Study: Angora fire unstoppable
Tree thinning, homeowner maintenance and firefighters' efforts limited damage, Forest Service says.
By Chris Bowman – Sacramento Bee Staff Writer
Saturday, August 4, 2007
The air was wrung so dry, the trees stood so parched and the wind hollered so fiercely that nothing short of a half-mile-wide clear cut would have stopped the Angora fire from torching a Lake Tahoe community six weeks ago, according to a Forest Service study released Friday.
Forest thinning and homeowner clearance of deadwood, along with "aggressive" firefighting, nonetheless spared many homes and, perhaps, lives, the report said.
The blaze that started June 24 destroyed 254 houses but caused no deaths on the outskirts of South Lake Tahoe, the worst wildfire to strike the High Sierra basin in modern times.
The Forest Service credits its forest-thinning projects in the area and some homeowners' maintenance of "defensible space" for slowing the burn and diminishing the smoke enough for firefighters and sheriff's deputies to efficiently evacuate neighborhoods.
"This report shows that you need both thinning and defensible homes to prevent future Angora fires. Either one by itself is not enough," said Matt Mathes, spokesman for the agency's regional office in San Francisco.
Defensible space helped only so much. Evidence from several on-site inspections indicated that trees caught fire from burning houses -- not the reverse -- the report said. In most of these cases, houses most likely caught fire from firebrands -- pieces of burning wood -- thrown up from neighboring houses that were ablaze.
The study reinforced preliminary Forest Service findings that thickets of dead and dying trees along Angora Creek -- an environmentally sensitive area off limits to conventional logging operations -- "likely contributed" to the fire's rapid spread.
The agency acknowledged that one of its 2004 thinning projects effectively backfired because the piles of dry cut wood remained on the site. Officials said they did not have a chance to burn the remains because of air-quality restrictions in the Tahoe basin.
Billed as the most definitive analysis yet of the fire, the investigation included interviews of homeowners, firefighters and fire-behavior experts along with aerial photos and video taken before, during and after the blaze. Officials reconstructed the course of the fire and tried to pinpoint conditions that intensified or allayed the destruction.
The 3,072 acres within the fire's perimeters are mostly unoccupied national forest land, but residential areas have the density typical of suburban neighborhoods and bump right against the forest. Traced to an unattended campfire, the Angora fire "burned under some of the most severe fire danger conditions experienced in this area during the last 20 years," the report said.
Moisture in the standing trees was an average 73 percent, a near-record low for June 24, and the relative humidity was 8 percent, the lowest ever recorded for the date, the report said. Winds speeds ranged from 12 mph to 22 mph at nearby Meyers, but firefighters and other witnesses estimated gusts up to 40 mph on the fire lines. "Under the weather conditions present during the Angora fire, all vegetation would need to have been removed for as much as one-half mile to stop the fire without suppression action," the report said.
The Forest Service does not suggest clear cutting as a way to tame wildfires. Rather, the report found that most thinning projects worked as intended, reducing the intensity of the blaze from a crown fire that tosses embers hundreds of yards to ground fires that give firefighters better odds of saving homes. "Where urban lots had fuel treatments, they served as firebreaks, allowing firefighters to safely protect structures," the report concluded.
The report does not make recommendations. That is the charge of a commission created by the governors of California and Nevada to examine ways to reduce the wildfire threat while protecting Lake Tahoe, one of the world's clearest alpine lakes. Its findings are due in March.