Hazards: Wildfires

Question 1

What are wildfires?

Where do they usually occur?

Answer 1

Uncontrolled fires that destroy forests, grassland and other areas of vegetation.

They usually occur in rural areas, but can reach inhabited areas and destroy agricultrual land and settlements.

Question 2

What are the three types of wildfire?

Answer 2

• Ground fire
• Surface fire
• Crown fire

Question 3

What are ground fires?

Answer 3

Where the ground itself burns, eg peat and tree rots.

Slow, smouldering with no flame and little smoke.

Question 4

What are surface fires?

Answer 4

Fires where leaf litter and low-lying vegetation burn.

Fire can be low or high intensity.

Question 5

What are crown fires?

Answer 5

Fires which move rapidly through the canopy.

Likely to be intense and fast-moving.

Question 6

What does the nature of wildfires depend on?

Answer 6

• Vegetation type
• Strength of wind
• Climate and recent weather
• Topography
• Behaviour of fire

Question 7

What vegetation type favours intense wild fires?

Answer 7

• Thick undergrowth or closely spaced trees allow fire to travel easily.
• Some trees contain lots of oil so burn very easily, eg eucalyptus and pine.

Question 8

What fuel characteristics favour intense wild fires?

Answer 8

• Fine, dry material (long grass, thin twigs) catch fire and burn most easily.
• Large amounts of fuel that form a continuous cover will help the fire burn for longer and spread.

Question 9

What type of climate and recent weather conditions favour intense wild fires?

Answer 9

• Rainfall must be sufficient for vegetation to grow, so there’s plenty of fuel.
• Area usually has distinct dry season when rainfall is low for significant time - causes vegetation to dry up and become more flammable.
• Strong winds provide more oxygen to help the fire burn and spread burning embers.

Question 10

What type of fire behaviour favours intense wild fires?

Answer 10

• Running fires spread more rapidly and are more intense - whereas creeping fires move across the ground surface fairly slowly.
• Fires can throw out burning debris that help the fire spread and become more intense.

Question 11

Canopy.

Answer 11

The top layer of vegetation.

Question 12

What three things do fires need to ignite?

Answer 12

Fuel, oxygen and a heat source.

Question 13

List natural heat sources that can start wildfires:

Answer 13

• Lightning is particularly likely to start a fire if it occurs without much rain.
• Volcanic eruptions can produce hot lava, as or gas, which can start fires.

Question 14

List human heat sources that can start wildfires:

Answer 14

• Accidental - dropping cigarettes, allowing campfires and BBQs to get out of control, or if fireworks or sparks from machinery land in vulnerable areas.
• Fires can also be started on purpose.

Question 15

What does it mean if a species is pyrophytic?

Answer 15

They can withstand fire.

Question 16

Discuss how an area might try to prevent a wildfire:

Answer 16

• Managing vegetation - controlled burning to get rid of litter and to make firebreaks in vegetation in advance.
• Managing built environment - increasing gap between housing and vegetation and intorducing fire retardent materials into construction.
• Modelling - study fires using computer simulations to comprehend and predicts how it might behave.
• Education - ensure people are aware of home safety and how to reduce risk of starting fires.
• Warning systems - lookout posts, air patrol and notice boards.
• Community action - helping people establish their own fire survival techniques.
• Being well insured

Question 17

Name a wildfire event:

Answer 17

Victoria, South-east Australia, February 2009.

Question 18

Describe the risk and vulnerability of Victoria to wildfires:

Answer 18

• Covered by eucalyptus forests which have an oil-rich foliage which burns easily.
• Summer climate is often over 40°C with low humidity and often periodic droughts - produce tinder-dry vegetation.
• Area susceptible to high winds - produce drier conditions and fan flames over large distances.
• Lightning strikes and power cables falling down - produce sparks.
• Rural-urban migration - decline in rural services making ti harder to fight fires when they occurs.

Question 19

Describe the conditions that contributed to the Victoria fires:

Answer 19

• 10 years of drought previously
• Recent temperatures of over 40°C
• Strong winds
• Lack of management
  
  • Large amount of dry oil-rich material to fuel the fire.
• Several fires caused by faulty power lines

Question 20

What were the major impacts of the 2009 Victoria fires?

Answer 20

• 173 fatalities
• More than 2000 houses were destroyed and 1,500 farm buildings
• 7,000 people were displaced
• Huge forest loss - over 1 million acres
• Agricultural losses, eg loss of livestock
• Electricity supply disrupted to over 60,000 residents
• Looting
• Fire costs - $4.4 billion

Question 21

What were the responses to the 2009 Victoria fires?

Answer 21

• Australian Bureau of Meteorology predicted how fires would spread and told residents they could either evacuate or stay in their homes - those who stayed at home put at risk.
• More than 20,000 firefighters and volunteers.
• $400 million donated to rebuild - but making new houses more fire-resistant increased costs, so not everyone could afford to finish.

Question 22

What new responses did Australia adopt in response to the 2009 Victoria fires?

Answer 22

• Announced new fire hazard system - everyday of fire season Bureau will forecast Fire Danger Index.
• New building regulations for bushfire-prone areas - government urged by experts to ban housing in highest risk areas, and were criticised for not doing this.