Severe Weather Awareness Week – Flooding

Weather Knowledge

LITTLE ROCK, Ark. – March 1-7, 2020 has been declared Severe Weather Awareness Week by the National Weather Service (NWS) and Arkansas Department of Emergency Management (ADEM). Today’s topic of discussion is flooding. Below you will find more information about the two most common floods that occur in Arkansas – flash flooding and river flooding.

Flash Flooding:

A flash flood is a flood that occurs suddenly, creating a channel of raging water that runs through neighborhoods, valleys, streets, etc. The rate at which the rain falls is quicker than the rate of runoff, especially in locations in which the ground is already saturated. This leads to the collection of rainfall on roadways, streams and creeks.

While flash flooding occurs most commonly due to prolonged heavy rainfall from storms that move slowly or develop over the same area, it can also occur with dam and levee failures.

Urban locations are more prone to flash flooding as concrete and asphalt highly limits the absorption of water into the ground. Hilly terrain will see more flash flooding also as the rainwater will runoff downhill and gather at in the valleys.

According to the data collected over the last 30 years in the United States by the NWS, flooding kills more people each year than other major weather events including tornadoes, hurricanes and lightning. Their data shows that on average, 80-90 people die per year from flash flooding scenarios across the United States.

Half of the recorded deaths from flash flooding come from scenarios in which people try to drive through flooded areas. These floods are extremely dangerous due to the fast moving and unpredictable flow of water. A flash flood can be so powerful that it takes away whatever is in its path including debris. Plus, a continued flow of water can wash away pavement.

It doesn’t take much water to make a big impact, either.

  • 6 inches of fast moving water can knock over and carry an adult.
  • 12 inches of fast moving water can carry a small car.
  • 18-24 inches of fast moving water can move most SUV’s, vans and trucks.

One phrase you’ll hear used frequently by meteorologists when heavy rainfall is expected, especially when flash flooding is possible is “turn around, don’t drown.” This simple phrase acts as a reminder to motorists to help save lives. When or if a driver comes to a flooded roadway, he or she is encouraged to turn away from it rather than try to cross. Should the motorist attempt to cross it and be unsuccessful in doing so, it could result in loss of life from drowning.

Data from the ADEM and NWS shows that in 2019, a total of four people died from flooding – either driving into floodwater or becoming submerged in a swollen creek.

The most severe flash flooding event, however, that occurred in Arkansas resulting in the highest total of deaths actually dates back ten years. On June 11, 2010, the Little Missouri River rose over 20 feet following a rainfall event that resulted in more than 6 inches of rain. Prior to dawn, campers in Montgomery County at the Albert Pike Recreation Area were awakened to high rising and raging water. Unfortunately, 20 people drowned.

What do you do when flash flooding is possible or already occurring? Follow these guidelines:

  • Move to higher ground quickly
  • Don’t try to pass roadways with standing or flowing water
  • Stay away from flood prone areas like near streams, creeks, culverts, rivers, drainage ditches
  • Stay out of floodwaters
  • Be especially cautious at night when it’s harder to see

Flash Flooding Terminology:

A Flash Flood Watch means that conditions are favorable for flash flooding. When the National Weather Service issues a watch, it usually covers a big area including several counties. During this time, it is best to review safety plans and know what to do should a warning be issued or flash flooding start to occur.

A Flash Flood Warning means that flash flooding is either already happening or will occur soon. Warnings of this type typically cover a smaller area. When a warning is issued, action should be taken immediately, following the guidelines above.

A Flash Flood Emergency is reserved for rare situations in which there is a severe threat to human life and catastrophic damage from flash flooding. Emergency officials may report life threatening water rises and/or rescues, evacuations occurring within the area of a flash flood.

River Flooding:

River flooding is a more long-term event that lasts for days, weeks, possibly even a month or longer. Water from flash flooding eventually makes its way into rivers, which overall will lead to higher river water levels and could result in the flooding of a river. It is usually a slower process than flash flooding, giving individuals who may be impacted more time to prepare for its effects,

Rivers can cause devastating results when water overtakes homes, business and hundreds/thousands of acres of cropland – all of which we saw during the summer of 2019 when the Arkansas River created historic flooding.

The safety guidelines for river flooding safety are essentially the same as flash flooding. People whose homes and/or businesses may be threatened by rising river levels may choose to place sandbags around the building to help keep floodwater from entering the premises. Locations that will likely receive substantial damage from floodwater are most likely to be ordered to evacuate – heed the warning and leave, finding safety elsewhere. Remember, things can be replaced but your life cannot.

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