The study will map vulnerable stretches along Mumbai’s 149-km coastline, identify populated areas that could face flooding and examine how coastal development, land-use changes and changing climate patterns have affected the city’s risk.
The assessment is currently underway and the report is expected to be released next year.
The exercise comes after a recent United Nations report warned that global sea levels rose by a record 5.9 mm in 2024. The report also projected at least 0.5 metre of sea-level rise by 2100, even if countries take strong steps to reduce emissions. In a worst-case scenario involving instability of the West Antarctic ice sheet, sea levels could rise by as much as two metres.
A senior civic official involved in the assessment said Mumbai’s coastline has changed significantly over the past five years, making a fresh study necessary.
The Coastal Road has been developed along the western coastline, with more than 100 hectares of land reclaimed from the Arabian Sea. On the eastern side, salt pan lands have been identified for development. Changes in land use across the city have also altered the coastal landscape.
Unlike the UN report, which examines sea-level rise globally, the BMC’s new study will focus specifically on Mumbai. It will examine local factors that increase coastal vulnerability, estimate future sea-level rise and identify people living close to the shoreline who could be at risk.
The BMC’s first Mumbai Climate Action Plan, released in 2022, had already identified coastal flooding, rising pollution, loss of green cover and increasing urban heat as major climate risks.
The plan had also projected that around 80% of Mumbai’s island city could be submerged by 2050.
Scientists have linked rising sea levels to global warming and increasing sea surface temperatures. The 2022 climate action plan noted a gradual rise in sea surface temperatures in the Arabian Sea over the previous two decades.
Raghu Murtugudde, emeritus professor at the University of Maryland and visiting professor at IIT Bombay, said warming in Europe and West Asia was also contributing to higher temperatures in the Arabian Sea.
He said rainfall patterns have become more unpredictable in recent years, with Mumbai receiving above-normal rainfall. Heavy rain combined with high tides can increase the risk of flooding and inundation in the city.
Oceanographer and climate scientist Roxy Mathew Koll of the Indian Institute of Tropical Meteorology said Mumbai’s geography makes it particularly vulnerable.
According to Koll, rapid development, concretisation and changes in land use have reduced floodplains and restricted rivers. He cited the development of Bandra Kurla Complex on former mangrove land and the narrowing of the Mithi River due to roads and encroachments.
Koll said Mumbai’s flooding is not only a climate issue but also a city planning and management problem.
He stressed the need to protect mangroves and coastal wetlands. These natural areas help absorb floodwater and protect the city from strong winds.
Expanding and protecting coastal wetlands could improve Mumbai’s ability to deal with rising sea levels while also providing important habitats for marine and coastal life.
The 2022 Mumbai Climate Action Plan had also recorded major changes in the city’s mangrove cover between 2008 and 2021.
According to the report, around 325 hectares of dense mangrove cover had either become sparse or changed into intertidal mudflats due to erosion and sedimentation. At the same time, mangrove density had increased across around 305 hectares.
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