When the strong northerly winds hit the tinder dry bush each summer, Australians anxiously wait for the outbreaks of fierce unpredictable bushfires, that ravage the land leaving death and destruction in their wake.

With the right geographical and climate information, experienced firefighters can usually predict the path of the main body of the fire. But not so predictable are the spotfires, caused by flying sparks, that can fly more than 25 kilometres ahead of the main blaze.

There are more than 600 different types of eucalypts and each one acts differently in a bushfire.

So scientists from Australia's science agency, CSIRO, set out to find how the different woods burn, and how far they can fly.

Each eucalypt type is weighed and the burning samples are placed in a specially designed, 12-metre tall, vertical wind tunnel. By adjusting the speed of the wind in the tunnel, the scientists can work out when it is likely to fall.

"A piece of bark starts off by burning quite quickly, but as it burns it gets smaller and smaller. It falls more slowly until it's burnt out."

By discovering the behaviour of the different types of rogue firebrands, it's easier to predict the possible sites of spotfires.

"We've found that stringy bark is one of the most dangerous types of bark because it ignites easily, it burns slowly and it falls very slowly. This means that it will travel longer distances ahead of the fire and start spotfires."

But the most dangerous bark they've found is the manna gum that can send sparks five times as far as the stringy bark.

By knowing the wind direction, wind speed and tree type in the region, firefighters will be better able to predict where spotfires and possibly new fire fronts might flare up. This could save many hectares of valuable land, fauna, livestock and even human lives.

CSIRO Enquiries
Email: Enquiries@csiro.au
Phone: 1300 363 400
Locked Bag 10
Clayton South
VIC 3169