The proposed methodology aims to simultaneously simulate wave overtopping and the resulting flood in an urban area, with respect to chronology and buildings effect. Based on a downscaling approach, this method uses a time-dependent phase-resolving model to simulate dynamically the flows on a DEM including buildings. Applied to the Johanna storm in Gâvres (France), this method allowed for obtaining very realistic results in terms of water depths and flow velocities at a very high resolution.