Uncertainty on design critical rainfall for flash flood early warning——Case in Censhui South Branch Watershed,Hunan Province
Li Changzhi, Zhang Xiaolei, Sun Dongya, Guo Liang
1. China Institute of Water Resources and Hydropower Research, Beijing 100038; 2. Research Center on Flood and Drought Disaster Reduction of the Ministry of Water Resources, Beijing 100038
Abstract: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.
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