Sediment source tracing during flood events in the Huangfu River basin in the northern Loess Plateau, China

Abstract

Identifying critical soil erosion areas and sediment sources are essential for sediment control and water resources management in the watershed, especially in the severely eroded northern Loess Plateau, China. In this study, we collected suspended sediment samples at the hydrological stations to identify the sediment source dynamics during flood events in a highly erodible basin, the Huangfu River basin in the Northern Loess Plateau. A total of 6 flood events were sampled during 2016 and 2018 for investigation, the flow discharge was featured by a rapid rising limb and a slow falling limb. Compared with the sediment sources, the silt fraction in the suspended sediments was enriched and the sand fraction in the suspended sediment was depleted. The dominant particle grain size of suspended sediments was coarse sand (56.89%), higher than silt (41.81%) and clay (1.3%). The sediment sources were estimated using the FingerPro unmixing model based on the conservativeness index (CI) and consensus ranking (CR) methods. The results of the unmixing model reveal that the bare land was the predominant source of suspended sediments, ranging from 40% to 57%, which was much higher than farmland (27 ∼ 31%) and grassland (16 ∼ 25%). Our findings imply that the bare land (weathered sandstone area) is the critical region for soil loss control in the Huangfu River basin. A combination of vegetation restoration measures and engineering measures are proposed to improve the sustainable development of ecological environment in the basin.