Wildfires began erupting around Los Angeles at the dawn of 2025, quickly engulfing forests and homes alike. The blazes are sweeping through Southern California, bolstered by drought conditions and strong Santa Ana winds. The fires remain uncontained and are already deemed among the most destructive in LA history.
This current wave is the latest in a series of devastating wildfires that have ripped through the western U.S. over recent decades, burning vast swaths of forest and obliterating towns. Over Labor Day weekend in 2020, wildfires swept through Washington, Oregon, and California, causing widespread damage to communities. Those wildfires burned nearly 3.5 million acres in that trio of states, not only burning forests and buildings but also damaging infrastructure like electrical lines, pipelines, and roads.
Further reading:
- Devastating wildfires hit close to home for LA civil engineers
- What happens when a wildfire rips through your neighborhood
- A collection of wildfire resilience articles
Once a fire is contained, researchers and emergency managers pore over the area, documenting the aftermath and damage to the region. Although the backbone of any recovery effort requires a healthy infrastructure system, roadway damage can often be an afterthought.
In a paper published in Emergency Management, researchers delved into how climate change and wildfires have caused infrastructure damage over the past two centuries. The study could help managers better direct recovery efforts for future – or current – wildfire events.
Fire vs. pavement
When the dry, hot, and windy weather of the western U.S. meets with dehydrated forest fuel sources, wildfires can be unwelcome visitors. Lightning strikes, overheated vehicle undercarriages, sparking power lines, or errant campfires can trigger giant fires that sweep across states. These fires have ballooned into humongous disasters, and researchers have begun categorizing them with descriptive prefixes: megafires, gigafires, and terafires, burning more than 40,000, 100,000, and 1,000,000 hectares, respectively.
While wildfires have profound impacts on communities and ecosystems, not all damages get the same attention. “This study is a first attempt to evaluate the risks, dangers, and harm to road infrastructure caused by megafires, which are frequently disregarded when calculating hazard risk, vulnerability, and resilience,” said Kevin Christiansen, Ph.D., a construction manager for HDR and lead author of the research study.
Wildfire-urban interfaces – where fire meets communities – can range from rural settings like small towns in Oregon to urban environments like what we are witnessing in LA. The increased interactions with built environments mean a research shift is happening after a fire.
“Historically, wildfires have been researched by forest ecologists, by the U.S. Forest Service, by fire science experts,” explained Erica Fischer, Ph.D., P.E., M.ASCE, a structural engineering associate professor at Oregon State University and a member of the ASCE/Structural Engineering Institute Fire Protection Committee. “It's really only in the last less than a decade that civil engineers are involved in the research on wildfires.”
Fire causes damage and regional transportation problems to highways in burned areas.
“The way that fires can damage roads is exactly what we're seeing in LA,” Fischer said. She described all the cars abandoned on roads to burn, damaging the concrete and creating spalling that can remove chunks of roadway. “That’s just the direct impact; there’s all kinds of peripheral impacts that can impact your transportation networks and roads and make them unusable.”
Christiansen added that roadway impacts include teetering trees or those that have fallen onto highways, pavement damage (like burning asphalt), structural damage to signs and guardrails, and slope instability issues that linger after a burn. These problems cost a lot of money to mitigate, and these repairs can close roads or slow daily commutes for residents, causing disruption that continues long after the fire has been contained.
After the fire, there can be even more risk to roadways as the community tackles recovery. Debris must be removed from an area before rebuilding can start, and that means big trucks moving heavy materials on damaged pavement. For instance, Fischer recalled that after the Marshall fire, which struck Colorado three years ago, one of the affected communities received money from the Federal Emergency Management Agency to repair roads.
“We told them not to repair the roads until after the debris had been removed,” she said. Even in the best of times, most roads aren’t intended for that many trucks to drive over in such a short period of time. The result was unsurprising. “They decided to repair the roads. … Then they realized exactly what we were talking about, and they had to then rerepair the roads after the debris was removed,” she added.
Fire history and roadway damages
Megafires, like those in 2020, appear to have increased substantially over the past three decades – potentially because of the influence of climate change, Christiansen said. But he and his colleagues wanted to look at fires over the past two centuries to see the long-term pattern of wildfire frequency and associated highway damages.
They collected records of wildfires, including the years, hectares burned, reported causes, and locations of the fires in Washington, Oregon, and California. In total, they found records of 74 fires over nearly two centuries caused by lightning (49%), human activity (26%), unknowns (12%), power transmitters/power lines (8%), and land clearing/logging (5%).
They found that detailed records of roadway damages from historical fires was virtually impossible.
“It’s extremely difficult to capture these damages in historical wildfires because the documentation produced is usually missing information,” said Christiansen, adding that trying to find and talk to personnel who worked on road repairs is extraordinarily challenging. He noted that the team could not find any roadway infrastructure damage data documentation related to megafires prior to the 21st century.
“Throughout the research, it became apparent that there is not an efficient or accurate way to collect data on this topic,” he said.
They decided to use the 2020 megafires as a case study and created a method for classifying road damage. They considered traffic control, slope-rock scaling, hazard trees, and structures as critical information to collect for documenting damages. Using this methodology, they found the anticipated repair costs after the 2020 megafires tallied $3 million for traffic control, $17.5 million for slope-rock scaling, $24 million for hazard trees, and $43 million for structural damages. Overall, damages cost the affected states $127,783 per kilometer.
Christiansen says the research shows the need for comprehensive data collection to better assess the risk of wildfire to roadway infrastructure.
“We should examine more states and their megafires to develop a more detailed statistical analysis and standardization of financial estimates of the costs for road characteristics for use in estimating the risk of future wildfires,” he said.
Collecting comprehensive data is an important first step in prioritizing emergency preparedness and recovery.
“Ultimately, what communities need to think about is what we call strategic fire planning,” Fischer explained. She said this can include determining which roads are most critical for evacuation and firefighter access and also for long-term economic and social recovery. “A lot of communities have gone through this for other hazards like hurricanes, floods, or earthquakes,” she said, adding that civil engineers and mitigation experts should view wildfire hazards in the same holistic way.
“I think ASCE does a good job of bolstering multidisciplinary research and kind of thinking across hazards,” Fischer said. “No community is only exposed to one hazard; now we have climate as a hazard as well.
"This is why we need civil engineers working in this field so that we can address wildfire as we have all the other hazards and the large swath of infrastructure impacts.”
