Flood frequency analysis: The Bayesian choice
Résumé
After an introduction to the traditional flood frequency analysis methods, this article discusses their limits and the risks associated with their thoughtless use: overconfidence in the estimated values of flood quantiles or return periods and systematic underestimation of risks. The article then presents and illustrates the added value of modern Bayesian flood frequency inference procedures that are statistically consistent, numerically accurate, and now computationally affordable. The implementation of such methods shows that estimated flood frequencies, based on observed samples of limited size, are generally affected by large uncertainties. This acknowledgement should be an incentive for increasing the size of the analyzed samples through a more systematic use of historic information as well as regional approaches in flood frequency analyses. It also clearly points out that the margin of errors should be considered when using inference results for design or risk assessment purposes. Several pieces of software are now available to conduct Bayesian flood frequency analyses relatively straightforwardly. There is no remaining obstacle to the implementation of these modern approaches in operational hydrological studies.
Cette article présente et discute les qualités et les limites des méthodes d'analyse fréquentielles des débits utilisées en hydrologie. Il expose notamment l'intérêt des approches Bayesiennes qui permettent une évaluation des incertitudes associées à ces analyses fréquentielles. L'article se termine par l'illustration de l'importance de la prise en compte de ces incertitudes dans les études de risques ou de dimensionnement.
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