Evaluation of flood runoff reduction effect of LID (Low Impact Development) based on the decrease in CN: Case studies from Gimcheon Pyeonghwa district, Korea

LID are spread on a small scale throughout target area, therefore, evaluation of their overall effect on flood reduction is not straightforward. As one solution dealing with this problem, Yoo et al. (2012) proposed a methodology for quantifying the flood runoff reduction effect of storage facilities by curve number (CN). Introduction of various infiltration or storage facilities causes the decrease in CN, which can be calculated using the runoff. The result derived was summarized in a graph showing the decrease in CN as an effect of the runoff reduction. That is, the runoff reduction effect of infiltration or storage facilities was able to be easily estimated using the derived graph. In this study, LID effects of Gimcheon Pyeonghwa district in Korea was quantified using this method. Additionally, the reduction amount of the runoff volume using the method suggested by Yoo et al. (2012) was compared with that estimated by using SWMM 5.0. As a result of this, the effect of LID facilities was shown similarly in both cases using the methodology used in this study and simulated using SWMM 5.0. This result verified that the methodology was valid even though it is straightforward and simple.