Fuels

Report
1. Weather
2. Fuels
Fire behavior largely determines fire
effects!
3. Topography
Fire behavior is largely determined by
which fuel strata is carrying the fire:
1. Ground
2. Surface
3. Ladder
4. Crown/ aerial

Ground Fuels
 Duff (partially decomposed)
 Peat
 Roots
 Stumps
litter
Duff
fermentation layer
humus
mineral soil

Surface Fuels
 Grasses
 Shrubs
 Litter (leaves)
 Woody debris
SURFACE AND GROUND FUELS

Aerial/ canopy Fuels
 Crown or canopy of
overstory

Ladder Fuels (located between
crown and surface fuels)
 Smaller trees
 Vines


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

Fuel Loading
Size and shape
Compaction
Chemistry
Arrangement
 Vertical
 Composition

Continuity
 horizontal

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
Fuel loading is simplified by categorizing
fuels into similar groups
All fuels are characterized by their size
category, called “timelag fuel class”. This is
related to their capacity to absorb and lose
water in relation to their environment.
The most important factor associated with
fuel size is its surface area to volume
ratio…why?

EMC = equilibrium moisture content: the watever vapor
pressure of the fuel is in equilibrium with the wvp of air.

Given a stable air mass, the “timelag” is time it takes for a
particle of fuel to reach 63% of the difference between its
initial moisture content and the equilibrium moisture
content.
It is NOT how long the fuel will burn


Difference
http://stream2.cma.gov.cn/pub/comet/FireWeather/S290Unit1
0FuelMoisture/comet/fire/s290/unit10/print.htm#page_2.2.0

It takes 5
timelags
for 95%
of the
change
to occur
But most
of the
change
happens
within
the first
timelag
http://stream2.cma.gov.cn/pub/comet/FireWeather/S290Unit10FuelMoisture/comet/fire/s290/unit10/prin
t.htm#page_2.2.0

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Size of fuel (diameter, inched) Timelag Class
0” to ¼”
1 hour
¼” to 1”
1o hour
1” to 3”
100 hour
> 3”
1000 hour
1.
2.
3.
Fuel models
Photo series
Measure it
Fuel Loading – what do you include?
Timber
Brush
Fire Ecology & Management
Feb. 22, 2008
Fuel Models and
Fire Behavior Prediction
Anderson, 1982
Rate of spread (meters / minute)
Rate of Spread for Fuel models at 5 mph wind
FuelM 1
FuelM 2
FuelM 5
FuelM 8
FuelM 9
FuelM 10
FuelM 11
100.0
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0
10
20
Slope (degrees)
30
40
FUEL MODEL 13: HEAVY LOGGING SLASH
6-10 tons/ acre
FUEL MODEL 7: SOUTHERN ROUGH
3-5 tons/acre
FUEL MODEL 8: CLOSED TIMBER LITTER
1-3 tons/acre
FUEL MODEL 3: TALL GRASS

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
Hundreds of field plots measured= averaged
= photo series fuel loading values.
Digital photo series (USFS)
http://depts.washington.edu/nwfire/dps/

Brown’s Planar Intercept

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