Analysis of the suspended sediment dynamics in the midstream of the Brahmaputra River in Tibet using a sediment rating curve approach

Abstract:

The effect of climate and land cover changes on soil erosion is a relevant factor in river management and ecological protection on the Tibetan Plateau. Lack of field observation data is a strong limitation to investigate soil erosion and sediment transport. The aim of this study is to assess the spatial and temporal variations of sediment fluxes in the midstream of the Brahmaputra River based on intermittent discharge and suspended sediment datasets obtained in 2007-2009 at the Lazi, Nugesha, and Yangcun hydrological stations and to develop an empirical sediment transport model using a sediment rating curve (SRC) approach, by interpolating the points on the graph of discharge (Q) vs sediment concentration (C). SRC coefficients correlating with catchment area and other catchment characteristics vary spatially and temporally. Based on the seasonal variability of the SRC coefficients, we assume that larger flow peaks mobilize source sediments not previously activated. As a result, sets of SRC coefficients were obtained for different time periods throughout the year separated by flow peak ranking, which were further used to predict the suspended sediment concentrations/loads based on discharge with improved accuracy compared to the traditional SRC approach.