Wave statistics and spectral shape in the nearshore region

Human interaction with ocean surface waves occurs mainly in the nearshore region. Waves propagating towards the coast over gradually sloping bathymetry undergo fundamental transformations, resulting in statistics and spectral energy distributions that are substantially different to those of the incoming wave field in deep water. This is of particular importance to the generation of individual extreme waves.

This presentation will address our recent observational studies of spectral wave properties and surface elevation statistics at various nearshore locations ranging from normalized water depth of kH > 5 (deep water) to kH < 0.1 (beach-water interface). Data were obtained by surface following wave buoys, bottom-mounted pressure sensors, and an acoustic current profiler. The data reveal the dependence of skewness, kurtosis, and wave groupiness on normalized water depth, and on the position within the surf zone relative to the onset of depth-induced breaking. In the surf zone, skewness and groupiness are modulated coherently, whereas modulations of the kurtosis seem to be more random. In addition, the spectral change of the wave energy across the surf zone including the emerging infragravity wave signal will be discussed.