Wildland fire behavior
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Wildland Fire Behavior. Component 1. Fuel-grass, shrub, timber litter, logging slash. 01-02-S390-VG. STAGE OF VEGETATIVE DEVELOPMENT ________________________________________ Fresh foliage, annuals developing early in growing cycle. Maturing foliage, still developing with full turgor.

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Wildland Fire Behavior

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Wildland Fire Behavior


Component 1

Fuel-grass, shrub, timber litter, logging slash

01-02-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

Percent

300

200

100

50

Less than 30, treat as a dead fuel.

LIVE FUEL MOISTURE

01-10-S390-VG


PROBABILITY OF IGNITION

A rating of the probability that a

glowing firebrand will cause a fire.

01-11-S390-VG


Wind

20 mi/h

20 mi/h

10 mi/h

3 mi/h

01-13-S390-VG


Unsheltered

(ridgetops)

Fuel exposure to wind

Wind

Partly sheltered

(under timber

midslope, wind

on slope)

Partly sheltered

(patchy timber)

Fully sheltered

(under timber,

flat or gentle

slope, near base

of steep mtn.)

Unsheltered (no foliage,

near clearings)

01-14-S390-VG


RISE IN FEET

X 100 %

% SLOPE =

RUN IN FEET

PERCENT SLOPE

RISE

RUN

01-16-S390-VG


A MATHEMATICAL MODEL IS A SET OF EQUATIONS

02-04-S390-VG


ASSUMPTIONS OF THE FIRE SPREAD MODEL

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.

02-05-S390-VG


TIME

RATE OF SPREADDISTANCE/TIME

ENDING

TIME

STARTING

TIME

DISTANCE

02-09-S390-VG


FLAME LENGTHFEET

02-12-S390-VG


POINT SOURCE

Point source model is designated for fires

burning on flat ground or where the wind

is blowing in the direction of the slope plus

or minus 30°.

upslope

slope

max

± 30º

02-15-S390-VG


SPREAD CALCULATIONSD=PT X ROSSD = SPREAD DISTANCEPT= PROJECTION TIMEROS = RATE OF SPREAD

02-16-S390-VG


SPREAD DIRECTION

UP

SLOPE

UP

SLOPE

UP

SLOPE

NO WIND

WIND

WIND

WIND

DOWN

SLOPE

DOWN

SLOPE

DOWN

SLOPE

02-18-S390-VG


POINT SOURCE PREDICTION LIMITATIONS

Calculations with windspeeds less than

2.5 miles per hour are generally too low.

Better predictions result with

windspeeds greater than 2.5 miles

per hour.

02-21-S390-VG


FIRE PERIMETER AND SHAPES

Fire perimeter and shapes are based on

smooth ellipses - actual perimeter of

the fire edge would likely be greater

length and follow topographic relief.

02-23-S390-VG


APPROXIMATE FIRE SHAPES ASSOCIATED WITH MIDFLAME WINDSPEEDS OF…..

Wind Direction

Fire Start

7.5 mi/h

2.5 mi/h

10 mi/h

15 mi/h

5 mi/h

02-24-S390-VG


AREAS OF USE SUPPRESSION

Determination of locations to place crews,

equipment, helicopters and fuel breaks.

Development of the wildland fire

situation analysis.

02-25-S390-VG


PRESCRIBED BURNING

Distance between spot fires to accomplish

an objective.

Calculating timing of ignition to take

advantage of diurnal weather patterns.

Managing wilderness fires.

Development of escaped fire contingency

planning.

02-27-S390-VG


EFFECTIVE WINDSPEED

The midflame adjusted for the effect

of slope on uphill fire spread.

02-37-S390-VG


EXAMPLES OF EFFECTIVE WINDSPEED

3 mi/h

EFFECTIVE

WINDSPEED

IS 5 mi/h

60%

5 mi/h

02-38-S390-VG


MAXIMUM SPOTTING DISTANCE

When torching trees, piles or wind-

driven surface fires loft firebrands,

which are then carried by the

prevailing wind.

02-43-S390-VG


SOURCES OF FIREBRAND

  • Torching trees

  • Burning pile

  • Spreading surface fire

02-44-S390-VG


FACTORS RELATING TO THE SPOTTING PROBLEM

  • Probability of production of

  • firebrands.

  • Windspeed.

  • Fire intensity.

  • Number of firebrands

02-45-S390-VG


Dispatching Priorities

FUELS

WEATHER

TOPOGRAPHY

03-05-S390-VG


Predicting “Real Time” Fire BehaviorRunning Surface FireWildland Fire Situation Analysis(WFSA)

03-06-S390-VG


Prescribed Burning

  • Estimate the behavior of escapes or spots.

  • Assess fuel and weather conditions at burn time.

  • Develop burn prescriptions.

  • Develop containment and control plans.

03-07-S390-VG


FIRE PLANNING

  • Preattack

  • Describing consequences

  • Environmental documents

03-09-S390-VG


Rate of Spread =

Spread Distance

Elapsed Time

03-28-S390-VG


FLAME LENGTH*

Indicator of intensity

Observable

*Remember flame length is not equal

to flame height.

03-30-S390-VG


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