Investigation of damage: Brisbane 27 November 2014 severe storm event

Between 2 and 6 pm the on the 27th of November 2014 severe thunderstorm activity was observed in the South-East Queensland region. Two adjoining storm cells moving in a northerly direction subjected Brisbane and neighbouring suburbs to severe hail, damaging winds and localized flooding. A maximum gust wind speed of 141 km/h was measured at Archerfield Airport during this event. However, from wind field analyses and field observations, speeds were estimated to be approximately 40 to 80 km/h in other affected suburbs. Severe hail accompanied the storm (40 mm diameter typical), with hail damage to windows being widespread. Street and house surveys were conducted between the 28th of November and the 5th of December to assess structural damage and to compare overall impacts of the storm to what was reported by journalists and social media. An analysis of damage severity in relation to construction materials was then performed allowing patterns of housing stock vulnerabilities to be examined. Hail damage to windows and subsequent water ingress was particularly high, especially for older housing, with older window glass performing poorly against the wind-driven hail compared to newer window glass. Another contributing factor was most likely the significant horizontal component in the trajectory of the hail caused by the strong winds. Although winds were lower than design level, some cases of severe roof failures did occur. On several occasions, these failures were due to: (i) building age with rot in timber roof members and/or corrosion of connections or (ii) installation of new roof cladding without upgrading the batten to rafter or rafter to wall tie down connections to contemporary building standards. Roof structure damage was typically associated with a breach in the windward wall allowing a large increase in internal pressure and adding to the external suction loads on the roof.\u