EVIDENCE OF TOPOGRAPHIC STEERING OF WINDS IN A SMALL, COASTAL BLOWOUT, SOUTHEAST QUEENSLAND – APPLICATIONS OF GPR AND PALAEOCLIMATE

Great Sandy National Park is located in coastal southeast Queensland, Australia. The area is home to the world’s largest sand island, Fraser Island, and large mainland sand masses. The massive, complex dune fields are presently stabilized by vegetation. However, previous work suggests that the dune field has had periods of activity and dune building over the past million years when the entire region was active with respect to aeolian processes.

Various sizes and forms of blowout structures provide areas of active aeolian processes within the stabilized dune fields. On the Cooloola Sand Mass, two coastal, cliff-top blowouts exist. The Little Blow is at the northern terminus of the large, stabilized aeolian dune field and in close proximity to the town of Rainbow Beach. The northwest migration of the blowout crest is threatening town infrastructure and private property with burial.

A detailed ground penetrating radar and remote sensing campaign was mounted to understand how the blowout has evolved over time and establish the degree of threat to the town. The results show present migrations rates of ~1 m/yr to the northwest. However, GPR imagery of the subsurface architecture indicates that potential wind direction has changed significantly over time. Orientation of reflections related the depositonal lobe slipfaces suggest that the wind direction has changed from north to north-northwest to northwest. Correlation with climate records from the area as well as examination of other features throughout the Cooloola Sand Mass and adjacent Fraser Island do not indicate a similar shift in wind direction. As the deposional lobe is as the northern terminus of the field, we attribute the observed change in the depositonal lobe as an influence of local conditions on the wind field, primarily through topographic steering.