Buildings damaged by the "relatively low wind speeds" of ex-Tropical Cyclone Alfred have revealed what aspects will need to be drastically improved so communities can continue to function after future cyclones, according to a new report from James Cook University and Natural Hazards Research Australia.
The JCU Cyclone Testing Station's report into the impact of ex-Tropical Cyclone Alfred lays bare how southeast Queensland and northeast New South Wales effectively "dodged a bullet" thanks to the weakening of Alfred into a tropical low just prior to landfall.
But even wind speeds of around 100km/h across the impacted zone were enough to reveal several failings in weatherproofing systems, cladding, glazing, and pedestal-mounted balcony pavers.
Natural Hazards Research Australia CEO Andrew Gissing said research in the immediate aftermath of a natural hazard like Alfred was critical to ensure lessons are learned.
"This research shows that while the damage from ex-Tropical Cyclone Alfred was less severe than expected, large parts of this was due to a combination of meteorological factors. Southeast Queensland and northeast New South Wales may not be as luckily next time," he said.
"This research shows some great ways forward to improve safety and resilience against future tropical cyclone threats that we know will be faced in the future."
Report co-author and Cyclone Testing Station Chief Engineer Dr David Henderson said the weaker than expected impact of Alfred presented valuable lessons into how residents, building owners, and communities could better prepare for future cyclones in southeast Queensland and northeast New South Wales.
"One of the things that we want people to understand is that this was a great practice run in the event a stronger cyclone does eventually arrive in this area. This has happened in the past," Dr Henderson said.
"Thankfully, these are rare events but they have a massive consequence if they do impact the coast. There was the Great Gold Coast Cyclone of 1954 that caused loss of life and significant building damage and in the 1970s you had cyclones Zoe and Wanda that made a close approach to southeast Queensland.
"During ex-Tropical Cyclone Alfred, there was minimal structural damage to buildings but we still learned a lot about water ingress, waterproofing, and resilience of fire systems because of water getting inside buildings.
"There were also people who had issues with not being able to work, being inconvenienced by flooding, and experienced a loss of power."
The report has made 15 observations for improvement on how to mitigate the impact of future tropical cyclones in the region, centred around the topics of:
* weatherproofing for buildings,
* selection of corrosion resistant materials for hidden structural elements,
* fastening balcony pavers,
* communications about future tropical cyclones in the area,
* and resilience measures for tall buildings.
Dr Henderson said the failure of some glazing, cladding, and pedestal mounted balcony pavers on tall buildings at Alfred's relatively low windspeeds was a concern.
"It was an eye opener to have 15kg balcony pavers starting to lift and move around on these modern engineered, commercial structures in an ex-tropical cyclone," he said.
"On one building, lifted balcony pavers broke the glass balustrades and ended up on the street, several floors below. That's a real wake up call. If the wind speeds were higher, they would have been potentially deadly flying debris hitting other buildings."
Water entered a large number of buildings in area extending from Caboolture south and well into New South Wales during Alfred, coming through walls and closed windows.
The report emphasised the importance of weatherproofing layers on the outside of walls, stating it was vital to maintain these systems.
"The glazing industry should be encouraged to incorporate simple features in the window design that control air movement through weep holes under differential pressures across windows," the report read.
"A method of evaluating the impact of these measures should be developed to inform purchasers of windows of the effectiveness of the windows at keeping out water at pressures above the water penetration test pressure."
The report noted that while the majority of buildings in the area affected by Alfred remained functional throughout the event and immediately afterwards, many buildings were still impacted by loss of power supply, rainwater ingress, or accessibility due to flooding.
In the event of a mains power failure in mid-rise and high-rise buildings, sufficient backup power to operate a pump for subterranean basements was recommended, noting a basement's potential to accumulate water in extreme storms.
"It's also important that sufficient power was available to run lifts to enable people with mobility issues to leave their apartments," Dr Henderson said.
On the community front, residents mostly heeded warnings prior to Alfred making landfall by cleaning up their properties, despite some yards being observed with loose material, bins, outdoor furniture and shade sails – all of which have the potential to become missiles in a future cyclone event.
"For a region that doesn't have the same level of familiarity that we do in North Queensland when it comes to cyclone preparation, it was good to see people were paying attention to the messaging and were helping to protect their own and their neighbours' places," Dr Henderson said.
"However, there were some examples of construction sites with things lying around or not tied down and there were some balconies observed with things left on them.
"Overall, this event was a very good way of learning lessons without too much of the community having to suffer.
"It was a 'near miss' and we must work hard as a community not to be complacent and put in place what is needed to minimise damage in a future stronger event."
Dr Henderson, Dr Geoff Boughton and Dr Bruce Harper co-authored the report.
To read the report, head to www.naturalhazards.com.au/from-storm-to-study
