A Triple La Nina & SEQ Coastal Changes: Implications for Management
Lecture, April 2023
By Dr Javier Leon

The capacity of sandy beaches to provide coastal protection varies across time and space. Recent research suggests climate change could result in substantial erosion of most sandy beaches by the end of the century, with significant social and economic impacts. Furthermore, storm and cyclone events generate extreme erosion of sandy beaches which is not fully recovered. Three back-to-back La Nina events occurred between 2020-2023. La Niña is associated with warmer waters in the western Pacific Ocean, which increase storminess off Australia’s east coast. Chances of a higher number of tropical cyclones increase, as do the chances of cyclones travelling further south and further inland, and of more frequent passages of east coast lows. Detailed (3 cm spatial resolution) and frequent (monthly or bimonthly) drone and ground-based volumetric surveys were undertaken during this period along the open beaches between Peregian Beach and Sunshine Beach with the aim of monitoring coastal change along the shoreline and dunes. Results are variable and indicate average shoreline erosion of around 20 m, dune crest retreat of up to 10 m and dune erosion of up to 3 m vertically on some locations. Frequent, high-quality 4D spatial information (3D plus time) across the coastal zone is required to monitor, manage and predict coastal change and its associated hazards. Building an understanding of coastal response to both gradual and extreme events is especially critical in an era of progressively rising sea levels which are likely to exacerbate already existing trends.