Geomorphic evolution of Sutlej valley catchment in Western Himalayas: Imprint of surface processes in modulating fluvial erosion

The Sutlej River catchment in the tectonically active western Himalayas has several geomorphic signatures of river piracy and drainage reorganization across the Upper Sutlej-Zhada basin upstream. The accelerated growth of the Leo-Pargil Horst across the Kaurik Chango-fault (KC-fault) Zone and affected regional tectonics triggered enormous incisions, causing southward migration of the present Sutlej River, which is highly infested by bedrock landslides and debris flows and evolves as a very steep valley catchment. In order to understand the changing regional landscape and identify the tectonic perturbation over the channels, we evaluate the slope-break knickpoints in the Sutlej River profile. Furthermore, we model the presence of an elevated low-relief relict landscape in the Upper Sutlej-Zhada basin and the rapid incising lower Sutlej valley catchment using the Celerity model. The observation suggests that major knickpoints at ~2000–3000 m elevation comprise the fluvial erosion process, while higher elevation knickpoints recommend the hillslope process. In order to understand how fluvial erosion and surface process imprints have changed the landscape over time, we spatially correlate terrestrial datasets, such as rates of denudation and exhumation ages, with topographic metrics and climate variables. We observe a strong correlation between the pattern of denudation rates and the conditioning factors that modulate the surface processes. Increased channel erosion, high stream power, topographic metrics, and the occurrence of bedrock landslides over a regional structural disruption exhibit a positive spatial relationship, but their role in regional drainage capture, tectonic uplift, and the gradation process remains poorly understood.