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How to Ford Deep Water

SAS survival expert, John 'Lofty' Wiseman

Floods can occur when rivers burst their banks after a thaw or period of heavy rainfall. In urban areas sewers and drains can become blocked meaning there is nowhere for the water to soak away.

If you've checked the weather forecast before departing then you will be aware of the weather en route to your destination and have considered if a detour is necessary to avoid any potential danger spots like fords and low lying areas.

In unfamiliar areas always pay attention to flood signs and warnings - even if there have been times previously when you've seen flood signs and there has been no apparent danger - it may have drained away.

However, even with good planning it is likely that you will encounter a flooded road at some point, so remember in normal vehicles you shouldn't attempt to drive through water that is more than about 25 centimetres deep (roughly up to the centre of your wheels).

To decide whether to cross a flood assess the depth of the water:

  • Observe how any other cars attempting to cross the flood are doing and use them to judge how deep it is.
  • Use the surrounding landscape to try and judge how deep the water is by looking at water levels relative to curbs, traffic signs, trees etc.
  • If all else fails wade out to measure how deep the water is using a pole.
  • Beware of fast flowing water that can make you lose your footing.
  • Be aware that water can hide potholes and submerge obstacles in the road. Worse still, there may be no road at all if the flooding has washed away the road surface.
  • If you're unsure, make a detour, it's likely to be quicker and safer.

If you decide it is safe to cross:

  • Let some of the air out of your tyres to reduce the car's buoyancy.
  • Pass through the flood one vehicle at a time and don't drive through water against approaching vehicles.
  • Drive in the middle of the road where the water is likely to be most shallow.
  • As you enter the water (slowly) you will create a 'bow wave'.
  • Using first or second gear, drive slowly and keep your speed constant - keeping the bow wave in front of your car (if you speed up or slow down this could cause water to wash back into the engine).
  • Don't change gear because this can cause water to be sucked back up the exhaust.
  • If your wheels start to lose grip partway through a flood, the car may be trying to float. Counter this by opening a door to allow some water into the car, this will weigh it down, enabling the tyres to grip again.
  • After driving through a flood apply your brakes to dry them out and test they are operational.

Survival Tip

Normal vehicles shouldn't attempt to drive through water that is more than about 25 centimetres deep (roughly up to the centre of your wheel). (Lofty)


Winter Survival Guide

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Amid falling temperatures and rising levels of concern among drivers, Halfords Autocentres has worked with renowned survival expert, former SAS Sergeant Major and author of the best-selling SAS Survival Handbook John 'Lofty' Wiseman to create the ultimate Motoring Survival Guide.

Download the complete guide or read on for more winter survival advice.