An urban stream is a formerly natural waterway that flows through a heavily populated area. Urban streams are often significantly polluted, due to urban runoff and combined sewer outflows.[1]
Government agencies may alter the flow and/or course of an urban stream to prevent localized flooding, using a construction technique called channelization and a collection of related practices collectively known as river engineering. These techniques may include lining a stream bed with concrete or other hardscape materials, and/or diverting the stream into culverts and storm sewers. Some urban streams, such as the subterranean rivers of London, run completely underground. These modifications have often resulted in loss of habitat for fish and other species, downstream flooding due to alterations of flood plains, and further deterioration of water quality.[2]
Some communities have initiated stream restoration projects, using techniques such as daylighting, in an attempt to correct the problems caused by previous stream alteration efforts, as well as to address stream bank erosion caused by heavy stormwater runoff volumes.[3][4]
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