River Ravensbourne

The Ravensbourne is one of many rivers which flow into the Thames. Its catchment area is SouthEast of the Thames. 
The Ravensbourne source rises in Keston, four miles south of Bromley town centre. The river collects various sub-tributaries, such as the River Quaggy. It empties into the Thames at Deptford.
These river names are quite ancient. The Ravensbourne, for example, is noted in the Domesday Book.
In the centre of London the rivers are hidden under the "made" road surfaces (under Fleet Street, for example). In the suburbs the tributaries can usually be seen. The tributaries influenced the positioning of roadways and housing during the 19th century.
Of course, before the 19th century London was a much smaller city. Most of the tributaries to the Ravensbourne ran through country districts then.