Investigating the effect of sediment on flood occurrence in Qarasu River catchment using copula functions

The multi-dimensionality of the flood phenomenon causes us to not be able to get an accurate estimation of flood characteristics with one-variable analysis. Moreover, multi-dimensional analysis usually includes the variables of peak flow, volume, and duration of flood. Meanwhile, other variables, such as sediment, can affect the occurrence of floods. This research examined the effect of sediment on the occurrence of floods using copula functions of two variables of volume and flood sediment in the Qarasu River catchment in a statistical period of 41 years. The results revealed that the Weibull distribution is the most suitable marginal distribution, and the Frank copula function can well create the bivariate distribution of volume and flood sediment. Furthermore, the estimated return period of the bivariate showed that the sediment parameter has a significant effect on the return period. However, it is decreased in the case of {or} and increased in the case of {and}.