Fighting Wildfires With Fire

Catastrophic wildfire may be defined as a fast-moving, vegetation-fueled fire that affects people, structures, and/or terrain, causing death and significant damage.

Public policy decisions regarding catastrophic wildfire continue to emphasize an open treasury for suppression and little for prevention and public education.

As recently as this month, the Marple fire in Castaic consumed more than 21,000 acres at a suppression cost exceeding $1 million per 24-hour period.

Had this been a classic urban/wild-land interface fire, the cost of suppression would have surpassed $2 million per 24-hour period as occurred in the “firestorm” (Calabasas/Malibu) fires of 1993. Not included in the 24-hour period suppression cost are the “watershed rehabilitation” measures involving erosion and mud flow management necessary with the approach of fall and winter storms.

Strange as it may seem, all recent (since 1985) catastrophic wildfire events have been predicted by wildfire specialists or researchers using various prediction techniques.

These techniques involve historical wildfire data, shrub condition and the latest tool, high-altitude infrared imagery. The application of these systems identified the “stressed” areas of the Goleta (paint) fire, Oakland/Berkeley, Laguna, Altadena, Calabasas/Malibu, and most recently, the Marple fire. Stressed, old-age chaparral is the culprit.

There has been a great deal of hand-wringing about new development on hillside communities contributing to the wildfire problem. A close analysis of all catastrophic wildfires that have occurred since 1990 clearly reveals that the greatest risk is hillside housing and landscaping constructed or planted before 1980. Regarding arson-induced fires, consider that if a generally explosive condition exists, it makes little difference if the fire was ignited by an arsonist, wires down, lightning or rocks striking each other.

All vegetation is a fuel. The U.S. standard for measuring the energy of burning fuel is the British thermal unit, or BTU. A BTU is the amount of energy it takes to raise a pound of water 1 degree Fahrenheit. A single candle flame or a kitchen match equals one BTU. A cup of gasoline contains 8,500 BTUs.

Comparably, one pound of chaparral contains about 8,500 BTUs. Ignite the gasoline in a cup and it will burn evenly. Ignite gasoline spread across the floor and it will burn extremely rapidly--if not explosively.

Similarly, “aerate” the chaparral by suspending it in air, pass a 30-plus-mph wind through it at 80 degrees Fahrenheit, provide ignition and the chaparral will react almost as explosively as the cup of gasoline. Fuel arrangement and fuel load play an equal part in combustion. By lowering the fuel load or the fuel surface-to-volume ratio, the fuel will burn less rapidly.

Since terrain and weather are unmanageable, consider managing the fuel load itself. This can be accomplished mechanically around a structure or along roads.

A fuel management technique termed “prescription burning” is the most cost-effective and environmentally acceptable fuel management tool where there exists large blocks of unbroken chaparral fields, i.e., Topanga State Park, Santa Susana Mountains, Angeles National Forest and similar chaparral-covered terrain.

Prescribed burning is the application of fire to wild-land fuels when conditions such as weather, fuels and topography permit a specific objective to be accomplished safely.

This system has been used in Stone Canyon, burning directly under the eaves of homes along Roscomare Road to prevent another Bel-Air fire. The cost of that burn was in excess of $1,100 per acre. That is still cheaper than the wildfire loss of structures and suppression costs.

In the Santa Clarita Valley, several 3,500-plus-acre parcels were burned at a cost below $50 per acre. The U.S. Forest Service has conducted prescribed burns in remote areas for less than $15 per acre.

There exists a significant body of evidence that fuel reduction through prescribed burning has been curtailed due to budget constraints, while wildfire suppression costs are escalating.

Increased acreage consumption and significantly higher structure loss reinforce the debate as to whether vegetation management and fire suppression are mutually exclusive.

A vegetation management program can provide a lower cost for fire suppression, limit critical watershed damage, lower air pollution and, just as important, provide for adequate clearance so that structures can survive.