Probability-Weighted Moments without Plotting Position Formula

A new method of parameter estimation for any probability distribution used in flood frequency analysis is proposed as a modification to the conventional probability-weighted moments (PWMs) method. The PWMs can be estimated by computing either the nonexceedence or the exceedence probability of each element in the sample series using the distribution itself instead of a plotting position formula. The formulation and solution of the suggested method is given for the general extreme-values distribution. Experiments on 1,000 short-length synthetic series indicate that the proposed method predicts the 1,000-yr return-period events better than both the maximum-likelihood and the conventional PWMs methods.