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What Is Stormwater?

Stormwater drain with drainage destination painted

Whenever there’s precipitation, there’s stormwater. Stormwater is rain or water from melting snow that falls on or washes over pervious and impervious surfaces.

  • Pervious surfaces allow stormwater to be absorbed by the ground (e.g., forests, grass, gardens and other undeveloped land).
  • Impervious surfaces don’t allow stormwater to be absorbed (e.g., roofs, parking lots, streets, and other hard surfaces).

As we build the homes that we live in; the buildings where we work, shop, and play; and the roads that we drive and bike on, our forests, woodlands, and grassy areas change. So where does all of the stormwater go?

Stormwater runoff is excess water that can’t be absorbed by pervious surfaces, or that flows off impervious areas. This runoff enters Howard County’s stormwater drainage system, where it’s carried to local waterways—and eventually the Chesapeake Bay.

Along the way, stormwater runoff picks up anything in its path—including oil from cars, fertilizers, litter, pet waste, and sediment—and carries it to the streams and rivers in your backyard. These pollutants can harm plant and animal life. In addition, this runoff can cause erosion, flooding, and property damage if not properly managed.

Stormwater runoff is responsible for 20 percent of the Chesapeake Bay’s pollution.