February 3, 2023

M-Dudes

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Storm surge is deadly. We built a computer model to show how. |

Table of Contents

Understanding — and fearing — this threat can make the difference between life and death.

So the Tampa Bay Times wanted to make it easy to grasp, showing how storm surge can hit with the force of a train. The newsroom’s tool emphasizes the brutal reality behind the adage: Run from the water, hide from the wind.

This is why we leave.

The simplest way to estimate the power of storm surge is to consider a wave as one solid object crashing into a building.

We’ll set the size of the wave at feet high and feet wide.

Let’s use feet for the length of the building’s wall as well. Seawater is heavy: One cubic foot, roughly three shoeboxes worth, weighs 64 pounds.

Our calculation shows that this wave results in more than pounds of water rushing toward our building.

That alone would be a lot of force. But we also need to consider how fast the wave is moving.

Let’s use 8 mph because that’s how quickly Hurricane Ian was traveling at landfall.

When we add speed, the wave crashes into the wall with over pounds of force.

For perspective, Vita Vea is a star defensive tackle for the Tampa Bay Buccaneers. He crushes quarterbacks and leads the team in sacks.

Vea is big and fast. He weighs 347 pounds and has an arm length of 32 inches. He can run a 40-yard dash in 5.1 seconds — about 15 mph.

Tampa Bay Buccaneers defensive tackle Vita Vea (50) sacks Los Angeles Rams quarterback Matthew Stafford.
Douglas R. Clifford

If Vea ran full speed into the same wall with his arms outstretched, he would hit with more than 33,000 pounds of force.

Still, it would take more than Vita Veas to match the force of our wave.

That’s just a back-of-the-envelope calculation, though. Surge is even stronger.

Using water level data from the Caloosahatchee River gauge in Fort Myers during Ian, we can see how the power changes, ebbing, flowing and building over time.

This calculation includes the force that standing water exerts on nearby objects, which is called hydrostatic pressure.

Not only is that a lot of force at any given moment, you can see that the surge reaches its maximum force quickly: within the first quarter of the simulation. That means the danger comes swiftly, and by the time water is rising, it may be too late to leave.

We can take this even further by using what’s known as finite volume analysis.

This requires special expertise, so we teamed up with water researchers at the University of South Florida — Juan Penaloza Gutierrez, Thathsarani Dilini Herath Herath Mudiyanselage and Dr. Andres Tejada-Martinez — to improve our model.

A Fort Myers Beach resident captured Ian’s surge on video.
Karen DeHays

Methodology

We came up with three ways to calculate and model the force of storm surge to help readers better understand its power.

The first model simulated a wave as a solid object with a specific mass and velocity. The second model simulated the wave’s drag force across the surface area of a wall.

The third model is a finite volume analysis, created in Ansys Fluent, by water researchers at the University of South Florida.

Our methodology — reviewed by 4 physics and engineering experts — is available here along with the code that powers the graphics on this page.

The team

  • Reporting and graphics:
    Eli Murray
  • Contributors:
    Zachary T. Sampson
  • EDITORS:
    Rebecca Woolington, Langston Taylor, and Mark Katches
  • Fluent Model:
    Juan Penaloza Gutierrez, Thathsarani Dilini Herath Herath Mudiyanselage and Dr. Andres Tejada-Martinez