Exploring the signature of climate and landscape spatial variabilities in flash flood events: Case of the 8-9 September 2002 Cevennes-Vivarais catastrophic event

This paper investigates the signature of climate and landscape spatial variabilities on flash-floods events. Through the case of the catastrophic 8-9 September 2002 Cevennes-Vivarais event, the impact of the space-time structure of the rainfall on the distributed hydrological response is evaluated. Comparisons are made with other spatial variabilities that may also contribute to the flash-flood generation such as initial soil moisture condition, topography, landscape characteristics, hydraulic processes. A model-based approach is suggested and was applied on 19 catchments. It is shown that the spatial variability of rainfall and of the initial soil moisture conditions were both of first order in the flash-floods generation and that the spatial variability of landscape properties were of second order. This methodology will be applied on other extreme hydro-meteorological events surveyed by the OHM-CV (Cevennes-Vivarais Mediterranean Hydrometeorological Observatory), with the aim of providing clues on processes that should be particularly focused when measuring and simulating such intense mesoscale meteorological events.