Fairfax Media Network

Weather News

New fire danger rating system set to be trialled this summer to cope with new extremes

Kate Doyle, Ben Deacon and Sarina Locke, Wednesday December 13, 2017 - 06:17 EDT
ABC image
The fire danger rating system is due for an upgrade focussing on the science behind the sign. - ABC

The trusty roadside fire danger signs marking the entrance to every country town are up for a revamp.

They are an Aussie icon, but the science behind the signs, the Forest Fire Danger Index, is now due for a rethink.

The Forest Fire Danger Index (FFDI) was originally created by the grandfather of Australian fire science, Alan McArthur.

He came up with his system by setting experimental fires in the hills around Canberra in the 1950s and 1960s.

It was a different time. Legend has it he used the number of beers needed to mollify firefighters to gauge fire intensity.

Whatever his methods, Mr McArthur's system has been used and has undoubtedly saved many lives.



The FFDI uses a combination of temperature, humidity, windspeed and drought factor to produce an indicator of how easy it will be for a fire to start, and how intense and fast moving the fire is likely to be once it gets going.

What's wrong with the system?

Despite its long tenure, recent major fires have shown the FFDI and its partner, the Grass Fire Danger Index (GFDI) have their flaws.

Rural Fire Service agrees there are problems with the old system.

"There are quite a few examples of fire events in Australia where there has been a very big miss with the McArthur system," he said.

"There have been times when it has served us very well, but there are other times when it has missed."



These are a few of the major problems:
McArthur's original system was only designed for use in forests and grasslands. Australia has a whole range of different types of vegetation such as Mallee heath, woodlands and savanna, and the McArthur system does not forecast those well.
It does not look at all of the conditions that are now known to have an impact upon fire behaviour. Effects such as wind changes and the stability of the atmosphere have big impacts on fire but are not included in the current system.
The McArthur system is very sensitive at the extreme end of the scale. Small changes to the input variables such as temperature, humidity and wind speed can have a big influence on the fire danger index.



The top end sensitivity is a result of a formula created under lower fire danger conditions being extrapolated to extreme conditions.

Dr Heemstra said that sensitivity made it hard to precisely forecast what rating you were going to be in.

"It is possible to jump through several categories with very small changes in temperature, wind speed and humidity," he said.

NSW Rural Fire Service deputy commissioner Rob Rodgers said the difficulties with the top end of the scale were increasingly being put under the spotlight.

"The fires we see nowadays, when we start getting those catastrophic type fires, it was never designed to predict fires of that sort of magnitude," he said.

"It was always intended to predict fires of a much lower level."



Following the Black Saturday fires of 2009, a new category ("catastrophic" or "code red" in Victoria) was added to the roadside signs to describe conditions more extreme than those thought likely by McArthur.

The new system will go a step further by improving the formulas that form the basis of the rating system.

How will the new system help?



Having a more accurate gauge of the potential fire danger will help firefighters and the public better prepare.

It will also allow emergency services to have resources such as aircraft and firefighters at the ready when conditions are at their worst.

"There are never enough firefighters to cover the entire country, but hopefully this will enable us to put those firefighters where they're most needed and where the highest risk is," Mr Rodgers said.

He said the improved system would "undoubtedly" save lives.

"The more informed we are as community and firefighters, the better we're able to react and do that safely."

The prototype is being tested this fire season, and a review is being conducted into how the new system would have rated days when there were big fires in the past that were rated lowly on the old system.

Will the signs change?



Not yet.

Until researchers are sure their new method is an improvement, the current measures will stay in place.

But the signs are one of the things the team is looking into.

Few could deny a system where the second lowest level is "high" and there is a higher category than "extreme" has issues.

Social research considering public perception and responses to warnings is scheduled to begin next year.

But with this season forecast to have above normal fire danger for large areas, and high an improved index would be welcome.


- ABC

© ABC 2017

More breaking news

Sydney Morning Herald
ABC News
National Nine News
News Limited

Display Your Local Weather

Weather News

Myer Hobart store beats flood and fire, but market conditions may be toughest foe

17:03 EST

It has risen again from the ashes and has emerged from a devastating flood — but the challenge for the latest incarnation of Myer's Hobart store is simply to get people to shop there.

Perth rainfall is higher than Melbourne, Hobart, London despite reputation for sunny beaches

14:41 EST

Perth may be best known for its idyllic beaches and sunny skies, but the West Australian capital sees more rain than Melbourne, Hobart and London — cities often associated with gloomy, wet weather.

Dry autumn for Murray-Darling

13:47 EST

With just over a month left until the end of autumn, it's shaping up to be a very dry season for most of the Murray-Darling Basin.