Use of Multitemporal ERS-2 SAR Images for Identification of Burned Scars in South-East Asian Tropical Rainforest

Florian Siegert* and Gernot Ruecker+

*Ludwig-Maximilians-University, Luisenstr. 14, 80333 Muenchen

+ZEBRIS GbR Geographic Information Systems and Consulting, Lipowskystr. 26, 81373 Muenchen

The evaluation of a multitemporal series of ERS-2 Synthetic Aperture Radar (SAR) images of an area severely affected by fires in 1998 showed that fire induced changes in surface properties strongly affect C-Band radar backscatter. We investigated the changes in radar backscatter over a period of ten months in areas of interest representing different land-cover types at a study site in East Kalimantan, Indonesia. Fire impact was found to cause a strong decrease in backscatter (2-5 dB) in all land-cover classes while areas not affected by fire show only a slight decrease in backscatter (0.5-1 dB) probably due to drought effects. Ground and aerial evidence suggest that the marked decrease in backscatter can be attributed to the removal of the vegetation cover and subsequently higher contribution of backscatter from dry soil. After the onset of rain the radar reflectivity increased (3-5.5 dB) in areas severely affected by fire while in unburned forests it resumed to similar values as before the drought. PCA-enhanced colour composites for change detection between two successive images were found to be a useful tool for visual identification of burned scars.