Stormwater runoff is rainfall that flows over the ground surface. It is created when rain falls on roads, driveways, parking lots, rooftops and other paved surfaces that does not allow water to soak into the ground.
Stormwater runoff picks up and carries many different pollutants that are found on paved surfaces such as sediment, nitrogen, phosphorus, trash and bacteria. The runoff the flows either down the nearest stormdrain in the nearest waterway without any treatment or directly into streams, ponds and lakes. These pollutants can harm fish, wildlife and kill native vegetation.