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Benefit of convective-scale meteorological models for Mediterranean flash-floods forecasting : towards an ensemble discharge forecasting system in the Cevennes-Vivarais region.

Apport des modèles météorologiques de résolution kilométrique pour la prévision des crues rapides méditerranéennes : vers une prévision d'ensemble des débits en région Cévennes-Vivarais

Abstract : The northwestern Mediterranean is prone to heavy rainfall events that lead to flash-floods over the small to medium basins of the region. The first part of the thesis is to assess the benefit of using the ISBA-TOPMODEL coupled system to simulate this type of flooding on three watersheds of the Cévennes-Vivarais region. mediterranean flash-floods. The potential of convective-scale deterministic forecasts (such as those provided by the French AROME model) for flow forecasting is discussed in the second part of the Ph.D work. It is shown that location errors in the rainfall forecast propagate into the hydrologic model to grow. In the last part, to quantify these uncertainties, a perturbation method of the AROME precipitation forecast is is developed. The rainfall scenarios are then igested into ISBA-TOPMODEL to generate an ensemble of dicharge forecasts. The resulting discharge ensembles are found better than the discharge simulation driven by the single deterministic operational AROME forecast.