Driving in Bad Weather
Driving through Deep Water

Driving Through Deep Water: Dangers, Wet Brakes & Flood Safety Rules

Updated Nov. 16, 2020

When it comes to driving through deep water, there is only one rule you need to remember: avoid it at all costs. Finding an alternative route or waiting for the water to subside is the only safe course of action, should you encounter standing or deep water on the road. Do not attempt to drive through, as it is impossible to accurately determine the water’s depth or the force of the current from where you sit in your vehicle. The water may appear to be just a few inches deep and moving slowly, but is that a chance you are willing to take?

How deep is dangerous?

Even relatively shallow water can be dangerous. At low speeds, six inches of water can cause you to lose control of the vehicle and can float some smaller vehicles. Many vehicles will float in more than one foot (12 inches) of water and once the depth reaches two feet, very few vehicles will be able to keep their wheels on the road - sports utility vehicles (SUVs) included.

When a vehicle floats off a flooded roadway into deeper water, it can easily roll and fill with water before the driver and passengers have the chance to escape.

Wet brakes

Wet brakes can be a problem when you have driven through extremely heavy rain or deep water. If enough water to act as a lubricant has reached your brakes, you may find they pull in one direction or are completely ineffective. Do not panic if this happens, simply pulse the brakes gently while in a low gear to shake off the excess water. When your brakes are dry, they will work just fine.

As a preventative measure it is often wise to apply this brake-drying technique immediately after driving through a pool of water on the roadway, even if you do not need to brake at that time. This will ensure your brakes are ready and working correctly when you need them next.

Flash floods

Flash floods are a common and deadly hazard in the United States, causing around 200 fatalities every year. Approximately 50 percent of flood-related drownings are known to occur in or around vehicles. People mistakenly assume that being inside their vehicle will protect them during a flood. Unfortunately, the opposite is usually true.

Flash floods occur when a great deal of rain has fallen in a short amount of time. The rate at which a flash flood can develop is what makes them such a dangerous phenomenon. In some cases, small streams of just a few feet wide and less than 12 inches deep have swollen to over 12ft deep and 80ft wide, in a matter of minutes. These are the facts all drivers must know about flash-flooding:

  • Six inches of water will reach the bottom of most passenger cars, causing loss of control and stalling. Six inches of swiftly moving water can also knock a person off their feet.
  • 12 inches of water will float many cars.
  • Two feet of swiftly moving water will sweep away larger vehicles such as pick-up trucks and SUVs.
  • Flood water on a roadway may be obscuring a hazard, like a missing chunk of roadbed or a broken bridge. Keep in mind that roads quickly weaken under floodwater. Even after the water has subsided you must proceed with extreme caution, as the weight of your vehicle could make the road collapse.

Dealing with floods

If you observe water quickly rising on the roadway, or the National Weather Service has issued a Flash Flood Warning, you should act right away.

  1. 1

    Do not drive through the flooded patch of the roadway, even if you can see clear road on the other side.

  2. 2

    Get away from areas that are more susceptible to flooding, such as dips, canyons, dry river beds and other low spots. Look for higher, safer ground.

  3. 3

    Avoid areas near streams and river beds that are already flooded. Even if the flooding does not appear to be severe, flooded roadways may be damaged and no longer safe to drive on.

  4. 4

    If your vehicle stalls while in water, leave it immediately and look for higher ground. If the water continues to rise it may be difficult or impossible to open your door and escape the vehicle.

  5. 5

    Use extra caution when driving at night, as it will be harder to see flood hazards.

  6. 6

    Never park your vehicle or camp next to streams or dry stream beds during threatening conditions.

Escaping a vehicle submerged in deep water

If your vehicle is swept into deep water by a strong current, knowing what to do will save your life and the lives of your passengers. Acting quickly is the key to survival in such situations, as most vehicles will only float on the surface of deep water for 30 to 60 seconds. First things first, get out of the vehicle. Do not call 911 until you are out of the car! Use the following steps to escape from a sinking vehicle:

  1. Unbuckle your seat belt.
  2. Roll down a window before the car sinks.
  3. Open the door if possible but be aware that the car will immediately fill with water if you do this. Do not panic.
  4. If you cannot open the door or window, try to kick out a side window.

There are specially designed “escape tools” on the market which can be kept in your glove compartment or door pocket, to break a window if you become stuck in a sinking vehicle.

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