Echoes Of Fire: Geospatial Analysis of Terrain, Legacy Burns, and Wind-Aligned Severity During The 2025 Forsyth Fire, Pine Valley, Utah
Presentation Time: Fri, 12/05/2025 - 15:30
Keywords: Wildfire Severity; Terrain Analysis; Remote Sensing; Wind Alignment; Legacy Burns
This study examined how topography, vegetation moisture, and legacy fire perimeters influenced burn severity and directional spread during the 2025 Forsyth Fire in Pine Valley, Utah. The analysis integrated remote sensing, topographic, and meteorological data within ArcGIS Pro 3.5.4 to assess spatial factors affecting fire behavior. Differenced and relativized Normalized Burn Ratio (dNBR, RdNBR) indices derived from pre- and post-fire Landsat 8 OLI composites were used to map burn severity. In contrast, Normalized Difference Vegetation and Moisture Indices (NDVI, NDMI) evaluated pre-fire fuel conditions and post-fire canopy moisture changes. Topographic derivatives from the 10 m National Elevation Dataset—slope, aspect, and elevation—were summarized using zonal statistics. Mean burn severity increased from reburn to control zones, with dNBR values ranging from 88 to 174. Steeper slopes (20.18 ± 0.95°) and south-facing aspects (southness = –0.14 ± 0.08) correlated with higher dNBR (r = 0.57) and greater moisture loss (r = –0.69), confirming the influence of solar exposure and terrain inclination. Wind-alignment analysis showed that about 70 percent of the perimeter expansion occurred within 30° of the dominant southwest-to-northeast wind direction (mean azimuth = 41.1° ENE), linking burn severity to directional spread. Overall, the Forsyth Fire demonstrated increased intensity along steep, south-facing ridges intersecting the 2016 Saddle Fire scar, suggesting residual fuels and terrain features amplified severity toward the Pine Valley community. The findings highlight that integrated geospatial modeling effectively captures terrain-wind-fuel interactions that influence wildfire behavior.
