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Wildfire Assessment > Wildfire Behaviour > Flashcards

Wildfire Behaviour Flashcards

1
Q

Basic components necessary for a fire to ignite, burn and continue to burn:

A

• Oxygen; • Heat; and, • Fuel

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2
Q

Cutting off oxygen supply is Suitable for ______ _____ only

A

Cutting off oxygen supply is Suitable for small fires only

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3
Q

Cutting off oxygen supply is Difficult to cut off _____ supply to _____ fires out in the open

A

Cutting off oxygen supply is Difficult to cut off oxygen supply to large fires out in the open

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4
Q

Reducing the temperature.

Water directed onto _____ fuel absorbs heat ______ by turning to steam.

A

Water directed onto burning fuel absorbs heat energy by turning to steam.

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5
Q

Water ____ the fuel to a temperature below the fuels ‘_____ ____’ preventing the release of _____.

A

Water cools the fuel to a temperature below the fuels ‘ignition point’ preventing the release of vapours.

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6
Q

Methods of removing fuel from wildfire?

x 4

A
  • Mineral earth lines
  • Control lines
  • Burning out (burning any unburnt fuel between control line and fire edge)
  • Back burning (removing fuel from path of fire).
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7
Q

Burning out is:

A

burning any unburnt fuel between control line and fire edge

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8
Q

Back burning is:

A

removing fuel from path of fire

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9
Q

Three methods of heat transfer

A

Conduction

Radiation

Convection

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10
Q

Conduction:

_____ of heat through a ____ object from a region of _____ temperature to a region of _____ temperature.

A

Transfer of heat through a solid object from a region of higher temperature to a region of lower temperature.

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11
Q

Conduction

Different _______ conduct heat at different _____.

A

Different substances conduct heat at different rates.

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12
Q

Conduction

In wildfires ______ refers to the ______ of heat through the fuel itself.

A

In wildfires conduction refers to the movement of heat through the fuel itself.

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13
Q

Convection

Transfer of _____ through the _____ of air (air is the medium).

A

Transfer of heat through the heating of air (air is the medium).

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14
Q

Convection

Heated air rises ______

A

Heated air rises quickly

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15
Q

Convection

Air movement creates ______ ______ (supplying more oxygen to feed the fire).

A

Air movement creates convection column (supplying more oxygen to feed the fire).

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16
Q

Radiation

_______ heat is the heat you feel from a wildfire.

A

Radiated heat is the heat you feel from a wildfire.

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17
Q

Radiation

Generated by burning ___ and _____.

A

Generated by burning fuel and flames.

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18
Q

Radiation

Travels in ______ lines in all _____ from heat source

A

Travels in straight lines in all directions from heat source

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19
Q

Radiation

Radiated heat does not require a ______ to travel through.

A

Radiated heat does not require a medium to travel through.

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20
Q

FACTORS THAT AFFECT FIRE BEHAVIOUR

A

WEATHER • FUEL • TOPOGRAPHY

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21
Q

5 EFFECTS WEATHER

A

TEMPERATURE

WIND SPEED

WIND DIRECTION

RELATIVE HUMIDITY

ATMOSPHERIC STABILITY

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22
Q

FIRE WEATHER ESTIMATES ARE:

ISSUED AT _____ FOR CURRENT DAY

ISSUED AT _____ FOR FOLLOWING DAY

THE ARE _ WEAHTER DISTRICTS

ISSUED FOR __ REPRESENTATIVE LOCATIONS AROUND VICTORIA

A

FIRE WEATHER ESTIMATES ARE:

ISSUED AT 0630H FOR CURRENT DAY

ISSUED AT 1645H FOR FOLLOWING DAY

THE ARE 9 WEAHTER DISTRICTS

ISSUED FOR 25 REPRESENTATIVE LOCATIONS AROUND VICTORIA

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23
Q

For each of the 25 locations the following WEATHER fields are predicted: X7

A

– Maximum temperature (°C)

– Relative humidity (%)

– Wind direction

– Wind speed and gust (km/h)

– FFDI (using a calculated Drought Factor)

– GFDI (using an observed Curing value)

– Wind change time and wind strength (if appropriate)

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24
Q

For each of the nine districts the following WEATHER fields are predicted for maximum temperature time:

A

– Lightning Activity Level

– Rain

– Height of the mixing depth above sea level (mix, metres)

– Upper level wind direction and strength

– FDI above 35

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25
Q

What is LAL?

A

Lightning Activity Level

0 = nil,

1 = one or two,

2 = a few,

3 = numerous strikes over a district

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26
Q

ATMOSPHERIC STABILITY

Stability can be defined as the _______ of the atmosphere to _______ motion

A

ATMOSPHERIC STABILITY

Stability can be defined as the resistance of the atmosphere to vertical motion

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27
Q

Identifying Stable Atmospheric Conditions

A
  • Stratus clouds
  • Fog layers may be present.
  • Short smoke column
  • Vertical movement of air is limited
  • Winds light and predictable.
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28
Q

Stable Atmosphere Indictors

A
  • Hazy lower layers in the atmosphere
  • Stratus like clouds
  • Steady winds, usually light
  • Perhaps morning fogs
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29
Q

Stable Atmosphere Affect on Fire

A
  • Fire behaviour more predictable
  • Weaker in draft winds  reducing fire intensity
  • Development of a strong convection column above the fire is less likely.
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30
Q

Unstable Atmospheric Conditions

A
  • Cumulus clouds.
  • High smoke columns
  • Winds gusty and unpredictable
  • Potential for thunder and lightning.
  • Dust whirls may occur.
31
Q

Unstable Atmosphere Indicators

A

– Development of Cumulus clouds with vertical growth

– Gusty erratic winds

– Sometimes good visibility

– Dust whirls  willie-willies

32
Q

Convection Column

The superheated ____ column may rise _ to 11 ____ metres above sea level until it cools enough to match the _______ air.

A

Convection Column

The superheated smoke column may rise 8 to 11 thousand metres above sea level until it cools enough to match the surrounding air.

33
Q

Unstable Atmosphere Affect on fire

A
  • Rapidly developing convection columns
  • Intense long distance spotting may occur
  • Turbulent wind causing erratic fire behaviour
  • Thunderstorms may develop, producing strong updrafts and downdrafts and causing erratic fire behaviour at existing fires.
  • Fire behavior can be unpredictable under these conditions
34
Q

TEMPERATUREº

The sun warms the ____ and the ___ surface

  • Brings fuels closer to _____ temperature
  • With a drop in humidity, _____ content reduces
  • Fuels ignite more ______
A

TEMPERATUREº

The sun warms the fuels and the land surface

  • Brings fuels closer to ignition temperature
  • With a drop in humidity, moisture content reduces
  • Fuels ignite more easily
35
Q

RELATIVE HUMIDITY

A measure of the ____ ______ content in the air

A

A measure of the water vapour content in the air

36
Q

RELATIVE HUMIDITY

On humid days, fuels _____ moisture from the air and burn ____

A

On humid days, fuels absorb moisture from the air and burn slower

37
Q

RELATIVE HUMIDITY

On low humidity days the air will ____ moisture from the ___

They will _____ more easily, burn _____ and with more _____

A

On low humidity days the air will draw moisture from the fuels

They will ignite more easily, burn faster and with more intensity

38
Q
A
39
Q

3 important points of wind direction

A
  • Direction the wind is coming from
  • Local winds
  • Effects on fire when wind changes
40
Q

Effects of wind

A
  • Rate of spread
  • Direction and predictability
  • Spotting
  • Preheating of fuels
41
Q

Effects of stronger winds

A

– The higher the rate of spread

– Removes smoke, ash and fuel moisture

– Lift burning material  causes spot fires

42
Q
A

Sea Breeze

43
Q
A

Anabaic Winds

44
Q

During the day incoming solar radiation warms the earth’s surface

  • The warmer and less dense air rises and creates a void that tends to draw in air from lower down the slope
  • ________ _____ are strongest when the sky is clear, in steep terrain where vegetation is sparse, in areas that receive greater amounts of sunlight and when synoptic winds are light
  • _____ ______ are typically stronger than Katabatic flows
A

Anabatic Winds

45
Q

At night the land cools more quickly than the water

  • Air above the land cools, and the dense air sinks creating a surface high pressure region
  • Air flows from the land to the low pressure region over the water
A

Land Breeze

46
Q
A

Land Breeze

47
Q
A

Katabatic Wind

48
Q
  • The earth cools at night
  • This cooler and denser slab of air moves down-slope under the influence of gravity forming a _____ _____ or drainage flow
  • _____ ______ are strongest when the sky is clear, in steep terrain where vegetation is sparse, and when synoptic winds are light
A

Katabatic Wind

49
Q

Fuel Considerations

A
  • Type
  • Size
  • Quantity
  • Arrangement
  • Moisture Content
50
Q

Types of fuels

A
  • Grasses
  • Litter lying on the ground
  • Small herbs, shrubs & scrub
  • Decomposing humus and duff
  • Shrubs ( Ladder fuels)
  • Trees
  • Material remaining after logging
51
Q

Fine fuel less than ____mm

Heavy Fuels above ____mm

A

6mm

52
Q

Fine fuels include

A
  • Leaves, twigs, grasses, barks etc
  • Burn readily and cause spotting
53
Q

Heavy Fuels include

A
  • Surface fuels such as logs and branches
  • Ignite less readily and burn slower
54
Q

Definition of ‘avaiable fuel”

A

all fuel that is available to burn at this point in time

55
Q

Defintion of total fuel

A

– all the fuel that will burn under the worst possible conditions

56
Q

Fuel Arrangement

The way ____ are arranged in relation to one ____ and how it effects the way they _____.

A

Fuel Arrangement

The way fuels are arranged in relation to one another and how it effects the way they burn.

57
Q

3 categories of grass fuels

A

Natural pasture

Grazed Pasture

Eaten out Pasture

58
Q

Ladder fuels

Fine fuel from the ground surface to the crown of a tree encourages _____ of ______ fires

A

Ladder fuels

Fine fuel from the ground surface to the crown of a tree encourages development of crown fires

59
Q

4 Fuel hazards that make up overall fuel hazard

A

Bark

Elevated

Near-surface Fuel

Surface Fine Fuel

60
Q

2 Topographical considerations

A

Slope

Aspect

61
Q

Topography

  • _____ the ___ of the land
  • Effects _____ wind pattern
  • Effects the ____ and _______ of a fire
A

Topography

  • Describes the lay of the land
  • Effects local wind pattern
  • Effects the speed and direction of a fire
62
Q

______ is the direction that a _______ or slope faces

A

Aspect is the direction that a feature or slope faces

63
Q

How does slope effect rate of spread?

A

Every 10 degrees up the rate of spread will double

Every 10 degress down the rate of spread will half

64
Q

Mountain and valley winds are caused by three processes

A

– Wind flow around and between obstacles

– Wind flow over obstacles

– Surface heating and cooling

65
Q
A
66
Q

TYPES OF WILDFIRE

A

• SURFACE FIRE • CROWN FIRE • GROUND FIRE

67
Q

Fuel moisture content depends on

A

Weather conditions

Vegitation Type

Fuel is dead or alive

68
Q

Fuel moisture content effect on fuel

A
  • Ease of ignition
  • Probability of spotting
  • Rate of combustion
  • Rate of fire spread
  • Amount of heat radiated from the flames
69
Q

What is Fire Danger?

It is a measure of the ________ in controlling or ________ a wildfire

It is ________ using a number to which a descriptive FDR ( fire danger rating ) is attached, where higher values represent a higher level of ______

A

What is Fire Danger?

It is a measure of the difficulty in controlling or suppressing a wildfire

It is quantified using a number to which a descriptive FDR ( fire danger rating ) is attached, where higher values represent a higher level of danger

70
Q

FDI is calculated with the following variables:

A

– Fuel state ( due to rainfall etc. )

– Temperature

– Humidity

– Wind speed

71
Q

McArthur FFDI determines the difficulty of fire suppression due to:

A

– Drought Factor

– Temperature

– Relative humidity

– Average wind speed (at 10m height)

72
Q

McArthur GFDI determines the difficulty of fire suppression due to the following:

A

– Curing ( the percentage of dead grass )

– Temperature

– Relative humidity

– Average wind speed (at 10m height)

73
Q

The __________ of knowing the capabilities of the ______and ________ to fight fires is evident…but, if you do not know what the fire is going to do, it is just not enough.

A

The importance of knowing the capabilities of the crew and equipment to fight fires is evident…but, if you do not know what the fire is going to do, it is just not enough.

Wildfire Assessment (3 decks)

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