Tens of thousands of homes in the Blue Mountains would be difficult to defend in extreme fire weather conditions because of close proximity to the bush, according to research commissioned for the NSW government.
The research by Risk Frontiers was circulated to emergency services and other agencies in 2010 but not generally made public.
It found the distance of houses from the bushland boundary to be the most important factor determining vulnerability to fire, and that houses in the Blue Mountains are particularly close to bush.
“Unless a fire can be extinguished very quickly, it soon becomes uncontrollable.” Photo: AFP
Based on major blazes in the past, homes within 200 metres of at least half a hectare of bush can be considered to be at-risk properties, the research found. By that gauge, some 37,893 addresses in the Blue Mountains local government area were vulnerable, the most exposed of any region in NSW.
Research by Risk Frontiers, based at Macquarie University, found that in significant blazes in the past, the probability of loss in the first 50 metres of the bush was about 60 per cent. In the ferocious 2009 Black Saturday fires, ”60 per cent of losses occurred within 10 metres of bushland”.
Ross Bradstock, director of the University of Wollongong’s Centre for Environmental Risk Management, said the 200-metre range used to gauge risk was reasonable. He said fire chiefs including Rural Fire Service commissioner Shane Fitzsimmons had raised similar estimates of properties exposed in the Blue Mountains at a briefing in Katoomba in September last year.
Some 30,000 homes were within 100 metres of the bush in the region, officials told that meeting, Professor Bradstock said. The Blue Mountains ”has long been recognised as a problem” because of its ”ribbon” pattern of developments, with houses often scattered along ridges – an exposure clearly revealed over the past week, he said.
”The area that burnt last week was just classic 1960s-’70s ridge-top development in the Blue Mountains,” Professor Bradstock said. ”You’ve got single streets going down ridges with properties backing into bush.
”Those developments would not be allowed now,” he said, adding that ”things changed dramatically in 2006” when new planning rules required perimeter roads and setbacks from vegetation, among other requirements.
Risk Frontier’s report, Future Vulnerability to Natural Hazards in NSW, found fire-fighting efforts on extreme fire weather days are likely to have only a limited effect. ”Unless a fire can be extinguished very quickly, it soon becomes uncontrollable,” the research found, noting earlier work suggesting only a 15 to 30 minute window for crews to suppress a blaze.