Design Flood Volume of the Three Gorges Dam Project

With an increasing tendency of the flood disaster frequency and intensity in China, risk analysis of design flood volume for the Three Gorges Dam Project (TGP) should be of paramount importance for about one-half of the population and gross domestic product in China. How to predict the floods of Yangtze River with high precision is always a difficult problem, for the vast drainage basin and numerous tributaries. After a brief introduction of extreme value distribution and compound extreme value distribution, the TGP design flood volume predicted by the Chinese Hydraulic Design Code (CHDC) recommended annual maximum data sampling based Pearson type III extrapolation method is compared with the stochastic simulation technique based on the important sampling procedure (ISP) and the multivariate compound extreme value distribution (MCEVD), respectively. Comparison results show that the 100-year joint return period of the 3-day flood volume predicted by ISP and MCEVD is greater than 1,000-year return volume predicted by CHDC recommended method.