Bioswales Do More Than Clean Water

Riverkeeper recently collaborated with the owners of Johnson’s Beach to design and build a new bioswale that will clean up polluted stormwater runoff from busy downtown Guerneville streets before running into the Russian River. Due to heavy traffic on Hwy 116/ River Road, Guerneville has shown very high levels of dissolved metals in street runoff. Bioswales provide simple and sustainable natural pollution control by filtering out harmful contaminants with native plants and organic compost loaded with beneficial soil microbes that break down pollution. Bioswales also blunt the impacts of climate change.

The slogan for bioswales and other Low Impact Development designs in stormwater is “Slow It, Spread It, Sink It” a term coined by Occidental Arts and Ecology Center’s Brock Dolman.

By slowing down stormwater with boulders and rocks, and wide, low-gradient basins with check-dams, bioswales help to prevent the rush of water that can cause down-stream flooding.  The previous design allowed a 12-inch drain pipe to shoot stormwater straight toward the river over a paved surface with no way for the water to slow down.  Extremely high velocities of runoff cause erosion of sediment into the river, which cause major problems for spawning salmon.

The new basin, which was dug through old asphalt by local heavy equipment operators, was deep enough and wide enough to effectively spread out the stormwater over a large surface area.  Organic compost was integrated into the base of the channel to allow for the absorption of harmful chemical pollutants into the soil’s microbe-rich environment.  Additionally, the roots and grassy fibers of native plants capture pollutants, while filtering out pieces of microplastics and other trash.  Native plants are very well suited to this climate, and by being drought-tolerant they require far less watering through our long, dry summer months than many common landscaping plants.

With a potential drought looming, these bioswales allow for increased water storage by sinking the water back into the groundwater reserves in our communities before it runs into the river and out to sea.  Some climate change models suggest that we will be having extended periods of drought followed by massive atmospheric river storm events that just dump water in concentrated events.  Adequate storage of water for our communities is a big concern, and bioswales help with recharging our aquifers. By removing pollutants, bioswales are creating more drinkable groundwater reserves for a more resilient community.