Estimation régionale de quantiles de crues par l'analyse des correspondances

Abstract

In this study, the problem of regional flood estimation at ungauged sites is examined in the metric space defined by the application of correspondence analysis to physiographic and climatic characteristics of drainage basins. The selection of this technique was dictated by its highly descriptive ability and the stability of the results it yields. The transposition of flood quantiles at an ungauged site is carried out via the corresponding weighted averaged quantiles observed at s neighboring sites (s fixed). The fundamental question regarding the optimal size of the neighborhood to be used in flood estimation at a particular site is addressed in the discussion of results obtained from the application of the methodology to the drainage basins in the province of Ontario, Canada. In addition to identification of dependence structures between the characteristics of the drainage basins considered, the correspondence analysis allows to identify homogeneous groups within which 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 ensemble of basins shows that the proposed methodology can be adequately used to estimate flood quantiles.