How to drive through flood water safely

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Severe flooding check before you go

Before you travel in severe weather conditions, keep up to date with the latest information.

A car engine is not waterproof

Flood water can ruin the engine and make your car a write-off.

Your car engine is likely to break down if you drive through water that is too deep if water is sucked into the engine, causing damage to the engine parts – especially the piston rods and valves.

Your car engine will need replacing and depending on the car’s age; it may be a write-off.

Hey did you know?

Unless you‘re driving a high-riding 4×4, the maximum depth most experts advise you drive a standard car through is 10cm. Modern cars are generally water-tight so they can start to float when driven through water that’s only 30cm deep.

Driving through flood water

If you encounter flood water, it’s simple: don’t drive through it unless you are sure the water is not too deep for your car.

Drive slowly and steadily to avoid creating a bow wave, and after leaving the water always test your brakes as soon as you can.

Never try driving through fast-moving water such as at a flooded bridge your car could be swept away.

  • Be careful even when the water looks shallow. Water hides dips in the road.
  • It only takes 6″ (15 cm) of water to reach the bottom of most cars sufficient to stall the car, or you might even lose control.
  • A depth of just 1′ (30 cm) of flood water can be enough to move your car, while a depth of 2′ (60 cm) of moving water can be sufficient to sweep away most vehicles.

Accidents do happen in flood water

A third of all flood-related deaths are by drowning in a vehicle, but even strong swimmers will find difficulty once they are in fast-moving floods.

  • In flood water, 1 m deep or waist high at a flow of 1 m/s (2 mph) can cause anyone difficulty standing. By the time it reaches 1.8 m/s (4 mph) everyone will be washed off their feet.
  • After 20 minutes in water at a temperature of 12°C, the deep muscle of your forearm would drop to 27°C causing a 30% reduction in muscle strength.
  • When the speed of flood water doubles, the force exerted on you is quadrupled.
  • Flood water can be contaminated and carry diseases.

Just don’t let yourself get into position – it’s dangerous and could endanger your life.


Flood water also contains hidden hazards which can damage your car, and just an egg-cupful of water sucked into your car’s engine will lead to severe damage.