Modelling of flood patterns, using remote sensing, in the Coongie Lakes Wetlands, northeastern South Australia

© 1998 Justin Francis CostelloeThe Coongie Lakes is an area of freshwater wetlands located in the Strzelecki desert of north-eastern South Australia. The annual flood pulse from the unregulated Cooper Creek is the principal supply of water to this area of wetlands and of fundamental importance to the ecosystems of the wetlands. Understanding the hydrological factors that affect the flood patterns in arid zone wetlands is vital in the study of the ecology of the wetlands and when assessing the likely ecological effects of any upstream diversion of water from dry land rivers, such as Cooper Creek. The variability of the flood regime of dryland rivers requires that the flooding patterns from a range of flood pulses, with widely differing characteristics, be examined in order to best understand the subtle and complex interactions that are occurring. The use of the AVHRR, data provides the only viable synoptic and temporal coverage that can map the floodwater patterns during current and recent historic, large-scale flood events. The spatial and temporal distribution of floodwaters in the Coongie Lakes was mapped, using NOAA-AVHRR satellite imagery, for the period 1988-1990. Variations between images, not associated with the inherent albedo of the surface, were minimised by applying coefficients to the satellite data that corrected for the different path length of each image. These were measured for the centre of the image and this also minimised in-scene variations due to the wide view angle of the AVHRR. The images were not corrected for changes in atmospheric conditions between the different scenes. The effects of increased atmospheric haze levels and/or highly off-nadir view angles on some images was found to be quite significant and compromised the utility of the affected images in mapping out the distribution and movement of floodwaters. The floodwaters in the wetlands were identified using the ratio of NIR/Red