Impervious surfaces are mainly constructed areas (rooftops, sidewalks, roads, and parking lots) covered by impenetrable materials such as asphalt, concrete, brick, and stone. These materials seal surfaces, repel water, and prevent precipitation from infiltrating soils. Soils compacted by urban development are also highly impervious. Everyone contributes to impervious coverage. As communities develop, the amount of impervious coverage increases. These surfaces concentrate and increase the flow of storm water within a community or region. This increases the potential for flooding and is a major factor in the degradation of water quality.