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Flash floods represent one of the most destructive natural hazards in the Mediterranean region. These floods result from very intense and spatially heterogeneous rainfall events. Distributed hydrological models are valuable tools to study these phenomena and increase our knowledge on the main processes governing the generation and propagation of floods over large spatial scales. They are generally built using a bottom-up approach that generalizes small-physics representations of processes. However, top-down or data-driven approach is increasingly shown to provide also valuable knowledge. A simplified semi-distributed continuous hydrological model, named SIMPLEFLOOD, was developed, based on the simple dynamical system approach (SDSA) proposed by Kirchner (WRR, 2009, 45, W02429), and applied to the Ardèche catchment in France (2388 km 2). This data-driven method assumes that discharge at the outlet of a given catchment can be expressed as a function only of catchment storage. It leads to a 3-parameter nonlinear model according to rainfall and runoff observations. This model was distributed over sub-catchments and coupled with a kinematic wave based flow propagation module. The parameters were estimated by discharge

International audienceThis paper addresses the impact of the source and processing method of land use information for hydrological simulations on the long-term water balance of the Yzeron peri-urban catchment (150 km2), located near Lyon, France. A customised version of the distributed hydrological model J2000 was used to perform simulations at a daily time step. Five land use data sets obtained from aerial photographs BDOrtho@IGN and satellites Quickbird and Spot for the year 2008 are compared. The paper presents the methodology for model setup and the simulation results for the main water balance components of the catchment: total runoff at several gauging stations, runoff components, evapotranspiration and soil moisture. The model evaluation against discharge measurements at six locations shows a reasonable agreement between simulated and observed values, in particular for general seasonal variations, low flow periods and simulation of runoff components (surface runoff, interflow and base flow), with Nash–Sutcliffe efficiencies ranging from 0.25 to 0.51 at the daily time step and 0.46–0.82 at the monthly time step. The comparison of the model outputs for the various land use maps shows that the total discharge is not very sensitive to the data set used (−4.88% to 4.65% at the catchment outlet), except in a small and more densely urbanised sub-catchment for which a significant impact of image resolution on simulated flow is detected (+25.81%). For all gauges, the results also highlight the sensitivity of the modelled flow components, in particular regarding the amount and seasonal dynamics of surface runoff generation (8–44% of total flow at the catchment outlet depending on the data set used). As a conclusion, land use information should be selected and processed with care, with respect to the objectives of a given study, and the sizes and urbanisation rates of the target sub-catchments