Coupling Flood Propagation Modeling and Building Collapse in Flash Flood Studies

Flash flood events threaten the safety of people either because of the direct impact of the flow on people and car stability or because of structural damages to buildings. Traditionally, buildings stability is assessed with ex post analyses by vulnerability models applied to the results of hydraulic models where buildings are permanently present on the flooded domain. However, in the case of building collapse, the geometry of the computational domain should be adapted during the simulation and, accordingly, a more realistic approach would require the coupling of hydraulic modeling and structural analysis. This paper provides an example of a simple methodology implementing this procedure in HEC-RAS 2D using the results from a physically-based structural vulnerability model for masonry buildings. After positively testing the capabilities of the solver to model the flow field around isolated obstacles as well as the flow field in urban districts on complex bathymetries, the proposed procedure is applied to the reconstruction of the flood event in the Corna di Darfo village (Northern Italy) after the collapse of the Gleno dam in 1923.