Upgrade of harbor rubble mound breakwaters in the context of climate change

Despite the importance of upgrading aging harbor rubble mound breakwaters under the effects of climate change, to the author's best knowledge a comprehensive methodology for the design of upgrading solutions able to deal with the uncertainties linked to the current state of existing structures, the intrinsic variability of external loading, and the empirical nature of the design formulas has not been proposed yet. In this context, the present work aims to contribute to the definition of a methodology for the assessment of the performances of upgrading solutions of existing harbor rubble mound breakwaters, also considering the effects of climate change. First, a novel easy-to-use method for the assessment of the current state of existing structures is presented, which is based on the diachronic analysis of field aerial and UAV data. The obtained information are useful for the selection of the most appropriate upgrading concepts for the considered breakwater, as demonstrated by the results of the application to the case study of the Catania harbor breakwater. Then, a general framework of the variation of past and future sea level and wave climate due to climate change in the Italian seas is provided, which allows the definition of the external loading to be used for the probabilistic design of the upgrading options. Results on the behavior of upgraded rubble mound structures under wave attack, acquired through the composite modeling of the upgraded Catania harbor breakwater, are also presented. Two-dimensional experiments have been performed, considering six different upgraded configurations. Both traditional and novel techniques have been employed for the analysis of the armor layer damage dynamics. Furthermore, the mean overtopping discharge has been measured to compare the hydraulic performances of the tested structures. A deeper investigation of the overtopping phenomena, at both laboratory and prototype scale, has been conducted, through two-dimensional numerical simulations based on the solution of the VARANS equations. The outcomes of the composite modeling have allowed us the definition of site-specific empirical formulas for the design of upgrading solutions. A probabilistic method for the assessment of the performances of upgrading solutions under both present and future climate, based on a Monte Carlo simulation technique, is described, together with the outcomes of the application to the case of the Catania harbor breakwater. Finally, some general findings have been derived from the analysis of the considered case study, concerning the armor layer damage dynamics, the importance of using specific design formulas and the necessity of maintenance interventions for existing harbor breakwaters.