清水河流域场次洪水输沙特性及关键影响因素

Characteristics of Sand Transport and Key Driving Factors of Flooding Events in the Qingshui River Basin

[目的]揭示水沙对关键环境因子的响应规律,以期为促进黄河流域水土保持综合治理提供理论基础。[方法]利用清水河流域场次洪量和输沙量数据,基于径流侵蚀功率理论和随机森林等方法系统分析了清水河流域场次洪水输沙特性及其关键影响因素。[结果]流域产洪输沙量呈现显著的空间分异特性,影响不同子流域洪水输沙过程的主要参量有所区别。随机森林结果表明在小量级洪水频发的区域主要影响因素为径流深、洪水历时与洪峰流量,而在中量级洪水频发的区域则分别为径流深、洪峰流量与平均流量。在侵蚀产沙的解释变量中引入表征径流过程的复合指标更能综合体现天然降水和流域下垫面属性对次洪过程侵蚀产沙的影响,其拟合精度相较于传统的径流-输沙关系更高。[结论]相比于传统的径流深、平均流量或者洪峰流量等单一径流参量指标,径流侵蚀功率更适宜描述次洪尺度水沙关系。

[Objective]The aims of this study are to reveal the response patterns of water and sand to key environmental factors,and to provide a theoretical basis for promoting integrated soil and water conservation management in the Yellow River basin.[Methods]Based on the theory of runoff erosion power,the Random Forest method and the daily measured runoff and sediment data in the Qingshui River basin,we analyzed the sediment transport characteristics and key driving factors during flooding events.[Results]The flooding and sand transport in the basins showed significant spatial variation,with differences in the main parameters affecting the flooding and sand transport processes in different sub-basins.The results of the random forest showed that the main influencing factors were runoff depth,flood ephemeris and peak flow in areas where small floods were frequent,and runoff depth,peak flow and mean flow in areas where medium floods were frequent,respectively.The introduction of composite indicators for runoff processes in the explanatory variables of erosion and sand production could better represent the influence of natural precipitation and basin substrate properties on erosion and sand production during sub-floods,and the accuracy of the fit was higher than that of the traditional runoff-sand transport relationship.[Conclusion]Runoff erosion power is more appropriate for describing sub-flood-scale water-sediment relationships than traditional single runoff parameters such as runoff depth,mean flow or peak flood flow.