Recent past and future projection of sea level: a case study of Puri, Chennai, and Visakhapatnam

Sea-level rise (SLR) poses an increasing threat to coastal areas, especially along the Bay of Bengal, where there are high people densities and essential infrastructure. This study analyses historical and future projection of sea-level for three Indian coastal cities, Puri, Chennai, and Visakhapatnam, utilizing satellite altimetry, tide-gauge data, and CMIP6 models. Historical trends indicate a distinct acceleration, with recorded rates surpassing 4 mm/yr throughout the study region and a significant rise post-2010. Chennai and Visakhapatnam exhibits rise of about 4.5 mm/yr during 1995–2020, resulting from a confluence of global factors and local subsidence, whilst Puri shows relatively lower than other two metropolises (4 mm/yr) yet substantial developments. Future projection suggests that under high-emission scenarios (SSP5-8.5), sea levels may increase by approximately 1.0 m by 2100, jeopardizing vast urban, economic, and biological systems. A Dynamic Vulnerability Index (DVI) is estimated to evaluate city-level vulnerability by incorporating indicators of danger, exposure, and adaptive capability. The results indicate that Chennai is the most susceptible city, with growing urbanization, groundwater depletion, and low-lying topography exacerbating risks. Visakhapatnam leads due to its port and industrial infrastructure, whilst Puri's cultural and tourism resources encounter site-specific yet comparatively lesser exposure. The study suggests that adaptation routes should integrate engineered defenses with ecosystem-based solutions and improved governance, while enhanced monitoring and socio-economic resilience are crucial for mitigating future risks.