Hydrologist warns of heightened landslide potential as weekend storms approach

United States Geological Survey models indicate that as little as 0.2 inches of rain within 15 minutes could trigger dangerous debris flows in local Eaton Fire burn areas, representing one of the lowest thresholds observed in the region’s recent fire-affected zones. 

“A large fraction of the Eaton burn area has burned at least moderate burn severity, leaving bare soil vulnerable to erosion,” said United States Geological Survey Research Hydrologist Jason Kean. He added, “The combination of increased potential for runoff and easily eroded sediment substantially increases the

susceptibility of the burn area to floods and debris flows relative to what it was before the fire.” 

Kean explained that the burn area faces both immediate and long-term risks. 

“For recent burn areas … it is the rainfall intensity that matters, not the total precipitation,” he said. “Intense bursts of rainfall can come in localized thunderstorms, or it can be embedded in long-duration rainstorms.” 

Working with state and federal emergency response teams, the United States Geological Survey has mapped most of the burned drainages as high hazard zones, seen on their emergency response dashboard here. 

The assessment shows that even before rainfall, sediment from steep burned slopes has already begun moving downslope. 

“Down the road (typically three or more years after the fire) prolonged moderate intensity rainfall can saturate hillslopes and trigger shallow landslides,” Kean noted. 

In response to these concerns, the National Weather Service Los Angeles/Oxnard has issued a Flood Watch from 4 p.m. Sunday through 4 p.m. Monday for the Eaton Fire burn area. 

Rain rates during this period are expected to exceed the USGS debris flow thresholds. 

Residents in affected areas should monitor forecasts and be prepared to take action should flooding develop. Additional flood safety information is available at www.weather.gov/safety/flood