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.
“The ingredients for a breach are diminished height, diminished depth, deep water,” Mr. Terchunian explained on Friday. “A 6-foot surge and a wave set on top of that would overwash that area. The dune will get flattened out, the water will flow across the land, and the bay will fill up and fill up. Then when the hurricane passes, that water will try to get back out. The breach would really be caused by the return.”
The danger in the Mermaid Lane area is exacerbated by a deep channel dug by fishermen in the 1880s so that boats could approach the barrier island to haul fish back to the mainland, in the days before bridges spanned the bays. The trench they dug runs right up to the edge of Dune Road and would provide a perfect ready-made channel for a breach to wash through, Mr. Terchunian said.
The beach that separates the ocean from Wainscott Pond on the border of Southampton and East Hampton towns is in a similar predicament. The dune in the area is effectively non-existent, and storms this past winter and spring have already washed sand into the shrublands that typically is found landward of the dunes in a healthy beach system. Mr. Terchunian said it would not take a particularly heavy storm surge and wave action to flood across the beach into the pond, which is surrounded primarily by farmlands.
With very narrow dunes and an extremely low beachhead, downtown Montauk is also among the most vulnerable areas from storm surge.
“The beach there is very narrow and very, very shallow,” Mr. Terchunian said of Montauk’s beach. |There’s only a couple feet of sand on top of hard pan in much of that area, nothing to slow waves down.”
In most of eastern Southampton and East Hampton towns, however, the beaches and dune systems are in perhaps better shape than in recent years. The only other main areas where storm surge could cause significant damage or wash beyond the dune lines are at some of the western Southampton road ends, at Jobs Lane Beach in Bridgehampton—where nor’easters pushed the sea over the dunes in 1993 and 1997—and in Southampton Village, at the Dune Church.
The St. Andrews Church, known as Dune Church because it is nestled among the towering sand dunes just yards from the breaking ocean, has been the subject of significant concern for decades, as its property is one of only a very few in a 5-mile stretch of beach that does not have stout concrete or steel seawall protecting it from the onrush of a storm-driven sea. The church’s trustees have applied to the Southampton Town Trustees to be allowed to install a seawall or rock revetment to close the gap between the hardened protective walls on either side if it. Without a wall of its own, the church becomes the lone weak link where waves deflected off surrounding sea walls would be projected landward.
North-facing properties on Block Island Sound and the bays between the forks also face significant threats from storm surge as the pulse of water floods into the Peconic Estuary and Long Island Sound. The current forecasted track of Irene would take it to the west of the South Fork, a break for north-facing shores, because winds would remain from the south throughout the duration of the storm rather than switching to the north as the storm passed, as would happen if it passed to the east of the region. In particular, the shoreline along Culloden, west of the entrance to Montauk Harbor, has experienced extreme erosion this year and remains a very precarious situation.
“If we get a big storm surge in there—if the storm goes to the east, and a wind that switches around to the north—that is going to be extraordinarily unpleasant,” Mr. Terchunian said.
