Regional flood frequency analysis based on a Weibull model: Part 2. Simulations and applications

Regional flood frequency analysis based on an index flood assumption and a two-parameter Weibull distribution was studied and simulation experiments w ere performed to compare the sample properties of quantile estimates based on the maximum likelihood (ML), moments (MOM), and probability weighted mom ents (PWM) methods, and to determine the applicability of the asymptotic va riances of quantile estimators obtained for each method for finite samples. Results of these experiments showed biases and mean square errors vary wit h sample size, number of sites, non-exceedance probability, shape parameter , and estimation method. The ratio of the asymptotic variance (Avar) and th e mean square error has been examined to see how well Avar represents the v ariability of quantile estimators for finite samples. In general, asymptoti c formulas are quite good even for samples of size 25. The proposed regiona l model and estimation procedures are illustrated by analyzing some actual flood data from Illinois and Wisconsin. (C) 2001 Elsevier Science B.V. All rights reserved.