Spatio-temporal assessment of shoreline retreat and future vulnerability of Mousuni Island, West Bengal, India

Abstract

Shoreline retreat poses a significant threat to coastal systems, that are highly vulnerable to climatic and hydrodynamic variability. However, long-term studies linking past changes with future shoreline projections are still limited in many deltaic regions. This study evaluates the spatio-temporal shoreline dynamics of Mousuni Island, West Bengal, over the past four decades (1980–2023) using multi-temporal Landsat imagery and DSASbased coastal vulnerability assessment framework (DSAS 5.0). Shoreline dynamics were analysed along 1541 transects using five indicators, such as End Point Rate (EPR), Linear Regression Rate (LRR), Weighted Linear Regression (WLR), Net Shoreline Movement (NSM), and Shoreline Change Envelope (SCE). The analysis revealed erosion as the dominant process, affecting nearly 90 % of the island’s perimeter. The mean shoreline retreat was 􀀀 4.36 m/yr, with extreme erosion rates reaching 􀀀 23.55 m/yr in the southern and northwestern high-risk zones, whereas limited accretion occurred in northeastern pockets, with a maximum gain of + 2.81 m/yr. Between 1980 and 2023, Mousuni Island lost approximately 19.3 % of its land area, with peak erosion (2.28 km²) during 1990–2000. Forecasting using Kalman Filter model projects further shoreline retreat of 500–700 m by 2043, reinforcing the island’s high vulnerability under sediment deficit, cyclonic pressure, and declining vegetation buffers. The model provides robust estimates, though these include uncertainty related to data resolution and natural variability. Model validation confirmed WLR as the most reliable metric for long-term shoreline prediction. The study’s novelty lies in integrating historical erosion patterns with future risk projections, providing a replicable framework for deltaic island vulnerability assessment. These findings offer valuable insights for nature-based solutions, strategic embankment design, and the development of climate-resilient coastal management frameworks.