Urban and suburban areas have a high amount of impervious surface cover such as buildings, sidewalks, streets and parking lots. Impervious surfaces block much of the rainwater that falls on the landscape from soaking into the ground and instead turns it into stormwater runoff.
Road culverts and curb and gutter systems collect this stormwater runoff and may quickly deliver large amounts to area streams causing high stream flow with stream bank erosion and degradation of stream habitat.
In addition, urban areas are known sources of pollutants including excess nitrogen, phosphorus, and sediment that are washed off into area streams during rainstorms. Pollutant sources include lawn and garden fertilizers, leaky sanitary sewer or septic systems, pet waste, and deposition of airborne nitrogen by-products from automobiles and gas powered lawn tools.
Suburban environments use stormwater management facilities, generally called Best Management Practices (BMP), to slow down stormwater runoff and remove pollutants before the stormwater gets into streams and eventually transported to downstream ecosystems such as the Chesapeake Bay.
There are different ways stormwater BMP may be used in urban areas. Traditionally, stormwater BMP are used in a centralized approach (meaning fewer BMP in a given area with larger urban areas draining to them). However, BMP have recently begun to be integrated into the urban landscape and used in a distributed way (multiple different BMP often connected in a series with smaller urban areas draining to them, and used to address water detention, infiltration into groundwater, and removal of pollutants including nutrients and sediment).
Can Best Management Practices help protect streams in developed landscapes?
Animation showing urbanization near the study areas in Montgomery County, from the year 1951 to 2008. Image source: Montgomery County GIS.