FOREST FIRE CONTROL

1
FOREST FIRE CONTROL USE (Chapter 18)

• Forest fire an issue because
• Ecological/evolutionary significance
• Economic significance
• Threat to human life property
• Management tool
• Controversies surround control use decisions

2
FOREST FIRE CONTROL USE (Chapter 18)

• Topics
• Fire as a natural phenomenon
• Fire as a landscape architect
• Human impacts
• Forest fire prevention
• Forest fire behavior
• Forest fire control management

3
FOREST FIRE A NATURAL PHENOMENON

• Lightning fires common
• 500,000 forest lightning strikes per day
• Charcoal in lake sediments 1000s years old
• Centuries-old redwood fire scars

4
FOREST FIRE A NATURAL PHENOMENON

• Lightning fires vary in frequency
• Rare in tropical rain forests
• Uncommon in moist temperate regions
• E.g., in eastern North America, lightning causes
  lt2 of forest fires
• Frequent in western conifer forests
• E.g., in Rockies, lightning causes gt60
• Variation is due to climate, topography,
  vegetation characteristics

5
FOREST FIRE A NATURAL PHENOMENON

• Few lightning fires become catastrophes
• High humidity rain often accompany lightning
• 97 burn 10 acres or less
• Occasionally, lightning ? conflagration
• Dry lightning can occur
• E.g., Great Idaho Fire (1910) burned nearly 3
  million acres (4700 square miles)

6
FOREST FIRE LANDSCAPE ARCHITECT

• Fire frequency intensity affect
• Forest stand characteristics
• Average age of stands in an area
• Even-aged vs. uneven-aged
• Early-successional vs. climax stage
• Growth
• Wildlife populations
• Insect disease conditions

7
FOREST FIRE LANDSCAPE ARCHITECT

• Crown Fires
• Lead to even-aged forests where frequent
• E.g., lodgepole pine in West
• E.g., early-successional forests (aspen, jack
  pine, red pine) common in Minnesota
• Rarer in northern hardwoods
• 1000 years between fires
• Thus, uneven-aged climax forests dominated
  pre-Colombian landscape

8
FOREST FIRE LANDSCAPE ARCHITECT

• Plant species adapt to frequent fires
• Rapid colonization early domination, e.g.
• Light seeds for long-distance transport
• Root sprouting (aspen)
• Serotinous cones (lodgepole pine)
• Seedling tolerance of dry surface conditions
  temperature extremes
• Rapid early growth (aspen)
• Thick bark (resistant to fire injury, e.g.,
  ponderosa pine)

9
FOREST FIRE BENEFITS

• Forest rejuvenation and delay of climax species
  invasion
• Wildlife habitat improvement
• Light surface fires reduce hazardous fuel
  accumulation (which lowers risk of large
  catastrophic fires)
• Release to soil of organic matter nutrients

10
FOREST FIRE HUMAN IMPACTS

• Ancient peoples used fire to
• Improve hunting
• Ease travel
• Clear land
• Reduce pest populations (insects snakes)
• E.g., shifting slash burn tropical agriculture
• E.g., North American native peoples

11
FOREST FIRE HUMAN IMPACTS

• 1800s little appreciation for beneficial
  effects, because fire
• Destroyed timber resources
• Threatened human life property
• Thus
• Fire suppression became predominant policy

12
FOREST FIRE HUMAN IMPACTS

• By mid 1930s
• Goal all wildfires suppressed ASAP
• Little planned (prescribed) burning, except
• Fuel reduction
• Seedbed preparation
• 1940s - 1960s
• Realization labor equipment insufficient to
  suppress all wildfires (especially in West)
• Priorities needed for fire suppression efforts

13
FOREST FIRE HUMAN IMPACTS

• Need to prioritize ? Fire Management
• Fire recognized as natural environmental factor
• Undesirable fires suppressed
• Beneficial effects of fire utilized
• Decisions based on management objectives
• Decisions not aimed at universal suppression

14
FOREST FIREHUMAN IMPACTS

• Humans are primary cause of fire in most areas,
  e.g., in United States
• Incendiarism (26 overall 40 in south)
• Smoking (19)
• Debris burning (18)
• Lightning (9)
• Machine use (8)
• Campfires (6)

15
FOREST FIRE PREVENTION

• Large proportion of human-caused fires ?
• Prevention Strategy Education, e.g.
• Smokey the Bear
• Programs targeting incendiarism

16
FOREST FIRE PREVENTION

• Prevention Strategy Hazard Reduction
• Goal is to reduce
• Fire frequency
• Fire intensity
• Hazard reduction activities
• Fuel reduction
• Prescribed burns
• Snag removal after fire or harvest
• Construction of barriers to fire spread

17
FOREST FIRE BEHAVIOR

• Fire behavior is
• Rate of spread
• Direction of spread
• Fire intensity
• Fire behavior knowledge essential for
• Decision whether or not to suppress
• Choice/implementation of suppression strategy
• Design/implementation of prescribed burns

18
FOREST FIRE BEHAVIOR

• Behavior determined by three fire prerequisites
• 1. Flammable fuels
• 2. Heat
• 3. Oxygen
• These prerequisites are affected by
• Fuel conditions
• Weather conditions
• Topography

19
FOREST FIRE BEHAVIOR

• Behavior Topics
• Types of forest fire
• Surface fires
• Ground fires
• Crown Fires
• Weather
• Topography
• Prediction of fire behavior

20
FOREST FIRE BEHAVIOR

• Surface Fires
• Burn surface fuels undecomposed litter, fallen
  logs, grasses, herbs, small woody plants
• Rate of spread depends on amount, arrangement
  moisture content of fine fuels
• Intensity depends on large fuels (logs)
• Most intense in logging slash
• More total fuel ? more difficult to control

21
FOREST FIRE BEHAVIOR

• Ground Fires
• Burn ground fuels (below surface) partly
  decomposed organic matter, roots, peat
• Oxygen often limited
• Low intensity slow spread
• BUT persistent difficult to extinguish

22
FOREST FIRE BEHAVIOR

• Crown Fires
• Burn aerial fuels tree crowns subcanopy
  flammable materials
• Common in conifers, rare in hardwoods
• Usually begin as surface fires
• Can blow up into conflagrations
• Powerful convection column
• Convection column creates its own draft
• Embers spot far ahead of main fire
• May be uncontrollable

23
SURFACE FIRE BECOMING CROWN FIRE LODGEPOLE
PINE EASTERN WASHINGTON
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FOREST FIRE BEHAVIOR

• Fire Weather Includes
• Atmospheric moisture (relative humidity)
• Atmospheric stability (resistance to vertical
  motion)
• Wind

25
FOREST FIRE BEHAVIOR

• Fire Weather
• Atmospheric moisture (relative humidity)
• Atmospheric humidity controls fuel moisture
• Rate of fuel moisture response depends on fuel
  size
• Fire energy must evaporate fuel moisture before
  burning fuel itself (wet fuels dont burn easily
  !)

26
FOREST FIRE BEHAVIOR

• Fire Weather
• Atmospheric stability (resistance to vertical
  motion)
• Stable winds steady horizontal
• Unstable gusty, turbulent winds, vertical
  motion, strong fire convection column possible
  (which, in turn, can dramatically modify local
  weather)

27
FOREST FIRE BEHAVIOR

• Fire Weather
• Wind
• Rate of fire spread is proportional to square of
  wind speed
• Wind speed direction affect shape of fire
• Shifts in wind direction can turn a long flank
  into a large headfire

28
FOREST FIRE BEHAVIOR

• Topography
• Fires burn quickly upslope
• Fires burn slowly downslope
• South southwest slopes warmest driest
• Slopes modify channel airflow patterns
• Mountainous terrain ? wind turbulence

29
FOREST FIRE BEHAVIOR PREDICTION

• Physics principles ? mathematical models
• Models fire weather data ? predictions
• E.g., National Fire-Danger Rating System predicts
• Number of fires in an area
• Ignition probability in an area
• Rate of spread
• Burn intensity
• Fire perimeter location in future (for ongoing
  fires)

30
FOREST FIRE CONTROL

• Control is
• Cooperative
• U. S. Forest Service
• Bureau of Land Management
• National Park Service
• State government agencies
• Private owners industry (sometimes)
• Highly organized (think of military campaigns)

31
FOREST FIRE CONTROL REQUIRES DETECTION !

• Detection methods
• Lookout towers (gt5000 in 1950s few now)
• Aerial detection (systematic daily flights, e.g.,
  Ontario)
• Casual reports from public
• Combination of the above

32
FOREST FIRE CONTROL SUPPRESSION

• Suppression requires removal of one of
• Fuel
• Oxygen
• Heat
• Fire line removes fuel
• Dirt, water, retardants reduce heat O2

33
FOREST FIRE CONTROL SUPPRESSION

• Direct attack
• Used on low-intensity fires
• Fire line constructed at/near fire edge
• Flames physically attacked (usually with dirt)
• Indirect attack
• Used if direct attack unsafe
• Fire line constructed at distance
• Backfires remove fuel between constructed fire
  line and headfire

34
FOREST FIRE CONTROL SUPPRESSION

• Aerial Attack
• Application from aircraft of
• Water
• Retardants
• Flame-inhibiting chemicals
• Surfactants (wetting agents)
• Slurries (clay) minimize evaporation during drop
• Supplement to ground attack
• Delaying tactic
• Cools hotspots
• Not usually intended to extinguish fire

35
FOREST FIRE CONTROL SUPPRESSION

• Conflagration Fires
• Produce convection column
• Create own weather (strong updraft, strong winds
  toward fire)
• Self-sustaining
• Spotting of embers long distances (gt 1 mile)
• Can jump fire lines, lakes, rivers, roads
• Can endanger and surround crews
• Control infeasible until weather favorable

36
FOREST FIRE CONTROL SUPPRESSION STAGES

• 1. Initial Attack
• 2. Containment
• Fire line around perimeter
• Fire no longer spreading
• 3. Mop-up
• Follows containment
• Extinguish all fires inside of fire line
• Excavate burning stumps roots
• May require winter to complete

37
FOREST FIRE PRESCRIBED BURNS

• Use of fire to accomplish specific goals, e.g.
• Reduction of logging debris (fuel) to reduce
  wildfire hazard
• Seedbed preparation
• Surface fuel reduction in standing forests
• Understory vegetation control
• Wildlife habitat improvement
• Range improvement

38
FOREST FIRE PRESCRIBED BURNS

• Advantages over mechanical methods
• Economical
• Energy efficient
• Disadvantages
• Risks to life and property
• Air pollution
• Few days per year with suitable burning
  conditions (in some regions)

39
FOREST FIRE PRESCRIBED BURNS

• Planners must consider fire behavior
• Topography
• Weather conditions
• Fuel conditions
• Fire Prescription includes
• Desired effects
• Fire intensity and spread rate needed
• Suitable conditions for ignition

40
FOREST FIRE PRESCRIBED BURNS

• Fire line constructed prior to ignition
• Test burn conducted prior to main burn
• Fires ignited by drip torches or from air
• Backfires are the least risky