Nearshore Wave Simulations and Wave Characteristics Analysis during Extreme Weather Events

Abstract

Offshore storm wave direction may distinguish between an extreme event and a typical event experienced at nearshore. Using a state-of-the-art spectral wave (SW) model, the purposes of this study are: (1) to investigate the transformation of waves from offshore to nearshore along the coastline from two opposite directions (northerly and southerly); and (2) to analyse the offshore wave energy density spectrum. The SW model was calibrated considering various mesh resolutions and lateral wind forcing with different wind field resolutions. The results show that a longshore wave attenuation gradient exists from the southerly swell, primarily due to different degrees of sheltering provided by the headland. In contrast, the coast essentially becomes an open coast from northerly swells, thereby producing a significant reduction in wave attenuation. The wave energy density spectrum indicates that wave pattern varies depending on offshore wave direction. Both storms produce a wide range of frequencies and directions. However, southerly swells only produce single-peaked spectrum, while double-peaked spectrum is observed in northerly swells due to the presence of prevailing swells and storm swells. This study highlights the significant reduction of wave attenuation when predominate offshore wave direction is abrupted.