Devastating wildfires, including the Palisades Fire and Eaton Fire, have ravaged areas near Los Angeles, scorching a total of 58 square miles since igniting on Jan. 7. While firefighters work to contain these fires, a new danger looms over the burn scar regions.
The Hazard of Debris Flows
Debris flows, fast-moving landslides carrying water, pose a significant threat. According to weather.com Senior Meteorologist Dina Knightly, these flows resemble a muddy river, laden with debris, rocks, and earth, propelled by water. Racing at speeds exceeding 35 mph down slopes, they can spread out and wreak havoc upon reaching lower elevations. Striking suddenly, they have the capacity to flatten or bury buildings and homes within minutes.
Burn scars heighten the risk of landslides and debris flows due to the absence of vegetation that would otherwise anchor the soil in place. Even brief rainfall events can trigger movement of land and debris in these vulnerable areas.
The Deadly Consequences
Landslides and debris flows can be lethal, as evidenced by the tragic event in Montecito, California in 2018, where mudslides claimed 20 lives. On average, 25 to 50 people lose their lives annually in the U.S. due to landslides, reports the USGS.
Professor Brad Johnson from Davidson College emphasizes that intense fires can create a soil crust that repels rainfall, creating dry, fire-prone landscapes vulnerable to further wildfires and landslides. Moreover, burning vegetation can leave a slick film on the soil, enhancing runoff.
Looking Ahead
Research indicates that Southern California routinely experiences debris flows following wildfires, and with multiple large fires currently burning, the likelihood of future debris flow events is high. Residents living on steep slopes should remain vigilant and consider relocating during forecasted heavy rain events.
Precautions to Take
Residents in landslide-prone areas are advised to closely monitor local weather forecasts and act promptly upon any rain warnings. Register for emergency alerts and familiarize yourself with evacuation routes to ensure a swift and safe escape in case of imminent danger.
Develop a plan with your family to establish a designated meeting spot in the event of separation. Do not delay in leaving if heavy rain emerges in a burn scar region, even without an evacuation order. The Eaton Fire and the Palisades Fire have now become the second and fourth most devastating wildfires on record in California, respectively. Together, they have reportedly destroyed approximately 12,000 homes and other structures, while claiming the lives of at least 27 individuals. A study from 2023 indicates that the increasing size and frequency of wildfires, attributed to climate change, are anticipated to result in more frequent debris flows.
