Raising public awareness – Increasing community safety

In June 2016, as a world first, engineers conducted a flood demonstration at the School of Civil & Environmental Engineering’s Water Research Laboratory (WRL) with real, life-size cars.

As WRL Director Professor Ian Turner notes, “People die in their cars in floodwater with shocking frequency in Australia. WRL was already undertaking research into the stability of modern vehicles in floods, research led by WRL Principal Engineer and Manager Grantley Smith, in partnership with the NSW State Emergency Service, NSW Office of Environment and Heritage and insurer IAG.”

Flooding vehicle

“This research was just coming to fruition when the first June 2016 ‘super’ storm hit NSW, so when another east coast low was due to hit a couple of weeks later, we felt a strong obligation to raise public awareness about the dangers of driving into floodwater and took the research straight to the media. The story was incredibly effective.”

The resulting footage and interviews with WRL engineers featured on all seven national TV news networks and was covered in over 500 stories in online and print publications:

The tests themselves were a world first. Previous experiments to understand the force of floodwaters relied on using vehicle miniatures, rather than actual cars. Even the WRL engineers were surprised how easily cars weighing more than a tonne quickly became buoyant and unstable.

“What was surprising” says Grantley Smith, WRL Principal Engineer,”was just how little water it took to make even a large vehicle unstable. They became vulnerable to moving floodwaters once the depth reached the floor of the vehicle. Even in low water depths and slow flow speeds, floodwaters had a powerful enough force to make them float away.”

Even slow-moving water packs a powerful punch

A small car, weighing 1.05 tonnes, was moved by water only 15 cm deep and with a flow speed of 1 metre/second (or 3.6 km/h). It completely floated away in 60 cm of water. Even a 2.5 tonne 4WD can be rendered unstable by floodwater 45cm high, and a similar flow speed of 1 metre/second. Once the water reaches 95 cm, the four- wheel drive can completely float, and needs almost zero force to move it by hand.

By contrast, an able-bodied adult is much more stable in flowing water than the 4WD vehicle.

“Part of the reason,” explains Smith, “is that modern cars are made so airtight for comfort reasons. They more easily float when encountering water. Another factor is that people underestimate the power of a swathe of moving water.

“People don’t realise that even slow-moving water packs a powerful punch,” said Smith.“Water is heavy: each cubic metre weighs about 1,000 kg.”

WRL hopes the impact of their research will continue – as a public service warning. Beyond that initial media interest, notes Turner,” there have been some heavy rainfall events since June 2016. and each time in the media there has been a specific reference to our research and a reminder of the dangers of driving into floodwaters.”

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