Science & Nature
Chicago Among Major US Cities That Are Slowly Sinking: Study
What was once thought to be a mainly coastal phenomenon is now showing up in most major cities in the U.S. and around the world.
Scientists say land subsidence — a so-called “slow-moving hazard” — is causing Chicago’s urban center to lose around two millimeters of elevation every year. In other words, Chicago is slowly sinking.
A May paper published in Nature Cities found that at least 98% of Chicago’s city area is affected by land subsidence, with 10% sinking at a rate faster than three millimeters — around one-tenth of an inch — per year.
Manoochehr Shirzaei, one of the study’s authors, attributed land subsidence in Chicago to glacial isostatic adjustments — the rising and settling of land after glaciers melted — and groundwater extraction from humans.
“Chicago has a long history of groundwater extraction,” Shirzaei said. “ … The land and the aquifer system responds to that rapid overextraction of the groundwater — and that is adding to that natural effect.”
Long-term pumping has lowered the groundwater level by as much as 900 feet since 1864, according to the U.S. Geological Survey.
Researchers say coastal and lakeside cities facing subsidence are at higher risk of flooding, while landlocked cities face threats to infrastructure.
Chicago isn’t expected to see immediate impacts to its infrastructure or transit, but long-term sinking could cause structural damage if unchecked.
“One of the most harmful yet less visible effects of urban land subsidence is the potential damage to buildings, foundations and infrastructure,” the study reads. “The latent nature of this risk means that infrastructure can be silently compromised over time, with damage only becoming evident when it is severe or potentially catastrophic.”
Chicago areas most at risk of long-term infrastructure damage include River North, the Loop, the West Loop, the South Loop and along train routes.
Researchers have outlined mitigation strategies for land subsidence based on regional causes.
In Chicago, where groundwater extraction is a major factor, Shirzaei recommends managed aquifer recharge — that is, returning excess water and rainwater to the ground.
He cited Orange County, California, as a leading example of the approach.
“Instead of letting water run off, you can collect it, minimally treat it, and put it back under the ground,” Shirzaei said. “California suffers from severe droughts. … Orange County does not even feel that pressure of the drought, because they constantly put water under the ground and when they need it they have it, and it slows down and actually reverses the land subsidence.”
Chicago does not have a formal managed aquifer recharge program. But the city has prioritized water reclamation in the form of projects like the Green Infrastructure Partnership Program and the Tunnel and Reservoir Plan.
Shirzaei said city and state governments do not shine enough light onto land subsidence.
“Land subsidence, by nature, is a slow but steady hazard, and often, especially in democratic countries like our country, decisions are made from election to election,” Shirzaei said. “Managed aquifer recharge is the solution, the remedy that results in amazing outcomes in 1,000 years from now. So policymakers often don’t look that far into the future.”
Note: This article was updated at 2:45 p.m. on Sept. 17, 2025, to clarify and add more detail about the drop in the region’s groundwater levels. A previous version referred to that level as elevation.
