Crown Wall Modifications as Response to Wave Overtopping under a Future Sea Level Scenario: An Experimental Parametric Study for an Innovative Composite Seawall

The overtopping phenomenon at the rear side of breakwaters has particular importance in harbor protection. Undoubtedly, this topic needs to be taken even more seriously, considering the sea level rise. The present study focuses on the effectiveness in the reduction of the wave overtopping of a triangular parapet placed on the top of an innovative concrete superstructure. The last is part of the OBREC device (Overtopping BReakwater for wave Energy Conversion), an overtopping structure which is integrated into a traditional rubble-mound breakwater, to convert wave energy into electricity. Parametric laboratory tests, including the influence of water depth, have led to the evaluation of the accuracy of the main literature formulations and to the introduction of a new overtopping formula to take into account the influence of the parapet geometry. The results highlight the capability of the parapet in significantly increasing the hydraulic protection compared to a breakwater with a traditional crown wall. The findings from this work are expected to support in promoting and developing adaptive management strategies for existing coastal defenses and smart approaches in the construction and maintenance of new ones, with special reference to future sea-level-rise scenarios.