AusGeo News  June 2011  Issue No. 102

Satellite imagery assists flood emergency response and recovery

David Hudson and Norman Mueller

International support for Geoscience Australia's contribution

Heavy rainfall occurred across most of Australia between November 2010 and early February 2011 causing extreme flooding across eastern Australia, particularly in Queensland and Victoria. During the flood emergencies, Geoscience Australia provided satellite imagery and derived mapping information to support the emergency response and recovery efforts. These images came from more than twenty different satellites operated by governments and companies from the United States, United Kingdom, Germany, Japan, Italy, France, Canada, Taiwan and the European Commission.

Table 1.Detailed breakdown of each of the acquired datasets and their source.

Satellite sensor Type Acquisition window Scenes acquired Resolution (m) Acquisition method Country of origin
Cosmo-SkyMed RADAR 12.01.2011–13.01.2011 2 3 OGRE Italy
RADARSAT-2 RADAR 06.01.2011–12.01.2011 4 10 Charter Canada
TerraSAR-X RADAR 04.01.2011–18.01.2011 9 10 Charter Germany
ALOS, PALSAR RADAR 04.01.2011–16.01.2011 6 10–30 Charter Japan
ENVISAT, ASAR RADAR 05.01.2011–17.01.2011 2 150 Charter European Commisiion
Formosat 2, RSI Optical 06.01.2011–10.01.2011 2 2–8 Charter Taiwan
Spot4/5 Optical 07.01.2011–09.01.2011 11 20–10 Charter France
ASTER Optical 05.01.2011–17.01.2011 12 15 Charter Japan
DMCii Optical 09.01.2011–20.01.2011 6 22 Charter UK
Quickbird Optical 19.12.2003–22.11.2006 23 2.4 Charter US
Worldview 1 Optical 13.01.2008–16.01.2011 331 0.5 Charter US
Avnir2 Optical 16.01.2011 4 10 Charter Japan
Terra, MODIS Optical 05.12.2011–19.01.2011 10 250 GA ground station US
Aqua, MODIS Optical 12.12.2010–18.01.2011 6 250 GA ground station US
MODIS Composite Optical 19.10.2010–14.01.2011 103 500 GA ground station US
Landsat 5, TM Optical 05.12.2010–20.01.2011 53 25 GA ground station US
Landsat 7, ETM+ Optical 13.12.201–19.01.2011 25 25 GA ground station US
Total
609

Between December 2010 and February 2011, Geoscience Australia acquired more than 600 satellite images covering flood-affected areas from satellite imagery archives around the world, satellite downlink stations in Australia, international space agencies and overseas commercial imaging satellite operators (Table 1). The three key sources of these satellite images were:

Fig 1. Landsat 5 true-colour images of Brisbane before and after the January floods. The image on the left was acquired on 19 October 2010 and shows the typical conditions around Brisbane before the floods. Urban areas appear light grey while vegetation appears green and dry areas such as farmlands appear brownish. The image on the right was acquired on 17 January 2011 and shows the conditions as flood waters receded. The flood waters appear as dirty brown while clear water is dark blue.
  1. Day-to-day satellite imagery acquisition from downlink stations in Alice Springs and Hobart.
  2. Activation of the International Charter for Space and Major Disasters. The International Charter is an agreement involving 39 countries to provide satellite data during a major disaster.
  3. The cooperative panel for Optical Geospatial Radar and Elevation (OGRE) data and services. This panel is a government procurement mechanism for accessing imagery-related data and services. The panel was established in 2010 in a joint project by Geoscience Australia and the Defence Imagery and Geospatial Organisation (DIGO).

Figure 1. Landsat 5 true-colour images of Brisbane before and after the January floods. The image on the left was acquired on 19 October 2010 and shows the typical conditions around Brisbane before the floods. Urban areas appear light grey while vegetation appears green and dry areas such as farmlands appear brownish. The image on the right was acquired on 17 January 2011 and shows the conditions as flood waters receded. The flood waters appear as dirty brown while clear water is dark blue. Sediment plumes from the flooding rivers can be seen streaming out into Morton Bay from the Brisbane River. Many of the areas that appear dry (brownish) in the pre-flood image are now showing green as grasses react to the wet conditions. The cloud in this image appears grey to white.

The emergency support included the provision of satellite imagery, flood extent data and flood maps showing flood-affected areas and their surrounds. These images allowed emergency managers to carefully monitor the extent of the flooding and receding waters. Imaging satellites capture a specific point in time and so it is extremely difficult to capture the peak of a flood. In addition, many of the images are obstructed by clouds as the majority of satellites are optical satellites and cannot see through the clouds which are highly likely over a flooding area (figure 1).

Utilisation of the satellite imagery

Fig 2.  Map showing flood footprint coverage in southeast Queensland derived from the Landsat 5 satellite.

During the flood crises, Geoscience Australia was able to provide over 75 maps and 25 flood extent products based on the data received by emergency service agencies across Australia (figure 2). These products were used for many applications including emergency response deployment, early impact assessment, guiding Natural Disaster Relief and Recovery Arrangements (NDRRA) payments, assisting the Bureau of Meteorology with data used for flood warnings where ground instruments had been damaged, briefings and redeployment of government services such as child care facilities.

The response to the Queensland floods took the utilisation of satellite imagery to a new level for Australia and demonstrated the critical role remote sensing services have in emergency management.

Figure 2. Map showing flood footprint coverage in southeast Queensland derived from the Landsat 5 satellite.

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