By Capt D. Napolean Robinson, USAF, and Christopher Chini, Ph.D.
Recurrent heatwaves and droughts across the western half of the United States, as well as the natural environment of the region, have historically caused the area to be plagued by wildfires. Each year, California and other western states struggle to contain fire spread and limit damage to buildings, land, and lives. These issues have only increased in frequency and intensity. During December 2020, the Santa Ana wind event caused multiple fires to erupt around Los Angeles, ushering in the largest wildfire season in California history at that time. Additionally, recent events such as the winter 2021 and spring 2022 wildfires in the greater Denver area have expanded the notion of a traditional wildfire season.
These wildfires threaten military installations across the western United States, as evidenced by recent evacuations and mission impacts in 2017 to Vandenberg SFB, Calif., and in 2020 to Travis AFB, Calif. As wildfires pose one of the largest threats to mission security in the west (and only heightened today by lengthening seasons and changes over time of site vulnerability), it is important to tabulate and quantify risk, uniformly, to better account for future impacts on defense operations and personnel safety.
ASSESSING IMPACTS
Human development has raised the propensity for wildfire incidents and risk, especially at wild-urban interfaces. California, for example, is currently in the midst of a three-year drought, with lake levels at or near historic lows across the state. This has reduced available water to fight fires and caused incendiary dead and dry foliage to be available year-round.
In 2019, the Department of Defense (DOD) released a report on the impacts of climate change to installations, with wildfire being one of the leading concerns. The report considered both current and future threats to wildfire, but it did not acknowledge differences in severity. In response, the Government Accountability Office found that installations across the services have not assessed what impacts from climate change their infrastructure may face in the future.
Recently, DOD has enlisted the Defense Climate Assessment Tool to assess relative disaster risk to installations across the country. And although wildfire liability is considered in this tool, the assessment mainly benefits strategic-level investment and not installation decision-making.
A promising tool to potentially fill this gap is FlamMap, a free fire behavior simulator developed by the Department of Agriculture to map a static fire behavior representation across the desired location. Used throughout the United States for wildfire research, FlamMap provides a way to quantitatively assess changing risk patterns at the installation level and spatially represent highly vulnerable areas to influence management and risk mitigation policies.
FlamMap’s strength is modeling fire probability and the risk of extreme weather scenarios based on conditional inputs for land analysis. This type of analysis is ideal to investigate burn probabilities based on weather conditions generated over monthly intervals. A minimum travel time formula computes burn probability based on the weather, fuel, and topography and a simulated ignition point. The result is a geolocated raster file containing a burn probability at each pixel of resolution.
QUANTIFYING RISK
To demonstrate the methodology of FlamMap, a team of researchers with the Air Force Institute of Technology conducted a case study of Vandenberg SFB. The installation was selected due to its location in a state that has been afflicted with drought, high winds, and multiple wildfires over the years.
Using historical weather data, the projected burn probability was simulated every two years from 2003 to 2017 for the summer months and for all months in 2003, 2009, and 2017. Averaging the value of each burn probability across the installation can create a metric of relative risk against other months, while the individual rasters can be used to pinpoint the highly probable locations and understand relative risk next to infrastructure.
With some variability due to drought years, there is a slight increase over time in burn probability for Vandenberg. The burn probability of a specific area within an installation could be used to quantify a location’s risk of wildfire when paired with infrastructure assets. Burn fire managers use probability maps to find the optimal locations for permanent lookout towers, locate areas of potentially limited suppression effectiveness, and identify zones that require landscape-level fuels management.
Burn probability for all months were studied for 2003, 2009, and 2017. Peaks and lows for burn probability are consistent for all three years. The year 2009 was still at an elevated risk by having probabilities higher than 2003 and 2017. Looking at the standardized precipitation index for California showed that 2003 and 2017 were relatively wet years, while 2009 was exceptionally dry—illustrating the important role drought plays in understanding changes to burn probability.
INFORMING DECISIONS
There are several opportunities to include these types of analyses from the FlamMap software. Installations could use the burn probability to understand how different climate factors, based on historical trends, might impact wildfire risk in the future. Similarly, FlamMap and its outputs could be a valuable tool to validate the results of the Defense Climate Assessment Tool. Though still in the early stages of usage, this tool was made to provide planning and land use recommendations through assessments to investigate mission impacts. Another possibility is to use the spatial outputs as an annual assessment of infrastructure risk and facilitate and prioritize wildland and infrastructure management policies. These spatial outputs could also be incorporated within existing geospatial management software to facilitate best infrastructure management practices.
Finally, because tools like FlamMap already exist, there is an incubated ecosystem possible for greater intra-governmental cooperation to facilitate these studies on a more nuanced and widespread scale. The U.S. Air Force currently works with the Department of Agriculture and National Wildfire Coordinating Group to manage wildfire threats, such as through the Air Force Wildland Fire Branch, a joint operation with the U.S. Fish & Wildlife Service and Bureau of Land Management. Currently, this group is focused on ensuring military preparedness by executing fuel reduction activities and wildfire mitigation. Incorporating quantitative tools into these organizations and installation management plans, specifically considering climate change, would benefit DOD in making climate-informed infrastructure decisions.
Capt D. Napolean Robinson, USAF, was Graduate Student, and Christopher Chini, Ph.D., is Assistant Professor, Air Force Institute of Technology. They can be reached at david. robinson.60@us.af.mil; and christopher.chini@afit.edu.
[This article first published in the September-October 2022 issue of The Military Engineer.]
