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Aug 26, 2011 3:00 PMPublication: The Southampton Press

Storm Surge Now Expected To Hit At High Tide

Aug 30, 2011 1:20 PM

Forecasters now expect the accelerating Hurricane Irene to approach the Long Island coastline sometime early on Sunday morning—a dangerous shift in timing, because the storm’s destructive surge could now push ashore near the time of the morning high tide, exacerbating the effect.

Storm surge, the mound of sea water that is pushed ahead of the hurricane, can be expected to come ashore one to two hours before the actual center of the storm passes the area—now believed to be sometime between 7 and 10 a.m. on Sunday. High tide at Shinneock Inlet on Sunday morning is at about 7 a.m.

The storm surge could elevate sea levels as much as 5 feet above normal, according to latest official predictions. Adding to the effects of the storm surge is Sunday’s new moon, which raises tides, and the fact that the moon also is at its perigee this month, which can exagerate tide levels further.

Irene is expected to still be a Category 1 hurricane when its center comes ashore on Long Island. The center of the storm is now expected to make landfall somewhere near the Nassau-Suffolk border, according to NOAA computer models. The strongest winds and the highest surge from the storm will be to the east of the center of the storm, in central and eastern Suffolk County.

“This is a huge storm—the pure size of it means it’s going to gather a lot of water in front of it,” said Stephen P. Leatherman, Ph.D., director of the Labratory for Coastal Research at Florida International University, a research group that examines the coastal flooding effects of storms. “It’s moving very slowly right now, and if it comes up the coast slowly, you will get a bigger surge. And you’re coming up on spring tides—so the surge will be critical relative to the tidal cycle. If it comes at low tide, it will effectively cancel out the surge.”

As of midday on Saturday, the National Oceanographic and Atmospheric Administration and the U.S. Army Corps of Engineers were predicting a total sea level height—combining the expected storm surge and the height of the tides—of about 5 feet above normal.

“This is not going to be 1938,” Dr. Leatherman said of the infamous, deadly hurricane of that year, nicknamed the “Long Island Express” for the speed with which it bore down on the region, killing more than 500 people. “That was a big Category 3 storm with 10- to 15-foot storm surge. This is not what we’re looking at with Irene.”

With storm surges only predicted to be in the middle single-digits, Dr. Leatherman said he doesn’t expect evacuations of anything but the lowest-lying areas and the barrier islands to be necessary.

Storm surge can pose the greatest threat to beachfront properties, as waves riding the top of the surge of water pound into, and sometimes over, the sand beaches and protective dunes behind them, flooding under or through the foundations of homes. Structures mounted on pilings are typically sound, unless the full brunt of storm waves impact the structure directly.

The timing of Irene’s arrival has Long Island’s beaches in the best condition they can be for absorbing the force of the hurricane’s waves and storm surge. Summer’s southerly winds tend to pile sand onto the south shores, and with gentle winds for most of the summer and no passing storms to cause erosion, the South Fork’s beaches are generally in good shape, according to experts—with several very important exceptions.

“Overall, our beaches are in pretty good shape,” said coastal geologist Aram Terchunian, whose Westhampton Beach company, First Coastal, manages dune rebuilding and coastal protection for dozens of oceanfront property owners in Southampton and East Hampton, including Southampton Town. “There are some problematic spots, though.”

Mr. Terchunian said a handful of areas of the beachfront are vulnerable to either property damage from Irene’s waves or overwash of the dunes, and possibly even breaches of the barrier beach in two places.

The stretch of Dune Road in East Quogue surrounding Mermaid Lane and Sandbar Beach is a very low region, where the underlying hardpan beneath the sand and dunes dips to just barely above sea level, from its usual 10 to 15 feet. The area has also suffered from accelerated erosion in recent decades, narrowing the beachhead and nearly erasing the once-broad natural dunes. Last winter, Southampton Town contractors used a stockpile of sand dredged from the ocean floor in 2009 to rebuild the primary dune near Sandbar Beach. But in front of some private properties there is effectively no dune, Mr. Terchunian said. It is in this area, he said, that an actual breach of the barrier islands is most likely.

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Excellent and detailed reporting Mr. Wright.
By PBR (4945), Southampton on Aug 26, 11 7:41 PM
Not so much, at least as far as the first paragraph is concerned. Maybe those very close to the water must fear the surge but everybody must deal with the wind and the damage it does to trees, power lines, and structures. I'd bet that the insurance companies would take issue with that lead.

How about backing the claim with some statistics from past storms?
By VOS (1224), WHB on Aug 27, 11 12:50 AM
Unless I'm mistaken, we've lost more beach in the last thirty years, than in the last one hundred prior.

Of course, I could be wrong...
By Mr. Z (11550), North Sea on Aug 27, 11 2:39 AM
Very good explanation Aram!
By Summer Resident (245), Manhattan on Aug 27, 11 10:21 AM
This comment has been removed because it is a duplicate, off-topic or contains inappropriate content.
By G (338), Southampton on Aug 27, 11 4:17 PM
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