Stormwater Runoff in Urban Watersheds

Stormwater Runoff in Urban Watersheds

When precipitation falls over urban watersheds, its fate may differ from precipitation that falls over undeveloped, rural or natural watersheds. Different urban land use types can affect strormwater runoff patterns in different ways. There are many potential non-point sources of nutrients, sediment, and other contaminants within urban watersheds. During storm events, rainwater can pick up these contaminants and transport them downstream.

Commercial watersheds often have higher concentrations of impervious cover (such as rooftops, paved roads, and parking lots), which can lead to less stormwater infiltration (when precipitation soaks into the ground and replenishes the groundwater) and more stormwater runoff (when precipitation flows overland until it joins a body of water such as an urban stream). This stormwater runoff can flow into stormwater infrastructure designed to prevent flooding and be quickly diverted to urban streams. This stormwater runoff may pick up contaminants from the urban environment.

High density residential watersheds tend to have fewer impervious surfaces than commercial watersheds but more than single family residential watersheds. Infiltration is highest in single family residential watersheds, where industrial and urban contaminants are less common but sources of nutrient pollution such as fertilizer, pet waste, and yard waste are more common.