Stormwater, or the flow of water after a precipitation event, travels across the ground. During its travels, it may pick up pollutants ranging from fertilizers and pesticides, pet waste, auto fluids and trash. Without proper management, stormwater eventually reaches our waterways, carrying pollutants with it.
Bioswales are landscape features that manage stormwater and add beauty and diversity to your property with native plants. They are long, shallow channels that are gently tapered inward toward the center of the channel.
The channel of the bioswale is filled with soil mixed with sand and compost and planted with native species. The goal of a bioswale is to infiltrate stormwater into the ground, filtering out any pollutants it may carry. Any stormwater that is not infiltrated can be directed to a specific location, such as ponds, rain gardens or storm sewers.
Bioswales are different from traditional swales due to their amended soil and use of native plants to increase stormwater infiltration and are effective stormwater management tools.
Impervious surfaces
The pollutants that stormwater typically picks up around your home are often found on or built up on impervious surfaces. Impervious surfaces are surfaces that do not allow water to pass through, such as driveways, sidewalks and roofs.
Driveways can harbor oil and other auto fluids, sidewalks are seasonally coated in salt and our roofs can harbor bacteria from bird droppings and heavy metals from various airborne sources.
As the stormwater flows across these surfaces, it picks up pollutants as it moves toward storm drains or directly to our waterways. Storm drains empty directly into our waterways as well, so any pollutants that are carried end up in our local bodies of water, negatively impacting water quality and aquatic habitats.
The best way to combat stormwater pollution is by carefully managing stormwater and increasing permeable surfaces that allow water to pass through. Permeable surfaces include lawns, rain gardens and bioswales.
Bioswales can be installed in a variety of situations to increase permeability, such as along a property line, in a neighborhood lining a street or between roadways or parking lots.
Amended soils
With the amended soils and native plants, bioswales increase permeability allowing stormwater to easily infiltrate through the soil profile. Soils in bioswales need amendments in order to increase their permeability. Soils vary widely, while some sandier soils allow water to percolate quickly, clay-based soils can retain water for some time. Amending the soil ensures that stormwater is able to easily percolate.
Use Web Soil Survey (websoilsurvey.nrcs.usda.gov/app/) to check the soil type on your property to ensure you are amending it correctly. Compost and sand can be used to increase pore size within the soil and create variations in soil particle size.
The large pore size between the various-sized soil particles increases the infiltration ability of the stormwater. The faster and more effectively the stormwater is able to percolate, the less likely it is to carry pollutants to our waterways.
Native plants
Native plants are an essential component of bioswales and provide benefits for stormwater and native wildlife. Their deep and healthy roots break up the soil, making it easier for water to infiltrate into the ground. The plants take up water and transpire it into the atmosphere, further reducing the possibility of stormwater runoff.
Native plants also provide a habitat for many native species of animals and insects, adding diversity to your backyard food web. Some great examples of native plants that can be used in bioswales include New England Aster, Swamp Milkweed and Blue Flag Iris. There are many native, water-loving plants to choose from that can accent any landscape while enhancing your backyard habitat.
Implementing a bioswale improves stormwater management on your property and for your community as well. Both urban and rural communities can benefit from bioswales and their stormwater benefits.
If you would like more information about installing a bioswale, contact your local soil and water conservation district.
