Name: How Storm Surges Work—and Why They’re So Deadly
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The deadliest part of a hurricane isn’t the wind–it’s water. Here’s what causes a storm surge, and which regions are most at risk.

The deadliest part of a hurricane isn’t the wind–it’s water.

The deadliest part of a hurricane isn’t the wind–it’s water. Here’s what causes a storm surge, and which regions are most at risk.

How Storm Surges Work—and Why They’re So Deadly

The deadliest part of a hurricane isn’t the wind–it’s water.

Planet Earth

How Storm Surges Work—and Why They’re So Deadly Published October 13, 2022Narrator: Storm Surge is the most deadly component of a hurricane ... resulting in half of all hurricane deaths.James Marshall Shepherd: Although the focus is often on wind speed in hurricanes, the deadliest aspect of a hurricane is water. The storm surge and the inland freshwater flooding.Rosimar Rios-Berrios: The storm surge is very, very dangerous because the water gets pushed inland and it can cause water levels to rise and inundate coastal cities in a very short amount of time.Narrator: The southeastern coast of the US is especially vulnerable to hurricanes — and Florida in particular — for its geography and proximity to warm, tropical waters.James Marshall Shepherd: Hurricanes derive their energy from warm ocean water. The Gulf of Mexico really was a powder keg ready to blow - if Ian tapped into that really warm, deep water.Narrator: Hurricane Ian hit the coast of Florida on September 28th, 2022. Overwhelming the southwest coast with rain, storm surge, and wind speeds of up to 155 miles per hour, making it one of the most powerful storms to make landfall in the US. The highest recorded storm surge in the US was 27.8 feet in the the Bay St. Louis and Pass Christian areas of Mississippi during Katrina in 2005 — one of the deadliest storms in US history. But what makes storm surge so deadly and why are they so unpredictable?James Marshall Shepherd: It's not just a big wave. It's really a massive inundation of a large wall of water.Rosimar Rios-Berrios: Water is rushing in very fast and the water levels are increasing like super fast as well.Narrator: As hurricane winds intensify, they actually start circulating water in the ocean.Marshall Shepherd: It's not simply just the shoving of the water on to the coast. That wind blowing on the surface of the ocean creates the circulation in the ocean as well. And as long as that's out over the deep ocean, you don't really notice it. But as the storm gets closer to the land and the shelf, you start to see the rise of that water as it moves inland.Narrator But there are a number of factors that contribute to the intensity of a storm surge.Jennifer Collins: So you've got storm intensity, the size of the storm, the forward speed and the angle of the approach. So those are all very significant factors. But// the continental shelf is important.Narrator: The continental shelf – or the underwater edge of the continent – plays a big part in storm surge. The shallower the shelf, the greater potential for storm surge. This is one of the things that makes the Tampa region of Florida so vulnerable to hurricanes.Jennifer Collins: So near Tampa Bay and off the coast of Florida, you have a very gentle sloping shelf. And with this shelf is going to cause much more of a storm surge. Whereas if you take Miami, your storm surge may be half as less because it drops off very quickly on the east side of Florida.Narrator: But location relative to a storm is an important factor. North of Hurricane Ian, in Tampa Bay, the storm actually drew water away from the coast.Rosimar Rios-Berrios: But on the northern side of the storm, when the winds are blowing essentially away from the coast, then they can have the same but reverse effect where the winds are blowing away from the coast. They can essentially push the water away from the coast. And what you get is what is known as negative or reverse storm surge, which is what we saw in Tampa Bay.Narrator: Another factor that experts suspect is making storm surge worse? Climate change.Jennifer Collins: Already those sea levels are higher than what they used to be. So add on top of that the storm surge from the hurricane. We have these higher waters. You could have an even happening at high tide, which makes it even worse. And then the water pushing in. So that's a big impact from climate change on the hurricanes.Narrator: Researchers also think that hurricanes are intensifying faster, and moving slower. Warming may cause storms to move more slowly as high and low pressure systems become more balanced.James Marshall Shepherd: Going forward, hurricanes, because of climate change, will likely increase in intensity.Narrator: This is partly because oceans are warming in response to climate change — and warm water is one of the main ingredients for hurricanes — they are fueled by warm surface water.James Marshall Shepherd: We can't say as much about the frequency of occurrence, which is what you often see. People say, Oh, we're going to have more hurricanes because of climate change. That's actually a a statement that needs a bit more care. The current scientific literature suggests that we'll see stronger storms on average, not necessarily more frequent ones of the literature still emerging on that.

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How Storm Surges Work—and Why They’re So Deadly

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Storm Surges and New York City

What Makes a Hurricane?

Hurricanes and Climate Change