Wildfires Flashcards
What is fire?
A chemical reaction as a result of three key elements combining. Oxygen, Heat, Fuel. Known as the fire triangle.
What are 3 types of heat transfer?
Radiation, Convection, Conduction
What are the three types of bush fires?
Ground Fire
Surface Fire
Crown Fire
Define Ground Fire
Ground fire burns the organic material in the soil layer and also the surface litter and small vegetation.
Define Surface Fire
Surface Fire travels just above the ground surface, in vegetation such as grass, low shrubs and forest litter.
Define Crown Fire
Crown fire burns in the crowns of trees ahead of and above an intense fire in the undergrowth.
What is a Spot Fire?
A Spot Fire is a new fire which has been ignited ahead of a main fire by embers or a burning object often called a fire brand.
What does a grassland fire consist of?
Light to moderate fuel loads
Mostly fine surface fuels
Maximum wind penetration
What does a forest fire consist of?
Heavy fuel loads
Mixture of fine and heavy fuels
Bark fuels
Elevated fuels
Restricted wind penetration
What does a wildfire in grasslands have?
Moderate intensities
High rates of speed
Short residual burning time
And limited short distance spotting
What does wildfires in forests have?
Very high intensities
Relatively low rates of spread
Long residual burning time
Potential for long distance spotting
What do Crown Fires consist of?
Burns in crowns of trees ahead of and above surface fires
Fast travelling and destructive
An intense surface fire can lead to a crown fire
Short or long distance spotting often present.
If fire is 100m or wider it has reached it ROS
If a fire is a fire 100m or wider it is said to have reached its?
R.O.S
What is required for spotting to occur?
Suitable fuel type
Sufficient energy release to carry particles
A receptive fuel bed
Spotting favours an unstable atmosphere and upper and lower winds mixing
What can spotting lead too?
Many fires ahead of the main fire
Potential trap for firefighters
Increase in difficulty of suppression
A rapid forward rate of spread
What are the parts of a wildfire?
The heel, rear or back
Point of origin
Flank, left or right going with wind direction
Finger
Head of Fire
Spot fires
What three things is bush fire behaviour dependant on?
Fuel
Weather
Topography
What are the four elements of wildfire fuel that affect fire behaviour?
Type - grass, trees, shrubs etc
Size and quantity - fine fuels <6mm, heavy fuels >6mm
Arrangement - dense forest or fine loosely stacked
Moisture content - how damp fuel is, dry fuel will burn better.
What are the heights of fuel?
Surface Level
Near Surface Level
Elevated
Canopy
What effect does moisture content have?
Effects ignition
How quickly it will burn
Rate of spread
Intensity
Likelihood of spot fires occurring
What are the four key elements of weather?
Temperature
Relative Humidity
Wind
Atmospheric stability
What does wind do and what are its factors?
Determines the intensity and rate of spread.
Factors include:
Potential spot fires
Wind direction
Locality of wind
Change in wind direction
What is topography and its components that affect fire behaviour?
Describes lay of the land.
Factors include:
Slope
Aspect
Terrain/wind direction
Elevation
Why is fire travelling up a slope bad and what is the rule of thumb?
Fire travelling up a slope means that is there a shorter distance for radiant heat to travel.
For every 10 degrees of slope, the rate of spread doubles.
What is aspect and its differences?
Aspect is the direction that a feature or slope faces.
North/Westerly: more solar radiation, dry and flammable vegetation
Southerly/Easterly: less solar radiation, lush and less flammable vegetation.
What is the difference between a stable vs unstable atmosphere?
Stable: predictable winds, layer clouds, hazy lower atmosphere and morning mists and fog.
Unstable: gusty and erratic winds, clouds with strong vertical growth, clear lower atmosphere, dust devils.
What SOG outlines ACTFR Wildfire response?
SOG 7