Chicago flooding worsens as aging stormwater infrastructure falls short

(UI) - Flooding risks across Chicago are increasing as aging sewer and stormwater infrastructure struggles to keep pace with more intense rainfall driven by climate change. 

According to a Sun-Times/WBEZ investigation, the frequency of heavy storms has risen sharply over the past century, with some events now delivering more than 8 inches of rain in 24 hours—far exceeding the capacity of many of the city’s legacy sewer systems, which were designed to handle roughly 2 inches over the same period.

While Chicago’s Deep Tunnel system has helped reduce overflows into waterways, it has not prevented widespread basement backups and localized flooding. Combined sewer systems in many neighborhoods continue to be overwhelmed during high-intensity storm events, resulting in property damage, public health risks and recurring disruptions for residents.

The impacts are particularly severe in low-lying and historically underserved communities, Sun-Times/WBEZ reported where outdated infrastructure, limited green space and high levels of impervious surfaces exacerbate stormwater runoff and drainage challenges.

Experts say addressing the issue will require a combination of traditional and green infrastructure investments, including expanded underground storage capacity, upgraded sewer networks and increased use of permeable surfaces and stormwater retention systems.

However, these solutions come with significant cost and long timelines, leaving cities like Chicago facing growing pressure to accelerate investment as rainfall intensity continues to rise.

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