How to drive through flood water

Driving in heavy rain can be challenging, but flooded roads are even more treacherous. Be prepared with our guide to driving in the wet

James Mills
Oct 9, 2019

Wet weather driving can be demanding and it's not something to undertake lightly if the rain is falling faster than it can drain. Flooded roads are commonplace during the wetter months of the year, and most of us will know of at least one spot locally that is prone to becoming submerged when the rain falls.

And with many cars - even SUVs - not being able to wade through much water before engine damage can occur, it's worth being prepared before taking the plunge. Keep reading to find out how to safely negotiate flooding on the roads to keep moving and ensure that you and your car remain safe.

If rain is lashing down, it's wise to ask yourself whether you really need to travel at all before even leaving the house. If not, it can be a good move to stay at home and wait until the rain has eased off and should make for a less stressful drive, too. If it is essential though, we've put together this handy guide to driving in flooding that might just help to keep you afloat.

These 10 tips will not only help to keep you and your passengers safe, they will also help you to avoid what can often be irreparable damage your car, so read on to learn more about how to drive through flooding.

10 tips for driving in flooding

1. Dont' forget your headlights

This is surprisingly easy to forget, especially if you're driving during the day. However, while you might not think to put your headlights on, it's important to be seen and to give yourself the best possible view of the road ahead.

The Highway Code says drivers must switch on their vehicle’s headlights when visibility is reduced, including in heavy rain. While it might not help you to see necesarily, it'll make you more visible to other road users. Even if that simply stops another vehicle zooming through a flood, causing a big wave to wash over your bonnet and destroying your engine, you'll be grateful for being seen.

2. Adjust your speed

You may be driving in a new off-roader or sports car fitted with a brand-new set of tyres, but you should always allow for conditions, which means slowing down in heavy rain. If that means dropping below the speed limit of the road, so be it. Fail to do this and you could experience aquaplaning, which could potentially lead to a crash.

Those who have ever experienced aquaplaning – where the tyres skate over the surface of standing water, creating an effect similar to driving on ice – will know that this can happen at even low speeds and leaves you with very little ability to steer or brake.

 

Reducing your vehicle’s speed reduces the likelihood of aquaplaning and means you allow for delayed reaction times in poor-visibility situations and the increased stopping distances that come with wet and flooded roads.

The same goes for following another car, you should allow double the distance between you and the car in front when driving in very wet weather to accommodate for the worse visibility and greater stopping distances.

3. Avoid severely flooded roads

It makes sense to avoid flooded stretches of road by taking detours where practical. Doing this means there’s no chance of you getting stuck or damaging your car; in certain conditions getting stuck in a flood could be potentially dangerous as you or your vehicle could be carried away in fast-moving water.

This also avoids the risk of damaging the underside of your car on unseen obstacles or, worse still, causing irreparable damage to the engine that could lead to your insurer declaring the car a write-off.

Remember, too, that if you were to write off your car this is likely to mean losing any no claims bonus you have on your insurance and/or still owing a substantial amount on your car finance, even if the insurance company pays out the market value of your car. Read our guide to Gap insurance to understand the risks.

4. Gauge how deep the water is

If you have no option but to pass through flood water, don’t enter it without knowing how deep it is. This calls for some improvisation on your part. Find a stick or use an umbrella to assess the depth of the water.

Be mindful that the water is likely to be full of silt and you won’t be able to see where you’re driving, so use the stick to feel ahead, then take a measurement at the deepest part of the water. You can also use the stick to establish whether there are any high kerbs or hidden underwater obstacles ahead.

Next, compare the watermark on your stick, umbrella or even your leg to the ground clearance of your vehicle. If the water is as high as the lowest part of the car’s bodywork or higher, think twice about attempting to pass through it. The air intake for the engine could be flooded, which in turn could cause the engine to be destroyed.

5. Beware of strong currents

The current of flood water running across a road can be surprisingly strong even if the water is only a couple of inches deep. That’s because there is so little friction slowing the water, due to the road’s smooth surface.

Be extremely wary of entering fast-flowing water, as anything above 15cm (nearly six inches) could sweep you off your feet or drag your car into danger and it could be impossible to either get back onto your fleet or regain control of the car.

6. Can anyone guide you?

If you have a passenger, or other drivers are about, it is a good idea to ask someone to guide you when crossing flood water. That’s because you won’t be able to see how high the water is and how it’s gathering around your car.

Having someone guide you means you don’t have to try to lean out of the window or leave your door ajar to see how high the water is in relation to your car, which could take your attention away from other hazards.

7. Go slow

Speed is your worst enemy in deep water. The likes of the AA, RAC and Land Rover advise entering flood water at speeds of only 1 or 2mph. You may need to slip the clutch slightly to do this, or dab the brakes in a car with an automatic gearbox to avoid going too fast.

This might sound extreme but prevents a wave of water going over the bonnet and potentially causing irreparable damage to the engine. It can help to rev the engine a little as you slip the clutch, to keep the car moving slowly but also stop water flowing up the exhaust’s tailpipe.

8. Look out for approaching vehicles

You might be extra careful as you drive through flood water but what about other drivers? If there is an over-enthusiastic driver zooming towards you from the other direction, you need to take action to avoid them causing damage to your car.

Beware of a wave from their car, as it could swamp your car, causing water to entirely submerge the bonnet and engine. If you can see another car is passing through flood water you're approaching, therefore, it's wise to wait until they're through before starting yourself, so you're not in the water as they pass, which means that even if they create a humongous wave, you're safe.

9. Dry your brakes

As soon as you have passed through deep water, apply the brakes lightly to dry them off and ensure that no small stones have become lodged between the brake discs and pads.

This should mean that the next time you need to brake sharply, you'll get a better response, as the brakes shouldn't have such a layer of water on them, reducing their effectiveness.

10. Protect your engine

If the engine cuts out when crossing water, don’t try to restart it. It is likely to have swallowed water, and further damage could be caused by trying to start the engine again. If the car's still moving, try to move it as far out of the way as you can and switch on the hazard warning lights, so it can be seen.

If you urgently need to get clear of the vehicle, grab your phone and coat and get out. Don’t worry about water entering the car; this could help stabilise it. Once clear of the water, call a breakdown provider.

 

Read more about:

Latest advice

  1. What is the London T-Charge?

  2. Should I buy a pick-up?

  3. Car finance for part-time workers

What our customers say