Mapping flood inundation in southwestern Arizona using landsat TM data: A method for rapid regional flood assessment following large storms

Landsat data can be used to detect changes at the Earth's surface caused by flooding in the deserts of the southwestern United States. On September 25-26, 1997, Hurricane Nora made landfall across Baja California Norte and then dissipated across southwestern Arizona, where it caused widespread flooding. We introduce a method of orthogonalizing bands from Landsat data, obtained before and after the passage of Hurricane Nora, in order to perform radiometric normalization simultaneously with change detection. Using multi-spectral detection allowed us to separate two general kinds of change associated with floods: vegetation growth and sediment deposition. Landsat data from southwestern Arizona were analyzed using this method to detect the extent of the flooding caused by Hurricane Nora. These data reveal that detectable changes occurred along many washes in western Arizona as a result of the passage of this storm. Comparison of remote-sensing data with independent field mapping of flood inundation on the Tiger Wash alluvial fan in western Arizona allows us to assess the general usefulness of our approach. Tiger Wash experienced an extreme flood as a result of the passage of the remains of Hurricane Nora over the region. Field investigation indicates that change detection from space is a valid and effective approach to rapidly determining where flooding has occurred in southwestern Arizona, because there is a strong correspondence between detected changes and the extent of inundated areas on Tiger Wash.