New Green Infrastructure Mitigates Stormwater Runoff

Chicago, like many other U.S. cities, is trying to cope with one of the many problems caused by worsening climate change—increasingly intense downpours that inundate the urban landscape with stormwater that sometimes overwhelms sewer systems designed many years ago.

In contrast with the hurricanes that threaten to overwhelm the shorelines of coastal cities, inland rainstorms cause a phenomenon called urban flooding, in which excess rainfall causes sewers to overflow, flooding streets and homes around them.

“The problem in many Great Lakes cities like Chicago is that they’re flat and old,” says Drew Williams-Clark, managing director for urban resilience for the Center for Neighborhood Technology, a Chicago-based national organization that aims to improve cities’ sustainability, resilience, and quality of life. “We have combined sewers where sewage and rainwater both flow. Often, they were based on rainwater modeling that is now completely outdated because of climate change.”

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The Chicago area, which must contend with rising water levels in Lake Michigan as well as increasingly intense rainstorms, has more-robust gray infrastructure than many other cities. Its sprawling Tunnel and Reservoir Plan—also known as the Deep Tunnel Project—has taken decades to carry out at a cost of about $3.8 billion and includes 109 miles (175 km) of underground tunnels as big as 33 feet (10 m) in diameter. The system will have a combined stormwater and sewage capacity of 17.5 billion gallons (66.2 billion liters) by 2029. But even that massive amount of gray infrastructure is hard pressed to keep up with the escalating intensity of rainfall.

In Cook County, where Chicago is located, the Metropolitan Water Reclamation District of Greater Chicago has turned to an additional solution. Fourteen miles (23 km) outside Chicago in the village of Harwood Heights, for example, the district has helped fund the construction of several green alleys, with permeable pavement that allows rainwater to seep through spaces into the ground instead of staying on top, as it would with conventional asphalt.

Green infrastructure, as such projects are called, aims to capture and store water close to where it falls. Instead of massive pipes, tanks, tunnels, and reservoirs, elements of green infrastructure are smaller and more numerous, scattered across an urban area. In addition to permeable pavement, such infrastructure ranges in form from rain gardens and green rooftops to bioswales—drainage channels planted with vegetation.

While green infrastructure is not a completely new idea—the city of Chicago, for example, has been repaving alleys with permeable surfaces for years—the metropolitan water district is working to expand its reach across suburban areas that use its sewer system as well. The district provides $5 million each year in competitive grants to local governments to build green infrastructure, according to its annual budget documents. The district has completed or is currently planning 60 projects, including 21 to be completed this year, says Allison Fore, a public and intergovernmental affairs officer with the district. In addition, the district partners with the Chicago Public Schools, the city’s Department of Water Management, and other groups on the Space to Grow program, which has renovated 25 local schoolyards and added permeable surfaces to manage rainfall.

Other U.S. cities are also increasingly turning to green infrastructure to augment conventional stormwater systems, often by funding neighborhood and environmental groups, as well as requiring developers to include it in projects. Though implementing smaller, distributed green infrastructure projects costs far less than building gray infrastructure, it requires creative thinking and innovative funding mechanisms. But proponents note that green infrastructure provides benefits that go beyond controlling stormwater. Sites devoted to infrastructure can double as recreational space or traffic barriers, or help improve an area’s appearance. Maintaining green infrastructure can provide jobs for residents and promote economic equity in disadvantaged neighborhoods, as well as improve the quality of life there.

Emulating Nature to Improve Resilience

“We have to figure out how to reproduce what nature did for millennia,” says Williams-Clark. “We’re not going to be able to build enough pipes, tanks, and tunnels to get us out of this.”

The stormwater problems that cities face are tied to changes in climate that have led to increased rainfall in some regions. In a 2019 article for The Conversation website, Shuang-Ye Wu, an associate professor of geology at the University of Dayton who analyzed historical climate data from 1951 to 2013, reported that mean precipitation in the Midwest has been increasing by 2.1 percent per decade. Half of the increase has been caused by more frequent storms, and the rest is attributable to increased storm intensity. According to Wu’s modeling, rainfall across the Midwest by midcentury is likely to increase by 8 percent from 1970–2000 levels.

Often, much of the harm caused by urban flooding is suffered by less affluent and minority neighborhoods. A Center for Neighborhood Technology study of $400 million in insurance payments made for flood damage in Chicago between 2007 and 2016 found that 75 percent of the claims were paid in a handful of zip codes where 93 percent of the residents were people of color and a quarter of households had incomes below the federal poverty line.

“Generally, we should enhance the capacity of our infrastructure and strengthen our potential for resilience,” says David Strifling, director of Marquette University Law School’s Water Law and Policy Initiative. “Green infrastructure can be one piece of that puzzle. When properly installed and maintained, it reduces and slows storm-water runoff, in turn helping to manage localized flooding.”

In addition, he says, “it replenishes groundwater reserves, prevents erosion, reduces energy use at treatment facilities, lowers the temperature in urban heat islands, and reduces energy use within individual buildings through the cooling effects of green roofs and vegetative cover.”

Moriah Gelder, a civil engineer for the Chicago area’s metropolitan water district, says the green infrastructure provides two types of protection: in addition to reducing flooding in the immediate area, it also decreases the stormwater going into a combined sewer system, which can prevent overflows and flooding elsewhere in the system.

“The size, design, and location [of green infrastructure] all factor into how much flooding protection the installation can provide to nearby structures,” she says. “For example, if there is a street that often floods during a rainstorm, installing a roadside rain garden and curb cuts to allow the stormwater on the street to flow into the rain garden and soak into the ground is an ideal use of green infrastructure. Flooding on the street often means that the sewer system is full, so any stormwater we can redirect away from the sewer system will help prevent combined sewer overflows and backups of combined sewers into basements.”

Gelder notes that buildings also can be designed to more effectively use the green infrastructure around them. “A design decision such as raising the underdrain will allow more water to soak into the ground beneath a GI [green infrastructure] installation rather than be slowly discharged into the connecting sewer,” she says. That eliminates the discharge from ever reaching the sewer system, rather than just holding it back and releasing it slowly.

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Green Infrastructure Innovation

Besides Chicago, other cities are adding green infrastructure to their stormwater management strategies.

In Detroit, the Detroit Water and Sewerage Department plans to spend $50 million by 2029 to build green infrastructure projects. The agency already has completed 12 projects with the capacity to manage 61 million gallons (231 million liters) of stormwater. Detroit’s expanse of vacant lots—40 percent of the city’s 141 square miles (365 sq km) is owned or controlled by the government—offers officials plenty of locations to choose from.

One recent project in Detroit involved an $8.6 million transformation of traffic medians along Oakman Boulevard, which combines vegetation with an underground storage tank to manage 37 million gallons (140 million liters) of stormwater each year.

Valerie Strassberg, Detroit urban conservation director at the Nature Conservancy, a national environmental group that works with cities on developing green infrastructure, says such projects are increasingly woven into Detroit’s redevelopment plans for areas such as the Eastern Market neighborhood. A green infrastructure retrofit there of the neighborhood’s Sacred Heart Church, where the conservancy worked with church members to develop a rain garden in the parking lot, will keep an estimated 1.5 million gallons (5.7 million liters) of stormwater out of city sewers each year. “Sacred Heart as a community can display and demonstrate what they want their city, their community, and their neighborhood to look like into the future,” Strassberg says in a video on the project.

The conservancy also worked with Detroit’s sewage department to develop a policy, enacted in 2018, that requires developers to manage stormwater on new projects. “That changed the way development is done in the city of Detroit,” Strassberg says.

Milwaukee also has been aggressively developing green infrastructure. The Milwaukee Metropolitan Sewerage District, which has the goal of zero sewer overflows by 2035, has invested $42 million in grants to help local communities, organizations, and private developers build $85 million worth of green infrastructure—more than 600 pieces of infrastructure, and in some instances multiple elements on the same site. “These include everything from native landscaping to wetlands,” says Bill Graffin, the district’s public information manager. “These assets have the capacity to capture up to 38 million gallons [144 million liters] at any given storm event.”

One innovative Milwaukee project is Freshwater Plaza, constructed on a former foundry site, which captures rainwater off the roof of an adjacent building and filters it through rocks and wetland plants to remove finer particles of pollution, before directing it into channels and an underground cistern capable of holding 30,000 gallons (114,000 liters). Freshwater Way, a street that is home to numerous water-technology businesses, features an assortment of green roofs, bioswales, permeable pavement, and rain gardens. A rooftop vegetable garden on Tippecanoe Presbyterian Church in the city’s Bay View neighborhood is capable of managing another 2,000 gallons (7,600 liters).

ULI Report: On Safer Ground: Floodplain Buyouts and Community Resilience on Knowledge Finder.

Working with Neighborhoods

Buffalo’s decline in population since the early 20th century, when it was the eighth-largest U.S. city, has given it an advantage in dealing with stormwater. “They built an infrastructure for a city as large as Chicago,” says Oluwole McFoy, general manager of the Buffalo Sewer Authority. Even today, “we have a very robust system capacity.”

But even those pipes are challenged by the downpours Buffalo now experiences. “We’ve seen in recent years a number of 100-year events,” McFoy says. “For us, green infrastructure is a great way to capture and treat that water on site and keep it out of the sewer system in the first place.”

Buffalo also has used properties where deteriorating houses were demolished 20 years ago and now serve as locations for green infrastructure. “We’ve taken those lemons and turned them into lemonade,” he says.

One important part of Buffalo’s strategy is going into neighborhoods and consulting residents about the sort of projects they would like to see, and then getting them to participate in the development. “Normally in public works, when we go in, we’ve already got the blueprints,” McFoy says. “But this time we said, ‘We’ve got blank sheets of paper. We think this is the proper neighborhood to locate the green infrastructure. Now tell us where and what you want to see.’”

In Buffalo’s Willert Park neighborhood, officials consulted with residents on developing green infrastructure at the Pratt Willert Community Center, which included redirecting stormwater runoff from the parking lot into a rain garden and installation of a storage basin beneath it to hold the water before slowly releasing it into the soil. That project, combined with a rain garden at the nearby JFK Community Center, will keep 14,000 gallons (53,000 liters) of stormwater out of sewers during a typical rainstorm. To help build community ownership, local schoolchildren were invited to join in the design process. “We taught them about the plantings, filtration, absorption, and had them do the layout.” McFoy says. “Then we brought in the equipment to do the job.”

The authority has turned to an innovative funding method for green infrastructure—a $54 million environmental impact bond, the first in which a municipal issuer included a performance incentive. Buffalo can refinance or retire the bond after year seven if it meets a performance goal of protecting at least 200 acres (80 ha) from stormwater.

On this project, Buffalo worked with an infrastructure advisory team that helped Buffalo find the financing, led by Environmental Consulting & Technology, a firm that provides support ranging from engineering and scientific expertise to project management for environmental issues. Enabling municipalities to scale up their distributed green infrastructure efforts is crucial for coping with climate change, says Sanjiv K. Sinha, the firm’s senior vice president, chief sustainability officer, and water resources national director.

“The aggregation of projects leads to faster delivery, lower costs, and more immediate water quality and other benefits,” he says. “These infrastructure investments can be made in a manner that is also conducive to equitable economic growth of a city/town. My team is focused on similar larger-scale implementation and financing projects across the Great Lakes region.”

In the Chicago area, the Nature Conservancy and the Metropolitan Planning Council are involved in a different sort of effort to promote green infrastructure. In 2020, they launched StormStore, a pilot program that enables developers to trade credits for stormwater management features that they are required to put on their properties. The goal is to ensure that green infrastructure is built where it is needed most rather than just to comply with regulations.

Sinha sees a strong economic argument for cities to use more green infrastructure. “When you take all the factors into consideration, dealing with the rain where it falls is more cost-­effective, as opposed to spending a lot more money to build a system to take it somewhere else.”

Learn more about the future of urban living at the 2021 Fall Meeting.

PATRICK J. KIGER is a Washington, D.C.–based journalist and author.