Bioswale

A landscape element designed to concentrate or remove silt and pollution from surface runoff water

A bioswale is a landscape element designed to concentrate or remove silt and pollution from surface runoff water. They are typically vegetated, mulched, or xeriscaped, and consist of a swaled drainage course with gently sloped sides (less than six percent) and filled with vegetation, compost, and/or riprap. Bioswales are designed to maximize the time water spends in the swale, which aids the trapping of pollutants and silt.

Design and Function

Bioswales are designed to manage water runoff from a specific area, reducing the risk of flooding and erosion while improving water quality. The design of a bioswale includes a series of components:

• Vegetation: Plants in a bioswale are selected for their ability to withstand both wet and dry conditions. They help slow down the flow of water, allowing sediments to settle and pollutants to be absorbed.
• Soil and Substrate: The soil in a bioswale is engineered to support plant growth and facilitate the infiltration of water. It often includes layers of sand, gravel, and organic matter.
• Inlet and Outlet Structures: These structures control the flow of water into and out of the bioswale, ensuring that it does not overflow and that water is evenly distributed.

Benefits

Bioswales offer several environmental and economic benefits:

• Water Quality Improvement: By filtering pollutants and sediments, bioswales improve the quality of water entering natural water bodies.
• Flood Mitigation: By slowing down and absorbing runoff, bioswales reduce the risk of flooding.
• Habitat Creation: The vegetation in bioswales provides habitat for wildlife, including birds and beneficial insects.
• Aesthetic Value: Bioswales can enhance the visual appeal of urban and suburban landscapes.

Applications

Bioswales are used in a variety of settings, including:

• Urban Areas: To manage stormwater runoff from roads, parking lots, and rooftops.
• Agricultural Lands: To reduce runoff and improve water quality in nearby streams and rivers.
• Industrial Sites: To treat runoff from impervious surfaces and reduce pollution.

Challenges

While bioswales are effective, they also present challenges:

• Maintenance: Regular maintenance is required to ensure that bioswales function properly, including removing debris and invasive species.
• Design Complexity: Proper design is crucial to ensure that bioswales effectively manage water and pollutants.

Also see

• Rain garden
• Green infrastructure
• Stormwater management
• Riparian buffer