South Thames Estuary and Marshes are nationally scarce plants on dykes, and the diverse invertebra include nationally rare beetles, flies and true bugs. 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
Columbia River Estuary Columbia River Estuary The Columbia River Estuary is an estuary and a bay on the Oregon–Washington border and the Pacific Coast of the United States. If the Columbia River Estuary is defined by the region that experiences ocean tides, then the estuary extends up the Columbia River to Bonneville Dam and up the Willamette River to Willamette Falls (south of Portland at Oregon City, Oregon). If the estuary is defined by the geographic land form or by the inland extent of salinity, then the estuary extends only as far as Welch Island. The downstream end of the estuary is the