Uncertainty on Design Critical Rainfall for Flash Flood Early Warning : A Case Study of South Branch Watershed of Censhui

摘要

Critical rainfall estimation for early warning of rainstorm-induced flash flood is an inverse rainstorm-0x09runoff 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 affects 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 South Branch Watershed of Censhui in Hunan Province as an example, critical rainfall in scenarios of typical antecedent moisture content and storm patterns was 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.