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Wildfires

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Title: Wildfires


1
Wildfires
2
  • Wildland Fires are a natural part of the
    evolution and renewal of nature. It is necessary
    for healthy rangelands and forests.
  • Ecosystems benefit by
  • Thinning forests
  • Reducing understory fuel
  • Permitting growth of some species of trees

3
Years of Fire Suppression Beginning in 1910
after a large fire, wildland fires were put out
as soon as possible. The campaign against forest
fires has long been recognized by the icon Smoky
Bear. Smoky Bears Birthday 9 Aug 1944
1985 Fire suppression campaign
4
  • Many years of fire suppression have led to
  • Increased fuels
  • Higher density, unhealthy forests

5
So do we fight fires or let them burn? In the
1990s, the policy changed to permit fires to
burn in uninhabited wilderness areas.
6
Fires have been increasing problematic as urban
areas encroach upon the forests. The danger to
human lives and property is increasing
dramatically.
7
What is happening during a wildfire? Trees burn
at a high temperature by the reaction with oxygen
in the air. Cellulose the main combustible
part of wood is which breaks down to carbon,
water and heat. Some plants also contain natural
oils or saps that add to the combustibles.
8
Grasses, shrubs and litter burn easier, thus more
quickly. A ground fire may move through fast
enough to clear the understory but spare the
trees.
9
Some species of trees (Ponderosa Pine) have
evolved through time to survive ground fires and
even need them to reproduce.
10
  • What does a fire need?
  • A fire requires 3 components
  • Fuel
  • Oxygen
  • Heat
  • and cannot progress without all three

11
Healthy versus destructive fires A fire in a
healthy forest will burn the ground cover and not
the trees.
12
Where fire can easily reach up from the ground
vegetation through lower tree branches it may
crown forming a destructive fire called a crown
fire. Crown fire a fire that burns the upper
part of a tree, which includes the branches and
leaves.
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14
Once a fire crowns, wind can carry the embers
more than a kilometer causing spot fires.
Biscuit Fire
15
Spot fire a small fire started when flames from
a crown fire are blown into a non-burning part of
the forest.
Spot fire on Trail Creek, MT on 1 August 2003
16
  • Factors that affect fire behavior
  • Fuel
  • Weather
  • Topography

17
1. Fuel the amount of burnable vegetation
(natural or brought in by people)
18
  • 2. Weather 2 important factors
  • Wind
  • Humidity ( Temperature)
  • Winds accelerate fires by
  • Move them downwind.
  • Directing the flames at new fuels
  • Bringing in new oxygen
  • Carrying embers (up to more than a kilometer)
    causing spot fires

Tuolumne Fire, Stanislaus NF, CA, September 2004
19
  • Humidity
  • Directly affects fuel moisture
  • The lower the humidity, the drier the fuel
  • (increase temperature, decrease RH)
  • The drier the fuel, the greater the fire danger

20
Fuel dryness is dependent on the size of the
fuel. If vegetation is completely saturated,
the time it takes to dry out to 63 of its
moisture (or vice versa) can be calculated.
1000 hour fuels gt8 in diameter (e.g. pine
trees)
What does this mean? If a Ponderosa Pine is
dried out from a drought it may take over a month
for water to saturate the trunks. Thus, the fire
danger is NOT eliminated after one rain storm.
21
100 hour fuels 3-8 in diameter
22
10 hour fuels lt3 in diameter 1 hour fuels are
grasses and twigs
23
Haines Index is used to indicate the potential
for wildfire growth by measuring the stability
and dryness of the air over a fire.
24
Palmer Drought Index (PDI) maps show long-term
(cumulative) meteorological drought and wet
conditions.
25
From these data, the fire danger for any given
time period can be predicted. This enables fire
officials to hire and disperse crews to areas
with the highest fire danger.
26
Fires can generate their own weather Convective
updraft of heat from a fire draws in new air from
the sides of the fire helping to fan the flames.
These winds can easily reach 60mph.
27
Firestorm forms when a fires own winds rush air
in to replace the air rising convectively This
is caused by high winds /or extremely dry fuel.
28
3. Topography shape of the land a. Flames and
sparks rise with heat promoting upslope movement
of fires into new fuel. Thus fires move rapidly
upslope but not downslope.
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b. Canyons can funnel air as a chimney and cause
more rapid spreading.
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Fire Suppression and Prevention
34
  • What does a fire need?
  • If one of the components in the fire triangle is
    removed, the fire is no longer able to burn.
  • Fuel clear the forest
  • Oxygen
  • Heat water

35
Wildland fires are fought from the ground and the
air, with several specialized crews  hotshots,
smokejumpers and helitack  all contributing to
the frontline assault.
36
1. Smokejumpers parachute from planes to attack
wildland fires in remote and inaccessible areas
to get to a small fire before it spreads. There
are only 400 smokejumpers in the US.
Smokejumper recruits are boarding a CASA 212 twin
engine turbo-prop plane for their first jumps at
the North Cascades Smokejumper Base in Winthrop,
Wash
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38
2. Hotshot Crews these specialized crews are
assigned to the most remote and difficult
sections of wildland blazes.
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40
They are often the first into a fire, hiking many
miles to get there.
41
A Hotshot Crew can dig ¼ of a mile of fire line
in an hour.
42
  • Type 2 crews come in later and cut fire lines
  • Fireline a fire control line formed by removing
    surface litter and organic matter to expose
    mineral soil. The width of a line must be 1½
    times the fire height.

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45
Bulldozers cut firebreaks to remove the
vegetation to bare ground
46
4. Helitack crews support firefighters on the
ground by dropping water, foam or retardant on
flaming trees, brush and even structures to cool
hot spots and prevent a fire from spreading.
47
Helitack crews can be rapidly deployed and are
often the first to respond to a wildland fire.
They are also trained to rappel from a hovering
helicopter and their primary job is to load and
unload slings of equipment and supplies.
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49
5. Air tankers - Aircraft drop loads of fire
retardant along lateral and advancing edges.
50
Tuolumne Fire, Stanislaus NF, CA, September 2004
51
6. Burnout a small area in the path of a big
fire is burned under controlled conditions and
suitable weather, generally near a road or a
river. The goal is to remove fuels in the path
of the fire. A burnout on Jul 2003 this saved
the town of West Glacier.
52
Burnout, CA 2007
53
7. Setting BackfiresBackfires are used for
rapidly spreading fires. The tactic involves
burning an area ahead of the main fire.
Backburn, Biscuit Fire
54
It is set next to a road or a facility to burn
back to the main fire the convective rise of hot
air in the main fire draws the new flames to it.
The goal is to 1.) Eliminate fuel in advance of
the fire, widening the control line, 
      2.) Change the direction of the fire, 
      3.) Slow the fire's progress. 
55
Tuolumne Fire, Stanislaus NF, CA, September 2004
56
Backburn, Canada
57
Mopup Hot Spots Embers can burn underground,
especially in tree root systems, long after a
fire has stopped spreading. Firefighters must
search out these hot spots and ensure they are
extinguished before they flare up.
58
CrewSafety
Old Fire, 2003 (Southern CA)
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Moose Fire, MT 2001
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63
Effect of Urban Interface
Just east of Okanagan Lake, Kelowna, BC 20 Aug
2003
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65
Cedar Fire, 2003 (San Diego area, Southern CA)
66
Aerial tanker drops water on the edge of an Idaho
fire in Aug 1996. Note the house is upslope
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69
Minimizing fire danger around the home
A good example of a house saved by intelligent
firewise practices.
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71
Many homes were destroyed in the Cedar Fire, just
east of San Diego, CA
72
Gap Fire, 05
73
Gap Fire, 05
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Fence Fire 02
77
Fence Fire 02
78
Fence Fire 02
79
Fence Fire 02
80
Prescribed burns
Prescribed fire is a carefully planned and
controlled fire conducted to manage fuels and
forest health in timber, brush and oak woodland
vegetation types. It is conducted only under
safety standards that define rigid windows of
opportunity where weather conditions are
appropriate and firefighting resources are
readily available.
81
Cerro Grande fire near Los Alamos NM, a
prescribed burn that got out of control
82
Cause of Wildland Fires National Averages
83
Michigan
84
Total Acres burned in 2007 1,087,110 (Only ID
had more)
85
Santiago Fire, CA Fall 07
86
Santiago Fire, CA Fall 07
87
Santiago Fire, CA Fall 07
88
Santiago Fire, CA Fall 07
89
Poomacha Fire, CA, Fall 07
90
Witch Fire
91
Witch Fire
92
Witch Fire
93
Witch Fire
94
Harris Fire. S CA 2007
95
Harris Fire, S CA, Fall 2007
96
Harris Fire, S CA, Fall 2007
97
Harris Fire, S CA, Fall 2007
98
Harris Fire, S CA, Fall 2007
99
Slide Fire, S CA, Fall 2007
100
Seneca Grade School
Slide Fire, S CA, Fall 2007
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103
Catalina Fire, 2007
104
Catalina Fire, 2007
105
Davis Fire, CA 2007
106
Rat Creek Fire, CA 2007
107
Santiago Fire
108
Sawtooth Fire, CA 2007
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110
After the Fire
111
Hydrophobic soils During an intense fire, the
organic material burns into a hydrocarbon residue
that soaks into the ground. It fills the tiny
pore spaces and sticks them together. As a
result rain cannot percolate into the ground so
it runs off.
112
The ground stabilizing vegetation is removed
113
The reduced vegetation creates unstable slopes
leading to mudslides, debris flows and flash
floods.
Mudslide following the Hayman Fire, CO 5 Jul 2002
114
Gullies eroded by a short-lived rainstorm one
year after the 2000 fires in the southern
Bitterroot Valley, MT
115
  • Mitigation
  • Straw wattles straw packed into tubes
  • Fell dead trees across slope
  • Add drainages to direct flow into valleys
  • Reseeding

Straw wattles placed below the McClain Slide,
Bitterroot Range, MT
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