PNNL

Abstract

In this study, a Copula Monte Carlo (CMC) method was proposed to improve flood risk for confluence flooding control downstream of a reservoir. The effects of reservoir operation and joint relationships between two rivers streamflow were both considered in the method. The Copula function modeled the dependence between the mainstream and tributary; while the Monte Carlo (MC) method estimated the flood risk after the reservoir routing of mainstream flood and the simulated tributary flood from the Copula function. This proposed method was applied by a case study in the confluence flooding control downstream (Jinsha and Min River) of Xiluodu-Xiangjiaba reservoirs, Southwest China. After the simulation, the results were compared with the current MC method. Our results indicated that with the CMC method, the downstream flood risk caused by the Min River flood was 4.32%, 2.35%, and 1.08% for the 0.5%, 1%, and 2% design floods of Jinsha River, respectively; while the MC method underestimated the flood risk. The CMC method is more robust than MC since it can consider both the flood spatial correlations and the inside flood domain stochastic characteristics. Further, this method can provide decision support for joint operation of Xiluodu and Xiangjiaba cascaded reservoirs as well as flood risk planning and management.