MULTI-TEMPORAL ASSESSMENT OF DELTAIC ISLANDS IN THE HUGLI AND MEGHNA ESTUARIES

Abstract

Understanding of coastal erosion and accretion processes in dynamic estuarine contributes in coastal risk mitigation strategies. The island-area dynamics across multiple estuaries within the same delta region requires significant research attention. This study analyses shoreline changes characteristics of Nayachar and Ghoramara islands (Hugli estuary, India) and Hatia and Nijhum islands (Meghna estuary, Bangladesh) of the Ganga–Brahmaputra Delta using Landsat-MSS, TM, and OLI data from 1973 to 2024. Multi-temporal island shoreline overlay analysis was applied to quantify island area dynamics at each time step for a period of 51 years. Manual digitalization from the satellite images has done to quantify the shoreline accretion and erosion rates. Linear extrapolation was applied to project future island-area trends to 2044. In the Hugli estuary, Nayachar shows overall accretion while Ghoramara erodes from all directions. In the Meghna estuary, Hatia faces erosion in the northern portion, while Nijhum shows northward area gain through sediment deposition. Accretion rates for Nayachar and Nijhum (0.57 km²/yr and 0.41 km²/yr) exceed projected sea-level rise of 0.43–0.84 m by 2100 under IPCC SSPs, yet any SLR increase will raise flood frequency. The erosion rates of Ghoramara and Hatia (0.09 km²/yr and 1.52 km²/yr) signal severe vulnerability to future sea level rise, storm surge and flooding. If historical trends continue, island areas by mid-21st century will be 67.40, 40.67, 287.98 and 1.53 km² for Nayachar, Nijhum, Hatia and Ghoramara respectively; actual areas under SLR will be smaller. The study suggests shoreline protection zoning for eroding islands, mangrove restoration and integrated island specific management as immediate priorities.