Australia After bushfires burned more than 1 million hectares through the Australian Alps in 2003, bushfire analyst Greg McCarthy set about studying the effectiveness of earlier prescribed burns.
Prescribed burns, or fuel reduction burns as they are also known, are designed to reduce the amount of fuel in an area before any bushfire.
“We can’t have any effect on the weather or the topography but we can have an effect on the fuel from our fuel reduction burning,” Mr McCarthy said.
“Of those three factors, fuel is the one we try to manage in the expectation that on the bad fire day, the reduced fuel will make some difference to the way the fire burns.”
Mr McCarthy works with the Victorian Department of Environment, Land, Water and Planning and presented his findings at the Australasian Fire and Emergency Services Conference in Brisbane this week.
Factors reduce effectiveness of controlled burns
His work shows there are certain factors that can reduce the effectiveness of a prescribed burn.
“When the energy in the weather builds up on those really bad fire days, the difference in fuel that is, the differences we might have made from doing fuel reduction burning doesn’t make as much difference, once the weather builds to a certain level,” he said.
Mr McCarthy found the size of a fire at the point of its greatest intensity could also influence the effectiveness of a prescribed fire.
He said when a head fire was between five and 10 kilometres wide, a fire became “a very unmanageable beast”.
“It’s rolling through the landscape and it’s integrating the fuel and topography into it,” Mr McCarthy said.
Another factor is the elapsed time between a fuel reduction burn and a bushfire.
Mr McCarthy’s study found a fuel reduction burn best helped reduce fire severity, or suppress a fire, when the bushfire was burning late of an evening or overnight and when it had occurred within the previous three years. Controlled burns controversial
Planned burns have been controversial in Victoria with questions raised about their management and effectiveness.
The Royal Commission into the Black Saturday bushfires recommended Victoria set a target of burning five per cent of the state’s public land each year.
But a report from the Inspector General for Emergency Management last year recommended a move to a risk-based strategy, with concerns over the effectiveness of a target-based approach.
Victoria’s environment department was also criticised when a planned burn escaped containment lines in Lancefield, in central Victoria, late last year, and destroyed four homes.