A new study on this developing global urban crisis comes as Indian megacities face the brunt of subsidence-related building destruction. A team of researchers from Virginia Tech worked to gauge ground-sinking in New Delhi, Mumbai, Chennai, Kolkata and Bengaluru. To conduct their analysis, they used satellite radar data from 2015-2023. This new research study paints a disturbing picture of subsidence across the country. If these trends persist, over 23,000 of their buildings could be at risk of severe damage in just the next 50 years.
Over-extraction of groundwater has become a significant driver of this subsidence. Meanwhile, major metropolitan areas—like Atlantic City, Norfolk and New Orleans—are drowning at unprecedented speeds. More than 1.9 million residents experience subsidence rates that go over 4 millimeters per year. As much as 878 sq. km—roughly 339 sq. mi—of land that used to be the city is sinking under its former surface. This dangerous trend is a serious risk to our nation’s infrastructure.
Key Findings of the Study
The research team evaluated over 13 million structures in all five megacities. Their results showed that 2,406 buildings in New Delhi, Mumbai and Chennai are at high risk of irreversible structural damage. This risk is a direct result of continuous subsidence impacting these communities. These lives are at risk, and so too is the economic vitality of these areas.
Nitheshnirmal Sadhasivam, a PhD student and the study’s first author, stressed the need for immediate steps.
“The silent strain we see today could lead to tomorrow’s disasters if cities do not adapt their infrastructure and groundwater management policies.” – Nitheshnirmal Sadhasivam
The significance of the study goes beyond these short-term hazards. It calls for cities to rethink their approaches to infrastructure development and groundwater management in order to safeguard against potential disasters in the future.
Groundwater Overuse and its Consequences
Groundwater overextraction is a critical factor underneath the subsidence currently being felt in these developed communities. Capital cities such as New Delhi and Mumbai draw down aquifers faster than they can be replenished. Consequently, the ground is literally sinking below their feet.
Assistant Professor Susanna Werth, the third co-author of the study, elaborated on this common occurrence.
“When cities pump more water from aquifers than nature can replenish, the ground quite literally sinks.” – Susanna Werth
This environmentally destructive practice leads to irreversible structural damage. It further jeopardizes the quality of life for millions of other residents who rely on these waters for drinking, bathing, and fishing.
The Role of Satellite Technology
The research highlights the importance of state-of-the-art satellite methods in predicting and mitigating subsidence risks. With the use of next generation ground mapping radar technologies, scientists can identify weaknesses that would remain hidden until total failure sets in.
He emphasized the need for proactive approaches to dealing with these issues.
“Our research shows how satellite-based ground mapping techniques can reveal risks that are otherwise hidden until collapse occurs.” – Manoochehr Shirzaei
Furthermore, he stressed the importance of proactive measures in addressing these challenges.
“Investing in adaptation now, through groundwater regulation, resilient design, and proactive monitoring, will save lives and resources in the long run.” – Manoochehr Shirzaei