Severe Weather 101: Floods

Flooding is the overflow of water onto land that is normally dry. Floods can happen during heavy rains, when ocean waves come on shore, when snow melts too fast, or when dams or levees break. Flooding may happen with only a few inches of water, or it may cover a house to the rooftop. They can occur quickly or over a long period and may last days, weeks, or longer. Floods are the most common and widespread of all weather-related natural disasters. Flooding occurs in every U.S. state and territory, and is a threat experienced anywhere in the world that receives rain.

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Flash floods are the most dangerous kind of floods, because they combine the destructive power of a flood with incredible speed and unpredictability. Flash floods occur when excessive water fills normally dry creeks or river beds along with currently flowing creeks and rivers, causing rapid rises of water in a short amount of time. They can happen with little or no warning.

In 1993, many levees failed along the Mississippi River, resulting in devastating flash floods. The city of New Orleans experienced massive devastating flooding days after Hurricane Katrina came onshore in 2005 due to the failure of levees designed to protect the city.  Dam failures can send a sudden destructive wall of water downstream. In 1889 a dam break upstream from Johnstown, Pennsylvania, released a 30-40 foot wall of water that killed 2200 people within minutes.

Here in the U.S., floods kill more people each year than tornadoes, hurricanes or lightning.  These tragic incidences happen too often and ironically, the people who are rescued from the vehicles reported the reason they drove into the water was to get to the safety of their home. 

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Where does the idea that a heavy vehicle will keep you safe come from?   Many automobile commercials advertise the ability to drive through water.  This may lead to the false sense of security at best and tragic consequences at worst. 

Many believe that a 3000 lb vehicle will remain in contact with the ground and won’t float.  But if you really think about that, a 97,000 ton aircraft carrier floats, why wouldn’t your car?  

Vehicles can be swept away in as little as 2 feet of moving water.  Trucks and SUV’s don’t fare much better with only an extra 6 to 12 inches of clearance.  In moving water, all that needs to happen if for the vehicle to become buoyant enough for the force of the water to push it sideways.  Once swept downstream, vehicles frequently flip over, leaving the driver only a few seconds to escape. 

The solution is simple.   Turn around, Don’t drown.   Stay out of flooded roadways.  Not only may the water be much deeper than it appears due to washed out roads, but as little as 6 inches of rapidly moving water is enough to sweep a person off their feet.  You must be especially cautious at night, as flooded conditions can be hard to see. 

The best thing to do is know when you’re at risk.   Consider carefully when you camp or park alongside a river, especially during threatening conditions.  Keep alert for the latest watches and warnings and pay attention to local weather conditions.  Also plan a safe route.   Find a hill near the river that you can go to should flash flood conditions occur.  

Robert Millette