Flood water: how to drive through it safely
Heavy rain showers combined with fallen leaves can create flash floods - and they can spell trouble for drivers. Find out how to drive through patches of localised flooding with our guide...
Heavy rainfall often goes hand in hand with hazardous flooded roads and travel alerts warning drivers not to travel unless their journey is absolutely essential.
The sensible option is to stay at home safe and dry. But what if you're already driving when a storm strikes and you find your route blocked by a submerged section of road? Or the carriageway is flooded not by rain but by a burst water main? When is it safe to proceed and when should you turn back?
In this story we'll tell you everything you need to know about driving through a flood, including which car models have the highest wading depths to cope in extreme conditions. Read on to learn how to deal with these potentially hazardous situations...
Driving through water top tips
1. Take an alternative route
Never drive through deep, fast-flowing water and don’t drive through flooded roads if you can avoid them. It’s better to add an extra 10 to 15 minutes to your journey rather than risk your car’s engine and electrics being ruined or, even worse, the vehicle being swept away.
2. Check the water depth
If you have a pair of wellies handy you could wade into the water to see how deep it is (keep a powerful torch in the glovebox for use after dark), or you could park up nearby and watch other vehicles go though it first. Unless you’re driving an off-road-ready 4x4 or SUV the maximum depth most experts advise you drive through in a car is 100mm. Modern cars are generally water-tight so they can start to float when driven through water that’s only 300mm deep.
3. Let oncoming vehicles pass
Wait for oncoming vehicles to get through the flood patch before you head into it, especially if they’re larger vehicles or are travelling fast. They could soak your vehicle and cause it to break down.
4. Drive along the highest point of the road
Most roads dip down at either side so aim to drive in the middle of the road. That’s another reason to wait for oncoming cars to get out of the way before attempting to cross floodwater.
5. Don’t drive too fast
Drive through flood water slowly – 3 to 4mph is an adequate speed. If you drive too fast you'll not only create a wave that will splash other road users, but you’ll also run the risk of your car’s tyres losing their contact with the road. If that happens, don’t brake, just take your foot off the accelerator and keep the steering wheel straight and wait for the grip to return.
6. Don’t stop
Although you should drive slowly, it’s important not to let the car come to a halt while crossing deep water because that could allow water to get into the exhaust pipe, which can cause costly damage. Keep the engine revs up, too. If necessary slip the clutch to do this in a car with a manual gearbox. If you’re driving a car with an automatic gearbox select the lowest possible held gear and keep your foot on the accelerator.
7. Dry your car’s brakes
Gently press your car’s brakes a few times once you’re clear of the flood – and in a safe place to do so – to dry them off and ensure they respond efficiently.
What to do if you break down in floodwater
If the worst happens, and your car gets stuck in deep water stay inside it and phone for help. Don’t get out or open the bonnet or you could worsen the initial damage. Don’t try to restart the engine either as that could push water into it.
The best vehicles for driving through water
The vast majority of cars and SUVs will run into trouble very quickly if you try to navigate anything other than a shallow ford or patch of flooding. Even the mighty BMW X7 has a maximum recommend wading depth of 500mm, and for most models it will be much less.
However, there are several 4x4 SUVs and pick-up trucks designed to cope with deeper stretches of water. The new king of waders is the OCTA version of the Land Rover Defender 110. With a 1,000mm – i.e. one metre – wading depth, it should be virtually unstoppable. That's a very expensive limited-edition model though, so here are five slightly more attainable vehicles with great fording abilities...
1. Land Rover Discovery – 900mm wading depth
This seven-seater not only lets you carry six passengers, it also comes with a Wade Mode, which when set closes vents, adjusts the throttle response and makes other changes to protect it from water. Its Land Rover stablemates are similarly impressive in this regard. The Range Rover has a 900mm wading depth too, as does a Defender on air suspension (850mm with coil suspension). A Range Rover Sport manages 850mm.
2. Ford Ranger/Ranger Raptor – 800mm/850mm wading depth
As well as performing well as a building site workhorse, the Ranger (along with the closely related VW Amarok) is a pretty handy off-roader. And if you go for the Ford Ranger Raptor performance version, you get loads more power plus a 5cm increase in wading depth to help you tackle the toughest conditions. Indeed, the Raptor came second in our best off-road vehicles test.
3. Isuzu D-Max – 800mm wading depth
Another pick-up truck that combines practicality with go-anywhere prowess is the D-Max. It's as tough as it looks, with plenty of suspension articulation and a lockable rear differential on top versions for the best traction. If you're really serious about going places most vehicles fear to tread, there's also the Isuzu D-Max Arctic Trucks AT35 – a pumped-up version with raised suspension, bigger, knobblier wheels and other kit.
4. Ineos Grenadier – 800mm wading depth
Okay, so with a starting price at the time of writing of a puddle's depth off £80,000, the Grenadier is not as obtainable as some cars on this list, but if you can afford one, you'll find the designers have you covered for flood situations. The engine air intake is high up to reduce the risk of water damage and a button near the rear-view mirror lets you quickly switch to a wading mode to help keep you moving and protect the vehicle.
5. Jeep Wrangler – 762mm wading depth
The Wrangler came top in our best off-roaders challenge and one of its strengths is what Jeep describes as its "water-fording capability". Indeed, you'll find plenty of companies offering snorkel kits you can fit to the engine air intake under the bonnet to protect it while wading. With lockable and waterproof storage compartments, and optional all-weather mats, this is not a car that's afraid of a few drops of rain.
Is it dangerous to drive an electric car through water?
The idea of driving a car with a big battery inside through water sounds terrifying, and while it shouldn't be any more perilous than doing so in any other model, it's vital to follow the advice above. However, there are some electric vehicles that boast impressive wading depths – namely the Maxus T90 EV electric pick-up truck (550mm) and the forthcoming electric Mercedes G-Class (850mm).
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