Understanding Fire Behavior The Key to Effective Fuels Management

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Understanding Fire Behavior The Key to
Effective Fuels Management Marty Alexander, PhD,
RPF Sr. Fire Behavior Research Officer Canadian
Forest Service Northern Forestry Centre Edmonton,
AB FERIC Sponsored Fuels Management
Workshop Hinton Training Centre, Hinton,
AB October 6-8, 2003
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FUELS MANAGEMENT
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... further major advances in combating wildfire
are unlikely to be achieved simply by continued
application of the traditional methods. What is
required is a more fundamental approach which can
be applied at the design stage Such an
approach requires a detailed understanding of
fire behaviour ... Drysdale (1985)
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Are these realistic solutions to the wildfire
problem?
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What is Fuels Management? Fuels management is
the planned manipulation and/or reduction of
living or dead forest fuels for forest management
and other land use objectives (e.g., hazard
reduction, silvicultural purposes, wildlife
habitat improvement) by - prescribed fire -
mechanical means - chemical means - biological
means - changing stand structure and
species composition
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What is the Basic Premise Behind Fuels
Management? We cannot really do much to control
the weather or reshape the topography but we can
and of influence the quantity and character of
wildland fuels.
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What is the Purpose of Fuels Management? The
goal is to proactively lessen the potential fire
behavior and thereby increase the probability of
successful containment and minimize adverse
impacts. More specifically, it's to decrease
the rate of fire spread and in turn fire size and
intensity as well as crowning and spotting
potential.
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FIRE PREVENTION
A new dimension in

• WEATHER MODIFICATION
• WEATHER PREDICTION
• WEATHER PATTERNS

• FUEL MANAGEMENT
• LAND USE PLANNING
• LAND USE MANAGEMENT

FIRE TRIANGLE
FUEL
AIR
HEAT

• EDUCATION SMOKEY BEAR PEOPLE CONTACTS
• CLOSURES LAW ENFORCEMENT

From Anon. (1973)
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Fuels management can be accomplished by three
principal means

• Reduction Manipulation
• Conversion
• Isolation

Pyne et al. (1996)
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Fuel Reduction The fuel load is decreased
and/or the vertical fuel arrangement is altered
Campgrounds where fireproofed in the early 1900s
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Burning of logging slash was a common practice in
the past
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Some forest types lend themselves to prescribed
underburning
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Factors to Consider When Deciding How Much Fuel
is Acceptable
MANAGEMENT OBJECTIVES
VALUES AT RISK
DECISION
OTHER FIRE FACTORS SURROUNDING FUELS SUPPRESSION
CAPABILITY FIRE HISTORY FIRES ROLE
From Brown et al. (1977)
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Stand-replacing prescribed crown fires may be the
only viable option in some northern boreal forest
types
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(No Transcript)
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Fuel reduction can be achieved through livestock
grazing
Heavily Grazed
Lightly Grazed
From Davis (1949)
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Davis (1949) Heavily vs. Lightly Grazed
Study Two plots 30 x 150 m ignited
simultaneously Lightly Grazed ROS 28.5 m/min
1.5 m Flame Height Heavily Grazed ROS 9.7
m/min 0.3 m Flame Height
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Pruning and thinning are commonly advocated for
reducing crown fire potential
Graham et al. (1999)
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Semi-theoretical comparison of fire behavior in
pruned exotic pine plantations under high fire
danger conditions as patterned after McArthurs
(1965) analysis
Stand A
(pruned up to 5m)
Surface
300
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2700
2
4.86
a
a
0.83
b
b
lt200
a theoretically, approximately 9 and 45 of the
total perimeter would have fire intensities
exceeding 2000kW/m(Catchpole et al. 1992) thereby
precluding direct attack by conventional means. b
After Douglas (1974)
(from Alexander 1992)
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This stand was pruned at age 20 years. Live crown
are safely above heavy accumulation of needle
litter below
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Alexander (1988)
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Before
Schmidt and Wakimoto (1988)
After
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(No Transcript)
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(from Alexander 1998)
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Continuous crown fire spread
Intermittent crowning
Surface fire spread
Alexander (1998)
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Thinnings in general will lower crown bulk
densities and redistribute fuel loads
significantly, thus decreasing fire intensities
if the surface fuels are treated ... these
removals have been shown to be effective in
reducing crown fire potential ... Because of
drier fuels ... and increased wind speeds that
occur in thinned stands, it is critical that they
be treated to minimize fire intensity. Graham et
al. (1999)
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International Crown Fire Modelling Experiment
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Fuel Conversion fuels are replaced by less
flammable ones
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Are Crown Fires in Aspen Possible?
2001 Duffield Fire, Central Alberta
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Crown fire in black spruce
Aspen forest
Willow River, Northwest Territories, 1979
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Aspen stands are still subject to low- to
moderate intensity surface fires in the spring
and fall.
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Unfortunately most communities under go "fuel
conversion" from unplanned fire events!
Immediately after the fire
Present day
1969 Faro Fire, Yukon
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Fuel Isolation large expanses of fuels are
broken up with firebreaks and fuelbreaks
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Grass Firebreak Breaching
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What is a Fuelbreak? A fuelbreak is "An existing
barrier or change in fuel type (to one that is
less flammable than that surrounding it), or a
wide strip of land on which the native vegetation
has been modified or cleared, that act as a
buffer to fire spread so that fires burning into
them can be more readily controlled. Often
selected or constructed to protect a high value
area from fire. In the event of fire, may serve
as a control line from which to carry out
suppression operations." (Merrill and Alexander
1987)
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This is NOT a Fuelbreak!
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Norman Wells, Northwest Territories, 1995
Fireguard construction with bulldozers on
permafrost
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Conflagration Barrier An Elaborate Fuelbreak
Design
Green and Schimke (1971)
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Green's (1977) publication constitutes a major
summary of past research and operational
experience.
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Research and Operational Experience Suggests that
"Aspen Fuelbreaks" Offer a Viable Option in Many
Areas of the Boreal Forest
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Fort Providence, Northwest Territories
Firebreak/Fuelbreak
Mackenzie River
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Firebreak/Fuelbreak
Watson Lake, Yukon
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Plot 5 - July 4, 1997
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Spot Fires Breaching Fireguard Downwind of a
ICFME Experimental Fire
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Significant tradeoffs between available
fuelbreaks options, including positive and
negative attributes
OPTION
Positives
Negatives
Nature takes over
Live with wildfires
I. Cease construction and maintenance
Simplicity
Could lose big
II. Maintain established performers only
Increase options
Requires hard work
III. Manage landscapes using fuel breaks where
appropriate
From Omi (1996b)
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Theoretical analysis of landscape-scale fuel
management considerations suggest that fuel
treatments need to be strategically placed.
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Width of Barrier to Fire Spread
30
1000 m
of area treated
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300 m
10
200 m
100 m
0
0
2000
4000
6000
8000
10 000
Limit of single fire area (ha)
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Is Fuels Management Needed? On some days adverse
fuel and weather conditions coupled with an
ignition conspire to produce conflagrations that
are impossible to contain until burning
conditions ameliorate.
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The stakes are high!
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(No Transcript)
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Fire managers are now publicly acknowledging that
they need fuels management to assist them in
controlling wildfires in the future.
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This publication by C.M. Countryman is a
fundamental piece of work on fuels management.
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In southern California, many fires start and burn
under conditions that permit their control with
little burned acreage and fire damage. In
contrast, under other conditions of weather
topography, on a small group of fires, control is
relatively ineffective they become large and
destructive. A major reason for these
"conflagration fires" is the extreme difficulty
of stopping the head of a hot, fast-running fire
in dry fuels and strong winds. No radically new
concept of suppression can be anticipated. The
best prospect for alleviation of the problem is
modification of the vegetation to reduce fuel
energy output. In a fuel-type mosaic containing
large areas of light fuels, where conventional
suppression will be effective, potential
conflagrations could be brought under control
while relatively small. Creation of the
fuel-type mosaic will require coordinated
area-by-area planning and a variety of
techniques. Countryman (1974)
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Forest Management and Other Land Use Practices
Need to Consider Implications for Fire Suppression
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Will fuels management make fire suppression more
effective?
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Can Fuels Management be Effective?
1983 Ash Wednesday Fires, South Australia
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• Methods of Judging the Effectiveness
• (or Limitations) of Fuels Management
• Experienced Judgment
• Expert Opinion
• Wildfire Case Studies
• Mathematical Model Simulations
• Outdoor Experimental Fires

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Conceptual Model of Scientifically-based Forest
Fire Management
FIRE BEHAVIOR
FIRE IMPACTS
FIRE IGNITION

• Ease of ignition
• Probability of sustained flaming ignition
• Probability of sustained smoldering ignition
• Probability of x number of lightning fires
• Probability of x number of human-caused fires

• Scorch height
• Defoliation height
• Stem mortality
• Stem damage
• Soil heating
• Depth of burn
• Mineral soil exposure
• duff reduction
• Tree mortality
• etc.

• Rate of spread
• Fire intensity
• Flame height
• Flame length
• Flame depth
• Residence time
• Burn-out time
• Fire shape growth
• Fire acceleration
• Fuel consumption
• Spotting distance
• etc.

FIRE MODELS OUTPUTS
MANAGEMENT APPLICATIONS
FORECASTING FIRE DANGER
CONTROLLING WILDFIRES
PRESCRIBED BURNING
EVALUATING ECOLOGICAL EFFECTS
FUELS MANAGEMENT
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Rothermel (1991) Model vs. ICFME Results
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e.g., ICFME Treated/Untreated Plot - burnt June
14, 2000
U N T R E A T E D
T R E A T E D
IGNITION FACE

• Limitations
• Plot face exposure problem (fuel moisture)
• Subject to shift in wind direction after
  ignition
• Question of one half influencing the other

• Strengths
• Any differences should be readily apparent
• Lull in wind speed not a problem

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e.g., ICFME Plot C established June 2001
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e.g., New NWT Community Fire Protection Fuel
Treatment Effectiveness Experiment plots
Untreated
IGNITION FACE
IGNITION FACE
IGNITION FACE
Simultaneous Ignitions

• Strengths
• Lull in wind speed not a problem
• Provides direct evidence of treatment effect

• Limitation
• Subject to shift in wind direction after ignition

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ECONOMICS OF FUELS MANAGEMENT
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Aesthetics of Fuels Management
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Framework for Assessing the Impact of
Landscape-scale Fuels Management vs. Status Quo
Fire effects
Landscape effects
Fire regime, frequency, severity, size
Suppression efforts
Policy evaluation (including assessment of
risks, hazards and values)
Socio-economic evaluation
Manipulate landscape fuels
Status quo
No
from Omi (1996a)
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THE END QUESTIONS?
Natural Resources Canada Canadian Forest Service
Ressources naturelles Canada Service canadien des
forêts