Dr Robbi Bishop-Taylor1, Dr Rachel Nanson1, Dr Stephen Sagar1, Dr Leo Lymburner1
1Geoscience Australia, Canberra, Australia
Accurate, robust and consistent coastline mapping is critical for characterising and managing the impacts of coastal change. Satellite remote sensing provides an unparalleled source of freely available data for studying dynamic coastlines through time and across large extents. However, previous approaches have been challenged by the low spatial resolution of freely available satellite data, and the influence of tides that can obscure long-term patterns of coastal change. Here we present DEA Coastlines, a new continental dataset providing consistent tide-datum coastlines and robust rates of coastal change. We combine subpixel waterline extraction with tidal modelling to map median annual coastline positions at 0m Above Mean Sea Level along the entire Australian coastline from 1988-2019. We validate our method using extensive in-situ coastal monitoring datasets covering diverse coastal environments and survey methodologies. Bias-corrected coastline mapping was precise to 11.4m over sandy substrates, with highest accuracies along steeper coastlines and against in-situ datasets with high sampling frequencies. 33% of Australia’s clastic coastlines have retreated or prograded significantly since 1988, with 16% changing at greater than 0.5 m/year. Coastal change in Australia was predominantly recessional, however hotspots of extreme coastal growth and retreat were identified nationally. Our results provide new insights into patterns and trends of coastal change across Australia, and highlight the critical value of long term in-situ coastal monitoring data for evaluating satellite-derived coastal datasets. DEA Coastlines is made available to scientists, coastal managers and policy makers as free and open interactive tools and code to support future coastal research and management.
Robbi Bishop-Taylor is a Coastal Earth Observation Scientist from Geoscience Australia, specialising in the use of satellite remote sensing to map and monitor coastal change along the entire Australian coastline.