High wildfire damage in interface communities in California

Abstract

Globally, and in the US, wildfires pose increasing risk to people and their homes. Wildfire management assumes that buildings burn primarily in the wildland–urban interface (WUI), where homes are either ignited directly (especially in intermix WUI areas, where houses and wildland fuels intermingle), or via firebrands, the main threat to buildings in the interface WUI (areas with minimal wildland fuel, yet close to dense wildland vegetation). However, even urban areas can succumb to wildfires. We examined where wildfire damages occur among urban, rural and WUI (intermix and interface) areas for approximately three decades in California (1985–2013). We found that interface WUI contained 50% of buildings destroyed by wildfire, whereas intermix WUI contained only 32%. The proportion of buildings destroyed by fires among classes was similar, though highest in interface WUI areas (15.6%). Our results demonstrate that the interface WUI is where most buildings were destroyed in California, despite less wildland fuel. Continued advancement of models, mitigation and regulations tailored for the interface WUI, both for California and elsewhere, will complement the prior focus on the intermix WUI.

Building Loss in WUI Disasters: Evaluating the Core Components of the Wildland–Urban Interface Definition

“…Our finding, that building loss mostly occurs in areas with low building densities and high vegetation cover, supports previous findings [35,[48][49][50]. Higher losses in rural intermix environments with more wildland vegetation may be due to multiple factors, such as: continuous vegetation providing more potential for fire spread and building ignition, lower fire response capacity, the relative inaccessibility of dispersed buildings, or incident managers' choices to direct resources to areas with higher-density clusters of buildings [51].…”

“…In areas where wildland hazardous fuel reduction projects are not feasible, there may be a benefit to the removal of flammable landscaping and the implementation of building hardening techniques. Our results, which describe the pattern of loss in different environments, underscore the need to tailor distinct mitigation techniques across a range of building density, vegetation cover, and community types, including some areas that are not traditionally considered at risk [16,[48][49][50]. Fine-scale WUI maps of at-risk buildings also provide the potential to improve quantitative wildfire risk assessments, refine estimates of values at risk, and better identify community wildfire exposure zones [17,18,20,52].…”

Vegetation fires in the Anthropocene

“…In recent years, for example, there have been increasing media reports of major fire disasters: the wildfires in Chile in 2017, Portugal in 2018, California in 2018 and Australia in 2019-2020 are prominent examples. Such fires have major economic impacts, affecting life, property and human health [26][27][28][29] , thus, it is important to consider contemporary and future trends in fire activity to inform adaptation and mitigation policies. For instance, the 2019-2020 Australian Black Summer is likely the nation's most costly natural disaster, costing over AUD $100 billion 30 , whilst California in the USA saw an estimated USD $40 billion(NatCatSERVICE) in structure losses alone in a dozen major wildfires in 2017-2018.…”

Exposure of the Canadian wildland–human interface and population to wildland fire, under current and future climate conditions

“…Furthermore, specific preventive fuel management options may be prioritized depending on the WUI type. For example, densely populated and built-up interface areas could cost-effectively benefit from local fuel removal or fuel reduction in their immediate vicinity, because firebrands, landscaping vegetation, and other buildings are common sources of ignition (Partners in Protection 2003;Cohen 2004;Scott et al 2016;Kramer et al 2019). In comparison, large-scale fuel treatments, such as prescribed burns, would be an appropriate option in intermix areas.…”