What is a bioswale?

November 29, 2018

You may have unknowingly parked next to, landed in a plane, or drove past miles of bioswales in your life and not even knew they existed or more importantly their actual purpose. Bioswales are large areas designed to both collect and treat stormwater runoff from impervious surfaces. With increasing regulations to not just reduce stormwater runoff, but also to improve the water quality, bioswales have become an effective tool for this purpose.

Courtesy of https://theray.org/tech/bioswales/

Keep in mind that here in Georgia and Metro Atlanta that the majority of precipitation events are 1 inch or less.  Therefore, those are the events most regulators, environmental groups, and engineers design plans to capture and return the water to the landscape in a manner that mimics nature.  Natural landscapes, such as forest, allow the water to infiltrate through the soil and either be stored, taken up by plants, or move as groundwater before recharging a downslope stream.  Impervious surfaces (roads, roofs, etc.) prevent this from occurring and water must be transported horizontally across the surface.

This stormwater is now being collected along parking lots and roads into bioswales.  Bioswales use a combination of vegetation and most importantly engineered soil placed on a specific grade to collect water and allow it to infiltrate into the soil and/or be taken up by the plants for evapotranspiration.  The soil is designed to filter the water from pollutants while providing plants a media to grow by using the water and excess nutrients filtered from the runoff.

Think of the soil as a sponge that soaks up water, stores some of it for plants to use, and allows the excess to recharge the groundwater below.  That’s the coolest ditch you ever saw, and some of the plants can even make the landscape look amazing!  So next time you run through the parking lot when it is raining, look where the water is flowing because it might just be into a bioswale.

For further in depth reading and if you are interested in learning more about stormwater here in Georgia check out the Georgia Stormwater Management Manual at:


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