Stormwater Runoff

meeting the challenges of a changing landscape

How increased stormwater runoff affects water quality and stream health.

Steps homeowners can take to help manage runoff.


What is Stormwater Runoff?

Stormwater runoff occurs when water from rain or snowmelt flows over the ground. Impervious surfaces such as driveways, sidewalks and streets prevent stormwater from naturally soaking into the ground.

Development typically replaces the natural landscape with impervious surfaces like roads, roofs and parking lots. When stormwater cannot sink into the ground, it has nowhere to go but to flow across the surface of the ground.

Where Does Runoff Go?

Most stormwater runoff flows either:

  • directly into streams, rivers, ponds, lakes and wetlands

  • down the nearest stormdrain into the nearest waterway without any treatment

Why is Stormwater Runoff a Problem?

Water Pollution

Stormwater washes pollutants off roads, lawns and other surfaces and carries them into the nearest body of water. Some of the pollutants commonly carried by runoff are:

  • Sediment
  • Oil, grease, and toxic chemicals from motor vehicles
  • Pesticides and nutrients from lawns and gardens
  • Viruses, bacteria, and nutrients from pet waste and failing septic systems
  • Heavy metals from roof shingles, motor vehicles, and other sources
  • Road salts

These pollutants can harm fish and wildlife populations, kill native vegetation, foul drinking water supplies, and make recreational areas unsafe and unpleasant.

Stream Damage

Increased flow resulting from excess runoff causes extensive damage to streams, scouring the stream bottom and causing severe erosion to stream banks. The risk of flooding downstream also increases.

Land cover affects...

Stream health.

3 Easy Steps Homeowners Can Take to Help Manage Runoff

Rain Barrels

You can collect rainwater from rooftops in mosquito-proof containers. The water can be used later on in lawn or garden areas.

Rain Gardens

Specially designed areas planted with native plants can provide natural places for rainwater to collect and soak into the ground. Rain from rooftop areas or paved areas can be diverted into these areas rather than into storm drains.

Vegetated Filter Strips

Filter strips are areas of native grass or plants created along roadways or streams. They trap the pollutants stormwater picks up as it flows across driveways and streets.

How Can Homeowners Reduce Pollution in Runoff?

Lawn Care

Don’t overwater your lawn. Consider using a soaker hose instead of a sprinkler. Excess fertilizers and pesticides applied to lawns and gardens wash off and pollute streams. Use pesticides and fertilizers sparingly. Have your soil tested to determine how much fertilizer you need. When use is necessary, use these chemicals in the recommended amounts. Use organic mulch or safer pest control methods whenever possible. Compost or mulch yard waste.


Use a commercial car wash that treats or recycles its wastewater, or wash your car on the grass in your yard so the water infiltrates into the ground. Repair leaks and dispose of used auto fluids and batteries at designated drop-off or recycling locations.

Pet Waste

Pet waste can be a major source of bacteria and excess nutrients in local waters. When walking your pet, remember to pick up the waste and dispose of it properly (double bag it and dispose with garbage).

Septic Systems

Leaking and poorly maintained septic systems release nutrients and pathogens (bacteria and viruses) that can be picked up by stormwater and discharged into nearby waterbodies. Inspect your system every 3 years and pump your tank as necessary (every 3 to 5 years). Don't dispose of household hazardous waste in sinks or toilets.

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For a presentation on Stormwater, click here.