Improvement of rainfall temporal distribution method to reduce the frequency discrepancy between design rainfall and designed flood discharge

The most accurate way to estimate design flood volume is through flood frequency analysis based on stage-discharge gauging data. However, due to limited gauging stations in Korea, ungauged watersheds rely on rainfall-runoff models, which often yield results differing from direct frequency analysis. This discrepancy arises from assuming design rainfall and design flood share the same frequency and the smoothing effect of rainfall temporal distributions. This study identifies the underestimation issue in the commonly used Huff distribution and proposes an improved Blocking method for deriving design rainfall hyetographs. The proposed approach, similar to the Blocking method but incorporating statistical techniques, ensures frequency consistency and adapts to various rainfall patterns. Results show improved accuracy, aligning closely with direct frequency analysis, enhancing its practical applicability in hydrological design.