Working of defence coastal structures dissipating by macro-roughness

The working features of innovative coastal defense structures that can dissipate the energy of incoming waves by the action of large-scale bottom unevennesses rigid blades covering the lower half of the water depth were investigated by means of a laboratory experimental campaign. The goal of the study was to characterize the ability of the structures to efficiently reduce the wave height with a minimal change in the mean water superelevations. Similar wave height reductions were achieved for both vertical and inclined blades; their efficiency was slightly superior to that of traditional submerged rubble-mound breakwaters of the same cross-shore extension. For the incident waves examined, very low mean water elevations were observed inshore of the structures, with the inclined blades producing the smallest values. These results suggest that the structures analyzed here could represent an alternative to submerged rubble-mound breakwaters from a hydrodynamic point of view to protect coastlines prone to erosion with minimal risk of dangerous rip currents.