River Wandle

A short headwater – the Caterham Bourne – is partially in Surrey, the historic county of the river's catchment. Tributaries of the Wandle include Carshalton Ponds and Norbury Brook. The Wandle Trail follows the course of the river from Croydon to Wandsworth. The name is thought to derive from a back-formation of Wandsworth (Old English: Wendelesorde meaning Wendle's Enclosure). In the pleistocene before the carving of the Mole Gap, water lapped the north of the area between the North Downs and Greensand Hills known as the Vale of Holmesdale taking the Caterham or Coulsdon Bourne routes, to form the much less deep Merstham Gap, a wind gap. In more recent times, precipitation on the local central, small section of the long escarpment percolates through the chalk and reappears as springs in central Croydon, Beddington, and Carshalton. The occasional stream, known as the Bourne, which runs through the Caterham valley (and Smitham Bottom in Coulsdon) is a source of the River Wandle but only surfaces after heavy rainfall. A series of ditches and culverts carries the water from Purley to Croydon.