Behind the Forecast: Dangers of flash and river flooding

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Behind the Forecast: Dangers of flooding (2/14)

LOUISVILLE, Ky. (WAVE) - More deaths occur each year due to flooding than from any other thunderstorm related hazard, according to the National Weather Service (NWS). The Centers for Disease Control and Prevention says that half of all flood-related drownings happen when people drive vehicles into floodwater. People walking near or into floodwater is the second-highest percentage of flood deaths.

Just six inches of rushing water can knock down an adult, and it takes only a foot of fast-moving water to carry away most cars. Two feet of water can wash away trucks and SUVs!

Several types of flooding can be dangerous; in Kentucky and Indiana, flash flooding and river flooding are the main focus.

Flash floods usually occur within six hours of the immediate cause. Heavy rain, ice or debris jams, and dam or levee failure can cause flash flooding. The most common cause of flash flooding is excessive rainfall from multiple thunderstorms tracking over an area or slow-moving storms. Flash flooding is an issue in cities because asphalt and concrete don't allow water to seep into the soil. Water can also quickly runoff hilly or mountainous areas since water travels faster downhill.

River flooding happens when rivers overflow their banks and flood areas that are typically dry. Snowmelt, ice jams, heavy rain, and dam failures can all cause river flooding. Depending on flooding severity and impacts, the NWS categorizes river flooding as minor, moderate, or major.

Many newly built Ford Explorers parked at the Louisville Assembly Plant on Fern Valley Road fell victim to the floodwaters in 1997.
Many newly built Ford Explorers parked at the Louisville Assembly Plant on Fern Valley Road fell victim to the floodwaters in 1997. (Source: WAVE 3 News Archives)

Preliminary information for 2019 shows that 66% of the people who died in the United States from flooding were in their vehicles. Seven died in Kentucky while one died in Indiana.

Here are what the various Flood Watches, Warnings, and Advisories mean per the NWS.

  • Flash Flood Warning: Take Action! A Flash Flood Warning is issued when a flash flood is imminent or already occurring. If you are in a flood-prone area, move immediately to high ground. It is possible to experience a flash flood in areas not immediately receiving rain.
  • Flood Warning: Take Action! A Flood Warning is issued when flooding is imminent or occurring.
  • Flood Watch: Be Prepared! A Flood Watch is issued when conditions are favorable for flooding to occur. It does not mean flooding will occur, but it is possible.
  • Flood Advisory: Be Aware! A Flood Advisory is issued when a specific weather event that is forecast to occur may become a problem; the situation is usually not bad enough for a warning. However, flooding may cause significant inconvenience, and if caution is not exercised, it could lead to situations that may threaten life and/or property.
The floodwaters covered the driving lanes of Interstate 65 in Okolona in 1997.
The floodwaters covered the driving lanes of Interstate 65 in Okolona in 1997. (Source: WAVE 3 News Archives)
  1. Flood Crest at 52.15 ft (Upper Gauge) on 01/27/1937
  2. Flood Crest at 42.10 ft (Upper Gauge) on 03/08/1945
  3. Flood Crest at 41.70 ft (Upper Gauge) on 02/16/1884
  4. Flood Crest at 41.20 ft (Upper Gauge) on 03/12/1964
  5. Flood Crest at 39.50 ft (Upper Gauge) on 02/16/1883
  6. Flood Crest at 39.40 ft (Upper Gauge) on 04/02/1913
  7. Flood Crest at 38.76 ft (Upper Gauge) on 03/07/1997
  8. Flood Crest at 36.40 ft (Upper Gauge) on 01/22/1907
  9. Flood Crest at 36.00 ft (Upper Gauge) on 04/19/1948
  10. Flood Crest at 34.10 ft (Upper Gauge) on 03/23/1933

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