Introduction to Wildland Fire Behavior

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 • 00-01-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 01-02-S190

6. Heat Transfer • Radiation • Convection • Conduction 01-03-S190

7. Wildland Fire Behavior Triangle Topography Fuel 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 01-04-S190

9. Fuel Types • Grass • Shrub • Timber litter • Logging slash 01-05-S190

10. Fuel Characteristics • Size and shape • Fuel moisture • Fuel loading • Horizontal continuity • Vertical arrangement 01-06-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 01-08-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 01-07-S190

15. Fuel Loading • The quantity of fuels in an area 01-09-S190

16. Horizontal Continuity andVertical Arrangement • Horizontal continuity • Uniform • Patchy • Vertical arrangement • Ground • Surface • Aerial 01-10-S190

17. Uniform Fuels 01-11-S190

18. Patchy Fuels 01-12-S190

19. Vertical Arrangement of Fuels 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. 01-13-S190

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. 01-15-S190

23. Aspect North Heavy fuels Shade Moisture South Light fuels Sunny Dry 01-16-S190

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 Convection and radiant heat Flame is closer to fuel 01-17-S190

28. Position of Fire on Slope Fire near top of slope Slope Fire near bottom of slope has rapid spread upslope 01-18-S190

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 01-19-S190

31. Radiant Heat Across Narrow Canyon 01-20-S190

32. Spotting Across Narrow Canyon 01-21-S190

33. This fire is moving into an area of stronger wind and an enclosed area where radiant heat can collect Lateral Ridge to Canyon 01-22-S190

34. Mountains Cause Channeling of Wind 01-23-S190

35. Elevation As elevation increases, temperature will decrease Trees Shrubs Grass Sea level 01-24-S190

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