Physical model tests have been performed to study wave overtopping at rubble mound breakwaters, including breakwaters with a crest wall, breakwaters with a berm, and breakwaters with a crest wall and a berm. For rubble mound structures with a protruding crest wall or with a stable berm, limited information is available in literature even though protruding crest walls and berms clearly affect wave overtopping discharges. Adding a crest wall to an existing structure, increasing the height of a crest wall, adding a berm, or increasing the width or height of a berm, can be effective measures to account for effects of sea level rise if the sea level rise appears to be more severe than the amount of sea level rise for which the structure was designed for. The present wave flume tests were used to develop guidelines for rubble mound breakwaters, including breakwaters with a crest wall or with a berm. The relative height of the protruding part of a crest wall dominates the effect of a crest wall. The berm width, berm level and wave steepness all affect the influence of a berm on the wave overtopping discharge. Moreover, it was confirmed that the wave steepness also affects wave overtopping discharges for rubble mound breakwaters without a berm or without a crest wall. The developed set of expressions for rubble mound structures has also been validated based on existing data for oblique wave attack on rubble mound breakwaters with a crest wall.

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The wave overtopping discharge during extreme storm conditions largely determines the required crest height in dike reinforcement projects. In case of future sea level rise, crest heights should be increased significantly, which potentially leads to significant costs and environmental and societal consequences. The available empirical design formulas for wave overtopping are based on data sets that show a relatively large scatter, potentially leading to inefficient design of crest level heights. In this paper a novel approach is presented in which the water depth in front of the dike is incorporated in the wave overtopping formulation leading to a lower scatter and in the case of shallow foreshores also a lower required crest height. The present approach is based on the use of an existing overtopping database (CLASH-EurOtop) and additional generated data by conducting physical experiments(Scheldt Flume of Deltares) and numerical experiments (OpenFOAM) in which the water depth was varied systematically for a variety of test conditions. Based on these three approaches, it is concluded that the wave overtopping discharge (q) is dependent on the water depth. Since this dependency is not included in the present wave overtopping formulation, this paper suggests a method to incorporate this dependency in the present existing formulas by implementing an influence factor for water depth (γd).@en

This paper describes a method of determining the reaction forces of a vertical structure with an overhang to impulsive wave impacts. The aim is to develop a method to design a hydraulic structure exposed to the impulsive wave impact. At present, there is a lack of guidelines on the designing and verification with such a purpose. The impulse of the impact is taken as the primary design variable to estimate the impulsive reaction force instead of peak impact forces. By using extreme value analysis (EVA), the characteristic impulse (e.g., I _im,0.1% ) can be determined. Then a simple structure model is used for obtaining reaction forces to the characteristic impact impulse. The sum of the impulsive reaction force and the quasi-steady wave force could represent the total reaction force, which can be used as a design load on the structure. The advantage of using the impact impulse could give an approach in which several aspects of the impulsive wave impact force can be incorporated better, like determining the exceedance probability of a certain load, incorporating the flexibility of the structure and correcting possible scale effects in small scale hydraulic models. The proposed method based on the characteristic value of the I _im,0.1% is applied to forces measured in a small scale model of the Afsluitdijk discharge sluice, and compared well to a full-time domain solution. The results indicate the initial assumption that using the impact impulse of the impact as the primary design variable, it is possible to estimate the dynamic response of the structure.

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