U.S. Geological Survey Landslide Hazards Program

Force in Play

Providing post-fire debris flow hazard assessments and early warning support

A Christmas Day atmospheric river dumped up to 12 inches of rain on Southern California's mountains, triggering mudslides that buried roads in Wrightwood and forced helicopter rescues from rooftops. More than 120 emergency responders worked overnight Christmas Eve rescuing residents trapped in vehicles and homes. Governor Gavin Newsom declared emergencies in six counties covering 28 million people. At least three to four died. By December 26, the worst of the storm had passed, though flood risks persisted through Friday evening. The twist: these floods hit burn scars from massive wildfires earlier in the year, where charred soil repels water like pavement and half an inch of rain can unleash catastrophic debris flows.

Updated Dec 26, 2025