INTER-COMPARISON OF REGIONAL FLOOD FREQUENCY PROCEDURES FOR CANADIAN RIVERS

This paper presents the results of a comparison of regional flood freq uency procedures. The accuracy of regional quantile estimators as pred ictors of population quantiles at a number of key sites is examined. R eference sites have been selected with the basic requirement of at lea st 35 years of local flood records. Accurate at-site estimates of popu lation quantiles can therefore be obtained at these locations. The reg ional estimators are used ignoring the local data. This is equivalent to flood estimation at an ungauged site. The case of some local inform ation (10 years of records) is also considered. The bias and variance of the regional estimators are evaluated by comparing at-site and regi onal estimates. Two methodologies have been devised for the comparison of regional models: a regional bootstrap approach and an empirical Ba yes approach. For each approach, a detailed description of the results of the various methods considered in the study is provided. It was sh own that, in general, the two methodologies lead to similar results.