Bioswales are linear, vegetated ditches that allow for the collection, conveyance, filtration and infiltration of stormwater. Bioswales are often used in areas that are otherwise comprised of large impermeable surfaces (office parks, large parking complexes, etc.).
In the event of a heavy rainfall event, these areas shed large volumes of runoff as the pavement is unable to absorb the falling rain water. Traditionally water runs off of asphalt or cement into a gutter or along a curb until it reaches the inlet of a storm sewer drain.
A bioswale replaces a traditional concrete gutter with a natural one. The vegetation in a bioswale slows the water’s velocity, allowing for treatment and infiltration. This slowing effect reduces the time of peak run off time.
The vegetation in a bioswale does more than simply slow down the flow of water, as the plants filter suspended sediments from the water passing through the swale. While the plants remove the larger particles, microbes in the soil digest organic nutrients which in high concentrations could be considered pollutants. The added vegetation can be a more visually appealing alternative, particularly if decorative place species are chosen for the swale. The added green space could provide habitat for some wildlife species, especially birds. Bioswales offer a more colorful alternative to traditional stormwater conveyance systems.