A new satellite-based study has found that several cities across India are experiencing varying levels of land subsidence. While some cities remain largely stable, the research highlights that others are witnessing noticeable ground movement, in some places at rates far higher than global sea-level rise. The study, titled ‘Vertical Land Motion and Human Exposure Across India’s Coastal Regions,’ analysed changes in land elevation using satellite radar data collected between 2016 and 2024.
Conducted by researchers from the University of Rhode Island, including Quantao Zhu, Pei-Chin Wu, Meng (Matt) Wei and Estelle Chaussard, the study examined vertical land movement along India’s vast coastline and nearby urban regions.
India has a coastline of about 7,500 kilometres and more than 200 million people live within 100 kilometres of it. As coastal populations continue to grow, understanding changes in land elevation has become increasingly important for planning cities, infrastructure and disaster management. Land subsidence can worsen the impact of rising sea levels and increase the risk of flooding in vulnerable areas. The findings show that several Indian cities are experiencing measurable subsidence, although the patterns vary significantly from place to place. Among the cities analysed, Ahmedabad recorded the most significant subsidence, with widespread ground sinking across large parts of the city. In some locations, the maximum rate was estimated at about 44 millimetre (mm) per year.
In Kakinada, researchers identified large areas affected by subsidence, with rates ranging from moderate levels to peaks of about 30 mm annually. The city lies close to the deltaic region of the Godavari River where soft sediments and groundwater extraction can influence ground stability.
Similarly, the coastal city of Kochi shows widespread subsidence across much of its urban area. The study found that land in several parts of the city is sinking at rates exceeding six mm per year, with maximum values reaching around 21 mm annually.
Other major cities also show signs of land movement, though generally at lower levels. In Kolkata, subsidence is widespread but relatively moderate, with maximum recorded rates of about 13 mm per year. A similar pattern was identified in Puducherry, where subsidence also reaches up to 13 mm annually in some areas.
In Chennai, the researchers observed mostly localised subsidence rather than city-wide sinking. Certain pockets of the city show rates of up to 11 mm per year, suggesting that the phenomenon may be linked to local conditions such as groundwater extraction or land use.Some cities appear relatively stable overall. In Visakhapatnam, most areas show little or no significant land movement, although small localised zones were found to be subsiding at rates of up to seven millimetre per year. A similar pattern was observed in Mumbai, where subsidence is limited to a few areas and does not appear to be widespread.
Beyond individual cities, the study also identified significant subsidence in several major delta regions along India’s coastline. These include the Ganges-Brahmaputra Delta in eastern India as well as the Godavari Delta, Krishna Delta and Cauvery Delta in the southern part of the country. Researches noted that the delta regions are naturally prone to subsidence because the soft sediments deposited by rivers gradually compact over time. The study notes that human activities such as groundwater extraction, drainage of wetlands, agricultural practices, heavy construction and urban development can contribute to ground sinking. “India is currently one of the largest users of groundwater in the world, and excessive extraction in some regions has been linked to land subsidence,” the study states.
The research also highlights how subsidence can compound the impact of rising sea levels. Global sea levels are increasing at an average rate of about 3.4 mm per year. “However, when land itself is sinking at a faster pace, the effective rise in sea level experienced locally can be significantly greater. In some regions, this combined effect could increase the risk of coastal flooding and waterlogging over time,” researchers explain.
The study estimates that around 207 million people live within 100 km of India’s coastline. Of these, about 27.1 million people live in districts where land is sinking faster than two mm per year. Around 8.5 million people are in areas experiencing subsidence greater than five mm annually, while approximately 3.4 million people live in zones where the land is sinking by more than ten mm each year.
Researchers say understanding vertical land movement is essential for improving long-term planning in coastal regions.