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Spotlight on Sandy

Hurricane Sandy Impacts Did Not Contribute to Subsequent Storm Flooding

Study looks at Great South Bay and Barnegat Bay

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Flooding in coastal areas bordering Great South Bay, New York, and Barnegat Bay, New Jersey, caused by winter storms that occurred after Hurricane Sandy was not influenced by changes Sandy made to barrier islands or other bay features, according to a new U.S. Geological Survey (USGS) study.

Oblique aerial photographs of Pelican Island and Fire Island, New York
Above: Oblique aerial photographs of Pelican Island (arrow points to a fishing shack on the island) and Fire Island, New York, looking northwest toward Great South Bay. This location is within Fire Island National Seashore near Old Inlet—a narrow part of the island that has been breached in previous large storms. The island breached during Hurricane Sandy, creating a new inlet. The new study shows that such shoreline changes did not affect flooding caused by post-Sandy storms. USGS photo pair from http://coastal.er.usgs.gov/hurricanes/sandy/photo-comparisons/. [larger version]

USGS scientists studying Barnegat Bay and Great South Bay looked at data from November 2012 to October 2013, when winter storms brought water levels in these bays to among the 20 highest storm water levels reached from October 2007 to October 2013.

“The frequent and extreme high-water levels caused by storms in these two bays in the months after Hurricane Sandy led to perceptions that the mainland was more vulnerable to flooding,” said USGS oceanographer and coauthor of the study Neil Ganju. “This study shows that changes to bay features caused by Hurricane Sandy did not influence these post-Sandy storm water levels.”

Hurricane Sandy caused extreme floods along portions of the northeast coast of the United States and cut new inlets across barrier islands in New Jersey and New York. Scientists investigated whether Hurricane Sandy had in some way reduced the protection provided by the barrier islands and the bays, leaving the mainland more vulnerable to flooding.

The study compared water-level measurements made at stations within Great South Bay and Barnegat Bay to ocean water levels before and after Hurricane Sandy. Both are back-barrier bays—bodies of water behind barrier islands and connected to the ocean through one or more inlets.

“Changes in water levels in the back-barrier bays are primarily caused by ocean water levels driving water into or out of the bays through inlets,” said USGS oceanographer and lead author of the study Alfredo Aretxabaleta. “The study showed that most of the ocean water-level fluctuations caused by storms make their way into the bays, while only a fraction of tidal fluctuations do.”

Above: Map of Middle Atlantic Bight showing locations of water-level stations at Mantoloking, New Jersey (MAN), and Lindenhurst, New York (LIN), in blue (in estuaries behind barrier islands) and at Sandy Hook, New Jersey (SH), in red (used as proxy for offshore water level). The Battery in New York (NYB) is also shown in red. Inset maps show (left) Barnegat Bay and (right) Great South Bay, and open squares show the location of breaches at Mantoloking, New Jersey, and Old Inlet, New York, that occurred during Hurricane Sandy. The letter B marks the location of pressure measurements on the inner shelf (1999–2000). (Figure 1 from “Water level response in back-barrier bays unchanged following Hurricane Sandy,” Geophysical Research Letters.) [larger version]

The results showed that alterations to the barrier, inlet, and bay systems caused by Hurricane Sandy did not influence the high water levels caused by storms from November 2012 to October 2013. None of these post-Sandy storms opened new inlets or caused overtopping of the protective dunes and barrier beach systems. Both before and after Sandy, about 80 percent of storm surge—a temporary rise in water level caused by an offshore storm’s winds or low pressure—made its way into the back-barrier bays, whereas only about 20 percent of the tidal fluctuations do. This suggests that whether the same storm occurred before or after Hurricane Sandy, the water level in the bays would be the same.

“While the existing barrier-island and inlet system shields the mainland to a great extent from the daily tides, most of the storm surge, and all long-term changes in water level, such as those resulting from sea-level rise, reach the mainland” said USGS oceanographer and coauthor Bradford Butman. “These results will inform coastal communities and planners how water levels in back-barrier bays respond to ocean fluctuations.”

Several studies related to Hurricane Sandy recovery, restoration, and rebuilding efforts, many of which are funded by Disaster Relief Appropriations Act 2013, are currently underway.

Water-level station (tide gage) at Mantoloking, New Jersey
Above: USGS water-level station (tide gage) at Mantoloking, New Jersey. [larger version]

“The USGS is committed to providing the science foundation for Federal, State, and local authorities to build more resilient communities,” said John Haines, coordinator of the USGS Coastal and Marine Geology Program. “This is one of many studies the USGS is doing to understand the effects of Hurricane Sandy and to evaluate the vulnerability of the coast and its communities to future storms.”

Results of the study have been published in a paper in the journal Geophysical Research Letters. The full citation for the new paper is:

Aretxabaleta, Alfredo L., Butman, Bradford, and Ganju, Neil K., 2014, Water level response in back-barrier bays unchanged following Hurricane Sandy: Geophysical Research Letters, v. 41, no. 9, p. 3163–3171, doi:10.1002/2014GL059957.

Related Sound Waves Stories
Hurricane Sandy Disrupts USGS Study of the Barnegat Bay-Little Egg Harbor Estuary in New Jersey
Jan. / Feb. 2013
USGS Research to Support Hurricane Sandy Rebuilding Gets Boost from Supplemental Funds
Nov. / Dec. 2013
USGS Scientists Predict, Measure Sandy's Impacts on the Coastal Landscape
Nov. / Dec. 2012

Related Websites
Water level response in back-barrier bays unchanged following Hurricane Sandy
Geophysical Research Letters
USGS 01408168 Barnegat Bay at Mantoloking NJ
Hurricane Sandy: Pre- and Post-Storm Photo Comparisons

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in this issue:

cover story:
Earthquake, Landslide, and Tsunami Hazards in the Caribbean

Through the Eyes of a Polar Bear—First "Point of View" Video

Spotlight on Sandy
Hurricane Sandy Impacts Did Not Contribute to Subsequent Storm Flooding

New Personnel Study Estuarine Response to Storms

Summer Hires Assist Studies of Coastal Sediment Transport

Tracking Oil—USGS Tools and Analysis Inform Oil-Spill Response

Help Identify Coastal Hazards with Aerial Photographs on "iCoast" Website

Coral Reefs Provide Critical Protection to Coastal Inhabitants

New Postdoctoral Researchers at USGS in Woods Hole, Massachusetts

Summer Intern at USGS in Woods Hole, Massachusetts

Publications New USGS Coastal and Marine Geology Web Pages

Facilitating Identification of Coastal and Undersea Features

May / June Publications

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