s-190 Wildland Fire Behavior

  1. Point of Origin
    precise location where ignition source became in contact with material first ignited and sustained combustion
  2. Head of Fire
    side of fire having fastest rate of spread
  3. flank of a fire
    part of fire's perimeter that is roughly parallel to main direction of spread
  4. rear of fire
    • portion of fire opposite of head
    • slowest spreading portion of fire edge
    • aka heel
  5. Fire perimeter
    entire outer edge or boundary of fire
  6. Fingers of a fire
    long narrow extensions of fire projecting from the main body
  7. pockets of a fire
    unburned indentations in fire edge formed by slow burning areas or fingers
  8. island
    area of unburned fuel inside the fire perimeter
  9. spot fire
    fire ignited outside perimeter by firebrands
  10. wildland fire triangle
    • Fuel to burn
    • air to provide oxygen for combustion
    • heat to start and continue combustion process

    remove any single one and there can be no fire
  11. 3 methods of heat transfer
    • radiation- heat ray or wave
    • convection- heat transfer thru air. hot air rises
    • conduction- direct contact of heat thru a medium
  12. fire CONTAINED
    control line is completed around the fire and any spot fires. confident that spread and forward progress has stopped
    hotspots are out, line will hold, burn out any unburned areas inside line
  14. fuel types
    • six major fuel types
    • grass- burns hottest and fastest
    • grass:shrub- significant contributor to spread, fine fuels mixed with aerial/shrub fuel
    • shrub- some highly flammable
    • timber:understory- ladder to aerial crown fuels
    • timber: litter- dominant in mountainous topo. provides fuel for ground fires
    • slash: blowdown- debris left after natural or human events. fuel for fire spread
  15. horizontal continuity of fuel
    affects rate of spread

    • uniform fuels- fuels distributed evenly over the area. network of connected fuels providing continuous spread
    • patchy fuels- fuels distributed unevenly across an area. fuel with definite breaks or barriers
  16. vertical arrangement of fuel
    • ground fuel-all combustible materials beneath the surface: duff, roots, buried logs
    • surface fuel- all combustible materials lying on or immediately above ground: needles, duff, grass, logs, shrubs, stumps
    • ladder fuel- combustible materials that aid the spread of fire from surface to canopy: shrubs, moderate height vegitation, tree trunks
    • aerial fuels- all green/dead fuels in uper canopy: tall shrubs, tree branches and crowns, snags
  17. fire environment triangle
    • weather
    • fuel
    • topography
  18. wind indicators that fire behavior is increasing
    • surface winds above 10 mph
    • lenticular clouds- indicate high winds aloft with potential to surface
    • high fast moving clouds- indicate wind shifts
    • approaching cold front- wind will increase in speed and and change direction
    • cumulonimbus development- possible wind speed/direction indicators and potential for erratic winds
    • sudden calm- wind change coming
    • battling or shifting winds
    • columns-  leaning, sheared, well developed, changing
  19. weather factors that indicate increaseing fire behavior
    • unstable atmosphere:
    •    -gusty winds cumulus clouds
    •    -castellatus clouds in a.m.
    •    -smoke rising straight up
    •    -inversion lifting
    • RH below 25%
    • temp. above 85 degrees
  20. indicators of possible increase in fire behavior
    • continuous fine fuels
    • heavy loading of fuels
    • ladder fuels and tight crown spacing and numerous snags
    • firebrand sources
    • bug kill/ dead trees preheated canopy
    • steep slopes greater than 50%
    • chutes/chimneys
    • firewhirls
    • frequent spotting
  21. box canyon
    • strong upslope drafts creating rapid spread
    • one way in/one way out
  22. narrow canyon
    • easily spreads fuel to opposite side with radiation and spotting
    • strong upslope air movement at sharp bends in canyon
  23. creeping fire
    burning with low flame and slow spread
  24. running fire
    behavior of fire spread rapidly with well defined head
  25. torching
    burning of the foliage of single tree or small group from bottom up. little or no lateral spread
  26. backing fire
    • aka heel of fire
    • part of fire with slower spread and lower intensity, usually moving into wind or downhill
  27. flaming front
    zone of moving fire where combustion is primarily flaming
  28. anchor point
    • location usually a barrier to spread from which to start constructing line
    • minimizes chance of being flanked
  29. fireline and control line
    • part of conrol line that is scraped to mineral soil
    • all constructted or natural barriers used to contain fire
  30. chain
    • unit of measure = 66 ft.
    • one mile is 80 chains
    • 10 chains is one acre
  31. south/southwest slopes
    • more exposed to sunlight
    • lighter sparser fuels, higher temp, lower RH, lower fuel moisture
  32. north facing slopes
    • have more shade
    • heavier fuels, lower temp, higher RH, higher fuel moisture
    • less fire activity than south facing slope
  33. slope
    • degree of incline on hillside
    • fire burns more rapidly uphill, steeper the slope the faster it burns
    • fire on level ground is influenced by wind and fuels
  34. saddle
     wind blowing through saddle can increase speed as it passes through constricted area and spreads out on downwind side
  35. barriers
    any obstruction to the spread of fire, an area or strip lacking any flammable fuel
  36. fuel loading
    • amount of fuel present
    • expressed in tons per acre
  37. fuel size classes
    • 1 hr fuels: 0-1/4 inch diameter
    • 10 hr fuels: 1/4-1 inch
    • 100 hr fuels: 1-3 inch
    • 1000 hr fuels: 3-8 inches
  38. air temperature
    degree of hottnes/coldness in the air
  39. relative humidity
    amount of moisture in the air divided by the amount the air could hold when saturated

    • temp increase- RH decreases
    • temp decrease- RH increases
  40. precipitation
    fine fuels react rapidly while heavy fuels are not drastically effected

    duration has more effect then amount of precipitation
  41. stable atmosphere
    • resists upward motion
    • clouds in layers
    • columns drift apart after limited rise
    • poor visibility
    • fog layers
    • steady winds
  42. wind direction
    the direction from which the wind is blowing, not where its blowing towards
Card Set
s-190 Wildland Fire Behavior
S-190 Wildland Fire Behavior