How likely is your home to burn in wildifre? New scale rates the risk

How likely is your home to burn in wildifre? New scale rates the risk

18 November 2013

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USA — As winter’s snowflakes start falling on the scorched hillsides above Lolo Creek, researchers around the nation are pondering how they might prevent the kinds of disaster that burned five homes there last August.

But it probably won’t involve putting out the wildfire.

“This is not a new issue, but it does come home to roost when you have a fire like Lolo Creek,” said Ted Mead, chief of fire and aviation management for the Montana Department of Natural Resources and Conservation. “That’s a teachable moment. We recognize that first short period, that first six months is the most opportune time to work with property owners and help them understand what they can do to mitigate risk.”

That’s because research indicates fighting wildfires and saving homes are two separate things, even if the struggle takes place in the same forest. The retardant-dropping planes and yellow-shirted ground crews can reduce how many acres a forest fire blackens. But the homes lost in Lolo Creek, as well as the hundreds that burned in Colorado’s wildland-urban interface last summer, usually face a very different threat.

It’s common to assume the walls of flame under a towering smoke column pose the biggest threat in a wildfire, said Jack Cohen, a scientist at the Rocky Mountain Research Station in Missoula. That’s true for people, but not for houses.

“The same heat radiation that on my exposed skin will give me a second-degree burn in 5 seconds, takes 27 minutes to ignite wood,” Cohen said. “Firefighters are way more vulnerable to big flames than a house is. That tends to skew what we pay attention to.”

In most of the lost-house incidents he has studied, Cohen found the residential destruction took place eight to 10 hours after the big flame front moved through. That’s when embers finally ignited piles of pine needles in a rain gutter, or leftover lumber under a deck, and eventually burned the house down.

“Unless houses are mitigated to be ignition-resistant, firefighters can’t be effective in well-developed residential areas,” Cohen said. “There aren’t enough firefighters and resources to assist and suppress ignitions on all houses exposed.”


Several new tools have appeared in the past year that may make the homes lost in Lolo Creek less common. A fire hazard scale ( developed by the National Institute of Standards and Technology and U.S. Forest Service can suggest changes in building codes similar to how the Richter Scale defines risk in an earthquake region.

Last month, a task force gathered by Colorado Gov. John Hickenlooper proposed a way to rank homes based on fire risk. Montana Building Association government affairs specialist Dustin Stewart attended the conference where it was unveiled.

“Every home would be given a grade on a sliding scale from 1 to 10 to determine its susceptibility to wildland fire,” Stewart said. “It’s not entirely clear who would use the grade. Insurance companies could potentially use it when developing policies for wildfire. Or it could trigger a mandatory fire mitigation for those homes with high grades.”

Stewart said the Colorado Homebuilders Association members he talked with were not in favor of the plan, warning it could “hang a scarlet letter on the house.”

“It could severely impact resale value,” he said. “And it becomes very politically unpopular when you tell 10,000 residents across the state they have to disclose this number when they sell their house.”

Colorado and several other states have developed systems that use public data like aerial photos to rank house-wildfire risks. In Montana, Cohen has developed a different system that requires a different social approach.

The “Wildfire Wizard” program assesses the likelihood of a home burning down when – not if – a wildfire ember hits it. Cohen said one of its assumptions is that big forest fires will continue to outrun the firefighters confronting them.

“We’re talking about situations where wildland fire suppression and structure protection were totally overwhelmed,” Cohen said of the incidents he used to build the model. “Times where you may have a few tactical successes, but strategically, fire protection fails and more than 100 houses burn down. What’s the unassisted potential for this house to survive or fail?”

The Lolo Creek and West Mullan fires last summer matched those criteria – incidents that took off so quickly responders could do little but get out of the way. In Lolo Creek, five homes burned in the first chaotic day.

The Wildfire Wizard can be used before, during and after such fires. Its principles helped structure protection crews save several houses on the Lolo Creek fire’s second day, when embers floated for miles along Highway 12 and ignited barrow pits and hillsides far from the main fire boundary. Municipal fire crews went house-to-house dousing embers on decks and under porches.


But the Wildfire Wizard requires much more than an aerial-photo overview to make an advanced assessment. It needs at least 20 minutes with an experienced auditor on the property – and that brings a whole different element into play.

“The ignition zone is usually on private property, and that changes the social dynamics,” Cohen said. “We don’t have the authority to go in and tell people to make changes or to make changes ourselves. We have to have homeowner agreement, engagement and participation in reducing their vulnerability.”

In other words, labeling people from space won’t save any houses next summer. Stewart, at the Montana Homebuilders Association, had a similar observation.

“I think incidents like Hurricane Sandy, the Oklahoma tornadoes, the wildfires in Colorado – they’re going to become a bigger part of the public discussion in new construction standards,” Stewart said. “But there are things people can do without creating another level of government. That’s a nice thing about living in Montana. We don’t need to reinvent the wheel every time there’s a storm or fire. We can find a solution that isn’t heavy handed and gets the job done. There may be a big national debate, but the tenor is different as a result of where we live. It would help everyone if a few more homeowners would take care of a few simple things on the to-do list before we enter that debate.”

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