Raingardens take the city back to nature
Now that the snow is gone, small, oval “I am a raingarden” signs are once again visible next to landscaped, shallow indentations in many neighborhood yards. No one can help but notice that raingardens exist. But not everyone knows how raingardens are designed nor how they function. And, almost no one knows (except avid Southside Pride readers who remember everything they read) that all raingardens on the west side of Powderhorn Park are part of a study investigating urban watershed issues.
The person who can tell you everything you ever wanted to know about raingardens is Michael Keenan, lead landscape designer at Metroblooms, the nonprofit organization coordinating the Powderhorn study.
Keenan says, “A Raingarden is a flat-bottomed, bowl-shaped depression on a lawn or backyard space. It is strategically placed to collect, store and infiltrate storm water runoff that’s generated from impervious surfaces such as roofs and driveways.”
He explains that Raingardens are not there for looks, though they can be beautiful. The function of a Raingarden is the protection of water ecosystems.
What happens in urban areas is that phosphorous from fertilizer, yard clippings, leaves and other debris and toxins are rarely naturally absorbed and filtered by the earth over time. Normally, they drain quickly across lawns and roads or streets into a storm water system that outputs directly into local streams, rivers or lakes, causing meaningful and sustained damage to ecosystems at scales ranging from stream and pond size to algae blooms in the Gulf of Mexico.
So, Raingardens help restore the natural functionality of the water cycle by minimizing runoff into urban storm water systems. More effective than rainbarrels, the volume of an average Raingarden allows it to hold and infiltrate potentially hundreds of gallons per rainstorm. This makes possible a slow, natural process of filtration that breaks down toxins underground and prevents the sudden release of these compounds into aquatic environments.
U.S. environmental protection policies have gone a long way toward eliminating “point source” water pollution sources such as factories and hazardous waste sites. Today, “broad source” runoff from public rights of way and private property such as factory farms, suburban lawns, urban lawns and street drains is the biggest culprit in water ecosystem degradation.
While ecologically functional, the gardens are also botanically interesting.
“The types of plants that we are putting in are primarily drought tolerant prairie plants that can withstand temporary lack of water,” elaborates Keenan. “We use other types of plants in the shade. Overall it’s a specific type of plant, but we have a large variety of species to choose from. We aim for a mix between formal and native. Both extremes on the continuum require more maintenance from the gardener.”
The Powderhorn neighborhood is an ideal fit for the Metroblooms study for a variety of reasons. It’s a large 330 acre watershed all flowing into one basin: Powderhorn Lake. Furthermore, the buildup throughout the watershed is on mostly uniform terrain, with similar yard and lawn characteristics throughout.
Keenan explains the Powderhorn Raingarden study. “Our project is comparing and testing the quality and quantity of water that flows from two distinct sub-watersheds into Powderhorn Lake. Last summer we installed 122 Raingardens in the west side watershed, and we’re installing more this year. Now we’re testing the difference that can make.”
In other words, the study is comparing the flow from the west side of the lake, where the Raingardens are, with the east side’s flow, which is unfiltered by Raingardens.
Keenan’s interest in Raingardens began a few years ago when he was a graduate student. “While kayaking down a local river I started noticing the storm water outflows. I could see in the middle of the summer steaming hot water pouring into the river. I investigated and learned more about what was going on. I knew I had to do something about it.”
Now, Keenan’s passion for Raingardens and his collaboration with area residents is serving a number of beneficial purposes in the Powderhorn community. One of these is the raising of urban ecological awareness.
“Getting involved with Raingardens is a way to connect the community to its local water bodies, to create an understanding that the way people treat their back yards affects local water quality and ecosystems,” says Keenan.
Sometime this heightened awareness can lead to heated interactions.
“There was a homeowner who had a Raingarden installed, and got very involved. Her neighbor did not participate in the project and had her lawn professionally mowed,” recalls Keenan. “This commercial company was mowing and grass clippings were going into the street. The Raingarden woman went out and started yelling at them saying ‘You can’t do it that way! That stuff is going to the lake! It’s causing algae blooms!’ ”
But the interaction stimulated by the Raingardens is usually the opposite.
“The whole project has been something of a community barn-raising event,” declares Keenan. “Neighbors weren’t always talking so much, there were people who were shut in. Now they have this common speaking piece. There’s been a new community that has been built up around these Raingardens.”
The Powderhorn Raingarden study is a small part of a greater panorama: retrofitting and redesign of the urban landscape. This larger, global movement includes such innovations as permeable pavement, maximization of active and passive solar collection, small wind turbines and rooftop gardens for insulation, beauty and food production.
All of these elements will play a role in creating the city of the future.
“I think cities make sense, it’s a concept that will last,” Keenan reflects in conclusion. “It’s the sprawl that will end. We need to model our human systems much more in line with natural systems. Nature’s inventions are economical and effective, and many of our systems don’t make sense. A prime example is our current runoff stormwater system—it pollutes our water. That doesn’t make sense.”
Raingardens make sense.