Grazing • Access and amenity • Pollution • Coastal defence maintenance • Alternative uses

Coastal defence maintenance

The implications of continuing to maintain the current line of flood defences in estuary systems has already been considered in relation to the discussion of coastal squeeze. In those areas where sea level is rising relative to the land, it would appear that a loss of saltmarsh is inevitable. The losses experienced in Essex and north Kent provide an indication of what might happen elsewhere, particularly if the current scenarios associated with an increase in the rate of sea level rise due to global warming are realised.

The extent to which the maintenance of defences (i.e. holding the line) reduces the ability of the tidal zone to accommodate changes in sea level, the influence of storms and alterations in the tidal regime or the configuration of the estuary channels is potentially significant. The management response to these changes requires both consideration of the need to protect the saltmarsh and to maintain the flood defences in each case and each location. These issues are considered in a recent report published by CIRIA. The report, entitled ‘Coastal and estuarine managed realignment - design issues’ (Leggett et al., 2004), provides guidance on when ‘holding the line’ may be a viable economic or environmental option and when ‘retreating’ would better meet management objectives (see Managed Realignment for more information).

The direct effect of works to maintain sea walls can have implications for saltmarsh habitat both during construction and operational activities. Construction works can have an impact on the habitat due to a requirement for access across the marsh or works to the toe of the sea wall. Certain species that may be rarely distributed or sensitive to damage could be particularly at risk. Furthermore, works that stabilise the eroding edge of a saltmarsh may have long term effects on the development of the marsh which should be considered against the (potentially) short term gains associated with the works.