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| Australian bushfires explained: ask your questions here | |
| (35 minutes later) | |
| Dr Andrew Sullivan is head of CSIRO’s Bushfire Dynamics and Applications Group. His research covers five key areas: fuel dynamics, fuel availability, fire behaviour, fire impacts and fire management. | Dr Andrew Sullivan is head of CSIRO’s Bushfire Dynamics and Applications Group. His research covers five key areas: fuel dynamics, fuel availability, fire behaviour, fire impacts and fire management. |
| He is online now to answer your questions about bushfire behaviour and about the current state of emergency in New South Wales. | He is online now to answer your questions about bushfire behaviour and about the current state of emergency in New South Wales. |
| Hi Andrew, what determines the direction in which the fires spread? Is it just the wind or are there other factors we should think about? | Hi Andrew, what determines the direction in which the fires spread? Is it just the wind or are there other factors we should think about? |
| Andrew Sullivan answers: | Andrew Sullivan answers: |
| Yes, it is predominantly the direction of the prevailing wind that determines the direction of fire spread. However, the direction of the prevailing wind can be affected by topographic features such as hills and gullies, etc. Topography will affect the speed of the fire (fires burn faster up hil than down hil) but will only significantly affect fire spread direction in light winds. | Yes, it is predominantly the direction of the prevailing wind that determines the direction of fire spread. However, the direction of the prevailing wind can be affected by topographic features such as hills and gullies, etc. Topography will affect the speed of the fire (fires burn faster up hil than down hil) but will only significantly affect fire spread direction in light winds. |
| Hi Andrew. From the perspective of someone from the UK, the current situation in New South Wales looks very extreme - both the scale of the fires and the extent of the warnings today about what could potentially happen. How rare is this kind of situation? And what makes it so particularly bad today? | Hi Andrew. From the perspective of someone from the UK, the current situation in New South Wales looks very extreme - both the scale of the fires and the extent of the warnings today about what could potentially happen. How rare is this kind of situation? And what makes it so particularly bad today? |
| Andrew Sullivan answers: | Andrew Sullivan answers: |
| The current fire situation is extremely serious but is not rare during the bushfire season (the bushfire season in NSW started on October 1). What is fairly unusual is the number of ignitions that have occurred to start these fires. The expected fire weather for today is amplified by the fact that there are a large number of fires already burning in the landscape and there is a great potential for more to start. These new ignitions plus the existing fires will stretch firefighting resources greatly. | The current fire situation is extremely serious but is not rare during the bushfire season (the bushfire season in NSW started on October 1). What is fairly unusual is the number of ignitions that have occurred to start these fires. The expected fire weather for today is amplified by the fact that there are a large number of fires already burning in the landscape and there is a great potential for more to start. These new ignitions plus the existing fires will stretch firefighting resources greatly. |
| How much do the fires affect air quality in surrounsing areas? Would a bad day in Sydney, for example, be as bad as smoking a pack of cigarettes? | How much do the fires affect air quality in surrounsing areas? Would a bad day in Sydney, for example, be as bad as smoking a pack of cigarettes? |
| Andrew Sullivan answers: | Andrew Sullivan answers: |
| A large active fire can produce enough smoke to block out the sun and create night time conditions downwind of the fire. Depending on where you are and your proximity to the fires, the effects of bushfire smoke can be very debilitating. There is a broad range of both particulate matter as well as toxins in the smoke that can cause major health issues in susceptible people. | A large active fire can produce enough smoke to block out the sun and create night time conditions downwind of the fire. Depending on where you are and your proximity to the fires, the effects of bushfire smoke can be very debilitating. There is a broad range of both particulate matter as well as toxins in the smoke that can cause major health issues in susceptible people. |
| If bushfires are this bad in October, what might that mean as we hit summer. Are the fires likely to continue all the way till December? | |
| Andrew Sullivan answers: | |
| It is highly possible that if the weather patterns do not moderate that these fires could burn for the next few weeks if not months. Certainly the weather that Sydney has been experiencing of late is very similar to that expected during summer months. Unless there is significant rain to dampen the fuels, the terrain where most of these fires are burning will make controlling them extremely difficult. | |
| How much do you think climate change is a factor in the bushfires this year? | |
| Andrew Sullivan answers: | |
| From the work we have done, climate change will certainly have an impact on the length of the fire season--during the warm dry years of the future, the fire season is expected to start earlier and last longer than previously experienced but is not expected to greatly affect the magnitude of fires themselves. It is difficult to say whether the current fire events are a result of climate change as we are in the NSW bushfire season. | |
| What, do you find, is the biggest misconception about fire behaviour and management. What is the most routine advice you provide, and to who? | |
| Andrew Sullivan answers: | |
| One of the biggest misconceptions about fire behaviour is that fires will create their own weather and behave totally beyond the laws of nature. Fires will influence the wind around them but if there were no ambient wind, they would not spread. Fires can behave unexpectedly but this is predominantly due to our poor understanding of the conditions in which they are burning. If we knew precisely what the burning conditions were (e.g fuels, weather, topography) we would be able to predict fire behaviour extremely well. | |
| Hi Andrew - the length of time these fires have been going on for and the amount of thick smoke in the air even many kilometres away seems worse than ever before. Is the scale of this fire unprecedented do you think? Also it seems counter intuitive to me to join two fires in order to fight them. How does this work? | |
| Andrew Sullivan answers: | |
| I'm not sure of the precise history of fire in the Blue Mountains but certainly NSW has experienced the extended periods of elevated fire weather we've seen recently a number of times in the past (December 1993/January 1994 springs to mind). I don't think the spatial scale of these fires are unprecedented, although the number of uncontained fires at this time of year probably is. | |
| I think the idea of joining the two fires in the Blue Mountains is based on the concept of removing as much fuel between the two fires under controlled conditions before the extreme fire weather returns and removes it in an very uncontrolled manner. From experience we know that unburnt fuel between two high intensity fires can result in an escalation of the fire behaviour as the fire convection columns interact and the fires coalesce. | |
| Hello Andrew | |
| Do you know how much money these fires will cost the Australian taxpayer? | |
| Andrew Sullivan answers: | |
| I don't know the answer to this question but nearly all of the people fighting them are volunteers and thus not being paid. | |
| If the worst case scenario were to occur i.e the three major fires in the Blue Mountains were to combine (something we are all hoping doesn't happen) then how do you organise an orderly evacuation of the Blue Mountains? | |
| At the moment, only the Great Western Highway is available for use by the main communities in the Mountains for travel east through to Richmond. There is also the possibility, I presume, of utilising the railway from Blackheath to Richmond. All of this does seem horribly close to a single point of failure.though. | |
| Do we need to look seriously at the logistical problems associated with an increasing population in the Blue Mountain and do we need to look at providing better infrastructure to enable the population to leave quickly if required? | |
| Michael | |
| Andrew Sullivan answers: | |
| This is a very good question and one that is pertinent to locales in Australia other than the Blue Mountains. In many places around Australia people live in bushfire-prone areas with only one path of ingress/egress which provides no alternatives if it is blocked for any reason. This is particularly important for those high population locations than can become jammed even under the best of circumstances. | |
| Andrew can you tell me how effective water bombing is in the fighting of fires? do you think it is the best way to be fighting a fire of this enormity? | |
| Andrew Sullivan answers: | |
| Water bombing is only one of the tools in the firefighter's toolkit. Waterboming in itself will not suppress fire but will reduce a fire's intensity for a period and enable other suppression tactics to be more effective. (Spotting is one of the primary causes of suppression breakdown and limits the effectiveness of even water bombing) | |
| The terrain where the fires are occurring in the Blue Mountains makes for very difficult firefighting, regardless of tactics. Under the most extreme fire weather conditions, fire suppression is highly dangerous and little can be done to control the spread of fire. Under these circumstance firefighters fall back to protecting life and property and often aerial suppression is very effective in this role. | |
| How long do the beneficial effects of hazard reduction burn last? | |
| Andrew Sullivan answers: | |
| The period of benefit from hazard reduction burning (in regard to effects on wildfire behaviour) depends on the type of fuel in which it is carried out and the intensity of the fire used to carry it out. In annual pastures, it will only last a year as the fuel grows back in that time. In dry eucalypt forest the work we've suggests that the period of effectiveness lasts from 3 to 15 years. Depending on the productivity of the site, HR burning will create a discontinuous surface fuel layer that will last 3-5 years. It can take between 3 and 10 years for most elevated fuels (i.e. shrubs) to return to their pre-fire hazard levels. Most importantly for dry eucalypt forests, it has been shown that HR burning will reduce the potential for spotting for up to 15 years. Of course, if the HR burn is of low intensity or is patchy, the effect can be much reduced. | |
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