Research on the Co-occurrence Characteristics of the Floods Between Lower Reaches of Jinsha River and the Chuanjiang River

Abstract In order to provide a theoretical basis for real-time flood control, reduce the flood disaster in the lower reaches of Jinsha River and the upstream Yangtze River (the section in Sichuan Province, also known as the Chuanjiang River), as well as alleviate flood control pressure of the downstream Three Gorges Project flood encounter characteristics between the lower reaches of Jinsha River and the Chuanjiang River were discussed in detail based on Copula Function Method. AIC criterion and OLS criterion were applied in the paper to evaluate the fitting effect of four Archimedean Copula function models, and Frank Copula function with the best effect was selected for the flood encounter analysis subsequently. The result shows that: the proportion of the maximum 3d, 7d, 15d, 30d flood volume of the lower reaches of Jinsha River in the composition of the Chuanjiang River increases in sequence. Frank Copula function has very small errors in the flood encounter problems of the lower reaches of Jinsha River and Chuanjiang River, with higher credibility, its calculation results are consistent with the flood encounter laws of the two rivers. The frequency of occurrence of the largest flood peak in the two rivers in different months is significantly different. The co-occurrence probability of floods with peak flow greater than 50-year flood for the two rivers is 0.15%. Therefore, by taking full advantages of the flood co-occurrence characteristics, it’s extremely practicable to reduce not only the flood control pressure of Chuanjiang River but also the downstream Yangtze with the cascade reservoir operation in the lower reaches of Jinsha River.