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Introduction to Wildland Fire Behavior S-190 Unit I.

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Presentation on theme: "Introduction to Wildland Fire Behavior S-190 Unit I."— Presentation transcript:

1 Introduction to Wildland Fire Behavior S-190 Unit I

2 Course Objectives Identify and discuss the three sides of the fire triangle Identify the environmental factors of wildland fire behavior that affect the start and spread of wildland fire Recognize situations that indicate problem or extreme wildland fire behavior S190

3 Unit 1 Objectives Describe the fire triangle Identify three methods of heat transfer List the three principle environmental elements affecting wildland fire behavior List three factors of fuel that affect the start and spread of wildland fire 01-01(1 of 2)-S190

4 Unit 1 Objectives (cont.) Describe how slope affects wildland fire spread List four factors of topography that affect wildland fire behavior Describe the dangerous conditions that can develop in a box canyon and steep narrow canyons 01-01(2 of 2)-S190

5 Fire Triangle Heat Oxygen Fuel S190

6 Heat Transfer Radiation Convection Conduction S190

7 Wildland Fire Behavior Triangle Fuel Topography Weather

8 Group 1 — Fuels Fuel moisture Size and shape –Light fuels vs. heavy fuels –Fuel loading Horizontal continuity –Uniform and patchy Vertical arrangement –Ground, surface, aerial S190

9 Fuel Types Grass Shrub Timber litter Logging slash S190

10 Fuel Characteristics Size and shape Fuel moisture Fuel loading Horizontal continuity Vertical arrangement S190

11 Fuel Size and Shape Make a huge difference in how the fire will behave –Fuel moisture –How it will spread –How fast it ignites –How well will it transfer fire to other fuels –How long and intense will it burn

12 Categories of Fuel Light fuels –Leaves, grass, shrubs Light fuels catch easily and burn quickly Because they don’t have much weight, they are consumed quickly These are the primary carriers of fire S190

13 Categories of Fuel Heavy fuels –Limbs, logs, stumps Heavy fuels are more difficult to ignite, and move slower than fires in light fuels However, expect large amounts of heat and long burning times

14 Fuel Moisture The amount of water in a fuel expressed as a percentage of the oven-dry weight of that fuel Size of the fuel play directly into how much moisture it will hold and how fast it can gain or lose moisture –1 hour –10 hour –100 hour –1000 hour S190

15 Fuel Loading The quantity of fuels in an area S190

16 Horizontal Continuity and Vertical Arrangement Horizontal continuity –Uniform –Patchy Vertical arrangement –Ground –Surface –Aerial S190

17 Uniform Fuels S190

18 Patchy Fuels S190

19 Vertical Arrangement of Fuels S190 AERIAL FUELS: All green and dead materials located in the upper forest canopy including tree branches and crowns, snags, moss, and high shrubs. SURFACE FUELS: All materials lying on or immediately above the ground including needles or leaves, duff, grass, small dead wood, downed logs, stumps, large limbs, and low shrubs. GROUND FUELS: All combustible materials lying beneath the surface including deep duff, roots, rotten buried logs, and other organic material.

20 Ladder Fuels Ladder fuels are areas where a surface fire can easily move into the aerial fuels

21 Fire moving through Ladder Fuels

22 Group 3 — Topography Aspect –Direction a slope faces Slope –Steepness Position of fire –Top, middle, or bottom of slope Shape of country –Narrow canyons and box canyons Elevation –Relates to curing of fuels, precipitation, length of fire season, etc S190

23 Aspect S190 North Heavy fuels Shade Moisture South Light fuels Sunny Dry

24 South Facing Aspect

25 North Facing Aspect

26 Fire and slopes Due to convected heat, fires will move uphill 20 times faster than they will downhill. Flame lengths are generally pointed in an uphill direction (where more fuel is) Upward moving heat will preheat fuels farther up the slope The steeper or longer the slope, the faster the fire will spread

27 Steep Slopes Cause Rapid Fire Spread S190 Convection and radiant heat Flame is closer to fuel

28 Position of Fire on Slope S190 Fire near top of slope Fire near bottom of slope has rapid spread upslope Slope

29 The hazards of narrow or box canyons The enclosed space of the canyons have a tendency to channel wind Keeps radiant heat in the area due to the shape of the country Canyons expose more fuel to heat and brands Fires can preheat several aspects inside the canyon all at once

30 Box Canyon and Chimney Effect S190

31 Radiant Heat Across Narrow Canyon S190

32 Spotting Across Narrow Canyon S190

33 Lateral Ridge to Canyon S190 This fire is moving into an area of stronger wind and an enclosed area where radiant heat can collect

34 Mountains Cause Channeling of Wind S190

35 Elevation S190 Trees Shrubs Grass Sea level As elevation increases, temperature will decrease

36 Unit 1 Objectives Describe the fire triangle Identify three methods of heat transfer List the three principle environmental elements affecting wildland fire behavior List three factors of fuel that affect the start and spread of wildland fire 01-25(1 of 2)-S190

37 Unit 1 Objectives (cont.) Describe how slope affects wildland fire spread List four factors of topography that affect wildland fire behavior Describe the dangerous conditions that can develop in a box canyon and steep, narrow canyons 01-25(2 of 2)-S190


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