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Australian Natural Hazards Task Force
Introduction to Natural Hazards -
Some hazards strike quickly, without warning, while other types occur over long periods of time and their occurrence is sometimes predictable. Australia is frequently ravaged by bushfires, more so than any other country in the world. That is why it is crucial for people living in bushfire-prone areas to be prepared.
The Australian Natural Hazards Task Force has created this Information Kit to inform and guide with dealing with fire. Effects of natural hazards can be seen by different geographical perspectives, they include; social, economic and environmental impacts. Australia needs to be ready when deadly bushfires hit and that’s why management strategies are so important and will hopefully reduce the effects of life-threatening events. This kit will also focus on an important case study, ‘
The Ash Wednesday Bushfire
A bushfire is a wildfire that spreads quickly across vegetational areas of harsh & dry environments.
For a bushfire to be catastrophic, there must be certain weather conditions, such as dry conditions, low humidity, strong winds and hot temperatures. The southeast part of Australia is where the majority of the population resides, and it is prone to large wildfires because of its dense undergrowth and dry climate.
Due to its weather, Australia will never be completely protected from raging bush fires.
Causes of Bushfires -
In Australia there are many different conditions that can trigger a bushfire, including dry weather, high temperatures and flammable vegetation.
In remote bushland areas, lightning is most common to ignite a fire.
Poorly attended campfires
Hazard reduction burns
Sparks from machinery
The act of Arson
Fires require three key elements to grow into bushfires and spread. This is referred to as the fire triangle -
fuel, oxygen and heat.
Fuel source - Australia’s natural vegetation of dry forests and grasslands is particularly prone to fire.
Eucalyptus trees shed their leaves & the oil from the tree crown enables fires to spread rapidly in the right weather conditions.
- Sunshine and high temperatures dry out the fuel source making it susceptible to fire.
Also the extremely hot, dry days in the summer season over the south-eastern area of the continent adds to the fire risk.
- The movement of oxygen in the atmosphere is stimulated by strong winds which are caused when steep pressure gradients occur between high and low-pressure systems.
Dry winds that originate from the centre of Australia bring hot and dry conditions with them, which adds to the fire intensity.
Map of Bushfires in Australia
ASH WEDNESDAY BUSHFIRE
The Ash Wedneday Bushfires
were a series of bushfires that occured in south-eastern Australia on the 16 February 1983.
This day is now one of Australia’s most well-known bushfire events.
Fires swept across Victoria and South Australia,
killing 75 people
and causing widespread damage.
Environmental Causes -
Drought & low rainfalls
- Prior to the fire, most of Victoria had experienced a drought lasting 10 months or more.
Rainfall over winter & spring was very low, and summer rainfall for Victoria was up to 75% less than in previous years.
Low rainfalls meant that there was little moisture in the soil and water supplies in many places were almost dry.
- The humidity was very low and fuels such as dry leaves, twigs and other vegetation matter was found across Victoria.
This fuel was very dry, due to the weather conditions and the forest vegetation in valleys and gullies, which is normally moist in summer, was also very scorched.
Hot Temperatures & winds
- Clear skies and temperatures over 40°C were observed on the morning of Ash Wednesday.
A band of cold air was located in the Great Australian Bight off the coast of South Australia.
The front caused the hot air in the centre of Australia to be drawn southwards, creating a hot, dry northerly wind over Victoria.
Effects of the Bushfires -
Due to the large numbers of fires burning on Ash Wednesday, many parts of Victoria suffered damage and eight towns were severely damaged.
There were 75
and 2080 homes were destroyed (2080 in Victoria, 380 in South Australia).
Many businesses, stores, equipment, machinery, stock and other private assets were also lost.
The bulk of the losses in life and property occurred in the hour following the wind change.
Areas where the Ash Wednesday Bushfires hit
Referring to Chart 1
, Bushfires have a greater amount of injuries and death tolls over the time period of 1967 - 1999. Also the chart confirms that the costs ($millions) are greater than the other natural hazards. This is because the continent of Australia is hot, humid and dry which makes it vulnerable for bushfires to occur, leaving communities with nothing but dead land for them to rebuild their lives upon.
The total cost of the property related damage in Victoria was estimated to be just over $200 million.
The fires damaged valuable timber in State forests with losses of around $50 million. Park and forest offices and firefighting equipment were also lost.
16000 firefighters attended the Ash Wednesday bushfires, fighting to save Victoria from mass destruction.
Massive amounts of Flora and Fauna were lost, leaving the areas extremely lifeless.
Referring to chart 2
, the state of Victoria has the highest annual cost ($million) for bushfires than any other state and the Northern territory, the lowest.
Referring to chart 3
, Severe Storms and Bushfires have the same proportion of insured loss to total loss (35%).
The fires burnt the vegetation that protects the soil. After the fires, there was further damage through soil erosion affecting streams and water catchments.
Heavily forested areas, such as Victoria’s eastern Otway Ranges, and the pine forests of southeastern South Australia were incinerated.
Two hundred thousand tons of dry soil were lifted from the ground and the dust cloud was so large and thick that it blocked out the sun in Melbourne.
Fires burning in South Australia on the same day destroyed over 208 square kilometres of land.
Referring to Chart 4, Bushfires occured the 3rd least out of the other natural hazards between the years of 1967-1999.
Damages from the fire
Fires Swept Across Many Kilometres
Management Strategies -
Bushfires are events that require careful monitoring and management by governments, organisations and individuals.
two main fire-fighting techniques
to control bushfires in Australia actually involve lighting fires.
Hazard reduction - Lighting low-intensity fires in the cooler months of the year during favourable climatic conditions to reduce the threat of bushfires.
Back burning - It involves lighting fires in unburnt areas so that the fire front burns into the areas already burnt. They are generally small and are able to decrease a bigger fire.
Another technique is using air cranes when fighting fires.
that can carry 9000 litres of water and are fitted with a flexible hose that allows refilling from water sources as shallow as 45 centimetres in just 40 seconds.
Air crane delivering water to a bushfire
Individual Strategies -
Bushfires threaten properties and lives in Australia each year. It is essential that people in fire-prone areas prepare their property before the fire season arrives.
Here are some easy strategies for around your house;
Remove leaf litter from gutters
Fit shutters to windows
Keep grass short and green
Store flammable chemicals away from the house
Clear plants from near the house
Also, for people who live in bushfire-prone areas, it is best for them to develop a
detailed survival plan
in the event of a bushfire.
Research shows that well-prepared home owners stand a good chance of protecting their homes from destruction in the event of a bushfire.
Bushfire Warning Sign
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