The Intertidal Extents Model (ITEM) v2.0 – Modelling the intertidal extent and topography of Australia’s coastline and reefs

Dr Stephen Sagar1, Mr Biswajit Bala1, Dr Claire Phillips1

1Geoscience Australia, Symonston, Australia


In 2016 Geoscience Australia released the Intertidal Extents Model (ITEM); derived from 28 years of earth observation data, it is the first continental scale model describing the extent and topography of Australia’s vast exposed intertidal zone. ITEM has already been used to provide information for migratory bird studies and coastal habitat mapping projects, and to derive digital elevation models that have significantly improved modelling of the land/ocean interface.

In this talk we introduce version 2 of the ITEM, based on the full archive of Landsat satellite data managed within the Digital Earth Australia (DEA) platform.  DEA provides spatially and spectrally calibrated earth observation data to enable time-series analysis on a per-pixel basis across the Australian continent. In developing ITEM v2.0 we have integrated an improved tidal modelling framework, enabling us to more accurately associate each observation in the full 30 year time series with the modelled tide height. We demonstrate the improvements this new modelling framework has provided to the ITEM product, particularly in regions with complex coastlines and large tidal ranges.

Case study examples will be discussed in which we demonstrate the new model’s ability to more effectively examine coastal instability, and to provide a smoother more continuous model across the continent. The extended coverage of ITEM v2.0 will also be introduced, including the full Great Barrier Reef, where the model provides a new perspective by identifying the extents of reefs exposed at different stages of the tidal cycle.


Stephen Sagar is the Marine Remote Sensing Project Leader within the Digital Earth Australia (DEA) program at Geoscience Australia. His research interests include the development of products from time series earth observation data, for understanding the dynamics of the coastal and marine environment.

About the Association

The Australian Coastal Society (ACS) was initiated at the Coast to Coast Conference in Tasmania in 2004. The idea was floated as a means for those interested in coastal matters to communicate between conferences and where possible take resolutions of the conference to appropriate levels of government.

The idea was discussed further at the Coast to Coast Conference in Melbourne in 2006 and it was agreed that Bruce Thom develop a constitution of a company limited by guarantee that would operate on a national basis.

This plan was accomplished and in 2008 at the Coast to Coast Conference in Darwin the constitution was ratified and an Executive appointed. The company received charitable status in 2011.

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