A bioswale (also known as bioretention area) is very similar to a rain garden, the main difference being its linear, swale shape. What distinguishes a bioswale from a conventional swale (or ditch)? The latter are typically vegetated with turf grass and are a conveyance tool, basically a grassy stormwater sewer that conveys water as quickly as possible from point A to point B. In fact, a lot of conventional swales or ditches are required by code to have a minimum flow velocity of, let's say, two feet per second.

A bioswale differs in that the turf grass is replaced with native prairie vegetation. This will significantly reduce the flow velocity (slow down of the runoff) in the swale’s drainage course. The residence time of the runoff is thus increased, which gives it the time to be stored, filtered, and infiltrated. These processes remove pollutants and suspended solids from runoff.

We decided to install a bioswale that would infiltrate any overflow we may get from the adjacent cistern, once it is full. Because the bioswale was in the shade of the house, we planted it with native savanna and woodland species, including grasses and sedges that have taken very well. The bioswale turned the awkward, narrow fringe space just north of the house into an area that has beautiful floral and textural interest throughout the year. It also attracts a variety of wildlife.

You can download an INFO SHEET for more detailed information on the bioswale or browse images of the bioswale INSTALLATION, FIRST GROWING SEASON, and SECOND GROWING SEASON.

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