Paved surfaces are so ubiquitous in urban areas today that most of us give little thought to the impact they have on water quality and the health of the environment. But here's the sobering reality: As more available land area in the country gets paved over, a larger amount of rainwater ends up falling on impervious surfaces such as parking lots, driveways, sidewalks, and streets rather than soaking into the soil. This creates an imbalance in the natural ecosystem and leads to a host of problems including erosion, flash floods, water table depletion, and pollution of rivers, lakes, and coastal waters as rainwater rushing across pavement surfaces picks up everything from oil and grease spills to deicing salts and chemical fertilizers.