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Unit 2: Fuels Classification

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Distribution & Behavior   ::   Characteristics   ::   Timelag & Life Cycle   ::   Availability   ::  Models  ::   Exercises

Fuel Models

Fuel model is a simulated fuel complex for which all the fuel descriptors required for the solution of a mathematical fire spread model have been specified.
Since the fire model only applies to surface fires, ground fuels and aerial fuels are not included in the fuel descriptors. The components that are described include needles or leaf litter, dead and down woody material, grasses and forbs, shrubs, and regeneration. Various combinations of these components make up the fuel models.
There are 13 stylized fuel models that are used to make fire behavior predictions. These must represent a wide variety of fuel conditions. Choosing the appropriate fuel model requires experience and personal judgment.
Four major fuel community groups are:

  1. Grass
  2. Shrub
  3. Timber
  4. Slash

Fire Behavior Fuel Model Key

Always check the selected model with fuel model description.

  1. Primary carrier of fire is grass. Expected rate of spread is moderate to high, with low to moderate intensity.
    1. Grass has a relatively fine structure, is generally below knee level and is easy to walk through. Model 1
    2. Grass has thick, coarse stems, is above knee level and is difficult to walk through. Model 3
    3. Mixture of grass and litter beneath open timber or brush overstory that does not burn. Model 2
  2. Primary carrier of fire is brush. Expected rate of spread and intensity are both moderate.
    1. Vegetation type is southern rough or low pocosin. Model 7
    2. Live fuels absent or sparse with no capability to reduce fire spread rate. Model 6
    3. Live fuel moisture can have a significant damping effect on the fire behavior.
      1. Brush is about knee deep with a ligh loading of 1-hour timelag fuels. Model 5
      2. Brush is close to head high with a heavy loading of 1-hour timelage fuels. Model 4
  3. Primary carrier of fire is debris beneath a timber stand.
    1. Live fuels are present in sufficient quantity to influence fire behavior. The load of 100-H TL fuels is heavy. Model 10
    2. Surface fuels are mostly foliage litter, with little or no live fuel.
      1. 1-H TL load strongly predominates; 10-H and 100-H TL fuels are sparse. Foliage litter is long needle pine or hardwood leaves, loosely compacted. Model 9
      2. 1-H and 10-H TL fuel load combined is about equal to 100-H TL load. Foliage litter is short needle coniferous or small hardwood leaves, tightly compacted. Model 8
  4. Primary carrier of fire is slash.
    1. Slash is not continuous. Other ground fuels must be present to help carry the fire. Average slash depth is about 1 foot. Model 11
    2. Slash is continuous or nearly so. Other surface fuels need not be present to carry the fire. Average slash depth is about 3 feet. Model 13
    3. Slash generally covers the ground, though there may be bare spots or areas of light coverage. Average slash depth is about 2 feet. Model 12

Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, October 20). Unit 2: Fuels Classification. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: This work is licensed under a Creative Commons License Creative Commons License