Dr Stephen Sagar1, Dr Leo Lymburner1, Dr Claire Phillips1, Mr Biswajit Bala1, Dr Dale Robert1
1Geoscience Australia, Symonston, Australia
Intertidal zones are dynamic, unique and extreme environments due to the combined effects of the tide, exposure and weather. As a result, the ecosystems they host are dynamic and unique, ranging from migratory bird habitat to larval fish nurseries and mangrove wetlands. For the essential functions that these environments offer, they cover an extremely small area of continental landmass. Furthermore, these environments are notoriously difficult to survey and clearly characterise using remote sensing, mainly due to the varying coverage of water throughout the tidal cycle.
High and low tide image geomedian composites of the Australian coastline have been produced from the Landsat imagery archive, stored and managed within the Digital Earth Australia (DEA). Modelled tide heights were attributed to all coastal images in the archive, enabling the generation of composite images from archival subsets, based on Landsat images acquired between 2000 and 2017 and sorted into the upper or lower 20 percent of the observed tide range.
The result is two highly detailed, clear and cloud free composite images of the Australian coastline, at a resolution of 25 m2 for both high and low tide and which will be freely accessible online. This tidally tagged archive of satellite imagery can be further used to investigate coastal and event based change by varying the temporal domain and restricting tide-based variability in the subsets used for composite generation.