Interface Areas Are Critical to Wildfire Losses
Residential development in the wildland-urban interface (WUI) is a major factor in the increased risk and costs of wildfire and managing that risk falls primarily on local communities in fire-prone areas. Wildfire policy typically focuses on the WUI, where homes meet or intermingle with wildland vegetation, in an attempt to reduce building ignition from either nearby vegetation or from firebrands. A USDA Forest Service scientist and her partners examined wildfires across California over the 28-year period, between 1985 and 2013, to fully characterize the challenges wildfire poses to homes and buildings in this densely developed and fire-prone state. The study included the 2017 Tubbs Fire as a recent case study of a notably destructive and urban wildfire. The scientists found that interface WUI areas (developed areas that have sparse or no wildland vegetation but are within close proximity of a large patch of wildland) accounted for the majority of building destruction in California wildfires that destroyed at least one building. These interface WUI areas contained 50 percent of buildings destroyed by wildfire, but composed only 2 percent of the area burned by these wildfires. Intermix WUI contained 32 percent of buildings destroyed by wildfire, despite the fact that intermix areas are where homes are intermingled with fuels. This research highlights the need to incorporate non-wildland vegetation, buildings, propane tanks, wood piles, and vehicles that also fuel fire in the WUI in wildland fire behavior models. In the Tubbs Fire, similar to other California wildfires, destruction was primarily in the WUI; however, the Tubbs was unique in having 25 percent of all destruction in urban areas (in comparison to 4 percent of destruction falling within urban areas for other California fires). Other recent and highly destructive fires including the 2018 Carr, Camp, and Woolsey fires included no urban area within their perimeters, exemplifying the rarity of the Tubbs’ building destruction in urban areas.