An Assessment of Riverbank Instability and Quantification of Bank Line Migration of a Foothill-Fed Transboundary River Using Remote Sensing and GIS Techniques: A Case Study of Jaldhaka River

The lateral migration of a river channel inside its valley over time is a universal phenomenon. The most prominent factors behind channel dynamics in West Bengal’s sub-Himalayan region are fluvio-geomorphological processes such as rapid valley fill deposition due to very low channel gradient and resultant migration of active channel, bank failure, and bank line migration, frequent occurrence of floodsFlood, capturing of lower courses of tributaries by trunk streams, and abandonment of tracks and avulsion. Furthermore, human activities in the form of engineering constructions (floodFlood, bridges, embankments, and so on), mining and quarrying, tea plantation and agricultural encroachment are currently emerging as a major problem that is pulverizing natural channel adjustment methods as well as channel behavior. A comprehensive effort has been made to examine the channel dynamics of this region’s Jaldhaka River over 65 years in order to reveal the nature of channel migration in terms of changes in historical bank line. This research was carried out by mapping the river channel and outlining migration patterns and oscillatory activity. The distance of river channel movement was quantified using temporal data analysisData analysis in a GISGeographic Information System (GIS) context. Periodic rates of variability in channel migration have been documented, with shorter periodic migration trends also exhibited. Significant changes were observed between during study periods. The findings also revealed that the left bank of the Jaldhaka River is more unstable than the right bank. The oscillatory tendency in the meandering pattern was shown by temporal monitoring of the fluctuation in channel stretch. The study emphasizes that examining the erosion process can help us better understand the causes, develop forecasts, and plan how to implement preventive and remedial measures.