Planned fires, 11 May 2000

Planned Fires at Whim of Nature

by The New York Times, 11 May 2000

BOISE, Idaho (AP) — Like every “prescribed burn” that federal land managers undertake, the New Mexico fire that has forced the evacuation of Los Alamos was planned in advance with scientific precision.

Then nature stepped in.

“This fire has experienced some severe wind events that were not totally forecasted,” said Tom Zimmerman, a National Park Service fire science and ecology program leader at the National Interagency Fire Center. “That was the variable that killed us on this one.”

Science can’t yet control the weather, but experts have some say over how the fire behaves.

Zimmerman said blazes like the one set to clear brush in the Bandelier National Monument all have specific fuel reduction goals and are extensively planned.

Each plan includes a description of the area to be burned, a statement about what land managers are trying to accomplish and a “prescription” — a set of size and intensity parameters within which the fire will ideally burn.

The parameters are based on what experts know about fire behavior. Parameters such as how high the flames are likely to burn and how fast the fire may spread are directly related to variables including the dryness of the grass, brush, trees or deadfall to be burned, as well as wind speed, air temperature and humidity, Zimmerman said.

Prescribed burns also take into account “firing patterns.”

“For example, if you light a fire at the base of a hill, you get the maximum speed of movement and maximum intensity because it moves up the slope,” Zimmerman said. “If you were to light that same fire at the top of the hill, you would create what we call a backing fire, which moves much slower and with much less intensity as it moves down the slope.”

Land managers have been studying the technology and methods for prescribed fires for years in an effort to prevent catastrophic wildfires by beating nature to the punch.

It’s a lesson learned, in part, by the 1988 fires in Yellowstone National Park that burned through decades of deadfall. One million acres of timber and meadow were scorched.

Not everyone is pleased with the idea of prescribed burns and the related policy of letting some naturally started fires burn out.

In 1996, a fire along the Idaho-Montana state line that was supposed to have covered only 18,000 acres under a worst-case scenario instead burned more than twice that amount. Air quality officials complained about the smoke and landowners complained that their property was needlessly threatened.

Some members of Congress also have criticized prescribed burns, saying they waste timber that should be harvested.

Today, land managers can take advantage of computer modeling of fire behavior and better ways of analyzing historic weather trends in their efforts to control prescribed fires.

“We’re pretty set that our prescribed fire procedures are sound,” Zimmerman said.


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