Abstract
In this study, we investigate the performance of the index flood method for 4 regions whose specifications are representative of annual maximum rainfall data in Korea. For this purpose, the Monte Carlo simulation was performed to investigate the influence on the accuracy of quantile estimates depending on the at-site and regional frequency analyses, sample size, inter-site dependence, heterogeneity, and applied frequency distributions. As the results, index flood method is more accurate than at-site frequency analysis in regions with moderate amounts of heterogeneity, inter-site dependence, and mis-specification of the applied frequency distributions. Heterogeneity increases the relative bias of estimates for the case of at-site analysis not typical case of regional one as a whole. Inter-site dependence increases the variability of estimates but has little effect on the relative bias. And small amount of inter-site dependence may be unimportant in regional frequency analysis. As the nonexceedance probability is increased, the advantage of index flood method over at-site frequency analysis is getting increased. Also, it is founded that the mis-specification of the frequency distribution is more important than heterogeneity as a source of error for large return period.