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St. Petersburg Coastal and Marine Science Center > National Assessment of Storm-Induced Coastal Change Hazards > Hurricane Sandy

National Assessment of Storm-Induced Coastal Change Hazards

Hurricane Sandy

Pre-Storm and Post-Storm 3D Lidar Topography: Virginia

The USGS conducted an airborne lidar survey of the topography of Virginia in November 2012, after Hurricane Sandy passed by to the East. In November 2009, the USGS conducted a similar survey after Ida (also known as "Nor'Ida") impacted the Northeast United States. Comparing these two surveys reveals the nature, magnitude, and spatial variability of hurricane-induced coastal changes, such as beach erosion, overwash deposition, and island breaching. At least one other large storm occurred in the period between the two lidar surveys, so these data document the cumulative impacts of these events.

Location Map
Virginia Index Map. Click on the yellow highlighted numbers to see maps of that location. The numbers correspond to the pre- and post-storm photograph comparisons. In the inset map, the green line is Hurricane Sandy's track and the red line indicates the shoreline where post-storm airborne lidar data were collected post Hurricane Sandy.

Below are pre-storm elevation maps, post-storm elevation maps, and elevation difference maps at each highlighted location. In the pre- and post-storm elevation maps, orange and red colors indicate higher elevations while yellow and green colors indicate lower elevations. In the elevation difference maps, red colors indicate erosion such as shoreline retreat, and blue-green colors indicate accretion, such as overwash deposits where waves and surge have moved sand landward. The location numbers correspond to the photo pair comparisons. The maps are oriented with the Atlantic Ocean on the bottom.

Location 1

Pre-Storm Elevation
pre-storm elevation for Assateague Island, Virginia

    Post-Storm Elevation
post-storm elevation for Assateague Island, Virginia

Elevation Difference
elevation difference for Assateague Island, Virginia
 
Location 1: Assateague Island, VA.
Along this stretch of the island, overwash deposits from earlier storms are evident in the pre-storm map. The pre-storm lidar was obtained after Nor'Ida (2009) but prior to Hurricane Irene (2011) so the change in the post-storm map incorporates both Irene and Sandy. (Note that in the photo comparisons of this location, the pre-storm photo was taken prior to both and Irene and Nor'Ida). The post-storm and difference maps show even more extensive overwash deposits in a thicker layer farther inland. The shoreline has moved seaward indicating the beach had been severely eroded after Nor'Ida and had recovered since then.

Location 2

Pre-Storm Elevation
pre-storm elevation for Chincoteague National Wildlife Refuge, Assateague Island, Virginia

    Post-Storm Elevation
post-storm elevation for Chincoteague National Wildlife Refuge, Assateague Island, Virginia

Elevation Difference
elevation difference for Chincoteague National Wildlife Refuge, Assateague Island, Virginia
 
Location 2: Chincoteague National Wildlife Refuge, Assateague Island, VA.
The pre-storm map shows that this part of the island is very low-lying and narrow and has been overwashed by earlier storms. During Hurricane Sandy, not only was there extensive overwash and deposition, but an island breach occurred, cutting the island in two. In the post-storm map there is evidence that the breach is beginning to fill in naturally which is not evident in the photo comparisons. To the left of the breach (south), road crews have pushed sand off the roadway into a line of piled sand.

Note: The results presented here are considered preliminary and have not been thoroughly reviewed or edited. They are based on preliminary data that may be updated as the survey accuracy improves in future processing steps such as application of the precise ephemeris for GPS satellites, offset checks using ground control surveys, checks for laser calibration and mounting errors, and full application of data quality control, assurance and editing procedures.


St. Petersburg Coastal and Marine Science Center > National Assessment of Storm-Induced Coastal Change Hazards > Hurricane Sandy

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