The Wash is a large, square-mouthed, shallow estuary on the eastern coast of England, surrounded by extensive areas of tidal sandflats, some mudflats, and salt marshes. It is fed by four main rivers: the Great Ouse, Nene, Welland, and Witham.
The sandflats of the Wash range from extensive fine sands to drying banks of coarse sand and are home to large communities of bivalve mollusks, crustaceans, and polychaete worms. The extensive salt marshes comprise the largest single area of this habitat in Britain and are growing in extent. The main plant species making up these salt marshes, which are traditionally used as grazing lands by farmers, are cordgrass and glasswort in roughly equal amounts.
The Wash is one of the most important sites in the UK for wild birds, its sheltered tidal flats providing a vast feeding ground for migrating birds, such as geese, ducks, and waders. These come to spend the winter in the Wash in huge numbers, with an average total of about 300,000 birds, from as far away as Greenland and Siberia. In addition, the Wash is an important breeding area for common terns and a feeding area for marsh harriers. It has been declared a Special Protection Area (SPA) under EU law.
In 2000, parts of the artificial coastal defenses on the western side of the Wash were deliberately breached to increase the area of salt marsh in the region. This has taken pressure off other nearby sea defenses, because the newly establishing area of salt marsh soaks up wave energy, acting as a natural sea defense. This is a relatively novel approach to coastal management that employs “soft engineering” techniques to defend against the erosive power of the sea. It also has the added environmental advantage of providing additional habitat for wildlife.