20^thCentury Building Damage

The Risk Frontiers natural hazards database contains every known natural hazard event in Australia for the period 1900 to 1998. More than 5,000 events are included in the database and spatially referenced to a database of more than 10,000 locations. For about 1,200 of these events some information is available about building damage. For each of these events an estimate of Damage in House Equivalents has been made. For the period 1900 to 2003, total building damage expressed as House Equivalents is about 46,500; that is, total damage to buildings is equivalent to the total destruction of 46,500 houses. Figure 3 summarises the estimates, with the results expressed as the proportion of known building damage attributable to each natural peril.

Figure 3: Proportion of total building damage (1900 – 2003) attributed to each of nine natural perils (after Chen, 2004).

These data confirm that tropical cyclones and floods are the most significant natural hazards in Australia in terms of building damage and, as we saw earlier, in terms of human deaths. While bushfires occupy third place in Figure 3, this view is challenged in Figure 4 where damage from wind gusts (other than those associated with tropical cyclones), tornadoes and hailstorm damage are combined as severe storm damage.

Figure 4 suggests that thunderstorm damage to buildings is second only to that caused by tropical cyclones. The exact order of the “big 4” raises questions about the completeness of each of the databases – a discussion that it is not profitable to delve into other than to remind the reader of the comments in an earlier section about the completeness of the flood and thunderstorm portions.

In Figure 4 the four meteorological perils account for 93.6% of the total damage to buildings. Startling as this total might seem, it is the very small contribution made by the geological hazards – earthquake, landslide and tsunami – that is even more surprising. It is a sad admission for this geomorphologist to make, but the death data and the building damage data suggest that geological hazards (shouldn’t that be geomorphological hazards?) don’t count for much in Australia.

Figure 4: Proportion of total building damage (1900 – 2003) attributed to each of seven natural perils (data after Chen, 2004).