Quantification of flood runoff reduction effect of storage facilities by the decrease in CN

This study proposed a methodology for quantifying the flood runoff reduction effect of storage facilities by curve number (CN). The runoff hydrographs for various rainfall durations and return periods were derived using the modified rational method. The effect of runoff reduction due to the introduction of storage facilities was then quantified by CN. The result derived was summarized in a graph showing the decrease in CN as an effect of the runoff reduction with respect to the rainfall duration, return period, runoff coefficient of the catchment, and size of the storage facility. The runoff reduction effect of a storage facility was able to be easily and directly estimated using the derived graph. The result derived was also found to be well matched with the previous study for three different sites.