Why you should never drive through floodwater
The NSW State Emergency Service has urged motorists to avoid entering floodwaters as a large part of south-east Queensland and North-East NSW prepares for Tropical Cyclone Alfred.
The rare weather event is tipped to make landfall as early as Thursday, bringing with it damaging and destructive winds, large powerful surf, coastal erosion and heavy rainfall. Moderate to major flooding is possible in Northern NSW due to expected associated heavy rainfall.
Speaking with the NRMA’s Open Road, an SES spokesperson reiterated calls for residents and motorists affected by Tropical Cyclone Alfred to avoid floodwaters altogether.
“Our safety message is do not walk, drive or enter flood waters,” the spokesperson said. “If you come across flood waters, please turn around and find an alternate route using the live traffic app. You can also stay up to date with all the current warnings listed on Hazards near me.”
Driving through flood water will likely severely damage your vehicle and could also put your life at risk.
The temptation is understandable – it’s been a tough drive and you’re within minutes of the comforts of home when you’re confronted with what looks like a relatively shallow and steady flow of water across the road.
As the SES will tell you, still waters can run deep and the flow in front of you could pack a punch of a tonne per metric metre, which can tear away the road surface and result in a much deeper gully than is apparent.
A typical car will lose power in depths greater than 15cm as water enters the exhaust and washes into the air intake, causing it to float once flood levels exceed 30cm.
Can you escape a car stuck in flood water?
Modern cars with electrically powered windows and locks are almost impossible to escape from once water finds its way into wiring and motors, disabling switchgear and pressing on bodywork.
Owners of off-road vehicles shouldn’t assume they are immune, as the fast-flowing force can overcome four-wheel drive or any other tool at their disposal.
Even if you have the good fortune to survive getting caught in a flood in your car, the damage your vehicle will certainly suffer will make you regret taking the chance.
And if you get caught in floodwaters, NRMA Roadside Assistance can't help you: not only from a safety perspective but also because damage to your vehicle suffered in this scenario becomes a car insurance issue.
We have also described the potential damage to vehicles here but the threat to life should be a good enough motivation: the US Centres for Disease Control and Prevention report that almost half of all flood-related drownings occur when a vehicle is driven into water, far ahead of pedestrian deaths.
Heavy rainfall and storms in fire-affected areas can lead to dangerous conditions such as road sediment, flash flooding, landslides, rock falls and falling trees. We urge motorists to put safety first and keep up to date on road closures through Live Traffic NSW before planning a trip.
At some stage motorists of all levels will find themselves driving in the rain. The fundamental thing to realise is that wet-weather driving demands you drive much slower, however, there are also other expert NRMA Driver Training tips to help you avoid an accident when facing wet roads. If floodwater has reached the lower level of the vehicle's doors before receding, do not turn on the engine.
Things to remember when driving in the rain
- Exercise extreme caution if a deluge has followed a long dry spell
During a dry spell, engine oil and grease collects on the road. When it rains, the surface becomes slippery. Continued rain will eventually wash away the oil, but the first few hours are the most slippery so bear that in mind. - Allow for more travel time
Traffic will be moving slower. Your normal route might be flooded or jammed, so don’t blow a fuse if it is – everyone’s in the same car-shaped boat. - Turn your headlights on
Not only will your lights help you see the road, but they’ll help other drivers see you. - Drive in the tracks of a car ahead of you
Following another car’s tracks on wet roads can reduce the amount of water between the road and your car’s tyres. Keep a keen eye on their brake lights so you can quickly anticipate their actions. - Brake earlier and easier than normal
This increases the stopping distance between you and the car in front of you and lets the driver behind you know you’re slowing down. Use you turn signals earlier, so that other drivers can read your intentions easily. - Keep an eagle eye out for pedestrians and cyclists
Visibility is lower and rain deadens sound, so the usual visual and audio cues for measuring car distances become obscured. Pedestrians are also impatient to get out of the rain so may make rash crossing decisions. - Defog your windscreen
Rain can cause your windscreen to fog up. Switch on both front and back demisters/heaters and make sure the air conditioning is also turned on. - Avoid large puddles
Water splashing up into your car’s engine compartment may damage its internal electrical systems or a pothole under the water could damage a rim or knock your suspension out of alignment. If you can’t gauge the depth, try to avoid it. After you are across the puddle, tap on your brake pedal lightly to dry off some of the water on your rotors. - Give trucks and buses extra distance
Tyres from large vehicles can splash enough water to block your vision completely. Avoid passing one, but if you must, do it as quickly as safety allows. - Traction and stability control are helpful on rain-soaked roads
Traction control helps you maintain grip by putting the brakes on the tyres struggling for traction, while a stability control system monitors your steering input, intervening with the brakes and/or reducing engine power. - How to manage aquaplaning if it happens
Aquaplaning occurs when the water in front of your tyres accumulates faster than your car’s weight can push it away. The water pressure causes your car to rise up and slide on a thin layer of water between your tyres and the road. If you find yourself aquaplaning, don’t brake or turn suddenly as you may skid. Ease your foot off the accelerator and if you must brake, do it gently. If your car has anti-lock brakes (ABS), then brake normally. The car’s computer will automatically adjust the brakes. If your car doesn’t have anti-lock brakes then use light pumping actions. - Keep your tyres inflated properly
Don’t put off replacing worn tyres. Slow down when roads are wet and avoid puddles to prevent aquaplaning. If you have any doubts about the wet-weather performance of your car’s tyres, get a mechanic to assess them. - Make sure your wipers are in good nick and functioning correctly
If the blades are brittle or damaged, replace them before you’re caught in a deluge. Some wipers are better than others, so ask The NRMA for recommendations. Wipers need replacing? Here are six easy steps to replace your windscreen wipers. - In very heavy rain, stop
When visibility is so poor that the edges of the road or other vehicles can’t be seen at a safe distance, pull over and wait for the rain to ease off. If you can’t stop at a rest area and the roadside is your only option, pull off as far as possible and wait it out. Keep your headlights on and turn on your hazard warning lights to alert other drivers. Be very careful to pick a safe spot to pullover as everyone’s visibility is dramatically reduced.
