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FIRE BEHAVIOR

FIRE BEHAVIOR. Three types of fire behavior. Surface fire: Ground: Crown:. Fuels at or near the surface. Subsurface organic fuels (duff, organic soils). Tree crowns. Categories of fires according to human management action:. Wildfire: Management ignited prescribed fire:

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FIRE BEHAVIOR

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  1. FIRE BEHAVIOR

  2. Three types of fire behavior Surface fire: Ground: Crown: Fuels at or near the surface Subsurface organic fuels (duff, organic soils) Tree crowns

  3. Categories of fires according to human management action: • Wildfire: • Management ignited prescribed fire: • Prescribed natural fire: Suppression action is taken Ignited to meet a management objective Allowed to burn under a management plan to preserve natural role of fire

  4. Weather Topography FIRE Fuels Fire Behavior: The Wildland Fire Environment

  5. Components of the Wildland Fire Environment Weather • Temperature • Relative Humidity • Atmospheric Stability • Windspeed and Direction • Precipitation

  6. Components of the Wildland Fire Environment Topography • Elevation • Position on Slope • Aspect • Shape of Country • Steepness of Slope

  7. Components of the Wildland Fire Environment Fuels • Fuel Loading • Size and Shape • Compactness • Horizontal Continuity • Vertical Continuity • Chemical Content

  8. Effects of topography on fire behavior.

  9. Fuel load Temperature Winds Moisture

  10. Effect of Aspect on Fuel Temperature and Moisture Heaviest snows Highest Moisture Lowest Temperature Later Curing of Fuels Late Snow Melt Wind Direction Fuels Transition Earlier Heating Earlier Cooling Generally Lee Side of Mountain Fuels Transition Later Heating Later Cooling Generally Windward Side of Mountain Lightest Fuels Lowest Fuel Moisture Highest Temperature Earlier Curing of Fuels Earlier Snow Melt

  11. Slope Affects Fire Behavior Burning Material Rolling Downslope Preheating Draft Faster Ignition and Spread

  12. Characteristics of Fire Behavior FIRE INTENSITY – Heat release per unit time (BTUs or KJ) • Fuel loading • Fuel moisture content • Compactness or arrangement of fuels Fire Intensity Affected by

  13. Spread Direction Flame Height Flame Length Flaming Zone

  14. Rate of Spread (ROS) The distance a fire travels during a given period of time. Rate of spread = distance/time Burned Area Primary factors affecting rate of spread? • Increased fire intensity • Windspeed • Steepness of slope

  15. 4 acres (front) 16 acres 36 acres

  16. Team Work • Construct a sentence using your term(s) that explains the behavior of a particular fire situation but WITHOUT USING THE TERM IN THE IN THE EXPLANATION– the rest of the class should be able to determine what the term is based on your explanation.

  17. Running Creeping Smoldering Spotting Spot fires Fire brand Torching Crowning Flareup Blowup Fire Whirls Wildfire Management ignited prescribed fire Prescribed natural fire Ground fire Surface fire Crown fire Chimney effect Slope reversal Chimney Effect Slope Reversal

  18. Bottom of a Narrow Canyon

  19. Slope Reversal

  20. Three types of fire behavior Ground fire: Surface: Crown: Subsurface organic fuels (duff, organic soils) Fuels at or near the surface Tree crowns

  21. Categories of fires according to human management action: • Wildfire: • Management ignited prescribed fire: • Prescribed natural fire: Suppression action is taken Ignited to meet a management objective Allowed to burn under a management plan to preserve natural role of fire

  22. Types of fire behavior Running – spreading quickly Creeping – spreading slowly with low flames Smoldering – burns without flames; barely spreading Spotting – sparks/embers carried by wind or combustion column or moved by gravity Spot fires – new ignition points Fire brand – a piece of burning material

  23. Types of extreme fire behavior Torching – surface fire moves into crowns of individual trees Crowning – spreads from tree crown to tree crown (dependent, active, or independent) Flareup – sudden acceleration of fire spread or intensity (short duration, for portion of fire) Blowup – dramatic change in the behavior of the whole fire (rapid transition to a severe fire) Fire Whirls – vortex (gas mass with rotational motion)

  24. Fire Affects Its Own Environment Local Winds Atmospheric Stability Clouds/Precipitation Fuel Temperature Fuel Moisture

  25. Wind-driven fire behavior Plume-dominated fire behavior (with downbursts)

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