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El Niño Brings Risk Of Flash Flooding, Debris Flows Near Wildfire Scars

Burned landscape from the Rim Fire in 2013.


A strong El Niño is forecast to bring a wetter-than-normal winter to much of California.

But, the ocean warming condition can also create high intensity rainfall events that cause mudslides, flash floods and debris flows in areas recently scarred by wildfires. 

And those hazards aren’t just a risk for Southern California. 

"Even in Northern California we are going to see an increased risk," says Meteorologist Michelle Mead with the National Weather Service in Sacramento. 

She says people living near in areas burned the last three years, such as Lake, Amador or Calaveras counties, should be prepared. 

"Mainly know your risk," says Mead. "Know where you are in proximity to the burn scar. You should be able to contact your emergency manager of the county." 

Mead says the counties, the National Weather Service and the U.S. Geological Survey will have specific data on what burn areas pose the most risk from debris flows. 

She says four years of drought increases the potential for flash flooding and debris flows. 

Mead says debris flows can happen with little warning. 

She suggests people living near areas scarred by wildfire be prepared to evacuate quickly. 

"It's all about situational-awareness, where you are in proximity to the burn scar," says Mead. "Are you at the end of a drainage, meaning you could be 10-15 miles away from the scar, but you happen to be at the bottom of a canyon that is upstream of the burn scar. So, basically you're a chute for some of that debris flow to come down into your area." 

The U.S. Geological Survey says "post-fire landslide hazards include fast-moving, highly destructive debris flows that can occur in the years immediately after wildfires in response to high intensity rainfall events, and those flows that are generated over longer time periods accompanied by root decay and loss of soil strength." 

The agency also says wildfires could potentially result in the "destabilization of pre-existing deep-seated landslides over long time periods."

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