Systematic appraisal of geomorphic river mobility across the Ganga basin

Multi-decade satellite data are increasingly used to assess changes in the wetted extent of large rivers, but few studies rigorously document both system- and reach-scale geomorphic mobility across the entire active width of river systems. Here, we quantify satellite-derived locational probabilities for 15 major rivers across the Ganga basin to systematically appraise geomorphic river mobility. Google Earth Engine (GEE) was used to biennially resolve active river channels from Landsat imagery (1990-2023), which includes the wetted channel and unvegetated alluvial deposits. At the system-scale, results reveal behavioural differences between Himalayan and cratonic rivers. Himalayan rivers are characterised by greater changes in active channel extent (mean locational probability = 0.46) than cratonic rivers (mean locational probability = 0.81). Many rivers show spatially non-uniform variability in along-valley patterns of geomorphic river mobility, with marked differences in mobility between reaches. The Wasserstein distance metric is used to quantify this reach-scale variability and identify locations where the changes are most pronounced. Given the increasing anthropogenic stresses on the Ganga basin (e.g., climate change, hydrological alterations and structural interventions), satellite-derived locational probabilities can be used as an interpretative tool to further investigate specific river dynamics.