PARAMETRIZATION OF ORBITAL VELOCITY ASYMMETRIES OF SHOALING AND BREAKING WAVES USING BISPECTRAL ANALYSIS

A bispectral analysis of electromagnetic flow meter data collected from four nearshore environments was undertaken to investigate the spatial variation of velocity skewness and asymmetry for shoaling and breaking surface gravity waves. The data base provides a wide range of wave conditions and beach characteristics (including planar and barred beaches). A simple parametrization for bispectral evolution (amplitude and phase) due to wave shoaling, which is based on the Ursell parameter, is proposed and tested. The results show that the parametrization provides both a good qualitative and reasonably quantitative prediction of velocity skewness and asymmetry arising from phase-coupling between wind-wave frequencies. Infragravity wave velocity skewness and asymmetry are also examined.