Topographic and climatic controls on decadal-scale catchment-basin erosion rates in the northern Chinese Tian Shan

Surface erosion shapes the topography of an active orogenic belt with a rate depending on the time and space scales. Quantifying erosion rates over various temporal and spatial scales is thus crucial for understanding the topographic evolution in active orogenic belts. This work focused on the decadal catchment-basin erosion rate and its controlling factors in the northern Chinese Tian Shan. Nine mountainous catchment basins were selected to quantify the decadal-scale erosion rates from hydrological data measured during the years 1964–2011. The contributions of the suspended load, bed load, and solute load in the river sediment load were first determined. The erosion rate was then calculated for each analyzed catchment basin. The results show that the average rate of catchment-basin erosion is ∼ 0.15 mm yr⁻¹, whereas the rate varies from one catchment basin to the next (the minimum rate of 0.05 mm yr⁻¹ in the Urumqi and the maximum rate of 0.30 mm yr⁻¹ in the Manas). In order to explore the possible effects of climate, topography, lithology, vegetation, and tectonics on catchment-basin erosion, correlation analyses were conducted between these factors and the erosion rate. The results indicate that the catchment-basin erosion rate is more closely correlated with topographic factors (basin area and basin relief) and climatic variables (discharge, run off, run off depth, and mean temperature), indicative of the main controlling of topography and climate on catchment-basin erosion. The erosion rates reported in this work are approximately consistent with the paleo-erosion rate of < 0.5 mm yr⁻¹ over the last 1.5 Myr derived from in situ produced cosmogenic ¹⁰Be concentrations in the Kuitun catchment basin in the west part of the range. Such a consistency is likely to imply relatively stable erosion during the late Quaternary in the northern Chinese Tian Shan.