The Severn Estuary SSSI original designation involves the then counties of Somerset, Avon and Gloucestershire in England, and Gwent and South Glamorgan in Wales. The Severn Estuary SSSI designation overlaps individual site designations for separate sites in Avon (Spring Cove Cliffs, Middle Hope, Portishead Pier to Black Nore, Aust Cliff), Gloucestershire (Purton Passage) and South Glamorgan (Penarth Coast). The 1976 designation includes two sites previously notified in 1952 (Brean Down and Uphill Cliff). The SSSI forms the major part of a larger area which includes the Taf/Ely Estuary and Bridgwater Bay (as well as the Upper Severn Estuary)