THE DESCRIPTION OF URBAN AREAS IN FLOOD INUNDATION MODELLING

Flash‐flood phenomena induced by climate change and rapid urbanization processes are expected to threaten people living in flood‐prone areas in the near future. The increasing awareness about the importance of integrated flood risk management strategies has further motivated the development of hydrodynamic models to reliably predicting flooding scenarios in urban areas. This paper compares the performances of three techniques, which can be adopted within shallow water models, to reproduce the propagation of a flood wave on a real urban layout. The first method resolves the building geometries on a fine mesh, the second one locally assigns higher roughness coefficients and the third one describes building alignment by means of porosity parameters. The simulations were carried out using the parallel 2D shallow water model PARFLOOD. The results show that the porosity approach enables capturing the relevant features of the flooding, both inside and outside the urban area, better than the method based on a local roughness increase. Moreover, the porosity approach allows reducing the run times up to 600 times if compared to the resolved building technique.