UCSB geology expert on storm: ‘It’s a time to be careful and watchful’

SANTA BARBARA, Calif. - Dr. Ed Keller, Professor of Geology at UC Santa Barbara and one of the foremost experts on tectonic geomorphology, spoke with your NewsChannel about local areas at risk as a large, pacific storm heads our way.

"It really depends on the rainfall intensities," said Keller during a Tuesday morning Zoom call. "The rainfall intensity from this storm are probably going to be up to the 3/4 inch an hour, which is right about the threshold for debris flows."

The earth surface expert said there is also the chance for a "damaging flash flood" with this system, which can carry the potential to take lives and damage property. However, that does not mean the community will see a large-scale disaster like we endured with the 1/9 Montecito mudslide of 2018.

"Based on probability analysis, there is about a 6% chance in the next 100 years for a 2018 size event," said Keller. "But it is possible, in a given year, to have another very large debris flow event, especially in the first few years following wildfire, if intense rainfall occurs."

Keller said the Santa Barbara area gets smaller debris flow events every 10 to 20 years, and these smaller-scale disasters are becoming more common in our area because of climate change.

"They're fairly common because our return period of fires is somewhere between 20 to 30 years. The bigger ones, like 2018 [Montecito disaster] are rare events. But, we're lucky we do get warnings."

Keller said potential hazard areas most at risk during heavy rain forecasted for Wednesday and Thursday would be alongside local creeks, areas of Montecito below the Thomas Fire burn scar and La Conchita. The beachside mountain landslide happened in 1995, followed by a major collapse in 2005 that killed 10 people.

"That [La Conchita] is a disaster just waiting to happen. It will happen. It's just a matter of when," said Keller. "The Thomas Fire is three years old and we have had debris flows three years following a wildfire."

The County's effort to clear debris basins in the hills above Montecito and Carpinteria brings a huge added layer of protection for neighborhoods below the Thomas Fire burn scar.

Keller said the danger behind this week's storm system is linked to what's known as an "atmospheric river."

"We get huge atmospheric rivers about every 200 years, really more common than the really big debris flows and they've caused intense damage. They can bring as much rainfall as the biggest rivers in the U.S. The amount of water they have in them is immense."

The biggest one happened "a couple hundred years ago," that brought 30 to 40 inches of rain in just a few days. This week, Keller encourages people to be especially watchful and aware of their surroundings.

"My advice to anybody is, if you get a notice to evacuate, you should evacuate."