The Falconbrook was a stream that flowed through Balham, Clapham Junction and Battersea where it entered the River Thames.
The Falconbrook, a south west London brook, now underground for its entire length, has been throughout replaced by surface water drains diverting water away from it however its course is used from its source for a convenient depression to form a combined sewer to the Southern Low Level Sewer in the London sewerage system. The source of the Falconbrook is Streatham Hill, with an additional source to the west at Furzedown south of Tooting Bec Common. From its source the Falconbrook flowed west through Balham, then turned north one residential block before Wandsworth Common as it was joined by the Tooting Bec and continues to carve a ravine which is formed by St John's Road and Northcote Road in Battersea Rise. Springs feed the first drain from the foundations of a shops (nos 2–36 Streatham High Road, the A23 road). During their construction, extra access space was built below the basement floors to accommodate the springs when in full spate. The brook flowed (and now sewer flows) along Drewstead Road, past Woodfield Avenue, passed through the north of Tooting Bed Common, north down Cavendish Road (passing Weir Road), west along the approximate line of Kenilford Road, along Oldridge Road, turned north by Holy Ghost School, west of Rusham and Montholme Road and along Northcote Road, 8-11m AOD.<ref name=wr>illustrations 1, 4 of the webpage of the Walbrook River page - a synopsis which cites the following books:
Nicholas Barton, The Lost Rivers of London (1962)
Anthony Clayton, Subterranean City (2000)
Michael Harrison, London Beneath the Pavement (1961)
Alfred Stanley Foord, Springs, Streams, and Spas of London. (1910)
J. G. White, History of The Ward of Walbrook. (1904)
Andrew Duncan, Secret London. (6th Edition, 2009)</ref> <ref name=map>Ordnance Survey map, courtesy of English Heritage</ref> After St John's Road it flowed along Falcon Road, Battersea just before its end turned west emptying in the River Thames west of Lombard Road and north of the London Heliport.<ref name=wr/>
Use of the Name in Local Places
Its immediate area reflects its existence in the naming of certain features: Falcon Park, Falcon Road, "The Falcons" housing estate, and the Falconbrook school.<ref name=map/>
Falconbrook's catchment basin, unlike longer tributaries such as the Lea and Wandle is entirely based on impermeable to semi-impermeable London Clay, starting north of areas with remaining Lambeth Group and North Downs topsoil.
Ponding of the "Falcon Brook" has been recorded as early as 1745. An entirely London Clay catchment basin and flatter lower course through Battersea was before urbanisation a major factor contributing to the stream's overflow. Now separate surface water and sewerage systems where in place and sufficient drain parks and residential areas and attempt to intercept the sewerage system before polluting the Tideway — a further interceptor pipe the Thames Tideway Scheme is expected to be completed by 2023 to avoid overflow.<ref name=prfa/>
Thames Water carried out work at the end of 2006 to resolve the flooding of the Falconbrook sewer in the north of Balham, involving a series of road closures.
In July 2007, demonstrating response to rainfall due to a combined sewer function, the Falconbrook sewer burst out of the pavement in several places and flooded Falcon Road by Clapham Junction, during the 2007 floods since 2007 five incidents have been recorded of flooding in the Critical Drainage Area 7_21 that covers that area.<ref name=prfa>London Borough of Wandsworth — Preliminary Flood Risk Assessment (pdf)</ref>
- Tributaries of the River Thames
- List of rivers in England