[2] At Bossington a shingle beach, through which flows the River Horner, rising sea levels in the 1990s caused the creation of salt marshes and lagoons developed in the area behind the boulder bank.

[3][4] This site comprises a shingle ridge and associated saltmarsh hinterland extending for a distance of approximately 4 kilometres along the west Somerset coast, immediately north of Porlock village.

The type of geomorphological development seen at Porlock has been noted for coastal shingle systems elsewhere (e.g. west coast of Newfoundland, Canada).

Although other UK systems probably developed and are developing in a similar manner, Porlock provides the only fully documented example of a nationally important coastal geomorphological system which has undergone catastrophic failure and subsequent evolution following sediment inhibition and a great storm in October 1996 which caused the single ridge to be breached allowing the marsh to be inundated with salt water at New Works (the drainage facilities for the previous managed fresh water marsh).

[2] A large part of this site is lower saltmarsh dominated by common glasswort (Salicornia europaea andannual) and sea-blite (Suaeda maritima).