Study of the water budget of streets: experimentation and modelling

The study of two stretches of street during 38 months has been performed to analyze the hydrological behavior of streets during rain events. The results show that runoff coefficients are very variable and runoff losses may be important. In order to better understand this behavior, a physically based model has been used. This model, BiL, combines a porous media flow module with a surface runoff module. The lateral runoff transfer in the lateral gutter is approximated by the Muskingum model. Evaporation is simulated by an adaptation of the Penman method. A sensitivity study shows that the model is mainly sensitive to saturated hydraulic conductivity of the asphalt pavement and to the storage capacity. The comparison of simulated and observed data gives good results for the runoff outflow at a 3 minutes time step. Nevertheless, the simulation results are less encouraging for the runoff coefficient. This study of the water budget of two street stretches during a time period of 38 months indicates that the infiltration and evaporation represent between 20 and 30% of rain.