Canvey Island the 30 hectares known as West Canvey marshes, acquired by the RSPB in 2007, and the Canvey Wick nature reserve. Canvey Wick is a designated Site of Special Scientific Interest (SSSI) at the site of the abandoned and incomplete oil refinery. The foundations of the 100 hectare (0.4 sq mile) site were prepared in the 1970s by laying thousands of tonnes of silt dredged from the Thames; the abandoned and undisturbed area has flourished as a haven for around 1,300 species of wildlife, many of which are endangered or were thought to be extinct; including the shrill carder bee, the
Severn Estuary the line between Lavernock Point and Sand Point is the Bristol Channel, which in turn discharges into the Celtic Sea and the wider Atlantic Ocean. The islands of Steep Holm and Flat Holm are located close to that line, in the middle of the estuary. Sometimes the term "Severn Estuary" is used to include the tidal upstream stretch between Gloucester and Aust. During the highest tides on the upper reaches of this stretch, the rising water is funnelled up the estuary into the Severn bore, a self-reinforcing solitary wave that travels rapidly upstream against the river current. The tidal range