Integrated assessment of the hydraulic and structural performance of crown walls on top of smooth berms

The introduction of crown walls with parapets on top of dikes and berms represents a relatively economic and efficient solution to reduce the wave overtopping discharge and therefore the hazard exposure of the inshore areas. However, the inclusion of parapets and bullnoses leads to increased wave pressures on the crown walls that may compromise their resistance. Literature studies have so far addressed separately the effects of crown walls, parapets and bullnoses on the hydraulic efficiency and on the structural stability. The purpose of this contribution is to fill the gap between these two streams of research, proposing an integrated analysis of the wave loads and of the wave overtopping discharges at smooth berms that are supposed to be upgraded with crown walls and parapets. The study is based on the results of a recent campaign of 2D small-scale laboratory tests on wave overtopping at smooth berms with crown walls under breaking and non-breaking waves. Relevant parameters of the sensitivity analysis are the berm slope, width and relative emergence, the crown wall height, and the inclusion of a parapet. The main outcome of the investigation consists of a set of indications for the optimized reduction of the discharge with a limited increase of structural loads. A simple and practical formula linking forces and overtopping discharges at walls and highlighting the strict correlation between the two variables is also proposed.