暴雨山洪设计临界雨量不确定性研究——以湖南省涔水南支流域为例

Uncertainty on design critical rainfall for flash flood early warning——Case in Censhui South Branch Watershed,Hunan Province

介绍了山洪预警临界雨量计算的基本思路与分析方法,基于《湖南省暴雨洪水查算手册》等资料,以湖南省涔水南支流域为例,充分考虑流域土壤含水量和暴雨雨型因素,运用水文模拟方法,对该流域3个预警地点暴雨引发山洪的设计临界雨量进行了分析计算,探讨设计了临界雨量与流域土壤含水量和暴雨雨型之间的响应关系。研究表明,流域土壤含水量和暴雨雨型对山洪设计临界雨量估算影响巨大,不同设计状态导致临界雨量阈值变化范围很大,不确定性非常明显,增大了山洪识别及预警发布决策的难度。获取流域适时降雨信息,滚动计算临界雨量,尽量避免和减少因流域土壤含水量和暴雨雨型导致的不确定性,是增强山洪预警可操作性、提高山洪预警准确性的重要方向。

Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-runoff process based on warning discharge threshold for a warning station of interest in a watershed;the key aspects of critical rainfall include rainfall amount and rainfall duration. Antecedent moisture content and storm pattern affect highly the estimation of critical rainfall. Using hydrological modeling technique with detailed sub-basin delineation and manual for design rainstorm-runoff computation,this study first introduced basic concept and analysis methods on critical rainfall for flash flood early warning,and then investigated the responses of flash flood warning critical rainfall to antecedent moisture content and storm pattern.Taking Censhui South Branch Watershed in Hunan Province as an example,critical rainfall in scenarios of typical antecedent moisture content and storm patterns were estimated at 3 warning stations of interest in this watershed. This research illustrates that both antecedent and storm pattern play important role in the estimation of critical rainfall and enough attention should also be paid to these factors when a decision to be made on whether a warning to be issued or not.