What's The Deepest Storm Surge In History?

- 2022 had so many crazy viral weather videos.

But how do you pick one that really encapsulates what's happening with our climate?

We chose this one because it's a groundbreaking look at a climate impact that has the potential to affect almost a third of the US population.

Sea level rise at just 0.14 inches per year is one of the slowest things to watch ever, that is until it's combined with the most deadly and destructive part of a hurricane, storm surge.

But until just a few years ago, we didn't understand what exactly causes it.

- Up to 2005, scientists and forecasters used to think that the amount of storm surge was correlated with how strong a hurricane was.

But Hurricane Katrina was truly a turning point and a learning experience for all of us.

- US coastlines hold over half of the nation's economic productivity, and population density continues to grow in these areas.

And with more powerful hurricanes acting on higher sea levels, climate change is making these surges more destructive than ever before.

So why has our understanding of the causes only recently developed?

Well, one reason for the lack of interest might be that it's very hard to capture on film.

And that's why this video feels so important.

Max Olson went out before Hurricane Ian made landfall, set up, and left a camera recording that created a shot far too dangerous for any person to film.

And even Max didn't catch the most sickening detail of the video.

- And I pulled out the footage and it was just, like...

It was truly remarkable, like nothing I've ever seen before.

(wave crashes) When I posted it, somebody commented and said, "Wow, I hope the person that's in there is okay."

I'm thinking, "What are they talking about?"

(water crashes) - We'll get back to the video, but first, we wondered how high a storm surge could actually get and what makes it bad in some storms and way worse in others?

- So one of the most challenging and destructive parts of a cyclone is not directly the wind from the hurricane, but rather the storm surge.

Storm surge is saltwater pushed on land by the winds of a hurricane.

- These strong winds push against the water surface, causing it to pile up.

The wind and low pressure system can also displace water elsewhere, causing a reverse storm surge on the opposite side of the hurricane.

All this water has to go somewhere, and when the storm is near a coastline, it piles up on shore.

If it lines up with high tide, the impact can be much worse.

Just three feet of water makes evacuation dangerous or impossible.

Six feet of water floods out the first floor of buildings and houses and can carry away large vehicles.

The deadliest hurricane to ever hit the US brought an eight to 12-foot surge, killed 8,000 people, and left nearly a third of Galveston, Texas's population homeless.

A century later, Hurricane Sandy caused a 14-foot surge in New York, flooding nearly a fifth of the city and causing $19 billion in damage.

Hurricane Ike brought 22 feet of storm surge and, once again, hammered Galveston, Texas.

But the highest storm surge in the US was 28 feet during Hurricane Katrina.

That's double the surge that hit New York during Sandy.

That level of surge could put much of the city underwater with the risk of inundation reaching all the way to Central Park.

But the largest surge ever recorded globally?

Well, the high water mark when Cyclone Mahina hit the northeast coast of Australia was reported at 42 feet of additional water.

Just how much of that can be attributed to storm surge, waves, and other factors is debated.

But, for reference, that's higher than the highest land elevation in Miami, New Orleans, Virginia Beach, and Charleston, just to name a few coastal cities.

But we wanted to know why do some major hurricanes produce a small storm surge while other weaker hurricanes produce devastating ones?

Well, let's go back to mid-September 2022, when Hurricane Ian began to take shape.

Storm chaser Max Olson headed to Florida.

- Right as we got onto Fort Myers Beach, we were immediately concerned because the orientation of that coastline, already, it's kind of like a catcher's mitt.

There's no sea walls.

There's no mounds of dirt, barriers, or anything.

It's just pretty much unimpeded flow right to the center of town there.

We're going and looking for places where we can put our unmanned surge probes.

They're basically just a waterproof camera with a battery pack, and they last for 26 hours.

And we're able to put them in areas that are just kind of too dangerous for us to go and stay.

We pulled a Ford Expedition onto a curb and then I climbed up on top, and stood as tall as I am, which is six, four, and put the probe up on the pole.

We could barely sleep that night.

I mean, the storm was strengthening.

It was coming in at the really truly worst orientation that it could.

(water splashing) (winds blowing) (water splashing) - Whoa!

- My god!

- The following morning, we went to go collect our surge probes.

We started getting close to Fort Myers Beach and we started seeing progressively worse and worse damage.

And then as we got over the bridge to Fort Myers Beach, it looked like something out of a movie.

Just completely catastrophic damage.

We somehow were able to make it to where our camera probe was and we were able to pull the car up enough and get the camera box pulled down.

- [Maiya] When Max pulled up the footage of the storm surge, he was shocked by what he saw.

- It shows how the storm surge just slowly creeps in at first and then starts rising, rising.

Before you know it, you basically have waves in downtown Fort Myers Beach.

You had swells that were going up and knocking down houses.

- [Maiya] But it wasn't until Max posted the video to YouTube that he learned something even more shocking.

- [Max] The camera probe captured a pink house which we thought was inhabited, and it just floats away.

I start scrubbing back through the footage and you can see somebody poke their head out the door.

- Then the surge quickly rose to three feet, which, as we learned earlier, means it was too late to safely evacuate.

And they had no idea just how much water was coming.

- I was convinced that I had just posted a video of somebody's last moments because I thought there was no way you could survive that.

- [Maiya] The house had completely floated away while Max was recording.

And Max had no idea what happened to its inhabitants.

- Hurricane Ian was a very powerful hurricane.

It was associated with very strong winds of up to 150 miles per hour, pushing a lot of water inland.

But it was also approaching from the western coast of the Florida Peninsula.

And it so happens that the ocean floor, it's very shallow there.

That means that a hurricane can push a lot of water inland a lot more than it would if the ocean floor was a lot deeper.

- Early estimates for the storm surge are 15 feet of additional water in a part of Florida that hadn't seen a major storm surge in years.

And Max wondered if he had recorded the last moments of someone's life.

- Then I get a message the next morning saying, "Hey, I'm the sister of the person who was in that house.

We spent all night searching for my brother and his girlfriend who were in that house, Todd and Annette and their two dogs."

And somehow, some way, they found them both alive.

- [Maiya] As the house washed away, they were able to hold on to a telephone pole and a tree with their two dogs, then floated to a different house where they survived the rest of the surge.

- So we just came up with everything that we could, filled up the car, and then drove it down.

And we actually got to meet him and shake his hand and give him a hug.

And that was just 24 hours after posting that video.

- Ian made landfall as a Category 4 storm with 15 feet of storm surge.

So why did Hurricane Katrina destroy so much of Mississippi and Louisiana with a 28-foot storm surge as just a Category 3 when it hit land?

Well, it turns out, size matters.

- Hurricane Katrina had a very large wind field, meaning that there were hurricane force winds extending over a very, very large area, much larger than the area of Hurricane Ian's hurricane force winds.

Hurricane strength, how big the hurricane force wind field is, the angle of approach, the ocean floor bathymetry, the speed, all of those factors combined together into generating the storm surge.

- So Ian had wind speed, shallow coastal water, and a catcher's mitt-shaped shoreline, but, thankfully, it was smaller than Katrina.

Rosimar told us that scientists are now researching how to forecast the impact of a hurricane's size on a storm surge.

But forecast models are missing one more detail.

- So if there are any underwater canyons or other features on the bottom that can impact the flow of that water, it can really change which areas might get a higher or lower storm surge.

But if you don't capture those features in the bathymetry and use those in your model for storm surge, your numerical model, you're not gonna be able to accurately predict exactly how much storm surge and where that might be going.

So only 25% of our ocean has really been mapped to modern standards, so that's a lot of things left to map.

- [Maiya] To fill that gap, NOAA is partnering with a company that makes an un-crude floating drone that can spend long periods at sea mapping the ocean floor.

- [Brian] So these are all propelled primarily by the wind.

We have a large, rigid wing for a sail.

We try and use that as much as possible because that's what gives us the long endurance at sea.

Control them via satellite, collect that bathymetry data.

- And climate change is making the need for improved storm surge forecasts even more pressing.

- Over the coming decades in the 21st century, our theory and our high resolution, large scale climate models are indicating that we should expect more intense hurricanes, that their peak wind speeds should be larger.

- If you take the same hurricane today with the ocean level from the future, that same hurricane today can cost a lot more storm surge in the future just because it has a higher amount of water that it can push inland.

So that turns into a combined effect where you have not only higher amounts of ocean water due to sea level rise, but also a stronger hurricane, and the combination of both can turn into much higher storm surge inundation in the future if our planet continues to warm at the rate it is warming.

- You may say, "Oh, you know, if it starts getting bad, then we'll get out of there."

That's not always the case.

In fact, many times, when you get to that point of realization, it's too late.

You don't have time to get out.

Make the plan and execute on it when the time is there.

If there's any, if there's one person I can convince to do that because of what we do out there, then that makes it all worth it.

- Improved storm surge forecasts can be incredibly useful to determining which communities will be the most prone to storm surge inundation.