Richmond Hill, Canada - 28 October 2025 — Across many of the world's fastest-growing cities, demand for water has outpaced what rivers and reservoirs can provide. This has increased dependence on groundwater and placed heavy strain on underground reserves. Climate change has also worsened the problem by disrupting rainfall and causing surface water to dry up more quickly. Yet each time water is pumped from underground, it removes the support that keeps the ground stable, putting overlying structures at risk of damage.
A new study published in Nature Sustainability, finds that gradual land subsidence poses a growing threat to buildings across India's largest cities. The analysis led by Dr. Manoochehr Shirzaei , the Chief Scientist of UNU-INWEH's Global Environmental Intelligence Lab, shows that over 2,400 structures in New Delhi, Mumbai, and Chennai are already at high risk of damage. It also warns that if current trends continue, more than 23,000 buildings across India's five megacities could face very high risk of structural damage in the coming decades.
"You can think of land subsidence as the Earth's response to our growing pressure on its surface and subsurface systems," said Shirzaei, who is also an associate professor at Virginia Tech. "It starts quietly, with the ground sinking by just a few millimetres each year, but when combined with extreme events such as floods or storms, it amplifies their impact by increasing the vulnerability of structures."
The study explains that land subsidence is largely linked to falling pressure in underground aquifers as groundwater is withdrawn faster than it can be replaced. In India, this problem is intensifying with population growth and rapid urban expansion, while changing monsoon patterns further limit the natural recharge of these underground reserves.
"In many places around the world, the irreversible damages to groundwater resources are orders of magnitude greater than what we have done to surface water resources," said Professor Kaveh Madani , Director of UNU-INWEH. "But such damage remains invisible and unnoticed until the sinking land makes our cities unsafe."
The authors call for a preventative approach that combines research, mitigation, adaptation, and technology to strengthen infrastructure resilience. They emphasize that reducing groundwater extraction, improving surface water management, promoting groundwater recharge, and conserving soil and vegetation are essential to protect cities and their inhabitants from the growing risks of land subsidence.
Key Findings:
878 km² of land across five Indian megacities is subsiding.
About 1.9 million people live in areas sinking faster than 4 mm per year.
2,406 buildings in Delhi, Mumbai, and Chennai are already at high risk of structural damage.
If current subsidence continues for the next 50 years, up to 23,529 buildings in Chennai, Delhi, Mumbai, Kolkata, and Bengaluru could face very high damage risk.
Find the publication here:
Sadhasivam, N., Ohenhen, L., Khorrami, M., Werth, S. & Shirzaei, M. (2025). Building damage risk in sinking Indian megacities. Nature Sustainability. doi.org/10.1038/s41893-025-01663-0
