If you live in a coastal city, you know not to swim in the ocean for several days after heavy rain. This is because water runoff can carry dirty and even harmful pollutants such as bacteria, chemicals, and sewage. Beautiful, planted rain gardens are a natural and effective way to clean water moving through communities. These gardens, also called bioswales, work so well that companies, and even entire cities, are adopting them to help clean water.
So how do they work? Vegetation is planted in a small depression on a slope and helps filter water before it reaches storm drains. They filter out 90% of chemicals and 80% of sediments. Additionally, they soak up 30 percent more water into the landscape than traditional lawns, helping alleviate flooding and droughts.
The University of California, Santa Barbara, Patagonia’s Ventura headquarters and the Los Angeles community of Westwood all use bioswales to improve water quality and drought resistance. The largest adopter of rain gardens is the City of Portland which is installing 83 green street planters to filter 7.1 million gallons of runoff and even offering free rain garden installation to residents. The project is part of the city’s Green Streets Resolution to reduce pollution and overhaul sewage systems.
On top of all their environmental benefits, these gardens can be incredibly beautiful as well. A wide variety of plants can serve as water cleaners including dogwood, grasses, and ferns. If you’re interested in landscaping your own home to filter out water pollutants, check out this guide on building your own bioswale.