Citation

Kuhnel I, Coates L. Nat. Hazards 2000; 22(2): 117-138.

Copyright

(Copyright © 2000, Holtzbrinck Springer Nature Publishing Group)

DOI

unavailable

PMID

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Abstract

The interannual variability of flood, bushfire and heatwave fatality data for eastern Australia during the period 1876-1991 was analysed with respect to the phase of the El Nino-Southern Oscillation (ENSO) and the associated values of the Southern Oscillation Index (SOI). Heatwaves were found to be the most serious peril in terms of the total number of fatalities, while floods ranked first in the fatality event day statistics. None of the three monthly (absolute value) fatality data sets showed significant correlations with the corresponding values of the SOI, while the correlation analysis of annual (July to June) data led to significant correlation coefficients of 0.5 for floods and -0.3 for bushfires. Additional SOI value-related classification of the standardised fatality event days into several ENSO categories confirmed the correlation trends by showing an increase (decrease) in the standardised bushfire (flood) fatality event day frequencies with increasing values of the SOI. In contrast to that, the standardised heatwave fatality data showed an inconclusive distribution pattern, which hints at the influence of other possible factors (such as air pollution) on heatwave-related fatality numbers. The results of a risk assessment analysis have shown that the probability of reaching the mean annual number of flood-fatality event days is roughly four times higher during La Nina seasons (80%) than the corresponding probability associated with El Nino periods (18%). The corresponding probabilities associated with the mean bushfire and heatwave fatality event days displayed a reversed pattern, with the probabilities of El Nino-related years being roughly twice as high as those associated with La Nina seasons (70% and 30% for bushfires, and 60% and 25% for heatwaves, respectively). Further probability calculations performed on the totals of fatalities from all three perils identified the La Nina years as potentially the most dangerous in terms of suffering fatalities from these perils. Furthermore, they highlighted the significant differences between the means of fatality event day numbers recorded during years of extreme SOI values (9.8 for La Nina, and 9.1 for El Nino seasons) and those marked by near-zero SOI values (6.6). The major reason for the increase in risk associated with extreme ENSO phases was the higher variability of these perils during the respective seasons.

Language: en