What is Stormwater Management?
• Stormwater management or SWM is the control of stormwater runoff and its impacts. • Stormwater runoff is rainfall or snowmelt that runs off the ground or impervious surfaces such as buildings and roads and drains into natural or manmade drainage ways. Runoff picks up debris, oils and other pollutants as it drains. Why do we need stormwater management? • To protect the City’s stream valleys from pollutants, trash and stream bank erosion. • To make our stream valley parks more attractive and more useable. • Rockville’s streams ultimately drain into the Potomac River and the Chesapeake Bay. Healthy streams add to the overall health of those bodies of water. • To comply with State and Federal requirements of the Clean Water Act. What happens if we don’t do stormwater management? • The City’s streams will continue to erode unchecked, which results in wider, deeper stream channels and more sediment in the stream channels. • More trees will fall along the eroding stream banks. • Widened str
When it rains or snows, the amount of water that is absorbed back into the environment varies largely on whether the land is paved or natural. Rain and snow on natural or undeveloped land gradually infiltrates into the soil, replenishing groundwater supplies and slowly discharging excess runoff to local creeks. In contrast, as we pave roads and sidewalks, construct buildings or add other impervious surfaces, the amount of water that can be naturally absorbed after a rain or snow event is reduced drastically. Water that cannot infiltrate into the surrounding environment is called water runoff or stormwater runoff. In order to prevent our communities from flooding, stormwater runoff is diverted into storm drains and carried to the nearest stream. Ultimately, this runoff makes its way to the Chesapeake Bay through our numerous watersheds. Because impervious surfaces prevent stormwater from infiltrating into the soil, runoff increases in quantity and speed, causing environmentally harmful,
