坡面径流含沙量随雨强和坡长的动态过程

Research on the Dynamic Processes of Sediment Concentrations in Slope Runoff with Rainfall Intensity and Slope Length

坡面径流的含沙特征是研究坡面侵蚀产沙的重要内容。为了研究坡面径流含沙特征及动态过程,揭示坡面径流含沙量随雨强和坡长的复合关系。采用人工模拟降雨的方式,通过不同坡长和雨强的组合试验,基于跨雨强和跨坡长的综合性分析思路,对特定坡度(20°)下,5个坡长(1,2,3,4,5m)13个降雨强度的试验监测数据进行了分析。结果表明:(1)坡长不同,含沙量与雨强的相关性不同,以2,3,4m坡长含沙量随雨强增加的规律性最明显,5m坡长的相关性最差,1m坡长的直线相关性较好,但增长斜率很小,由此可推得,研究坡面径流含沙量随雨强变化时,以2~4m坡长的试验槽较为适宜;(2)含沙量随产流历时总体上呈现出波动递减的趋势。含沙量波动特征值在2~4m坡长范围内波动性小而波动频率大,在1,5m坡长的波动性大但频率小。坡面径流含沙量变化的频率远大于河川径流含沙量的变化频率,即稳定性较差;(3)含沙量与主要水文要素和水力学特征参数的拟合都呈现出极显著相关性,流速、流量和剪切力是影响含沙量波动的重要因素。

The sediment characteristics of slope runoff are of great importance to study the slope surface erosion and sediment yield.In order to study the sediment characteristics and the dynamic processes of slope runoff,and to reveal the composite relations between sediment concentrations of slope runoff and the slope length and rainfall intensity,the artificial rainfall simulation were adopted based on the different combinations of slope length and rainfall intensity.The comprehensive analyses were used to analyze the monitoring data of 5 slope lengths（1,2,3,4,5 m）with 13 rainfall intensities under a designed slope（20°）.The results showed that：（1）Under the different slope length,the correlations between sediment concentrations and the rainfall intensities were different.The increases of sediment concentrations were the most obvious with the increasing rainfall intensities in the slope length of 2,3,4 m,but the least in 5 m.The linear correlation between sediment concentration of slope runoff and the rainfall intensity was better in the 1 mslope length,but its increasing slope was small.Thus,the slope length of 3 m was the most suitable for studying the changes of sediment concentrations with different rainfall intensities.（2）The sediment concentrations of slope runoff decreased undulately with the duration of production flow.The fluctuating characteristic value of the sediment concentration was small and the fluctuating frequency was large in the slopes length of 2,3 and 4 m,while with a large concentration and a small frequency in 1 mand 5 mslopes.The changing fre-quency of sediment concentrations of slope runoff was much higher than that in river flow.（3）There were significant correlations between the sediment concentrations of slope and the main hydrological elements and hydraulics characteristic parameters.The flow velocity,discharge and shear force were the important factors affecting the fluctuation of sediment concentrations.Because the starting velocity of sediment varies with different underlying surfaces,it is the key to measure the flow velocity and sediment concentrations timely,accurately and dynamically for the study of slope surface erosion and sediment yield processes.