Wildfire Simulation Technology – Part 3

Beneath every wildfire model there is a set of assumptions, ideally based on a theory of how fire ignites and spreads. The model, however, is only as good as the theory that drives it and the data that goes into it. As computers have gotten smaller and...

Modeling is easy, according to Finney, anybody can produce a model – so there’s dozens of models. “But, that’s a telltale sign of when people are substituting technology for science,” he warned. “We lack that underlying knowledge of how things really work. We’re not yet at the point where we know what we can put in a model, so people are stuffing whatever they want in there.” Not something that makes for reliable wildfire behavior prognostications!

An Abundance of Theories

Not everyone in fire science is working from the same set of notes. “There’s not one way to look at this that people agree on, and that’s a problem because there’s only one physics somewhere and until you can explain how fire spreads and can repeatedly prove it, it’s really hard to formulate the principles on which you’re going to base your model,” Finney explained. “We are still at the point where scientists don’t have a coherent theory of how fire spreads, and even worse, they don’t even bother with the theory.” Finney says scientists assume radiation works like this and assume convection works like that, and because they’re trying to model it rather than try to understand it, there’s a real difference.

Finney is concerned that the cart is being put before the horse. “Models are an abstraction of reality; they’re a simplification and are intended to be wrong because you have to compromise things to make a model work. So, it is a little surprising at this stage of the game that we don’t have a theory of fire spread.”

According to Finney, we haven’t yet reached the point where we have a reliable physical theory and where our models all actually diverge from that theory. “We’ve narrowed in on some things that, although they don’t constitute a complete theory, they are part of one, very essential physical process,” he explained.

Practical Application

As mentioned in a previous article in this series, a wildfire that burned outside of Hungry Horse, MT, in 2003 demonstrated the power (and the limitations) of modeling. Finney explained: “We prepared a number of different model runs [for firefighters], one of which was a thunderstorm that produced spotting on the other side of the lake, but it was enough to say, ‘Hey, this could happen,’ so that they were able to take precautions against it. The thunderstorm appeared, it blasted some embers across the lake, and they were there to pick them up.” Hungry Horse was an example of where a model could be used to point out something that wasn’t obvious, concluded Finney – not predicting that it would happen, just showing that it could happen.

“Models show the potential for something to happen, but it takes awhile for operational people to understand how to use models,” said Finney. “It takes awhile for people to understand that this software won’t predict the results of tomorrow’s horse race.”

And bear in mind the limitations. “One thing that really constrains us with fire is that we’re never going to know enough about the environment (what the wind is like everywhere or what the fuel particles are doing everywhere), so we can’t feed even a perfect model with enough information,” Finney cautioned.

So, it appears that much remains to be done before wildfire models will be able to accurately forecast how a blaze behaves, but each day fire scientists get closer to realizing that goal. It will be interesting to see where the U.S. Forest Service scientists are in another 50 years!

MIKE ARCHER is an author, wildfire consultant, systems engineer, and public speaker who has been interviewed by CBS News, KABC-TV, USA Today, and the Associated Press on wildfire topics, and has been part of a delegation testifying before government bodies (including Congress and the California Senate) on fire-related issues. He runs the Wildfire News of the Day blog and Firebomber Publications.