Filling the ‘white ribbon’ in temperate Australia: A multi-approach method to map the terrestrial-marine interface

This study applies different techniques, such as single and multibeam bathymetry, sidescan sonar, terrestrial LiDAR, RTK-GPS, underwater drop camera and bathymetry derived from WorldView-2 optical imagery, to map the `white ribbon', a term first coined by the British Geological Survey which refers to the terrestrial-marine interface known for the lack of data and hydrographic challenges associated with it. The `white ribbon' area is of extreme importance for coastal managers, scientists and engineers interested in sediment dynamics, volume estimates and coastal connectivity. The `white ribbon', or the interface area formed by the intertidal and nearshore zones, is generally too shallow and dangerous for most traditional bathymetric survey vessels, due to rocks, reefs and waves, and too deep for land-based survey methods. Herein, we present the integration of data collected by multiple Australian organisations (University of Wollongong, Geoscience Australia, NSW Office of Environment and Heritage, and NSW Land and Property Information) into seamless digital elevation models for three sites (Beecroft Peninsula, Gerroa and Five Islands) on the South Coast of NSW. Two major challenges were associated with this study: the use of a small aluminium vessel to collect singlebeam bathymetry in shallow water, and the integration of the Australian Height Datum (AHD) and the Chart Datum. Research findings were particularly relevant for understanding of sediment mobility between different coastal compartments, mapping of geomorphic features, underwater extension of headlands, unconsolidated and consolidated substrates, and different rock reef habitats.