2,400 buildings in Chennai, Mumbai, Delhi face a high sinking risk, warns study

A new study published in Nature Sustainability warns that India’s largest cities are slowly sinking. Using eight years of satellite radar data, researchers found that parts of Delhi, Mumbai, Chennai, Kolkata and Bengaluru are subsiding due to groundwater extraction and soil compaction, a process where the ground compresses as water is drawn out from underground layers.

Land subsidence, or the gradual sinking of the ground, occurs when underground water is pumped faster than it can be naturally replenished, causing soil and rock layers to compress.

The study mapped 878 square kilometres of land showing signs of subsidence and found that nearly 1.9 million people are exposed to areas where the ground is sinking faster than 4 millimetres each year. More than 2,400 buildings across Delhi, Mumbai and Chennai are at high risk of structural damage from ongoing land subsidence.

City-level projections show that Chennai and Delhi could be the worst affected, followed by Kolkata, Mumbai, and Bengaluru. The paper projects that more than 23,000 buildings could face a very high risk of structural damage within the next 50 years if current trends continue.

Although less than 5% of urban areas fall under high-risk zones, these tend to be densely populated neighbourhoods, making the potential damage disproportionate.

“Our motivation to study land subsidence and...

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