April 14 marked the 20th anniversary of the Sydney 1999 hailstorm. The storm pelted thousands of homes and vehicles in Sydney’s eastern suburbs that evening with cricket ball and grapefruit sized hailstones, along with heavy rain and strong winds. The hail that fell was estimated to have weighed some 500,000 tonnes.
The storm occurred outside the typical “storm season” which is taken to occur between September and March but is Australia’s most expensive insured natural disaster to date with an estimated loss, in today’s terms, of around AUD 5.6 billion. This surpasses recent extreme insured loss events such as Queensland’s 2011 floods and the Black Saturday Bushfires of 2009 in Victoria. Severe storms, especially those that bring large hail, are among Australia’s most costly forms of natural hazards.
Over 100,000 people were affected: one person died and several were injured and attended hospitals. But the real story that emerged was one of the damage caused and the disruption to lives that resulted.
Where large hailstones had fallen there was substantial damage to roofing tiles and building windows. In the worst hit areas including Rosebery and Kensington almost every dwelling in whole street blocks had been damaged. Some hailstones were confirmed to have had diameters of more than nine centimetres.
Slate, tile and fibre cement roofs were particularly vulnerable. Some 12 million terracotta tiles needed to be replaced, with supplies quickly depleted.
Damaged roofs and windows resulted in torrential rain entering homes. In the most extreme cases ceilings collapsed under the weight of saturated insulation batts. Hailstones punched holes through pergolas and outdoor furniture, often shredding gardens. Vehicles too suffered denting to body work and broken windows and some motorists became trapped in floodwaters.
Many homes became uninhabitable and some remained so for months: the construction industry was placed under great stress and interstate resources were needed to meet demand. An unusually wet and windy autumn and winter slowed the emergency response and the completion of repairs.
In total around 24,000 homes, 70,000 vehicles, 60 schools and 23 aircraft were damaged. Some 10 million dollars’ worth of tarpaulins and 9,600 km of rope were used to effect make-shift repairs.
Across the suburbs, the colour of roof tiles was replaced with an array of different coloured tarpaulins sprawling over damaged rooftops. At the peak of the response around 3,000 emergency personnel were deployed in the field and in total 44,000 calls for help were made to emergency services, requiring 12,450 personnel.
Hailstorms generating insured losses larger than AUD 1 billion dollars in Australia (in today’s values) cannot be regarded as once-in-a-lifetime events. Severe hailstorms have always been a feature of Sydney’s climate, and the costs associated with the worst of them have been huge. Losses attributed to the Sydney hailstorm in December 2018 have exceeded this threshold as have recent events in Brisbane, Melbourne and Perth with further events beyond the most recent decade.
Though the influence of climate change on hailstorms in Australia is uncertain with only few projection studies undertaken, increases in wealth and the size of Sydney and other capital cities mean that metropolitan areas are more exposed to severe storm events. Since 1999 Greater Sydney has grown by over 1.3 million people with the number of dwellings increasing around 30%.
With increasing exposure will come increased loss activity but thankfully models exist to assess hailstorm risk on a national scale. For those with access, the likelihood of the April 1999 Sydney insured loss, or similar, is easily quantifiable.
Risk Frontiers are a Sydney based research and development company specialising in catastrophe modelling and climate change risk analytics.
For more information, go to www.riskfrontiers.com