Bushfires

Summary: Just before Christmas 1993, I told my northern electronic friends ‘anybody who has Christmas in winter is a mug!’. A few days later, I had this reply from Dave Liquorice in Bristol:
‘Having just seen our lunchtime TV news it seems to have its advantages. . . Seems to be a bit of a fire going on down under at the moment, so I hope everyone is managing to be avoided by them.’
Bushfires are a regular part of our summer. In winter each year, we have control burns, small fires aimed at reducing the amount of standing fuel. Then somewhere around September, the fire authorities will all compete to be the first in print with dire warnings that ‘it's like a tinder-box out there’. This ritual apparently helps them to feel less guilty when the inevitable happens at midsummer, when property is destroyed, and lives are lost.

Here are the fires of January 1994, as I saw them then. Those fires reduced fuel levels to such an extent that the fires will not be repeated for some years. Still, what I said then will apply, time and time again, in other places, and hopefully on a smaller scale, to many another Australian December and January. Bushfires are a part of high summer in Australia.

Saturday midday:

There are fires all over the New South Wales coast. By now, we have even made it onto CNN, and the worst is yet to come. A politician, our Emergency Services Minister said last night that we will be lucky if we lose no more than three thousand homes, and he has stressed that fire fighters are to concentrate on saving property and preserving lives, including their own.

Journalists are hard at work cranking out the clichés: tinder-dry, hellish, rampaging fires, exhausted fire fighters, and all of the rest. Their labours probably generate even more heat than the fires, and inevitably, lurid reports will appear overseas. Here, I will try to give you some background to bushfires generally.

First, the biology of bushfire in Australia.

Fire is a natural part of the bush cycle. So the natural environment should survive fairly well, just so long as we don't get heavy rain, too soon afterwards. That is why the fire fighters will concentrate on saving property and lives. They will fight fire with fire, knowing that what they burn deliberately will grow back again, refreshed by the flames.

Our bush, after all, has lived with fire for many millions of years, since long before humans came here. Our bush will grow back after the fires have done their worst.

The geology and geography of urban bushfires.

When the first whites invaded Australia in 1788, they settled on flat land near the sea or on the ridges. Sydney sits on a bed of sandstone, two to three hundred metres thick, with joints running north-south and east-west. It was laid down in a Triassic delta, rather like Bangladesh today, with a huge river braiding back and forth, washing out the fines, and leaving quartz grains behind. The grains were rounded, and had probably been in an earlier sandstone somewhere else, but they settled here, almost 200 million years ago, waiting to play their part in shaping modern Sydney. Some of the sandstone beds are better bonded than the others within this ‘Hawkesbury sandstone’, but they are otherwise pretty much the same, right through the deposit.

(Hawkesbury, in case you are wondering, was a minor and rather odious 18th century English politician who had a local river named after him. The stone was later named after the river.)

In the last Ice Age, the sea level here was much lower, due to all the water tied up in the northern glaciers. Then, today's Sydney Harbour was a river valley, shaped by the jointing pattern in the sandstone. Joints, planes of weakness in the stone, were eroded into crevices which became valleys, with the more resistant sandstone forming ridges. Later, the sea level rose, and so we got a ‘drowned river valley’ with a characteristic fern leaf shape. A few of the higher ridges have a shale capping which offered rather better soil than the sand which derives from sandstone.

When the first whites invaded, they settled on the coast, then headed (a) for the flat land of the ridges, where roads were easier to build, and (b) for the richer soil on the shale-capped ridges. First, they built small farms and market gardens, then roads were built to service these, and soon the residences followed. Down in the valleys, close to the harbour, the bush was left alone. It was too hard to build roads down to there, and so people left it alone. Even today, much of the valley bush is preserved, with homes sitting on the ridges above: a sure recipe for trouble.

Fuel builds up in the bush over a period of years. Gum trees shed their bark, branches and leaves, smaller shrubs in the under-storey die and are replaced by others, so the lowest three metres is a closely packed mass of dead and drying twigs. Until they break and fall, these pieces of finely divided wood rot very little in the dry bush, and even on the forest floor, rotting is a slow business, for the sandy soil drains fast after rain.

Heathlands regenerate fast. Some of them can be ready to burn again, just six months after a major fire. Other areas can take ten to twenty years to be ready for a major burn. As a general rule, after 40 or 50 years, any area at all will be ready to sustain a ‘blow-up fire’, and we are having a few of these fires right now.

Now for the physics of bushfires. When any fire starts, it begins very slowly. It takes time to develop from a maker of smoke wisps into a maker of misery. Some thirty years ago, I used to go out and light a bushfire each afternoon, so I know about a fair amount about this topic. No. I'm not an arsonist: I was working as cheap student labour for the Forestry Research Institute. Our employers needed to find out how fires behave in the first hour or two, so we would go out with a tanker, tools and knapsack sprays.

Once we were all there, we would start a fire, mark its spread and progress, take fuel samples, measure wind, humidity and temperature, and then put the fire out before it got much bigger than a hectare (2.5 acres) or so. It was small stuff, nothing exciting to it, not unless you were a fire researcher.

The sort of fire we measured is quite safe, for it has not ‘crowned’ yet. The dangerous fire is one that roars and gusts through the tree tops, the crowns of the trees, a firestorm travelling at 50 kilometres an hour or more, leaping ahead of itself, and destroying all in its path. I have seen crowning fires cross 400 metres of open water, as the sparks and burning rubbish flew up in the roaring flames, and then tumbled down on the other side. We can expect that sort of performance over the next few days. Any footage you see on your local TV will be of these crowning wildfires. You will see flames gouting 30 metres or more into the air, searing the upper branches of gum trees, leaping across the fire breaks, and almost impossible to control until the weather improves.

Weather and bushfires

The weather is the last factor in the bushfire equation. At the moment, we have hot dry nor-westers, gusting at up to 50 knots, pushing the fires downhill as well as up. There is no rain, and no promise of any. There is little hope.

Usually, a fire front can be beaten as it crests a ridge. Fires go fast uphill and slow downhill. On the forward side of any advancing fire, you will find a wind blowing towards the flames at the front of the fire. If you can set small fires on the far side of a ridge, they will gather strength and rush up, sucked in by the fire wind from the blaze on the other side, until the small fires meet the major fire coming the other way.

In this style of fire-fighting, the major fire limps over the ridge, only to find that most of the fuel in its path has already been burned. Starved, it falters like a wounded beast, and puny men and women rush in to attack it with sprays and hoses. But with high winds, this ploy is too dangerous to attempt, as the fire lighters in its path could easily be over-run, as it leaps over the fire break they have just made.

One of the scientists at the FRI used to lie down in a tent made of space blanket material as wildfires went through. It was the only way, he said, to assess the nature of a fire front, to plant the thermocouples and other devices that he needed if he was to find out what trees experience in a firestorm. A thorough scientist, he had assessed the risks, he said, but he was plain nuts, we thought. Still, he's alive today to tell the tale, a senior and respected figure, so perhaps we judged him too harshly.

Or maybe he was just lucky. I notice that he is more to be seen on the television today than huddled in a fireproof tent in front of a wildfire. Even thorough scientists can learn the meaning of discretion in middle age. For ordinary fire-fighters, the risk of getting in close to the fires is much too great, and so we have to pray for cooler and moister conditions, when the fire will be more vulnerable to such tactics.

Fortunately, only New South Wales is under threat, and help has been pouring in from around Australia. Fire engines from Melbourne (600 miles/1000 km away), with crews arriving by air from all around the country, and convoys of 4-wheel-drive vehicles from around the Canberra (200 miles/300 km away) area have all poured in, ready to do their bit. (To put this in perspective, while we Australians see new South Wales as a small state, it is about the same size as France, about 20% larger than Texas.)

As the fires spread, my wife and I have mourned several preferred picnic spots where we tend to take gourmet food, a bottle of champagne, and a couple of good books to read in the shade beside a creek (that's a brook to most of the rest of the world). At last count, two, possibly three of our most favoured spots have been burned out, and that saddens us.

Even now, the seeds will be dropping from the woody fruits of the she-oaks, Hakeas and Banksias, and the trunks and underground stems of other plants will already be starting to shoot. In three weeks, there will be green all over the bush. In time, the bush will recover, and so will the animals. The homes can be rebuilt, and lives, so long as they have not been lost, will go on. It is all part of the natural cycle.

So is the round of recriminations that will follow, with people demanding more control burns, less control burns, or whatever. The debate will be fuelled by emotion, not by scientific fact, but that, too, is natural among human beings.

Sunday lunch-time.

The worst is over. So far, a great deal of bush has been blackened, 150 homes have been lost, and four lives, but it could easily have been 5000 homes and many more lives. Just after I prepared the first message and sent it, the wind really got up, a dry gusting horror from the north-west that ripped the drying leaves from suburban trees and sent them slithering and rattling along the streets. You can imagine what that wind did for the fires out in the bush.

Then around dusk last night, a southerly change came through, a cool change which increased the humidity, and turned most of the fires more or less back on themselves, and today the wind has eased, so back-burning is possible. There are now around 120 separate fires, and many smaller settlements are still in danger, but the worst seems to be over. We will lose more bush, we will lose more homes, and maybe even more lives, but we are starting to win.

Most of the highways out of Sydney are still closed as a safety measure, so my sister-in-law, travelling back from Brisbane will probably have another night in Newcastle, 100 km from her home, which overlooks a valley crammed with dry bush. Many others from the ‘central coast’ suburbs have been trapped in Sydney, away from their homes. Still, most of them can now rest easy, knowing their homes, if unburnt, will stay that way.

Now come the arguments. Highly uninformed arguments, if last night's news is anything to go on, with the State premier being quoted as saying we would have to look into the ‘controversial practice of back-burning’. He probably meant (or even said) control burning, for there is no real controversy about back-burning, which simply means lighting fires to be sucked into the path of an oncoming fire front. Control burning is different, but I'll tell you all about that some other time. It is a complex and emotive issue.

Injuries: many people have needed treatment, mostly for smoke inhalation, and quite a few have fallen off ladders while they were cleaning leaves from roof guttering, and hosing down the roof. A wet sloping roof can be a nasty place to be . . .

Crime: a few looters have been caught, and one 13-year-old arsonist, but there must be many more of them running around out there. The 120 fires were in many cases begun as ‘spot’ fires, but many others seem to have no known natural cause. Fire is a good servant, a bad master, a worse friend, and an implacable enemy.

Luck: while almost the entire eastern seaboard of NSW has been ablaze, the inland areas have been comparatively free of fire, and other states have been suffering severely anti-fire weather, courtesy of the same weather pattern that set us up with hot dry winds and no rain, It is, paradoxically, a weather pattern seen more often in winter, when it is quite welcome. We would have had less assistance if the weather had not been so mild in the rest of Australia.

Sunday night

Well maybe I spoke too soon. The fires are raging again, half a million hectares are gone, and no rain in sight. There can't be much fuel left, but every part of my favourite bushwalking areas has now gone. The wildflowers will be beautiful in spring 1995. [They were!]

My home is safe. As a long-time local with the right training, I had looked at the risks and selected safely before I bought our home, close to bushland, but there are many many other people still at risk. They either did not know, or believed blindly that it wouldn't happen to them.

One fire front is 120 km long. They are trying to water bomb the fires, but I don't hold out much hope for that. We need a wind shift or better still, rain. They might as well spit at the fire front, if they have not back-burned first . . .

Tuesday afternoon.

Well we have been up and down like a roller coaster ride, with the danger levels running to extremes, dropping off, and back up again. There was some rain on Sunday-Monday, enough to interfere with back-burning, not enough to kill the wildfires.

I have been working the last two days at Parramatta, west of Sydney. All seemed to be well, so I decided to swing north to look at the Ku-ring-gai Chase National Park, my favourite wilderness area.

As I drove to the coast, the car radio said the roads up there were closed again as flames jumped Mona Vale Road, getting into the bush at the top of Middle Harbour. This is a deep bushy valley with many houses above on both sides, and it could have been a huge disaster if the fire had swept down the valley. Luckily, spot water-bombing from helicopters cleaned up the small fires that were established, and ground-crew action finished them off. It was extremely close for a while there.

I diverted through Lane Cove River Park, and stopped to look at the bush near Sydney's main crematorium (which survived the fire, even though it is set in bushland!). All the ground was black, with just the occasional line of white between the charcoal twigs, where a branch or log had burned out after the fire was past. The dead trees have already dropped their seeds into the ashes, but there are no shoots yet. In the next day or two, I will get down to the Royal National Park, which is said to be 97% burnt-out.

Wednesday night.

We are still at the mercy of the weather. Overnight, three fires are expected to join up outside a small town (St Albans) and this is the biggest danger at the moment. Close to Sydney, we are holding our own, but with temperatures in the thirties (Celsius!) on Thursday, we could have flare-ups again. If there is anything left to burn, that is.

I went down to the Royal National Park, south of the city today, since it was said to be open again: I worked in the park in 1968-9 just after the last serious set of burns there, and I had a few things to check and a few photos to take. To our surprise, the park was still closed due to ‘extreme fire danger’, which seems a bit odd when it has been 97-98% burned out (the rain forest area has survived, it seems). Probably the authorities are concerned about trees which will still be coming down as they burn through.

This was a bit of a disappointment, as I had planned to take some photographs of the walking tracks. After a fire, the track itself may completely disappear, but you can see where the track went, by looking for the glint of sunlight on broken glass, either side of the route. I discovered this in 1969, the last time that "the Royal" burnt out -- I was working there in those days -- but I wanted photos to prove my point to others who doubted my claim.

(Later)

Soon, people overseas began to react to the alarmist reports in their local press. Headlines like ‘Opera House melts in flames’ and ‘Sydney Harbour Bridge scorched’ even pushed ‘Aliens ate my baby’ off the front page for a while there, and I wrote to reassure them.

Yes, we have bush within a kilometre of those two landmarks, but nothing large enough to sustain a serious fire. Not this time, not next time, but one of these years, it will have to burn.


This file is http://members.ozemail.com.au/~macinnis/fireweek.htm
It was last revised on November 17, 1996, just after the first "tinderbox" refrence in the Press for this bushfire season, and the first bushfires within smell of my home.
It was created by Peter Macinnis -- macinnis@ozemail.com.au
Text and pictures are copyright, but may be used for non-profit purposes. GIF files are available for these images on request.