REGIONAL ESTIMATION OF FLOOD QUANTILES BY CORRESPONDENCE-ANALYSIS

In this study, the problem of regional flood estimation at ungauged si tes is examined in the metric space defined by the application of corr espondence analysis to physiographic and climatic characteristics of d rainage basins. The selection of this technique was dictated by its hi ghly descriptive ability and the stability of the results it yields. T he transposition of flood quantiles at an ungauged site is carried out via the corresponding weighted averaged quantiles observed at a neigh boring sites (s fixed). The fundamental question regarding the optimal size of the neighborhood to be used in flood estimation at a particul ar site is addressed in the discussion of results obtained from the ap plication of the methodology to the drainage basins in the province of Ontario, Canada. In addition to identification of dependence structur es between the characteristics of the drainage basins considered, the correspondence analysis allows to identify homogeneous groups within w hich floods at an ungauged site are represented satisfactorily by the weighted averages of floods observed at neighboring sites. Comparison between results obtained and those from multiple regressions on the en semble of basins shows that the proposed methodology can be adequately used to estimate flood quantiles.