Comparison of two wave models for Gold Coast, Australia

Abstract

Managing hazards associated with shoreline responses to extreme events and the provision of safe boating access is an ongoing concern for coastal authorities. The open sandy coastline of Gold Coast city is a wave dominated coast with a highly variable wave climate and a narrow continental shelf thus experiencing substantial variations in long-shore transport rates. Detailed wave transformation information is central to further investigations of sediment transport processes as complex bathymetry associated with trained river entrances and rocky headlands causes localised interruptions to the overall northward littoral drift. Temporal variations in wave energy are driven by a wide range of swell direction and size while spatial variations occur as a result of the strong refraction during particular swell events. This paper presents a comparison of two near shore wave models of the region using MIKE 21 and SWAN. The transformation of waves arriving from offshore is simulated using the models for selected time series of wave parameters. The parameterized boundary conditions are derived from NOAA Wave Watch III global wave model data. Model output is compared with observed data from existing wave recording buoys at Gold Coast Seaway and Point Lookout. The inclusion of wind in the modelling undertaken did not improve the models' accuracy and winds in excess of 10 ms-1 led to an over-estimation of significant wave height while increasing the processing time. Sheltering of the near-shore site during southerly swell conditions was well-represented by the modelling.