How easily cars float in a flood

Extreme weather is a fact of life in Australia and recent East Coast storms hammered people and property. A few unlucky ones have tried to drive through a dangerous flash flood and lost their lives.

Carried away

A University of New South Wales experiment in Manly Vale, Sydney, used real cars rather than miniatures to test how cars perform in water. It showed researchers just how easy it is to be carried away, even in shallow water:

  • A Toyota Yaris (1.05 tonnes) moves in only 15cm deep water flowing at 3.6 kmh and floats away at 60cm depth
  • A Nissan Patrol 4WD (2.5 tonnes) becomes unstable at 45cm deep and floats at 95cm depth.

Water is heavy – each cubic metre weighs 1,000 kilos. It exerts a strong force when it reaches the floor of a car. If you are inside the car, it’s very difficult to open the door and get out, because of the force of the water.

Elon Musk, founder of Tesla, claims the new electric Model S can almost float through deep water for short periods. Petrol and diesel cars can’t do this because the water stops exhaust fumes from getting out. But no-one should ever attempt to drive through water. It is difficult to tell its depth or the speed it’s moving.

Flood-related claims

For unlucky motorists, comprehensive insurance can cover flood-related claims, but there may be a question about who is “at fault”.

Remember your green slip does not cover property damage, only injury to a person in an accident involving your car.

You may consider taking out third party property damage or comprehensive insurance to cover damage caused by unexpected floods. Better yet, don’t drive though water. Leave this to the likes of Tesla Model S – or Chitty Chitty Bang Bang.

Corrina Baird

Writer and expert

Corrina used to lend her car to her kids and discovered first hand what Ls, Ps and demerits mean for greenslips. After 20 years of writing and research in financial services, she’s an expert in the NSW CTP scheme. Read more about Corrina

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