In June 2016 a devastating storm struck the east coast of Australia. Evacuations limited the death toll to three, but damage to property was extensive, and some beaches suffered unprecedented erosion. However, for scientists, this was a once in a lifetime opportunity. Never before had a storm been studied in such depth, and the results have overturned thinking on the threats posed by future big weather events.
The 2016 storm was labeled a “superstorm”, but its energy was only a one in five-year event. So why did it do so much damage? According to a paper in Scientific Reports, the problem was that the storm came from the east, rather than the south or southeast as is normal in this region.
Dr Mitchell Harley of the University of New South Wales explained to IFLScience that south-eastern Australia has an “emabayed coastline” where rocky headlands jut into the sea on either side of sandy beaches. When storms come from the south, most of the power of the waves is shed against these headlands, protecting the beaches and anything built inland of them. In the case of June storm, Harley said, “The headlands did nothing.”
Climate change is likely to alter the direction of future storms. We know little about how this will change, but Harley warned Sydney could soon face the sort of storms that have traditionally hit Brisbane – and come from a more easterly direction.
Harley is concerned that while plenty of work has been done on the likely impact of sea level rise on coastal inhabitants, with some consideration of changes in storm intensity, the direction has been almost ignored.
The lessons from the 2016 event are well documented because Harley and colleagues had several days warning of the event and mobilised an unprecedented effort to document it, something he said they had been planning “for the best part of ten years” From satellites to laser ranging sensors, fixed cameras on buildings, drones and sensor buoys, no opportunity to study the storm was passed up. There were even researchers out on jet skis and quad bikes documenting pre- and post-storm conditions.
“It’s very easy to get post-storm measurements, but what is really difficult is to get snapshots just before,” Harley told IFLScience. Having done this, the team calculated 11.5 million cubic meters (400 million cubic feet) of sand was eroded from beaches – similar to Hurricane Sandy and equivalent to filling Australia’s largest sports stadium seven times over. Sydney’s Narrabeen Beach experienced 36 percent more erosion than the next worst storm in its 40-year documented history.
The data will be studied for years to come, but in the meantime, Harley warns thoughts need to turn to how to prepare for even larger storms coming from new directions.