Heavy rains fuel urban runoff

We finally received the rain we needed this week.  While this rain was good for our lawns and gardens, the excess water needs to run somewhere and that somewhere is usually our lakes and streams. Before I proceed, I need to define a term: impervious surface. Impervious surface is any surface on land that is impenetrable to water and prevents its absorption into the ground. Examples include rooftops, sidewalks, parking lots, and roads. The more impervious surface in a concentrated area, the less surface there is for rain to be absorbed into the ground. When rain is absorbed into the soil, it percolates through the ground getting filtered along the way and usually ends up in the groundwater. When rain is not able to be absorbed into the ground, it ends up in basements, collects in low areas, runs directly into lakes and streams from adjacent yards and flows into storm sewers.

In a heavy rain like this week, anything in your yard, streets and parking lots is washed away including lawn waste, pet waste, oil drippings, fertilizer and pesticides. In a town, since there is a high percentage of impervious surface, this waste can add up quickly. The Environmental Protection Agency (EPA) says, “because of impervious surfaces such as pavement and rooftops, a typical city block generates 9 times the runoff than a woodland area of the same size.” Lawn clippings and pet waste contain phosphorus, which fuels algae growth. Pesticides can kill beneficial aquatic insects in lakes and streams. Other toxic chemicals and gas can pollute lakes and streams by forming a film on top of the water and binding with lake sediments affecting habitat.

Storm sewers start with street gutters and typically end up in a storm pond or wetland. They are usually separate than a city’s waste treatment system. It is important to understand that the water that flows through storm sewers typically does not get treated before entering the natural environment. It is your responsibility to monitor what you put into or allow to enter the storm sewer and leave in your yard, driveway, and street.

There are ways that you can limit runoff from your property. First, keep your yard free of pet waste and unbagged piles of leaves. Avoid applying fertilizer to steep slopes where it can run off more easily. Think twice about paving more of your yard and increasing your impervious surface.

You can also be proactive and construct areas for rainwater to collect in your yard and get filtered such as rain gardens and wetlands. A rain garden is a depression that contains native plants and shrubs designed to collect and filter rainwater. It is both beautiful and functional.