Evolution de la méthode du gradex : approche par type de temps et modélisation hydrologique

Evolution of the GRADEX method : improvement by atmospheric circulation classification and hydrological modelling

EDF-DTG 21, Avenue de l’Europe – BP 41 – 38040 GRENOBLE CEDEX 09

Auteur de correspondance : emmanuel.paquet@edf.fr

Abstract

The physico-statistical approach of the flood prediction by the GRADEX method seems very effective : it’s very straightforward and makes it possible to obtain completely coherent results by a robust and very readable step. To assess the quality of the approximation carried out by this model, some improvements have been tested on two significant points, leading to the SCHADEX method. SCHADEX is based on the study of the risk of precipitation related to each type of atmospheric circulation. This typology highlights the weather configuration of stronger rainfall risk and therefore increases the probabilities of extreme rains. The runoffs resulting from these precipitations, depending on highly variable hydrological conditions, are estimated by the MORDOR hydrological model. The results show a fast increasing of the rainfall efficiency going from common to rare floods. But this increase is smoother than with the initial GRADEX approach, which moderates the impact of heavier extreme rainfall.