Protecting New YorkShoring up Long Island’s natural shore defenses against future storms

Inlet cut through New York's Fire Island by hurricane Sandy // Source: usgs.gov

A rapid response science team from the University of Texas at Austin’s Institute for Geophysics is helping map the impact of Hurricane Sandy on the beach and barrier systems off the south shore of Long Island.

You may follow this rapid response field blog with live updates from the ship. The team is collaborating this month with researchers from Stony Brook University, Adelphi University, the City University of New York, and other institutions from the New York metro area to assess the health of the offshore barrier system which protects the New York Harbor and southwestern Long Island region against damage from future storms.

An Institute of Geophysics release reports that the team is conducting marine geophysical surveys of the seafloor and shallow subsurface to map the sedimentary impact of the hurricane on the beach and barrier systems of selected bay, inlet, and nearshore areas of the south shore of Long Island.

Sand and other coarse-grained sediments are vital to the naturally occurring barrier systems which dissipate storm surges, protect coastal residences, and shelter biologically diverse estuaries and ecosystems.

Results of the survey will help environmental engineers plan future efforts to restore sand to the barrier system in the wake of Sandy’s devastating, long-term damage.

The release notes that the Texas team has experience with similar geophysical surveys of nearshore sediments after Hurricane Ike, the costliest storm in Texas history, which made landfall near Galveston on 13 September 2008. Furthermore, the team has a collaborative history studying the continental shelf off New Jersey and New York.

“As with Ike, we will be looking at where the sand went as a result of the storm,” said John Goff, a principal investigator for the project at The University of Texas at Austin. “With Ike, we found that the ebb of the storm surge moved a lot of beach barrier sand off shore.”

Using a compressed high-intensity radar pulse (CHIRP) and an even higher frequency seafloor mapping system supplied by Stony Brook University, the scientists will use multiple research vessels to profile the seafloor and upper sediment layers of the ocean bottom. Similar research after Ike found an “event layer” of sand that the storm deposited over a wide area of ocean floor.

The danger with any storm of Sandy’s magnitude, added co-principal investigator Jamie Austin, is that “a lot of the sand gets pushed too far off shore, beyond the ability of normal processes to reincorporate it into the system that nourishes the barrier naturally.”

When that happens, the only way to restore the sedimentary system may be to recover sand from new, offshore locations manually and deposit it where it was before the storm.

“The cost to society for these restoration projects can be huge,” said Austin, “so we need to get the sediment budget details absolutely right.”

Colleagues from Adelphi University and the City University of New York also expect to take sediment samples during these at-sea investigations to assess sediment budgets further.

“Our study of the sediments will allow us to better understand how the surge impacted the fragile estuarine system,” said Beth Christensen, team leader from Adelphi University.

The U.S. Geological Survey is providing crucial seafloor mapping data for before-and-after comparisons.

Assessment of the seafloor is already under way. The geophysical survey is taking place 7-28 January. Results will be prepared for distribution later this year.

The rapid response geophysical survey is being funded by the Jackson School of Geosciences at the University of Texas at Austin. The Jackson School has funded similar rapid response geoscience surveys following several previous natural disasters, including the Solomon Islands earthquake/tsunami (2007), Hurricane Ike (2008), and the Haiti earthquake (2010)