We've got plenty of old stormwater detention basins throughout Cuyahoga County. You'd recognize them if you saw them, big depressions with concrete channels running from one pipe to another across the basin. In the past when designing for flood control, we made it our goal to get water from one place on our properties to another as quickly as possible, and those concrete channels do exactly that, transporting water from one end of the basin to another during typical low flow rain events. As we have learned more about stormwater, we have realized the benefits of holding water on site longer, allowing it to infiltrate to the natural soils, as it would in a forested natural landscape, and we have moved away from those older designs.
All of those existing basins provide an opportunity for what we call "retrofits." Essentially you can remove the low flow concrete channels, replace them with deeply rooting native vegetation, and move to an annual mowing cycle to allow the basins to behave more like a wetland than a turf lawn. By allowing water to spread throughout the basin and allowing mature growth of vegetation, we can slow down water, provide better infiltration, and better filtration by vegetation. We get enhanced flood control and water quality treatment.
By naturalizing basins with low flow channels, we provide water quality treatment for smaller storms that would previously get none, which helps out our fish populations in the downstream rivers and lakes. As an added bonus, naturalizing basins provides important wildlife habitat that is in short supply in our urban environments. By adding native wildflowers, grasses, and herbaceous vegetation and moving to an annual mowing cycle after the first frost, we provide a place for birds, pollinators, and amphibians to eat and live throughout the spring, summer, and fall.
While adding wildlife habitat is a bonus, and maintenance of naturalized basins is less frequent with annual mowing versus bi-weekly or monthly mowing ($$$ savings), there are additional considerations that do need to be made. When considering a basin retrofit you need to get your regulatory authorities involved. There may be federal, state, and local requirements to meet before retrofitting a basin. Contact your municipal engineer and find out where to start.
If you have questions about stormwater basin retrofits and stormwater basin maintenance contact Elizabeth Hiser, Cuyahoga SWCD Natural Resources Coordinator.
Blog Author: Elizabeth Hiser, Natural Resources Coordinator