Simulating floods in ephemeral streams in Southern Italy by full-2D hydraulic models

The simulation of flood events is essential for risk prevention and land regulation purposes. Traditionally, it is performed by decoupling the prediction of hydrograph(s) at some section(s) of the waterway(s) from the delineation of downstream flooded areas by using synthetic hydrologic models and hydraulic inundation models, respectively. In the case of the Apulian ephemeral streams (Southern Italy), the application of such an approach is prevented by the lack of monitored rainfall-runoff data and the discrepancy of some key underlying hypotheses. Thus, the suitability of integrated (hydrologic-hydraulic) full-2D models is investigated here by assuming the rainfall as the only external forcing term into each element of the bi-dimensional domain, where the shallow water equations are integrated. This permits the reproduction of runoff generation, propagation and, eventually, flooding at any point of the catchment. Several model runs under many combinations of hydrological losses and surface roughness parameters demonstrate that the full-2D approach realistically reproduce catchment hydraulic behaviour and predicted inundated areas of Apulian ephemeral streams, thus being of direct relevance for basin management purposes.