Australia has had a considerable number of hazardous bushfires, the Ash Wednesday Bushfires of 1983 is one of Australias most devastating.

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Ash Wednesday Bushfires

yr 10

jessica dimovski


ASH WEDNESDAY BUSHFIRES

The many natural hazards that have occurred over the years have varied from cyclones to droughts, however bushfires are the main hazard Australia is prone to. A bushfire is an out-of-control fire that burns bush, forest and woodland areas. Australia has had a considerable number of hazardous bushfires, the Ash Wednesday Bushfires of 1983 is one of Australia’s most devastating.

THE LOCATION:

Over one hundred fires broke out between February 16th-18th 1983, eight of which were major fires. These fires swept across regions of VictoJ.Dimovskiria and South Australia causing widespread damage. Figure 1 below is a map of Victoria, the red representing where the fires were formed. The eight major fires were started in the following areas of Victoria:

  • Cudgee, Ballangeich and Framilingham
  • East Trentham and Mt Macedon
  • Otways
  • Belgrave heights and Upper Beaconsfield
  • Monivale
  • Branxholme
  • Warburton and
  • Cockatoo


GEOGRAPHICAL PROCESSES:

CAUSES

An ignition flame point is needed for a bushfire to start. This ignition is caused naturally by lightning strikes or by a deliberate/accidental flame for example arson, camping fires or carless behavior. Most of the Ash Wednesday fires were caused by an accidental ignition, for example in Cudgee, Mt Macedon, Monivale and Branxholme. The suspected cause for these fires was the clashing of electrical powerlines with tree branches.

Bushfires can be influenced by several factors. It is primarily the weather conditions and geographical processes that dictate the behaviour and spread of a fire.

Drought plays an essential part in the environment desiccating determining the spread of a bushfire. Due to lack of rainfall, vegetation such as dry grasses, parched native shrubs and other combustible materials build up and become fuel for the fire to burn. Before the Ash Wednesday fires Victoria suffered 10 months severe drought.

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The relative humidity also results in the right climatic conditions for a bushfire to occur. If the amount of water vapour in the atmosphere is than 20%, it can cause forest fuels to dry out and become highly flammable. The relative humidity of Victoria was exceedingly low in the months leading to the bushfires. At one stage Melbourne’s relative humidity reached as low as 6% compared to the usual 43%. This factor greatly
contributes to increasing the speed of the fire.

High temperatures are necessary for a fire to occur. Hot air from high temperatures is responsible for helping to lower ...

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