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Wildland Fire Behavior
Component 1
Fuel-grass, shrub, timber litter, logging slash
01-02-S390-VG
LIVE FUEL MOISTURE
01-10-S390-VG
STAGE OF VEGETATIVE DEVELOPMENT________________________________________
Fresh foliage, annuals developing early in growing cycle.
Maturing foliage, still developing with full turgor.
Mature foliage, new growth complete and comparable to older perennial foliage.
Entering dormancy, coloration starting, some leaves may have dropped from stem.
Completely cured.
MOISTURE CONTENT
Percent300
200
100
50
Less than 30, treat as a dead fuel.
PROBABILITY OF IGNITION
01-11-S390-VG
A rating of the probability that a glowing firebrand will cause a fire.
Wind
10 mi/h
20 mi/h
3 mi/h
20 mi/h
01-13-S390-VG
Fuel exposure to windFuel exposure to wind
Partly shelteredPartly sheltered(patchy timber)(patchy timber)
WindWind
Unsheltered (no foliage, Unsheltered (no foliage, near clearings)near clearings)
Fully shelteredFully sheltered(under timber,(under timber,flat or gentle flat or gentle slope, near baseslope, near baseof steep mtn.)of steep mtn.)
Partly shelteredPartly sheltered(under timber(under timbermidslope, windmidslope, windon slope)on slope)
UnshelteredUnsheltered(ridgetops)(ridgetops)
01-14-S390-VG
PERCENT SLOPE
01-16-S390-VG
% SLOPE = RISE IN FEETRUN IN FEET
X 100 %
RISE
RUN
A MATHEMATICAL MODEL IS A SET OF
EQUATIONS
02-04-S390-VG
ASSUMPTIONS OF THE FIRE SPREAD MODEL
02-05-S390-VG
1. Fire is spreading at the flame front.
2. Fire is free burning.
3. Fine fuels control rate of spread.
4. Uniform and continuous fuels.
5. Surface fire.
6. Uniform weather and topography.
RATE OF SPREADDISTANCE/TIME
02-09-S390-VG
STARTING TIME
TIME
ENDING TIME
DISTANCE
FLAME LENGTHFEET
02-12-S390-VG
POINT SOURCE
02-15-S390-VG
Point source model is designated for firesburning on flat ground or where the wind is blowing in the direction of the slope plus
or minus 30°.
upslope
max
slop
e
± 30º
SPREAD CALCULATION
SD=PT X ROS
SD = SPREAD DISTANCEPT= PROJECTION TIMEROS = RATE OF SPREAD
02-16-S390-VG
SPREAD DIRECTION
02-18-S390-VG
WIN
D
NO
WIN
D
WIN
DUP
SLOPEUP
SLOPEUP
SLOPE
WIN
D
DOWN SLOPE
DOWN SLOPE
DOWN SLOPE
POINT SOURCE PREDICTION LIMITATIONS
02-21-S390-VG
Calculations with windspeeds less than 2.5 miles per hour are generally too low.
Better predictions result withwindspeeds greater than 2.5 milesper hour.
FIRE PERIMETER AND SHAPES
02-23-S390-VG
Fire perimeter and shapes are based on smooth ellipses - actual perimeter of the fire edge would likely be greater length and follow topographic relief.
APPROXIMATE FIRE SHAPES ASSOCIATED WITH MIDFLAME
WINDSPEEDS OF…..
02-24-S390-VG
Wind Direction
Fire Start
2.5 mi/h
5 mi/h
7.5 mi/h
15 mi/h
10 mi/h
AREAS OF USE SUPPRESSION
02-25-S390-VG
Determination of locations to place crews,equipment, helicopters and fuel breaks.
Development of the wildland fire situation analysis.
PRESCRIBED BURNING
02-27-S390-VG
Distance between spot fires to accomplishan objective.
Calculating timing of ignition to take advantage of diurnal weather patterns.
Managing wilderness fires.
Development of escaped fire contingencyplanning.
EFFECTIVE WINDSPEED
02-37-S390-VG
The midflame adjusted for the effectof slope on uphill fire spread.
EXAMPLES OF EFFECTIVE WINDSPEED
02-38-S390-VG
EFFECTIVE WINDSPEEDIS 5 mi/h
3 mi/h
60%5 mi/h
MAXIMUM SPOTTING DISTANCE
02-43-S390-VG
When torching trees, piles or wind-driven surface fires loft firebrands,which are then carried by the prevailing wind.
SOURCES OF FIREBRAND
02-44-S390-VG
•Torching trees
•Burning pile
•Spreading surface fire
FACTORS RELATING TO THE SPOTTING PROBLEM
02-45-S390-VG
•Probability of production of firebrands.
•Windspeed.
•Fire intensity.
•Number of firebrands
Dispatching Priorities
03-05-S390-VG
FUELSWEATHER
TOPOGRAPHY
Predicting “Real Time” Fire Behavior
Running Surface Fire
Wildland Fire Situation Analysis(WFSA)
03-06-S390-VG
Prescribed Burning
03-07-S390-VG
•Estimate the behavior of escapes or spots.
•Assess fuel and weather conditions at burn time.
•Develop burn prescriptions.
•Develop containment and control plans.
FIRE PLANNING
03-09-S390-VG
•Preattack
•Describing consequences
•Environmental documents
Rate of Spread =
03-28-S390-VG
Spread DistanceElapsed Time
FLAME LENGTH*
03-30-S390-VG
Indicator of intensity
Observable
*Remember flame length is not equal to flame height.