§ This year’s fires leaping across the Southwest present a gallery of high-octane fire behavior. There are long-range spots that mock efforts to hold control lines. There is saturation spotting, and the ember attacks that take out most houses. Crown fires blast through the canopies of forests that don’t normally support them. Vast convective columns, bent by winds, twist into facsimiles of fire hurricanes. Plumes punch upward into towering pyrocumulus. All are known phenomenon, but this spring they were all on display, and all seemingly injected themselves with performance enhancers. But they are not how we model fire.
When the International Crown Fire Modeling Experiment in Canada’s Northwest Territories installed cameras inside the flaming front, the resulting motion pictures showed a violent swirl and boil of flame, spark, and light; a full-immersion baptism by heat in all its varieties. Recent lab experiments suggest that even pine needles require such immersion to ignite or else they radiate heat away on one side as quickly as they receive it on the other. The prevailing models for fire spread, however, imagine a two-dimensional fire propagating by preheating fuel particles through radiant flux. More intense fires are imagined to scale up into three-dimensions by subjecting larger fuel arrays to the same mechanisms, or by a cascade upward. With considerable labor it is possible to yield approximations to what happens in the field. A thoughtful observer of this season’s conflagrations might reverse that picture and imagine a three-dimensional problem in fluid dynamics that, in some circumstances, simplifies into two-dimensions for which radiant heat transfer is dominant.
Our models, in brief, don’t reflect the reality of fire behavior. They reflect the reality of modeling. They express what can be done within the traditions of the disciplines doing the exercise.
§ Before those outside the fire modeling community begin to gloat, however, they might consider that other behaviors associated with fire suffer the same lacuna. For four weeks, while on my fire-study tour of California, I have had to cope with the realization that the academic history I imagined writing is at odds with how people have told me events actually happened.
The narrative I would have crafted follows a spoor of documents, recorded decisions, investigated phenomena, all with artifacts lodged in archives or in holding pens before being hauled to formal depositories. The story speaks of institutions and agencies, or of parks and forests, or of ideas, or of moments when nature erupted. That’s how historical scholarship works. It appeals to common templates for organizing accounts. Most practitioners in the humanities would shudder at calling that modeling, but an outsider might well consider the outcome as such. All, however, would recognize the character of the written narrative that results, and if they objected to its conclusions, they would propose modifications or pen an alternative narrative. They would answer, that is, within the same methodology.
The problem is that this representation is not how participants recall events. Universally, they tell a story of people, and of people dealing with people. Arguing with a contract county fire department. Dealing with state legislators. Wrestling with a new FMO (but old fire dog), redolent in nomex, suspicious of prescribed burning, and scornful of natural fire. A wealthy rancher who didn’t want smoke at his weekend cabin. The survivor of a dreadful burn who continually strokes his psychological scar tissue. A governor who denounced his staff, a superintendent who celebrated his. A charismatic partisan enflaming acolytes to take up the cause. Institutions and ideas don’t matter: people do. Policies don’t spread park by park, or agency by agency, by institutional radiation; they undergo spasms of immersive angst and enthusiasm; they spread by conflict or else they go out. They propagate through people.
At Sequoia-Kings Canyon National Park historian scholars would likely narrate a chronicle of research, national policy reforms, revised or replaced fire plans. They would point to fires set and acres burned, budgets and organizational charts. They would code events and sentiments into formal registers and store them in acid-free folders in temperature controlled rooms. The story would go from preserved print to print. But locals remember the history and its dynamics differently. They would speak of Harold Biswell, Bruce Kilgore, Howard Shellhammer, Tom Nichols, and “Pyro Pete” Schuft. They moved the people who moved fire around the land.
Both groups are right. A better narrative would be one that accounts for both processes, that can capture the detail of personalities and deeds yet still abstract from that welter of personalized contacts a more formal rendering that can sketch the larger forest out of the thicket of past trees. Most scholars are keen for that model narrative – that’s what scholarship does. But sometimes, as at Sequoia, we need to ignore the forest and look at those Big Trees.
June 2011 / [PDF]