combined sewer overflows (CSOs), averaging per day or 106,849 tonnes per day. These CSOs can cause the deaths of marine life and health hazards for river users. The Thames Tideway Scheme, under construction, aims to divert most of the overflow from sewers into a tunnel under the river. Thames Estuary The Thames Estuary is bordered by the coast and the low-lying lands upstream between the mouth of the River Stour on the Essex/Suffolk border and The Swale in north Kent. It is now usually designated the Greater Thames Estuary and is one of the largest inlets on the coast of Great Britain. The water can rise by 4 metres moving at a speed of 8 miles per hour. The estuary extends into London near Tower Bridge, and can be divided into the Outer Estuary up to the Swale at the west end of the Isle of Sheppey, and the Inner Estuary, designated the Thames Gateway above this point. The shore of the Outer Estuary consists of saltmarshes and mudflats, but there are man-made embankments along much of the route. Behind these, the land is cultivated or used for grazing. Parts of the Outer Estuary are on a major shipping route. Thames Gateway The Gateway is some long, stretching from the Isle of Sheppey to Westferry in Tower Hamlets. Its boundary was drawn to capture the riverside strip that formerly hosted many land extensive industries, serving London and the South East. The decline of these industries has left a legacy of large scale dereliction and contaminated land, but an opportunity for major redevelopment. The area includes the London Docklands, Millennium Dome, London Riverside and Thames Barrier. Major crossings Dartford Crossing including two Dartford Tunnels (1963 and 1980) and the cable-stayed Queen Elizabeth II Bridge (1991) Blackwall Tunnels (Alexander Binnie, 1897; second bore 1967) Jubilee line and Docklands Light Railway tunnels Greenwich foot tunnel (Alexander Binnie, 1902) Rotherhithe Tunnel (Maurice Fitzmaurice, 1908) Tributaries Pitsea Creek, Mar Dyke and River Ingrebourne River Rom (lower reaches known as the Beam) and River Dart River Roding (tidal reach known as 'Barking Creek') River Lea or Lee (tidal reach known as 'Bow Creek') Ravensbourne (tidal reach known as 'Deptford Creek') Islands and peninsulas Isle of Grain— actually a peninsula Two Tree Island Canvey Island Lower Horse Island Frog Island, Rainham Isle of Dogs — actually a peninsula Pool of London The Pool of London is divided