Fire Behavior and Fuels
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What is fire behavior?

The term fire behavior is used to describe the magnitude, direction, and intensity of fire spread. The magnitude is measured as the velocity, in meters/second, of the leading edge of the flaming portion of the fire. The direction is measured as the bearing of the leading edge of the fire and will vary from zero to 360 degrees. Finally, the intensity is measured as the energy released from the fire per unit area, in jules/sq. meter.

A fire that spreads rapidly and releases a large amount of energy is sometimes referred to as a conflagration or firestorm. Fires burning through Southern California chaparral can display this type of behavior. Fires which spread rapidly, but with low intensity, are sometimes referred to as flashy. Fires burning through grass, which lacks the biomass of chaparral, are often described in this way. A fire that spreads neither rapidly nor with great intensity is referred to as a creeping fire. Typically, a fire spreading downslope without the assistance of the wind is described in this way.

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For more information about specific aspects of fire behavior, follow these links:

What are fuels?

Fuels is the name given to the suite of variables used to describe the material a fire is spreading through. A complete fuels description includes measurements of load (mass per unit area), heat content (energy per unit mass), surface-area-to-volume ratio, height, and moisture content.

What are fuel models?

Spatially explicit fire behavior models require measurements of elevation, slope, aspect, weather and vegetation to simulate fire behavior across the landscape. The fuel parameters, collectively termed fuel models, used in these simulations vary based upon the specific requirements of the model chosen to forecast fire spread. In general, most fire behavior models will require estimates of the following variables to generate predictions: total aboveground biomass contributing to the forward rate of spread of the fire; mean stand height; fuel particle surface-area-to-volume (SAV); and moisture content.

More information

For more information about specific aspects of fuels, follow these links: