Once again, rain is in the forecast. After years of drought, that pitter-patter is the sound of relief.
Yet for many—especially those near waterways and other low-lying areas—rain is also cause for concern. Climate change is already making storms more intense, and flooding more frequent. Thankfully, there’s a solution that’s got a deluge of benefits.
What if I told you there was a way to capture stormwater runoff that made your neighborhood more beautiful and biodiverse, while also reducing flooding, replenishing groundwater, filtering pollution, and mitigating heat?
This is the power of the humble bioswale, also known as a rain garden.
Its purpose is exactly that, to be a garden made for rain. Bioswales are landscaped ditches designed to mimic natural ecosystems. They’re often inconspicuous, so there’s a good chance you’ve walked by one without even noticing it. Yet if you see a curbside green space sitting below the surrounding pavement, dotted with rocks and drought-resistant plants, you’ve likely found one of our best tools for making the city more resilient. Once you start seeing them, you’ll begin to notice them all over town.
When storms come, these low places are where the rain collects. Bioswales absorb all this water, easing the burden on our sewer system and filtering pollutants from cars found in the runoff. Having been transformed into an oversized puddle with great landscaping, the bioswale then allows the stormwater to filter into the ground, replenishing aquifers that are often starved by our love affair with asphalt. And by pulling back the concrete and allowing nature to flourish, we create a healthier and more enjoyable environment for all of us.
Bioswales are a form of green infrastructure, the likes of which are being rapidly rolled out to serve the dual purpose of combating climate change and improving urban living. A great example of this comes from Hoboken, New Jersey. A low-lying city next to the Hudson River, Hoboken built new parks on top of storage tanks capable of handling 1.4 million gallons of stormwater. Or take the Dutch town of Nijmegen, which made room for the river and created a new river park in the process. It’s easy to imagine what this level of investment in green infrastructure could do for an initiative like the Blue Greenway, stringing together existing parks with new ones to absorb rising tides while reconnecting communities and ecosystems along San Francisco’s industrial eastern waterfront.
Bioswales and other green infrastructure—like our existing parks—have economic benefits as well. Returning to the story on Hoboken: “Disinvestment in parks is going to cost the city in the long run because parks are a first line of defense against climate change. As Amy Chester, who directs Rebuild by Design, pointed out in the magazine Vital City, New York’s natural acreage absorbs as much rainwater as $580 million worth of green infrastructure.” It’s been estimated that every dollar invested in green infrastructure ultimately yields $2 in “avoided losses,” such as from office closures and flooded basements. Forget Gamestop, invest in parks!
San Francisco’s best bioswale is undoubtedly the one at Valencia and Duncan, which accomplishes several things simultaneously. In addition to being bigger, greener and more aesthetically appealing than many of the city’s bioswales, it also serves as a traffic-calming element, simplifying an awkward three-way intersection where Valencia and Duncan are intersected diagonally by Tiffany St. The bioswale calms and simplifies traffic flow on Duncan and Tiffany while remaining porous for cyclists and pedestrians who use this popular route.
With a new law mandating daylighting intersections, a rising stormwater surcharge on city water bills, and the rain continuing to pitter-patter against the window, there will be plenty more opportunities to implement bioswales and other green infrastructure throughout our city. By embracing these tools, we can transform our relationship with water and the places we live, creating a greener and more resilient future for ourselves and future generations.
This is a greener future that could appear on every block. It’s also more lush, inviting, and enjoyable than the streetscape we have today. Making our city resilient to climate change can often seem like a big, expensive, and abstract problem. But the bioswale on Valencia and Duncan reminds us that sometimes the solutions we’re seeking can be refreshingly attainable.