In Defense of Bioswales

There is a trend among environmentalists to push for something called “daylighting” of storm water flows.

That just means that when an area is developed, the storm water is channeled to open ditches rather than through underground pipes–i.e., “storm sewers.”  This is an environmentally preferable practice because it eliminates the “out of sight, out of mind” syndrome and makes any pollution that enters the storm sewer highly visible.

A refinement on this practice is to have a “bioswale.”  This is a ditch that has vegetation.  Ideally, the vegetation will be local ecotype native plants that are adapted for wet areas.  This also allows a certain amount of biological treatment of the storm water.

Bioswale management is still in its infancy.  Bioswales can look kind of rugged and weedy and people aren’t really used to them yet.  I think there is an issue with the land management of the area surrounding bioswales as well–trying to keep turfgrass next to a bioswale with taller vegetation sort of mixes two incompatible land uses.

I have done butterfly surveys on a local bioswale, and have found that there are almost twenty  times as many butterflies in that particular bioswale than in turf-grass residential-type habitats.   Unfortunately, a part of the bioswale that I have surveyed will be filled as part of another project.  An underground storm sewer will replace it.

I was too slow in voicing my opinion on that project and maybe I wouldn’t have been able to change it anyway.  However, I am still sorry to see that section of the bioswale go.


About the roused bear

Nature photographer from central Iowa.
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1 Response to In Defense of Bioswales

  1. Rich Pope says:

    I agree in concept with the bioswale arguments you post and the need to try to avoid out of sightism. You know of course a couple of the first arguments against, like, mosquito (and encephalitis, West Nile, etc. ) risks and of course, but it looks unsightly and reduces property values…… Any thoughts on how we effectively rebut some of that would be interesting discussion points.

    Thanks Harlan…. Rich

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