15 August 2019

Canberra's bushland suburban mix is highly combustible says new fire risk study

| Genevieve Jacobs
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Dr Price’s research focuses on high ignition zones in the densely settled inner suburbs. Image: Supplied.

We may be going through consecutive polar blasts at the moment, but Canberra’s unique combination of higher-density inner suburbs threaded through with bushland is a combustible mix, according to a newly developed bushfire mapping tool.

Add to that “a lot of ignition” in those areas, and Canberra’s heavily populated areas are at surprisingly high risk for bushfires, according to Dr Owen Price from the University of Wollongong.

Dr Price has used a newly developed bushfire risk prediction tool to map our biggest fuel loads and the likelihood of future bushfires in urban areas.

Initially developed in the Baulkham Hills area in Sydney, Dr Price then assessed Canberra’s risks for his work at the request of ACT Parks and Conservation.

“In the Hills district, most of the bushland is in the north and there’s a fairly clear distinction with closely populated urban areas, whereas Canberra has islands of forest within the town that my analysis highlighted as potential risks,” he says.

Dr Price points to a confluence of factors: a large concentration of houses, but also an ACT Parks and Conservation map that shows multiple recent incidences of small fires (above).

“The kindest explanation is that it’s carelessness, people tossing cigarettes out of car windows without thinking,” he says. Significantly for fire risks, Canberra’s reserves are islands of natural bush rather than controlled plantings.

Suburbs adjacent to bushland on the city’s southern, western and eastern edges are at an even higher risk than rural areas, according to Dr Price.

The Pierce’s Creek fire late last year was just a few kilometres from the nearest suburb. Photo: Jack Mohr.

His planning tool is something of a world-first, mapping bushfire risk based on objective records of past fire patterns. Dr Price believes that current prediction methods are too simple, often failing to account for varying factors like the amount, distance and direction of forest, fuel reduction from recent fires and ignition hotspots.

Dr Price’s new method considers ignition hotspots, a place’s distance from previous ignition points, the layout of forest in the landscape, time since the last fire, and the weather.

He calculated the risk to Canberra’s suburbs using data from ACT Parks and Conservation and the census. Factors included density, the direction in which houses faced, proximity to bushland and the last time that fuel sources were treated.

“The method takes planning from a heuristic approach where everyone relies on expert opinions and puts it into an objective, repeatable framework that compares one place to another. Fire agencies can then judge whether they’re putting their resources into appropriate places and whether there are any gaps,” he says.

Dr Price is quick to emphasise that there’s plenty of value in expert judgements and that his mapping method is another tool in a mix that often also includes simulator models.

“One of the key judgements is where to do fuel treatments, and this is more than guesswork and expert opinion. All methods have their drawbacks but you have to marry them all together to get the best-informed result.”

 

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Queanbeyanite5:03 pm 22 Aug 19

It was all in the recent inquest over the 2003 fires. Phil Koperberg of NSW didn’t burn off the vast area of bush to the west and the ACT person responsible did nothing. Then they didn’t put out the fires burning there for months. So when it got hot and windy it sucked the fuel up and blowtorched the south. Only the change of wind direction at 4:30pm stopped everything south of the lake going up. A couple of hankercheif sized patches not burnt is ‘peanuts’. Back then the local council tried to nobble the Coroner. For a fraction of the cost of a day’s joyriding in ‘Elvis’ you could put cool burns through the NSW side every other year. They know what needs to be done but the Greens won’t let them.

Deciduous fire retardant trees and shrubs are the answer to this problem and should be the main planting around suburbs. I heard of some fireies saying that the reason a house was saved from fire was the camellias which were planted near the windows. This knowledge must be come commonplace and the government needs to realise that this is the only sure way of protecting the city — a buffer around and within the city of fire retardant deciduous trees .

I think what they do in Victoria, allowing deadfall timber to be collected for domestic firewood, might help remove some of the fuel.

Whether a suburb adjoining a “high-risk” coded area on the map is at risk depends on factors that aren’t obvious at a glance. For example, Ainslie adjoins a red-coded area but a fire on the flank of Mt Ainslie (and there have been many) always burns up and away from the suburb. Even houses adjoining the bush in Ainslie are safe if basic fire protection steps are taken. Strong easterly winds wouldn’t get past the mountain to force a fire into that suburb. Rest easy, Burghers of Ainslie!

HiddenDragon6:21 pm 18 Aug 19

Always nice to see serious academic attention to this issue, but to a considerable degree, this is a statement of the bleeding obvious – to anyone who is not in complete denial about bushfire risk in suburban Canberra.

Work like this should make plausible deniability that much harder to maintain than was the case in 2003.

Capital Retro8:36 am 18 Aug 19

Is there a link to a clearer version of the map supplied, please?

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