Role of Anthropogenic Activities on the Riverbank Instability: A Geospatial Analysis on Part of the Bhagirathi-Hugli River, India

Anthropogenic activities have an assumed impact on riverbank dynamics. In West Bengal, the Bhagirathi-Hugli River is a significant river that is presently being affected by human interference. The study attempts to assess the influence of human activities on the riverbank stability of the Bhagirathi-Hugli River, West Bengal, India. For this investigation, topographic maps and satellite data of different times with the associated field survey are used to verify bank erosion, Normalized Difference Vegetation Index (NDVI), Normalized Difference Build-up Index (NDBI), and Modified Normalized Difference Water Index (MNDWI) as land use/land cover change using remote sensing (RS) and GIS application. Riverbank erosion and accumulation were determined from successive alterations in riverbank line locations over several periods from 1972/1973 to 2017. The river erosion and deposition statistics showed that 22.45 km2 of land was lost on the left bank, while about 19.10 km2 of land was gained on the right bank during the assessment period, indicating that the river is moving toward the left bank. The bank erosion rate was reduced from 1.67 to 0.71 km2/year within the study areas. The population density increased sharply from 1981 to 2011. There is a strong linear negative relationship between NDVI and NDBI and between MNDWI and NDBI, confirming the dominant human activities in these areas. Other anthropogenic activities, such as the rapid growth of brick kilns and the removal of soil from riverbanks, also affect the character of bank stability.