Cyclone damage and temporal changes to building vulnerability and economic risks for residential construction

A risk analysis procedure is developed to predict economic risks due to changes to existing housing vulnerability over time. The wind hazard and building vulnerability models are based on exposure of residential construction to cyclones in North Queensland, Australia. A feature of the building vulnerability model is that it includes the effect of enhanced (post-1980) building standards in North Queensland. A cyclone damage risk-cost-benefit analysis is then used to assess the economic viability of strengthening existing houses to post-1980 construction quality for temporal changes in economic risks for two scenarios: (i) retrofitting pre-1980 houses to post-1980 quality immediately after they experience cyclone damage, or (ii) rate of growth of the proportion of post-1980 construction. The cost of retrofit or additional cost of strengthened construction can be included in the risk analysis to help assess the economic viability of these and other scenarios. Results are given in terms of annual and annualised economic risks and the damage loss conditional on occurrence of an Average Recurrence Interval event. The annualised economic risk is a time-variant measure of risk that is influenced by temporal changes in building vulnerability, which can be used to help determine the time when a particular strengthening strategy will be economically viable. “Zones of economic viability” determine the potential for cost-effective retrofitting of residential construction. The risk analysis also enabled the time to economic viability to be calculated.