集中流引起的细沟侵蚀是黄土高原坡耕地主要侵蚀方式之一，对坡面集中水流动力学特性研究有利于掌握坡面集中流剥蚀产沙的根本原因，但目前哪种集中流水动力学参数最能准确揭示侵蚀动力过程机理尚不明确。该文采用室内集中流放水冲刷试验，以黄土高原典型黄绵土为研究对象，研究坡面平均和瞬时剥蚀率与相应水流剪切力、水流功率、单位水流功率以及过水断面单位能量之间的关系。结果表明，除了瞬时过水断面单位能量拟合效果较差外，其他平均和瞬时水力学参数均能够较好地与坡面剥蚀率建立不同的拟合关系。所有参数中平均水流功率是描述本试验条件下的最优水力学参数。由于细沟发育过程中大量坍塌的出现，导致整个径流剪切力和水流功率与剥蚀率之间的关系曲线整体上升，出现了临界剪切力和临界水流功率为负值的情况。通过与仅考虑水流对坡面直接作用参数所得结果对比，表明坍塌等作用在细沟发育过程中具有重要影响，对剥蚀率的贡献可达90.93%。研究可为控制和预防集中流侵蚀发生提供科学依据。%Rill erosion caused by concentrate flow is one of the main erosion types on cultivated slope in the Loess Plateau. It is necessary to research on the response of concentrate flow hydrodynamic characteristics for a better understanding of rill erosion mechanism. However, the optimal runoff hydrodynamic parameter for estimating detachment rate was still ambiguous. An indoor concentrate scouring experiment was carried out was carried out in the State Key Laboratory of Soil Erosion and Dryland arming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, China to investigate the response of runoff hydrodynamic characteristics to detachment rate under concentrate flow condition with different inflow rates and slope gradients. Loessal soil collected from Yanan (35°21′-37°31′ N and 107°41′-110°31′ E) in Shaanxi province, a kind of typical soil in the Loess Plateau, was prepared for this research. The experiments were applied to a soil plot with 5 m long, 1 m wide and 0.5 m deep. Packing was carried out layer by layer to attain the desired uniform bulk density (about 1.25 g/cm-3) with 40 cm in depth. The bottoms of the boxes were perforated and covered with a layer of 10 cm sand under the gauze to facilitate even drainage of percolating soil water. After packing, the soil was watered to saturation with an electric sprayer to reduce the variability caused by packing. Four flow rate (10, 15, 20 and 25 L/min) combined with four slope gradient (10°, 15°, 20° and 25°) were designed for this research. The experiment lasted for 10 min after runoff initiation. Runoff and sediments were collected in a series of plastic containers at intervals of 1 min throughout the 10 min. The volume of water in each container was measured, and the sediment was dried in an oven and weighed. The flow velocity was measured by dye-tracing technique within the 1-4 m away from the bottom and the flow width was also measured at 4 sections between 0.5-4.5 m to estimate flow depth at every minute during the experiment.The relations between runoff hydrodynamic characteristics, including shear stress, stream power, unit stream power and unit energy of water-carrying section, and detachment rate were analyzed. The results showed that all the mean and instantaneous runoff hydrodynamic characteristics factors fitted the detachment rate well with different regressions equations except instantaneous unit energy of water-carrying section. The mean runoff hydrodynamic characteristics factors were better than those of average values for fitting with detachment rate. The optimal runoff hydrodynamic characteristics factor in our research was mean stream power because it was of the largest determination coefficient 0.97. The curve of linear regressions of mean shear stress and stream power with detachment rate became ascended because of collapse during the experiment process, which also led to a negative value for corresponding critical shear stress and stream power. By comparing results with that from a published paper that only considered the flow effect on soil surface in the same soil, the detachment rate directly estimated based on mean stream power were more reasonable than those estimated based on mean shear stress. The collapse could account for 90.93% of the detachment rate, indicating an important role of collapse during rill development process. The results provide valuable information for a better understand of the response of concentrate flow hydrodynamic characteristic factors to detachment rate and its corresponding erosion mechanism.
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