Data may be Colorado’s best bet to mitigate increasing wildfire risk on the Front Range

By Michael Booth, The Colorado Sun and John Upton, Climate Central

Grass fires have threatened the meadows and homes near Chatridge Court and U.S. 85 three times in five years, and firefighters work hard to keep flames from moving over the hill into thousands of homes in Highlands Ranch. (Photo from the 2016 Chatridge fire. Credit: South Metro Fire Rescue)

DOUGLAS COUNTY — The future of climate change and suburban firefighting in Colorado is here, in a dull brown meadow at the corner of Chatridge Court and U.S. 85. 

They know the future will arrive on this spot, because the kind of raging grass fires near thousands of suburban homes that keep emergency planners awake at night has already been here three times in five years.

The Chatridge 3 grass fire on Dec. 14, just before Boulder County’s horrific Marshall fire, swept east up the hill from U.S. 85 toward an isolated mansion and threatened 100,000 people in Highlands Ranch, a few miles away. 

Ruth lives in that mansion at the top of the hill, with her husband, where they’ve seen all three Chatridge grass fires. In December, it was just another beautiful day to enjoy the stunning 360-degree views from her upstairs windows, until the police knocked. Again. 

“We didn’t know why they were here until we looked down to our yard, and the firefighters were already there,” said Ruth, who asked that her last name not be used. A rancher usually brings cattle to keep the grass down between their house and the highway, but the animals hadn’t arrived yet to do their job. The pasture was flaming. Scorched roots of scraped-up yucca plants dot the ground.

“They evacuated us. When we came back, we didn’t know if we’d have a house left or not,” Ruth said. “But we did.”

Grass fires have threatened the meadows and homes near Chatridge Court and U.S. 85 three times in five years, and firefighters work hard to keep flames from moving over the hill into thousands of homes in Highlands Ranch. (Photo from the 2020 Chatridge 2 fire. Credit: South Metro Fire Rescue)

The weather that day was dry, warm and windy — fire weather, the increasingly familiar conditions that can blow small fires quickly into infernos. South Metro Fire Rescue knew soil there was historically dry – a worry confirmed by detailed new satellite data from a Boulder firm that wants to reach out to Front Range firefighters. Just 16 days later and 45 miles away, fire weather would stoke the Marshall fire.

As heat-trapping pollution pushes up temperatures, the region that’s home to the state’s largest cities has seen one of the nation’s sharpest increases in the frequency of fire weather. Climate and fire experts say they must now do even more to layer new sensor technology atop decades of firefighting experience to prevent fires like the one that devastated Louisville and Superior.

New data resources for prevention

An analysis of weather data shows the region, known as Colorado’s Platte Drainage Basin, is experiencing fire weather nearly 40 days a year on average now, up from fewer than 20 days annually in the 1970s. The increase is steepest during the winter months.

“When I look at that climatology change, it lines up exactly with the amount of large historical fires that South Metro has specifically had. We saw an uptick in the size and intensity of wildland urban interface fires,” department spokesman Eric Hurst said. 

“The fires tend to be more intense and grow faster than they used to.”

Firefighters were overwhelmed by the speed and intensity of the Marshall fire, which destroyed more than 1,000 homes in just a few hours. 

Grass fires have threatened the meadows and homes near Chatridge Court and U.S. 85 three times in five years, and firefighters work hard to keep flames from moving over the hill into thousands of homes in Highlands Ranch. (Photos from the 2020 Chatridge 2 fire. Credit: South Metro Fire Rescue)

Landscaping including bushes and lawns growing alongside houses and roadways were parched by the dry and windy weather and by the shortage of snow and rain in the months beforehand. That provided an abundance of kindling for the flames, which were carried swiftly from one block to another by the fierce seasonal gusts. 

But the inferno’s rapid spread didn’t surprise planners in departments from Larimer County to Colorado Springs. They are watching fall snow disappear, and open space soils grow desiccated. They see extreme heat season expanding. 

And they are trying to prepare. 

How firefighting can adapt

South Metro dreams of acquiring its own road graders to supplement those owned by Douglas County. A satellite data company executive whose own home was ruined by smoke from the Marshall fire pictures fleets of suburban brushcutters ready to trim fire breaks on red flag days. Colorado Springs scrambles to warn a constant turnover of new homeowners in its military-transient community of new urban interface fire dangers.

While some years still bring good snow cover as a fire deterrent in November and December, said Colorado State University climatologist Peter Goble, “the dry years hurt more with warmer conditions.” While much of the western half of Colorado is in a 20-year drought, average statewide temperatures in the last six months of 2021 were the hottest ever recorded. Denver set a record in 2021 for the number of days between the last spring and the first winter snowfall.

Not only are suburban grass fires threatening in mid-winter, but recent years have brought grass fires on the Eastern Plains before plants there have the chance to green up, Goble said. 

Front Range fire planners and civic leaders have to now contend with far more fire danger days under climate change than in past decades, with chances for damaging events like the Marshall fire ever more present in the suburbs.

“It’s made me wonder if maybe we’ve been a little bit lucky that we haven’t had more of these brush fire incidents closer to urban centers before,” he said. 

Dazed by the fury of the flames in their neighborhoods on the border between open space and town centers, homeowners and elected leaders on the Front Range are reassessing their disaster priorities. 

David Gross spent 30 years planting shrubs and trees to slowly transform his Louisville home south of Harper Lake into his version of paradise, just across McCaslin Boulevard from the city’s Davidson Mesa open space. He was away on vacation at the end of December when the Marshall fire torched his house and his illusions of relative security.

 “Never in a million years,” would he have imagined a foothills wildfire arriving at his doorstep, Gross said. “We were certainly far away enough that I never would have imagined this. Let alone on Dec. 30.” 

Remains of burnt yucca plants near U.S. 85 and Chatridge Court. Credit: Olivia Sun,
The Colorado Sun

Homes at U.S. 85 and Chatfield Court on Jan. 20, about a month after a wildland fire. Credit: Olivia Sun, The Colorado Sun

Louisville Mayor Ashley Stolzmann said city firefighters keep bringing up the fact that the fire jumped a six-lane highway next to a two-lane concrete road — “that’s a pretty big fire break,” she said. “This just jumped right over, like nothing.”

Until now, Stolzmann said, Louisville has worried much more about flooding from the seasonally expansive creeks that shoot down the canyons from the high country. Grassland fire, she said, is “certainly something we’ll be thinking about now.”

“The reality is, when we do have a wildfire event, each individual home is not going to have a fire truck sitting in its driveway,” said Ashley Whitworth, wildfire mitigation administrator for the Colorado Springs Fire Department. What planners keep researching, Whitworth said, is “anything that a homeowner can do on the front end to help firefighters help their home give it that chance of survivability.”

David Gross, who lived in a neighborhood south of Harper Lake in Louisville for 30 years, surveys the damage to his home on Jan. 1, after the Marshall fire. Credit: Steve Peterson, Special to The Colorado Sun

Doubling down on looking ahead

The fire departments, government agencies and homeowner associations bent on defending against suburban  grass fires are now doubling down on the kind of climate change analysis they’d begun before a December fire exploded into the most destructive in Colorado history. 

Urban development is increasing fire risks while climate change is boosting droughts by sucking moisture from plants and soils, which is causing Western forests and grasslands to burn more frequently and intensely. The rising temperatures are also increasing the frequency with which fire weather strikes. (Changes in how forests and other lands are managed are also affecting fires; so, too, is the spread of invasive plants and tree damage caused by beetles.)

Climate Central analyzed data from federal weather stations operating since the early 1970s to investigate fire weather trends. Climate Central based its definition of fire weather on criteria developed by NOAA’s Storm Prediction Center for elevated fire weather forecasts. To count as fire weather, thresholds set by the federal government must be met for a certain number of hours each day for temperature, relative humidity and wind speeds, with thresholds varying from one region to another.

Front Range fire planners and civic leaders have to now contend with far more fire danger days under climate change than in past decades, with chances for damaging events like the Marshall fire ever more present in the suburbs. (Climate Central)

The analysis revealed sharp increases across the Western U.S. of occurrences of fire weather, with modest increases in temperature playing outsized effects on dryness. When the Chatridge 3 and Marshall fires broke out, the region’s powerful yet natural winds were strong enough locally to satisfy the conditions for fire weather. So, too, were relative humidity and temperature.

During the Marshall fire, the winds were “particularly violent, but they were where and when you’d expect them to appear,” said Daniel Swain, a climate scientist based in Boulder whose affiliations include UCLA and the National Center for Atmospheric Research. Swain advised Climate Central on its fire weather analysis.

There was no official red flag warning banning open burns the day of the Marshall fire, though other burn bans were in place. The National Weather Service’s Boulder office is now reviewing whether its standards should change for issuing red flag warnings, which may carry more weight with the public than other no-burn notices. 

That the winds blew embers through suburban vegetation that was parched and dry just one day before the region’s first major snowfall of the fall or winter might just have been “bad luck,” Swain said.

The effects of those winds in spreading the Marshall fire, however, highlighted that the same climate change influences that are worsening forest fire risks can also lead to suburban wildfires igniting scrub vegetation first, then taller grass, and then moving on to ignite fences, rooftops and then entire homes and blocks. 

“While the Marshall fire wasn’t really a traditional wildfire, in the sense that much of what it burned were highly populated suburbs rather than just vegetation, it turns out the climate conditions leading up to the event were still important,” Swain said.

More “fire weather” days

An analysis of fire weather trends from the region including Denver and Boulder from December through February shows fire weather remains far rarer then than during summer months, but the frequency is increasing at a faster pace — roughly five days per winter now on average, up from an average of about one in the early 1970s.

Kevin Petty watched Front Range soils dry out in November and December in his work as a vice president at Spire Global, which uses data collected from low-orbit satellites to understand the impacts of extreme weather. In January, he has been trying to figure out how to get more of his company’s weather and climate data to civic leaders, while he tallies near-total smoke damage to his Louisville home from the Marshall fire.

Satellite collection of sensor data shows how dry soils have been on the Front Range in recent years, including in November and December when suburban grassland fires have grown more dangerous. Credit: Spire

The day Petty talked to The Sun about Spire’s identification of historic levels of soil dryness in late 2021, he was also fielding phone calls from his daughter looking for a smoke-free dress for an honor society induction. He had never before had to think of his family as a victim of natural disasters, Petty said. 

“Now, allowing people to make better decisions about what to do in these situations is even more near and dear to me,” he said. “We want to live in a great state, and we want to see the natural beauty. But when you have a population that’s growing, and houses being built close together, you have to take certain mitigation actions.”

Similar to NASA soil moisture missions, Spire satellites indicate surface moisture levels falling steeply below the historic mean in November and December. From the foothills of Larimer, Boulder, Jefferson and El Paso counties and heading east, soil moisture in late 2021 flares an angry, subnormal red on Spire generated maps. 

Spire’s hourly forecasts on Dec. 30 also had Petty on the edge of his seat. “I was actually praying for the sun to go down, because I knew our forecasts were showing a decrease in wind speeds at sunset, and that was going to help these firefighters fight the fire.”

The company is reaching out to local weather and fire agencies to offer partnership in information, Petty said. Satellites have useful environmental data, but researchers haven’t perfected conveying those risks to civic planners or the public. 

“To take the appropriate actions at the right time – that’s something in the scientific community that we haven’t necessarily focused on quite as much,” Petty said.

High winds grounded any aerial firefighting or prevention that day, Petty noted. But with more advanced data on local climate conditions, like dry soil or potential fuels, planners could do more in grassland areas previously thought safer than forests. They could mow ultra-dry grass and weeds in more open space buffers during droughts, or have more cutters and bulldozers available for making firebreaks “in real time.” 

A meadow at Chatridge Court and U.S. 85 has burned three times in five years, threatening hilltop mansions and thousands of homes over a ridge in Highlands Ranch. (Photo of firefighting efforts were taken on Dec. 14. Credit: South Metro Fire Rescue)

Other civic agencies already do this, drawing on information from Spire and other data companies, he said. An airport or highway department looks at precise weather reports to schedule snowplow drivers and other crews for maximum impact. 

“You can figure out the same in terms of fighting and mitigating fire hazards,” he said. 

South Metro Fire, whose map straddles C-470 and takes in thousands of acres where grassland and suburbs meet, from the foothills to the prairie east of Parker, is trying to think ahead in that way. 

South Metro looks at long-range historical data showing the Front Range climate in their service area to be warmer and wetter to the east of Interstate 25, but warmer and drier than normal in the southwest metro area, Hurst said. That trend fits “exactly” with the uptick in grass and brush fires the department has fought since the massive Hayman fire in 2002 first alerted southwest metro counties that they were in a new era, Hurst said. 

The department watches National Weather Service red flag warnings carefully, he said, but also adds in other criteria they find relevant in its suburban territory. South Metro’s planning “recipe,” Hurst said, adds in a burn index, fuel moisture levels and “energy-release components” – “things that are a bit more into the weeds of the weeds, so to speak.” 

On a normal day in a relatively wet year, Hurst said, when a 911 caller reports vegetation fire of less than an acre, one wildland fire engine, one structural fire engine and a chief officer and safety officer are dispatched. That team is about 10 people. 

“On a day that South Metro has identified as high risk, we triple that response of firefighters, immediately,” he said. “It’s a conversation that happens around 6:30 every morning.” 

Douglas County and Highlands Ranch, among others, work with South Metro to identify high-risk grassy areas and keep as much mowed during high risk times as possible. When flame height or length reaches 4 feet from waist- or chest-high grass, firefighters can no longer attack it directly, Hurst noted. 

But firefighters wishing all grass was an inch high doesn’t match up with what the public wants, Hurst said. “We know that’s unlikely.”

Ground zero at Chatridge Court

The Dec. 14 fire at Chatridge in South Metro was 24 acres. The previous fires on the same spot were 461 acres and 205 acres, both of them breaking out when fire weather was detected by nearby weather stations, and the 2020 edition prompted evacuation of 1,000 homes in Highlands Ranch. Just to the south, the Cherokee Ranch fire in 2003 burned 1,000 acres. South Metro now develops detailed maps of such wildland high-risk spots, with bird’s eye views of terrain and structures. The terrain is graded to show what fire behavior and movement is likely, and access points and structure evacuations are marked. 

The firefighters’ ideal of a home in such areas is “standalone,” like the mansion that sits on Chatridge Court in the middle of a thrice-burned pasture. The homeowners had cut grass and avoided any tall shrubs around their property, Hurst said. But of course Highlands Ranch and other more dense neighborhoods will never be like that. 

Residences at U.S. 85 and Chatridge Court photographed on Jan 20. The Chatridge 3 grass fire on Dec. 14 swept east up the hill from U.S. 85, potentially threatening 100,000 people near Highlands Ranch before being contained. Credit: Olivia Sun, The Colorado Sun

What department outreach staff tell homeowner associations in vulnerable areas is to defend themselves with simple tasks, like cleaning leaves and pine needles out of their gutters and off their decks. Avoid landscaping with 12-foot-tall plume grass that grows to the eaves and dries to a crisp in September. 

“We try to describe to them what an ember shower is going to look like,” Hurst said. Websites like Firewise describe safe landscaping down to the leaf type.

What South Metro firefighters wish for is more road graders and bulldozers. Douglas and Arapahoe County offer access to their road equipment and skilled operators, Hurst said, “but not all fires are created equally, and being able to get those in the right spot at the right time is a challenge.” 

California towns keep more aerial and road building equipment on site, and local Colorado departments will likely seek those kinds of resources, he said. 

What keeps Colorado Springs awake

Similar interface areas have been an intensive focus of Colorado Springs fire planners for years now, since their own terrifying events. 

The wildland urban interface for sprawling Colorado Springs stretches from the Air Force Academy on the north to Cheyenne Mountain on the south, running through densely populated neighborhoods near Garden of the Gods and the Mountain Shadows area, burned by the Waldo Canyon fire, said Whitworth, the mitigation expert for the city. The steep firefighting terrain of Cheyenne Mountain State Park runs right down into the forested homes around the Broadmoor. 

“It all keeps me up, to be honest with you,” Whitworth said. 

Whitworth takes daily state fire danger bulletins and adds local emphasis on cloud cover, relative humidity, expected temperatures and fuel moisture. The longer-term work, such as homeowner education and building-code changes, is meant to make incident commanders’ jobs easier. 

The Waldo Canyon fire burned 347 homes in 2012, the most notorious loss in Colorado until the Marshall fire knocked it down the list. Before Waldo Canyon, the fire department worked with 63 neighborhoods on education and preparation. Today, it works with 142 neighborhoods. 

The help includes an offer of a free walkaround for homeowners with a city mitigation specialist. Homeowners on designated days can clear and stack brush from scrub oak and junipers, and the city chips and hauls it away for free. 

Post-Waldo Canyon, firefighters went to city council and sought codes requiring rebuilding or new building in interface areas with ignition-resistant material, like stucco or cement fiberboard. Decking must be composite, instead of wood. Hazardous vegetation needs to be at least 15 feet from the home.

The educators don’t take winters off. 

“People think, oh, December, January, nothing is going to happen. But some of the most deadly fires in Colorado have happened in winter months,” Whitworth said. “So we are constantly educating. Twelve months of the year.”

El Paso County’s large military presence – the Air Force Academy, Fort Carson, Peterson and Schriever Air Force bases and other facilities – increases the need for round-the-calendar education. “We get a lot of turnover in homeownership and renters,” she said. 

Spark to ember to flaming, flying chunks

Independent wildfire investigators are sifting through damage in Louisville and Superior to deepen their research and spread the results as far as possible. The Insurance Institute for Business and Home Safety, a nonprofit trade group, combines notes from its field researchers with results from a lab where it can subject home materials and landscape to embers blown on 100 mile per hour winds, and other threats.

Burning particles of grass at the front edge of a fire usually travel only 60 or 70 feet before they cool off, the IBHS Marshall fire investigators said. But those grasses in Boulder County were being driven much farther by the hurricane-force winds that day. And the grasses were within a few feet of many structures.

Once smaller grass embers hit wood fences, chunky landscape mulch, and the houses themselves, then bigger embers start flying and igniting the next structure, said IBHS engineer Faraz Hedayati. 

Once an entire house is on fire amid furious winds, larger and larger embers can skip hundreds of feet across roads and other perceived firebreaks. At the Marshall site, the investigators found downwind homes burned with all the other structures around them still intact, a sign of those flaming chunks hopscotching large distances. 

Under those conditions, said IBHS investigator Daniel Gorham, an engineer and former firefighter, federal designations of which neighborhood is in a wildland interface and which isn’t suddenly disappear. As does the perceived security of sitting on the east side of a six-lane concrete highway.

“It’s oftentimes not a clear line in the sand,” Gorham said. 

Individual homeowners increasingly worried about the vulnerability of their neighborhoods can consider practical steps, the investigators said. Those include adding noncombustible siding, keeping wooden fences detached from the home itself, using double-pane windows, and keeping volatile landscaping 5 feet from the house. Yard sheds often burn first, and may contain accelerants like lawnmower gas or sawdust, they noted. 

As a group, neighbors can help out homeowners who haven’t been able to take basic steps like clearing gutters or cutting back landscape plants, they said. Neighbors should look at the Marshall fire and realize the source of their potential fire might be coming from a roof burning next door. 

At the community level, the insurance investigators said, solutions to climate change layered on top of suburban realities are less clear. 

“Maybe it’s fuel modification,” Gorham said. “Maybe it’s not mowing all the grass but maybe strategically mowing it, such that if there’s a fire that spreads into there, the intensity is reduced.”

Fire investigators will continue digging into the Marshall and other fires at the urban interface for messages they can send to communities and emergency planners. Much like the Marshall fire victims who are rethinking their ideal landscape, though, Colorado’s Front Range communities will have to reconsider their sense of place. 

“The balancing of wanting to live in a place that you want to live, and have it look the way you want it to look, with the reality of the potential for wildfire . . . “ Gorham said. “I don’t have the answer for that.” 

High atop Chatridge Court near Highlands Ranch, Ruth and her family don’t attribute their frequency of fire to climate change. They’re used to it being bone dry in December, and people make mistakes and start fire, she said. They keep the brush cleared outside their fence, as firefighters have advised, welcome the hungry cows, and know it can happen again. 

She thinks neighbors atop the hill, also in big houses, across wide stretches of former pasture, also try hard to build their own versions of a firebreak.

“I think everybody’s doing as good a job as you can expect, living in a rural area,” she said, waving again at the view plans north to Highlands Ranch and west to the Rampart Range. 

“This is why we love it out here,” she said. “Rural. But close to everything.” 

It’s a wet heat . . . or a dry snow . . .

Weather, climate and fire watcher Peter Goble has a complicated phrase he thinks Coloradans might want to learn: Standardized Precipitation Evapotranspiration Index. 

But there’s a simpler way to think of it: Rain + Snow – Water lost to heat = Danger level. 

While Coloradans keep hearing about historic drought and temperature levels, Goble, who watches the climate from the Colorado State University climatology center, said we actually aren’t doing that badly lately on rain and snowfall. He offers this chart of precipitation in recent years – at a glance, green years are good, brown years are bad: 

Watching fire danger means not just counting snowfall, but also account for how fast hotter climate change temperatures burn up the moisture. This graphic shows how precipitation has seen fairly normal fluctuation in recent years. The next chart shows how fast it has dried up in recent drought years. Credit: Peter Goble, Colorado State University

“And it’s remained just highly variable over time,” Goble said. 

Now, add in the higher temperatures from global warming, which is impacting the western United States and Colorado in particular at a faster rate than the rest of the nation. The wetter years don’t help nearly as much if scorching hot days are sucking all the moisture out of the grown and out of river watersheds. Here’s what that more ominous evapotransipiration chart looks like for Colorado:

Watching fire danger means not just counting snowfall, but also account for how fast hotter climate change temperatures burn up the moisture. This graphic shows how precipitation has dried up quickly in recent drought years. Credit: Peter Goble, Colorado State University

The last 20 years have been awful, frankly. And that’s one major contributor to the high fire danger in both mountainous areas and in the grassy, wildland urban interface areas that burned so disastrously at the Marshall fire and other Front Range locations. 

“It shows how even if you don’t have a trend in precipitation, if you take into account the changes in temperature when looking at our overall water story, it makes a big difference,” Goble said.