OF THE ESSEX COAST, UK

Salt marshes are of immense environmental and economic importance, particularly for flood defence since their presence reduces the impact of waves at the shore line. Salt marsh habitats along the UK Essex coastline are, however, in decline which is putting increasing pressure upon coastal defences, escalating both the consturction and maintenance costs of flood protection. Pollution has been cited as a potential cause for the decline of these fragile ecosystems. Heavy metals, herbicides, insecticides and organochlorine compounds have been extensively used in industry and agriculture since the 1930s. The presence of such compounds within the salt marsh environment could potentially have a deleterious effect upon salt marsh vegetation and invertebrates, ultimately leading to marsh erosion. A case study of salt marsh and mud flat environments in Essex defines the magnitude, spatial and temporal distribution of contaminants within these inter-tidal sediments. This seeks to demonstrate how an appreciation of sediment processes and pollutant input pathways, transportation routes and contaminant sinks, may aid the management of flood defences. Results indicate widespread low level contamination by a range of anthropogenic contaminants from historical as well as contemporary sources. The magnitude, distribution and availability of contaminants is dependent upon a number of inter-related biological, chemical and physical processes. These interrelationships demonstrate the need to consider different disciplines and management needs to create integrated approaches to coastal management. By taking a strategic view of the coastline on a multi-disciplinary basis more sustainable management solutions will be generated in the future.