Geoscience Reference
In-Depth Information
continent was drawn over the city and humidity
plunged due to adiabatic heating. By 2:00 pm temper-
atures had reached 40°C, humidity had dropped to
less than 4 per cent - reaching 0 per cent at one station
- and, ominously, wind speeds began to increase to
130 km hr -1 . Within half-an-hour, fires had raced out of
the mountains, through plantations of Pinus radiata
(these trees have higher biomass than eucalypts) and
into the outer suburbs of Canberra. As in Hobart
35 years before, firefighters had been distracted by
fires burning on the outskirts of the city. When the fires
reached Canberra, 1000 firefighters, 14 aircraft, 119
fire trucks, and 54 water tankers were fighting three
blazes outside the city. Only 12 pieces of equipment
were available within the urban area to cope with the
fires. The unprecedented firestorm that developed
snapped off, like a lawnmower cutting grass, trees the
size of telephone poles 1 m above the ground, flung
vehicles through the air, ripped doors off fire trucks,
deroofed houses, hurled bits of roofing tile through car
windows like bullets, and carried pieces of wood as
large as compact discs more than 12 km away. The
ground trembled and the sky was filled with a sound
similar to a fleet of 747s taking off. Fireballs slammed
into houses, palls of dense smoke spontaneously burst
into flame and, as if by magic, houses suddenly ignited
one by one like matches being lit against a reddened
sky. Daylight was supplanted by darkness, eerily lit by
the feeble headlights of fleeing cars and sprays of
racing embers. The helicopters, including an Erickson
aircrane, which had so successfully contained urban
fires in eastern Australia over the previous decade,
were helplessly grounded by the lack of visibility.
Communications between the fire command center
and field units broke down in chaos. Fire hydrants
failed, gas meters ignited torching adjacent houses,
and exasperated firefighters broke down in tears. The
fires raged for 12 hours, killing four people, destroying
431 homes, and causing $250 million damage including
destruction of the internationally renowned Mt
Stromlo astronomical observatory. It was an urban fire
that should never have been allowed to happen and
shattered any confidence that Australia had learned
from the lessons of previous fires.
fires of 1983 took more lives and destroyed more
property in scattered semi-rural communities than
Cyclone Tracy did in moving through the center of
Darwin. Dense settlement, which is now occurring in
rugged bushland on the outskirts of major Australian
cities, is increasing the probability of another major
bushfire disaster like Ash Wednesday or the 2003
Canberra fire. All too often, images of horrendous
conflagration fade within a few years from people's
minds. A drive through the outskirts of Melbourne or
the Adelaide Hills will show that houses, destroyed in
1983 because they were not fire-resistant, have been
reconstructed exactly as they were before the fire. In
New South Wales, at least 10-20 homes each year
over the last 20 years have been destroyed by bush-
fires around urban centers. In the northern suburbs
of Sydney, homes with wooden decks and exteriors
have been built up the inaccessible slopes of steep
gullies.
Throughout this topic, the 1:100-year event is
emphasized as an event that has not yet occurred in
most of Australia. Overseas, in countries settled for
longer, structures designed to withstand that same
event have been shown to be inadequate over
periods longer than 100 years. If 1:100-year bushfire
maps were constructed for settled areas in southern
Australia, many newer suburbs, as well as some of
the older inner suburbs, would obviously lie within
bushland that has undergone recurrent burning.
Oddly, just when America is abandoning pre-
scribed burning in national parks, Australia is
adopting it. This is the reverse of the pattern twenty
years ago. The debate whether to burn or not will, in
the end, be resolved by defining which policy best
mitigates loss of life. However, prescribed burning
can also kill. In the middle of winter on 8 June
2000, four volunteer firefighters died in a Sydney
controlled burn that got out of control. Similarly,
another controlled burn too close to the summer
fire season, in the Goobang National Park, burnt
14 000 hectares of farmland killing 5000 sheep and
destroying 140 km of fencing. One of the reasons
that prescribed burning has been reintroduced in
Australia is that, despite the world's best-developed
volunteer firefighting organization, urban conflagra-
tions are increasing. This volunteer service will be
severely tested and ultimately fail within the next
20 years as the urban bushfire threat continues to
escalate in south-eastern Australia.
CONCLUDING COMMENTS
Of all natural hazards occurring in Australia, bushfires
now have the potential to be the major cause of
property damage and loss of life. The Ash Wednesday
 
 
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