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Unit 1: The Changing Fire Environment

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Rate of Spread

Approximate fire shapes for various windspeeds

The figures below illustrate some variations in the elliptical or egg-shaped patterns of fire spread, depending on wind speeds. As wind speeds increase, the fire shapes elongate. Note that these patterns are not drawn to scale, and merely illustrate fire shapes.

The fire shapes below can be used for planning purposes, particularly on the initial attack of fires. These shapes may not fit your fire situation, as conditions in the field can cause variations in fire shapes. These conditions are the following: heterogeneous fuel complexes that produce fingering, barriers that stop or partially stop the spread, the effect of slope that reduces or increases fire spread at the head or flanks, and spotting ahead of or down slope from a fire. All of these serve to complicate the task of estimating where the fire perimeter will be after times number of hours.

Rate of Spread 2.5 mi/hr Rate of Spread 5 mi/hr
Rate of Spread 10 mi/hr Rate of Spread 15 mi/hr
Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, October 04). Unit 1: The Changing Fire Environment. 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