Streamlining Site Selection For Managed Realignment

摘要

Managed realignment, the deliberate breaching of flood defences to allow the formation of new intertidal habitat, has received increasing attention in the UK over recent years. Managed realignment has become a necessary shoreline management technique for two reasons; firstly as a means of providing economic and sustainable flood defences, and secondly because European law (in the form of the Habitats Directive) and the Biodiversity Convention require the UK to maintain the health and extent of a number of intertidal habitat types in the country and ensure that equivalent compensatory habitat is provided to offset loss or damage to these habitats designated under the Directive. However, the task of finding land that is suitable for creating intertidal habitats such as salt marsh is not an easy one. Salt marshes have a number of physical and biological requirements that must be fulfilled before they will form, and these must be taken into consideration when looking for available sites. Furthermore, much of the land found in the coastal zone already has an existing nature conservation value, which can create conflicts of conservation interest when creating new habitats or carrying out shoreline management activities. Finally, private landowners are often unwilling to sell their land, which has resulted in a general shortage of suitable land available for managed realignment in the coastal zone. There is currently no standardised procedure for identifying sites for managed realignment, which means that sites are identified on an ad hoc basis. Coupled with the numerous issues that must be considered when finding suitable sites, the time required for compensatory site identification can cause extensive delays to essential flood defence schemes located in environmentally sensitive areas. A means of streamlining the site identification process with a view to reducing these delays has been developed by creating an analytical tool, in the form of a matrix, to assess site suitability. This paper discusses this tool, which has proved successful in bringing together the key elements involved in site selection, ranging across technical, environmental, sustainability, statutory and legal, economic, social and recreational issues. Each site is scored for suitability in all of these categories, which allows direct comparisons to be made between different sites, so they can then be ranked and the most suitable one chosen. The matrix was developed and then tested in site identification for a coastal defence scheme in central southern England. It was concluded that the matrix is a successful means of identifying sites and eliminating those which are unsuitable for realignment at an early stage. The process also allows for wider geographical coverage and therefore facilitates a more strategic approach to site selection. The matrix has the potential to be adapted to other processes such as strategic planning for shoreline management.