A hierarchical approach to regional flood frequency analysis

Abstract

A hierarchical approach to regional flood frequency estimation is described, where higher‐order parameters controlling the skewness of annual maximum floods are determined from larger regions than are used for determining parameters controlling the coefficient of variation. Procedures based on two‐component extreme value and generalized extreme value distributions are developed, and it is shown that dividing a region into subregions to estimate some parameters can lead to more precise quantile estimates. The practical problem of defining the optimum number of subregions is discussed.