Driving in extreme rain and flooded conditions

Whether to go ahead or not.

With the recent extreme weather we had in the Dubai and the UAE (2 years worth of rain in one day!) a lot people were exposed to driving in flooded conditions for the first time, and were unsure what to do or how to go about it, and as a result we have thousands of cars and trucks that were stranded by the side of the road with various degrees of damage, some salvageable, some beyond the point of salvage (i.e. the most “money smart” thing to do with them is to scrap them rather than try to fix them, they are not economic to fix any more).

Here I thought I would put down some advice from what I have read over the years and what I have practiced myself, since I have been driving for over 25 years in different countries and conditions. I have mostly driven 4x4s/sport utility vehicles/off-roaders, though I have had my fair share of time in smaller cars as well as motorbikes.

I have put together a Q & A based on what a typical motorist might wonder, when faced with a flooded road and wondering whether to go ahead or not. What goes through your mind in such a situation?

What is the wading depth of my car?

“Wading depth” is a term that means, how far can you go in water, without doing major damage to your car. Some 4x4’s specify this depth in the owner’s manual, because it is an essential piece of information for off-roading, to know when you can proceed in some conditions, and when it is best to turn back. For example, the famed Mercedes G-wagen (or G-class www.mbusa.com) has a fording depth of 50 or 60cm, depending on year of manufacture and model, and this can be easily increased by addition of a snorkel and a suspension lift. A general rule of thumb I have heard used, is if the water comes up to half the car tires (i.e. half the car tires are submerged under water, you can only see the top half), it is best to turn around and NOT proceed. This is assuming the water is standing and not moving. Moving water is WAY more dangerous, even if it is only 1 foot (25cm) deep. Fast moving water can sweep a car and pedestrians off the ground regardless of how much they resist, so avoid fast moving water at any rate!

What can happen if I drive into a pool of (still – not moving) standing water?

It is normal to do a cost-benefit analysis in your head when it comes to “what is the worst that could happen if I keep driving in this water”? To answer this question, the engine and transmission (gearbox) are two of the most expensive components in a car, and if water enters the engine from where it should not (i.e. air intake/filter), then this can result in a condition known as “hydro lock”, where the water entering in place of air causes the engine to stop suddenly, and this sudden stop can result in bent valves, cracked pistons, broken blocks and so on. In the best case scenario, if water goes in and the engine dies from the lack of air before water actually goes into the sensitive places, the cost of repair may be minor, but if water goes into the combustion chamber of a hot engine, you might be looking at a replacement engine ($$$$$)!

There is much more that can be said on the topic, like that one time a family member’s car was driven through water and I took it back in to dry it out and get it back into service, maybe it is a blog post for another day. I hope this helps you in some way!