A STUDY ON CALCULATION OF EXPECTED ANNUAL DAMAGE CONSIDERING UNCERTAINTIES OF DISCHARGE-EXCEEDANCE PROBABILITIES

摘要

In this study, flood frequency analysis and Monte Carlo simulation are used to determine the expected annual damage (EAD) including uncertainties of discharge-probability function. Frequency analysis is applied to flood data of two stations, Dongchon and Seongseo in the Kumho River Basin in Korea. Appropriate probability distributions for those sites are selected based on the method of probability weighted moments and several goodness of fit tests. Sample data for each return period of an appropriate underlying probability distribution are generated by Monte Carlo simulation and then the appropriate sampling distribution is found based on the same frequency procedure. Then EAD, including uncertainties, is estimated by applying sampling distributions to discharge-probability functions. As the results, EAD considering uncertainties shows the larger value than EAD without considering uncertainties. The accuracy of EAD depends on the sample size, that is, the smaller the sample size is, the less accurate EAD is. Although the differences between EADs with and without uncertainties are small in two sites considered, EAD can be larger when the watersheds become more dangerous for flooding. In such a case, the estimation of EAD considering uncertainties of discharge-probability function is more necessary to reduce possible flood hazard.