Shifting of Main Course of River Ganga Within the Reach Bhagalpur to Kahalgaon Using Remote Sensing and GIS

Abstract

The lateral movement of the river channel within its Khadir over time is a universal phenomenon. Various processes of the fluvial-geomorphological environment, such as frequent occurrence of floods, deposition of sediment, the capture of lower courses of tributaries by the main channel, failure of the bank and avulsion, are predominant factors behind the channel dynamics. In this study, shifting of main course, bank-lines and the variation of the sinuosity index were computed from the year 1973–2018 within the reach Bhagalpur to Kahalgaon, in the state of Bihar, India. The area near both the banks is densely populated and has many important structures. Shifting of river banks put these structures under risk of failure and dwelling area under risk of submergence in flood seasons. It has abandoned its original course and huge sandbars have been formed in the middle of the stream. These sandbars are hindering vessel navigation too. The dynamics of channel adjustment in terms of lateral shifting can be beautifully illustrated by the application of modern geoinformatics tools, i.e., remote sensing and Geographic Information System (GIS). From the study of USGS satellite images using ARC-GIS, it has been found that the main course and bank-line has been shifted significantly during this period. The study of the width of the active channel and the position of main course indicates that both the left and right banks have changed significantly due to the erosion and deposition of sediment during monsoon period of each year. During the period 1973–2018, the river has moved toward its left bank and has become more sinuous in nature. This study highlights a significant message of immense vulnerability of the Ganga river and also points towards its geomorphological instabilities in this reach of the river.