Hazards of Risk: Identifying Plausible Community Wildfire Disasters in Low-Frequency Fire Regimes

Abstract

Optimized wildfire risk reduction strategies are generally not resilient in the event of unanticipated, or very rare events, presenting a hazard in risk assessments which otherwise rely on actuarial, mean-based statistics to characterize risk. This hazard of actuarial approaches to wildfire risk is perhaps particularly evident for infrequent fire regimes such as those in the temperate forests west of the Cascade Range crest in Oregon and Washington, USA (“Westside”), where fire return intervals often exceed 200 years but where fires can be extremely intense and devastating. In this study, we used wildfire simulations and building location data to evaluate community wildfire exposure and identify plausible disasters that are not based on typical mean-based statistical approaches. We compared the location and magnitude of simulated disasters to historical disasters (1984–2020) in order to characterize plausible surprises which could inform future wildfire risk reduction planning. Results indicate that nearly half of communities are vulnerable to a future disaster, that the magnitude of plausible disasters exceeds any recent historical events, and that ignitions on private land are most likely to result in very high community exposure. Our methods, in combination with more typical actuarial characterizations, provide a way to support investment in and communication with communities exposed to low-probability, high-consequence wildfires.

A quantitative wildfire risk assessment using a modular approach of geostatistical clustering and regionally distinct valuations of assets—A case study in Oregon

“…Fig 7 shows the distribution of ORR on private and public land in Oregon. The values show that with exception of FSA 4, the largest percentages of public land are assigned to the high ORR and highest ORR classes whereas the biggest portion of private areas is assigned to the lower and lowest ORR classification which agrees with similar distributions found in recent related studies [ 17 , 30 ].…”

“…This was done to account for the increasing frequency and severity of droughts and projected increase in air temperature in the Pacific Northwest and thereby considering highest risk fire weather conditions as recorded by the stations for our risk analyses. Moreover, if mean-based parameterizations are used, fire hazard can be potentially underestimated for low frequency fire regimes as found in the coastal region of Oregon where low-probability, high-consequence wildfires have recently destroyed significant amounts of assets and resources [ 30 ].…”

Cascadia Burning: The historic, but not historically unprecedented, 2020 wildfires in the Pacific Northwest,USA

“…Infrequent, stand‐replacing fires are low‐probability, high‐consequence events akin to other natural hazards that westside communities face, such as earthquakes and tsunamis (McEvoy et al, 2021). These events are rare, difficult to forecast, and result in profound negative consequences to human communities.…”

“…This approach is less common for wildfires, potentially leading to distorted risk perception and complacency in community adaptation (e.g., Aven & Krohn, 2014;Kates & Clark, 1996;Kunreuther et al, 2001). Given the potentially high consequences and relatively low wildfire risk to communities, westside communities face considerable challenges in accessing and allocating resources to effectively plan for and mitigate low-probability, high-consequence events (McEvoy et al, 2021).…”

Potential operational delineations: new horizons for proactive, risk-informed strategic land and fire management

“…One area is improving PCL modeling, for instance by capturing more information on historical fire perimeter progression and containment operations, and by integrating with analyses of fuelbreak and fireline effectiveness (Gannon et al 2020;Simpson et al 2021). Risk assessments can be improved by increasing the rigor of expert elicitation, better examining low-probability, high-consequence events, and incorporating more diverse stakeholder values and perspectives (McFayden et al 2019;McEvoy et al 2021;Essen et al 2021). For strategic response categories, risk-informed incident response is best described as a continuum that adapts to changing conditions (Thompson et al 2016a), such that developing dynamic or condition-based strategic response categories is likely a needed evolution.…”