A distributed hydrological model for urbanized areas – Model development and application to case studies

SummaryThe circulation of rainwater within urban areas has not yet been described in a detailed manner, as studies on this topic often remain limited to the runoff on impervious surfaces. The need for innovative and sustainable methods of water management has incited increased research efforts on the hydrological processes at work in urban areas. A distributed hydrological model based on information supplied by current urban databanks has been developed in this aim. The components of rainwater flux (i.e. surface runoff, soil runoff, drainage flow via the sewer, and evapotranspiration) as well as information on the hydric state of the urban soil (saturation level, storage capacity) are modeled at the parcel scale, and then coupled with a detailed description of the hydrographic network. This model runs continuously and has been intended to reproduce hydrological variables over very long time series. In order to evaluate this model, it has been applied at two different scales, on two urban catchments of various land use, where hydrological data were available. This evaluation is based on the comparison of observed and simulated flowrates and saturation levels, and details the various compartments (soil, impervious or natural areas) to the outflow. This study shows the importance of water fluxes often neglected in urban hydrology, such as the evapotranspiration or the soil infiltration into sewers. This first evaluation has highlighted the capability of mapping most of the hydrological fluxes on urban catchments, such as the capacity of soil to store water.