This past April, when torrential rains caused some of the worst flooding in Illinois history, many people were asking “why?” Roads were flooded, homes were deluged, and favorite family destinations were too flooded to operate—such as the perpetually-open Brookfield Zoo, which closed down for only the third time in 100 years.

Many people in the Chicagoland area blamed their flooding on the fact that they lived near wetlands. There’s usually water in ’em, so it makes sense, right? So for Worldview’s monthly segment with EcoMyths, Jerome and I decided to invite wetlands experts to help us explore this question.

Illinois Department of Natural Resources) Wetlands in Illinois.
A quintessential Illinois wetlands area. (Illinois Department of Natural Resources)

We talked with Gary Sullivan, PhD, a senior restoration ecologist with The Wetlands Initiative and Mark Maffei, PhD, a wildlife biologist that serves on the board of the Natural Land Institute and is also a wetlands expert. Although it seems counterintuitive, we found out that wetlands actually reduce flooding!

Gary explained that wetlands, with their deep-rooted plants and absorbent soils have great capacity to take in much more water, like enormous natural sponges. About one quarter of the state of Illinois used to be wetlands including much of the Chicagoland region. As a result, Mark pointed out, many homes are built on property that used to be a wetland and therefore is naturally situated to attract water.

The way things used to work in Illinois, rain would be absorbed by both the prairies and wetlands in this region, Gary continued. In turn, he said, this water eventually would have “percolated down into the groundwater,” eventually replenishing our natural underground freshwater storage systems, called aquifers. Now that we have lost the wetlands as sponges and have replaced them with a lot of hard surfaces like roads and rooftops, the rain runs off the land much more quickly, causing flooding.

Peoria Audubon Society Ducks in Peoria make the shallow wetland area their home.
Ducks in Peoria make the shallow wetland area their home. (Peoria Audubon Society)

“We treat our (rain) water as a waste product,” commented Mark. Instead, we move rainwater into straight, fast-flowing man-made channels, rather than slow-moving natural rivers. The result is intensely loaded waterways during large rainstorms, often resulting in flooding.

One Green Thing

Gary talked about a Wetlands Initiative project in DuPage County, Spring Brook #1, in which TWI is working to restore the meandering path of the stream and the wetlands along it. In addition, upstream homeowners are getting into the act by making changes in the way they landscape to mitigate flooding.

For his part, Mark urged people to encourage their municipal legislators to make changes to the building codes to protect wetlands and acknowledge their value.

For more information on wetlands and their value, check out our full EcoMyth here.

—As part of our partnership with Worldview, this content may also appear on the Chicago Public Media EcoMyths series page.

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