Influence of Spectral Width on Wave Height Parameter Estimates in Coastal Environments

Abstract

In this study, we present comparisons of wave height estimates using data from acoustic Doppler wave gauges in ten coastal and estuarine environments. The results confirm that the agreement between significant wave height estimates based on spectral moments (Hm0) versus zero-crossing analysis (H1∕3) is linked to the underlying narrow band assumption, and that a divergence from theory occurs as spectral width increases with changes in the wave field. Long-term measurements of the maximum to significant wave height ratio, Hmax∕H1∕3, show a predictable dependence on the site-specific wave climate and sampling scheme. As an engineering tool for other investigators, we present empirically derived equations relating Hm0∕H1∕3 and H1∕3∕m0 to the spectral bandwidth parameter, ν, and evaluate two procedures to predict Hmax from the spectrum when the surface elevation time series is unavailable. Comparisons with observations at each site demonstrate the utility of the methods to predict Hmax within 10% on average.