Groundwater overuse is a critical driver of the problem, said Susanna Werth, assistant professor of geosciences who co-authored the paper published Oct. 28 in Nature Sustainability.
"When cities pump more water from aquifers than nature can replenish, the ground quite literally sinks," Werth said. "Our study shows that this overexploitation of groundwater is directly linked to structural weakening in urban areas."
Using satellite radar data from 2015-23, the research team assessed differential ground sinking, or subsidence, in New Delhi, Mumbai, Chennai, Kolkata, and Bengaluru, covering more than 13 million buildings and home to nearly 80 million people.
Results revealed that 878 square kilometers of urban land, or about 339 square miles, is sinking, with nearly 1.9 million people exposed to subsidence rates greater than 4 millimeters per year.
The study estimates that 2,406 buildings in New Delhi, Mumbai, and Chennai are already at high risk of structural damage. If current subsidence trends continue, over 23,000 buildings could face a very high risk within the next 50 years.
Land subsidence compounds the threats from flooding and earthquakes. When the ground beneath a city sinks unevenly, it weakens foundations, damages utility lines, and amplifies structural vulnerability.
"The silent strain we see today could lead to tomorrow's disasters if cities do not adapt their infrastructure and groundwater management policies," said lead author Nitheshnirmal Sadhasivam, a graduate student working with Werth.
The study demonstrates the value of cutting-edge satellite techniques in preventing tragedy, according to co-author and Associate Professor Manoochehr Shirzaei.
"Our research shows how satellite-based ground mapping techniques can reveal risks that are otherwise hidden until collapse occurs," said Shirzaei. "Investing in adaptation now, through groundwater regulation, resilient design, and proactive monitoring, will save lives and resources in the long run."
The findings extend beyond India, warning that subsidence-driven building damage is an emerging global urban challenge. As more cities depend on stressed aquifers and expand rapidly, subsidence will continue to erode infrastructure resilience worldwide.
Research Report:Building damage risk in sinking Indian megacities
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