Detailed Assessment of Extreme Coastal Erosion and Storm Surge Vulnerability of Central Gold Coast Beaches

Abstract

The Gold Coast's beaches have achieved iconic status worldwide with residents nearing 40 million trips to the foreshore annually and tourists an additional 7 million. The littoral environment is described as high-energy open coast, regularly subjected to storms and large waves (Hmax of 14 m, 2004) with a net annual sediment transport rate of approximately 500,000 m3. This system is found to be in long-term equilibrium with the major impact coming from the cross-shore movement of sand during large events such as cyclone, where large seas and storm surge prevail. Urban development has seen the beaches, creeks and river entrances of the coast modified to provide the necessary coastal protection, community, economic and environmental services to sustain the city. In 2005, Gold Coast City Council (GCCC) commenced a Shoreline Management Plan (GCSMP) to review the social, environmental and economic processes that impact the way the city's beaches are managed. The major outcome of the review is the development of a new shoreline management plan to guide coastal works for the next 50 years. DHI Water and Environment were commissioned to implement a high resolution numerical model to provide outputs for possible control systems or structure design in the vicinity of Palm Beach - the least resilient of the Central Gold Coast Beaches. Recent beach and creek profile surveys and the near-shore wave data were collected for calibration and verification of the numerical models. Scenario testing was carried out using the damaging East Coast Low for the period March to May 2009 which was of great significance to the region. Such high level detailed modelling is required to encompass the complex two dimensional nature of sediment transport in this region. This study is a vital part of an integrated Decision Support System to guide ongoing foreshore protection and nourishment of the Gold Coast beaches.