Monitoring changing course of the river Ganga and land-use dynamicity in Manikchak Diara of Malda district, West Bengal, India, using geospatial tools

Abstract

Dynamicity of the river Ganga introduces significant changes in the land-use character of active alluvial plain of West Bengal, India. The dynamicity of the river Ganga is caused due to continuous sedimentation and formation of char land which frequently changes the flow direction and flow velocity of running water as well as causes the shifting of the bank line due to active bank erosion processes in the upstream of Farakka Barrage. Bank line shifting was estimated with the help of 25 transects since 1973–2011. A large-scale land erosion (38.6 sq. km area) occurred due to the bank line shifting which observed in Godai, Kesharpur, Rambari, Hiranandapur, Mathurapur, Manikchak, Samastipur, Dakshin Chandipur, and Gopalpur mouzas of Manikchak block, whereas deposition (2.4 sq. km area) was found in Chandipur Tofi Narayanpur and Govindapur mouzas. Such erosion and deposition invited a lot of changes in land-use statistics. Land-use–land-cover maps were prepared using supervised image classification techniques and validated through kappa statistics (kappa coefficient 0.803 and 0.892 for the year 1994 and 2016, respectively). Land-use change detection technique was used to identify the transformation of land-use character from one feature to another. This study revealed that a notable area of settlement (5.07 sq. km) and vegetation cover (6.84 sq. km) was converted into water body as a result of bank erosion. Loss of agricultural land and homestead led to the loss of livelihood and introduced internal migration. The observed pattern of river dynamics and the consequent land-use change in the recent decades have shown newer environmental challenges to the coping capabilities of the rural inhabitants.