Severe Weather Awareness Week Day 5: Flood Safety

Yahoo

28-03-2025

SIOUX CITY, Iowa (KCAU) — It's the final day of Severe Weather Awareness Week and today's topic is something still fresh on the minds of many in Siouxland: Flooding & Flood Safety.
On average, there are more flood-related fatalities than any other weather phenomena, with the exception of heat-related deaths.
According to the National Weather Service (NWS), since 1940, flooding has resulted in 8,616 fatalities, or a 30-year average of 88 per year. That average has, unfortunately risen over the past ten years, reaching an average 103 flood-related fatalities per year from 2013 through 2023. However, keep in mind, that number is likely higher after several significant flood events in the U.S in 2024.
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With that being said, it's crucial to be prepared and know what to do should flooding impact your area.
This starts with knowing a little about the we see in Siouxland:
Flash Flood: Flash floods generally develop within 6 hours of the immediate cause. Causes of flash flooding include heavy rain, ice or debris jams, and levee or dam failure. These floods exhibit a rapid rise of water over low-lying areas. In some cases, flooding may even occur well away from where heavy rain initially fell
Ice Jam Flooding: As ice or debris moves downstream, it may get caught on any sort of obstruction to the water flow. When this occurs, water can be held back, causing upstream flooding. When the jam finally breaks, flash flooding can occur downstream.
Snowmelt Flooding: When the major source of water involved in a flood is caused by melting snow. Unlike rainfall that can reach the soil almost immediately, the snowpack can store the water for an extended amount of time until temperatures rise above freezing and the snow melts. This frozen storage delays the arrival of water to the soil for days, weeks, or even months. Once it begins to melt and does reach the soil, water from snowmelt behaves much as it would if it had come from rain instead of snow by either infiltrating into the soil, running off, or both. Flooding can occur when there is more water than the soil can absorb or can be contained in storage capacities in the soil, rivers, lakes and reservoirs.
River Flooding: Occurs when river levels rise and overflow their banks or the edges of their main channel and inundate areas that are normally dry. River flooding can be caused by heavy rainfall, dam failures, rapid snowmelt and ice jams. The National Weather Service issues Flood Warnings for designated River Forecast Points where a flood stage has been established:
The stages of river flooding are as follows:
–Minor: low-lying areas adjacent to the stream or river, mainly rural areas and farmland and secondary roadways near the river flood.
-Moderate: Water levels rise high enough to impact homes and businesses near the river and some evacuations may be needed. Larger roads and highways may also be impacted.
–Major: Extensive rural and/or urban flooding is expected. Towns may become isolated and major traffic routes may be flooded. Evacuation of numerous homes and businesses may be required.
When flooding is a possibility or imminent, there are several different flood alerts your local National Weather Service may issue:
-Flood Watch or Flash Flood Watch
-Flood Warning or Flash Flood Warning
Like Severe Thunderstorm or Tornado Watches/Warnings, it's important to know the difference between a watch vs. warning during flooding events:
The major difference between flood watches/warnings and other severe weather watches/warnings is the duration of each alert. Especially a Flood or Flash Flood Warning, which can last several hours, unlike for example, a Severe Thunderstorm Warning which generally last half and hour to an hour at most.
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Similar to Severe Thunderstorm and Tornado Warnings though, the National Weather Service is transitioning to impact-based Flash Flood Warnings, some of which parts of Siouxland saw with the June 2024 flooding event.
Here is how this works:
There is the most basic Flash Flood Warning, issued when Flash Flooding is imminent or occuring and will pose a risk to life and property. This is like how we have the base Severe Thunderstorm Warning.
Then there are two different tags the NWS may add on to a Flash Flood Warning.
1.) Considerable: Rare. Used if there are indications that flash flooding capable of unusual severity or impact is imminent or occuring. Urgent action is required to protect lives & property.
2.) Catastrophic (Flash Flood Emergency): Extremely Rare. When a flash flood threat to life and property is imminent or occuring with catastrophic damage and impacts occurring or imminent. Floodwaters will rise or have risen to levels rarely, if ever, seen. This is the flood equivalent of a Tornado Emergency.
More information about impact-based Flash Flood Alerts can be found here.
Before flooding strikes though, make sure you and your family have a plan. Also make sure you know your flooding risk: Is your home, business or school in a floodplain? Where is water likely to collect on the roadways you most often travel? What is the fastest way to get to higher ground? Where will we evacuate to, if necessary?
You'll also want to check your home insurance. Most standard policies don't include flood insurance, so you may need to contact your insurance company or agent purchase flood insurance and ensure that you're covered. This will need to be done well in advance of any potential flooding since many policies take at least 30 days to go into effect, according to NWS.
During flooding or when flooding is likely, stay informed, make sure you have several ways to receive warnings, and be prepared to evacuate, if needed. Obey all evacuation orders and get to higher ground immediately, if issued.
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Even if evacuation isn't imminent or required during a flooding event, flood present many danger within and around your home.
If you have flooding in your home or business, avoid rooms where water is covering electrical outlets and cords. This could pose the risk of electrocution.
Likewise, outside, avoid walking through floodwaters, which could have submerged electrical wires and downed power lines, that may or may not be electrically charged.
Aside from the risk of live electrical lines, floodwaters harbour may other hazards. Just 6 inches of moving water is enough to sweep you off your feet.
In addition to this, floodwater may be deeper than it appears and may contain things like: sharp objects, chemicals, bugs & snakes, sewage, debris, and bacteria.
Don't drive through floodwaters either. Remember, 'Turn Around, Don't Drown.
12 inches of water, just one foot of moving water, is enough to sweep a car away. And 18 inches of moving water can sweep away a smaller truck or SUV.
After flooding, continue to stay informed: Stay tuned to your local news for updated information on road conditions. Watch for boil water advisories as water may not be safe to drink, cook, or clean/shower with after a flood. Check with your utility company, many have apps, for updates on service restoration.
Additionally, carbon monoxide poisoning is one of the leading causes of death after storms in areas dealing with power outages. Never use a portable generator inside, not even in the garage.
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Continue to avoid floodwater, avoid impacted areas, obey all road closures other informational signs that may be put out.
Finally, don't enter a flood damaged home/building until an All Clear has been given by authorities. Water can cause floors to collapse, ceiling to fall, etc. Ensure the electricity has been turned off and have only your power company or a qualified electrician fix wires. Contact your insurance agent to discuss property damage and most importantly, be sure to let family and friends know you're ok.
For more flood safety tips and information, visit the National Weather Service . There, you can find state-specific flood information and safety tips.
And for the latest weather any time in Siouxland, visit the .
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