We measure the strength of hurricanes by their wind speed. But it’s storm surge that’s by far the bigger threat.
An analysis of U.S. hurricane deaths from 1963 to 2012 found that nearly nine in 10 deaths were caused by rainfall, rough surf and, especially, storm surges. It was these storm-driven waves that toppled Hurricane Katrina’s levee system.
But what is storm surge? Why is it so deadly and what can we do to stay safe?
A Surge of Water
As a hurricane spins out at sea, its winds push huge amounts of water ahead of it. As the sea gets shallower closer to land, that water “piles up” far above the normal water line.
Along coastlines with a broad, shallow seafloor — where that water has little place to go — the storm surge can be devastating. In places, Hurricane Katrina pushed up to 16 feet of water, punching through levees in more than 20 places.
Because the water from storm surges is pushed ahead of a hurricane, the storm doesn’t have to make landfall to cause serious damage.
People experience a storm surge as a rapid rise in water level — perhaps several feet in a few minutes — and not a “wall of water.” Still, this wind-driven water is powerful. Just a cubic yard of water weighs almost a ton, and it’s being pushed forward by the storm itself.
That makes it almost impossible to walk or drive in a storm surge; rescues, too, are difficult during a surge.
How to Prepare
Though they’re most devastating along the beach, storm surges can reach for miles inland in low-lying areas. This is in part because water can be pushed up the rivers and streams that empty into the ocean.
The best way to prepare for a storm surge is to secure your property and leave before it hits. Here are some other tips:
- Know Your Elevation: The federal government has created maps to show which areas are most vulnerable to storm surges. Check out this map to learn how high the storm surge might be near your home depending on a hurricane’s intensity, from Category 1 to Category 5.
- Prepare Your Property: Board up your doors and windows, secure objects in your yard and turn off utilities. Store important documents at the highest level of your home.
- Pack an Emergency Kit: If there’s an order to evacuate you should be ready to leave. We compiled this list of basic hurricane supplies in an emergency kit.
In the last few years, flooding from rainfall — instead of storm surges — has been the biggest cause of fatalities. During Hurricane Florence, more than half of victims died when they were trapped in their cars during flooding.
If you’re experiencing flooding or a storm surge, stay inside. Don’t drive through flood waters — it only takes a few feet of moving water to carry a vehicle away.
Be prepared for power outages, as well. If you’re a new parent looking to plan for a hurricane, check out our post for tips on how to prepare.
Knowing what a storm surge is and how to stay out of its path is one of the most important steps you can take to protect you and your family.