Quantifying Colorado’s Current and Future Wildfire Risk: Development of a Climate-Informed Wildfire Analysis

Abstract:

The state of Colorado is actively looking to better identify, quantify, prioritize, and manage their climate change risk as it relates to flood, drought, and wildfire natural hazards. To quantify and monetize the cost of future hazards, we developed a new hazard risk assessment framework to quantify statewide (county-level) economic impacts resulting from climate change and population growth by the year 2050.

The wildfire analysis leveraged the state’s existing wildfire model to quantify damages for current conditions as well as two future climate scenarios and three future population scenarios for a total of 12 combined scenarios. Risk, expressed as damages in dollars, was calculated as the product of wildfire hazard and asset vulnerability. The wildfire behavior modeling was completed using Technosylva’s Wildfire Analyst to calculate annual burn probabilities and fire intensity. Asset exposure was determined using building replacement costs from the Hazus building stock inventory, while asset susceptibility was calculated using a predefined relationship between intensity (flame length) and building damage. Future climate change was modeled by adjusting air temperature using temperature offsets derived from general circulation models (GCMs) and live fuel moisture content (LFMC) by developing a relationship between the Standardized Precipitation Evapotranspiration Index (SPEI) and observed LFMC. Population growth scenarios were spatially modeled using the EPA’s Integrated Climate and Land Use Scenarios (ICLUS) version 2, combined with Colorado’s future population estimates by county. The result of the analysis was a statewide gridded risk data product, which was aggregated to the county level. Results indicate that climate change alone could increase wildfire damages by 1.6 to 1.7 times current costs, while population growth alone could increase wildfire damages by 1.6 to 1.9 times current costs, and the combined effects could increase wildfire damages from 2.1 to 2.9 times current costs.