Critical Rainfall Analysis on Flash Flood Early Warning for South Branch of Censhui Watershed

TLDR: Using hydrological modeling technique with detailed sub-basin delineation and manual for design precipitation-runoff computation, the authors introduces basic concept and methods of analyzing critical rainfall for flash flood early warning.

Abstract: Critical rainfall for flash flood early warning is a converse result of precipitation-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. Using hydrological modeling technique with detailed sub-basin delineation and manual for design precipitation-runoff computation, this study introduces basic concept and methods of analyzing critical rainfall for flash flood early warning. Taking South Branch of Censhui watershed in China as an example, typical critical rainfalls for flash flood dynamic early warning were estimated for 3 warning stations located in the watershed. This research illustrates that detailed watershed characteristics in the context of several warning stations can be modeled in-depth by further delineating the watershed into smaller sub-basins to simulate spatial distribution of various basin parameters. It further confirms that time of concentration of a watershed is an important factor to rainfall duration determination, and the antecedent soil moisture condition of a watershed has significant impact on critical rainfall for same rainfall duration.