Sensitivity analysis of the flash flood hazard by coupling variable fuzzy method and mutual entropy

Watershed characteristics are one of the crucial factors affecting watershed hydrologic processes. Watershed hydrologic process regulation has been shown to be an effective tool for flash flood management. This study aims to propose a coupling method to evaluate the flash flood hazard degree of small hilly ungauged watersheds based on their watershed characteristic factors and identify sensitive factors influencing flash flood hazard. In this regard, nine watershed characteristic factors were selected for flash flood hazard sensitivity analysis. The variable fuzzy method (VFM) was proposed to calculate the eigenvalue of flash flood hazard degree for each small hilly watershed, and mutual entropy was proposed to identify sensitive factors influencing hazard degree. As an example, the sensitive factors in Licheng County with 119 small hilly watersheds in China are identified and further verified by stepwise regression analysis, which are mean watershed slope, soil moisture, average width of the mainstream, and watershed shape factor. This study shows that VFM and mutual entropy can be used jointly to identify the sensitive factors associated with the flash flood hazard in small hilly ungauged watersheds. The results can be used for engineering measure management in flash flood hazard control.