Risk assessment for closure of the diversion channel at the Three Gorges Project on the Yangtze River

This paper is mainly focused on the assessment of both the hydrological and hydraulic risks in the closure of the diversion channel Three Gorges Project (TGP) at the Yangtze River, which was carried out at the end of 2002. By using the daily flow data of the Yichang hydrological station during the period of 1877-2000, techniques such as the Pearson type-3 distribution, the flow duration curve and a Poisson process model were used to estimate design flow discharge and assess the hydrological risks. In a second step, a one dimensional unsteady flow hydraulic model was used to obtain the values of total energy head, flow velocity, etc., for the given design flow. Assuming the total energy head of the closure gaps as a random variable with normal distribution, a model was proposed for calculating the hydraulic risk of the closure of the TGP diversion channel.