Sea level rise effect on inhabited river-deltaic estuarine islands in the tropical monsoon regions in the Indian Sundarbans

Coastal deltaic landscapes under tropical monsoon regions are sensitive to sea level changes exacerbated by human interventions. In low-lying areas, rising relative sea level (RSL) and such interventions are intensifying geohazards like coastal erosion and land subsidence. This study examines erosion and flooding risks in the Sundarbans mangroves along the Bay of Bengal using statistical models – Endpoint Rate (EPR) and Shoreline Change Envelope (SCE) incorporated in Digital Shoreline Analysis System (DSAS). “Patharpratima Block” comprises thirteen estuarine islands, part of the delta formed via confluence of three rivers, the Ganges, the Brahmaputra, and the Meghna. EPR and SCE were applied via geospatial modelling, and remote sensing to evaluate coastal changes between 1990-2020. Results show the shoreline undergoes gradual to significant changes due to fluctuating erosion and deposition, impacting local residents. Surendranagar and Dhanchi were identified as the most vulnerable, followed by moderately vulnerable Lothian. With observed RSL rise, shoreline dynamics were modeled using EPR and SCE to estimate past and future changes. Additionally, the Sundarban Reserve Forest (SRF), the world’s largest mangrove forest, is at risk of disappearing. The region’s population has increased, while total area has shrunk due to erosion. Urgent sustainable measures are needed to prevent biodiversity loss and displacement of livelihoods into environmental refugees.