DEA Intertidal Extents (Landsat) ================================ Intertidal Extents Model 25m 2.0.0 ----------------------------------- **Authored on**: 2018-03 **Updated on**: 2022-08 **Author/s**: Stephen Sagar, Biswajit Bala **License**: CC BY Attribution 4.0 International License View the [original metadata page](https://cmi.ga.gov.au/data-products/dea/174/dea-intertidal-extents-landsat) for the most up-to-date information on this product. Abstract -------- Intertidal zones are those which are exposed to the air at low tide and underwater at high tide. These include sandy beaches, tidal flats, rocky shores and reefs. Intertidal zones form critical habitats for a wide range of organisms, but are faced with increasing threats, including coastal erosion and a rise in sea levels. Accurate knowledge of the extent and topography of these regions can help assess where these threats will have the greatest impact, and provide essential information to underpin monitoring and management strategies. This data is challenging to acquire using traditional survey methods given the dynamic nature of intertidal zones and length of the Australian coastline. What this product offers ------------------------ This product is a national dataset of the exposed intertidal zone: the land between the observed highest and lowest tide. It provides the extent and topography of the intertidal zone of Australia's coastline (excluding off-shore Territories). This information was collated using observations in the Landsat archive since 1986. This product can be a valuable complementary dataset to both onshore LiDAR survey data and coarser offshore bathymetry data, enabling a more realistic representation of the land and ocean interface. Applications ------------ - Understanding the extent and topography of the Australian intertidal zone - Environmental monitoring of migratory bird species - Habitat mapping in coastal regions - Hydrodynamic modelling - Geomorphology studies of features in the intertidal zone Accuracy and limitations ------------------------ Due the sun-synchronous nature of the various Landsat sensor observations; it is unlikely that the full physical extents of the tidal range in any cell will be observed. Hence, terminology has been adopted for the product to reflect the highest modelled tide observed in a given cell (HOT) and the lowest modelled tide observed (LOT) (Figure 2). These measures are relative to Mean Sea Level, and have no consistent relationship to Lowest (LAT) and Highest Astronomical Tide (HAT). The inclusion of the lowest (LMT) and highest (HMT) modelled tide values for each tidal polygon in the ITEMv2\_tidalmodel dataset indicates the highest and lowest tides modelled for that location across the full time series by the OTPS model. The relative difference between the LOT and LMT (and HOT and HMT) heights gives an indication of the extent of the tidal range represented in the Relative Extents Model. As in ITEM v1.0, v2.0 contains some false positive land detection in open ocean regions. These are a function of the lack of data at the extremes of the observed tidal range, and features like glint and undetected cloud in these data poor regions/intervals. Methods to isolate and remove these features are in development for future versions. Issues in the DEA archive and data noise in the Esperance, WA region off Cape Le Grande and Cape Arid (Polygons 236,201,301) has resulted in significant artefacts in the model, and use of the model in this area is not recommended. Publications ------------ Sagar, S., Roberts, D., Bala, B., & Lymburner, L. (2017). Extracting the intertidal extent and topography of the Australian coastline from a 28 year time series of Landsat observations. *Remote Sensing of Environment*, *195*, 153–169. [https://doi.org/10.1016/j.rse.2017.04.009 ](https://doi.org/10.1016/j.rse.2017.04.009) References ---------- Sagar, S., Roberts, D., Bala, B., & Lymburner, L. (2017). Extracting the intertidal extent and topography of the Australian coastline from a 28 year time series of Landsat observations. *Remote Sensing of Environment*, *195*, 153–169. [https://doi.org/10.1016/j.rse.2017.04.009 ](https://doi.org/10.1016/j.rse.2017.04.009) Sagar, S., Phillips, C., Bala, B., Roberts, D., & Lymburner, L. (2018). Generating continental scale pixel-based surface reflectance composites in coastal regions with the use of a multi-resolution tidal model. *Remote Sensing*, *10*(3), 480. Contacts -------- For questions or more information about this product, email [DEA Support](mailto:dea@ga.gov.au?subject=Data%20Products%20support%20for%20DEA%20Intertidal%20Extents%20%28Landsat%29&cc=earthobservation@ga.gov.au).