Stormwater management practices are used to manage the impacts of stormwater runoff. Stormwater runoff is generated by impervious surfaces (rooftops, roads, parking lots, etc.) because they do not allow rain to soak into the ground. Impervious surfaces also accumulate pollutants deposited from the atmosphere, leaked from vehicles, or wind-blown in. These pollutants wash off of impervious surfaces and are delivered to downstream waters during storm events. Stormwater management practices improve water quality and reduce the flooding associated with increased impervious cover and surface runoff.