Chennai among coastal cities most at risk from rising sea level, finds study

Chennai and other cities along India’s eastern coast face heightened risks from sea-level rise, according to a new study by scientists from Anna University and the Tamil Nadu Green Climate Company. 

The study, published in Theoretical and Applied Climatology recently, shows that the Bay of Bengal is experiencing accelerated sea-level rise compared to the Arabian Sea, placing Tamil Nadu’s capital and surrounding coastal districts in a high-risk zone.

The study, led by A. Ramachandran, professor emeritus at the Centre for Climate Change and Disaster Management, Anna University, analysed tide-gauge and satellite altimetry data from 1992–2023 and used SimCLIM AR6 models incorporating CMIP6 data from 39 global climate models. Projections show sea-level rise along India’s coastline could range from 25.72 cm under low-emission pathways to 110.2 cm under high-emission scenarios by 2100.

The findings indicate significant regional variations. In the Arabian Sea, sea-level trends were relatively steady, ranging from 0.97 mm per year at Mumbai to 2.75 mm per year at Mormugao. By contrast, the Bay of Bengal displayed greater variability, with rates from –0.17 mm per year at Tuticorin in southern Tamil Nadu to 3.82 mm per year at Diamond Harbour in West Bengal, south of Kolkata. Tuticorin’s negative rate was linked in the study to land uplift in the area, even as other parts of Tamil Nadu continue to see saltwater intrusion and coastal erosion.

Tamil Nadu’s long coastline makes it particularly vulnerable. The 2004 Indian Ocean tsunami exposed the fragility of the state’s shores, causing large-scale destruction and long-lasting socio-economic impacts. Today, rising seas and climate variability are intensifying these challenges. Saltwater intrusion into groundwater aquifers in Tamil Nadu has been reported as a growing problem, threatening drinking water and agricultural productivity. Coastal erosion has also been noted in several stretches, adding to risks faced by fishing and farming communities.

Cyclone records between 1991 and 2023 further underline the vulnerability of the Bay of Bengal coast. The region accounted for 62 cyclonic systems, compared with just 9 in the Arabian Sea. Of these, 67.3% of severe cyclones occurred in the post-monsoon season, intensifying storm surges and flooding risks for low-lying coastal settlements in Tamil Nadu and neighbouring states.

The study identifies the Sundarbans, Visakhapatnam, and Tamil Nadu’s eastern districts as areas where risks will intensify, threatening ecosystems, agriculture, and freshwater supplies.

The authors stress that adapting to sea-level rise requires integrated strategies, combining engineering interventions, nature-based solutions such as mangrove restoration, and community-based resilience measures. They say that effective mitigation will depend on region-specific approaches that account for the distinct conditions of the Bay of Bengal and the Arabian Sea.