Fire Severity Model Accuracy Using Short-Term, Rapid Assessment versus Long-Term, Anniversary Date Assessment

Abstract

Fires are common in rangelands, and after a century of suppression, the potential exists for fires to burn with high intensity and severity. In addition, the ability of fires to affect long-term changes in rangelands is substantial; therefore, the assessment of fire severity following a burn is critical. These assessments are typically conducted following Burned Area Emergency Response team (or similar) protocols; the resulting data can be utilized to plan future land uses and remediation efforts. For the purpose of supplementing these procedures and exploring fire severity modeling of sagebrush steppe rangelands, we compared fire severity models developed using (1) short-term post-fire imagery (i.e., imagery collected within 30 days of the fire) with (2) long-term post-fire imagery (i.e., imagery collected on or about the one-year anniversary date of the fire). The models were developed using Satellite Pour l'Observation de la Terre 5 (SPOT 5) imagery as well as Shuttle Radar Topography Mission (SRTM) elevation data, as well as Classification Tree Analysis (CTA). The results indicate that while anniversary date imagery can be used to assess fire severity (overall accuracy ~90%), it is not as accurate as short-term imagery (overall accuracy ~97%). Furthermore, use of short-term imagery allows remediation strategies to be crafted and implemented shortly after the fire. Therefore, we suggest that rangeland fire severity is best modeled using CTA with short-term imagery and field-based fire severity observations.