Abstract
This contribution presents a new procedure for the automatic identification of the individual overtopping events. The procedure is based on a zero-down-crossing analysis of the water-surface-elevation signals and, based on two threshold values, can be applied to any structure crest level, i.e. to emerged, zero-freeboard, over-washed and submerged conditions. The results of the procedure are characterized by a level of accuracy comparable to the human-supervised analysis of the wave signals. The procedure includes a second algorithm for the coupling of the overtopping events registered at two consecutive gauges. This coupling algorithm offers a series of original applications of practical relevance, a.o. the possibility to estimate the wave celerities, i.e. the velocities of propagation of the single waves, which could be used as an approximation of the flow velocity in shallow water and broken flow conditions.
Highlights
The prediction of the characteristics of the overtopping waves and their evolution over the dike crest and the identification of the individual overtopping volumes, are a key aspect in the design of coastal and harbor structures and for the estimation of their vulnerability (Van der Meer et al, 2012; EurOtop, 2016)
The identification of the single overtopping events is based on a zerodown-crossing analysis of the wave signals and on two threshold values defined that are made varying with physical parameters, such as the wave height, the structure crest emergence or submergence, the structure roughness, etc
This new procedure includes a second algorithm for the coupling of the wave signals at two consecutive gauges, to estimate the velocity of propagation of the waves and to capturing the evolution of the wave shape and parameters for an enhanced characterization of the overtopping process
Summary
The prediction of the characteristics of the overtopping waves and their evolution over the dike crest and the identification of the individual overtopping volumes, are a key aspect in the design of coastal and harbor structures and for the estimation of their vulnerability (Van der Meer et al, 2012; EurOtop, 2016). The identification of the single overtopping events is based on a zerodown-crossing analysis of the wave signals and on two threshold values defined that are made varying with physical parameters, such as the wave height, the structure crest emergence or submergence, the structure roughness, etc This new procedure includes a second algorithm for the coupling of the wave signals at two consecutive gauges, to estimate the velocity of propagation of the waves (celerity) and to capturing the evolution of the wave shape and parameters for an enhanced characterization of the overtopping process. The upper threshold uth is set greater than a certain percentage of lth and it is introduced in the algorithm to ensure a correct identification of the events in case of very “irregular” or “noisy” wave signal, as in the example of Figure .3 This kind of signals typically occur over the crest of structures rarely overtopped, where the friction and/or the complete or partial wave breaking induce bursts of small amplitude and almost instantaneous duration in the sea surface elevation signal. In this case the wave identification and the wave coupling are eased by the regularity of the signals, and only one identified at wg and uncoupled is discarded (event around 33 s marked with a black cross)
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