Assessing the Feasibility of San Salvatore Dam Removal on the Trebbia River: A Study of River Restoration Through Hydrodynamic and Morphodynamic Simulation.

Dam removal has garnered significant attention as an alternative option for river restoration over several years. To that end, the Open Rivers Programme has proposed an innovative initiative in Italy to restore the Trebbia River by demolishing the obsolete San Salvatore Dam. This thesis delves into a comprehensive assessment, including both one dimensional and two-dimensional hydrodynamic modeling, alongside 1D morphodynamic numerical simulations, to evaluate the feasibility of removing such a dam and its potential impact on the downstream due to the impounded sediments transport. This thesis includes a thorough set of studies, starting with the acquisition of point clouds aided by unmanned Aerial Vehicles (UAVs) and continuing with post-processing using CLOUDCOMPARE to generate a high-resolution Digital Terrain Model. The grain size distribution near the dam section was determined using the BASEGRAIN software. The primary goal of the thesis was to evaluate the volume of sediment transport and the possible geomorphic and flood inundation impacts to the downstream and the response of time scale of sediment transport to reach nonlinear adjustment towards equilibrium of the geomorphic evolution of riverbed. For the same reason, the 1D hydrodynamic model in HECRAS was developed to calculate the discharge that initiates sediment transport in this specific case that contains the bypass connecting upstream and downstream of dam section. The discharge calculated was then integrated to see the geomorphic evolution of riverbed and sediment transport volume through 1D morphodynamic simulations using MATLAB software. Finally, the results obtained from 1D morphodynamic simulations were used for 2D hydrodynamic modeling in HECRAS to observe the spatial inundation map and flow depth before and after dam removal. It was found from the analysis that the volume of sediment transport downstream of the dam after removal was low and the results showed no significant changes in spatial flood mapping and the flow depth after the sediment transport. However, it still requires the detailed quantification of the amount of sediment that could be deposited in the pools and riffles present downstream the dam and the ecological response after post-dam removal. The results strongly indicate minimal impacts to the downstream due to the sediment transport after dam removal. This evidence robustly bolsters the decision to proceed with the San Salvatore dam removal project for river restoration proposed by the Open rivers Programme.