Kim Henson advises on staying safe and at the same time preventing wrecking your car in floodwater…
I first published this feature on Wheels-Alive in 2016, but in view of the huge amounts of rainfall we’ve seen lately (as I write, it’s late-November 2023), I feel that it is worth revisiting/updating now. It seems that many drivers don’t appreciate the potential dangers of driving through floods or deep puddles, and the fact that water ingress within a car’s air engine can wreck it. Modern car electronic systems and wiring connections can also be written off by floodwater, so it’s worth avoiding problems if possible; prevention is definitely better than cure.
It’s worth having a look at video tube channels online, searching for ‘cars in floods’ or similar, and the adverse effects of the water on some of the vehicles shown will be obvious (in some cases they will be write-offs…).
The recent very heavy and persistent rain has resulted in widespread flooding in many parts of the country. This can make driving very hazardous and certainly has the potential for wrecking your vehicle, if not risking life and limb. However, if you keep your head and don’t panic, you should be okay; just think carefully… and if at all possible avoid driving thorough water, especially if it’s of unknown depth.
The following tips may help you to stay safe, keep dry and preserve your vehicle.
1. TAKE EXTRA CARE when driving in heavy rain and in wet road conditions, as even if flooding is not prevalent, visibility will be impaired and the surfaces your tyres are travelling on are much more slippery than usual. In extreme conditions when the road surface is ‘coated’ with water, the tyres can ‘skim’ along the top of it. This is termed ‘aquaplaning’, and in such circumstances steering and braking the vehicle can be very difficult, if not impossible. SLOW DOWN and treat the car’s controls with kid gloves in such conditions.
2. IS YOUR JOURNEY REALLY NECESSARY? Ideally, if floods are forecast, or even if they seem likely, think carefully before venturing out on the road at all – especially late at night and/or in remote areas.
3. NEVER DRIVE THROUGH WATER OF UNCERTAIN DEPTH, especially when close to a known watercourse, and/or in places where the road fords a stream, even in dry conditions. Vehicles can easily sink in unexpectedly deep water, or be swept away by a fast-flowing swollen stream or river.
4. WATCH FOR FLOODED SECTIONS AT THE LEFT-SIDE OF THE ROAD. Large puddles and floods on the left-side of the road are commonly encountered after heavy rain, when the water cannot flow away fast enough, often due to blocked drains etc. Take special care when driving in such conditions, especially on unlit country roads, when a deep ‘puddle’ can catch you unawares, tugging at the steering and dragging the car towards the left. Be prepared and hold on tight to the wheel if you do hit a flood like this.
5. TAKE THE HIGH GROUND… If the road is flooded across its width, aim for the highest part of the tarmac, almost always in the centre, or ‘crown’ of the road. SLOW DOWN and wait for oncoming vehicles to pass before driving SLOWLY through the shallowest part of the water you can find. If in doubt about its depth, or if you cannot see a possible exit point at the far end of the flooded section, DO NOT ENTER the water; instead, turn round and retrace your route home.
6. DO NOT DRIVE FAST INTO OR THROUGH FLOODWATER… The ‘bow’ wave you set off can swamp pedestrians (especially frightening and dangerous for children and the elderly), cyclists or other motorists’ vehicles. In addition, the water could ‘drown’ your car’s electrics, or indeed could enter the engine via the air intake system or exhaust pipe(s), resulting in you coming to a halt in the middle of a flood.
7. KEEP THE ENGINE RUNNING FAST AND THE VEHICLE MOVING SLOWLY. If you MUST drive through a flood (ideally DON’T!), ensure that you have a clear run at it, and keep the car moving slowly with the engine running at medium to high revs (the pressure in the exhaust pipe will help prevent water from running through the exhaust system and into the engine; if you drop the revs the internal pressure in the pipework will drop too, with the risk that water may enter the engine and can cause ‘hydraulic lock up’ of the pistons/valves, resulting in severe damage to your motor). You may have to slip the clutch to a certain extent to achieve this; try not to overdo the slipping or the clutch will be damaged. If your car has a petrol engine and it stops because the spark plugs and high tension leads are wet, turn off the ignition, gently wipe them dry with a soft cloth, spray them with water-dispellant spray (keep an aerosol can handy in the car) and try it again; if water hasn’t entered the engine itself it should start again; fingers crossed!
8. TRY YOUR BRAKES! On emerging from the flood water, gently apply the brakes for a few hundred yards when you reach dry land, to expel water and dry out the pads/discs/linings and drums (the brakes will be at least partially ineffective when waterlogged).
9. INSURANCE ASPECTS. Your insurers may take a dim view if you have deliberately driven through floodwater and your car is damaged or even written off. Indeed it may be deemed that such an event is not covered by your insurance. Think carefully about this before heading into deep water – literally!
10. OPEN THE WINDOWS… If ever you should be unfortunate enough to find yourself in a vehicle that has been submerged in water, you need to get out of it and to the surface as soon as possible. However the water pressure acting externally on the vehicle’s doors may hold them shut so that they are very difficult, if not impossible, to open. If you can, open the car’s side windows, at least partially, to allow water to enter the vehicle so that the pressure on the inside and outside of the doors is equalised. It should then be possible to open the doors. Take a deep breath of air before making your exit.
Most of all, TAKE GREAT CARE when driving in heavy rain and/or on flooded roads, and make safety your main priority – for you, your family/friends on board, and other road users.
Additional note re. electric vehicles:
Although, on the face of it, electric cars may be able to negotiate flooded roads without coming to a halt, it should be borne in mind that by definition such vehicles are packed with electronic systems. These, and the wiring/connections, need to be kept dry. If they are swamped, they may operate for a while but later be affected by residual moisture/corrosion… A multitude of problems can arise as a result. Water and electricity really don’t mix!