More homes are being built in high-risk wildfire areas, a zone referred to as wildland/urban interface (WUI). Fire managers from the Boise National Forest say defending structures changes their game plan on draws more resources.

More homes are being built in high-risk wildfire areas, a zone referred to as wildland/urban interface (WUI). Fire managers from the Boise National Forest say defending structures changes their game plan on draws more resources. By Darin Oswald

When wildfires burn in Idaho, they’re difficult to ignore. Smog pools in the Treasure Valley, roads and trails are closed, and columns of thick smoke can be seen from miles away. Landscapes are altered for years, dotted with charred trees and aptly named burn scars.

Still, with the exception of those fighting the fires, many Idahoans don’t see the flames up close or feel their heat.

As wildfires across the West have killed dozens and burned entire towns to the ground in recent years, Idaho has largely been spared. Evacuations aren’t uncommon, but it’s been years since an Idaho wildfire destroyed homes on a large scale, and even longer since any Idaho residents lost their lives to wildfire.

A swiftly growing population and sprawling development are putting Idaho — and the Treasure Valley in particular — at an ever-growing risk of catastrophic wildfire.

>> Idaho has avoided tragedy, but it’s largely due to luck

Idaho’s history with wildfires started in rough fashion. The Big Burn, a 1910 fire in North Idaho that charred 3 million acres, killed dozens and wiped out several towns. Few, if any, comprehensive records exist to detail the total wildfire death toll and property damage in the century since.

The last decades have offered a few notable examples — the 2008 Oregon Trail Fire that destroyed 10 homes and killed one woman in southeast Boise, the 2012 Charlotte Fire in Pocatello that torched 66 homes and the 2016 Table Rock Fire that burned one Foothills home and threatened more.

Idaho’s damage has paled in comparison to the rest of the West. Last year alone, fires in California destroyed more than 8,600 homes. In Oregon, Washington and California, more than 30 people were killed by wildfires in 2020. And while entire towns like Talent, Ore., and Paradise, Calif., have been reduced to rubble in recent years amid record-setting fire seasons, Idaho has experienced fairly mild years, thanks to lucky combinations of fuel loads, ignitions and numerous other factors.

Idaho’s relatively sparse population has played a role in its smaller loss of life and property. Though Idaho often boasts some of the highest-acreage wildfire seasons in the country, many of those blazes are on rangeland or in forests with no inhabitants.

That could soon change. The 2021 wildfire season has the potential to be brutal, with widespread drought in the West rapidly expanding. What’s more, a recent study found that fires are burning places they haven’t before, reaching higher altitudes once too cold or wet. One of the study’s co-authors, Boise State University assistant professor of civil engineering Moji Sadegh, said fires are now threatening some mountain towns that haven’t been at risk.

Sadegh also said Idaho’s growing population is leading to more human-caused ignitions, which bring wildfires closer to residential areas much more frequently than fires ignited by lightning, vehicles or other sources.

“We are putting more houses in the fire danger zone, and we are increasing the fire danger — not necessarily by drying but by providing more ignitions,” Sadegh said. “The problem with growth is humans provide sources of ignition.”

>> Treasure Valley homes expanding into high-risk wildfire zones

Maps of wildfire risk areas show development in the Boise region and other parts of Idaho has expanded more and more into what’s known as wildland-urban interface areas — the less densely populated outer limits of towns and cities where structures meet with forest or range.

It’s difficult to precisely match up Idaho’s rapid development with wildfire risk. A comparison of a U.S. Forest Service wildfire risk map with Google Satellite images shows growth in the Boise Foothills, southwest Ada County and parts of Boise County into areas classified as the highest or second-highest wildfire risk areas.

“If you think about the city as a whole, a lot of our urbanized area have little opportunity for infill,” said Capt. Jerry McAdams, wildfire mitigation specialist with the Boise Fire Department. “So as we continue to expand, with the idea that Boise is one of the fastest-growing cities (in the country) ... it makes sense that we’re going to expand into wildland-urban interface areas.”

The Forest Service found that “populated areas in Idaho have, on average, greater risk than 94 percent of states in the U.S.” Nearly the entire wildfire risk map shows Idaho at some level of fire danger. Central and Southwest Idaho are tinged the deepest shade of red on the agency’s map — the highest wildfire risk level, reserved for parts of Southern California and deserts in Nevada, Arizona and New Mexico.

“There are not very many places in the state of Idaho that I wouldn’t consider at risk from the impacts of wildland fire, whether that be from smoke or from embers, or from truly being directly impinged upon by a flame,” said Tyre Holfeltz, wildfire risk mitigation program manager for the Idaho Department of Lands.

While the innermost parts of the Treasure Valley along the Boise River are considered lower-risk areas, according to the Forest Service map, most of Southern Idaho is at high risk for wildfire.

“In Southwest Idaho, since mostly we have shrublands ... the fire risk is always high,” Sadegh said. “Driving to Bogus Basin, you can see houses are popping up at a high rate. A lot of these houses ... the view is beautiful, they get a feeling of living in nature, but it’s a fire zone. It’s not a matter of if (the area will burn), it’s a matter of when.”

Sadegh said Idaho is “following the path that California walked a couple of decades ago.” He said development in the Foothills mirrors California’s expansion into wildland-urban interface areas. Investigations by the Sacramento Bee have shown the majority of deadly, destructive fires in the state have occurred in areas deemed “very high fire hazard severity zones.”

>> Boise implemented wildfire standards a decade ago. Are builders and homebuyers keeping up?

After the deadly Oregon Trail Fire in 2008 and another damaging Ada County fire the following year, officials created the Ada Fire Adapted Communities initiative. The project implemented fire codes specific to wildland-urban interface areas and created resources for homeowners, businesses and government agencies to mitigate risk.

“At the time (of the Oregon Trail Fire) we didn’t have a delineated wildland-urban interface area,” McAdams said in a phone interview. “We didn’t even think about it in that context.”

The wildland-urban interface code, which was updated this year, includes requirements for fire-resistant construction materials and vegetation management to create what’s called defensible space — a barrier of less-flammable materials around homes. The code also requires developers to create wildfire safety plans, which McAdams reviews.

McAdams said a swath of wildland-urban interface homes creates a protective ring of fire-resistant structures on the perimeter of a city, in theory stopping the spread of a wildfire that manages to reach developments.

But there are caveats. Several older neighborhoods on the edges of town — like Boise Heights and Highlands — were built decades before flame-resistant materials were required. If a fire made it there, the whole area could go up in flames quickly, McAdams said.

“If we think about the idea of having another Oregon Trail Fire where we have high winds ... you catch that first house on fire and now you have large embers from those houses landing on other houses,” McAdams said. “We definitely have the possibility here in Boise where we have a chance of losing hundreds of homes.”

Even new developments aren’t fireproof.

“Builders are still getting used to the idea,” McAdams said. “We’ve got developers that are extremely receptive and understand all the nuances (of the wildland-urban interface code), and then there’s developers that unfortunately want to cut corners, or maybe they just don’t yet understand (the importance.)”

Once homeowners move in, they can create fire risks despite a developer’s best efforts. McAdams said many people put highly flammable vegetation — such as decorative grasses, bark mulch and lavender — right alongside homes, where embers can fly under flame-resistant siding to ignite wood framing.

Holfeltz, the Department of Lands wildfire mitigation expert, said embers can travel a mile or more from a fire to ignite flammable materials. He works with agencies around the state to launch risk mitigation efforts, using grant funding to remove hazardous fuels and create defensible space in high-risk areas such as Idaho City.

In Boise, there are numerous initiatives meant to help homeowners reduce the risk of losing their homes to wildfire, but administrators say they’re underused. McAdams conducts free wildfire home safety inspections, while Boise offers programs to dispose of tree limbs or swap highly flammable plants for fire-resistant ones. Information on those programs is available at the Ada Fire Adapted website.

But even with the best preparation, there is immense risk of catastrophic wildfire, Sadegh said.

“People here are used to fire and understand it,” he said. “But as we grow, it means more and more structures are in the way of fire.”