Application of laboratory dam break experiments to non-impulsive wave overtopping

This study evaluates the novel application of a laboratory dam break flume to replicate non-impulsive wave overtopping of coastal structures, without geometric scaling. The bore generated by the dam break flume is characterised and compared with overtopped bore parameters from the literature. For a more detailed wave-by-wave comparison across a broad parameter space, XBeach non-hydrostatic was used to simulate non-impulsive waves overtopping smooth-sloped coastal structures. From the XBeach dataset of individual overtopped bores, empirical relationships were derived to predict maximum water depth, velocity and flow rate using bore volume, offshore wave parameters and coastal structure parameters. Compared to the XBeach dataset, the flume bores replicate the overtopped bore flow characteristics for gentle slopes 6 ≤ cot ( α ) ≤ 10 , with peak wave period T p > 4 s and at a distance from the crest edge 1 ≤ x c ≤ 5 m. Considering wave overtopping hazards, the flume bore maximum water depth and maximum velocity can exceed thresholds for pedestrian stability. • Laboratory generated dam break bores replicate overtopping of gently sloped dikes. • Results are compared to individual overtopped bore characteristics from XBeach. • XBeach extended parametric study is compared to EurOtop design guidance. • Laboratory bores replicate overtopped bores that are hazardous for pedestrians.