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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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Component 1
Component 1

Fuel-grass, shrub, timber litter, logging slash

01-02-S390-VG


Live fuel moisture

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
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


Fuel exposure to wind

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


Percent slope

RISE IN FEET

X 100 %

% SLOPE =

RUN IN FEET

PERCENT SLOPE

RISE

RUN

01-16-S390-VG



Assumptions of the fire spread model
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


Rate of spread distance time

TIME

RATE OF SPREADDISTANCE/TIME

ENDING

TIME

STARTING

TIME

DISTANCE

02-09-S390-VG


Flame length feet
FLAME LENGTHFEET

02-12-S390-VG


Point source
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 calculation sd pt x ros sd spread distance pt projection time ros rate of spread
SPREAD CALCULATIONSD=PT X ROSSD = SPREAD DISTANCEPT= PROJECTION TIMEROS = RATE OF SPREAD

02-16-S390-VG


Spread direction
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
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

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
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
AREAS OF USE SUPPRESSION OF…..

Determination of locations to place crews,

equipment, helicopters and fuel breaks.

Development of the wildland fire

situation analysis.

02-25-S390-VG


Prescribed burning
PRESCRIBED BURNING OF…..

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
EFFECTIVE WINDSPEED OF…..

The midflame adjusted for the effect

of slope on uphill fire spread.

02-37-S390-VG


Examples of effective windspeed
EXAMPLES OF EFFECTIVE WINDSPEED OF…..

3 mi/h

EFFECTIVE

WINDSPEED

IS 5 mi/h

60%

5 mi/h

02-38-S390-VG


Maximum spotting distance
MAXIMUM SPOTTING DISTANCE OF…..

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
SOURCES OF FIREBRAND OF…..

  • Torching trees

  • Burning pile

  • Spreading surface fire

02-44-S390-VG


Factors relating to the spotting problem
FACTORS RELATING TO THE SPOTTING PROBLEM OF…..

  • Probability of production of

  • firebrands.

  • Windspeed.

  • Fire intensity.

  • Number of firebrands

02-45-S390-VG


Dispatching priorities
Dispatching Priorities OF…..

FUELS

WEATHER

TOPOGRAPHY

03-05-S390-VG


Predicting real time fire behavior running surface fire wildland fire situation analysis wfsa
Predicting “Real Time” Fire Behavior OF…..Running Surface FireWildland Fire Situation Analysis(WFSA)

03-06-S390-VG


Prescribed burning1
Prescribed Burning OF…..

  • 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
FIRE PLANNING OF…..

  • Preattack

  • Describing consequences

  • Environmental documents

03-09-S390-VG


Rate of spread
Rate of Spread = OF…..

Spread Distance

Elapsed Time

03-28-S390-VG


Flame length
FLAME LENGTH* OF…..

Indicator of intensity

Observable

*Remember flame length is not equal

to flame height.

03-30-S390-VG


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