Overtopping of Berm Breakwaters Extension of Overtopping Formula

In this paper is presented an improved version of the overtopping formula by Lykke Andersen & Burcharth (2004)valid for berm breakwaters with initial slopes of 1:1.25. In the present paper guidelines is given on how to modify the formula to take into account the initial slope angle. Further the formula is improved so it gives reliable estimates also for more stable structures. The extension of the overtopping formula is based on analysis of front slope stability data from many different data sets. In most cases there is only a small difference between the Lykke Andersen & Burcharth (2004) formula and the present improved formula. However, for a more stable structure and low wave steepness the improved formula performs better. Six different data sets are used to study the validity of the Lykke Andersen & Burcharth (2004) formula, the present improved formula and the CLASH neural network model. The present improved formula seems to be the best choice. The CLASH NN-Model performs very well for berm breakwater data sets included in the fitting of the NN-Model, but much worse for those not included. This demonstrates some degree of overlearning of the neural network due to limited data for berm breakwaters.