Evolution of Holocene Floodplain of Jaldhaka River in Cooch Behar Plain of West Bengal, India

Abstract

This study evaluates how the river networks and floodplain geomorphology of the Jaldhaka River have changed within a dynamic Himalayan foreland basin environment over an 88-year period (1934–2022). Floodplain geomorphological maps were prepared using high-resolution satellite images and historical maps. Field validation contributed to improving the accuracy of landform mapping, while sedimentary log analysis allowed the recognition of floodplain types and fluvial architectural elements. Channel oscillation attributes were interpreted based on indices such as channel length, channel width, and sinuosity, as well as bankline migration and erosion–accretion areas. The findings suggest that progressive channel migration and meander shifting have shaped various floodplain landforms in the recent past, such as cut-offs, palaeochannels, backswamps, abandoned channels, and meander scroll bars on a Holocene river plain. These features are well developed in the middle and lower floodplains. Quantitative analysis indicated that the channel sinuosity of the middle and lower segments of the Jaldhaka River fluctuated (1.15, 1.24, 1.42, 1.18, and 1.31 for the years 1934, 1955, 1983, 2003, and 2023, respectively), implying channel lengthening or shortening due to meander development and cut-off formation processes taking place over time. The results also demonstrate spatiotemporal variations in channel width and an increasing trend in erosion–accretion areas during the period 1983–2023. Both natural processes (such as variable discharge, frequent flooding, active tectonics, meander migration, and channel shifting) and human interventions (including channelization, mining, construction of cross-sectional structures, and land-use changes) have contributed to the evolution and morphological modification of the Jaldhaka River system and its floodplains in the Cooch Behar Plain, West Bengal.