Using radar to detect flooding in arid wetlands and rivers

The arid zone of Australia is an environment with `boom and bust´ dynamics; where years of drought can be followed by periodic flash flooding. Major floods occurred along 500km of the Paroo River in March 2010 at levels unequaled since 2000. Dual polarization (HH/HV) L-Band synthetic aperture radar (SAR) data was obtained from the Japanese Advanced Land Observing Satellite (ALOS) to evaluate its use for mapping flooding over an area of high conservation value floodplain wetlands. The data were shown to be highly informative for mapping flooded classes and provide an alternative data source to optical imagery in the presence of cloud cover. Due to radar speckle, segmentation was used to partition the scenes within eCognition Developer. Classification was performed on image objects using decision rules based on field verified radar backscatter thresholds of classes and change detection. The methods developed for single and multiple images provide a framework for operational mapping and monitoring water over time, as well as a rapid response strategy for flood emergencies. Future work on image transforms and research on the interoperability of SAR and optical data will aim to improve differentiation of wetland classes.