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Tasmanian bushfires: should we have trusted the models?

This week the Tasmanian government released its inquiry into the January 2013 bushfires that destroyed numerous properties on the Tasmanian Peninsula. A key finding is that modelling predicted fires would…

Bushfire modelling predicted the Dunalley fires a day before they happened, but that’s not the whole story. AAP Image/News Limited Pool, Chris Kidd)

This week the Tasmanian government released its inquiry into the January 2013 bushfires that destroyed numerous properties on the Tasmanian Peninsula. A key finding is that modelling predicted fires would reach the town 24-hours before it occurred, but this modelling wasn’t disclosed quickly enough.

But putting excessive faith in bushfire modelling is a mistake, particularly as models are not yet sophisticated enough to ensure accurate warnings.

Bushfires across the island had enormous impact on Tasmania: through extensive property damage and harm to the economic, social and psychological well being of affected communities. So a thorough investigation into the causes and consequences of these fires is to be welcomed.

But the bushfire inquiry’s report and the subsequent media reportage has spread a dangerous idea – that government can provide a very high level and reliable community protection from bushfire threats with bushfire models.

Indeed, a powerful storyline in the report is that the Tasmania Fire Service failed to adequately warn communities of the immediate risk of the fires, by not disclosing findings of a predictive model quickly enough.

However, careful reading of the inquiry report undermines this simplistic interpretation about fire models, and glosses over some very serious operational issues concerning the use of bushfire predictions.

The basis for the finding is a match between the actual extent of the Dunalley fire and a 24-hour prediction of the fire spread using an Australian designed bushfire model. But one accurate prediction doesn’t mean we should trust models every bushfire season.

The inquiry acknowledged that fire behaviour is influenced by numerous local factors. These include terrain, fuel loading, fuel type and moisture, and variation in vegetation and winds. Under some conditions severe fires can also create their own weather. These factors are not perfectly captured in the current generation of predictive fire models, and in any case, the appropriate data are not always available.

The sole expert witness Dr Jon Marsden-Smedley of the University of Tamania to the inquiry - who gave evidence about fire behaviour modelling - stated that the current generation of predictive fire models are imperfect, and are based on generalized meteorological data rather that local measurements. He also stressed that fire predictions are susceptible to the effects of atmospheric instability that are not represented in the models yet.

Despite the expert advice, the inquiry found that the modelling from January 3, which predicted the town of Dunalley was at risk, should have been acted upon immediately by the Tasmania Fire Service.

Tasmanian Premier Lara Giddings at the presentation of the report on the Tasmanian bushfires. AAP Image/David Beniuk

The big concern is that such literal application of modelling will lead to “warning fatigue”. Given the limitations of the models there will be numerous false alarms, and there will be some inevitable failures to predict extreme fires. Over time people will become disconnected from fire warnings.

This is a real concern. On the morning of January 4 local communities were clearly warned that a severe fire situation had developed but many people failed to comprehend what these warnings meant, resulting in significant risks to life.

Better is to use the hard won field experience of fire fighters and rural landowners. Local expertise and field experience are critical for assessing fire risk. Indeed, one of the recommendations of the inquiry is that the Tasmanian Fire Service should place greater reliance on local knowledge from rural landowners. Putting the emphasis on modelling can take this vital knowledge away.

A key organising principle to the inquiry is that the Tasmanian government is duty bound to provide safety and certainty for citizens. The notion that models can provide perfectly reliable advance warning of threat is an appealing idea. But this can lead to a dangerous thinking with increasing dependence on the state to eliminate fire risk, including an unrealistic expectation of advanced warnings.

Failure to achieve this ideal invites blame, litigation and more fundamentally, people not accepting the responsibilities associated with living in inherently flammable landscapes.

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20 Comments sorted by

  1. Peter Ormonde

    Farmer

    I don't want to wade into the firestorm arising from the investigation other than to suggest that people should be informed when there is a credible threat.

    Up here we rely on an increasingly aging but extremely experienced bunch of volunteers for our fire fighting. And one of the more disturbing features of fires over the last decade or so is their changing nature. All anecdotal but there is a unanimous view that for the most part the fires are hotter, faster and less predictable than they…

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    1. Trevor Kerr

      ISTP

      In reply to Peter Ormonde

      Further on "the whiff of eucalyptus oil" in the air, are there any actual measures of volatiles? Gut feeling suggests that higher levels are an important factor in the 'fire storm' phenomenon. Is it possible to measure the flammability of smoke?

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    2. Mark Amey

      logged in via Facebook

      In reply to Peter Ormonde

      Peter, you are indeed the voice of wisdom!

      I remember reading a study by the US national parks on bush/forest fires. Even then, twenty years back, they reckoned that they were too unpredictable to do anything but protect life and limb, where threatened, otherwise, let 'em burn out. That was, of course, with the usual efforts at maintaining fire-breaks, fire trails, and good building maintenance.

      Like the last sentence of the essay, we must accept responsibility for living in our highly flammable areas.

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    3. Peter Ormonde

      Farmer

      In reply to Trevor Kerr

      Morning Trevor,

      I remember some studies I read from 15 years ago or so where some clever science wallahs were tooling about with various concentrations of eucalyptus oil in confined spaces ... pumping euc oil into a 1m3 cabinet and seeing what the spontaneous flash point was ... they used a measure called vapour pressure to determine the concentration (slightly complex concept from memory) but I do recall that at a 70% vapour pressure and 38 degrees C the air caught fire - no spark required. That's why I remember it.

      I'll try and track it down but I suspect it was published on highly inflammable paper rather than the interweb Trevor. Some boffin here might remember it.

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    4. Trevor Kerr

      ISTP

      In reply to Peter Ormonde

      Good one, Peter. May I, then, make a proposal? As it appears that the gum-leaf is the fatal component in fire-storms, the national Govt could act as curator for all knowledge on eucalyptus leaves and stimulate research to fill in the gaps.

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    5. Michael Shand
      Michael Shand is a Friend of The Conversation.

      Software Tester

      In reply to Peter Ormonde

      "two days of hot westerlies, two days of temperatures above 30 and humidity around 10% and particularly the whiff of eucalyptus oil in the morning air"

      This is going to become the new normal very soon and as such, we need to seriously think about other strategies to manage bush fire risk

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    6. Peter Ormonde

      Farmer

      In reply to Trevor Kerr

      I suspect that the yanks might also be of some assistance Trevor. In Califormia where eucalypts have gone feral they are routinely referred to by firefighters and park rangers as "gasoline trees" ... can't really argue with that.

      Indeed there is solid evidence that eucalypts are actually "designed" to spread fire as anyone who has sat watching spiraling pieces of burning bark raining down from an approaching fire will testify.

      Buggers of things really... but some folks insist on living…

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  2. John Newlands

    tree changer

    Oddly I discussed dome of these issues at sunrise today with a neighbour looking for lost calves. We remarked on the NSW bushfires while western Tasmania has had 10-60 mm a day of rain for the last 10 weeks Therefore we are probably in for a shocker. when it all dries out. I don't know about computer models but property owners definitely want to know where the fire front is at all times. The information source is ABC radio and the TFS websites until the power goes down. Smoke from downwind is a major source of anxiety and signal for action. The air may be smoky from a fire 10 km away due to a temporary wind shift and is often difficult to interpret.

    Perhaps the TFS website should have a real time fire map with arrows indicating the current wind direction. Presumably the model could predict fire fanned accelerating winds. My other suggestion is that secondary roads be trimmed of trees that might fall and block exit.

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    1. Michael Shand
      Michael Shand is a Friend of The Conversation.

      Software Tester

      In reply to John Newlands

      You want to setup swales, rain gardens, add compost to your local area

      All of which helps holds water in the soil for longer by reducing evaporation and creating passive water catchment systems

      you want to do this as high up a hill as you can and you want to do this around your home.

      Of course, most Australians are disgusted by any suggestion that isn't burning

      we let the rain fall off the roof, straight to the gutter, straight out to sea - A great resource is being flushed out to sea as fast as possible

      we are doing the exact opposite of what we should be doing.

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    2. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Michael Shand

      Yep, and Brachychiton species, Cussonia, cork oaks, fruit trees, if you can create a wind break for all directions, which may also soak up flying embers and create a shock absorber for a fire, that's good too. Down in a valley, the embers flying from elsewhere fire-bomb directly from above. Some basket shaped valleys are just as dangerous as ridge-lines for this reason. Looking at the total 10 km radius is prudent.

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    3. Michael Shand
      Michael Shand is a Friend of The Conversation.

      Software Tester

      In reply to Alice Kelly

      Great comment, if you get a chance, check out a doco called lessons from the loess plateua - posted on youtube

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    4. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Michael Shand

      I will when the new download month starts. (Damn them). I don't burn anything now, unlike others. It's the lignin in woody matter which improves soil. My swales start with cut up rubbish trees. Another personal gripe of mine is the over-reliance of burns in spring. Autumn is much better here because we get rain, so the burn is cool, and less wind. Better for critters too. This is probably the case for much of coastal NSW.

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    5. Phil Dolan

      Viticulturist

      In reply to Alice Kelly

      Autumn burning is a disaster for grapes. They pick up the smoke taste and all is ruined.

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    6. Peter Ormonde

      Farmer

      In reply to Alice Kelly

      Yep, restricting the spread of eucs is definitely a good idea Ms Alice and there are plenty of indigenous species that are capable of slowing a fire front. (There's an excellent list of fire resistant species in the Australian Native Plant Society's "Grow What Where" ... here's a chapter list http://www.drought-tolerant-plants.com/grow-what-where/ ).

      But given what's going on weather-wise of late I wouldn't put total faith in them. Given enough dryness and heat (coupled with wind) anything…

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    7. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Phil Dolan

      Phil, grapes don't grow well here because it's too wet in early autumn, they'd go mouldy. My suggestion is for the very eastern seaboard. I'm growing a few, and an ancient egyptian wheat, trying to get something personally. Sorry about yours, I don't know where you are. We get horrible spring winds, everyone starts fires in the last two weeks before the bans start, and then there's fires all over the place out of control. For us here autumn is better, slower, and we get heavy down-pours in between.

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    8. Phil Dolan

      Viticulturist

      In reply to Alice Kelly

      I'm down in Tassie and forestry burn off in Autumn.

      To be fair to them though, they consult and postpone if it looks dodgy.

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    9. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Peter Ormonde

      Peter, I too have experienced the impact of fire. Ash wed. was one. I no longer listen to anybody, particularly my local experts, because there are in my opinion, no longer any rules which can be assumed, during the event of fire. The local brigade have never seen the sort of fire which I have, and are liberal with local truth. My intention on the day, (and I have a good radar for conditions), is to turn the pump on, and leave for the coast in the morning. My suggestions were only how try to create a still, cooler, micro-climate surrounding a rural house, so that hopefully fire could skim over? I pay a lot of house insurance.
      25 metres away from my fence is a large cupressus belonging to my neighbour, (the psychologist), I fantasise shooting a flaming arrow at it from my side of the fence on my way out, before the front comes. Tricky policy pyromania. There are no rules anymore with the right fire. I do understand what yr. saying.

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  3. Phil Dolan

    Viticulturist

    I think the Japanese were a bit relaxed when the tsunami warnings came so I think that is a good point that people will become disconnected.

    When all is said and done though, no lives were lost so I guess it was a successful operation. Things were lost, and they can all be replaced.

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  4. Michael Shand
    Michael Shand is a Friend of The Conversation.

    Software Tester

    Unless you actually try to address bush fire properly this is all a waste of time

    ie. if all we do is controlled burns and evacuations - in less than 40 years we are doomed to be in a constant state of warning

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