Floods and heavy rain

Advice from the AA's flood rescue team

Even drivers with local knowledge can be caught out during heavy downpours

Even drivers with local knowledge can be caught out during heavy downpours

Driving in wet conditions can be hazardous and even drivers with local knowledge can be caught out during heavy downpours, as the most modern road surface is still susceptible to standing water.

Standing water creates a potential aquaplaning hazard as well as reducing visibility.

Take it easy through standing water and if the steering does become unresponsive due to the rain, ease off the accelerator and slow down gradually.

The AA has its own specially-trained and equipped flood rescue team called Special Operations Response Team (SORT).

Darron Burness

Darron Burness

Darron Burness, Head of Special Operations, says: "Only attempt to drive through flood water if you know it's not too deep and maintain a steady, slow speed to avoid creating a bow wave."

The air intake on many cars is low down at the front and just an egg cupful of water in the combustion chamber is enough to wreck an engine.

Water doesn't compress and the piston in effect hits a wall, bending or breaking a con rod. Driving fast - even if the intake's above the water level - could cause water to be ingested.

If you break down in heavy rain don't prop the bonnet open while you wait for the patrol to arrive. The engine will be more difficult to start again if the electrics are all rain-soaked.

In heavy rain

  • You must use headlights when visibility is seriously reduced - generally when you cannot see for more than 100 metres (328 feet)(Highway Code).
  • You may use front or rear fog lights but you MUST switch them off when visibility improves (Highway Code).
  • Improve vision in wet weather by renewing windscreen wipers if worn or damaged.
  • Stopping distances increase on wet roads. Double the distance you leave between you and the car in front.
  • If steering becomes unresponsive due to the rain, ease off the accelerator and slow down gradually.

Floods and standing water

Don't enter flood water that is moving or more than 10cm (4 inches) deep.

Allow oncoming traffic to pass first and drive slowly and steadily to avoid creating a bow wave. Test your brakes as soon as you can after leaving the water.

Don't try driving through fast-moving water, such as at a flooded bridge approach – your car could easily be swept away.

Slow down and try to avoid standing water if you can.

Driving fast through standing water is:

  • dangerous - tyres lose contact with the road and you lose steering control in what's known as 'aquaplaning'. If you do experience aquaplaning, hold the steering wheel lightly and lift off the throttle until the tyres regain grip.
  • inconsiderate - driving through water at speeds above a slow crawl throws water onto pavements, soaking pedestrians or cyclists. You could face a hefty fine and 3-9 points if the police believe you were driving without reasonable consideration for other road users.
  • expensive - the air intake on many cars is low down at the front of the engine bay and it only takes a small quantity of water sucked into the engine to cause serious damage. All engines are affected but turbo-charged and diesel engines are most vulnerable.

As you drive slowly through standing water, use a low gear so the engine rev's are higher; water in the exhaust could otherwise damage the catalytic convertor.

Fords

Don’t assume that a ford is always safe to cross just because the road goes into the river on one side and comes out on the other. The depth of the water at a ford, and its flow rate, will change with the weather.

Read AA advice on fording a river safely »

Floodwater facts

  • The majority of drowning deaths in the UK occur within only 3m of a safe point
  • 2/3 of those who die in flood-related accidents are considered to be good swimmers
  • 32% of flood-related deaths are by drowning in a vehicle
  • After 20 minutes in water at 12C the temperature of the deep muscle of your forearm would drop from 37 ºC to 27ºC,  leading to a 30% reduction in muscle strength.
  • In water 1m deep (waist high), flows of 1m/s become challenging and by 1.8m/s (4mph) everyone will be washed off their feet.
  • If the speed of the flood water doubles the force it exerts on you/your car is quadrupled
  • Just 15cm (6 inches) of fast flowing water can knock you off your feet and be enough for you to be unable to regain your footing.
  • 60cm (2 ft) of standing water will float your car
  • Just 30cm (1ft) of flowing water could be enough to move the average family car
  • Just an egg cupful of water in the combustion chamber could be enough to wreck an engine
  • Flood water can be contaminated and carry diseases
  • Culverts are dangerous when flooded – the siphon effect of culverts can drag in pets, children and even fully grown adults

Flood alert map


(15 December 2014)

 

Need AA Breakdown Cover?

We fix more cars by the roadside than anyone else. Get a quote »

Need AA Breakdown Cover?