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Understanding storm surge and inundation

NORTH CHARLESTON, SC (WCBD) -  One of the common misconceptions about storm surge and  inundation is that it's just a coastal problem. But that's untrue, especially in the Lowcountry.

Areas like the Ashley, Cooper and Wando Rivers rise and fall with the tides and is one of the areas that would be effected by storm surge.

"People kinda envision, oh its just the beach or its just the barrier islands or sea islands or whatever," says National Weather Service Warning Coordinator Meteorologist Ron Morales. "It isn't. It's anywhere that's affected by tides. And that's a lot."

Storm surge and inundation can effect any tidal basin, meaning any waterway that rises and falls with the tides.

"It goes up the Cooper River and the Ashley River and the Wando River and Stono and all the other inlets and smaller things that we don't even think about, creeks and marshes. All of those are effected by the water being pushed ashore by the hurricane, which is the surge and then how much inundation or water above the surface of the earth or the ground that you get," explains Morales.

Storm surge can even impact areas as far inland as Moncks Corner. Which is why if you live along a tidal basin, you need to pay very close attention to the storm surge forecast.

We hear the two words: inundation and storm surge, a lot when it comes to tropical systems. Often it seems like they are interchangeable. But its important to understand the difference between storm surge and what the inundation forecast means.

"Storm surge in the phenomena of water being pushed onto the shore by the winds. The inundation is just above ground. What does that [storm surge] produce," explains Morales.

"Now we can't tell you above every piece of ground, wherever you are. So it'll be very generalized," he says. For instance you'll hear a forecast of 2-4 feet or 4-6 feet for tidal areas.

"The trigger is once we think there's gonna be a little more than 3 feet of water above the ground, that triggers what we consider life threatening and damaging inundation or storm surge values. If that goes to a warning, usually that will be triggered say within 36 hours of the event occurring," Morales says of the storm surge watches and warnings.

Why is storm surge so important to understand? We all know that hurricanes can be deadly. But did you know, storm surge accounts for roughly half of all hurricane related deaths.

"Its one thing to stand in a puddle and say its 2 feet of water and its up to your knees. And you're just standing in a puddle. But imagine standing in that puddle and the water's moving at a high velocity. Like when you're at the beach and the surf's going back and forth and you feel it tugging you. So there's different areas where it becomes more dangerous. So in the what we call high velocity zones, say near the beaches is where that water's coming up. It's not only coming up, but it's coming up with a force and with a motion and a current. Very dangerous. Very destructive," warns Morales.

"Whereas, may be in the back behind the island, and in the marshes and up the rivers. Maybe it's not coming up as much with a force but its coming up, still damaging, still potentially life threatening if you don't swim," Morales says.

As Hurricane Florence approaches the coast of the Carolinas, storm surge watches and warnings continue. Make sure to stay up to date on the latest forecast at Hurricane Central.


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