How Are Glacier-Dominated Himalayan River Corridors Responding to Climate Change in Terms of Relative Vegetation Cover? A Remote Sensing Investigation

Highlights: What are the main findings? The dynamics of the riparian vegetation cover over the last few decades in the studied glacier-fed Himalayan Rivers appear to be strongly river-specific, and a single evolutionary trajectory related to the deglaciation phase is not evident. Both increasing and decreasing trends of riparian vegetation cover occurred in the studied rivers but such trends seem to be poorly related to the analyzed hydroclimatic drivers, suggesting a complex interplay among river runoff, sediment supply and vegetation resistance/erosion. What are the implications of the main findings? This study contributes to the scientific understanding of how glacier-dominated Himalayan Rivers adjust their channel forms and sustain riparian vegetation across spatial and temporal scales. These results provide a reference point for interpreting future river-corridor changes in response to ongoing glacier retreat. By interpreting the structure through which climate-driven hydrological changes shape both vegetation stability and geomorphic dynamics, the results highlight critical pathways that can guide future predictions of climate-related hazards and lead the sustainable management of Himalayan river systems. The adjustments in channel morphology under influence of vegetation dynamics, impacting natural sediment and flow regimes at local, catchment, and regional scales, are primarily driven by natural and anthropogenic factors. Limited knowledge exists regarding the historical channel adjustments along Himalayan glacier-dominated rivers. This study specifically concentrates on three distinct glacier-dominated river segments: Nubra in Jammu and Kashmir, Ganga-Bhagirathi in India, and Langtang-Khola in Nepal. The research adopts a supervised classification model initially developed by Mukhtar and extends the technique by applying it to four additional sources of satellite data with spatial resolutions ranging from 2.4 m to 30 m. This extension of the model is accomplished using the Google Earth Engine (GEE) platform to extract three main macro-units (base-flow channels, emerged sediment bars and vegetated surfaces) in fluvial corridors. Across different locations, the behavior of the rivers exhibited variability; however, possibly cyclic behavior in riparian vegetation cover was observed during the studied period. Surprisingly, in the subsequent period of 2016–2020, noticeable channel widening was observed in almost all reaches of the three river segments. Notably, the high meltwater runoff periods from 1989 to 2003 in the Nubra River segment induced vegetation erosion and channel widening. On the contrary, flood events during the early 21st century possibly lacked the duration and intensity required to impact vegetation growth in river corridors. This trend was also evident in the Ganga-Bhagirathi River, where the stable vegetation cover showed no major effects from the 2012 flood event. Despite the susceptibility of the Langtang-Khola river to landslides and earthquakes, the study reaches in Langtang-Khola River remained unaffected by these catastrophic events. Briefly, this study contributes to an enhanced understanding of the intricate dynamics of channels and vegetation in Himalayan glacier-dominated rivers, spanning diverse spatial and temporal scales, and elucidates their correlation with factors related to climate change.