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Title: Comparing fire severity models from post-fire and pre/post-fire differenced imagery

Author
item WEBER, KEITH - IDAHO STATE UNIVERSITY
item Seefeldt, Steven
item Moffet, Corey
item NORTON, JILL - IDAHO STATE UNIVERSITY

Submitted to: GIScience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2008
Publication Date: 2/13/2009
Citation: Weber, K.T., Seefeldt, S.S., Moffet, C.A., Norton, J. 2009. Comparing fire severity models from post-fire and pre/post-fire differenced imagery. GIScience and Remote Sensing. 45(4):1-14.

Interpretive Summary: Wildland fires are common in rangelands worldwide. A high severity rangeland fire can have long-term effects and cause vegetation changes especially in areas with exotic weed infestations. To remediate these severely burned areas it is critical to begin managing as soon as possible any areas that have been severely burned. Normally assessments of burn severity are carried out using Burned Area Emergency Response teams or similar protocols. However the size of rangeland fires and there inaccessibility make finding severely burned areas problematic. It may be possible to assist these response teams if models can be developed to find severely burned areas using remote sensing. This study compares models developed using 1) post-fire imagery only with 2) pre-fire minus post-fire imagery. The models were developed using Classification Tree Analysis (CTA) techniques and the imagery came from the Satellite Pour l'Observation de la Terre 5 (SPOT 5) and the Shuttle Radar Topography Mission (SRTM) elevation data. Our results indicate that both methods produced similar fire severity models (model agreement = 98.5%) and that little improvement in overall accuracy was gained by using pre- minus post-fire imagery (0.5 %). Therefore, we suggest the use of CTA models developed using only the post-fire imagery. The analyses and techniques described in this paper provide land managers with tools to find high severity burn areas in wildfires shortly after the fire occurs. This will improve the remediation recommendations and decisions they make following wildland fires in sagebrush steppe ecosystems.

Technical Abstract: Wildland fires are common in rangelands worldwide. The potential for high severity fires to affect long-term changes in rangelands is considerable, and for this reason assessing fire severity shortly after the fire is critical. Such assessments are typically carried out following Burned Area Emergency Response teams or similar protocols. These data can then be used by land managers to plan remediation and future land uses. To complement these procedures and explore fire severity modeling of sagebrush steppe rangelands, we compared models developed using 1) post-fire imagery only with 2) differenced imagery (pre-fire minus post-fire imagery). All models were developed from Classification Tree Analysis (CTA) techniques using Satellite Pour l'Observation de la Terre 5 (SPOT 5) imagery and Shuttle Radar Topography Mission (SRTM) elevation data. The results indicate that both techniques produced similar fire severity models (model agreement = 98.5%) and that little improvement in overall accuracy was gained by using differenced imagery (0.5 %). Therefore, we suggest the use of CTA models developed using only the post-fire imagery. The analyses and techniques described in this paper provide land managers with tools to better justify their recommendations and decisions following wildland fires in sagebrush steppe ecosystems.