Human Settlements Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Professor Peter W. Newton, CSIRO Building, Construction and Engineering, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06747 7
Liveability: environmental quality (continued)
Geohazards
Australian settlements are not without risk in relation to a range of extreme events (geohazards) that include earthquakes, landslides, flooding, cyclonic wind and storm surges. Specific examples include the 1989 earthquake near Newcastle (5.6 on the Richter scale) that caused arguably Australia's most costly 20th century disaster; the Thredbo landslide in 1997; flash flooding common to most urban communities as well as more extensive flooding of entire drainage basins and their associated settlements; cyclones, of which there are several each year in northern Australia, the worst being Cyclone Tracey in 1974 which resulted in the destruction of Darwin.
A comprehensive natural risk assessment for Australia has recently been completed by the Natural Hazards Research Centre (NHQ 2000). Nine natural hazards have been considered in constructing a relative risk rating-tropical cyclones, floods, bushfires, wind gusts, hailstorms, earthquakes, tornadoes, landslides and tsunamis (Figure 77). The relative importance (contribution) of each natural hazard has been determined largely on cumulative data on 20th century damage to buildings. Tropical cyclones, floods and bushfires are the most important natural hazards, and tornado, landslide and tsunami the least important to date.
Figure 77: Relative risk rating (RRR) for Australian postcode regions.
Source: NHQ (2000).
Table 57 shows a risk assessment for selected postcodes, comparing Darwin with several Sydney suburbs. The risk ratings indicate there is little differentiation on earthquake, but significant variation in risk across other geohazards. Darwin has a high risk of tropical cyclones and flooding, but a low risk of bushfire, wind gusts and landslides. Terry Hills and Hornsby, by way of contrast, have a relatively high risk of bushfire, as does Bondi Beach from tsunami.
| Post-code | Reference | Bushfire | Earth-quake | Flood | Gust | Hail | Land-slide | Tornado | Tropical cyclone | Tsunami | Total |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 800 | Darwin | 0.0 | 7.9 | 50.9 | 11.1 | 9.6 | 0.0 | 11.4 | 62.6 | 0.0 | 153.5 |
| 2026 | Bondi Beach | 0.0 | 7.7 | 0.0 | 10.4 | 20.3 | 0.0 | 11.7 | 0.0 | 0.7 | 50.9 |
| 2072 | Gordon | 0.0 | 7.3 | 9.4 | 10.4 | 17.4 | 1.0 | 9.8 | 0.0 | 0.0 | 55.5 |
| 2077 | Hornsby | 32.5 | 7.3 | 0.0 | 10.2 | 18.5 | 0.4 | 9.8 | 0.0 | 0.0 | 78.6 |
| 2084 | Terry Hills | 34.5 | 6.8 | 0.0 | 11.6 | 19.5 | 0.2 | 9.5 | 0.0 | 0.0 | 82.1 |
| 2135 | Strathfield | 0.0 | 7.3 | 33.1 | 9.8 | 18.0 | 0.0 | 10.1 | 0.0 | 0.0 | 78.3 |
| 2140 | Homebush | 0.0 | 7.8 | 7.1 | 7.6 | 18.5 | 0.0 | 11.2 | 0.0 | 0.0 | 52.1 |
| 2150 | Parramatta | 0.0 | 7.3 | 42.7 | 10.3 | 22.1 | 0.0 | 12.3 | 0.0 | 0.0 | 94.7 |
| Minimum | 0 | 1.7 | 0 | 1.4 | 4.8 | 0 | 0 | 0 | 0 | 16.1 | |
| Maximum | 52 | 15.6 | 53 | 19.6 | 34.2 | 65 | 17.1 | 100 | 1.5 | 162.7 |
Source: NHQ (2000).
The objective of such studies is to raise awareness and preparedness in local communities in order to minimise the potential loss of life and economic impact. In the longer term, planning strategies will need to be implemented to relocate critical facilities that are at risk, to flood-proof buildings and infrastructure to the maximum extent possible, and to ensure new development is appropriately sited.