Annual maxima and partial duration flood series analysis by parametric and non-parametric methods

Abstract

Annual maxima (AM) and partial duration (PD) flood series aer modelled by parametric and non-parametric methods. In PD analysis the number of threshold exceedances is assumed to be Poisson distributed; the peak exceedances are described by the generalized Pareto (GP) and non-parametric (NP) distributions. The generalized extreme value (GEV) and non-parametric (NP) distributions are used to describe the AM series. L-moments are employed for parameter estimation for GEV and GP distributions. Analysis of data from the provinces of Quebec and Ontario, Canada, shows that both AM and PD series can be inferred as being unimodal and bimodal, both of which can be described by the NP method. Also, this method is found not to be sensitive to choice of threshold level; however, it was also observed that parametric methods cannot detect biomodality, give different quantile estimates for AM and PD data and PD estimates are sensitive to the selection of threshold level. Therefore, the NP method is more advantageous than the parametric methods in flood frequency analysis of both AM and PD series.