Floodwater's Underrated Power

You vs. Flowing Water

From 2004-2013, flooding claimed an average of 75 lives per year in the U.S., according to National Weather Service statistics. Flooding makes up 40 percent of all natural disasters, the most common global natural disaster, according to the Centers for Disease Control.

Let's lay out some impressive facts about floodwater.

Six inches of flowing water can knock a person off their feet.

• Water flowing at 7 mph has the equivalent force per unit area as air blowing at EF5 tornado wind speeds.
• Water moving at 25 mph has the pressure equivalent of wind blowing at 790 mph, faster than the speed of sound.

Six inches of flowing water can drown a person.

• If you slip and fall face first, you might drown before you come to.
• Babies/small children are very vulnerable; just as they would be in a bathtub accident.
• Water levels in flash floods can rise one foot in five minutes. In some cases, for instance in a canyon, near-instantaneous rises of 10-30 feet or more may accompany walls of water rushing downstream.

Next, the danger of driving into flood water.

Flooding and Vehicles

You see water covering the road ahead. Perhaps the vehicle ahead of you just successfully navigated through the floodwater. Should you follow suit?

Consider the following facts from FEMA and the National Weather Service:

• Nearly half of all flash flood-related deaths involve cars and trucks.
• Six inches of water will reach the bottom of most passenger cars, causing loss of control and potential stalling.
• A foot of water will float many vehicles. According to the U.S. Geological Survey, water one foot deep typically exerts 500 pounds of lateral force, which could easily tip a vehicle on its side or flip it over.  
• Two feet of rushing water will carry away most vehicles, including SUVs and pickups. The vertical buoyancy force of about 1,500 pounds per foot of water lifts the vehicle, while a lateral force of 1,000 pounds (or more if water is flowing faster) pushes it downstream.

Once your vehicle becomes buoyant, it can be swept away, tipped on its side or flipped over, giving you only seconds to escape. 

Never drive into floodwaters of unknown depth and never drive around barriers warning you of a flooded road ahead.

You may not know if the road has been washed out and may underestimate the speed of the floodwater. As the National Weather Service advises, "Turn around, don't drown!"

Next, the power of floodwaters and your home.

Flood Water vs. Homes

As we mentioned earlier, flowing water can exert an incredible force on anything in its way, including your home.

Water flowing at just 4 mph produces a force comparable to an EF2 tornado's winds, sufficient to move boulders five feet in diameter.

Most flash floods can generate at least 1.34 horsepower per square meter of water, exerting 18.7 horsepower on a 30-foot wide section of a home.

In the extreme, the energy of a flash flood can be 100 times stronger, generating 1870 horsepower on that same section of a home, roughly two to three times the power generated by today's luxury sports cars.  

Floodwaters are thought to have reached peak forward speeds of 67 mph. The fastest floodwaters are on steep terrain, in relatively smooth rock ravines or concrete channels.

With this all in mind, if you live, camp or hike near a river, creek, or stream, particularly in hilly or mountainous terrain, you should consider evacuating to higher ground upon the issuance of a flash flood warning.  

In general, awareness of the weather situation can save your life in a flash flood.

(MORE:  WeatherREADY flood tips)

Download The Weather Channel's app for your smartphone and tablet or use NOAA Weather Radio to make sure you have a method of receiving flood watches and warnings.

(INTERACTIVE: Current NWS Flood Watches and Warnings)

Act quickly once receiving a warning. Knowing how to quickly get to higher ground if you're in a flood-prone area could save your life.

PHOTOS:  Colorado September 2013 Flood Aerial Photos