Stormwater is rainwater and melted snow that runs off lawns, streets, and other land surfaces. This runoff is supposed to be absorbed by plants and soils or make its way back to ponds and streams. However, more hard surfaces — such as pavement, parking lots, driveways, sidewalks, and roofs — especially in urban areas, prevent this runoff from naturally soaking into the ground. Stormwater has several environmental impacts, including flooding and the erosion of rivers and streams.