Flood hazard mapping in lowland areas: influence of treating artificial embankments as erodible elements

In floodable lowland areas, the inundation dynamics can be significantly influenced by artificial embankments (canal levees, roads/railways). Simulations performed for flood mapping are usually based on the unphysical assumption that these elements are resistant to erosion/breaching. This paper aims to analyse the influence of the possible erosion of embankments on flood hazard mapping, by comparing two-dimensional simulations performed with embankments assumed as either “non-erodible” or “erodible”, focusing on two inundation scenarios of different magnitude in a study area in Italy. Results show that, when the embankments’ erosion is neglected, the flood extent and the hazard classification can be underestimated and the flood arrival time can be anticipated in the regions originally protected by embankments, especially when the maximum water depths are comparable to the embankments’ elevation. Therefore, this exploratory work suggests that this process should be at least kept in mind in the context of flood hazard assessments.