Integrating DEM and flow stress factors to identify sedimentation-transportation zone in the eastern Himalayan...

The river basins of the Himalayan foothills exhibit highly dynamic sedimentation and sediment transport processes. The presence of active tectonic zones further modulates the sedimentary regime and fluvial dynamics within the foothill Himalaya. The Neora River, extending for about 60 km, and about 60% of its course drains through the foothill portion of the Darjeeling Himalaya and crosses several distinct tectonic thrust zones. However, studies that integrate secondary observations with primary field validation within this region are scarce, emphasizing the requirement for a clearer understanding of interface zone identification. This study delineates the spatiotemporal variability of fluvial process footprints using Longitudinal profile analysis and DEM of Difference (DoD) analysis, supported by field surveys conducted during post post-monsoon season were used to verify remote sensing results and reveal sediment-load dynamics within the Neora River basin. The result reveals that the thrust zones-particularly the Himalayan Frontal Thrust (HFT)-within the foothill Himalaya exert pronounced geomorphic control over sediment dynamics. The study findings further indicate that critical shear stress in the middle course (upstream of the HFT) is ∼0.85-13.35 times higher than flow shear stress, while in the lower course, flow shear stress predominates with spatial variability. This type of stress variability drives differential morphodynamics, resulting in deposition of river bed material in the middle course (∼27.54 cm yr^-1) and erosion of bed material in the lower course (∼4.9 cm yr^-1). An integrated analysis of bed load behavior and flood frequency in this basin provides valuable insights for developing effective river management strategies aimed at maintaining channel competence and fluvial stability.