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UAVSAR and Optical Analysis of the Thomas Fire Scar and Montecito Debris Flows:...

Donnellan, A., J. Parker, C. Milliner, T. G. Farr, M. Glasscoe, Y. Lou, et al. (2018), UAVSAR and Optical Analysis of the Thomas Fire Scar and Montecito Debris Flows: Case Study of Methods for Disaster Response Using Remote Sensing Products, Earth and Space Science, 5, doi:10.1029/2018EA000398.

We use the 2017 Thomas fire and ensuing Montecito debris flow as a case study to demonstrate how application of various interferometric synthetic aperture radar postprocessing techniques can be used to highlight the fire scar and major damage areas from the debris flows. We use National Aeronautics and Space Administration’s airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) L-band polarimetric interferometric synthetic aperture radar (InSAR) for this study. Results demonstrate that a single polarimetric radar image highlights burn areas. Coherence and interferometric radar pairs show the fire scar and debris flow. An unwrapped interferogram shows the location of the debris flow over the 101 Freeway in greater detail than a raw interferogram. We enhanced the interferogram and coherence product of a pair of images acquired before and after the fire and debris flows, which highlights areas of destroyed structures and major damage. We first despeckled the images and then converted the interferogram to four colors and the coherence map to two colors. Analysis of optical imagery between before and after images shows that the debris flows are best identified using visible bands and that near-infrared better highlights the lower part of the flows where more mud was deposited. These simplified products provide more actionable products for disaster responders; the products were downloaded for use by the State of California. Plain Language Summary Airborne radar imagery from National Aeronautics and Space Administration’s Airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar platform spanning the 2017 Thomas fire scar and subsequent 2018 debris flows highlights the location of the fire scar and debris flows when processed in different ways. The results highlighting the debris flows correspond with areas of major damage and destroyed structures. Optical image data from Planet Labs Dove satellite show that visible bands differenced before and after highlight the upper part of the debris flows, while near-IR shows the lower muddier part of the flows.

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