Hurricane Sandy and Fire Island

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Protective Dunes Breached by Waves to Create an Overwash Fan. Image by J. Gibson

Protective Dunes Breached by Waves to Create an Overwash Fan. Image by J. Gibson

What Happened During Sandy on Fire Island?

As Cheryl Hapke, a USGS research geologist and lead author of the after-study pointed out, “Sandy profoundly altered the shape and position of the barrier island, shifting it landward and redistributing large amounts of sand.

Essentially, three things occurred:

  1. The island was breached in three locations;
  2. The beaches and dunes of the island were severely eroded and enormous volumes of sand carried from the beach and over 50 % of the protective dunes to the central portion of the island, forming large overwash deposits; and
  3. There was widespread damage and destruction of coastal infrastructure, including private residences as flood waters rushed through.

Even before the storm hit a USGS pre-storm field team went to Fire Island and took before pictures. There were also pre-storm photos acquired during a baseline survey on May 21, 2009 and post-storm photos were acquired. On November 4-6, 2012, after the storm hit, the field team took specific oblique aerial photographs of the resultant damage.

Before and After Oblique Aerial Photographs of Storm Damage on Fire Island. Image by USGS

Before and After Oblique Aerial Photographs of Storm Damage on Fire Island. Image by USGS

Measurement and analysis of the damage followed in the form of profiles and 3D Lidar topography imaging, a remote sensing technology that measures distances by illuminating a target with a laser and analyzing the reflected light.

Lidar Images of Pre and Post Storm Elevations on Fire Island. Image by USGS.

Lidar Images of Pre and Post Storm Elevations on Fire Island. Image by USGS.

While there was some recovery in the early spring when 18 percent of the pre-Sandy beach volume returned, during the preceding winter months, Fire Island’s shoreline position shifted up to 57.5 meters (189 feet) inland.

Hurricane Sandy Beach Damage: Implications

Obviously, by eroding beaches and dunes, elevated water levels and waves during tropical storms can lead to dramatic coastal changes.

The USGS uses a storm-impact scale to predict the probability of coastal change. The result is three coastal change regimes:

  1. Collision- when waves attack the base of dunes and cause dune-front erosion;
  2. Overwash- under higher surge or wave runup conditions, waves can overtop dunes
  3. Inundation- storm surge and wave setup exceeds the elevation of the primary dune or beach berm (low, narrow islands may breach).

The probabilities of each of the above were assessed by calculating coastal probabilities. The parameters included were:

  • Modeled total water levels- tide, surge, wave runup
  • Dune or berm elevations
The Hazard Zones on Fire Island Based on Probability Models. Image by USGS

The Hazard Zones on Fire Island Based on Probability Models. Image by USGS

The probabilities were mapped with white representing a low probability (0-10 %) and dark red a high probability (90-100%).  High probabilities leave the impacted areas more vulnerable to future storms.

Fire Island: Vulnerable and Ever-Changing

So, this island, founded as a whaling center in the 18th century and now a destination for artists, actors and musicians “puts the fear of god in Fire Islanders whenever a storm approaches. With Hurricane Sandy, for many, our worst fears were realized,” says Jane L. Rosen.

And so it should. Fire Island’s shores and elevations constantly shift in a sort of equilibrium among mighty natural forces. The beaches are destroyed by the power of erosion – as Alida Thorpe’s photos attest- while, on the other hand, the island is being built up by the deposits carried to the ocean-front by longshore drift. The USGS is limited to providing scientific advice.

Resources

Davis Jr., Richard A.; Fitzgerald, Duncan M. Beaches and Coasts. (2004). Wiley-Blackwell. United Kingdom.

Hapk, Cheryl J. Coastal Change from Hurricane Sandy and the 2012–13 Winter Storm Season: Fire Island, New York. (2013). USGS. Accessed August 29, 2013.

Mandia, Scott A. Geologic Impact of the 1938 Hurricane. Suffolk County Community College. Accessed August 29, 2013.

Moore, W.G. A Dictionary of Geography. (1963). Penguin Reference Books.

Morelock. Barrier Systems, Lagoons, Tidal Inlets. UPRM. Accessed August 29, 2013. 

NOAA Coastal Services. Barrier Islands: Formation and Evolution. NOAA. Accessed August 29, 2013. 

Rosen, Jane L. To Fire Island With Love. (2021). Huffington Post. Accessed August 29, 2013. 

Smith, William K. et al. Coastal Barrier Islands: Coupling Anthropogenic Stability with Ecosystem Sustainability. (2006). Coastal Barrier Islands – Wake Forest University. Accessed August 29, 2013.

St. Petersburg Coastal and Marine Science Center. Coastal Change Hazards: Hurricanes and Extreme Storms: Fire Island Comparison Photos. (2013). USGS. Accessed August 29, 2013.

St. Petersburg Coastal and Marine Science Center. Coastal Change Hazards: Hurricanes and Extreme Storms: Fire Island Field Observations and Measurements of Coastal Change. (2013). USGS. Accessed August 29, 2013.

St. Petersburg Coastal and Marine Science Center. Vulnerability Image of Fire Island. (2013). USGS. Accessed August 29, 2013.

Thorpe, Alida. Fire Island, Long island, NY. Alida’s Photos. Accessed August 29, 2013.

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