A High-resolution Recalculation of the Wildland Urban Interface Reveals Over $1 Trillion of California’s Residential Structures Are at Risk to Wildfire

Wildfire is a significant risk to property and people in the state of California. In 2018 alone, California's wildfire damages were estimated to be $148.5 Billion or 1.5% of the state's gross domestic product. Wildfire risks to property and people are at their highest at the intersection of flammable wildland vegetation and the built environment, a space called the Wildland Urban Interface or “WUI”. Existing methods for delineating the WUI, however, tend to be coarse in both spatial and temporal resolution, resulting in less precise estimates of WUI extent and change. This thesis uses high-resolution spatio-temporal data and classification methods to remap the WUI in California and to reassess the risk of residents and homes to wildfire. The findings from this analysis reveal that approximately $1.34 Trillion or 40% of the improved residential property value in the state falls within high wildfire risk areas. Likewise, areas classified as WUI account for over 10% of California's land area or a total of 43,205 square kilometers. While WUI areas cover a considerable portion of the state, the addition of a temporal element in this research shows WUI growth in California has slowed considerably over the past 10 years. The unique structure-level data integration strategy applied in this thesis provides a streamlined and expandable process for monitoring the WUI, enabling these new estimates of the hazard risk profiles of areas, structures, and people.