Science & Technology



Wind, embers and defensible space: The science of destruction in Laguna Niguel

Tony Briscoe, Alex Wigglesworth, Hannah Fry and Paul Duginski, Los Angeles Times on

Published in Science & Technology News

“That’s changed in the last decade or couple decades,” she said. “What we have seen are urban conflagrations that start from wildland fires and then move into more densely built areas.”

Kolden attributes the resurgence to the fact that fires are igniting closer to the built environment, as development continues to push into wildland areas. Meanwhile, the climate change-supercharged drought has made it more difficult for authorities to prevent fires from reaching these populated areas, she said.

“They’ve got a heavy fuel load on those hillsides, it’s very, very dry this year, consistent with the drought in California, and it essentially is not containable before it gets into the neighborhoods,” she said. “And that is what we have seen, especially in the last five to 10 years across not just California but many places across the West and across the U.S.”

On top of that, Kolden said, it’s common for homes in areas that burn in these types of fires to have been built before contemporary building codes were enacted to minimize house-to-house spread. That appears to have been the case in the Coastal fire, which is burning in the highest fire severity zone as designated by Cal Fire, she said. At least 18 homes that burned were built in the late 1980s or early 1990s; two others were built in the late 1990s.

Chapter 7A of California’s building code lays out regulations for new homes built in designated fire hazard severity zones that include using non-combustible materials for roofs, wall sidings and eaves; attic vents that prevent embers from entering houses; and double-pane, tempered glass windows. The rules took effect in 2008 and apply only to new construction, and there is no requirement for homeowners to perform retrofitting.

Even if some homes had been retrofitted, Kolden added, if others hadn’t, the entire neighborhood could remain vulnerable, with embers either jumping hardened homes and igniting the next un-hardened structure, or finding a way to enter even the hardened homes.

“We’ve had so many destructive fires in recent years that Cal Fire has really been working overtime to track what’s going on across the state: which homes burn and which homes don’t,” she said. “And the pattern starting to emerge is that when whole neighborhoods are built to these higher standards, they’re so much more resilient that they essentially function as this barrier to the advance of fire.”

On Thursday, a day after the fire torched large swaths of the canyon, a gray haze hung over the charred hillside as residents returned to the community of Coronado Pointe.

As a firefighter trained his hose on the burnt remains of what had been a stately home in the gated enclave overlooking the canyon, 20-year resident Aimee Larr stepped out of her SUV and walked hesitantly to a string of yellow safety tape. She recognized the stone fountain in the frontyard.


“This was my house!” Larr said, voice trembling with emotion. “I can’t believe this. It’s completely leveled. Nothing is left.”

She recalled how Orange County Sheriff’s deputies called for neighbors to come out of their homes on Wednesday. Dressed in just sweatpants and a T-shirt, Larr left without medication or personal mementos.

When she returned Thursday afternoon, she held out hope that her house survived. After all, it was several thousand feet from the original blaze and the canyon her home overlooked was equipped with a sprinkler system that kept vegetation well-watered and green.

“I don’t know how fast it came to my house,” she said. “It was on the other side of the canyon, that’s why I had no big concern. I thought [firefighters] would drop something on it and it would be done.”

As of Thursday evening, the fire was 200 acres with 15% containment. Its cause remained under investigation, but Southern California Edison issued an initial report to state regulators saying that it had logged “circuit activity” around the time the fire started.


(Times staff photographer Raul Roa and staff writer Luke Money contributed to this report.)

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