Stormwater

Stormwater is excess water from precipitation events—moving through the environment by infiltrating soil, running off into nearby water bodies, or running into streetside storm drains. Once it enters these storm drains, the stormwater moves through a series of underground pipes that carry the water directly into a nearby lake, river, or stream, without any treatment. (Contrast this to household waste, which is moved through a separate system of underground pipes and routed to a wastewater treatment plant for the water to be cleaned.)

Drainage systems are imperative for conveying water after heavy precipitation events, but can also carry pollutants into nearby water bodies.

Our towns and cities are full of impermeable surfaces—meaning water can’t get through them—like roads, sidewalks, roofs and parking lots. More impermeable surfaces means more surface runoff and less infiltration.

As stormwater quickly runs off these surfaces, it picks up and transports just about anything in its path—soil, fertilizers, pesticides, excrement, oil, and other environmental contaminants.

Stormwater runoff rapidly empties into streams, causing flashy flows during heavy rains and increased likelihood of streambank erosion. Further, the increase in impermeable surfaces means greater amounts of runoff in shorter periods of time, leaving urban areas vulnerable to flash flooding—when more water is generated than a stream can handle, the water spills out into adjacent streets, buildings, homes, and businesses.