Engineer who worked on plans for nuclear-powered airplane later developed the fire spread model

Throwback Thursday: the origin of the model for predicting the spread of wildland fires

Today we may take it for granted that tools are available that can estimate how a fire, unplanned or prescribed, will spread across a landscape. It is not an exact science because there are far too many variables than can realistically be accounted for, at least with the technology available today. But in 1972 when Dick Rothermel and others developed the Forest Service’s first quantitative, systematic tool for predicting the spread and intensity of forest fires, it introduced a new era in fire management. And surprisingly, it is still the main tool being used today. Many researchers have produced alternative models, but none have made it into the hands of firefighters on a widespread basis.

Dick Rothermel fire research Ember Award
For his research and contributions to understanding how fires spread, Dick Rothermel was given the Ember Award at caonference in Missoula in 2014. Photo by Bill Gabbert.

After Mr. Rothermel developed the mathematical model, others used the information to make the concept more user-friendly and to analyze complex scenarios. Behave, software burned onto a custom made chip in a hand-held Texas Instruments 51 calculator, and later BehavePlus for personal computers, became must-have tools for fire behavior analysts. FARSITE added the ability to predict spread across variable terrain, vegetation, and weather. Rare Event Risk Assessment Process (RERAP) estimates the risk that a fire will reach a particular place before it dies. FireStem estimates tree mortality based on fire behavior and intensity. And there are many others.

When Mr. Rothermel began researching the behavior of wildland fires, he had just been downsized from a shuttered Department of Defense program that had been attempting to develop a nuclear-powered airplane.

Below is an excerpt from an excellent article by Gail Wells for the March, 2008 edition of Fire Science Digest, a publication of the Joint Fire Science Program.

[Jack] Barrows, [the first director of the fire laboratory in Missoula when it opened in 1960], went looking for researchers. He learned that General Electric was closing a laboratory in Idaho Falls where engineers had been working on a defense project to develop a nuclear-powered airplane. The government scrapped the program in 1961, and a handful of highly trained engineers and scientists were suddenly up for grabs.

“GE wanted to see that we got as good a placement as we could,” Rothermel recalls. “So we all wrote resumes, and Jack got hold of these, and he said it was like a Sears and Roebuck catalog of people.” Barrows hired four of the GE scientists: Hal Anderson, a physicist; Stan Hirsh, an electrical engineer; Eric Breuer, a technician; and Dick Rothermel.

Their hiring represented a departure from Forest Service custom. Up until that time, fire research had been pretty much the domain of foresters, who are used to looking at their work through the lenses of biology and silviculture. Gisborne was a forester; Barrows was a forester. But Barrows recognized that fire is a physical process, and that physical scientists and engineers could contribute much to the emerging science of fire behavior.

Rothermel, then barely into his 30s, was glad to join Barrows’s staff. He had a bachelor’s degree in aeronautical engineering from the University of Washington. During the 8 years since he’d graduated, he had worked in the engineering of nuclear systems in Albuquerque and then in Idaho. (Rothermel later went on for a master’s degree in mechanical engineering from Colorado State University.)

“I had the option of staying on [at GE] and working on a lot of programs, but with the cancellation of the atomic-powered airplane, nothing sounded that appealing,” he says. “And then I heard about this laboratory, and they said they had two wind tunnels and a combustion lab where you could control the atmosphere, temperature, and humidity. I thought, “Wow, that’s an opportunity!” Rothermel worked with Hal Anderson to get the new lab’s equipment calibrated and running smoothly. Then they began a set of experiments in the wind tunnel and combustion chamber, testing the effects of wind and moisture on various fuels and determining how fast a fire would spread under different conditions.


Given their training, it made sense to Rothermel and Anderson to approach the task as an engineering problem. Says Rothermel: “The idea was, if we could develop a way of describing the fuels, the weather, the topography, and something about the fire, and be able to put that into what we call a mathematical model, and if we described all these things properly, the model would integrate it and produce answers. It would tell you the resulting fire intensity, rate of spread, flame length, these sorts of things.”

Rothermel, Anderson, and Bill Frandsen, another physicist on the project, adapted an approach developed by an early Forest Service fire researcher, Wally Fons, which turned on the concept of conservation of energy. A fire spreads by igniting a series of little fires in the fuel ahead of it. The ignitions are driven by convection, radiation, and conduction. Even if it’s unknown which mode is operating in a given instance, the rate of heat transfer can be measured. The researchers reasoned that if they knew how much fuel was ahead of a fire, how big and how densely packed the fuel particles were, and how much moisture the fuel contained, then they could figure out how much energy would be needed to transfer enough heat to bring the fuel up to the ignition point. They could then calculate the rate of ignition that would carry the fire as it spread. The model would also have to account for the critical variables of wind speed and slope of the ground.

Because of the limitations of wind tunnels and combustion chambers, the model is forced to make certain assumptions that don’t hold in real life. For example, it assumes that the fuel is continuous and evenly distributed and burns uniformly. It further assumes that the fire is carried primarily by dead plant material and that only moisture will stop it.

The Rothermel model “describes very well a fire burning in a field of wheat,” says Bret Butler, a mechanical engineer at the Fire Sciences Lab whom Rothermel hired in 1992. “As you get further away from that uniformity, the less accurate it becomes.”

More significantly, the researchers had no basis for modeling the endless spatial variability that actually exists in a forest. So there was no way to simulate a fire’s movement through clumpy, discontinuous trees and shrubs. There was also no way to model a crown fire, one that leaves the surface and moves up into the crowns of trees. These were significant and universally acknowledged shortcomings.

Fire research scientists throughout the world are working on developing more accurate surface-fire spread models, but at this point all of them are too complicated to be used in an operational system. The beauty of Rothermel’s model, says Butler, “is that it’s simple—it can be run quickly with a low-capability computer.”

(end of excerpt)

What made me think of Mr. Rothermel was a graphic distributed on Twitter today by the National Weather Service. It is a fancy, colorized version of the figure in his 1972 paper that depicts how heat is transferred in a fire.

wildfire research dick rothermel
Graphic distributed by @NWS that is based on Dick Rothermel’s 1972 paper.

But of course Mr. Rothermel’s contributions are far more complex than this graphic.

Below is a screenshot from his paper where he describes Propagating Flux, just one of many elements of his mathematical fire spread model.

rothermel propagating flux

And here is his summary of equations for the model:

Summary equations Rothermel's 1972 paper fire model
Summary of equations from Rothermel’s 1972 paper.

Epilogue 1: The current administration has expressed a desire to zero-out the budget for the Joint Fire Science Program, the organization that published the 2008 article. 

Epilogue 2: Mr. Rothermel was one of the 655 attendees at the Fire Continuum Conference in Missoula last month. 

President’s proposed FY18 wildland fire budget includes some reductions

Most wildland fire functions in Fiscal Year 2018 would remain flat or reduced a small amount if the President’s proposed budget is enacted by Congress.

Above: The President’s proposal for funding wildland fire in the U.S. Forest Service in Fiscal Year 2018. Source: USFS.

(Originally published at 5:40 p.m. MST November 9, 2017)

While the federal government keeps throwing additional billions of dollars at the Department of Defense to fund our adventures in countries on the other side of the world, the budget for the war against wildfire in our homeland would be cut in some areas while most functions would remain flat if the President’s proposed budget for Fiscal Year 2018 is approved by Congress.

In May the President proposed budgets for the Forest Service and the four primary land management agencies in the Department of the Interior: Fish and Wildlife Service, Bureau of Land Management, National Park Service, and the Bureau of Indian Affairs.  However, Congress, as usual, has not finalized appropriations bills for these agencies for Fiscal Year 2018 which started October 1, 2017. The House passed a version in September, but the Senate has yet to take meaningful action.

The agencies have been operating on a continuing resolution (CR) which expires December 8. It is likely that some kind of showdown will happen around that date, with the worst case scenario being a government shutdown. Or, they could keep passing successive CRs for the rest of the fiscal year, which would lock the funding into the FY 2017 numbers. Of course, CRs were in effect for all of FY 2017. Apparently our elected Senators and Representatives think they have better things to do than fund the government.

If Congress actually does pass a funding bill for these land management agencies, the line by line details and numbers will most likely be different from the President’s proposals, but below we spell out what the administration would like to see happen this fiscal year that started October 1.

Forest Service

In the FS as a whole, the President would like to reduce the number of employees (jobs), cutting the number of staff-years by 5.7 percent. Wildland fire personnel in the FS would remain the same — a total of 10,000, including 67 Interagency Hotshot Crews, 7,940 other firefighters, 320 Smokejumpers, and 400 Fire Prevention Technicians. Fire Suppression would be funded at the 10-year average.

The exact numbers and trends are difficult to track because the Base 8 (the first 8 hours of a firefighter’s regular work day) will now be paid out of Preparedness rather than Suppression. And funds for Hazardous Fuels are shifting from fire funding to National Forest System accounts.

In 2017 the FS reduced the number of the largest helicopters, Type 1, from 34 to 28. The President aims to retain that smaller number. Type 2 and 3 helicopters would remain the same at 33 and 46, respectively. The two water-scooping air tankers in the FS would be eliminated completely, while they add one Single Engine Air Tanker, up from zero in 2017. The FS looked at the two years they had the scoopers as an experiment, even though they have been used successfully in Canada, France, Greece, and Spain for decades.

In 2002 the FS had 44 large air tankers on exclusive use contracts. In 2017 they had 20, consisting of 16 Next Generation air tankers and 4 Legacy P2V’s. With the 50+ year old P2V’s now retired, the agency expects to have “up to 20” Next Gen air tankers in FY 2018.

The budget proposal includes funding for only one of the seven HC-130H aircraft obtained from the Coast Guard in December, 2013 that are supposedly being converted into air tankers. The one that has been used for a couple of years is still not completely transformed, and is using a borrowed pressurized Modular Airborne FireFighting System for dispensing retardant rather than employing a conventional permanent (but removable) internal gravity-powered tank.

The budget document has a rather cryptic sentence about air tankers:

Beginning in 2018, the Forest Service will transition to a full cost recovery business model for aviation utilized by cooperating agencies.

We asked a few Washington Office folks what that meant, and they either didn’t know or failed to respond to our inquiry. One person told us that unclear writing in the document could be the result of a changing of the guards and the reviewers not fully being in place at the Departments and the Office of Management and Budget.

The agency has always charged cooperating agencies for the use of FS aircraft, but it sounds like the price will increase. They may tack on in addition to the hourly rate, additional charges such as working capital fund fees that go toward purchasing replacement aircraft at the end of its life cycle.

The President wants to eliminate the agency’s $6,901,000 contribution to the Joint Fire Science Program  (JFSP) which receives its funding through the FS and the Department of the Interior (DOI). According to the budget proposal document:

The JFSP would focus on completing existing projects and standing down science exchange with managers. New research in the Smoke Management and in the Fuels Treatment lines-of-work would be eliminated, as would new research in the Emerging Management Needs initiative. General fire research in the agency would be conducted through the National Fire Plan and the Forest and Rangeland Research appropriations.

The Department of the Interior intends to cut their JFSP contribution in half, down to $3,000.

The web site for the JFSP describes their work as  “funding scientific research on wildland fires and distributing results to help policymakers, fire managers and practitioners make sound decisions”.

The total budget for all research in the FS would be cut by 16 percent, from $329 million to $276 million.

Department of the Interior

The 2018 budget request for DOI’s discretionary Department-wide Wildland Fire Management program is $873.5 million. This is a decrease of $118.3 million, or 12 percent, from FY 2017. It would mean a reduction in Full Time Equivalent employees (FTE) from 3,586 to 3,401, or 5 percent.

The number of “fire personnel” would be cut by 140 personnel (jobs) from 4,221 to 4,081, or 3 percent. Smokejumpers would be reduced from 145 to 140, or 3 percent, and engines from 610 to 605, or 1 percent.

The numbers of all DOI firefighting aircraft would remain the same, except single engine air tankers would be cut from 34 to 32, or 6 percent.

Department of the Interior Fire Preparedness funding for FY 2018
The President’s proposal for Department of the Interior Fire Preparedness funding for FY 2018. Source: DOI.

As stated above, the DOI’s contribution to the Joint Fire Science Program would be cut in half, to $3 million, while the FS will eliminate their share of funding the program.

Thanks and a tip of the hat go out to Bean.
Typos or errors, report them HERE.

Can technology determine the best escape route for firefighters?

Of the 22 research proposals funded by the Joint Fire Science Program in June, 16 of them were various ways of studying vegetation. At the time we wrote, “It would be refreshing to see some funds put toward projects that would enhance the science, safety, and effectiveness of firefighting.”

A recently completed study is directed toward the firefighters on the ground. The U.S. Forest Service has paid to have researchers study the feasibility of using LiDAR and computers to determine the most efficient and quickest escape routes if firefighters have to withdraw while attacking a wildfire. The LiDAR helped researchers evaluate how landscape conditions, such as slope, vegetation density, and ground surface roughness affect travel rates.

I have a feeling that there will have to be significant advances in portable handheld technology before fire crews in remote areas can take advantage of this type of data. However, who knows, maybe in 10, 20, 30, or 40 years grunts on the ground will have access to sophisticated tools that we can’t even imagine today. They might just speak into a lapel pin to ask for the best escape route, and an augmented reality head-up display or an orbiting drone with a visible laser will designate the path.

Even though the research was paid for by United States taxpayers through the U.S. Forest Service, those same taxpayers will be charged a second time if they want to see the full results of their investment. The fee is $25 to get a copy of the .pdf. It may be available months or years down the road at no additional cost.

The title of the paper is, A LiDAR-based analysis of the effects of slope, vegetation density, and ground surface roughness on travel rates for wildland firefighter escape route mapping.

A year ago the same group of researchers studied how to find and evaluate safety zones in a paper titled, Safe separation distance score: a new metric for evaluating wildland firefighter safety zones using lidar. This research IS accessible to taxpayers without paying a second time.

The recent paper about escape routes was written by Michael J. Campbell, Philip E. Dennison, and Bret W. Butler. Here is a summary of some of their findings.

Every year, tens of thousands of wildland firefighters risk their lives to save timber, forests and property from destruction. Before battling the flames, they identify areas to where they can retreat, and designate the best escape routes to get from the fire line to these safety zones. Currently, firefighters make these decisions on the ground, using expert knowledge of fire behavior and assessing their ability to traverse a landscape.

Now, a University of Utah-led study has developed a mapping tool that could one day help fire crews make crucial safety decisions with an eagle’s eye view.

The new study is the first attempt to map escape routes for wildland firefighters from an aerial perspective. The researchers used Light Detection and Ranging (LiDAR) technology to analyze the terrain slope, ground surface roughness and vegetation density of a fire-prone region in central Utah, and assessed how each landscape condition impeded a person’s ability to travel.

Escape Route wildfire“Firefighters have a great sense for interactions between fire and landscape conditions. We hope to offer to them an extra tool using information collected on a broad scale,” says lead author Michael Campbell, doctoral candidate in the U’s Department of Geography.

Department of Geography professor and co-author, Philip Dennison, adds, “Finding the fastest way to get to a safety zone can be made a lot more difficult by factors like steep terrain, dense brush, and poor visibility due to smoke. This new technology is one of the ways we can provide an extra margin of safety for firefighters.” Continue reading “Can technology determine the best escape route for firefighters?”

Research projects funded by Joint Fire Science Program concentrate on vegetation

Joint Fire Science ProgramThe Joint Fire Science Program announced on Friday which research projects are being funded for fiscal year 2017. Of the 22 approved proposals, about 16 of them are various ways of studying vegetation.

It would be refreshing to see more funds put toward projects that would enhance the science, safety, and effectiveness of firefighting.

Click HERE to see the list of approved research projects.

New data from the Joint Fire Science Program

The Joint Fire Science Program has posted some new “Fire Science Briefs” on their web site.

Some of the new ones include:

  • How Does a Sierran Forest Grow? Fire, Thinning, and Regenerating Trees
  • Searching, Witnessing, Testing: Plants and Fire in Southern California
  • All Fired Up: Whitebark Pines are Crucial in the Cascades and Beyond
  • In a Ponderosa Pine Forest, Prescribed Fires Reduce the Likelihood of Scorched Earth
  • Earth and Fire: Forest Rely on Healthy Soils for a Well-rounded Diet
  • Something In the Air: Climate, Fire, and Ponderosa Pine in Southwestern Colorado
  • When Chaparral and Coastal Sage Scrub Burn: Consequences for Mammals, Management and More

Next week they will add several research publications under their “Science You Can Use” section, including:

  • Southern Beetles: Effects of Prescribed Fire and Fire Surrogates on Saproxylic Coleoptera in the Southern Appalachians of North Carolina
  • Black Hills: Can Prescribed Fire Be Used to Maintain Fuel Treatment Effectiveness Over Time in Black Hills Ponderosa Pine Forests?
  • Alaska: Fire History and Fire Management Implications in the Yukon Flats National Wildlife Refuge, Interior Alaska
  • Postfire Valuations for BAER: Nonmarket Resource Valuation in the Postfire Environment
  • Southwest: Fuel Loadings in Forests, Woodlands, and Savannas of the Madrean Province
  • Cheatgrass: Fire, Native Species, and Soil Resource Interactions Influence the Spatio-temporal Invasion Pattern of Bromus tectorum
  • Wildland Fire Suppression Costs: Factors Influencing Large Wildland Fire Suppression Expenditures
  • Burn Probability: Evaluating Spatially-Explicit Burn Probabilities for Strategic Fire Management Planning
  • Interior West Fuel Treatments: Objectives and Considerations for Wildland Fuel Treatment in Forested Ecosystems of the Interior Western United States
  • Shrubland Proceedings: Shrublands Under Fire: Disturbance and Recovery in a Changing World

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