BC Wildfire PSTA Spotting Impact

Provincial Strategic Threat Analysis (PSTA) is designed to consistently assess and map potential wildfire threats to values across the landscape (including communities, infrastructure and natural resources) and to integrate different aspects of wildfire hazard and risk.

Spotting was modeled by fuel type and by distance class from a given fuel type pixel. The risk of spotting within a given pixel was analyzed based on the risk presented by the surrounding fuel pixels, with distance radii based on fuel type. Distance class categories were analyzed as concentric circles around the target fuel patch, with higher ranking values associated with shorter distances, and with more volatile fuel types. The chance of spotting was considered to be “nil” for distances over two kilometers. Spotting values represent the estimated threat associated with 12 relevant fuel type-distance classes. The relative threat associated with each fuel type-distance class was ranked (“Spotting Rank”), based on expert opinions on the most frequent spotting concerns observed during wildfires. The rank values were assigned risk scores (weighting factor), which were adjusted to normalize the areas (since the larger concentric circles cover much more area than smaller ones). Each raster pixel (50 meter resolution) was then assigned a total score based on the sum of risk values contributed by all pixels within a radius of 1-2 kilometers. Based on this total score, the landscape was categorized into 10 spotting classes ranging from low to extreme.The classes were created by automatic classification, using the “natural breaks (Jenks)” setting of the ArcGIS 10.1 Spatial Analyst extension. Differences are caused by fuel type classes and distances, with no consideration given at this time to elevation or dominant wind direction. Future versions of this analysis will likely address both of these factors.Water bodies were overlaid on the raster and assigned their own class, -1.