How to keep yourself and your car alive when driving through floodwaters

Tuesday, 10 January 2023

Heavy rain is causing flooding and road closures in the Coromandel Peninsula and the area remains under an orange heavy rain warning until 12 pm Wednesday.

The best mode of transportation through flooded waters is a boat. But if you absolutely have to drive experts say go as slow as possible.

Bill Prescott, of Prescott’s Garages Ltd near Hikuai, says every time there is a flood on the Coromandel Peninsula someone gets marooned, and the usual mistake is driving too fast.

On Monday night, a family of three including a six-year-old boy, was rescued from a car that became stuck in a swollen and dangerous river near Ruatoria ahead of Cyclone Hale.

* Wild weather eases in the Coromandel after 1-in-15-year deluge

* Wild weather causes ocean diesel leak, floods, slips on Coromandel Peninsula

A summer storm on the Coromandel Peninsula left a bridge at the Hikuai Pauanui intersection underwater.

Heavy rain is causing flooding and road closures in the Coromandel Peninsula and the area remains under an orange heavy rain warning until 12 pm Wednesday.

MetService warns 'heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous'.

The Hikuai Settlement Rd between Prescott’s Garage and the Waterways roundabout was already flooding on Tuesday, with six to eight inches of water on the road.

Prescott said the smart things to do to avoid major damage to the car and occupants are “watch the road, drive on the high side and go slow – like 1-2 km/hr”.

However, if a motor vehicle comes towards you - creating a bow wave, the best thing you can do is turn off your car and stay there till the wave has passed.

He warned the water from the wave could go into a car’s air box or air intake and ruin the engine.

“It is what causes a lot of damage, especially with European cars, where the air intake is down by the front wheel or right across from the front of the grill. It only takes a tablespoon of water going into the motor to damage it.

“If the water speeds into the front bumper and the mudguards, it will tear all that up, because it is only held in with plastic screws.

“It rips it all off and could do thousands of damage to the car, especially with Audis and BMWs, as they have a big plastic skirt under them.

“It just creates havoc.”

Last month when flooding closed roads in Coromandel Prescott said two cars – a Mitsubishi Outlander and a V6 Nissan – got badly damaged because of driving through floodwater “too fast”.

“It sucked water into the engine and totally damaged the motor.

“And the price to repair that damage is at least $12000.”

There were likely risks of crashes too, on top of damage to the motor, Prescott said.

“If your car is getting washed or pushed side ways, you shouldn’t be in that deep water.

“I have seen a Holden station wagon get washed off the road, over the top of the fence and onto a paddock. That was probably 2 feet (61cm) of water on the road. The guy had to scramble out the door and up on to the roof.

“People like to see the big splash of water go up on the bonnet and go everywhere. Looks neat… you see it on TV.”

Motoring expert Clive Matthew-Wilson says while no car was safe to drive in heavy floodwaters, electric cars were somewhat less safe due to the fire risk.

Aside from the risk of your car getting washed away, Matthew-Wilson said floodwater could instantly wreck electronics and the engine, regardless of how the car is powered.

“And even if the floodwaters don’t wreck your electronics and engine, there’s a significant chance that you and your family could get washed away and drown. Yes, it really is that serious.”

“Don’t think it’s okay to risk floodwaters because they don’t seem too deep. Even if the water isn’t much more than 15-20cm deep, you can easily drive into hidden potholes or dips in the road. At about 30cm, many vehicles will start floating, which can be really dangerous.

“Floodwater often has the power of a tornado: it can pick your car up like a toy and fling you into a raging torrent. Lots of Kiwis have been drowned that way.”

Matthew-Wilson warned that electric cars carried extra risk.

“Electric and hybrid car batteries carry a huge amount of energy.

“They are usually fine on wet roads, because they’re sealed against ordinary moisture. However, once floodwater (especially seawater) gets into an electric or hybrid car battery system, there’s a high chance of a serious fire. So, you’re probably not going to be electrocuted, but the car may catch fire.

“There were multiple serious fires in Tesla cars following the recent floods in Florida. Fresh water is bad enough for vehicle electronics, but salt water is diabolical.

“Even if the battery doesn’t fail immediately, the salt may cause internal corrosion that may trigger a sudden battery fire, days, weeks or months later.”

With heavy rain falling in many parts of the country, the AA encourages motorists to take care when travelling.

AA Chief Mobility Officer Jonathan Sergel listed a number of things to consider, if you are driving through standing water:

- Go slowly so you don’t overtake the bow wave at the front of the vehicle.

- Keep a good distance between you and any vehicles in front and let them clear the water first before you start to go through.

- If a vehicle is coming in the other direction, let it past first so that your two bow waves don’t meet.

- Once you’re through the water, apply your brakes lightly to check they’re working and remove any water.

- If your tyres lose grip and you find yourself aquaplaning, ease off the accelerator and keep a firm grip on the steering wheel to avoid any sudden movements. Hitting the brakes hard or sharp steering movements could cause you to skid.