Geoscience Reference
In-Depth Information
the fire season has peaked in a line stretching from
Geraldton to Canberra and Sydney. By mid-summer,
the zone has moved to the southern part of the conti-
nent. At this time, hot, desiccating winds from the
interior can blow towards the coast as mobile polar
highs stall over the Tasman Sea (Figure 7.3). Histori-
cally, this is the time of severest bushfires and greatest
loss of life in Australia. Finally, the southern extremi-
ties of the continent experience bushfires as vegetation
dries out at the end of summer.
Bushfires are not necessarily restricted to the seasons
shown in Figure 7.7. In the central spring and summer
zone, severe bushfires have been known to occur in the
autumn. For example, in 1986 the worst bushfires of
the season broke out in early April following a dry
summer and record-breaking temperatures for the
month.
the fire risk; however, by 7 February, 81 fires had been
left burning around Hobart under the misconception
that rain would extinguish them (Figure 7.8). On that
day, temperatures reached 39°C with humidity as low
as 18 per cent, conditions not witnessed in a century.
The fires were driven by north-west winds in excess of
100 km hr
-1
generated by the pressure pattern shown in
Figure 7.3. By noon, fires had raced through the outer
districts of Hobart and were entering the suburbs.
By the time the fires were controlled, 67 people were
dead, 1400 homes and 1000 farm buildings destroyed,
and 50 000 sheep killed. Insurance claims totalled
$A15 million. The fires in Hobart clearly represent a
natural hazard exacerbated by human development
and attitudes. They also signify a major shift - towards
urban conflagrations - in the nature of bushfires in this
country. Urban settlements in Hobart had expanded
into hilly, picturesque bushland under the misconcep-
tion that metropolitan firefighting and water services
would be available to counteract any increased fire risk.
The unattended spot fires burning around Hobart
before 7 February stretched these resources to the
limit, scattering equipment outside the city and
Historic disasters
The worst fires in Australian history are well-
documented and have occurred in the fire-prone
belt of southern South Australia and Victoria. On
14 February 1926, fires ignited under temperatures
in excess of 38°C and relative humidity of less
than 15 per cent. Sixty lives were lost and an untold
number of farms, houses and sawmills burnt out. In
the 1931-1932 fire season, 20 lives were lost. The
13 January 1939 fires occurred under record-breaking
weather conditions. Fires raced through extremely dry
bush as temperatures rose to 46°C and humidity
dropped as low as 8 per cent. Over 70 lives were lost in
numerous fires in the south-eastern part of the country.
The 1943-1944 season was a repeat. Over 49 people
died in grass and bushfires under oppressively hot and
dry weather. Fires in the Dandenongs in 1962 killed
14 people and burnt 450 houses. On 8 January 1969,
23 people died in bushfires as temperatures exceeded
40°C and winds topped 100 km hr
-1
.
Since the Second World War, there have been four
fire events that stand out as exceptional: the Hobart
fires of 7 February 1967, the Ash Wednesday fires
of 1983, the Sydney fires of January 1994, and the
Canberra maelstrom of 18 January 2003. The last three
have occurred at decadal intervals, reflecting one of
the major climate cycles outlined in Chapter 2.
The Hobart, Tasmania, fires of 1967 were preceded
by a season of above-average rainfall and heavy growth
of grasses. As drought set in and this vegetation dried
out, numerous controlled burns were lit to diminish
N
Hobart
Source fires
Burnt areas
Wind direction
0
10
20
30
40
50 km
Extent of bushfires and location of spot fires prior to
Hobart, Tasmania, bushfires, 7 February 1967 (adapted
from Cheney, 1979).
Fig. 7.8
