New Project Vesta figures show that the forest fire spread prediction systems developed by bushfire researcher Alan McArthur in the mid 1960's can under-predict the potential rate of spread by as much as 3 times.
CSIRO has warned rural fire brigades around Australia of the new findings.
Almost a hundred experimental fires were lit during Project Vesta, a six-year, multi-million dollar study investigating the behaviour of summer fires in dry eucalypt forest.
The research project involved CSIRO and the Western Australian Department of Conservation and Land Management (CALM), supported by Australian fire and land management agencies, local government and corporate sponsors.
"These warnings arise from preliminary analysis of the field data collected over the past two summers. The warnings are posted as a guide only and may be subject to change as the evidence gradually emerges from still to be completed data analysis," says CSIRO's Mr. Phil Cheney, leader of Project Vesta.
A preliminary examination of the behaviour of experimental fires conducted during Project Vesta has raised a number of important points that include:
Firefighters are advised to:
"The weather has not changed and the present manning levels based on experience should be still applicable'" he says. "Likewise, the degree of suppression difficulty at each fire danger class is the same as it always was. However, forest fires have a considerably higher potential rate of spread than that predicted by the table on the back of the meter."
The fire spread table in McArthur's Forest Fire Danger Meter was derived from relatively small fires of intensities generally less than 2000 kW/m and observational reports of spread of wildfires, says Mr Cheney. McArthur's table may still predict reasonably well during the first hour of development of a fire if the head fire remains narrow - but be aware that there could be a sudden jump in fire behaviour if the head fire becomes wider. Under prescribed burning conditions satisfactory results will be achieved using the accepted prescribed burning guide.
"We have a great deal of analysis to carry out on the Project Vestadata but the above warnings stand out," says Mr Cheney. "There appears to be a complex interaction between the fuel structure (litter, shrubs, and bark), wind speed, and fire spread and it will be at least two years before we can quantify all the important variables."
Reprinted here with permission from:
CSIRO Forestry and Forest Products