It was a skepticism that sheriff's deputies witnessed firsthand. One resident wrote on social media that it took a 20-minute conversation with officials before they ultimately decided to leave their home for the night.
"I've seen experts opine about how you essentially not only have to warn people but you sort of have to convince people," Brown said. "That's a difficult order, but one we're obviously going to have to take a look at."
But there isn't a lot of science available on what message will truly make people appreciate a danger they cannot see, said Art Botterell, senior emergency services coordinator with the governor's office.
"I'm afraid what makes them resonate is bitter experience," he said. "If people haven't experienced a hazard recently, they tend not to personalize it."
Warnings need to be repeated and reinforced with other indicators, he said. If a resident sees a warning about a landslide from the National Weather Service and looks outside and only sees drizzling rain, they won't be convinced, Botterell said.
But if other neighbors are leaving, they might take it more seriously. Or if a message from the weather service is followed up by a text alert from the county, then a broadcast on TV, radio or social media, the chances of people heeding the warning increases, he said.
"It's just like advertising -- repeated impressions make a difference," Botterell said.
The danger of debris flows or floods are particularly challenging because they're stealthy, according to experts. In most cases, people can see a fire raging over a hillside and smell it from miles away.
A landslide moves in with a whisper.
"People are going to evacuate when there's a cop on every corner. They'll stay out when there's National Guard on every street," said James Langhorne, who was the fire marshal for the Montecito Fire Protection District for 23 years before retiring nine years ago. "The real issue is that people have to own a piece of this thing. It's not something you can do for them."