Australia's 60-year-old fire danger ratings get overhaul

The Bureau of Meteorology has successfully trialled a new Australian Fire Danger Rating System, which more accurately predicts bushfire threat and is to be fully rolled out before the next fire season.

Its introduction will see road-side signs across Australia replaced to show only four levels of risk: moderate – plan and prepare, high – be ready to act, extreme – take action now to protect your life and property, and catastrophic – for your survival leave bushfire risk areas.

The Australasian Fire and Emergency Services Authorities Council (AFAC) says Australia has diverse ecosystems, and these are not well represented by the existing fire danger system as it does not properly account for current fuel states or “make use of the last 60 years of fire behaviour science,” and its models have high sensitivity to changes in input values.

“The existing Fire Danger Ratings are based on science that is more than 60 years old, are not updatable and only designed for a limited number of vegetation types representing a third of the Australian continent,” AFAC said.

“It is known to perform poorly particularly at the higher end of the ratings scale where most impact occurs.

“There is a high degree of confidence that the new ratings will be easier to comprehend and encourage greater community engagement and comprehension, and therefore improve community safety.”

Since the 1960s, Australia has been using the McArthur meter developed with CSIRO which is based on two fire behaviour models – forest and grass – for all of Australia.

The new system will use eight updatable fire behaviour models: forest, grassland, grassy woodland, spinifex, shrubland, mallee heath, buttongrass and pine. This improves fire danger prediction accuracy and leads to better decision-making.

“Because vegetation types have different structural characteristics, fire moves in a different way through each – therefore each requires its own modelling,” AFAC said. “The new system is able to provide a diversity of fire behaviour, spread and danger across the country.”

A prototype was developed by the NSW Rural Fire Service, which is now working with a software developer and the Bureau of Meteorology to build the underlying infrastructure, including indices for ignition likelihood, fire impact and suppression difficulty.

“In recent years, we’ve mapped the vegetation across the entire country. So instead of the current system using just bush and grass to determine the fire danger, the new system will use eight different types of vegetation – making it more accurate,” the NSW Rural Fire Service said.

Community feedback also indicates a system which is easier to understand will increase the likelihood of people acting on fire danger rating information.

A more detailed Fire Behaviour Index is also being developed which will provide a scale of potential fire behaviour, including intensity, flame height, rate of spread and spotting potential. That index will guide when it is safe to prescribed burn, which bushfire suppression strategies are safe or effective, and Total Fire Ban declarations.

Under the new system, the Bureau of Meteorology will provide Fire Danger Rating Tables showing four days of forecast Fire Danger Ratings, as well as Fire Weather Warnings in the case of enhanced fire danger risk.