Runoff is a natural hydrologic process
that is strongly influenced by land use. Runoff from rainfall or
melted snow has three possible short-term routes: it can run off
the land surface, percolate to the groundwater reservoir or go into
storage on or near the surface. Urbanization of a watershed, such
as paving of roads and installation of drainage systems, can result in
increased surface runoff rates.
Stormwater drains relieve
localized flooding but contribute a higher velocity and volume of runoff
downstream. The quality of stormwater runoff from urban areas is
of vital concern when a waterbody is located nearby. Runoff can
carry oil and gasoline from vehicles, leaves, soil, lawn chemicals and
fertilizers. Potential contaminants are washed into streams and
lakes in sufficient concentrations to degrade the water quality of the
receiving body of water.