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Helicopters plucked dozens from rooftops in Southern California after mudslides in wildfire-scorched areas swept away or damaged homes. A family of five and their two dogs were rescued in Santa Barbara County. At least 13 people are dead. (Jan. 10)

Media: Associated Press

Residents of the area hit the hardest by the deadly flash floods in Southern California didn't heed a voluntary evacuation.

In Montecito, California, the vast majority of people under mandatory and voluntary evacuation orders early Tuesday stayed in their homes, 400 of which were either destroyed or damaged. At least 17 people died.

Evacuation orders are generally based on weather conditions, projected storm or fire patterns and the immanency of the threat.

Oftentimes, the feared devastating flames, floodwaters and mudslides don't materialize. After false alarms, some residents opt to ignore voluntary evacuation requests.

But experts say disasters can change course in an instant.

Photo: Matt Udkow, AP

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This aerial photo provided by the Santa Barbara County Fire Department shows mudflow and damage to homes in Montecito, Calif., Wednesday, Jan. 10, 2018. Anxious family members awaited word on loved ones Wednesday as rescue crews searched grimy debris and ruins for more than a dozen people missing after mudslides in Southern California on Tuesday destroyed over a 100 houses, swept cars to the beach and left more than a dozen victims dead. (Matt Udkow/Santa Barbara County Fire Department via AP) less

Photo: Matt Udkow, AP

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A firefighter stands on the roof of a house submerged in mud and rocks Wednesday, Jan. 10, 2018, in Montecito, Calif. Anxious family members awaited word on loved ones Wednesday as rescue crews searched grimy debris and ruins for more than a dozen people missing after mudslides in Southern California destroyed houses, swept cars to the beach and left more than a dozen victims dead. less

Photo: Marcio Jose Sanchez, AP

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A car sits stranded in flooded water on Highway 101 in Montecito, Calif., Wednesday, Jan. 10, 2018. Dozens of homes were swept away or heavily damaged and several people were killed Tuesday as downpours sent mud and boulders roaring down hills stripped of vegetation by a gigantic wildfire that raged in Southern California last month. less

Photo: Marcio Jose Sanchez, AP

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This January 2017, photo provided by Kelly Weimer, shows Jim Mitchell, 89, with his wife, Alice Mitchell, 78, and their dog, Gigi. The Mitchell's and their dog have been missing since Tuesday, Jan. 9, 2018, when their Montecito, Calif., home was swept away by the torrent of mud, trees and boulders that flowed down a fire-scarred mountain and slammed into the coastal town in Santa Barbara County. (Kelly Weimer via AP) less

Photo: Kelly Weimer, AP

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Members of the Los Angeles County Fire Department Search and Rescue crew work on a car trapped under debris in Montecito, Calif., Wednesday, Jan. 10, 2018. Dozens of homes were swept away or heavily damaged and several people were killed Tuesday as downpours sent mud and boulders roaring down hills stripped of vegetation by a gigantic wildfire that raged in Southern California last month. less

Photo: Marcio Jose Sanchez, AP

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A member of the Los Angeles County Fire Department Search and Rescue crew works near a car trapped under debris in Montecito, Calif., Wednesday, Jan. 10, 2018. Dozens of homes were swept away or heavily damaged and several people were killed Tuesday as downpours sent mud and boulders roaring down hills stripped of vegetation by a gigantic wildfire that raged in Southern California last month. less

Photo: Marcio Jose Sanchez, AP

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This photo provided by the Santa Barbara County Fire Department shows mud, boulders, and debris that destroyed homes that lined Montecito Creek near East Valley Road in Montecito, Calif., Wednesday, Jan. 10, 2018. Anxious family members awaited word on loved ones Wednesday as rescue crews searched grimy debris and ruins for more than a dozen people missing after mudslides in Southern California on Tuesday destroyed over a 100 houses, swept cars to the beach and left more than a dozen victims dead. (Mike Eliason/Santa Barbara County Fire Department via AP) less

Photo: Mike Eliason, AP

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This photo provided by the Santa Barbara County Fire Department shows the cleanup of mud and debris in front of the Coral Casino and Biltmore Hotel along Channel Drive in Montecito, Calif., Wednesday, Jan. 10, 2018. Anxious family members awaited word on loved ones Wednesday as rescue crews searched grimy debris and ruins for more than a dozen people missing after mudslides in Southern California Tuesday destroyed houses, swept cars to the beach and left more than a dozen victims dead. (Mike Eliason/Santa Barbara County Fire Department via AP) less

Photo: Mike Eliason, AP

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"Disasters are very dynamic in danger. They can change from minute to minute," said Scott Somers, an emergency management professor at Arizona State University. "Just because an area can be safe at 1 o'clock in the afternoon doesn't mean it is going to be safe at 3 p.m."

Jim and Alice Mitchell, whose house was swept away when the flash floods cascaded through their neighborhood, had not left their home because they were not under a mandatory order, their daughter, Kelly Weimer said Wednesday. Nearly every home on their block was completely destroyed and others were lifted and tossed from their foundation.

"They were in a voluntary evacuation area so they figured they were OK," said Weimer, who has been frantically searching for her parents for more than a day. "They weren't concerned. It's not like anybody came around and told them to leave."

Weimer, 53, spoke to her parents on Monday to wish her father a happy 89th birthday. The couple of more than five decades planned to stay in because of the rain and have a quiet dinner. Weimer hasn't heard from them since and pictures from the area show their home on Hot Springs Road was completely gone.

"This isn't an exact science in terms of actually defining where something is going to happen," Santa Barbara Sheriff Bill Brown said. "Obviously a lot depends on Mother Nature, on the magnitude of the rainfall, the magnitude of the mudslides and so forth, and I think what was put together by a team of people, meteorologists, Cal Fire, our Forest Service people, our firefighters and personnel from the flood district and so forth, made a best-guess estimate as to where this was going to occur, and as it turns out they were exactly right that this was going to hit."

Brown said sheriff's deputies went door to door in the mandatory evacuation area, knocking on 7,000 doors to tell them to leave their homes hours before the storm swept through. Some refused to leave. Officials did not respond to questions Wednesday about whether they had sent alerts to cellphones in the evacuation area, which have been used previously to warn California residents of threats from wildfires and flash floods.

Still, officials across California said it is critical for residents to heed the warnings as early as possible and be prepared to immediately evacuate if they are in a warning area. In Los Angeles, teams evaluate potential threat areas by examining the potential road blocks, slope erosion and the possibility of deadly conditions and then decide which areas should be under mandatory evacuation orders or voluntary warnings.

"We understand the impact there is to people to leave their homes and their belongings. We do not take issuing evacuations lightly," said Capt. Erik Scott, a spokesman for the Los Angeles Fire Department.

When their home of 40 years was under threat from the wildfire last month, Marco Farrell and his parents evacuated and remained away for more than a week. This time around, a voluntary evacuation order was issued for their area and the family discussed leaving but decided to ride it out.

"There was evacuation fatigue from the fire," Farrell acknowledged. "I would have preferred for them to leave and in hindsight we should have left. I don't know how I got lulled."

What will he do the next time there's an evacuation order? "Definitely go," he said.

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Associated Press writers Amanda Lee Myers and Frank Baker in Los Angeles contributed to this report.

Residents didn't heed voluntary evacuation before mudslide

Updated 3:25 am, Thursday, January 11, 2018