A woman walks by a rain garden in Seattle
Rain gardens can help alleviate flooding in urban areas © Hannah Letinich

Stories in Illinois

Building a StormStore™ for Cook County

A new market can help protect nature and people.

Jen Jenkins
Jen Jenkins Natural Infrastructure Project Manager for the Illinois chapter © Photo courtesy of Jen Jenkins

How Nature Can Help Reduce Flooding in Cook County Suburbs

As the natural infrastructure project manager for the Illinois chapter, Jen Jenkins spends a lot of time thinking about water. But even with all of her years of experience, she admits that she was shocked by the flooding she witnessed when she first moved to Chicago.

“I was really surprised because most of the developed areas in Cook County are not actually located in a floodplain,” she recalls. “Flooding in Cook County looks very different than other parts of our state. Instead of the catastrophic 100-year flood events we might see further south, it’s these smaller, very intense rain events that cause the frequent basement backups, inundated streets and sewer overflows that are so harmful to both nature and people.”

The kind of flooding Jen describes—and that Cook County residents brace themselves for when the spring rains arrive—are the result of too much concrete. In urban areas, roads, roofs, parking lots and other hard surfaces have replaced many of the marshes, prairies and other natural areas that soak up rainwater. The result is that during storms, the only place excess water has to go is the sewer system, which can quickly become overwhelmed.

Adding more green space, such as rain gardens, green roofs, and bioswales that incorporate native plants and trees, is one way to battle the chronic flooding that is a threat to both nature and people.  Jen and her partners at the Metropolitan Planning Council are looking to expand the use of these natural options through a new program called StormStore™.

Quote: Jen Jenkins

StormStore™ is an innovative option for Cook County that allows landowners who can store extra stormwater on their property via natural infrastructure to sell that capacity through a market.

Natural Infrastructure Project Manager

StormStore™ Brings Natural Solutions to Developers and Landowners

Here’s how it works: Development projects located in the suburbs of Cook County, such as new apartment buildings or retail spaces, are now required by ordinance to manage stormwater runoff on their sites. But on-site stormwater controls can be problematic or prohibitively costly. Through StormStore™, developers can buy credits from landowners, such as a churches or schools, that have installed rain gardens, bioswales or other natural infrastructure to store excess water.

Storm water backs up after a heavy rain.
Stormwater can overwhelm aging sewer systems after a heavy rain. © Fauna Creative

“This is a win-win for everyone,” Jen says. “Developers are able to proceed with new building plans without having to add costly control systems, landowners are able to add green infrastructure to tackle flooding in their neighborhoods and be reimbursed for their expenses and communities get added green space that benefits both people and wildlife.”

StormStore™ is currently entering a pilot phase, which will include two watersheds, the Lower Des Plaines and the Little Calumet. These two watersheds were selected by the Metropolitan Water Reclamation District (MWRD) because of their specific stormwater challenges, and they were determined to have sufficient supply and demand to support a marketplace. In addition, they include many of the communities highlighted by TNC’s Greenprint tool as priority, flood-prone areas that would benefit from the addition of more green space.

Map of Stormstore Pilot areas
Stormstore pilot projects will take place in the Lower Des Plaines and Little Calumet watersheds. © Metropolitan Planning Council

“One of the challenges we face in Cook County is that most new stormwater infrastructure is built where development is happening,” Jen explains. “So there are parts of Cook County that desperately need flood solutions but aren’t getting them. If we continue with business as usual, these inequities will only get worse. We really need better comprehensive stormwater planning across the region and we need to be innovative in how we invest in infrastructure so we can make sure that solutions are reaching the most flood-prone communities.”

The pilot will provide an opportunity to understand what conditions will make stormwater trading successful in Cook County. While TNC has experience developing similar stormwater trading markets in other cities like Washington DC, the physical and regulatory landscape in Cook County is unique.  Jen and her partners hope to learn where existing stormwater policies and incentives either succeed or fall short, as well as leverage private capital for more investment in natural infrastructure to create positive change for communities that are most vulnerable to flood risk. What they learn from the pilot will be used to improve StormStore™ to hopefully encourage more communities and developers to participate in trading in the future.

Quote: Jen Jenkins

There are parts of Cook County that desperately need flood solutions but aren’t getting them. If we continue with business as usual, these inequities will only get worse.

Natural infrastructure project manager

Natural Solutions Are Essential as Climate Change Brings Increased Risks

Programs like StormStore™ will be key as climate change brings even more intense storm events to the region—that very kind that currently overwhelm the sewer system and cause damage to home and businesses.

“Many of the neighborhoods identified by Greenprint as vulnerable to flooding are also at risk for urban heat and poor air quality, which will also be exacerbated by climate change,” Jen says. “A number of these communities don’t have access to the resources to tackle these problems. We see stormwater trading as a means to redirect investment to these parts of Cook County that need it most.”

The pilot will run for the next 5 years and Jen and her partners at MPC hope that it will lay the groundwork to set up a regional trading market that will include the rest of Cook County and maybe even beyond. For Jen, the most exciting part of the work is watching improvements grow for both nature and people.

“Many nature-based stormwater solutions include the use of trees and native plants, which offer habitat and food for pollinator species like bees and butterflies,” Jen says. “At the same time, they provide social benefits for people—like improved water quality, more green space and flood reduction.”

“When you dig into where and why urban flooding occurs in Chicago, you start exposing the inequities. I think knowing that these inequities exist and that there are communities in Cook County that are disproportionally burdened by impacts of stormwater is something we need to change and that is why this work really matters for me.”

To learn more about this project, contact Jen Jenkins at 312-580-2138 or

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