Urban runoff

Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing^[1] created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain, storms, and other precipitation events, these surfaces (built from materials such as asphalt and concrete), along with rooftops, carry polluted stormwater to storm drains, instead of allowing the water to percolate through soil.^[2] This causes lowering of the water table (because groundwater recharge is lessened) and flooding since the amount of water that remains on the surface is greater.^[3]^[4] Most municipal storm sewer systems discharge untreated stormwater to streams, rivers, and bays. This excess water can also make its way into people's properties through basement backups and seepage through building wall and floors.

Urban runoff can be a major source of urban flooding and water pollution in urban communities worldwide.

^ "Impact of Water Runoff from Streets and Yards". Highlands Ranch, CO: Highlands Ranch Metro District. Retrieved 30 August 2021.
^ "Runoff (surface water runoff)". USGS Water Science School. Reston, VA: U.S. Geological Survey (USGS). 2018-06-06.
^ Water Environment Federation, Alexandria, VA; and American Society of Civil Engineers, Reston, VA. "Urban Runoff Quality Management." WEF Manual of Practice No. 23; ASCE Manual and Report on Engineering Practice No. 87. 1998. ISBN 1-57278-039-8. Chapter 1.
^ Schueler, Thomas R. (2000) [initial publ. 1995]. "The Importance of Imperviousness". In Schueler; Holland, Heather K. (eds.). The Practice of Watershed Protection. Ellicott City, MD: Center for Watershed Protection. pp. 1–12. Archived from the original (pdf) on 2014-03-27. Retrieved 2014-12-24.