Tips For Driving Through Flooded Roads

Over the past few days, there has been a spate of flash floods within the Klang Valley, leaving many car owners stranded on the road.

Here are a few tips on how to deal with flash floods.

1. Avoid Driving Through One!

The general rule of thumb is to avoid risking a drive through a flood in the first place. If possible, turn back or wait for the flood water to recede. Mobile apps like Waze are a good way to check the traffic conditions ahead, allowing other drivers to report on if or not a flood or anything else is causing any issue.

You should only attempt to drive across a flooded stretch only if you are absolutely sure of the depth of the water, and only if it is standing water. Just one foot of fast flowing water is enough to push a small car away. Attempting to drive across fast flowing water could result in having your vehicle washed away by the strong current, which could possibly result in a fatal accident.

2. Gauging The Depth

Do not attempt to drive over flood water that is higher than the bottom of your vehicle’s body. This is to avoid water splashes from being sucked in by your vehicle’s air intakes, as well damaging other parts of your vehicle. The exterior parts of your vehicle are made to withstand water. The insides are not.

Before deciding to drive across a flood, stop your vehicle and take note of the kerbs on either sides of the road. If you can still see them, then it is generally safe to drive across the road. If you can’t see it, exercise extra caution as the water level may be too high, plus there is always the danger of washed off or damaged sections of the road hidden by the water.

If you are absolutely certain that the path is safe enough to be crossed by your vehicle, aim your vehicle towards the ‘crown’ or the highest point of the road, as the water level will be the shallowest there. Depending on the way the road is constructed, this is generally either at the centre or the right side of the road. Of course, this only applies to right-hand drive countries like ours, where roads are designed to channel rainwater away from the centre to the gutters at the left. However note that there can be certain stretches, especially in hilly areas, where water may actually gather more on the right side than on the left.

3. Driving Across Standing Water

As mentioned earlier, never attempt to drive across fast flowing water. Never follow behind another vehicle when driving over a flooded stretch. This is to avoid your own vehicle from getting stranded if the vehicle in front stalls.

Once you are certain that the standing water ahead is still safe enough for your vehicle to drive across, aim for the shallowest point and gently ease your vehicle towards the water at speeds no faster than walking pace, about 3 km/h. Higher speeds may cause water splashes that may get sucked in by your engine’s air intakes.

Shift to a low gear, or ‘L’ or other similar function modes in your transmission.

Once your front wheels are over the water’s edge, gently accelerate to increase your speed slightly, at around 6 km/h. Accelerate just enough to create a bow wave in front of your vehicle. This bow wave will create a depression in the water level in front of your vehicle, allowing you to continue driving across the stretch safely. Try to keep a constant speed so this bow wave is not disrupted.

Never take your foot off the accelerator. Maintaining a constant pressure is important in keeping water out of your vehicle’s exhaust. Easing pressure off the accelerator pedal will result in a drop in exhaust pressure, which could then result in flood water being sucked in from the exhaust and into your engine.

After successfully crossing a flooded section, continue driving slowly while gently tapping on your brakes to dry them, as well to check their function.

The video below is made in the context of off-road driving, but the bow wave and low but constant speed principle still applies for urban flash floods.

4. Get Flood Insurance Coverage

Lastly, ensure that your car’s insurance protects your vehicle against flood damage. For a RM120,000, 1.8-litre C-segment family sedan, flood insurance adds about RM500 to the total motor insurance cost, but that’s only a very small price to pay when compared to the potential cost of repairing a flood-damaged car.

Remember that today’s cars are far more sophisticated, employing multiple electronic control units inside its safety, infotainment and convenience features. Repairing a flood damaged modern car can easily set you back tens of thousands of Ringgit.