Runoff Generation on a Urbanizing River Basin Formation de ruissellement sur un bassin versant péri- urbain

Due to the expansion of urbanization, peri-urban zones face a quick land-use change. The control over this phenomenon has become a major issue for flood and water pollution management. Nevertheless, so far we are still on the pursuit of a well adapted model to these particular basins. We aim to develop such model by studying the Chezine basin, in the framework of the French national project AVuPUR (ANR-VMCS, 2008-2010). A 7-year data analysis unveils a specific behavior: first, rain events displaying one single peak produce one or two distinct peak discharge on the hydrograph ; second, the lag-time of the basin, usually close to 1 hour, sometimes exceeds 6 hours. Based on geomorphologic and hydro-meteorological data analyses we made some hypotheses to explain the different shapes that the hydrological response of the Chezine Bassin may present. The localization of urbanization throughout the basin and its pre-event moisture state seem to play a crucial role on the variability of hydrological responses. The application of the First Differenced Transfer Function confirms the existence of different shapes of transfer functions for the basin according to its initial moisture state. Therefore we conclude that the hypotheses here presented should not be neglected in the current pursuit to develop a well adapted model for suburban river basins.