South Thames Estuary and Marshes South Thames Estuary and Marshes South Thames Estuary and Marshes is a biological Site of Special Scientific Interest which stretches between Gravesend and the mouth of the River Medway in Kent. Part of it is a Nature Conservation Review site, Grade I, and part is a Royal Society for the Protection of Birds nature reserve. It is part of the Thames Estuary and Marshes Ramsar internationally important wetland site and Special Protection Area under the European Union Directive on the Conservation of Wild Birds. Over 20,000 waterfowl use this site, and some species are present in internationally important numbers. There
River Sheppey where it joins Whites River and then the River Brue near Westhay. The water quality is generally good; however, there have been some discharges from sewage treatment works in the area that can contribute to nutrient levels in rivers. Signs of nutrient enrichment are noticeable at times of low flow and the ecology of the Sheppey is adversely affected in its upper reaches. It would appear that the Sheppey was only so called in the late 19th century. Prior to then, if it was called anything, it was probably Doulting Water or the River Brae. The Sheppey has been used