Exploring tectonic, climatic, and substrate influences on topography in the Ghaghara watershed, western Nepal

Much of the Himalaya features an abrupt topographic transition from moderate relief towards the foreland to near slope-failure conditions towards the orogen's core. However, in western Nepal, high topography builds more gradually, and the transition to highest elevations deflects northward with respect to neighboring parts of the orogen. Recently, this embayment in the high Himalaya has been argued to reflect along-strike transitions in the geometry of the Main Himalayan Thrust and used to infer upper- and mid-crustal structures. We utilize remotely sensed datasets, geologic mapping, and a new suite of 10Be catchment-averaged erosion rates to test this hypothesized link between tectonics and landscape evolution in western Nepal. We limit our analysis to within the Ghaghara watershed, which encompasses a remarkable variety of distinct landscape types, including: the topographic embayment, regions of high elevation and low relief, abrupt transitions in steepness, and vast portions of presently and formerly glaciated terrain. Preliminary results suggest a weak correlation between erosion rates (ranging from ~50-350 m Myr-1) and channel steepness and point towards the importance of glaciers in modifying the landscape and introducing a degree of decoupling between topography and activity along deep-seated structures in the western Nepal Himalaya.