Geoscience Australia produces national flood frequency maps

source: Geoscience Australia

Water Observations from Space (WOfS) is a web service displaying historical surface water observations derived from satellite imagery for all of Australia for the period of 1998 to 2012. By June 2015 this service will be extended to enable users to view data on surface water observed by satellite across Australia since 1987. WOfS displays the detected surface water from the Australia-wide Landsat-5 and Landsat-7 satellite imagery archive. The aim of WOfS is to better understand where water is usually present; where it is seldom observed; and where inundation of the surface has been occasionally observed by satellite.

In the first phase of this project, delivered in November 2012, the service showed a proof of concept of how satellites can be used to detect surface water across Australia for specific periods between 2000 and 2012. Following further development, the new version of this service – which is still being reviewed and tested – now shows surface water observed by the Landsat-5 and Landsat-7 satellites for all of Australia from 1998 to 2012.

Water is detected from the satellite images using an automated flood mapping algorithm created by Geoscience Australia. The water detected for each location is summed through time and then compared to the number of clear observations of that location (i.e. observations not affected by cloud, shadow or other quality issues). The result is a percentage value of the number of times water was observed at the location. This provides relatively seamless historical water coverage for Australia, as observed by satellite. The colouring of the summary layer indicates how often water was observed in each cell of a 25 metre by 25 metre grid across Australia. 

For further details, see the Water Observations from Space web site

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