Three-dimensional CFD modelling of urban flood forces on buildings: A case study

Italy is among the countries most likely to be exposed to high hydrogeological risk. The recent 2018 Hydrogeological Disruption Report by ISPRA (Higher Institute for Environmental Protection and Research) states that about 90% of Italian municipalities fall within areas with hydrogeological risk, that is where the probability of floods/landslides is high (level P3) or very high (P4) or the hydraulic hazard is of medium level. Floods are the most severe and frequent phenomena affecting landscapes, mainly if they occur in urban contexts. Urban development, if nature-based solutions are not taken into account, determines an increase in the impermeable surface, with the effect of reducing the infiltration and water evaporation, and consequently with an increase in runoff peaks and decrease of the concentration times. In this framework, the work here presented numerically analyses the effect of floods in an urban basin, in term of their three-dimensional interaction with buildings. The site under study is Cervinara, a municipality in the Campania region, Italy, hit by severe floods in 1999. Flow peaks were calculated using the VAPI procedure, a regional methodology based on two-component extreme value (TCEV) distribution. The results show that the level of exposure of the buildings, evaluated by calculating the thrust of the interacting water on the exterior walls, is influenced by the local three-dimensional kinematics.