HomeEnvironment NewsMumbai city is sinking 2 mm every year on average; China's Tianjin at 5.2 cm, says research

Mumbai city is sinking 2 mm every year on average; China's Tianjin at 5.2 cm, says research

Groundwater extraction, mining, and infra projects leading to land subsidence in Mumbai.

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By CNBCTV18.com June 13, 2022, 3:10:27 PM IST (Published)

Mumbai city is sinking 2 mm every year on average; China's Tianjin at 5.2 cm, says research
Global warming is a clear and present danger. The increase in temperature is melting ice at the poles at a faster rate. As a consequence, sea levels are rising and islands and coastal cities all across the globe are sinking inch by inch. India's financial capital Mumbai also faces this threat.


A new research, published in the peer-reviewed Geophysical Research Letters journal in March, has revealed that Mumbai is sinking by an average of 2 mm annually. However, global warming is not the only culprit. According to the study, groundwater extraction, mining, reclamation of natural wetlands, infrastructure projects and ecological disturbances is leading to "land subsidence" -- downward, vertical movement of the earth’s surface -- in Mumbai.

The study titled “Subsidence in Coastal Cities Throughout the World” reads, “Mumbai is the seventh-most populous city in the world with a population of roughly 20 million. A significant portion of the city is subsiding more rapidly than 2 mm/yr." The observation has been made after measuring the subsidence rate in Mumbai between 2015 and 2020.

Meanwhile, another research, conducted by the Centre of Studies in Resources Engineering at IIT Bombay, has identified two major subsidence areas in Mumbai -- Vasai and Wadala. This research has found a strong correlation between land subsidence, groundwater extraction, and the proximity of the area to mangrove plantations and the coastline.

“A densely populated and irregularly constructed slum area along the Ghatkopar-Mankhurd Link Road merging with the Sion-Panvel Expressway also shows subsidence in the range of 60mm over the same period,” the study adds.

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Explaining the implications of land subsidence, Sudha Rani NNV, lead author of another IIT Bombay study, said, “With sea levels projected to rise by around 1 to 1.2 metres in a high emissions scenario, we found that nearly 38 percent Mumbai’s land may be inundated during normal rainfall. This is a severe issue that has to be addressed immediately.”

Researchers have found that the combined effect of declining groundwater and high-rise buildings have made Mumbai vulnerable to “subsidence, leading to increased inundation”. Additionally, the areas prone to subsidence witness the “worst impacts of flooding and property damage”. Experts suggest fighting climate change and better urban planning as the best ways to tackle the challenge.

However, the rate of subsidence in Mumbai is significantly lower than in other countries in South Asia. For instance, Tianjin in China is the fastest sinking coastal city in the world at a rate of 5.2cm per year, according to "Subsidence in Coastal Cities Throughout the World".

The study measured land subsidence in 99 countries globally. Besides Tianjin and Mumbai, the other coastal cities that are sinking include -- Jakarta (3.44 cm per year) in Indonesia, Shanghai (2.94 cm per year) in China, and Ho Chi Minh (2.81 mm per year) and Hanoi (2.44 cm per year) in Vietnam.

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