Distribution and evolution of knickpoints along the Layue River, Eastern Himalayan Syntaxis

Abstract

The longitudinal profile of rivers in active orogenic belts records the competitive process occurring between erosion and uplift, and the knickpoint, as a unique sign, can support this. A series of distinctive knickpoints are distributed at different heights in the basin of the Layue River, which is a tributary located on the northwest side of the Yurlung Tsangpo Basin, China. By combining the stream power erosion model and field investigation, this paper explores the relationship among dams, knickpoints and the normalized steepness index (ksn). In addition to sporadic damming-type knickpoints, a 4 k knickpoint group located in the basin has attracted attention. Using the slope-area analysis method and the integration analysis method, paleo profile reconstruction of 14 tributaries and trunks was carried out to estimate the resulting paleo relief and net uplift. The results show that the topographic relief increases by 35.3–214.3% during the process in which the knickpoint entered into the basin and spread, which is the result of the growth and retreat of the knickpoint. Using the celerity model for the 4 k knickpoint group, 83.3% of the model knickpoints are less than 5 km away from the observed knickpoints, which indicates that the model is suitable for application in the Layue River Basin. And the migration rate of the knickpoint in the Layue Basin is 10.8–51.7 km/Ma at an initial setup time of 1.25–6 Ma.