Australia

1
Australia
2
(No Transcript)
3
(No Transcript)
4
Hazards

• Bushfires
• Cyclones
• Dust Storms
• Floods
• Storms
• Earthquakes

5
Bushfires
6
What is a Bushfire?

• Bushfires and grassfires are common throughout
  Australia.
• Grassfires are fast moving, passing in 5 to 10
  seconds and smouldering for minutes. They have a
  low to medium intensity and primarily damage
  crops, livestock and farming infrastructure.
• Bushfires are generally slower moving, but have a
  higher heat output. This means they pass in 2 to
  5 minutes, but they can smoulder for days. Fire
  in the crown of the tree canopy can move rapidly.
  
• Bushfires are an intrinsic part of Australias
  environment. Natural ecosystems have evolved with
  fire.
• Many of Australias native plants are fire prone
  and very combustible while numerous species
  depend on fire to regenerate.
• In the past 40 years, major Australian bushfires
  have cost A2.5 billion corresponding to an
  average of about 10 of the cost of all major
  natural disasters in Australia between 1967 and
  1999.
• In the same period Australian bushfires resulted
  in the death of around 250 people and the
  destruction of 4,554 homes.

7
What causes a bushfire?

• Generally speaking, the greater the fuel load,
  the hotter and more intense the fire. Some types
  of grasses burn very rapidly, while larger fuels,
  such as tree trunks, do not burn as easily. The
  natural oil within Eucalypt trees promotes the
  combustion of fuel.
• Wind acts to drive a fire by blowing the flames
  into fresh fuel, bringing it to ignition point
  and providing a continuous supply of oxygen. Wind
  also promotes the rapid spread of fire by
  spotting, which is the ignition of new fires by
  burning embers lofted into the air by wind.
  Spotting can occur up to 30 kilometres downwind
  from the fire front. There is a threshold wind
  speed of around 12 to 15km/h which makes a
  significant difference in the behaviour of
  bushfires in the open..
• The higher the temperature the more likely it is
  that a fire will start or continue to burn.
• Fires pre-heat their fuel source through
  radiation and convection. As a consequence of
  these heat transfer effects, fires accelerate
  when travelling uphill and decelerate travelling
  downhill. The steepness of the slope plays an
  important role in the rate of fire spread. The
  speed of a fire front advancing will double with
  every 10 degree increase in slope so that on a 20
  degree slope, its speed is four times greater.
• Bushfires can originate from both human activity
  and natural causes with lightning the predominant
  natural source, accounting for about half of all
  ignitions in Australia.

8
Where do bushfires occur?

• For most of southern Australia the danger period
  is summer and autumn. For New South Wales and
  southern Queensland the peak risk usually occurs
  in spring and early summer. The Northern
  Territory experiences most of its fires in winter
  and spring.

9
(No Transcript)
10
(No Transcript)
11
Cyclones
12
(No Transcript)
13
Where / When do cyclones occur?

• In an average season, tropical cyclones are
  mostly experienced in north west Australia
  between Exmouth and Broome in Western Australia
  and in north east Queensland between Port Douglas
  and Maryborough. In the Australian region, the
  official tropical cyclone season runs from 1
  November to 30 April with most occurring between
  December and April.
• On average, about 10 cyclones develop over
  Australian waters each year and around six of
  these cross the coast.
• There is some correlation between cyclone
  frequency and the El-Nino Southern Oscillation
  status, with activity subdued in El-Nino events
  and enhanced during La-Nina events, especially in
  the Coral Sea.

14
Earthquakes
15
Where / When do they occur?

• Although Australia is not on the edge of a plate,
  the continent experiences earthquakes because the
  Indo-Australian plate is being pushed north and
  is colliding with the Eurasian, Philippine and
  Pacific plates. This causes the build up of
  stress in the interior of the Indo-Australian
  plate which is released during earthquakes.
• Adelaide has the highest earthquake hazard of any
  Australian capital. It has experienced more
  medium-sized earthquakes in the past 50 years
  than any capital because South Australia is being
  slowly squeezed sideways by about 0.1 mm/yr
  (Transform slip-strike)
• Australia's largest recorded earthquake was in
  1941 at Meeberrie in Western Australia with an
  estimated magnitude of 7.2 but it occurred in a
  remote, largely unpopulated area. A magnitude 6.8
  earthquake at Meckering in 1968 caused extensive
  damage to buildings and was felt over most of
  southern Western Australia. Earthquakes of
  magnitude 4.0 or more are relatively common in
  Western Australia with one occurring
  approximately every five years in the Meckering
  region.

16
(No Transcript)
17
(No Transcript)
18
Severe Storms
19
Severe Storms

• Severe weather includes
• Intense low pressure systems
• thunderstorms
• lightning
• hail
• storm wind gusts and
• tornadoes.
• Severe storms are estimated to cost A284 million
  per annum. This represents one quarter of the
  average annual cost of natural disasters in
  Australia.
• In terms of insured cost severe storms are
  responsible for more damage than tropical
  cyclones, earthquakes, floods or bushfires.

20
(No Transcript)
21
(No Transcript)
22
Hail Storms

• Hail is much more common along mountain ranges
  because mountains force horizontal winds upwards
  - orographic lifting.
• This phenomenon intensifies the updrafts within
  thunderstorms, making hail more likely.
• The Great Dividing Range in eastern Australia is
  the most hail prone region of the continent with
  south east Queensland particularly susceptible to
  severe thunderstorms, especially during the
  summer months

23
Tornados

• Although tornadoes have been observed throughout
  Australia, they occur most commonly in the
  western and south eastern parts of the continent
  and are not as rare as once thought.
• The perceived rarity was because Australia's
  sparse population and lack of detection equipment
  in the past.
• There have been more than 40 tornado related
  deaths in Australia in the past 100 years and
  there have been at least 15 confirmed or
  suspected tornadoes in the south east Queensland
  region during the past 50 years.

24
Dust Storms
25
(No Transcript)
26
Drought
27
                                                
                                                  
                                      Integrated
natural hazards risk map of Australia using six
categories with equal areas.
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)