Restoration and management of coastal wetlands

Coastal wetlands (or tidal marshes) are saltwater and brackish water wetlands located in coastal areas. They provide natural defence against coastal flooding and storm surges by wave energy dissipation and erosion reduction, helping to stabilise shore sediments. In some locations (such as the Schedlt Estuary), coastal wetlands can be used to absorb storm surge waters, attenuating flooding. Coastal wetlands also are important habitats, for example providing a nursery function for fish and shellfish and a variety of services to birdlife and can contribute to water purification. The restoration of coastal wetlands and managed realignment are increasingly considered as measures for adaptation:<ul><li>Restoration of coastal wetlands: wetland restoration aims at re-establishing natural functions of wetlands that have been degraded by natural and human activities. One method is to add sediment to raise land above the water level and allow wetland plants to colonise, or to modify erosion processes that are degrading wetland areas. Alternatively, rewetting of drained coastal wetlands by blocking drains and reducing groundwater extraction is an effective restoration technique for brackish wetlands. A more resource intensive technique is the transplantation of vegetation from healthy marshes or specialised nurseries (e.g. LIFE Barene project).</li><li>Managed realignment and ‘depolderisation’: setting back the line of hard flood defences to a new line, further inland and/or on rising ground to recreate intertidal habitats between the old and the new defence. The wetland will serve as a buffer zone where storm surges will be attenuated. Depolderisation refers to returning reclaimed land (a “polder” in Dutch) to the sea. Managed realignment can involve deliberate breaching or complete removal of a coastal defence such as a dike, or the relocation of defences further inland. For example, in the Hedwige-Prosperpolder project in the Scheldt Estuary (Belgium and Netherlands), outer dikes are being removed to turn reclaimed land into wetlands, while inland dikes are being strengthened.</li></ul>