A bioswale is a resilient vegetated stormwater solution that treats and retains stormwater as it moves from one place to another.
During seasonal shifts, city sewer and stormwater systems can struggle to keep up with increased water runoff. But your facility can help take some of the pressure off of your city’s infrastructure and lower your stormwater fees by investing in green infrastructure.
One such cost-effective and resilient approach is the bioswale. The Environmental Protection Agency (EPA) defines bioswales as “vegetated, mulched or xeriscaped channels that provide treatment and retention as they move stormwater from one place to another.”
These systems slow the flow of runoff water while making it cleaner and safer for the environment. Most importantly, you can easily install them at your facility.
Bioswales provide a number of advantages for facility managers. Here are four key benefits you could gain by implementing them.
1. Better Stormwater Management
Bioswales provide a smart stormwater management system for facility managers interested in sustainability. The EPA reports that pollution from urban stormwater runoff harms water in about 5,000 miles of estuaries, 1.4 million acres of lakes and 30,000 miles of rivers. Thus, vegetated swales provide an opportunity for your facility to slow and filter stormwater runoff.
Similar to rain gardens – often used to collect runoff from roofs, sidewalks and streets – bioswales are best suited for large impervious areas like parking lots, notes the Soil Science Society of America. This makes them an ideal solution for facilities.
The biggest advantage bioswales offer is reducing stormwater runoff. According to the American Society of Landscape Architects (ASLA), a 4-meter bioswale can reduce about 25% the of total rainfall runoff.
The effectiveness of bioswales extends to their ability to filter stormwater naturally. The soil and vegetation in bioswales can root out pollutants and contaminants that would otherwise end up in stormwater systems and bodies of water. By reducing the amount of water that ends up in city stormwater systems and cleaning what does go in, you can approach resilience from two directions.
2. Flexible Application
Unlike a number of stormwater solutions, bioswales are highly flexible for application. They work in any number of geographical areas, as long as they aren’t expected to bear the responsibility of managing abnormally high volumes of water runoff.
“Bioswales may be effective in any region as they can be tailored to the specific installation location by incorporating native plants,” notes conservation partnership Naturally Resilient Communities (NRC). “They may be designed to convey any size storm but are most effective in dealing with frequent, small rain events.”
More specifically, vegetative swales are flexible options for facilities because of their long, linear orientation, which can be parabolic, trapezoidal or v-shaped. Bioswales can fit in easily in parking lots as long as they aren’t implemented in areas with large slopes.
NRC suggests constructing bioswales in locations with a mild slope (no greater than 5%) due to the risk of erosion.
During a heavy rainstorm, a bioswale with a steep slope will erode quickly, rendering it useless. If you do implement one in a space where the slope is steep, erosion mats can help hold the soil, explains the Illinois Department of Natural Resources (DNR).
3. Reduced Maintenance
Assuming they are properly installed in a low-slope area and don’t risk the threat of erosion, bioswales can significantly reduce maintenance to stormwater management systems and landscaping.
“Maintenance costs may be reduced through the use of native grasses and plants that are already adapted to the area, requiring less water, no fertilizer and infrequent mowing,” states NRC.
However, if you don’t properly safeguard the swale against erosion, you may end up needing to do more frequent maintenance or reconstruction to undo the loss in sediment. “If sediment is not removed periodically, a bioswale may eventually need to be regraded to restore the proper flow,” NRC adds.
In addition to less upkeep, bioswales can help you reduce your water bill. With the right plant choice, you won’t need to water the vegetation in the bioswale outside of the initial period after planting. The Illinois DNR suggests using “hardy native plants with an established root system.”
4. More Aesthetically Pleasing
For some facilities, stormwater management means concrete fixtures that may be effective in handling runoff but are ultimately eyesores. Bioswales offer a more aesthetic alternative.
You can liven up the landscaping of your facility while still addressing stormwater management with bioswales. Because they double as a landscaping feature, bioswales allow for some personalization with the vegetation you choose.
If you’re considering bioswales, consult with an expert to identify plants that will work best in your climate.
Justin Feit [email protected] is Associate Editor of BUILDINGS.