December 12, 2013
Long Island Barrier Still Intact After Hurricane Sandy
Alan McStravick for redOrbit.com – Your Universe Online
On August 29 of last year, Hurricane Sandy, noted as the most powerful hurricane of the 2012 season, made landfall in southern New Jersey, wreaking havoc across much of the eastern seaboard. Residents of the area faced property destruction and crisis situations like flooding and massive, long-term power outages just in time for a particularly frigid autumn. Now more than a year out from the superstorm, a University of Texas led research team has good news for the region.
In a presentation at this week’s autumn meeting of the American Geophysical Union in San Francisco, the research team reported that Sandy, destructive as she was, was unable to seriously damage the offshore barrier system that controls erosion on Long Island. The good news was mixed with ongoing caveats regarding potential future sea level rise, the pollution of back-barrier estuaries and closer shore damage.
The team used pre-storm survey data compared to post-storm data to arrive at their conclusion. The post-Sandy data was collected as part of a rapid response coordinated among The University of Texas at Austin’s Institute for Geophysics, Adelphi University, Stony Brook University and other regionally-affected institutions.
The post-storm rapid response included marine geophysical surveys of the seafloor and shallow subsurface. These surveys mapped out the sedimentary impact of Hurricane Sandy on the beach and barrier systems of the selected bays, inlets and near-shore areas centered around the south shore of Long Island.
[ Watch the Video: Hurricane Sandy & Rapid Response Science ]
"The shape of the bedforms that make up the barrier system did not change a whole lot," said co-Principal Investigator (PI) John Goff of the Institute for Geophysics in a statement. "Where we might have expected to see significant erosion based on long-term history, not a lot happened — nothing that ate into the shoreface."
Stony Brook University, for their part, provided the team with a CHIRP (compressed high-intensity radar pulse) sonar system as well as a high frequency seafloor mapping system. The team, exploring an area approximately one mile offshore, mapped nearly six square miles in total.
"The sand largely took the blow," added co-PI Jamie Austin of the Institute for Geophysics. "Like a good barricade, the barrier system absorbed the significant blow, but held."
The Texas-based team has previous experience in this sort of mapping endeavor. In 2008, with Hurricane Ike, their results were not as rosy. That storm, they found, disrupted the natural sedimentary barrier outside the Galveston area, potentially accelerating future erosion of the Texas shore.
Long Island, it turns out, is not Galveston. This is because Long Island has a greater abundance of sand in its overall system. While Hurricane Sandy effectively churned up much of this sand and moved bedforms, the scientists believe the overall quantity of sand in the offshore region helped to maintain the natural barriers shape and integrity.
As mentioned previously, however, the report was not all good news for Long Island. They report the storm brought in new pollutants to the waters just off the Long Island shoreline. Chief among these new pollutants was the detection of heavy metals in a layer of mud deposited offshore. Researcher Beth Christensen of Adelphi University traced their lineage to muds from the South Shore Estuary Reserve. This estuary system has been subjected to pollution from both industry and human habitation over the years.
Less than a year after the storm, the heavy metal concentrations had been naturally dispersed making the toxin level low enough so as not to be an immediate concern, said Christensen.
"But if we continue to see more events like Sandy, we'll see the introduction of more and more muds from the estuary," said Christensen, "adding additional toxins to an already stressed system."
Also of concern is the increase in sea level rise, which is expected to place more pressure on the barrier system. As sea level rises, the onshore impacts from another Sandy-esque storm will go up, states Goff.
"In the long-term, if sea level gets high enough, the barrier system has no choice but to retreat and move landwards," said Goff, exposing the shoreline to increased erosion. "But at least for the present, there's no evidence of that being imminent."
This research represents the sixth rapid response science mission funded by the Jackson School of Geosciences at The University of Texas at Austin. These missions are key in getting the research teams to the affected areas as quickly as possible after a natural disaster. The speed of deployment allows them to quickly measure the vanishing traces of hurricanes, earthquakes, tsunamis and other disasters.
"The faster we get out into the field to measure Earth's response to naturally destructive events, the better we can relate data to the disasters," said Austin.