Tempest to Tranquillity: Remotely Sensing the Impact and Recovery of Storms on the Beaches of SE Australia

Abstract:

Climate change induced sea-level rise will result in storm erosion becoming the primary driver of long-term coastal recession. Australia is particularly vulnerable, as 80% of the population lives near the coast (most concentrated in the southeast). Recent storm events in 2013 and 2016 resulted in extensive erosion and property damage in New South Wales (NSW) but pales in comparison to the severe impact of a series of high-energy events in the 1970s. Long-term beach profiles exist only at Narrabeen and Moruya beaches and of these >40-year datasets, only one captures data prior to the 1970s. Photogrammetry using aerial photographs dating back to the 1970s as well as Light Detection and Ranging (LiDAR) data collected during 2013 provides an opportunity to extend spatial and temporal knowledge of barrier morphodynamics. The study sites, Wollongong South, Shellharbour South, Bulli (Sandon), Moruya (Bengello) and Callala, were chosen to cover a range of beach-barrier and embayment types, also considering the availability of historical data. The aim of this project was to investigate the primary coastal processes that influence beach storm-response, and the ways in which we can monitor coastal change. This project circumvents the lack of high-resolution, historical data by assessing the impact of storm events on sandy beaches along the NSW coast using remote sensing and geographical information systems (GIS). This analysis has revealed information about the impacts of the 1970s storms on NSW’s beaches; however, errors and limitations associated with this remote sensing method mean that the results are not sufficiently accurate enough to draw definitive conclusions without the use of additionally remotely sensed information, such as that derived from ground penetrating radar (GPR). It has been suggested that the erosive potential of NSW’s current definitive design 1-in-100 year storm event may be a substantial underestimate; the outcome may be an increase in risk to human life and coastal infrastructure during the next storm of this magnitude. This project has uncovered some of the mystery behind the impacts of the devastating series of storms in the 1970s and highlights the unreliable nature of depending solely on historical records for projecting future coastal change.