Interpreting Fire Behavior

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Interpreting Fire Behavior

• National Interagency Fuels Technology Team

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Objectives

• Review of applications of surface canopy fuel
  characteristics
• Relate fuel characteristics to fire behavior
  interpretations
• Understand and apply characteristics of surface,
  crown, and torching fire behavior
• Assess differences in fire behavior fuel model 13
  system for treatment design
• Conduct logical checks on fire behavior and FRCC
  input data to assure consistency

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• Fire Behavior
• Fire Behavior Fuel model (FBFM) surface fire
• - 13 Anderson
• - 40 Scott Burgan
• - custom fuel models
• Canopy cover (CC) wind, fuel moisture
• Canopy height (CH) torching/spotting
• Canopy base height (CBH) crown fire
  transition
• Canopy bulk density (CBD) crown fire spread
• Canopy foliar moisture crown fire spread
• Existing vegetation type (EVT)
  torching/spotting

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Fuel Model

• Fuel loading - dead
• 1 hour (0-1/4 in), 10 hour (1/4-1 in), 100 hour
  (1-3 in)
• Fuel loading live
• Live herbaceous, live woody
• Surface-to-volume ratio (1/cubic volume)
• Fuel bed depth
• Moisture of extinction -
• Heat content live dead fuels
• Used to predict surface fire behavior

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Fuel Model
10- timber with dead down fuels
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Canopy Characteristics

• Canopy cover
• Canopy height
• Canopy base height
• Canopy bulk density
• Foliar moisture

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Canopy Cover

• Used to predict shading effects foliar moisture
  content (more cover higher moisture reduced
  surface fire behavior)
• Used for adjusting wind reduction factor (more
  cover higher wind reduction reduced surface
  fire behavior)

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Canopy Cover
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Canopy Height

• Used in predicting embers
• Used in wind reduction factor
• Used in volume of crown fuels

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Canopy Height
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Canopy Base Height

• Height to the base of the live canopy
• Incorporates ladder fuels (dead branches, lichen,
  regeneration)
• Average lowest height above the ground to
  propagate a fire vertically through the canopy

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Canopy Base Height
1 meter
4 meters
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Canopy Base Height
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Canopy Base Height
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Canopy Bulk Density

• Estimate of canopy fuels consumed in the flaming
  front of an active crown fire
• Effective CBD from plot characteristics
• Does not assume uniform tree distribution
• Maximum 4.5 m (15 ft) running mean
• Same as used for FVS-FFE
• Stereo photo guide to adjust Scott Reinhardt
  (2005)

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Canopy Bulk Density

• Tree species (higher for short needle shade
  tolerant)

.20 kg/cu-m
.01 kg/cu-m
.06 kg/cu-m
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Foliar Moisture

• Short needle shade tolerant, fire intolerant
  species 75-100 in dry conditions
• Long needle shade intolerant, fire tolerant
  species 100 150 in dry conditions
• Default of 100

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Foliar Moisture

• Opening the canopy can reduce foliar moisture
• Short needle, fire intolerant species reduce
  foliar moisture

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Fire Behavior

• Function of surface fire spread
• Transition to crown fire
• Crown fire spread conditional, passive, active

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Surface Fire
Some basic rules of thumb to help in design
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Surface Fire
Some basic rules of thumb to help in design

• Fireline intensity heat release in flaming
  front
• function (fuel heat per unit area, rate of
  spread, moisture/temperature)
• Rate of spread rate of movement of flaming
  front
• function (fuelbed reaction intensity, wind,
  slope, fuelbed bulk density, heat of preignition)

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Crown Fire
Some basic rules of thumb to help in design
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Crown Fire
Some basic rules of thumb to help in design

• Initiation
• Function (CBH, FMC)
• Crown fire spread
• Crown spread rate function (FM 10 surface) fire
  rate w/ midflame windspeed _at_ 40 of 6.1 m (20 ft)
  wind speed
• Active crown fire function crown spread rate gt
  (3.0/CBD)

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Crown Fire
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Spotting
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Spotting
Some basic rules of thumb to help in design

• Can greatly increase rate of fire perimeter
  expansion (surface or crown)
• Function of
• Stand height higher lofting
• Tree species embers production
• Species tolerance more embers
• Species diameter more embers lofting

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Fuels Fire Behavior Hazard - Example
Canopy Bulk Density
Moderate
Low
High
100
Low
High 3, 4, 10, 11-13
High Index 70
H
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Moderate
Moderate 1, 5, 6, 7, 9
Fire Behavior Surface FM - Intensity
Canopy Closure/FMC
M
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L
Mod-High
Low 2, 8
0
Low
Moderate
High
Canopy Base Height
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Fuels Fire Behavior Hazard - Example
Canopy Bulk Density
Moderate
Low
High
100
Low
High 3, 4, 10, 11-13
H
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Moderate
Moderate 1, 5, 6, 7, 9
Fire Behavior Surface FM - Intensity
Canopy Closure/FMC
M
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L
Mod-High
Low 2, 8
0
Low
Moderate
High
Canopy Base Height
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Color Country rules of thumb
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Wind Speed 30 mph _at_ 20 ft flame height
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NEXUS
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NEXUS
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NEXUS
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NEXUS
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Fuel Models
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Integrating Fuels With FRCC Inputs

• rectification

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• Fire Regime Condition Class (FRCC)
• There are obvious overlaps between FRCC, Fire
  Behavior/Effects input characteristics, and basic
  vegetation characteristics
• Identify characteristics common to Fire
  Behavior/Effects model inputs, FRCC inputs, and
  basic vegetation characteristics
• Integrate treatment development and inputs to
  assure logical relationships

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• Fire Regime Condition Class (FRCC)
• BioPhysical Setting (BPS) reference
  conditions
• Succession Class (SC) canopy cover, height,
  existing vegetation type, species composition
• Interrelationships
• Logic relationships between characteristics
• illogical treatment to create fuel model 2
  leave succession class as closed mid-seral

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Fire Behavior Fire Behavior Fuel model (FBFM)
Canopy cover (CC) Canopy height (CH) Canopy
base height (CBH) Canopy bulk density (CBD)
Existing vegetation type (EVT) - species Fire
Regime Condition Class (FRCC) BioPhysical
Setting (BPS) kind of site, native species
Succession Class (SC) species, canopy cover,
height, size Existing vegetation type (EVT)
species
Interrelationships Relationships between
characteristics
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Interrelationships
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Objectives

• Review of applications of surface canopy fuel
  characteristics
• Relate fuel characteristics to fire behavior
  interpretations
• Understand and apply characteristics of surface,
  crown, and torching fire behavior
• Assess differences in fire behavior fuel model 13
  system for treatment design
• Conduct logical checks on fire behavior and FRCC
  input data to assure consistency

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Common Questions
Fuels and Fire Behavior Modeling
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Problem Fire Characterization

• Threat to Urban Interface
• Large Fire Threat
• Fire Effects
• Uncharacteristic (FRCC)
• Soil, water
• Smoke
• ..

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Problem Fire Characterization

• Calibrating FBAT (FlamMap)
• Fire Weather (primarily wind speed)
• Rate of Spread
• Flame Lengths
• Crown Fire Activity
• Fuel Characteristics

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Fire Family Plus
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1 Hr Fuel Moisture
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Pocket Cards
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Fire Occurrence
1988
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Fire Occurrence
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Calibrating for FBAT/FlamMap

• Wildfire Potential Hazard Scenario
• Static upslope wind direction
• Static 98th percentile severe weather
• (1, 10, 100 hr, live herbaceous woody)
• No change in weather
• Adjust wind to produce recorded fire behavior in
  these types of conditions

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Fire Behavior Assessment Tool Absolute FB Class
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Calibrating for FARSITE

• Wildfire Hazard Scenario
• Daily recorded weather of problem incident
• (dead and live fuel moisture)
• Or 98th percentile or other scenario
• Upslope winds
• Variable daily temperature, humidity
• Adjust to produce recorded fire behavior in these
  types of conditions

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Calibrating for FARSITE

• Wildfire Hazard Scenario
• Daily recorded weather of problem incident
• (dead and live fuel moisture)
• Or 98th percentile or other scenario
• Variable hourly wind direction speed
• Variable daily temperature, humidity
• Adjust to produce recorded fire behavior in these
  types of conditions

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hours of boredom interspersed with seconds of
pure panic