Presentation and review of some methods for regional flood frequency analysis

Regional flood frequency analysis is used for the estimation of floods at sites where little or no data are available. It involves the identification of groups (or regions) of hydrologically homogeneous catchments and the application of a regional estimation method in the identified homogeneous region. The main objective of this study is to systematically compare various regional flood estimation procedures with special emphasis on data from the two Canadian provinces, Quebec and Ontario. Four methods for delineating homogeneous regions and seven regional estimation methods were investigated and these methods are described here. The project was specifically aimed at developing new regional estimation techniques (or combinations of techniques) and to improve existing methods. Special emphasis has been put on non-parametric methods as an alternative to classical parametric techniques. The use of partial duration series data in a regional context has also been thoroughly explored. An accompanying paper (GREHYS, 1996, J. Hydrol., 186: 85–103) provides a detailed description of the inter-comparison approaches and of the results obtained in the study.