Experts warn the risk of fast-moving grass fires in Victoria is high this season after months of heavy rain led to massive grass growth, and rising temperatures continue to dry out forests and scrubs.

While recent moist conditions mean the state is less likely to face a major bushfire threat, the Bureau of Meteorology’s Michael Efron said challenging fire conditions would come after Wednesday, with forecast temperatures above 30 degrees combined with an expected strong wind change.

A firefighting helicopter drops water on a fire in Plenty Gorge in 2019. Credit:Justin McManus

“Especially given the flooding, [fire risk] is something that people may not have been paying attention to,” Efron said. “Given these conditions coming up, it is still very important that people keep up to date with that information from fire authorities.”

Three advice warnings for grass fires in Victoria were issued on Monday evening. Two of the small blazes were near Hopetoun in the state’s far north-west while another was just west of Seymour in central Victoria, but all were extinguished within hours.

The Country Fire Authority has warned that the Mallee, Wimmera and North Country regions, much of which were underwater just weeks ago but have now mostly dried out, are subject to high fire danger ratings until later this week.

Fire Risk Consultants managing director Graeme Taylor said the back-to-back years of wet weather fuelled by La Nina had resulted in phenomenal grass growth.

Curing grass near the township of Wedderburn in Victoria’s north.

“The risk with a lot of dry grass across the landscape is that in February or January, when you get those hot, windy days, there’s certainly the chance of fast-moving grass fires,” he said.

Taylor said grass fires could travel up to 25km/h in windy conditions.

Grass has the possibility of igniting when it is 40 per cent dried out, or “cured”, and will definitely ignite when it is 60 per cent cured. The taller and drier the grass, the more intensely it will burn.

Taylor said that in seasons of prolific growth, like the current one we’re in, grass slashing programs needed to be increased to meet the increased risk.

Grassland curing percentage in Victoria as of December 23. Credit:CFA

“There is still lots of unmanaged [grass] on roadsides. This is always an issue, and we can’t drop the ball on roadside fuel management,” he said.

Slashing, which is essentially mowing grassy areas, is carried out by Forest Fire Management Victoria (FFMVic).

Earlier this month, FFMVic announced 1400 hectares of grass would be slashed in the Mallee region, which includes Robinvale, Mildura, Walpeup, Ouyen, Rainbow, Pine Plains and Nyah.

Another 2000 hectares of grass was slashed across central Victoria, including in Avoca, Bendigo, Castlemaine, Cohuna, Maldon, Echuca, Heathcote, Inglewood, Maryborough, Dunolly, Bealiba, Macedon, Tarnagulla, Rushworth and St Arnaud.

FFMVic said that after this year’s floods, rapid regrowth was a possibility and certain areas might need additional treatment over summer.

Weatherzone meteorologist Andrew Schmidt said areas in Victoria’s north, which will reach 40 degrees on Tuesday, were likely to carry a high – but not catastrophic – fire danger rating.

“It’s still just a little bit too wet,” he said. “Looking at soil moisture from all the previous rain we’ve had, it’s still quite moist in the top layer of the soil.”

Some climate drivers that delivered extra rain to Victoria this year include the negative Indian Ocean dipole, which has just ended, and the La Nina weather pattern, which should finish in February.

“Heading into next year, I think we’ll experience a bit more dry weather, as well as hotter weather, than we’ve experienced over the past several months just due to those climate drivers,” Schmidt said.

“The key ingredients that we usually need for an elevated bushfire risk include low dew points – which is to say dry weather, not humid – high temperatures and gusty winds.”

Kevin Tolhurst, an associate professor in fire ecology and management at the University of Melbourne, said dry lightning storms passing over semi-arid areas could set multiple fires, which was more likely to happen in February when conditions were driest.

Taylor agreed bushfires were likely to become more of a risk later in the summer.

“At the moment, the majority of our forests are still drying out. But we still have a lot of weeks of summer to go,” Taylor said.

“Now we’ve got some really hot weather coming and heatwave conditions, so it pays to be aware, wherever you’re travelling in regional Victoria.”

With Lachlan Abbott

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