New look at regional flood-frequency relations for arid lands

A new method is proposed that combines records for several streamflow-gaging stations, as in the station-year approach, and produces regional flood-frequency relations using an iterative regression technique. This technique eliminates the need to extrapolate the flood-frequency relation to the flood probability of interest. The resulting multiparameter regional flood-frequency relation is based on all the available annual peak-flow data. The method was applied to a group of records from 42 gaging stations in Nevada with many years of no flow and with many poorly defined flood-frquency relations. One- and two-parameter models were developed in which much of the variance in peak discharge is explained by drainage area. The log-Pearson type III and Weibull probability distributions were used in the models. Part of the error is directly assessed using randomly selected subsamples of the annual peak discharges. -from Authors