Coastal wet grassland - definition

What distinguishes coastal wet grassland from lowland wet grassland which happens to lie near the sea, is the nature of the soil and/or the influence of saline water. Their origins are usually the result of drainage of swamps and other low-lying wetlands derived from marine sediments around the margins of tidal embayments. These enclosures may date back to 'Roman Times' as in the case of the Wash (the Fenland Basin) and Romney Marsh (c200AD) in Kent.

Precise definitions are difficult because the marine sediments may be overlain by river alluvium as relative sea level movements alter the landward limits of tidal influence. Although now largely used for intensive agriculture, the fenland basin around the Wash, is derived from the enclosure of freshwater and brackish swamps and salt marshes. The Ouse Washes in Cambridgeshire lie adjacent to the canalised river Ouse which stretches many miles inland and is influenced by tidal water along much of its length. The extent of saline water intrusion today is limited, and only occurs in the lowest tidal reaches of the river. Pevensey Levels on the south coast in East Sussex was formed on the site of a former inlet (Steers 1969) but today has no saline influence. Other coastal wet grasslands may receive limited saline water intrusion from seepage zones through coastal barriers or as a result of overtopping by the sea. There will be gradations from brackish to freshwater, especially in the drainage ditches.

References

Steers, J.A. 1969. The Coastline of England and Wales, 2nd Edition. Cambridge University Press, 762 pp.