MODELLING WAVE INTERFERENCE PATTERNS USING THE SWAN MODEL

Abstract

This study presents an efficient approach of resolving wave interference patterns in spectral wave models (e.g., SWAN). Such interference patterns, which frequently occur in coastal waters (e.g., near headlands, harbor entrances and coastal inlets), may lead to rapid changes in wave statistics, and thus, can affect wave-driven flow and transport processes. Therefore, prediction of wave conditions for coastal applications should account for these effects. Presently, operational wave models compute the mean wave properties by solving the action balance equation, which describes the transport of wave energy through geographic and spectral space, augmented with source terms to account for non-conservative and nonlinear processes. This model equation, initially intended for deep water conditions, is derived under the assumption that waves propagating at angles are mutually independent so that the wave field changes its mean properties (e.g. wave height) over many wavelengths. However in nearshore areas, the interaction of waves with variable bathymetry and currents can result in interference zones where crossing wave trains are statistically correlated and wave heights change rapidly.