降雨-径流格局对土壤侵蚀过程具有重要影响,以团山沟七号全坡面径流场1961-1969年间65次径流事件的径流泥沙数据为基础,选取历时、径流深和径流变率为径流过程的特征指标,采用K均值聚类和判别分析相结合的方法,将坡面径流划分为 5 种类型.其中,A 型径流具有超长历时、低变率、小径流的特点,是较为特殊的类型,B、C 型径流具有中长历时、中高变率、大径流的特点,D型径流具有短历时、低变率、小径流的特点,是最为普遍的类型.E型径流具有中历时、中变率、中径流的特点.不同径流类型下的输沙模数、平均含沙量及最大含沙量由大到小依次为: C>B>E>D>A,B、E、C型径流应是坡面径流调控的重点.不同径流类型输沙模数的差异主要来源于径流量(深)的变化,相同径流量(深)条件下,不同径流类型输沙模数的差异主要来源于由径流历时和径流变率所引起的水沙传递关系的改变;与A型径流相比,其作用使D、E、B、C型径流的输沙模数相对增大7.9、6.3、4.8和4.5倍,增大倍数随径流量(深)的增加呈逐渐减小趋势.通过构建包含主要径流特征指标的动力参数 ξ,对不同径流类型及径流阶段的径流-泥沙传递关系进行数学描述,其最优回归关系均符合S =alnξ+ b的一般形式,能合理解释不同径流类型及不同径流阶段含沙量变化的主要驱动因素.研究结果可为坡面径流类型划分、水沙传递关系构建、全面评估坡面径流调控系统的水土保持意义、进一步丰富坡面径流调控理论的内涵提供一定的参考.%The process of soil erosion is significantly impacted by rainfall-runoff pattern. To investigate the impact of runoff regimes on sediment yield and sediment flow behavior at slope scale, runoff and sediment data was collected and analyzed based on 65 individual runoff events from No.7 runoff plot at entire slope scale at Tuanshangou Catchment. Runoff process was characterized by runoff duration (T), runoff depth (H) and the ratio of peak discharge to mean discharge (flow variability, RPM) based on correlation analysis. Combined method of K-mean clustering, discriminant analysis as well as One-Way ANOVA was utilized to classify the runoff regimes. To quantify the relative impact of different runoff regimes on sediment yield from the same runoff amount (depth), 12 comparative groups were selected to conduct comparative analysis. Furthermore, dynamic indexes termedξ were constructed with the method of multiple stepwise regression based on main indexes of runoff characteristics to depict the flow sediment behavior under different runoff regimes and runoff phases (rising limb and recession limb). The results showed that the runoff at entire slope scale could be classified into five regimes: Regime A with super-long duration, low flow variability, and minor total discharge (a particular regime); Regime B with relative long duration, medium flow variability, and large total discharge; Regime C with long duration, high flow variability, and large total discharge; Regime D with short duration, low flow variability, and minor total discharge of high frequency; Regime E with medium duration, medium flow variability, and medium total discharge. Area-specific sediment yield, mean suspended sediment concentration and maximum suspended sediment concentration showed great difference between different runoff regimes, which ranked in the order of C>B>E>D>A. This indicated that regime B, E, and C should be paid more attention to conduct runoff regulation. The difference of area-specific sediment yield between different regimes mainly derived from the variations in runoff amount (depth); and yet, the effect of altered flow-sediment relationship on area-specific sediment yield was masked. From another perspective, the difference of area-specific sediment yield originated from different regimes with the same runoff amount (depth) mainly derived from the variations in flow sediment behavior. Driven by the variations in sediment flow behavior, in comparison with regime A, the relative area-specific sediment yield from regime D, E, B and C were increased by 7.9 times, 6.3 times, 4.8 times and 4.5 times, respectively. In addition, the increase ratio decreased with the increase in runoff amount (depth). The optimum regression equation between suspended sediment concentration (S) and dynamic parameters (ξ) based on main runoff characteristics obeyed the function form ofS =alnξ+b (R2>0.5,sig<0.001), which can interpret the main driving factors resulting in variations in sediment concentration under different runoff regimes and runoff phases. In conclusion, the results may provide some evidence for runoff pattern classification, construction of flow-sediment relationship, overall evaluation on the benefit of runoff regulation system at slope scale, as well as the further enrichment of the theory of slope runoff regulation.
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