Burn Severity Mapping Using Simulation Modeling and Satellite Imagery

As wildfires becomes an increasingly important issue affecting our nation’s landscapes, fire managers must quickly assess possible adverse fire effects to efficiently allocate resources for rehabilitation or remediation. While burn severity maps derived from satellite imagery can provide a landscape view of relative fire impacts, fire effects simulation models can also provide spatial fire severity estimates along with the biotic context in which to interpret severity. In this project, we evaluated two methods of mapping burn severity for four wildfires in western Montana using 64 plots as field reference: 1) an image-based burn severity mapping approach using the Differenced Normalized Burn Ratio (ΔNBR), and 2) a fire effects simulation approach using the FIREHARM model. We compared the ability of these two approaches to estimate fieldmeasured fire effects and found that the image-based approach was moderately correlated to percent tree mortality (r = 0.53) but had no relationship with percent fuel consumption (r = 0.04). The FIREHARM model was moderately correlated with percent fuel consumption (0.33) and weakly correlated with percent tree mortality (r = 0.18). Burn severity maps produced by the two approaches were quite variable with map agreement ranging from 33.5% and 64.8% for the four sampled wildfires. Both approaches had the same overall map accuracies when compared to a sampled composite burn index (57.8%). Though there are limitations to both approaches, we believe these techniques could be used synergistically to improve burn severity mapping capabilities of land managers, enabling them to meet rehabilitation objectives quickly and effectively.