What is stormwater management (SWM)?
Stormwater is rainwater that “runs off” from impervious areas (rooftops, parking lots, driveways, etc.) and lawns at a much faster rate than it would from woods or large grassy areas. This runoff flows quickly through storm drain pipes into the City’s streams. It can flood streets, erode stream banks, and topple trees. Runoff also picks up pollutants such as grit, oil and heavy metals from autos, pesticides and fertilizers from lawns, and sediment from bare spots. These pollutants impair Rockville’s streams, the Potomac River, and ultimately the Chesapeake Bay. SWM facilities treat runoff by trapping pollutants and trash and slowing the water’s release rate, which reduces downstream erosion.
