Measurements of Shallow Water Breaking Wave Rollers

Large scale laboratory experiments concerning breaking wave propagation over a fixed-bed, barred beach were performed. The primary observations of interest were video intensity time series obtained from a set of high-resolution video cameras in order to study the onset of wave breaking in shallow water and wave roller transformation in the surf zone. The approach is new in the sense that the analysis concentrates on individual breaking waves, as opposed to the more commonly used timeexposure technique, which averages the information over wave group time scales. A new parameter of interest is derived from the video observations based on the instantaneous intensity maximum, which propagates with the roller. The parameter is shown to provide high-resolution information regarding the onset of wave breaking and the spatial evolution of the wave roller. These observations provide a new and quite rigorous test for phaseresolving shallow water wave models.