What would you do if you were told that an entire town was predicted to be wiped out within 24 hours? This is the scenario faced by firefighters when bushfire behaviour experts analyse what could happen if a bushfire isn’t put out. Read the story below or watch the video on bushfire behaviour here.
Manager of the Environmental Protection Branch at the Department of Fire and Emergency Services (DFES) Ralph Smith is an experienced bushfire behaviourist. His job is to predict where and when bushfires could impact communities, using state of the art technology.
While it is not a crystal ball, bushfire behaviour modelling is a canny combination of experience, scientific knowledge and technology that helps DFES to understand how fast a bushfire will travel and in what direction.
It enables incident managers to work out the best strategies for firefighters on the ground, so that they can work to save the communities in the fire’s path.
The bushfire season is a busy time of year. Ralph responded to the Northcliffe, Lower Hotham and Bullsbrook bushfires earlier this year, and was deployed in July to assist with wildfires in Canada. He said understanding bushfire behaviour was critically important to fighting the fires.
“These were all very challenging incidents due to their scale, the weather conditions and the number of potentially impacted communities,” Ralph said.
“In cases like these, bushfire behaviour predictions assist decision makers to work out things like the locations to best tackle a fire from, when firefighters need to pull back or change tack, how fast a fire will spread, and whether and when community members need to relocate.
“The clock is always ticking and there is pressure to gather a lot of information from a range of sources, generate predictions and share that information with decision makers.
“Fortunately we have great technology and tools that enable us to form educated predictions – we use models, guides and simulations to generate them.
“We also have access to a lot of information from firefighters on the ground through to satellite feeds, the latest weather details and databases on terrain and vegetation.
“Time is gold in these instances because if it looks like a bushfire may hit a town or populated area then it’s a race to have the area evacuated.”
Following the tragic Black Saturday bushfires in Victoria in February 2009, one of the recommendations from the resulting Royal Commission was to enhance the role of warnings - including the need to provide timely advice about the predicted passage of a fire and the actions that people potentially in its path should take.
Australia’s worst bushfire disaster, it resulted in the highest ever loss of life with 173 people dead and more than 400 injured.
Demonstrating the critical importance of analysing conditions and predicting bushfire behaviour, the Kinglake area (Kilmore East fire) was one of the worst hit when a wind change in the late afternoon turned what was a long and narrow fire band into a wide fire front that moved northeast through populated areas. The area was the worst impacted, with 120 deaths and more than 1,200 homes destroyed.
As technology and knowledge from around the world continue to develop and become more sophisticated, the likelihood of such heartbreaking tragedy being repeated decreases.
“The systems and methods used today are more efficient and effective than ever before,” said Ralph.
“Similar to the way that weather forecasting has become more precise and reliable over time, we anticipate further advancements in predicting bushfire behaviour will continue to give us greater and greater capability to plan for and respond to bushfires.
“Early warnings save lives. The ability to predict a bushfire’s potential behaviour means that the Incident Management Team can work out the best way to fight a fire, including how many firefighters and appliances are needed and whether aerial support is required.
“It also means that DFES can provide up to date advice to the community about their safety during a bushfire with changing conditions.
“That said, there will always be elements that are outside of our control, such as extreme weather conditions or unmanaged private fuel loads.
“While early warnings can save lives some people may still put themselves in danger by choosing to stay and defend or to ‘wait and see’ until it is too late, rather than evacuating in line with warnings.”
DFES has a simulator that enables predictions to be generated within a matter of minutes and these can also be altered based on ‘what if’ scenarios.
“Simulations are good at predicting what path a bushfire will take and how fast it will spread but they give us an indication of what is likely to happen rather than being 100 per cent accurate,” said Ralph.
“Added to this, WA has a unique climate and environment, which varies drastically from one end of the State to the other. This means that bushfire modelling will always need to be adjusted so it applies to the local context.
“There are a lot of different factors involved in making predictions such as the fuel loads (flammable vegetation), wind, temperature and terrain – a change to any one of those factors can have a big impact.
“For example, if it’s a 35 degree day with relative humidity of 25 per cent and winds at 30 kilometres per hour, a fire that starts in a forest with undulating land and 15 tonnes per hectare of forest fuel will spread at a rate of 634 metres an hour.
“Under these conditions it will have such intensity that firefighters can’t directly attack the head fire and if an unprepared house is in its path it will probably be damaged or destroyed by the fire.
“The flame length at the head of the fire would be around six metres long – that’s around three times the height of the firefighters.
“If any one of these determining factors change, then the rate of spread, intensity and flame length will also vary as a result – for better or worse.”
Senior Environmental Protection Officer Jackson Parker said based on the information the team gathers they can generate simulations in near real time to work out the possible direction and speed of a bushfire’s spread.
“It is a race against time to gather and validate all the information we need to make predictions, so we can ensure communities get the information they need in time to be safe,” Jackson said.
“DFES advises people to get out early when there is the threat of bushfire but for some places such as hospitals, retirement homes or schools, a lot more time may be needed to relocate everyone to safety.
“That’s one of the reasons why we do all we can to give people early warning of what may happen.
“We also need to be ready for all possible scenarios when it comes to firefighting objectives, tactics and strategies.
“For example, during the Northcliffe and Boddington bushfire in January this year surrounding towns such as Harvey, Collie and Pemberton could have also been impacted and we were prepared for that based on our predictions.”
Ralph emphasised that understanding the different bushfire Advice, Watch and Act and Emergency warning alerts issued by DFES is vital.
“If you see smoke and flames act immediately – don’t wait for a warning, follow your bushfire survival plan,” he said.
Bushfire behaviour fast facts
- Drier fuels ignite and burn most easily. The amount and type of fuel also influences the intensity of the fire and the length of the flames.
- Fires can move faster in cured natural grasslands than in forests because of their fine structure and exposure to the wind.
- Bushfires travel faster up hill. For every 10 degree increase in angle up slope, a bushfire can potentially double its rate of spread.
- Wind speed is an important factor as a fire spreads as a result of burning embers, radiant heat and direct flame contact. Higher wind speeds tilt flames forward, pushing the fire along at an increased rate as flames can more readily reach unburnt fuel.
- Even if you think you are a safe distance from a bushfire you can still be affected by radiant heat and smoke. If fuel loads are high, such as in mature long unburnt forest or woodland, you could feel pain on bare skin as far as 50 metres away, after only a few seconds.
- Fires also spread by ember attack - fragments of tree bark or other small fuel material that are carried by the wind ahead of the fire and spark spot fires. Embers can get trapped within small openings, such as gaps between roof tiles, and set buildings on fire. Up to half of a jarrah tree’s bark can be burnt off with each fire and these make up the bulk of the embers.