Bushfire Protection, VCAT, Fallibility and Fairness

I'm revisiting my posting "Truth, justice and the Australian way or is it?" on 10 October 2016, to further discuss the performance of VCAT in its dealing with the two reviews I included in that posting.

First, whilst I may not always agree with the position taken by the CFA in its dealing with Bushfire Management Overlay (BMO) statements as part of planning permit applications, particularly when it comes to tree removal and the one-size-fits-all approach by some of its people, if the permit applicant is willing to accept the CFA's conditions then that should be the end of it .

From the 10 October posting:

In both cases people were wanting to build a home on their land and had much to lose. Would the two examples meet a fairness test or would they fit a definition of 'kangaroo court'?

Both cases involved considerable cost getting to VCAT and in the aftermath further considerable loss due to being left with devalued or even worthless land and broken dreams. And, it seems, a who-cares attitude by government or its minions.

How did it come to this?

Concerning Weingartner v Nillumbik SC [2016] VCAT 1359 (15 September 2016) despite the permit applicant satisfying the CFA with his BMO statement covering wildfire management, Nillumbik Shire Council — or its town planner planning department — decided not to accept the advice of the CFA and used wildfire risk as part of its grounds for refusing to issue a permit.

Rather than repeat myself, in commenting on the propriety of the appeal process in affirming Council's decision not to issue a permit the same comments apply to the Nillumbik Shire Council using wildfire as part of its permit refusal grounds.

Citing parts of the Weingartner v Nillumbik paper by numbered paragraph:

41. Although the CFA has undertaken its own assessment of the proposal, I am not persuaded that the measures proposed by the CFA conditions will overcome the difficulties of constructing a dwelling in an area which the CFA has assessed as being subject to significant risk on days of extreme bushfire weather. Underpinning the revised bushfire provisions gazetted in July 2014 is the necessity to prioritise the protection of human life over other policy considerations and where appropriate, to apply the precautionary principle when assessing the risk to life, property and community infrastructure from bushfire . My emphasis).

Let’s consider what VCAT has to say in para 41. First, the italicised “I am not persuaded ” in the first sentence is my emphasis.

Questions exercising my mind, what was the basis of the conclusion that I am not persuaded that the measures proposed by the CFA conditions will overcome the difficulties of constructing a dwelling in an area which the CFA has assessed as being subject to significant risk on days of extreme bushfire weather.

Where was the CFA so wrong in its assessment of the risk that it failed to not support the application rather than recommend risk mitigating conditions? In coming to this conclusion did VCAT take into consideration the effect of terrain on wind direction and speed — did it set up wind recording instruments under various wind directions that closely replicate wind on days conducive to the outbreak and spread of wildfire in the immediate area of the land involved — effect of upslope and downslope on fire spread and intensity? Did it do any destructive fuel sampling on and adjacent to the land in question to determine for itself the contribution of fuel to fire spread and intensity?

Begs the question, was VCAT qualified to come to such a conclusion? The following two photographs are of a house in the forest north of Lancefield that withstood the 2015 fire. Together with appropriate defensive space, this house was designed and constructed to withstand severe ember attack, high level radiant heat flux and the brevity of any passing flame contact consistent with wind speed likely to be experienced on that land. Further, it survived unattended.

Yet another example of fire not extending into the tree canopies .

There are numerous other well-prepared dwellings around Victoria that have withstood severe wildfire in the past. Is VCAT aware of this?

The same can be asked of the Nillumbik Shire Council in using wildfire as part of its grounds for refusing to issue a permit, for which the CFA had responded to the BMO referral by providing risk mitigation conditions.

Another issue in para 41. In the second paragraph VCAT refers to the necessity to prioritise the protection of human life over other policy considerations and where appropriate, to apply the precautionary principle when assessing the risk to life, property and community infrastructure from bushfire.

I've highlighted parts of subclause 13.05 Bushfire Nillumbik Planning Scheme where the protection of human life and precautionary principle appear under the heading “overarching strategies” and some other parts that may be of interest.

What is this “precautionary principle” to which VCAT refers? Some informative papers: “The Precautionary Principle”, UNESCO, 2005; and “Are Decision-makers Too Cautious With the Precautionary Principle?” Supreme Court New South Wales, 1999. I’m curious as to why VCAT viewed the “precautionary principle" as relevant in this case, but unfortunately it provides no explanation.

Strategy is defined in the Macquarie Dictionary Fifth Edition.

Concerning protection of human life, I’m curious as to how VCAT concluded that life safety was compromised by some other policy consideration when the CFA decided not to object subject to certain conditions. It was not a high risk subdivision proposal, but simply a family wanting to establish their home and willing to accept the CFA’s conditions.

It's also reasonable to expect that anyone willing to 'run the emotionally and financially costly planning permit application and VCAT gauntlets' will be sufficiently intelligent to prepare a wildfire survival plan that includes arrangements for the "stay and defend or leave early strategy".

Now let's consider VCAT's statements in the following paragraphs:

42. Maintenance of the defendable space in the manner required by the CFA is central to the implementation of bushfire protection measures. One of the development control strategies in Clause 13.05-1 is that new development should only be permitted where bushfire protection measures, including the siting, design and construction of buildings, vegetation management, water supply and access and egress can be readily implemented and managed within the property. (My emphasis).

I have no argument with para 42.

43. Apart from the large area of vegetation that needs to partly cleared and continually managed, I am also concerned about the practicality of achieving that management on slopes of up to 18-19 degrees. There are very few relatively level areas anywhere on the site and it is steep and difficult terrain to walk over.

and

44. In making these comments I accept that vegetation management can be more readily undertaken on the levelled areas around the dwelling, but I am more concerned about areas that are not levelled. Despite assurances that the defendable space can be maintained as required in order to lower bushfire risk to an acceptable level, I am not persuaded that level of management is practical on such a steeply sloping site.

Here, I wonder about the basis of VCAT's conclusion I am not persuaded that level of management is practical on such a steeply sloping site..

I've since been informed by the owner that he'd found a mower capable of managing the fuel on that slope. And, the CFA must have been satisfied that it could be managed.

If necessary there were other options such as a good brush cutter or maybe even on hands and knees with a large pair hedge clippers, as I trim the edges of my lawn if it gets away. Bewildering to say the least.

44. In considering the question of bushfire risk I have also taken into account another development control strategy in Clause 13.05-1 which is that the risk to existing residents, property and community infrastructure from bushfire is not increased. I have also taken into consideration local policy at Clause 21.05-2 which aims to restrict sensitive uses, such as dwellings, in areas of bushfire risk .

Let's consider how areas of "bushfire risk" are identified and promulgated. In my experience identification of "risk areas" was not done on a site-specific basis, and like the BMO was done behind closed doors.

There are areas with which I'm very familiar that the broad-brush approach by government unnecessarily disadvantages and frightens people. It seems not to take into account actual fire behaviour potential and how the risk could be reduced, in some instances with the proper application of fire prevention 'tools' in the Country Fire Authority Act. Wye River–Separation Creek is an tragic example that was promulgated as an area of "EXTREME bushfire risk" , yet virtually nothing was done to reduce that risk , which itself needs to be questioned.

Another example closer to home in this case, the government's Community Information Guide for Eltham found on the CFA's web site. To those of you familiar with the area covered by this, what is the fuel type and density in the various areas identified as "bushfire threat" that is true bush — whatever that means — or just gardens and lawns between dwellings as in the closer-settled parts of Eltham, Greensborough and Montmorency?

I could go on and on here, but I'm getting into subjects all of their own, so will end for now with the questions:

Was it appropriate that the Appellant be driven to take this matter to VCAT to get justice?

Was the VCAT process fair and reasonable as it dealt with wildfire?

Were the Appellant's human rights or property rights infringed by the VCAT decision?

Should the Appellant be entitled to compensation and from where should it be sought?

ADDENDUM 17 November 2016

Since this posting on 15 November, I’ve heard from the Appellant Stephen Weingartner. Too often the BMO losers are consigned to the VCAT dustbin without even a brief murmur of compassion and the circus moves on. I offered Mr Weingartner an opportunity to tell his story that I have included in the comments below.

Fairness? You be the judge.

The day a worm turned — or maybe it was a grizzly bear

"Even a worm will turn is an expression used to convey the message that even the meekest or most docile of creatures will retaliate or get revenge if pushed too far." en.m.wikipedia

The triumph of good over evil or action in the pursuit of the ideals of liberty, fraternity and equality or truth, justice and... Call it whatever you will, but a 'worm turned' at the recent Nillumbik Shire Council election following a large group of ratepayers banding together to get candidates whom they believed would better represent the interests of landholders if elected to council.

This group opened their own Nillumbik PALs - Pro Active Landowners Facebook page and it has been refreshing and encouraging to witness a community band together to overcome adversity. Adversity?

While there are probably other issues that caused dissatisfaction, I'm aware that a move by the former council to further control the use of private land through the introduction of proposed planning scheme amendments C81 and C101 caused this 'worm to turn' ... with due respect to the Nillumbik PALS, more a grizzly bear than worm.

And how did the 'worm turn'? Nillumbik Shire is comprised of seven Wards, with one councilor representing each Ward. Of the seven, five are now represented by councilors, being candidates supported by the Nillumbik PALs - Pro Active Landowners. The new Mayor and Deputy Mayor were supported by the Nillumbik PALs. And this from the Council Twitter account last Friday about the new Council .

What of the fate of the planning permit amendments that were the catalyst for the ratepayer backlash:

Photo by Nillumbik PALs - Pro Active Landowners

One incensed ratepayer who would be affected by proposed Amendment C101 appealed to VCAT. Here is the result of Parsons v Nillumbik SC [2016] VCAT 1898.

And this from the Council Twitter account last Friday confirming about the fate of C101.

Study Parsons v Nillumbik and draw your own conclusions. Suffice to pose the question, will senior council employees involved need to consider their positions?

Also in the mix is the abysmal manner in which the shire planning department, corporate CFA and VCAT have treated many dealing with the Bushfire Management Overlay (BMO) as part of planning permit applications.

I have first hand experience with the unnecessary and very costly difficulties or discouragements imposed on some people seeking to build on their land in Nillumbik Shire, and for no valid reason as far as wildfire protection is concerned.

Who knows what will be found if the new council decides to illuminate the darker recesses of the administration. Being intimately aware of some of the goings-on, to me "Watergate" does not seem an exaggeration.

I decided to post this as encouragement to others e.g. the people of Wye River-Separation Creek at the mercy of governments and insurers while trying to recover from the Christmas Day fire.

Nillumbik, an example of people power!

Again, I would welcome feedback.

Truth, justice and the Australian way or is it?

Maybe slightly off topic from the promised follow-on from the 4 October 2016 posting, but nevertheless worth airing in the public interest.

Here are two VCAT decisions that involve the BMO and bushfire protection, one in which I was involved in 2013 and a more recent decision that has come to my attention.

In both cases people were wanting to build a home on their land and had much to lose. Would the two examples meet a fairness test or would they fit a definition of 'kangaroo court'?

If you have an opinion feel free to express it in the comments provision at the foot of this posting.

Trees and wildfire - damaging mythology, just plain ignorance or self-serving risk avoidance

On commencing this blog on 16 February 2014 my intention was to assist people having difficulty with the Bushfire Management Overlay (BMO) considering the frustration I was encountering from the CFA and some councils in representing some of my clients and well aware that there were and continue to be others in the community experiencing similar difficulties.

The basis of dealing with the BMO as part of a planning permit application should be understanding fire behaviour, lacking in much of the community, and seemingly in part of corporate CFA when it comes to dealing with BMO referrals.

CFA promulgates its attitude toward the BMO at this time in a one-size-fits-all set of bushfire protection conditions, regardless of the actual conditions that contribute to fire behavior likely to affect a dwelling the subject of a specific planning permit application.

This attitude seems to be premised on a statement on the first page, penultimate paragraph, second sentence of the standard planning permit conditions: "Any justification for a tailored response should be included in the application". Why, who makes the decision and on what basis? More about this attitude later, but back to trees and wildfire now.

In the standard planning permit conditions there is a one-size-fits-all requirement under the heading Defendable Space stating that "the canopy of trees must be separated by at least 5 metres".

An arbitrary five metres canopy separation usually generates a planning permit condition requiring offsets that can be very costly to someone trying to establish a new home — many thousands of dollars, approximately $120,000 in one situation I'm aware of. Imagine the impact of that extra cost on a young couple trying to establish their dream home.

Raises the question, why would the CFA require a blanket canopy separation, is it because canopy or crown fire is not well understood by some CFA people making policy and dealing with BMO referrals? Hopefully the following will help.

Some examples to get the subject started.

In a blog posting on 23 April 2016 I included the following photographs from Wye River in the aftermath of the Christmas Day fire where crown fire was virtually non-existent. Observe the unburnt vegetation virtually to ground level.

And, what better than some examples from Ash Wednesday 1983. The following are from my collection photographed in the Lerderderg State Park a few days after the Trentham East fire. They show the effect of the fire at the time it was still heading in a generally southeasterly direction towards Bacchus Marsh and prior to the wind change to the southwest much later in the day forcing it towards Mount Macedon.

Above is a view of Firth Park in the Lerderderg State Park showing an absence of crown fire in the forest in the background. Note the singed trees or shrubs in the foreground.

The following two photographs are further south from Firth Park towards Bacchus Marsh.

What is particularly significant about these two apart from the lack of crown fire? Observe the unburnt shrubs/suckers at the base of the trees!

Below from my blog posting of 22 June 2014 are two examples of trees and shrubs in the path of the 9 February 2014 Gisborne fire as it travelled northeast towards Riddells Creek after the wind change.

The fire weather conditions this day were described as being the worst since 7 February 2009 (Black Saturday). Again, observe the vegetation close to the ground left unburnt when the fast moving grass fire passed.

The evidence is that crown fire is a relatively rare occurrence.

To quote Professor Julius Sumner Miller, "Why is it so?" The answer is in the fire triangle.

I will continue this theme in my next posting. Meantime, those of you who have or are still grappling with the BMO as part of a planning permit application may find the BMO Amendment VC109 July 2014 Explanatory Report of interest — ninth dot point on page 2 "remove their veto power" read the "CFA". It does not seem to be working in the manner then Planning Minister Guy intended, or maybe it is?

People grieving over the loss of trees in Wye River-Separation Creek may also find this posting of interest and it raise some questions.

The nature of bushfire Part 3 ... how fire moves across the land

I’m back with more to say on wildfire management after a break in Scandinavia and Scotland, with a few days in Berlin to learn about the rise and fall of the Wall or as the now defunct East German government or GDR named it, the "Anti-Fascist Protective Wall".

On the GDR side in a somewhat macabre outdoor museum and memorial to those who lost their lives trying to escape to the west.

While in Berlin I also took the opportunity to visit the Stasi Museum, formerly the Stasi headquarters. Stasi was the GDR's very secretive security organisation that had wives spying on husbands and vice versa, etc, etc and virtually everyone reporting on someone.

Chilling in many respects and I can relate the behaviour of the dictator Eric Honecker and his predecessors and their unelected functionaries to the behaviour of some “public servants” back home, but maybe a little more about this later. However, I imagine there are “victims” of Victoria’s Bushfire Management Overlay (BMO) and other aspects of wildfire management or I should say mismanagement in various areas of Australia, who would see some connection.

For some, the agony goes on. Shortly after returning home I came across this story "Single mother with five children forced from home after Yarloop bushfires has nowhere to go".

Wye River–Separation Creek (Vic) and Yarloop (WA) both succumbed to the spread of embers or firebrands into the settled areas and in some cases house-to-house spread, an issue I've already mentioned in an earlier blog posting that refers to the role of "spot fires" in fire spread. How did fire enter Wye River–Separation Creek?

The four following photos courtesy of Mark Strachan, Tony Maly, Matthew Stoios, Channel 7, ABC and Hamish Blair show the fire entering the residential areas of Wye River and Separation Creek and an example of its effect. They are very instructive!

This photograph shows many small fires commencing in Wye River. The green arrow at bottom left indicates Wallace Avenue with the Great Ocean Road the prominent white-lined bitumen strip. The yellow arrows indicate "spot fires" caused by embers or firebrands falling out of the convection column forming above the area. The red arrow indicates 'Tottie's Place at Wye River' (see below) about to succumb to ember or firebrand attack.

This photograph shows houses already lost due to ember or firebrand attack in the Mitchell Grove area of Separation Creek indicated by the green arrow.

Tottie's Place at Wye River prior to the fire.

and following the fire. Note the virtually unaffected trees, and 'singed' garden plants in the foreground.

The following two photographs were taken at ‘Narmbool’, near Elaine, on 24 December 2015, a few days after the Scotsburn fire ran across the property.

The photos show the effect of embers landing in isolated patches of garden and under plantation shrubs and trees. A couple of issues to note:

1. A hot fire in vegetative mulch under garden shrubs that extended to the gate before being extinguished by people who remained to defend the structural assets. The mulch under the shrubs around the house became involved, too, and it’s not hard to imagine the outcome if there’d been no one there to extinguish the initially small fires.

2. Fires under shrubs that can only have extended into that area by ember attack. Note how the fire was not sufficiently hot to ignite the shrubs, as was the situation in much of Wye River–Separation Creek .

On staying to defend a dwelling, this video was recorded as fire travelled across a property at Anglers Rest in 2003 . Note that the passage of the fire is a series of spot fires that then move forward to spot again and eventually burn into already burnt ground, and no tree canopy or crown fire. Nothing special about this building, which now has a timber dwelling added to it.

Also, note the conditions inside the building. The man operating the hose to wet down around the building moves inside for a short period when the convective heat outside becomes too uncomfortable. All done without fire brigade assistance and a very instructive video that I'll refer to in a forthcoming posting. Suffice at this stage to say that this property was in forest or woodland, hence a lot more difficult to handle than spot fires occurring in Wye River–Separation Creek residential areas.

It is well known within within the rural fire service community or should be that most houses are lost due to ember or firebrand attack — Dr Caird Ramsay, CSIRO and Justin Leonard, CSIRO.

Why then the BAL–FZ and BAL–40 nonsense being inflicted on the people of Wye River–Separation Creek seeking to re-establish themselves after the losses of the Christmas Day wildfire? Maybe a damages class action offers an opportunity to put the state and local government people involved into the witness box and question them on their fitness for the roles they are playing and reasons for their positions. It may be that all that glitters is not necessarily gold.

The nature of bushfire Part 2 ... reality versus mythology and fuel reduced buffer zones

Continuing on from my Sunday, 16 April 2016 blog posting, but first a clarification of that post: my comment about variations to temperature and relative humidity during the summer months in the third paragraph below the “flame temperature and residence time of fire” diagram is deliberately broad. Important that we all understand and acknowledge that there are many days during the summer months when weather conditions are not conducive to the occurrence and spread of bushfire.

Convection Heating

While not usually a direct source of ignition, preheating of flammable materials occurs when those surfaces are exposed to several hours of hot wind consistent with a north wind during a period of Total Fire Ban or are subjected to hot gases generated by a fire. Simplistically, this preheating — hot air — serves to aid ignition of an unprotected building.

The diagram below from Bushfires in Australia, Luke, R.H and McArthur, A.G 1978, Australian Government Publishing Service, Canberra, illustrates flames, radiant heat from those flames, and convection beyond the radiation from the flames.

An example of convection heating is a gas fired domestic heater in the family home. The heater below from the Jetmaster website utilises two methods to heat the building, radiation from the gas flames and glowing coals and heating of fan-forced air passing over a register or heat exchanger inside the body of the heater.

The temperature of bushfire flame is finite — 1,000° to 1,100° Celsius according to Project Vesta — and the radiation from those flames decreases over distance. The distance from the predominant vegetation (defendable space) tables in Australian Standard AS 3959—2009 Construction of buildings in bushfire-prone areas provide separation from harmful radiant heat.

The temperature of the air above a bushfire, convective heating, depends on the size of the fire, the larger the fire the warmer the air. Convective heating (warm or hot air) likely to be felt at ground level requires very strong wind to keep it down and alone will not be of a temperature that exceeds the fire resistance capability of a building constructed the requirements of AS 3959—2009.

Convective heat compared with radiant heat

When considering the bushfire threat to the safety of the occupants of a building it is important to understand the difference between radiant heat and convective heating or “hot air”.

Under the heading “Duration of the passage of the fire front – how bushfires spread”, I sought to explain how fire moves across the land. The diagram is there to illustrate how quickly the fire intensity rise and fall occurs with the passing of a typical bushfire front. As I comment in the fourth paragraph, the time it takes for “the temperature to fall behind the fire front depends on the amount of heavier fuel available to burn out”.

Radiant heat

Radiant heat decreases over the distance that the heavier fuels behind the fire front are from a building and will normally not be sustained at the temperature associated with the passing of the actual fire front through surface fine fuel comprised of leaves, twigs and dry grass.

Below is an extract from the Manual of Firemanship Book 1, Elements of combustion and extinction, on radiation:

All forms of radiant energy travel in straight lines at the speed of light. The intensity [heat] falls off inversely as the square of the distance from the source of radiation [in this case fire]. This means at twice the distance the intensity is one quarter; at three times the distance, the intensity is one-ninth, and so on. The inverse square law can be understood by looking at Fig. 4.5.

The square with 1 metres sides is placed at, say, 2 metres from the source will throw a shadow with 2 metres sides on a second sheet placed 4 metres from the source. Thus the energy falling on 1 m² is the same as that which would have fallen on an area of 2 metres x 2 metres = 4 m² at a distance of 4 metres. So the energy per square metre at 4 metres is one quarter that at 2 metres, i.e. that is one quarter at twice the distance. This is important when considering the effect of radiation from the heat source such as a fire.

Manual of Firemanship, Home Office (Fire Department)1974, HMSO, London

An example of the reduction of radiant heat over distance is the depth of defendable space required to achieve a particular bushfire attack level (BAL), in this case not exceeding 29 kW/m² at the outer edge of the building across 26 metres on a downslope not exceeding 10 degrees below the dwelling to satisfy BAL–29 according to Table 2 Defendable space and construction, Clause 52.47 Victoria Planning Provisions (below) with “woodland” as the predominant vegetation.

Following the arrival of the fire front the level of radiant heat behind the fire front will rapidly become less than 29 kW/m² over the width of the defendable space to achieve BAL–29 in this case. Of course this is dependent on effective implementation of the specified defendable space vegetation management requirements for the subject land.

Referring to the explanation beneath the heading “Convection Heating”, regardless of the size of the fire further back in the “heavy fuel”, in the aftermath of the arrival of the fire at the dwelling it will increasingly become convective heat — hot air — that reaches the building. And, that “hot air” will dissipate at a rate influenced by that hot air normally rising close to where it is being generated, but of course dependent, too, on the slope of the ground involved — see the slope diagram under the heading “Convection Heating”.

Finally, referring to my 24 March 2016 posting "Bushfire attack levels and windfall financial gains" there are two photos associated with a BAL–29 dwelling on the high side of Karingal Drive, Wye River, showing dry but unburnt shrubs and tree canopy.

Following are two other examples in Wye River in the aftermath of the fire that are consistent with the effect of convective heat or radiant heat from low level flames, but certainly not sufficiently severe to warrant BAL–FZ or BAL–40 throughout the Township Zone if the Colac Otway Shire Council and the CFA had met their statutory fire prevention responsibilities.

Fuel reduced buffer zones

Questions remain to be answered by the Victorian government. Why was the privately owned land around much of the settled areas of Wye River–Separation Creek ignored pre-fire and continue to be ignored in township redevelopment arrangements? The fire hazard removal provisions in the Country Fire Authority Act 1958 exist to help achieve the fuel reduced buffer zone sought by the property owners, and earlier put to the Colac Otway Shire Council.

Why didn’t the Municipal Fire Prevention Officer Colac Otway Shire Council or the CFA Chief Officer "form the opinion" that the serving of fire prevention notices was necessary to protect life or property from the bushfire threat to Wye River–Separation Creek?

What losses and suppression costs could have been avoided if the powers available in the Country Fire Authority Act had been exercised?

Again, BAL–FZ and BAL–40 in a Township Zone as protection from ember attack and "hot air"??? What was the government thinking when it accepted that bushfire attack level assessment or was it a case of "pay the piper and call the tune"?

The nature of bushfire

As stated in the introduction my objective is to raise bushfire knowledge and assist Victorians seeking approval to build in a so-called bushfire prone area.

Having regard to the reconstruction bushfire attack levels (BAL) recently imposed on the people of Wye River–Separation Creek, my opinion that the Victorian government and some councils only reinforce bushfire mythology is strengthened.

BAL–FZ and BAL–40 in a Township Zone??? What was the government thinking when it accepted that bushfire attack level assessment or was it a case of "pay the piper and call the tune"?

Why this was done needs consideration, including the adequacy of a risk assessment that should be the basis of the town protection plan, but first some facts about bushfire behaviour — if the community is to challenge government decisions they consider unfair, dictatorial or just require more explanation at least a basic knowledge of bushfire behaviour will help.

Knowledge of bushfire behaviour is also important in deciding whether to stay and defend a property or leave early and risk losing the family home or not being allowed back to deal with ember attack immediately after the fire has lost its intensity — see the pecuniary interest provision in Section 31(4) Country Fire Authority Act 1958.

Fire Triangle

When considering the threat of bushfire it is important to understand how fire occurs and spreads.

Of the three components required to have fire: fuel, oxygen and heat, in the bushfire environment the availability of fuel (vegetation) is the only component of the “triangle” that can be managed to inhibit the spread of fire and reduce its intensity.

I will refer to the availability of “bushfire fuel” as it will affect the threat to a building in the next posting.

Duration of the passage of the fire front – how bushfires spread

To introduce realism when considering the exposure of a building to bushfire it is important to be aware of how long the building will be exposed to an actual fire front.

Basically, bushfire spreads through an environment by flames at the fire front directly igniting fresh fuel (unburnt vegetation) in its path or in the case of a building, fracturing window glass thereby allowing the fire, usually in the form of sparks and embers, to enter the interior of the building, radiation from the fire front sufficiently high enough to ignite fresh fuel, including the exterior of vulnerable buildings due to a low flammability rating of the exposed materials.

The diagram below from Flame temperature and residence time of fires in dry eucalypt forest by B M Wotton, J S Gould, W L McCaw, N P Cheney and S W Taylor, 2011, International Journal of Wildland Fire that published a report on CSIRO Project Vesta, bushfire research in Western Australia that is relevant to Victorian conditions.

The trace in the diagram shows the very limited time that the fire peaks as it passes a given point. The time it takes for the temperature to fall behind the fire front depends on the amount of heavier fuel available to burn out.

Significant in assessing the bushfire threat to the dwelling it is important to understand that a fire only lasts as long as the fuel (vegetation) available to burn — grassland will burn out much faster than forest having a heavy understory of shrubs, ferns, grasses and fallen leaves and twigs.

Ignitability of the fuel is an issue; the fine fuel such as dead fallen leaves, twigs, dry grass and fine dead shrubbery close to the ground generally contribute to the passage of the fire front — the higher relative humidity (atmospheric moisture) and lower temperature that prevail over much of the summer months will inhibit the ignition of fine fuels and subsequent fire development by increasing its moisture content and raising the ignition temperature in a run to the building.

The heavier fuels such as sticks greater than six (6) mm in diameter, fallen branches, logs and hollow trees may be ignited by the fire front but don’t actually contribute to the fire front.

Again, the trace in the diagram above shows the very limited time that the fire peaks as it passes a given point. The time it takes for the temperature to fall behind the fire front depends on the amount of heavier fuel to burn out.

Effect of slope influencing fire intensity at the building site

Slope is a significant influence on fire behaviour. Simply, fire travels upslope faster than over flat ground. Conversely, a fire will be slowed as it traverses a lengthy downslope. The diagram below from Bushfires in Australia, Luke, R.H and McArthur, A.G 1978, Australian Government Publishing Service, Canberra, illustrates the effect of slope on rate of spread of a fire.

Other contributors to bushfire behaviour

Sparks, Embers and Firebrands

The most significant method of fire spread is the ignition of fresh fuel ahead of the main front due to burning wind borne material — known as “spotting”, as in the lighting of “spot fires”. To be a threat, this burning material must be sufficiently light in weight to be carried by wind while continuing to flame or smoulder sufficiently long enough to ignite fresh fuel.

I categorise “spotting” as follows:

Embers

The transmission of light burning or smouldering material generally horizontally above ground out to a distance of 100 metres and usually in the form of burning dead eucalypt leaves and other material of a similar weight picked up off the ground, and possibly the larger forms of grass seed heads or burning stringybark from tree trunks.

Stringybark eucalypts (below), where the bark has not been given a recent “haircut” — singed by fire and leaving the bark tight against the trunk with little or no fine fibres available to be ignited — will shed sparks and embers as fire travels up the bark. In strong wind stringybarks can be a prolific source of embers over a relatively short distance until all the aerated bark has been consumed.

Firebrands

Spotting over greater distances commonly involves the bark from gum species eucalypts. Some of the gum species shed their bark in the form of long ribbons (below). Some of these ribbons hang over higher branches, are relatively light and will burn readily. As they are relatively light they are susceptible to being carried aloft in the convection column — updraft above the fire and remain alight in the column for some time before falling to the ground and starting new fires, sometimes several kilometres distant from the main fire.

In my next posting I will cover how fire entered Wye River–Separation Creek, building loss and the "adequacy" of the township bushfire protection plan.

Meanwhile the the Government ramps up its political damage control and the economic damage to the State continues — now an "expert panel" appointed, so who signed off on accepting the bushfire attack level (BAL) assessment the cause of much distress in the community? And, the economics of the Victorian government's current approach to bushfire management is an important subject in itself.