A helicopter dropping water on a California wildfire in rugged terrain. (Photo by David Aughenbaugh/iStock.com)Burning questions
California has recorded more than 6,000 wildfires this year, underscoring the need for better mitigation strategies to reduce their devastating impact. Now, researchers have created a wildfire simulation model that may shed light on how these fires spread through communities in the wildland-urban interface (WUI), enabling us to better assess the wildfire risks and build more resilient communities.
The model is the first of its kind to fully integrate wildland and urban fire spread processes, filling a major gap in current tools by introducing data such as structural construction materials, surrounding vegetation and the intensity of approaching flames. The model also addresses the three primary pathways for WUI fires to spread: direct flame contact; radiation, or the intense heat emitted by flames; and firebrand ignition, when flammable vegetation or structural materials break off and travel ahead of the advancing fire, as seen with embers.
The researchers seamlessly integrated their WUI model with ELMFIRE, an existing tool that simulates wildland fire spread and is used by power companies and counties across the state for risk assessment.
To test it, the researchers simulated the Tubbs and Thomas fires, two historical and devastating WUI fires that occurred in 2017. Even accounting for a certain level of built-in uncertainty, the model’s predictions achieved an accuracy exceeding 85% for fire perimeters and around 70% for the damaged houses, with over 30% of the houses ignited by firebrands. In addition to validating the role that urban structures play in spreading fires, the model outputs provided new insights into how fire behaves in these settings.
“Fire does spread slower in the community than through the forest and the trees, but it’s also very destructive. The behavior is different,” said Michael Gollner, associate professor of mechanical engineering. “The way a house burns is different, and by including that data in our model, we now see the influence of each process — of the houses burning, of their arrangement side-by-side, of the weather — and how all those processes and factors play together.”
Dwi M.J. Purnomo, postdoctoral scholar, was the study’s lead author. Maria Theodori, Ph.D. student, and Maryam Zamanialaei, postdoctoral scholar, were co-authors, along with researchers from the University of Maryland, College Park and CloudFire Inc.