MODELLING THE WAVE OVERTOPPING DISCHARGE AT CROWN WALLS WITH GENETIC PROGRAMMING

The upgrade of existing coastal defense structures by including crown walls and parapets may represent an effective and economic solution to reduce the wave overtopping discharge q. The first systematic work was carried out by Van Doorslaer et al. (2015), VD, hereinafter. The study experimentally examined the typical defense structures of the Belgian coasts, characterized by smooth dikes, with a long and mildly sloping promenade above the still water level. The authors hypothesized to upgrade the existing structures by constructing a crown wall directly on the slopes or at the end of the promenades, including or not a bullnose, bn hereinafter. The study prompted the first organic set of formulae parametrizing the combined effect of wall, bn, and promenades into a reduction coefficient γ* adopted in the EurOtop (2018) manual and applied to the formula for q by Van der Meer & Bruce (2014). Recently, on the basis of a new set of experimental and numerical investigations, Zanuttigh & Formentin (2019) developed a coefficient γ*GP for the parametrization of the effects induced by berms or promenades, crown walls and parapets on the average q. The formula for γ*GP was obtained from the Genetic Programming (GP) technique and it was conceived to be included in the q formulae by EurOtop (2018).