Your questions answered by CSIRO scientists, drawing on internationally respected bushfire, climate and urban development research.
What caused the fires in Victoria on 7 February 2009?
In south-east Australia, bad fire days are associated with the presence of a 'blocking' high pressure system in the Tasman Sea. This brings hot, dry strong wind from the centre of the continent to the south-east.
The high temperatures, some in excess of 45 degrees, and dry air experienced throughout Victoria on Saturday resulted in very low fuel moisture content. Combined with the extended rainfall deficit for much of the state, this resulted in tinder-dry fuel that was very easily ignited and very difficult to extinguish. In addition, to the high pressure system there was an approaching cold front which helped to strengthen winds ahead of the front, as well as causing a wind change after the front passed. Very strong winds resulted in fires that spread very rapidly with the wind and were practically unstoppable until the weather moderated following the cool change. Victoria's topography and vegetation also played a role.
(A blocking high is a persistent high pressure system that occurs on a large scale, remaining stationary for a period of time, compressing and warming the air below.)
Why couldn't the fires be put out?
There is very little that can be done to suppress fires burning under these conditions. All that fire fighters can do is concentrate on asset protection and wait for the weather to change.
What causes spot fires?
Spot fires are caused by fire brands such as burning bark, twigs and leaves that are blown ahead of the fire front igniting new fires.
How is CSIRO working to understand why these fires happened?
CSIRO researchers will be contributing to the Bushfire CRC’s Bushfire Research Task Force looking at the key issues in the February 2009 bushfires. The task force includes researchers from various state fire agencies and research organisations with expertise in building analysis, human behaviour, community education, bushfire behaviour, fire weather, and fire investigation.
More information is available on the Bushfire CRC’s website.
The purpose of the research is to provide fire and land management agencies with independent analyses of the factors surrounding the Victorian fires. This knowledge will be shared across Australia and internationally and will assist with the Royal Commission and other investigations and inquiries.
CSIRO researchers from the Bushfire Dynamics and Applications Group, the Bushfire Urban Design project and the Remote Sensing team, will be involved with two areas of research:
- Fire Behaviour
The focus is on strategic fire behaviour: how the fires moved across different landscapes and different vegetation and under variable weather conditions. - Building (Infrastructure) and Planning Issues
Researchers are looking at: patterns of loss and patterns of survival of buildings and structures; the notion of defendable space and; planning and building controls and their impact on patterns of building losses.
CSIRO work will feed into the Bushfire Research Task Force findings and as this material will be available for use in the Royal Commission the Bushfire CRC will not be providing detailed comment on the type of work being done, where the work is being done or reporting any findings until they are complete.
What conditions lead to extreme fire weather?
Fire weather is determined by short term climate variables like temperature, humidity, wind, rainfall and evaporation that can change during the course of a day or even an hour.
There are several factors that combine to create extreme fire weather. Wind speed is the primary factor and the temperature and dryness of the air are the other factors. These affect the moisture content of fuels such as twigs, bark, and leaves. The lower the moisture content, the easier it is for the fuel to ignite and burn. Under the extremely dry conditions the led up to the Victorian fires, the fuel was very dry and could burn very quickly.
Once a fire begins, fire weather and topography affect the behaviour of bushfires in terms of the rate of spread, the height of the flames, the intensity of the heat released and so on.
Have fires like this happened before?
Victoria has experienced major bushfires in the past. The 2009 Victorian fires were similar to those experienced on Black Friday in January 1939 and Ash Wednesday in February 1983.
Is a house safe during a bushfire?
When a fire is close, sheltering in a house is much safer than being in a vehicle. In all cases it is important that the house and its occupants are well prepared. The house also needs to be surrounded by a clearance zone free from flammable materials and vegetation. A well-prepared house will provide the occupants protection while the fire front passes. If the house then catches fire, the occupants can relocate outside to the clearance zone behind the fire front.
Is a car safe during a bushfire?
Being in a car during a bushfire is a high risk strategy, however, it is safer than being outside with no protection. In research undertaken with the Bushfire CRC, tests showed that although temperatures may peak at extreme levels in parts of the car, locating the car away from any flammable material, orienting the car toward the fire front, and getting down low in a footwell under a woollen blanket is the best survival strategy.
Did global warming/climate change cause these fires?
It is not possible to attribute an individual weather event to climate change. What we need to look at is trends over time.
The extreme fire weather conditions that occurred in Victoria during January and February were partly due to very high temperatures following a 50 year warming trend, and very dry conditions following 12 years of below-average rainfall.
Most of the warming observed over the past 50 years can be attributed to human-induced increases in greenhouse gas emissions. The dryness over the last 12 years may be due to natural variability but may also be partly due to an increase in greenhouse gases, however it is still too early to tell.
Will we see a more days of extreme fire weather in the future?
Research done by CSIRO shows that by 2020 we expect to see a greater number of extreme fire weather days, longer fire seasons and a greater potential for multiple fire events like those seen in the Victorian fires. We don't yet know how these changes will impact fire behaviour.
How does prescribed burning reduce fuel loads and fire hazards?
CSIRO's Project Vesta studied the characteristics of the behaviour and spread of high-intensity bushfires in dry eucalypt forests under dry summer conditions.
Project Vesta found that reducing fuel loads by prescribed burning reduces the rate of spread, flame height and intensity of a fire, as well as the number and distance of spot fires, by changing the structure of the fuel bed and reducing the total fuel load.
When understorey shrubs regenerate after prescribed burning this does not necessarily mean an increase in the rate of spread of a fire because a significant near-surface fuel layer takes time to build up.
Using prescribed burning to lower bark hazard reduces the density of firebrands (pieces of burning bark that can cause spot fires).
Why were so many houses lost in the Victorian bushfires?
Houses in these regions of Victoria are likely to experience the fire weather that occurred in late January and early February at least once during their life.
Historically, most of Victoria's house loss has occurred under similar hot, dry and windy conditions. These conditions that promote fire spread are the same conditions that dry out combustible elements in, on and around the home, leaving them more vulnerable to ignition and fire spread.
Are these similar to the fires that occur in California, USA?
Some areas of the USA and Australia experience similar conditions that can result in dangerous bushfires: fire weather, bushfire fuels and urban/bush interface.
What research has CSIRO done on fire bunkers?
CSIRO is not currently conducting research into bushfire bunkers or shelters. Previous research by the Department of Defence indicated that underground bunkers may not be safe in bushfires due to the accumulation of toxic gases coming from a bushfire itself.
Bunkers were recommended and used around the time of the 1939 Black Friday bushfires to provide some shelter to mill workers who had no other protection from bushfires when working in the forests. Current research indicates that a well designed and prepared house can provide adequate protection (see question ‘is a house safe in a bushfire’) during a bushfire.
The use, design and efficacy of current era bunkers has not been investigated by CSIRO.
As with any form of bushfire refuge, bushfire bunkers must be assessed in an overall context taking into consideration issues such as:
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expected bushfire behaviour
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design and construction criteria
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preparation and maintenance
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intended and probable use of the bunker
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establishing a safe path to the bunker.
As well as the technical issues, there are a range of other considerations including:
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decision making processes and education around when to retreat to the bunker
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when to close off a bunker
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how long to remain in the bunker
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how to determine when it is safe to exit the bunker.
CSIRO has the capability to engage in the underpinning science for future policy and regulation development covering issues like:
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circumstances where a bunker may or may not be appropriate
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position of the bunker and its proximity to other objects
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designing a bunker
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maintenance and safety considerations.
Areas of bushfire research CSIRO has been involved in include:
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performance of buildings and materials under fire exposure conditions
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integrated town planning and house design for sustainability and bushfire survival
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robustness and role played by residential fence systems and water storage tanks in bushfire prone areas
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product development, verification and enhancement for use in bushfire-prone areas (specialist coatings, glazing protection, timber deck design)
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assessing house vulnerability and bushfire risk at the urban interface
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understanding bushfire behaviour and risk
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analysis of major bushfire events
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fire detection technology
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controlled burning programs
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enhancing firefighter and community safety
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aerial and ground suppression
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managing fire in different vegetation types
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the effects of bushfire burnovers on passenger vehicles
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design and performance of fire vehicle protection systems on bushfire burnovers.
Find out more about CSIRO's bushfire research.
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