Abstract : M.4
Flash flood forecasting within the PREVIEW project: high- resolution hydrometeorological simulations

Béatrice Vincendon, Katia Chancibault, Véronique Ducrocq, Ludovic Bouilloud, Georges-Marie Saulnier, Matthieu Lelay, Sandrine Anquetin, Vassiliki Kotroni, Konstantinos Lagouvardos, Massimo Milelli, Silke Dierer, Davide Rabuffetti
GAME/CNRM (Météo-France, CNRS)

PREVIEW is a European Commission FP6 Integrated Project which aims at developing, on a European level, new geo-information services for natural and industrial risk management. The work package WP4340 focuses on forecast of Mediterranean flash floods. Phase 1 is devoted to the assessment of the usefulness of kilometric scale atmospheric model forecast for hydrological applications and to the development of hydro-meteorological coupled systems based on high-resolution atmospheric models and hydrological models able to reproduce the hydrological behaviour of Mediterranean catchments.

Four high-resolution models at 2-3 km resolution have been run on five flash-flood cases over the French Cévennes-Vivarais and Italian Piemonte regions ; models are MM5 (by NOAA), Almo2 (by MeteoSwiss), Meso-NH (by Météo-France) and LAMI (by Arpa Piemonte). The various hourly precipitation forecasts are supplied as input to two hydrological models to evaluate through the simulated discharges the value of high resolution forecasts for hydrological forecast purpose. Companion presentations will detail results with Almo2 and LAMI. We focused here on the Meso-NH and MM5 results, including their hydrological answer when precipitation forecasts are used as input to the hydrological model TOPMODEL. In particular, sensitivity to various initial atmospheric fields are examined.

To investigate the benefit of more advanced coupling strategies, a full 2-way coupling between the hydrological model TOPMODEL and the Surface Vegetation Atmosphere Transfer (SVAT) scheme of Meso-NH (i.e. ISBA). The 2-way coupler manage the different grids (2.5 km for ISBA vs 50 m for TOPMODEL) ; the water budget is governed by ISBA whereas TOPMODEL performs the lateral soil water distribution over catchments and calculates the saturated areas used by the SVAT to compute the run-off supplied to the flow routing model. Preliminary results show that more realistic water soil contents are obtained with the full 2-way coupling.