“It’s simple: don’t drive your car through floodwaters”

Even purpose-built offroaders can easily drown you in a flood, says the car review website dogandlemon.com.

Dogandlemon.com editor Clive Matthew-Wilson says: 

"My best advice is: don’t drive your vehicle through floodwaters, even if your vehicle is designed for offroad use. Aside from the fact that you may be quickly drowned, you can also wreck your car, even in relatively shallow water.”

Matthew-Wilson suggests that motorists avoid driving their vehicles through floodwaters deeper than 15-20cm (15cm in a small vehicle and 20cm in a taller vehicle such as an SUV).

“And don’t drive faster than 5km/h.”

“European cars are the most vulnerable to flood damage, but all modern vehicles are full of electronics that can be instantly wrecked if they get wet. Floodwater can also instantly wreck your vehicle’s engine, regardless of how your 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 motorists have been drowned that way.”

Matthew-Wilson says that electric cars are generally okay in the wet, but are at risk of major battery fires.

“The good news is that the weight of an electric car’s batteries helps to keep it from being washed away in floods. If the electric car has four-wheel drive, this will also help it stay stable in floodwater.”

“However, electric and hybrid car batteries carry a huge amount of energy. Electric cars are usually fine on wet roads, because they’re sealed against ordinary moisture. However, once floodwater (especially sea water) 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.”

“Don’t underestimate how much energy these batteries contain: an electric battery fire can be really dangerous.”

In 2018, floodwaters at the Italian Port of Savona leaked into a number of luxury Maserati hybrids that were being stored there for export. Hundreds of cars later caught fire due to salt-water contamination into the lithium-ion batteries. 

Matthew-Wilson advises that, during heavy floods, motorists should simply park their cars on high ground and wait for the floodwaters to clear.

“During heavy rains, the easiest way to avoid wrecking your car and possibly your life, is to simply avoid trying to drive through floodwaters. There are very few emergencies urgent enough to make the risk worth it.  Even if there’s a serious emergency, such as a badly injured child, the chances are high that you won’t make it through a heavy flood. So, take shelter, contact the emergency services and follow their instructions.”