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. These photos are from the 2016 Chatridge fire. (South Metro Fire Rescue file photos)

Colorado faces the largest increase in homes and businesses threatened by wildfire of any state in the nation with nearly 1 million properties — two-fifths of all those in the state — already facing some risk, according to a new analysis.

The First Street Foundation wildfire risk modeling ranked Colorado No. 7 in the country for structures facing wildfire threats. The foundation also created an online tool — — that enables homeowners to plug in an address and find the fire risk for their properties.

Over the next 30 years, the model projects that an additional 447,000 homes, businesses, schools and other public buildings in the state will face an increased risk from wildfire — a 19% increase from today. Alabama had the next largest increase in risk, 14.6%.

The area with the greatest wildfire property risk is not Colorado’s forested region, but the Front Range’s growing suburban plains countiesEl Paso, Douglas and Larimer, according to the analysis.

“If you think about it, that’s where the people are and where there are people there is more risk of someone starting a fire,” said Chad Hoffman, director of the Western Forest Fire Research Center at Colorado State University. Hoffman was not involved in the foundation’s analysis.

That is also where most of the homes and businesses are located — potential fuel for a fast-moving fire, Hoffman said.

The archetype for future fire risk could be the Marshall fire, a one-day, grass-fed, wind-whipped wildfire on Dec. 30 that destroyed more than 1,000 homes in Boulder County.

“Those kinds of fires are clearly becoming more common,” Hoffman said. “These single-day burning periods create a problem.”

While much of the focus has been on the large-scale, intense forest fires that burn for weeks or more, a study by Hoffman and colleagues found that 70% of cumulative area burned in the Western U.S. between 2002 and 2020 were the result of the large, single-day fires.

The First Street analysis looked at the marginal risk of wildfire, with minor risk being less than a 1% chance of being in a wildfire over the next 30 years to extreme risk, defined as a greater than a 26% chance. Annual risk assessment started a 0.03% increased risk for any given year.

In El Paso and Douglas counties, more than 80% of the homes and business properties face a minor risk of being in a wildfire this year — 32,000 and 4,000 properties respectively. In El Paso County, 32,100 properties also face a moderate risk of fire — equal to a 6% chance.

Larimer County ranked third with a little more than half of homes, businesses and public buildings — 82,000 properties — at minor risk and 4,000 facing moderate risk.

The county facing the greatest increased risk from wildfire is Broomfield, where over 30 years, the number of properties that will face some additional fire hazard risk rises 48% to 20,400 — equal to more than three-quarters of all the county’s homes, and business and public buildings.

The foundation’s model incorporates data on formation of fuels, wildfire weather and wildfire behavior from agencies, including the U.S. Forest Service and the National Oceanic and Atmospheric Administration.

The First Street Foundation is a Brooklyn, N.Y.-based nonprofit research and technology group focused on defining climate risk in the U.S.

Across the country there were 49.4 million properties with at least minor wildfire risk, led by California, Texas and Florida. There were 4.2 million properties facing severe or extreme risk from fire.

“Enhanced understanding of the specific nature and location of wildfire risk enables communities to more effectively lobby for funding for fuel treatments, prescribed burns and other  wildfire risk mitigation strategies that may be used to reduce risk to houses, business and communities,” the foundation said in a statement.

Special to The Colorado Sun Twitter: @bymarkjaffe