Flood Safety
This interactive story map contains educational and safety information pertaining flooding and flood safety! Scroll down to see more!
Overview
Infographic: NOAA/NWS
The following story map is designed to provide educational information on flooding and safety information! On average, NWS Milwaukee/Sullivan issues 12 flash flood warnings each year. However, there have been many years where more than 12 flash flood warnings have been issued. In 2008, the NWS Milwaukee/Sullivan office issued a total of 52 flash flood warnings!
Causes of Flooding
Heavy Rain
Heavy ran can bring widespread or localized flooding concerns. Urban areas and low-lying areas are more flood prone, as water can easily collect and runoff.
Under the right conditions, quick moving thunderstorms can produce very heavy rainfall in urban areas, but often training or very slow moving thunderstorms cause the greatest concerns for flooding and flash flooding. The radar loop on the right is an example of thunderstorms and heavy rain training across Dane County, where significant flooding occurred.
Heavy rain can cause river flooding as well, even after heavy rains have passed. This is especially true when soils are already saturated and runoff is enhanced across river basins. Check out the graphic below for more extensive details behind the science of river flooding!
Infographic that describes river flooding and how it works. Infographic: NOAA/NWS.
Spring Snowmelt
Flooding can occur during Spring snowmelt depending on how much snow is on the ground and how much water is stored within the snowpack. Flooding becomes more of a concern during the snowmelt when:
- The ground is still frozen and water released from the snowpack has nowhere to go.
- There is a high amount of liquid water in the snowpack and the snowpack either melts quickly or heavier rain occurs.
When heavy rain falls with snow still on the ground, the stored water within the snowpack can easily be released. This makes it seem like it rained more than it did! When we're dealing with the trifecta of: frozen ground, snowpack, and heavy rain, this is when concerns very become high for flooding and serious impacts.
River Ice & Ice Jams
Before an ice jam can develop, an outbreak of colder air must occur to allow ice to from on rivers. When temperatures warm and snowmelt begins, chucks of ice break up and can clump together. This area of ice piling up is the ice jam and acts to block water from flowing downstream, causing water to backup upstream of the ice jam.
The image shown on the right is an ice jam that developed on the Milwaukee River in March of 2019. Below are the corresponding hydrographs from this ice jam, showing the rapid rises overserved on the Milwaukee River upstream of March 2019 ice jam.
Hydrographics from the ice jam that developed on the Milwaukee River in March of 2019.
Dam or Reservoir Beaches
It usually takes excessive amounts of heavy rain, or heavy rain on top of water loaded snowpack, to cause a dam to structurally fail. It is very difficult to predict these events in advance, so if you live near a dam it is even more critical you stay weather aware, especially during heavy rain events.
Back in 2008, multiple rounds of heavy rain tracked across southern Wisconsin bringing widespread heavy rain. Locally up 10 to 13 inches of rain fell within a 2-day stretch across portions of southern Wisconsin. On June 9th, 2008, a portion of Lake Delton gave way to the high water and channeled a new way into the Wisconsin River. The man-made lake drained out within two hours.
Watch vs Warning
Watch vs Warning
Similar to severe or tornado watches, a flood or flash flood watch means flooding is possible. If flood or flash flood warning are issued, this means the flood threat in imminent!
Flood Watches are typically issued ahead of moderate rains that could result in rising levels on rivers.
Flash Flood Watches are issued when heavy rain is expected to cause live-threatening flooding. These type of situations usually develop quickly after the onset of heavy rain.
Types of Flood Warnings
Areal Flood Warnings are issued for situations when water is expected to gradually rise, especially in area that are flood prone due to moderate to heavy rainfall.
River Flood Warnings are issued when rivers are expected to respond to recent rainfall and/or snowmelt, with water levels expected to rise and exceed bankfull.
Flash Flood Warnings are issued when heavy rain is expected to cause water to rise rapidly, resulting in life-threating conditions to develop. Urban areas with a lot of concrete, low-lying flood prone areas, and locations near flashy streams or creeks can be most vulnerable during flash flooding.
Flash Flood Emergencies!
We reserve flash flood emergencies for situations when we expect life-threatening conditions. Under these conditions, multiple water rescues and catastrophic damage to homes, roads and culverts are possible.
Flooding in Wisconsin
Want to learn more about what causes flooding in Wisconsin and some of our more historical flooding events? Visit the link below to learn more!
Before, During, and After
Before a Flood
Prepare ahead of time! Do you have a communications plan and emergency kit ready if needed? Are you camping near a river during a period when the flood risk is enhanced?
Know what your risks are. Do you live near a river that floods often? Do you life in or near a floodplain?
If you needed to evacuate, are you prepared? Do you have a plan? Do you have an escape plan if you need to evacuate? If you know conditions are worsening at your location or you know you live in a flood prone area, evacuate yourself before conditions get worse!
Charge Essential Devices & Have Multiple Ways to Receive Warnings
Keep those cell phones and portable radios charged! You may lose power and your ability to recharge important devices that can help you communicate and receive life-saving information!
Do you have multiple ways to receive warning information? Especially if you're planning on traveling through an unfamiliar area or are out camping, you may not have internet connection or the best cell phone reception.
Understanding River Forecasts
The forecast includes 48 hours of precipitation during winter and 24 hours of precipitation during summer. This forecast precipitation is then taken into account when creating the river forecast and how high water levels are expected to rise. The image on the right shows you how to read these river forecasts.
Below is a link to our Advanced Hydrologic Predictive Services website for southern Wisconsin. To view individual river forecasters, click on the circle with the gauge location of your choice.
During a Flood
Conditions can change rapidly as flood waters rise. Don't wait until it is too late to act!
Stay informed. If you have power, tune into local TV or radio stations. Keep those portable radios charged in the event you lose power!
Avoid areas where water is covering electrical outlets! Avoid the basement area or any area that water is covering electrical outlets or powered devices.
If you find yourself trapped in high water conditions, move to the highest area you can and call 911!
Obey Evacuation Orders!
If local authorities have asked you to evacuate, do so before conditions get worse!
This is where your level of preparedness comes into play! Don't wait until the last minute to prepare.
AVOID FLOOD WATERS
Never drive into flooded roads! Obey all road closures and NEVER drive around barricades! First, you don't know how much water it is you're driving into and second, you don't know if the road is still there! Flood waters can quickly erode/damage roads and culverts.
Don't play in or walk though flood waters! Flood waters can contain bacteria, dangerous debris, electrical wires, and animals you may not be accustom to seeing.
After a Flood
Listen to local authorities! Wait until you have the all clear to head back home.
Continue to obey an road closures. If there is damage to local roads, it may take time for repairs to be done!
Safety!
Turn Around, Don't Drown!!
Say it with us, Turn Around, Don't Drown!
More than half of all deaths related to flooding occur in vehicles.
You do not know how much water you may be driving into, if the road as suffered damage or is even still there! Flash flooding commonly results in washed out roads and culverts.
Don't take that risk. Your loved ones are counting on you to come home.
Avoid Flood Waters!
You do not want to mess around with flood waters. They can contained a number of dangerous hazards, most of which you will not see until it's too late!
Avoid flood waters. Do not walk in or play in flooded waters. This includes rivers that are outside of their banks!
Camping During Heavy Rain?
Stay up to date on the forecast before you leave your home, and have ways to stay updated while you're camping!
Remember, sometimes you may not have internet access or good cell phone reception!
Nighttime Flooding
At night, flood waters are nearly impossible to see. If you are traveling at night, obeying all road closures and never driving around barricaded roads is EVEN more important.
If you're traveling during periods of heavy rain and you know a flash flood warning is in effect, simply pulling off to the side of the road isn't a good idea. Find a safe place to seek shelter!
Have a Communications Plan!
Know how you will communicate with loved ones during and after a flood. It can be a very stressful time, so checking in with loved ones to know you're okay is important. Find out how at ready.gov/make-a-plan.
