Urban land surfaces are replaced by impervious surfaces such as roads and buildings, which prevent rain or snow-water from naturally draining into the ground and lead to extensive stormwater runoff. Stormwater runoff into nearby rivers without being cleaned of pollutants will contaminate waters. Low-impact development, such as permeable pavements and Sponge City, can restore the land’s ability to naturally manage road stormwater runoff and reduce the risk of flooding and water pollution.