An Energy based model of storm induced shoreline erosion - Gold Coast, Australia

Quantification of storm induced shoreline erosion is an integral component of coastal zone planning. Predicting the impact of storm events on a sandy coastline is necessary for managing authorities to determine setback lines for coastal infrastructure. This paper presents the application of a cumulative storm energy model at an open coast beach located on the Gold Coast QLD. The empirical model relates shoreline position change to cumulative storm energy, which is a function of wave height and storm duration. Storm data was collected using the peak-over-threshold method, with 83 storm events being investigated between 1999 and 2008. Shoreline positions were mapped using the Northern Gold Coast coastal imaging station (Argus), and beach width changes were calculated over a 1000m alongshore section of beach. The antecedent beach states were visually characterised using multiple daily time exposure images. The results showed that for the long, straight, double-barred beach system at the Gold Coast the antecedent beach state was a strong determinant of storm induced shoreline erosion, with high energy beach states less sensitive to storm energy when compared to lower energy states. The erosion response exhibited at the Gold Coast for the modal beach state matched the upper bound of storm erosion that was determined at a NSW embayed beach, suggesting that this simple modelling approach could be applied at both embayed and open coast beaches as a practical engineering tool to perform first-pass estimates of storm induced beach erosion.6 page(s