Channel migration zone mapping of the River Ganga in the Diara surrounding region of Eastern India

Abstract

River channel migration is the universal phenomenon that is common in almost all alluvial rivers. The holy River Ganga, the heartbeat of India, is also not an exception in this case. It has shifted its course from time to time. After crossing the Rajmahal hills that is situated in the north-eastern corner of the Chota Nagpur plateau, this main river of India has started its lower course by flowing over the great low-lying flat plain of Bengal. In this flat plain area, the channel migration is a common phenomenon which is observed in the River Ganga also. The study is done in the segment of the Ganga River which is situated in the Diara surrounding area. Diara is a physical cum administrative region of the Malda district of the state of West Bengal of India which occupies an area of almost 900 km2. For the identification of channel migration zone, several methods are used like construction of historical migration zone (HMZ), erosion buffer (EB), avulsion potential zone (APZ), restricted and un-restricted migration area (RMA and UrMA) and retreating migration zone (RMZ). The impact of the channel migration over the villages of the Diara region has also been depicted in this study. Remote Sensing and Geographical Information System (RS–GIS) is used to perform this study by taking the help of historical maps, Survey of India topographical sheets, LANDSAT imageries, etc. The results show that the river has a historical migration zone of 855.55 km2 during 1926–2016 period which is near the entire area of the Diara region (i.e. 900 km2). The construction of EB over the Ganga River for the next 100 years shows that more than half of the area of the Diara region will go under the river bed.