Grass fires still a risk despite floods

It's hard to imagine, but flood-ravaged parts of Australia could still face dangerous grassfires this summer and all it will take is a few hot, dry days.

After the wettest year on record in some parts, and ongoing flooding in Australia's northwest and south, the prospect of fires any time soon seems incongruous.

But CSIRO fire expert Dr Andrew Sullivan says the risk of grassfires - fast-moving blazes that have been among Australia's most deadly - remains very real.

And just a few days of hot, dry weather could create the right conditions.

"You can get extensive fires burning through grasslands the same year as extensive rain and growth because it grows really quick and it dries out really quick," he says.

He says annual grasses that grow, flower, set seed and then die every year have now completed their life cycle and are turning brown.

Regardless of factors like how much moisture is in the soil, and how much rain falls this summer, that dead material is still lying there.

The critical factor is whether or not places that have had heavy growth get the hot dry conditions that will dehydrate dead vegetation and make it ripe for combustion.

"You don't need a great period of time. If you get three or four days of hot, dry, windy weather at the end of January or February there's a potential that stuff will burn really well, regardless of what the general climate is doing."

The same isn't typically true for forests, which take much longer to dry out.

"It's not until you've had at least two to three continuous years of rainfall deficit that you've got the potential for catastrophic fires burning through forest lands."

Dr Sullivan is the principal research scientist at the National Bushfire Research Laboratory, which delves into the factors that influence bushfire behaviour.

He doesn't believe most Australians fully grasp how dangerous grassfires can be, with news coverage often dominated by dramatic images of flames racing through tall forests.

But in the fire stakes, a grass one will outpace a forest one every time, and he says it pays to remember what unfolded on South Australia's Lower Eyre Peninsula in 2005.

The blaze killed nine people, including eight who perished as they tried to escape the danger in their cars. Four of them were children.

About 50,000 livestock also died and 93 homes were destroyed.

Dr Sullivan says the fastest reliably recorded grassfire spread at 27km/h, and there were reports the Eyre Peninsula blaze exceeded that, at 30km/h, about three times the maximum speed of most forest fires.

"The issue with grass fires is that they can start somewhere and in a very short amount of time be burning somewhere else totally different, with people totally unaware there's a fire heading their way. And they get caught out."