Assessing long-term changes in shoreline position using multi-decadal remote sensing datasets in Queensland (Australia)

Dylan Cowley1, Dr Daniel Harris1

1School of Earth and Environmental Sciences, The University Of Queensland, Brisbane, Queensland

Abstract:

Sandy beaches are subject to a wide variety of processes that influence shoreline position and coastal orientation. The northeastern coast of Australia provides a unique setting to investigate shoreline change in environments that are exposed to a range of different climate and oceanographic processes. An extensive, yet underutilised, record of historical aerial photography (HAP) provides an excellent opportunity to investigate geomorphological development of this region over a multi-decadal scale. Here, we present a study of coastal change for a selection of beaches in Queensland, Australia, over a period of up to 90 years using high resolution (0.5-5m) aerial photographs. These images were orthorectified, and shoreline features were digitised to extract shoreline change statistics. Change rates and net movement were calculated, as were the confidence limits for observed shoreline adjustments. In addition to natural beach variability associated with sub-decadal adjustments to forcing conditions, there is a trend of accretion over the entire HAP record for most locations. Most sites present a long-term pattern of beach rotation on varying temporal scales in a consistent direction, with accretion (erosion) occurring on the northern (southern) sections of each beach. These observed changes may be a result of long-term adjustments in the offshore wave climate or sediment dynamics on the coast, though further work is to be completed to rigorously define the driving forces for these observations. This study provides insights into a variety of coastal settings and allows for further investigation into the mechanisms that control beach change over management oriented time scales.


Biography:

I am a third year PhD candidate at the University of Queensland, studying the role of waves and large scale ocean-atmosphere variations (such as ENSO) in the modification of coastal landforms, with a focus on sandy beaches on the Queensland coast.

I’m using a data driven approach to identify coastal change and the forcing mechanisms that may help explain the observed variability.