Seasonal Design Flood Based on Copula Function

Seasonal design flood should not only satisfy the flood prevention standard but also reflect seasonal variation characteristics. The present seasonal design flood method is under the assumption that the seasonal design frequencies equal to the reciprocal of the flood prevention standard, which causes the return period of the design values is less than the standard. The most fitted Copula function has been selected and used to describe the joint distribution of three seasonal maximum flood series with Pearson Type III distribution margins. Then seasonal flood can be designed via a relation between the frequencies of seasonal maximum flood and flood prevention standard on the trivariate return period bases. The seasonal design flood based on Copula function were compared with the present method, and the results show that Copula function is rational and can solve the problems existed in the present method. The proposed method provides a new approach for seasonal design flood.