Severe wind risk for Australia cities — A national risk assessment approach

This study explores a national methodology for assessing the risk that peak wind gusts pose to Australian communities. This risk has been estimated for four cities across Australia, specifically; Perth, Cairns, Brisbane and the Gold Coast. Initially the return period regional wind speeds for three second peak gusts (estimation of the wind speeds that would be equaled or exceeded within a given time period) for the four study regions were obtained from the Australian wind loadings standard [1]. In addition, updated wind hazards for two cities were considered to explore the sensitivity of the assessed risk to refinements of the hazard definition. The local effects on the return period regional wind speeds used were subsequently determined by assessing the local effect of terrain at the structure height of interest, the shielding effect of up-wind buildings and the effect of topography. These effects were numerically estimated using remote sensing techniques, digital elevation data, and formulae presented in the wind loadings standard. The return period wind speeds were determined by combining the local wind multipliers for eight cardinal directions with the return period regional wind speeds (from [1] or other source) on a 25 metre grid across each study region. A structural vulnerability model estimated the economic loss for a given site wind speed. Damage levels across each region were assessed for various return periods (50, 100, 200, 500, 1000 and 2000 years) and the associated economic losses determined. Each city data set was regressed to obtain a corresponding Probable Maximum Loss (PML) curve. Finally, the regression curves were used to determine annualized losses for each study area.