Bioswales are long channeled depression or trench that receives rainwater runoff from solid impervious surfaces and have vegetation and organic matter to slow water infiltration during rain storms. Planted with vegetation suited to boggy conditions, the bioswales act like miniature wetlands that filter out and biodegrade the toxins contained in the runoff.

Bioswales are designed to manage a specified amount of runoff from a large impervious area, such as a parking lot or roadway. Because they need to accommodate greater quantities of stormwater, they often require use of engineered soils. They are also linear systems that are greater in length than width and are vegetated with plants that can withstand both heavy watering and drought. The effectiveness of bioswales increases with increased contact time between soil and stormwater, and increased vegetative cover.

This is all best achieved by using soils that can adequately slow down, infiltrate, and retain water, as well as support plant life. In areas where nutrients are a concern to water quality, soils capable of retaining high amounts of phosphorus or nitrogen should be selected, along with plants that use nutrients very efficiently. Bioswales are a type of green infrastructure that helps clear the soil contaminants as well as the rain water contaminants ultimately improving the groundwater quality.