Hazards 7


Wildfires are uncontrolled fires that destroy forests, grasslands and other areas of vegetation. They usually occur in rural areas, but if they reach inhabited areas, they will also destroy agricultural land and settlements.

There are three types of wildfire:

1. Ground fire is where the ground itself burns. It is a slow, smouldering fire wih no flame and little smoke.

2. Surface fire is where leaf litter and low-lying vegetation burn. Fire can be low or high intensity.

3. Crown fire is where fire moves rapidly through the canopy. Fires are likely to be intense and fast-moving.

There are certain conditions that favour intense wild fires:

Vegetation type:

  • Thick undergrowth or closely spaced trees allow fire to travel easily.
  • Some trees, such a eucalyptus and pine, contain a lot of oil and so burn very easily.
  • Eucalyptus trees shed strips of their bark which helps the fire to spread quickly.

Fuel characteristics:

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

Climate and recent weather:

  • Rainfall must be sufficient for vegetation to grow, so there's plenty of fuel.
  • The area usually has a distinct dry season when rainfall is low for a significant time. Warm, dry weather causes water in the vegetation to dry up, so it's more flammable.
  • Strong winds provide more oxygen to help the fire burn and spread burning embers.

Fire behaviour:

  • Fire burns in different ways.
  • Fires can throw out burning debris (firebrands) that help the fire spread and become more intense.

Fires need fuel, oxygen and a heat source to…


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