Spatial Variation in Damage

The question “Which part of Australia is the most hazardous?” can be answered in many ways, but lets begin at the state level using the HE damage estimates. In Figure 5 Tsunami damage (grand total = 0) has been excluded to simplify the diagram, and at the scale of reproduction it is not possible to show Landslide damage clearly (only significant in New South Wales and Tasmania). NSW, Queensland and the Northern Territory are the states where it all happens and nothing much ever happens in the Australian Capital Territory (Canberra, and the location of the Federal Parliament). While, Figure 5 only includes data up to 1998, allowance has been made for the January 2003 Canberra bushfires in which more than 500 homes where destroyed, and for the 14 April 1999 hailstorm in Sydney, the largest insured loss event in Australian history. These adjustments mean that some minor details of the pattern in Figure 5 may be incorrect but the broad picture is a realistic representation.

Figure 5: House Equivalent damage estimates based on 1900-1998 data with adjustments for the 2003 Canberra bushfires and the 1999 Sydney hailstorm.

Figure 5 also shows the varying impact of each natural hazard from state to state. NSW has experienced a reasonably even mix of damage from flood, bushfire, thunderstorm and earthquake, whereas damage in Victoria has been much more dominated by bushfire and in Queensland, Western Australia and the Northern Territory by tropical cyclones. The Tasmanian and ACT experiences have been dominated by the 1967 Hobart bushfires and the 2003 Canberra bushfires respectively.

As Mark Twain once noted (1883): “There is something fascinating about science. One gets such wholesome returns of conjecture, out of such a trifling investment of fact”. So here we go.

New South Wales is the most populous state – it has the most buildings and so we might expect the most damage there. On the other hand, Western Australia has an enormous land area … So which state is the most hazardous when we estimate damage per 100,000 population or per unit area?

Figure 6 suggests that the Northern Territory is easily the most hazardous state or territory in Australia on a unit population basis. However, we should recognize that the head count is based on just the 2001 Census and does not reflect the changes over the century in which the damage has accumulated. This approach probably underestimates the HE per unit population for the Northern Territory and, possibly, for other states where population increase has been more dramatic in recent decades.

Figure 6: House Equivalents destroyed per 100,000 population. The same caveats on the data apply as on Figure 5.

Figure 7 illustrates that the picture is entirely different when the risk assessment is based on HE per unit area. Who said nothing ever happens in Canberra?

Figure 7: House Equivalents destroyed per 10,000 km2 area. The same caveats on the data apply as on Figure 5.

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