Wetland Fragmentation: How Poorly Regulated Urban Development Has Destroyed Illinois’ Natural Flood Control

By: Caitlin Federici

The taming of the historic swamplands around Chicago fragmented and irreparably damaged the Illinois River’s natural flood control, wetlands. Every year, once the snow begins to melt and Chicago paints its river green Chicagoans know that construction season is just around the corner. Construction around the Chicago area has always been complicated. Chicago’s very existence is often understood as an engineering miracle.

This massive metropolis was constructed atop a sprawling swamp.[1] The vast network of wetlands around the Chicago region made urban development exceptionally challenging due to soggy ground and relentless flooding events; it is also exactly what makes the Chicago area an attractive destination as a global hub.[2] The Great Lakes connect Chicago to the Atlantic Ocean and the Illinois River watershed connects Chicago to the Mississippi River, providing easy access to trade routes.[3] However, to make the region habitable, all that water had to be contained.

The Importance of Wetlands

Historically, wetlands covered 23% of Illinois’ landscape.[4] Many of these wetlands were located in the Illinois River watershed. The watershed begins in the northeast region of the state along the Lake Michigan lakeshore. It covers nearly half of Illinois running diagonally from the northeast corner down towards the southwestern edge. To develop the land, many of the wetlands were drained and filled.[5] Now, wetlands cover only 2.5% of Illinois.[6] Cook County has lost 40 % of its native wetlands and 85% of its marsh and swamp habitats.[7]

Wetlands are crucial for maintaining the balance of the watershed to which they belong. The unique needs of a watershed determine the natural locations of wetland habitats along it. A watershed is a geographic area where precipitation is channeled into rivers and streams so it can drain into low-lying areas known as basins. Wetlands absorb and retain excess water as it flows down from higher elevations towards the basin.[8] As the water volume in the rivers and streams shrinks, the surrounding wetlands discharge the excess water into these bodies of water.[9] This process serves two vital purposes: (1) it purifies the water by removing harmful nutrients and trapping sediments such as heavy metals and pesticides; and (2) it provides flood control for the surrounding area.[10]

In Chicago, flood control is imperative. Urban flooding has become a significant problem in the Chicago area in recent years. In fact, a 2015 report showed that “90 percent of [flood] damage claims were for locations outside the mapped 100-year floodplain.”[11] One of the main causes of flooding in Chicago is the city’s combined sewer system which is designed to store both sewage and runoff.[12] The system is often overwhelmed when it storms because the rainwater is diverted to the sewers rather than retained by the network of wetlands which no longer exist or have become so fragmented that they are no longer effective.[13]

A study on the aquatic landscape of the Chicago area shows that wetlands were once regular in distribution across the region.[14] Now, wetland habitats are clumped together and generally smaller in size than their historic counterparts.[15] This is because extensive development of the region has caused major fragmentation of what was once contiguous wetland units that worked in concert with the rest of the watershed.[16]

Inadequate Regulation Has Failed to Properly Protect Illinois’ Wetlands

In 1989 Illinois passed the Interagency Wetland Policy Act (Act) in response to a land survey which indicated only about 9% of the state’s native wetlands remained intact.[17] The Act set a State goal of zero net loss for the remaining wetlands across the state.[18] This does not mean that wetland habitats cannot be developed, but rather that state-funded construction projects must compensate for any harm caused to the impacted wetland. The Act seeks to prioritize wetland compensation that creates or expands wetlands as close as possible to the impacted wetland, but this is not mandatory.[19]

The O’Hare Airport expansion project is a great example of the questionable application of this Act by Illinois government officials. The project at O’Hare, which sits 16 miles northwest of downtown Chicago, destroyed dozens of acres of wetlands along the Des Plaines River Basin.[20] To compensate, wetland habitats in Pine Dunes Forest Preserve were restored.[21] The problem, however, is that the Pine Dunes Forest Preserve is located 36 miles north of O’Hare along the northern border of Illinois. Officials approved the location because it is part of the same river basin as the wetlands impacted by the project.[22] But this area remains largely undeveloped with much of the original landscape still intact. Additionally, because the restored wetland sits along the northern border where other functioning wetlands remain, it will not provide the location-specific flood control measures that the destroyed wetlands provided.

This system achieves net zero loss by creating or expanding wetlands in another location. While better than destroying the wetlands altogether, it is insufficient for a region prone to such consistent flooding. Furthermore, when wetland development and compensation is approved on a project-to-project basis, the cumulative impact of perpetual development in urban centers such as Chicago is likely lost in the process. One acre here and another there adds up quickly.

What we see today as fragmented and isolated wetlands were not so in times past. Human desire for convenience and luxury replaced the swamps and marshes that once dominated the Chicago landscape. We are left with a patchwork of small lakes and ponds inadequate to perform our necessary flood mitigation miracles. Our manmade replacements simply do not measure up to nature’s flood controls.

We are all responsible for adjusting our perspective on the necessity of proper wetland conservation. Tolerate the traffic, take the longer route, challenge misplaced development. The longevity of our city depends on it.




[1] Dan Egan, A Battle Between a Great City and a Great Lake, New York Times (Jul. 7, 2021), https://www.nytimes.com/interactive/2021/07/07/climate/chicago-river-lake-michigan.html.

[2] Id.

[3] Id.

[4] Sierra Club, Isolated: Illinois Wetlands At Risk, 2 (2002).

[5] M. Joseph Pasterski et al., Aquatic landscape change, extirpations, and introductions in the Chicago Region, 23 Urban Ecosystems 1277, 1281 (2020) (discussing the fragmentation of wetlands around Chicago).

[6] Sierra Club, supra note 4.

[7] Kimberly M. S. Cartier, Chicago Wetlands Shrank by 40% During the 20th Century, Eos (Sep. 23, 2020), https://eos.org/articles/chicago-wetlands-shrank-by-40-during-the-20th-century; Pasterick, supra note 4

[8] Sierra Club, supra note 4, at 5.

[9]  Id.

[10] Wetland Functions and Values: Surface and Ground Water Protection, VT Dep’t of Env’t Conservation (last visited Mar. 19, 2023) https://dec.vermont.gov/watershed/wetlands/functions/water-quality#:~:text=Wetlands%20can%20improve%20water%20quality,nutrient%20removal%20and%20chemical%20detoxification

[11] Strategies to reduce the effects of flooding in metropolitan Chicago, CMAP (last visited Mar. 19, 2023) https://www.cmap.illinois.gov/updates/all/-/asset_publisher/UIMfSLnFfMB6/content/strategies-to-reduce-the-effects-of-flooding-in-metropolitan-chicago.

[12] Caitlin Federici, Chicago is Losing its Duel with Climate Change: Water Levels Rise and Infrastructure Fails, Chicago-Kent Journal of Env’t and Energy Law (Oct. 1, 2022) https://studentorgs.kentlaw.iit.edu/ckjeel/2022/10/01/chicago-is-losing-its-duel-with-climate-change/.

[13] Id.

[14] Pasterick, supra note 4.

[15] Id.

[16] Id.

[17] Interagency Wetland Policy Act of 1989 20 ILCS 830/1-2(a) (1989).

[18] Id. at 830/1-4.

[19] Id.

[20] Sheryl DeVore, Wetland mitigation can be beneficial, but not all projects are equal, environmentalists say, Chicago Tribune (Feb. 20, 2022) https://www.chicagotribune.com/news/environment/ct-forest-preserves-wetland-mitigation-20220220-meokmnw5xvfx5gwbyua4mljpqe-story.html

[21] Id.

[22] Id.