Investigating the bivariate joint distribution of flood characteristics in the Qarasu River catchment using elliptic and Archimedesian copula functions

The catchment area of Qarasu river is always exposed to floods. To prevent possible damages, factors affecting the occurrence of floods in this area should be investigated. In this research, the dependence between the two main flood variables of peak flow and volume was determined during a statistical period of 41 years using copula functions. The results showed that the most suitable marginal distributions for both variables are Log-normal and Weibull, respectively. moreover, normal copula function is the most capable function to depict the structure of dependence between them, according to goodness of fit tests. Finally, applying the selected copula illustrated that the joint return periods in the state {or} is less than the joint return periods in the {and} and single variable state.