Design of multipurpose coastal protection measures at the reno river mouth (Italy)

This work presents the approach strategy for the optimization of the coastal defence at a specific site in the Northern Adriatic Sea, the Reno river mouth (Italy). The area is extremely dynamic and vulnerable since exposed to several climate change related effects and in the last decades has suffered strong erosion processes. A rocky revetment covered by a superficial bituminous layer protects this coastal area, but the bad state of conservation makes this defense technique inadequate also during ordinary events. In addition, important morphological variations at the mouth (i.e., the human demolishing of the final part of the right riverside) affected the stability of the protection works and compromised the inland safety. The analysis of multipurpose coastal schemes for flood mitigation and coastal defence of the area is carried out by means of the well-known commercial software MIKE21, that was implemented to simulate waves (SW), currents and levels (HD) and sediment transport (ST). Different sea events from NW (Bora) and SE (Scirocco) were reproduced in the site, also including tidal level, storm surge and river discharge associated to the reproduced storm. Current configuration of the area and alternative defence schemes (i.e. breakwater, groins) to improve coastal protection were simulated and the numerical results were compared in terms of wave load, inundation rate and bed level change. The condition of Bora with the simultaneous presence of high tidal level results to be the most severe event, since the developed longshore current contrasts the river outflow, leading to a high probability of fluvial flooding of the area. The comparative numerical analysis of the different scenarios and configurations allows estimating the optimal coastal protection scheme both in terms of flooding mitigation and erosion reduction and the implemented model can be a useful tool for future studies regarding a so vulnerable and dynamic area.