Figure 3a. False-color composite of ASTER bands 2, 3, 1 in red, green, blue, respectively. This color representation highlights the presence of the fire scars, showing the low values of active vegetation (green) and an overall higher albedo than the non-burned areas. The diffuse purple color indicates high reflectance values in the ASTER visible bands 1 and 2 and low in the near infrared (band 3). This spectral response is common for visually bright desert soils with little vegetative cover.

Figure 3b. (below) ASTER band 2 (15m spatial resolution) gray scale image overlain by vector polygons showing the detectable fire scars in the northeast Phoenix valley. This ASTER scene was acquired on September 19, 2000 and has only been processed to Level 1A (no geometric/radiometric calibration has been applied). Each of these scars were formed by human or naturally-caused brush fires over the past 25 years, with the most recent and largest being the "Rio Fire" of 1995. That fire burned more than 58 km and threatened homes in several new housing developments. Fire scars denude the landscape and may enhance surface flow during the summer monsoon rain season. This increase in water run-off promotes erosion, down-channel deposition and flash flooding hazards. Currently, this region of the Phoenix valley is undergoing some of the most rapid urban development in the country, and hence is a prime pilot site for this study.