Calculating impacts to sediment transport critical to restoration efforts
By Summit Voice
FRISCO — Along with the devastation and human suffering it caused, Hurricane Sandy may have raised awareness about the importance of natural coastal defenses to a whole new level. With climate models predicting significant sea level rise and increased precipitation, those natural barriers may become the first — and most important — line of protection against growing storm surges and coastal inundation.
In the wake of Sandy, a rapid response science team from the University of Texas at Austin’s Institute for Geophysics will help map the impact of Hurricane Sandy on the beach and barrier systems off the south shore of Long Island.
The team will collaborate 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 that protects the New York Harbor and southwestern Long Island region against damage from future storms.
Sand and other coarse-grained sediments are vital to the naturally occurring barrier systems that dissipate storm surges, protect coastal residences and shelter biologically diverse estuaries and ecosystems. To try and understand the impact of Sandy, the researchers will conduct marine geophysical surveys of the seafloor and shallow subsurface.
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 Texas team has unique experience with similar geophysical surveys of nearshore sediments after Hurricane Ike, the costliest storm in Texas history, which made landfall near Galveston on Sept. 13, 2008. Furthermore, the team has a rich 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 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.
“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,” said researcher Jamie Austin, describing the impacts of a megastorm like Sandy. 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 will take place Jan. 7-28. 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).
The rapid response field blog will post live updates from the ship.