Urban rivers in London

Hogsmill River, Salmons Brook (a tributary of the River Lea), River Pinn, Marsh Dykes: These four catchments are all tributaries of the river Thames. Totalling 51km in length, they are classified as heavily modified rivers due to urbanisation and flood defence. Between 53-76% of the total catchment area consists of urban and industrial land use, so the rivers are important for biodiversity and as public amenity spaces. However, they face typical urban pollution issues: misconnected and cross connected plumbing, polluted run off from roads, point pollution, sedimentation and fly tipping.