In bad hurricane, we get SLOSHedComputer model predicts how high water could get in your neighborhood By Tony Bartelme (Contact)
The Post and Courier
Wednesday, March 5, 2008
A Category 2 hurricane would turn much of downtown Charleston and Mount Pleasant into a soggy flooded mess, according to special computer-generated maps used by emergency officials. A Category 3 storm surge, meanwhile, would flood all but a few patches of higher ground east of the Cooper and turn Savannah Highway into Savannah Causeway. And a Category 5? Break out the snorkels. Wet and WetterView the map of which areas would flood in different hurricane-intensity scenarios. The National Hurricane Center generates these storm surge maps using the little-known but well-named computer model called SLOSH, which stands for Sea, Lake and Overland Surges from Hurricanes. Government agencies then use the SLOSH data to decide which areas to evacuate and when. A poster of an interactive version of the model is being displayed at the federal Interdepartmental Hurricane Conference in Charleston this week. The version allows users to single out individual landmarks and get a vertical look at how deep the water would be at that landmark. The model is in development. Hurricanes are notoriously fickle and can arrive in an infinite number of directions, speeds and tidal levels. This makes predictions of their impacts just as tricky. Still, a SLOSH map obtained by The Post and Courier and generated for a hypothetical direct hit on Charleston provides an intriguing snapshot of how the city might fare in certain hurricane scenarios. It's also a bit of a reality check for Hurricane Hugo veterans. When Hugo spun into South Carolina, the storm's sustained winds in downtown Charleston were 87 mph with a 108-mph gust, and a 10.4-foot storm surge in the harbor. By most measures, Hugo put downtown Charleston in Category 1 and 2 conditions. It was a different story in the Francis Marion National Forest, 30 miles north of downtown. There, winds were at Category 4 levels — 130 mph and higher. The storm surge in McClellanville hit 19 feet, so high that shelter seekers in Lincoln High School nearly drowned. 
Partly because of Hugo and the Lincoln High School incident, the National Hurricane Center created SLOSH to simulate storm surges for different hurricane intensities and directions, said Doug Marcy, a scientist at National Oceanic Atmospheric Administration's Coastal Services Center in Charleston. The newspaper obtained SLOSH calculations for a hurricane with an eye coming in south of Kiawah Island. This reflects more of a worst-case scenario for the city because surges are higher in a storm's northeastern quadrant. In a Category 1 storm, a surge of 7 to 10 feet would have a relatively minor effect on the area, the calculations show. Floodwaters would fill the area's marshes and low-lying areas on the peninsula and the sea islands. But parts of the Isle of Palms and other barrier islands would still remain above water. That changes dramatically in a Category 2 storm with a surge of 12 feet. In this scenario, the barrier islands all but disappear and most of downtown Charleston and James Island flood. In Mount Pleasant, the only dry ground would be along Johnnie Dodds Boulevard, which is built on an ancient sand ridge. In this Category 2 scenario, floodwaters would begin to march into North Charleston toward Park Circle. And for the first time since it was developed, most of Daniel Island would temporarily lose its island status and become a seabed. In Category 3 surge, most of West Ashley goes under water, along with a few specks of downtown Charleston. In a Category 4 scenario, a 15- to 20-foot surge inundates much of Johns Island, while floodwaters on the Charleston Neck are neck deep. A Category 5 scenario? Some parts of Charleston would be under more water than the low areas of New Orleans after Katrina. Forecasters caution that SLOSH maps aren't perfect. They say the calculations have a 20 percent margin of error, and they also don't take into account tides, which could add or subtract a few feet of surge depending on a hurricane's timing. Still, they offer an important lesson: For much of the immediate Charleston metro area, Hugo wasn't a worst-case scenario. "Hugo was an awful storm but had it moved south and come in over Kiawah, we could have had 18 to 20 feet of storm surge, instead of the 10 feet we got on its backside," Marcy said. Reach Tony Bartelme at tbartelme@postandcourier.com or 937-5554. |
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Comments
This article has 16 comment(s)
Posted by jimisle on March 5, 2008 at 8:29 a.m. (Suggest removal)
This isn't news. Tell us something we don't know.
Posted by wpc3iop on March 5, 2008 at 8:41 a.m. (Suggest removal)
It's the price we pay for living in paradise...
Posted by desspec on March 5, 2008 at 8:55 a.m. (Suggest removal)
Why not construct a map for the newbies that show where the water rose to in Hugo? That would be more accurate than a "what-if" guess of the future..
Posted by ColdBeer on March 5, 2008 at 9:08 a.m. (Suggest removal)
I wonder if they could spend tax payer money and make a map that lets us know it gets hotter when the sun shines....
Posted by Paul on March 5, 2008 at 9:15 a.m. (Suggest removal)
Are these people associated with the ones who said we would have a massive storm yesterday? On James Island all we had was a few sprinkles and a nice breeze ...
Posted by PJM on March 5, 2008 at 9:22 a.m. (Suggest removal)
Preparation for a hurricane? Absolutely. Another hyped-up "scientific forecast" of a dreadful hurrincane season starting in June? CAN IT!!
Posted by blah_blah_blah on March 5, 2008 at 9:28 a.m. (Suggest removal)
*This just in*
People living by volcanoes can expect lava during an eruption.
People living in Kansas can expect tornadoes.
People living in New England can expect cold winters.
People in North Charleston can expect gun shots at night.
Posted by MichaelsAdvocate on March 5, 2008 at 9:58 a.m. (Suggest removal)
Blah, Is that a threat or a promise? Kind of reckless, there.
Posted by ColdBeer on March 5, 2008 at 10:01 a.m. (Suggest removal)
P&C, instead of printing an article telling us what we already know, why not do some investigative reporting and find out how well prepared the low country governments are in the event we do end up with a Cat 4 or 5 heading our way. A lot of lessons were learned during Katrina. Does Joe Riley have a plan in place to evacuate all of the people in Charleston that do not own transportation? Do all of the areas old folks homes have evacuation plans in place? Has the city mandated those plans? The same questions for North Charleston and the remaining low country areas.
Telling me that water makes things wet is not news. Letting us know that our local government is really prepared, or is not prepared IS news.
Posted by ssturmsc on March 5, 2008 at 10:07 a.m. (Suggest removal)
Here's another idea. How about all of you commenters quit being ass holes.
Posted by anon on March 5, 2008 at 10:33 a.m. (Suggest removal)
This is why I bought in Summerville.
Posted by swcjr on March 5, 2008 at 10:39 a.m. (Suggest removal)
we need a another one, it is good for the building industry
Posted by don0427 on March 5, 2008 at 12:14 p.m. (Suggest removal)
I see it's time again to start scaring people.
Every year since Hugo the local "bad weather mongers" start puffing their feathers (Chicken Little-like), wringing their hands with the "oh whoa is us" thing and then tell us how much they're going to do to protect us. How. By reading what's written on their screens as though we're all incapable of reading.
If it scares you get out of town. But do it early because the Big 3 will direct you all to I26 and like lemmings you'll go and sit in traffic like last time leaving a multitude of routes completely open (I know. I delivered 18 loads of gasoline that day in the tri-county area with absolutely no delays).
The local TV channels prey on your fears to booswt their ratings. Period.
Posted by jimisle on March 5, 2008 at 2:32 p.m. (Suggest removal)
"P&C, instead of printing an article telling us what we already know, why not do some investigative reporting and find out how well prepared the low country governments are in the event we do end up with a Cat 4 or 5 heading our way."
ColdBeer, I have to agree. It might be compelling to see a story on any studies being done regarding flood prevention methods; such as what they've done in the Netherlands. You don't even have to go as far as Cat 4-5. Let's talk about what flood control is already like for relatively minor soakings that cause street flooding. Of course, none of this has anything to do with the probability of a hurricane, about which we can do little. Proactively, however, you're right: what plans are in place for mass evacuations, particularly the poor?
Posted by AHLeland on March 5, 2008 at 4:34 p.m. (Suggest removal)
Say what you will about the fear mongering but having been upstairs in our house in McClellanville watching as 8-9 feet of water filled the downstairs, I can tell you this is a real issue. People need to really grasp what a storm surge is. That should be the focus of the National Huricane Center. I think there is some misconception that a storm surge is a flood. It is not the same thing.
Posted by ticket3477 on March 5, 2008 at 4:59 p.m. (Suggest removal)
it gets hotter where the sun shines? I need that map so I can move about charleston accordingly.