Ginninderry, the 6 Star Green Star Community-rated development being built on the NSW/ACT border, could be at greater fire risk than has been estimated, according to a leading bushfire scientist.
Dr Jason Sharples, a UNSW Canberra specialist in bushfire risk management, was commissioned by community group Ginninderra Falls Association to produce a report on the fire risk of the development, as part of a campaign that seeks to stop progress on the project on ecological grounds.
Dr Sharples told The Fifth Estate that the risk of bushfire in the Ginninderry region had been seriously underestimated.
“My concern is people are going to be going into houses thinking that they are going to offer them protection,” he said.
Is the standard at fault?
However, the issue isn’t just with one development; it’s with a standard that doesn’t reflect the latest science – calling into question the safety of other developments in bushfire-prone areas.
“The risk assessments that have been done on Ginninderry are fully compliant with the standard. The concern I raise is whether the standard is compliant with the science,” Dr Sharples said.
“The standard is predicated on the assumption that fires will behave in a certain way.”
However the research he has done has shown that in many circumstances fires will behave at odds with those assumptions.
Major flaws in the Australian standard of constructing in bushfire prone areas – AS3959, the report finds, includes:
- being based entirely on the assumption that fires propagate in a quasi-steady manner
- being predicated on the notion that the main cause of house loss is radiant heat exposure
- factoring in the effect of embers in an over?simplistic way via an assumed relationship with radiant heat exposure
- offering no consideration of the potential effects of pyrogenic winds
Dr Sharples said many of the damaging fires Australia has recently suffered had been driven by processes that “invalidate” what the standard assumes is behind them.
Things such as steep slopes – a feature of the Ginninderry development – and how they align with prevailing winds and fuel loads were extremely important in determining risk.
“By contrast, the standard addresses the risk by looking at distance of vegetation regardless of direction.”
Dr Sharples said the standard assumed that radiant heat was the main cause of homes burning down. He points to the Duffy, Canberra fire of 2003, where research by CSIRO found there was only a tiny proportion of houses damaged by radiant heat – and this was caused by nearby homes that were already on fire. The major cause, he said, was ember attack.
He said the current standard says a distance of more than 100 metres between vegetation and homes is enough to reduce the risk of ember attack, though the report said half of the houses lost in the Duffy fire to ember attack had been separated by more than 100 metres from the forest edge.
“Findings from the Canberra bushfires show that ember attack is a much more significant risk. The Ginninderry development will be particularly prone to ember attack in a bushfire.”
The report said there was a lag between what is accepted as best practice and what the science said, due to both the nature of the scientific process and difficulties associated with altering statutory regulations.
Report questioned by original fire strategy creator
The person behind the original bushfire management strategy, EcoLogical’s Rod Rose, said the findings were “just a report of one person to a lobby group”.
He told The Canberra Times he disagreed with the premise that the current standards were not adequate, and said using data based of the Duffy fires as a predicator for Ginninderra was an oversimplification.
The Ginninderra Falls Association, which has opposed the Ginninderry development, is using the report to pressure Yass Valley Council to delay rezoning part of the staged development in its jurisdiction.
“This bushfire report indicates that prior to the Yass Valley Council rezoning land for housing, a more thorough assessment of the threat from bushfires is needed,” Ginninderra Falls Association’s Robyn Coghlan said.
“Therefore, the rezoning should be delayed until we have the full picture”.
The group is concerned that rezoning the land could put future residents in danger and also lead to additional pressure to burn the surrounding forest to protect homes, “putting the fragile ecosystem and threatened species at risk”.
The development received a 6 Star Green Star Communities rating partly because it is setting aside more than a third of land as a nature conservation corridor, and will feature community gardens and a “green link” incorporating edible verges and gardens.