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Unit 11: Fire Behavior Prediction Systems

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Systems Pt. 1   ::   Worksheet & Field Guide   ::   Practice   ::  Systems Pt. 2  ::   Estimating   ::   Exercises

Effective Windspeed

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Effective Windspeed : The midflame windspeed adjusted for the effect of slope on uphill fire spread.

Slope Considerations in Fire Behavior Calculations

Calculation procedures based on midflame windspeed and slope.

Example 1 Example 2
Wind upslope, spread upslope – use the midflame windspeed and maximum slope value. Wind downslope, spread upslope – use the maximum slope value with zero windspeed.
Example 3 Example 4
Wind upslope, spread downslope – use zero slope and zero windspeed. Wind downslope, spread downslope – use midflame windspeed and zero slope.

The procedures for using the fire behavior prediction model go on and on. If you're a Plans Chief on a large fire, you will want to know what to expect of fire behavior on all portions of the fire perimeter. This requires line source fire predictions. How far might firebrands travel to cause spot fires? What will be the maximum scorch height in a stand of timber? What is the potential for a free burning, continuous fire front?

These questions and many others are covered by procedures taught in advanced fire behavior courses. If you have special needs or interest in the fire behavior predictions area, note the publications listed in the reference bibliography in the student guide. You might also contact a qualified Fire Behavior Officer in your area for help.

Adjustments

Adjustments to calculations can be made by these methods:

  1. The first thing you should do is to re-examine the input values. (The inputs may not be accurate)
  2. Use an adjustment factor. (Determine by comparing calculated and actual values)
  3. Use the two fuel model concept. (Calculations are run for two fuel models which represent the predominate fuels, then output values are combined according to their proportionate coverage of an area)
  4. Tailor a fuel model for the site. (Develop a local fuel model by a computer program such as BehavePlus)

Additional fire behavior prediction procedures are described in a number of publications listed in the reference bibliography in the student guide. Also contact a qualified fire behavior officer in your area for help.

Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, November 16). Unit 11: Fire Behavior Prediction Systems. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: http://ocw.usu.edu/Forest__Range__and_Wildlife_Sciences/Wildland_Fire_Management_and_Planning/Unit_11__Fire_Behavior_Prediction_Systems_6.html. This work is licensed under a Creative Commons License Creative Commons License