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Curious Louis: How is St. Louis managing stormwater runoff?

Provided by the Metropolitan Sewer District of St. Louis
A rain garden at a residential property.

The first thing to notice about Clarice Hutchens’ front yard is that it isn’t a nicely manicured green lawn. Her house sits atop a steep hill and as you come up her driveway, you see piles of rocks, shrubs and trees that blend in well with the woods that surround her property.

Hutchens planted this rain garden, a garden built to absorb rainwater, shortly after she and her husband moved into their Ballwin home in 2004.

“We filled everything with native landscaping, trees, shrubs and minimized the amount of turf because turf basically allows all the stormwater to run off,” she said.

Ballwin resident Clarice Hutchens stands in front of her rain garden in December 2016.
Credit Eli Chen | St. Louis Public Radio
Ballwin resident Clarice Hutchens stands in front of her rain garden.

Hutchens, an environmental scientist, learned in school and through workshops that stormwater catches much of the debris and chemicals that we put into our environment, and carries them into lakes and streams. Excessive stormwater also can worsen flooding.

“We take our dogs for walks every day in Castlewood Park,” Hutchens said. “And it doesn’t even take a very big rain and you see the banks bursting.”

She’s not just concerned about local flooding. As someone who’s traveled a lot to coastal areas and enjoys scuba diving, she’s seen how sea level rise has caused shoreline erosion and damage to communities. She’s read that part of the problem are the impenetrable surfaces we’ve placed in our urban environments, such as roads, sidewalks and lawns.

Her concerns have led her to wonder what’s being done locally to promote rainscaping, or reducing stormwater runoff through the use of rain gardens, rain barrels, porous pavement and other types of green infrastructure.

“I don’t know why that question hit home,” Hutchens said. “I felt like I need to be an active citizen and help raise awareness about it.”

What Clarice Hutchens' rain garden looks like in the warmer months.
Credit Eli Chen | St. Louis Public Radio
What Clarice Hutchens' rain garden looks like in the warmer months.

Stormwater runoff is a shared responsibility

In St. Louis, the Metropolitan Sewer District maintains the metro area’s stormwater system. It enforces stormwater regulations and when there’s new development, the agency will evaluate the new construction’s impact on runoff.

However, the MSD does not have complete authority over stormwater runoff.

“No one entity completely has control over stormwater management,” said Lance LeComb, spokesperson for the Metropolitan Sewer District. “The individual municipalities control their own destinies. They are their own floodplain managers.”

As a part of its Project Clear program to make major improvements to sewage and wastewater infrastructure, MSD has built rainscaping projects, which include a large rain garden in north St. Louis and the multiple gardens are the Cortex Innovation District. The agency was required to spend $100 million on green infrastructure, as a part of a 2011 settlement of a Clean Water Act lawsuit with the Environmental Protection Agency and the Missouri Coalition for the Environment.

The MSD's rainscaping project at the Cortext Innovation District.
Credit Provided by the Metropolitan Sewer District of St. Louis
The MSD's rainscaping project at the Cortext Innovation District.

Such projects can help address the problem of sewage overflows. A study released by Climate Central last fall noted that the major flooding that occurred in the St. Louis region last winter caused a sewage overflow of about 200 million gallons, one of the largest in the United States over the last couple years.

“It helps us on the wastewater side of our business because it’s holding back rainwater from getting into the sewer system that handles wastewater and stormwater through the same pipe,” LeComb said.

But LeComb also noted that the MSD has little control over where development takes place. Decisions over where to build can have the greatest influence on how much stormwater runoff and flooding affects residents.

Reducing runoff means cleaner water

At the College School in Webster Groves, Karla Wilson, a project manager at the Deer Creek Watershed Alliance, a Missouri Botanical Garden project, pointed at features of the parking lot that keep rainwater from running off into the street. The lot is covered in permeable pavers, which look similar to cobblestone.

“[Rainwater] runs in between the holes in the pavers and gets absorbed into the ground,” Wilson said.

The water can also run off and become absorbed by the prairie grasses along the edges of the parking lot. 

The MSD's Old North rain garden project.
Credit Provided by the Metropolitan Sewer District of St. Louis
The MSD's Old North rain garden project.

Deep-rooted native plants, such as prairie grass, work the best for capturing rainwater and improving water quality.

“Native plants are more adapted to this climate and environment, so they require less inputs, less watering but more importantly, less pesticide and fertilizer,” Wilson said.

Pesticide and fertilizer in runoff can introduce excessive amounts of nutrients, such as nitrogen and phosphorus, into lakes and rivers. That can taint our water supply, cause fish kills and create dead zones.

Wilson’s organization is focused on improving water quality in the Deer Creek Watershed, which covers 22 municipalities in the St. Louis area. Single family households occupy 71 percent of the watershed, so the Deer Creek Watershed Alliance has made outreach to residents a major priority.

“The idea is to really change the way people think about landscaping their yards,” Wilson said. “Most people think that a lawn is what a yard should look like.”

Rain gardens can curb a little flooding

A rain garden can help prevent low levels of flooding, the kind a resident who routinely experiences flooding in their basement sees after a rain, said Wilson. Most storms that come through St. Louis typically deliver a little over an inch of rain over the course of 24 hours. A garden full of native perennial plants could potentially capture the first inch of rainfall.

A three- to five-inch rainfall, however, could overwhelm the garden.

“We don’t like for people to think that rainscaping is going to be sufficient to address regional flooding,” Wilson said. “But it could be a partial solution.”

Ordinances to restrict building in floodplains would be the best solution to that, Wilson said.

LeComb agrees.

“Rain gardens aren’t the silver bullet,” LeComb said. “They are a part of the many pieces that need to come together to form a solution to the challenge of dealing with stormwater.”

A rooftop rain garden at SWT Design, a landscape architecture firm in St. Louis.
Credit Eli Chen | St. Louis Public Radio
A rooftop rain garden at SWT Design, a landscape architecture firm in St. Louis.

Affordable, but public funding is limited

According to the Deer Creek Watershed Alliance, it costs about $10 to $15 per square foot to build a rain garden. Hutchens said her rain garden was “inexpensive” and didn’t cost more than “a trip to Lowe’s.” After the first year, she barely needed to maintain it beyond some minimal weeding, since the garden was adept at fertilizing itself and retaining water.

Two years ago, the sewer district began offering small grants to encourage homeowners, businesses and organizations to do rainscaping on their properties. However, the financial assistance only is available to residents in north or eastern St. Louis, and small parts of St. Louis County. 

“It’s our hope down the road that we can get a change to our stormwater funding formula,” LeComb said. “Then we can perhaps introduce grants for the entire district and all of our customers.”

The MSD’s rainscaping grants are largely funded by private property taxes.

Rainscaping Resources

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This project is part of our collaborative reporting project Curious Louis. What do you wonder about St. Louis or its people that you would like St. Louis Public Radio to investigate? Ask your question in the form below. (If the form doesn't load, find it here.)


Eli is the science and environment reporter at St. Louis Public Radio.