Big Weather (and how to survive it) - the dangers of floodwater

With the BOM forecasting a wetter than average summer, it’s timely to remind ourselves of the dangers of floodwater. Every year floods cause enormous damage and loss of life on a global scale. While flood fatality rates are generally falling per capita, the number of fatalities that occur in vehicles, particularly 4WD vehicles has increased in the last fifteen years.

ABC’s “Big Weather (and how to survive it)” aired last night and provided great summary of flooding dangers, what to avoid doing and what to do if you’re unlucky enough to be caught in a flooded area. WRL Director of Industry Research, Grantley Smith, discussed the dangers with host Craig Reucassel.

“The main danger when it comes to flooding is when people decide they need to go somewhere; and go into the floodwater… Floodwater is really powerful. An Olympic swimmer can swim about 2 metres/second in the hundred metre final at the Olympics - and most floods in nature are going between 2 and 5 metres/second”.

WRL Director of Industry Research, Grantley Smith, and Craig Reucassel discussing the dangers of floodwater

By contrast, WRL research has shown that an able-bodied adult is more stable in the flowing water than a 4WD vehicle. In 2017 WRL completed world first testing of cars in floodwaters - eye opening research where the results surprised even our engineers at just how quickly the cars became buoyant and unstable. Even in water depths as low as 15 cm, floodwaters moving swiftly had enough force to push small cars around. In deeper waters, a 2.5 tonne Nissan Patrol 4WD can be rendered unstable by floodwater that is 45 cm high, with a flow speed of 1 metre/second. Once the water reaches 95 cm high, a 4WD this size completely floats, needing almost zero force to move it by hand.

To find out more about WRL’ s research, and read the report on “Vehicle Stability Testing for Flood Flows”, visit: https://www.wrl.unsw.edu.au/news/vehicle-stability-testing-for-flood-flows

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