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Tides and Oceans

Storm Surge

Often when we think of powerful hurricanes, we picture the strong winds. Trees are blown over, and debris are flying down the street.

But the biggest danger in a hurricane is not always damage from strong wind, it’s often from storm surge.

Storm surge? What?

Weird! I've never heard of storm surge before.

Storm surge is the unusual rise of water that happens during a big tropical storm. When the water rises, dangerous flooding can happen near the coast. Storm surges are not the same as high tides, but when a storm surge happens during a high tide, it can result in even higher water. Sometimes the water can rise as many as 20 feet. And that doesn’t mean there is one 20-foot wave that quickly goes away; it means that the water level rises that much, so it can go very far inland if the ground is flat.

a diagram of a shoreline with water levels during high tide, low tide, and a storm surge

What causes storm surge?

Storm surge happens because water gets pushed toward the shore by the force and pressure of a big storm. It’s hard to predict exactly how big a storm surge will be because it depends on so many things. It’s affected by the intensity of the storm, forward speed, size, angle of approach to the coast, pressure, and the shape of the coastline.

Danger extends inland, too.

an animated gif of rivers overflowing because of storm surge

People a distance from the coast might think they’re safe during a storm surge, but that can be tricky. The rising water level during a storm surge can also affect rivers and streams that empty in the ocean. The surge of water can travel far upstream, causing flooding far from the ocean.

I'll definitely evacuate. I'm not messing with storm surge.

What to do

If you hear warnings about storm surge in your area, you definitely need to evacuate. Water is a very powerful force. Even just a few inches of flooding make driving almost impossible, and then you’re stuck. No one wants to be stuck in a flood. Take storm surge seriously, and evacuate vulnerable areas.

A photo of Staten Island before and after hurricane Sandy that shows boats further inland as a result of the flooding

This is the same spot in Staten Island, New York before and after Hurricane Sandy. Notice where all the boats are in the "after" photo. Many were moved onto land as a result of the flooding.

"Before" image captured by Google; "After" image captured by NOAA's National Geodetic Survey