Geoscience Reference
In-Depth Information
Hills - the worst event being the loss of 584 homes in
1923. This urban-wildfire conflict was exacerbated by
the dominance of fire-prone vegetation such as
Eucalyptus
. Monterey pine, chaparral, grass, and orna-
mental species such as junipers and cedars were also
present. All are highly flammable, generate intense
radiation, and produce easily blown embers. The fires
were aided by the weather. The region had experi-
enced five years of drought while frosts the previous
winter had increased the amount of dead vegetation in
the forest. On the day the firestorm occurred, relative
humidity dropped to 16 per cent and temperatures
rose to a record 33°C. The local föhn winds enhanced
the firestorm. These winds became turbulent over the
local terrain and reached gusts of 90 km hr
-1
. Finally,
an inversion layer developed below 1000 m, containing
within the lower atmosphere the heat generated by the
fires and preheating vegetation in front of the flames.
The disaster began as a small brush fire on
19 October 1991 in the hills above Oakland. This fire
was easily controlled, but it continued to smolder
beneath a 20 cm thick carpet of pine needles. At
10:45 am on 20 October, flames reappeared and devel-
oped into a wildfire that lasted three days and became
the worst urban wildfire disaster in United States
history. Within 15 minutes of reignition, the fire
became a firestorm that generated its own weather and
proceeded along several fire fronts. Within 30 minutes,
eight pumping stations and ten water reservoirs were
lost due to power failures. Within an hour, the fire -
spreading at a rate of 1.67 m s
-1
- destroyed 790
buildings. Local firefighting resources were over-
whelmed and a Bay-wide call for assistance was issued.
Eighty-eight fire trucks, six airplanes, 16 helicopters
and over 1400 service personnel responded to the fires.
However, fire units from outside the area found
that their hose connections were incompatible with
Oakland's hydrant system. Communications amongst
emergency services failed within the first twelve hours
as call lines became congested. The rugged terrain
interfered with radio and cellular (mobile) phone
transmissions. Abandoned vehicles, narrow roads,
downed power lines and the thick smoke trapped in
the inversion layer hampered firefighting efforts. The
same restrictions hindered evacuation of residents.
Nineteen people were killed trying to flee the fires;
eleven of these died trapped in a traffic jam. By the end
of the first day, ten key reservoirs were drained and
firefighters had to rely upon tankers for water supplies.
The fires were extinguished only because they began to
burn more slowly as they reached flatter terrain, and
because the winds diminished. After burning for three
days, the firestorms had burnt through 6.4 km
2
of
affluent neighborhoods, destroyed 3469 structures
worth an estimated $US1.6 billion, injured 150 people
and taken 25 lives.
Following the 1998-1999 La Niña event in the
United States, the 2000 fire season was conditioned
by widespread drought from Florida in the south-east
to Washington in the north-west. Across the country,
122 827 fires burnt across 34 000 km
2
- more than
double the annual average - destroying 861 buildings,
killing 11 people, and costing $US1.6 billion to
suppress. At the peak of the fire season in Florida,
more than 500 wildfires broke out each day. Eight of
the ten worst fires were concentrated in the north-
west. This situation stretched the country's firefight-
ing capacity. At the season's peak on 29 August, 1249
fire engines, 226 helicopters, 42 air tankers and
28 462 people were fighting the fires. Eventually per-
sonnel and equipment had to be brought in from
Canada, Mexico, Australia, and New Zealand. And
still the carnage intensified. In October 2003, fifteen
fires in southern California burnt out 3000 km
2
,
destroying 3640 homes and 1174 other structures
(Figure 7.6).
An aerial view of total devastation in a housing estate follow-
ing the southern Californian fires on 29 October 2003. Note
the lone house that survived unscathed (photo 031029-N-
4441P-013 taken by Photographer's Mate 2nd Class Michael
J. Pusnik, Jr., of the U.S. Navy assigned to the 'Golden Gators'
of Reserve Helicopter Combat Support Squadron Eighty Five
(HC-85). Used with permission of Director, Naval Visual
News Service, U.S. Navy Office of Information.
<http://www.news.navy.mil/list_single.asp?id=10314>).
Fig. 7.6
