The Thames and its tidal creeks encompass the entire length of the river in London and the tidal limit of its tributaries. In many cases this tidal limit is artificially restricted by the operation of various barriers and weirs.

The River Thames runs 42 miles through Greater London from Hampton in the west to Dartford Creek in the east. For much of its length it is tidal, the tidal influence reaching as far upriver as Teddington Lock. There are several tributaries of the Thames which enter the river within Greater London, a number of which (notably the Wandle, Ravensbourne, Lea, Roding, Darent and Ingrebourne) have tidal creeks.

The Thames in London covers an area of approximately 2400 ha, about 1.5% of London’s surface area. At low tide the river comprises c2050 ha of open water (85% of the river’s surface area), 310 ha of intertidal mud, sand or shingle (13% of the surface area) and 17 ha of saltmarsh (0.5%). The remaining area comprises patches of neutral grassland, woodland and scrub associated with the islands in the Thames, and remains of former river walls that are within the existing flood defence. Several areas of tidal reedbed have developed in recent years, particularly in areas such as Barking Creek and Bow Creek (see Reedbed audit, HA9).

Areas of intertidal habitat occur along the entire length of the tidal Thames, but where the flood defences have particularly restricted the natural extent of the river channel the intertidal habitat is necessarily limited - although still of importance, particularly for fish and invertebrates. The most extensive areas of intertidal habitat occur downstream of Tower Bridge where the flood defences are set further back from the main channel. The areas of intertidal habitat are identified in Table 1 and displayed in the Map.

The flood defences (river walls) on the Thames vary in nature and characterise the different reaches of the river. Upstream of Putney Bridge much of the flood defence is sloping revetment, often vegetated, which softens the river’s edge and riverbank. Between Wandsworth Bridge and the Greenwich Peninsula the river is largely constrained between vertical concrete and sheet metal piled walls (although areas of mud, sands and gravel are exposed at low tide). Downstream of the Greenwich Peninsula, despite much of the flood defence still consisting of vertical concrete walls and sheet-metal piling, it is set further back from the main river channel thus exposing extensive areas of intertidal mud at low tide. An analysis of the composition of the river walls is provided in Table 2.

Management of the Thames rests primarily with two organisations; the Port of London Authority (PLA) and the Environment Agency (EA). The PLA is concerned primarily with navigation, pollution control and land-use planning issues related to the river; the EA has responsibilities covering flood defence, pollution control, fisheries, water quality, environmental protection and nature conservation.