How to Know When You're Going to Flood

About: If you guessed that I am a freelance writer and a flood survivor, you're 2-4-2.

Almost once a week, we see a new headline about an epic flood. If you've never experienced a flood, it's something that happens to someone else. It'll never happen to you, right? Think again...

By combining what you're about to learn with a little common sense, you will have ample time to move out of harm’s way.

Had I known about this resource before Tennessee’s Thousand-Year Flood in May 2010, I would have found my way to safety before the first drop of water entered my home instead of swimming for my life to the volunteer rescue crew’s canoe.

Pay special attention to the last two steps. That’s where “ you’ll find information that allows you to get to safety with time to spare.

In the next steps, we’ll zero in on your river and bookmark the exact URL for future reference. Let’s get started.

Step 1: The Advanced Hydrologic Prediction Service

That's a mouthful, so I just call it the “Advanced Flood Warning System.”

To find NOAA's Advanced Hydrologic Prediction Service, go to

You'll see a map of the U.S. overlaid with different colored dots (don’t click any of them). On the right, you’ll see the number of locations currently experiencing flood conditions. You can tell at a glance if your area is in danger of flooding, but we're going to see a lot more local information in the following steps.

In the next step, I'm going to show you the easiest way to find the river closest to you.

Note: This information is courtesy of NOAA and is in the public domain.

Step 2: Find Your River

Find the “Zoom Box” on the state map, and click it. It’s on the left side of the state map about halfway down the map. When you click the map, it turns gray, and your cursor changes to a crosshair.

Draw a box around your local area. You’ll see several small squares and/or circles. Hover your mouse over the squares/circles until you find the one closest to your neighborhood, and click it.

A quick-view graphic pops up. Click it to open the graph in the browser.

Bookmark this URL now because you may need to find it quickly someday.

In the next step, we’ll explore the Hydrograph.

Step 3: Reading the Hydrograph

The only tab along the top you care about is the Hydrograph tab. Just above the graph, you see dates. Under the dates, you see the flood stage and the last time the river stage was recorded.

The dotted vertical line represents the last recorded river stage.

Anything to left of the vertical line is in the past and denoted by a thick blue line. Anything to right of the line is in the future and denoted by a broken line. The broken line river levels are forecasts and are subject to change.

By comparing the flood stage to the present river stage, and by knowing how much rain is forecast, you can get a general idea about your probability of flooding.

In the next step, you’ll get a much clearer picture of your chances of flooding, and you’ll know when to get serious about preparations and evacuation.

Step 4: Taking Action Based on Flood Categories

Scroll down to the Flood Categories below the Hydrograph. Your river’s numbers will vary from those in the image. The two categories you care about are Action Stage and Flood Stage.

When the river level reaches the Action Stage, local authorities start making preparations and so should you.

I start moving irreplaceable items to the second floor. I get the cat carriers ready to go, pack the car with my go bag, and start hitting the refresh button on this page at frequent intervals. My passport drive, thumb drives, and important papers are ready to travel. I’m working off the notebook screen so I can grab the computer and run if the time comes.

By now, my phone is ringing off the hook, and I’m letting neighbors know that I’ll call them night or day if we need to evacuate.

The Action Stage is only halfway to the Flood Stage in my area, but as a flood survivor, I’m on high alert and ready to get out at a moment’s notice, but I’m not yet at the “must go” stage.

In the next step, we’ll look at flood levels of landmarks in your area and determine when to bail and which routes are safe (i.e., not underwater) to take out of your neighborhood.

Step 5: Interpreting Flood Impact - When to Get Out of Dodge!

At what point will the roads near your home become impassable? How long before your home is in danger of flooding? Which route should you take to safety? The Flood Impact Chart answers those questions.

The left column is series of river stages in feet. In the last step, we learned that 14 feet is the Action Stage in this example. The right column indicates what floods at a each level. The chart tells me that Hwy. 100 floods early. I know that there are only two main arteries out of my neighborhood, so once Hwy. 100 is flooded, I have to take Hwy. 70. That’s life-saving information. Hwy. 100 now has a bridge named after two residents in our neighborhood from the last flood.

I’m in charge now, and I’m smart enough to learn from my mistakes. And now you have the tools to give you ample time to remove yourself from danger in the event of a flood.

Additional resources:

Waves of Change: How Surviving Tennessee's Worst Natural Disaster Changed the Lives of a Survivor, a Rescue Professional, and a Family Grief Counselor

Waves of Change Kindle version

USGS Flood Resources



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