Greater London is located in the southeast of England, 50 km west of the Thames Estuary and extends over an area of 1,579 km², which puts the city at the thirty- seventh of the widest areas. The altitude varies from sea level to 245 m in Biggin Hill, south of the city.
The river, which crosses the city from west to east, has had a major influence on the development of the city. London was originally founded on the north bank of the Thames, and has arranged for several centuries only one bridge, London Bridge. The main focus of the city is accordingly stationed on the bank of the Thames, up to the construction, in the eighteenth century, of a series of other bridges. The city was then extended in all directions, this expansion is hindered by any natural obstacle in a country almost devoid of relief, with the exception of a few hills (Parliament Hill, Primrose Hill).
The Thames was once wider and shallower than today. The river banks were heavily equipped, most tributaries were diverted and are now underground, sometimes transformed into sewers (eg the Fleet River which is named after Fleet Street, the old street of journalists). The Thames is subject to the tide and London is widely flood. Flood threats also increase over time given the steady rise in the water level at high tide and slow inclination of Britain (bearing north, lower in the south) caused by a isostatic rebound phenomenon. Dam, the Thames Barrier, was built across the Thames at Woolwich in 1970, to address this threat. In 2005 however, it was suggested the construction of a dam fifteen kilometers long lower downstream to avert future risks of flooding.
Translated from Wikipedia .