Decoding spatio-temporal dynamics of river morphology: a comprehensive analysis of bank-line migration in lower Gangetic basin using DSAS

Bank-line migration in lower basins is an ongoing phenomenon in river morphology that poses an existential threat to most dwellers, who depend on riverine ecosystems for their habitat and means of subsistence. This study strives to assess the changes in the bank line of the Ganga River upstream of the Farakka barrage over the past forty-nine years by utilizing satellite imagery and geospatial techniques. The results (1973–2022) reveal that approx. 309.97 sq km of land were lost due to erosion between 1973 and 2022, while 414.94 sq km of land were gained as a result of accretion. The bank line erosion and accretion rates were 61.39 and 35.93 m per year respectively based on linear regression rate (LRR). Erosion mainly has occurred along the banks of Kaliachak III and Manikchak block, while the highest rate of accretion was found along the Kaliachak II block. Furthermore, it was found that bank-lines in the whole upstream stretch of the Ganga River moved towards the land by 189.42 m based on net shoreline movement (NSM) between 1973 and 2022, with 70% of the bank-line experiencing landward shifting. These findings are highly useful for the government in managing the river bank area and in the development of bank protection measures.