Wildfires and power outages caused by vegetation near powerlines have contributed to some of the state’s most destructive fires.
To better understand and avoid those risks and guide safer management, researchers at Cal Poly Humboldt partnered with a utility company to study tree failures (falling trees and branches) and fuel buildup along powerline corridors.
“Working directly with the utility company allowed us to connect what we were seeing in the field with real-world risks to communities,” says Forestry Professor Lucy Kerhoulas, a lead researcher of the study. “The goal was to identify where and why tree failures are happening, so management efforts can be focused where they matter most.”
Kerhoulas conducted the study alongside Cal Poly Humboldt faculty Rosemary Sherriff, Geography, Environment & Spatial Analysis professor; Kerry Byrne, Environmental Science & Management professor; and Zoe Ziegler, Forestry graduate student.
The study, published in the Journal of Environmental Management, focuses on rural, heavily timbered regions of Northern California, where power outages caused by falling trees and branches are common and can also spark wildfires.
“Tree failures can cause fire ignitions and/or power outages, which can create a lot of issues for residents,” Kerhoulas says. In fact, outages caused by falling trees or branches are among the most common reasons for power outages, and can impact hundreds of thousands of people at a time.
By comparing vegetation near powerlines with vegetation farther away, researchers identified several factors that increase risk.
One of the study’s most notable findings was higher levels of woody debris near powerlines. In many cases, tree-felling and pruning by utility vegetation crews left coarse woody material on the ground, increasing fuel loads around powerlines. Removing that debris is a key step in reducing wildfire risk, the researchers found.
The team also found that some vegetation types are more vulnerable to failure than others. Oaks, for example, showed higher levels of damage than conifers, making them a higher priority for management. Areas with dry conditions and thick duff layers also had increased tree failures, making them a high priority for management treatments to minimize the risk of potential ignitions. Beyond fuel concerns, the researchers found that effective vegetation management can help reduce beetle infestations, which weaken trees and make them more likely to fail.
Looking ahead, researchers hope to use remote sensing tools such as the Normalized Difference Vegetation Index (NDVI). NDVI, according to NASA, measures vegetation “greenness” to assess plant health. Integrating satellite data with on-the-ground observations could help utility companies scale this study’s findings to larger landscapes to more efficiently identify high-risk areas and prioritize preventive work.
These strategies, Kerhoulas said, not only protect infrastructure but also enhance community safety.
“Ultimately, even small changes in how vegetation is managed near powerlines can make a big difference in preventing fires and keeping the lights on,” she says.