A COMPARISON OF TWO BEDROCK RIVER STREAM-POWER EROSION MODELS: A CASE STUDY OF THE RIVER PROFILE OF THE GYIRONG WATERSHED IN THE MIDDLE HIMALAYAN OROGEN

The models for quantitative study of bedrock river are two typical representatives: the Distance-slope (DS) Model and the Area-slope (AS) Model. The AS model introduces the law of the matter conservation and builds a bridge between tectonic uplift and erosion. In recent decade, AS has been widely used in the longitudinal profile simulation of bedrock and alluvial rivers, but many applications have failed to carefully consider the mechanism, fitting effect, and applicability of the resulting models, resulting in unsatisfactory simulation results. In order to verify the channel profile analysis capability of the two models, the study compared the theoretical basis and the applications of channel fitting and knickpoint identification made in the Gyirong Watershed in the middle Himalayan Orogen. It is believed that if the river meets the equilibrium condition, both models reflect the law of the matter conservation, instead of being limited to the AS. The results show that, for rivers with different equilibrium status, the two have different numerical responses on 7 bedrock rivers. The AS model has a comparative advantage in river channels with a higher degree of equilibrium, while the DS model is more suitable for longer rivers in a disequilibrium state. Finally, we applied DS model to the Gyirong Zangbo River in order to analyze the numerical characteristics of the knickzone parameters. It is found that the distribution of concave-convex intersection on the profile corresponds to the variation of the fast and slow erosion rate. This characteristic reflects the interaction between the river erosion and sedimentation in the Gyirong Watershed and is sensitive to the formation processes of the differentiated climate patterns over the past 2 Ma