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St. Petersburg Coastal and Marine Science Center > Coastal Change Hazards: Hurricanes and Extreme Storms > Hurricane Irene

Coastal Change Hazards: Hurricanes and Extreme Storms

Hurricane Irene

Pre-Storm and Post-Storm 3D Lidar Topography: Outer Banks, NC

A NOAA-USGS airborne lidar survey of post-storm topography was completed August 28, 2011 along the North Carolina coast to detect coastal change resulting from Hurricane Irene. Comparisons of the post-storm elevation data to lidar data collected in 2009 are used to characterize the nature, magnitude, and spatial variability of hurricane-induced coastal changes, such as beach erosion, overwash deposition, and island breaching.

Location Map
Location index for pre-storm and post-storm lidar elevations for the Outer Banks, NC. Each location includes pre- and post-storm topography as well as topographic change. The green line shows Hurricane Irene's track.

On the elevation images below, red colors indicate topographic highs, while blues indicate topographic lows. The differences between the pre- and post-storm elevation data sets show where significant changes have occurred. Red colors indicate erosion. For example, oranges and reds on the seaward side of the islands indicate wide-spread shoreline retreat. (In each image, the Atlantic Ocean is on the bottom right.) Blue colors show areas of accretion, such as overwash deposits where waves and surge have moved sand landward.

Location 1

Pre-Storm
pre-storm lidar topography for a portion of Core Banks, North Carolina

    Post-Storm
post-storm lidar topography for a portion of Core Banks, North Carolina

Difference
topohraphic change for a portion of Core Banks, North Carolina
 
Location 1: Lidar topography from August 11-15, 2009 (Pre-Storm) and August 28, 2011 (Post-Storm) and topographic change (Difference) for a portion of Core Banks, NC.
A relatively low beach section near the center of the pre-storm image likely indicates where breaches have been cut through the barrier island at previous times. The Irene breach is clearly seen in the post-storm lidar data. The difference image shows over 1 m of vertical erosion in the beaches that were breached. See pre- and post-storm photo comparisons for additional discussion.

Location 2

Pre-Storm
pre-storm lidar topography for a portion of Ocracoke Island, North Carolina

    Post-Storm
post-storm lidar topography for a portion of Ocracoke Island, North Carolina

Difference
topographic change for a portion of Ocracoke Island, North Carolina
 
Location 2: Lidar topography from November 27-December 1, 2009 (Pre-Storm) and August 28-29, 2011 (Post-Storm) and topographic change (Difference) for a portion of Ocracoke Island, NC.
In the pre-storm image, the continuous, relatively high elevations, occurring just seaward of the road, appear to be either natural or human-made dunes. In the post-storm image, the central portion of these dunes was eroded. The difference image shows erosion of the beach and dunes and deposition landward of the road, signs of overwash when waves overtop the beaches and dunes and drive sand inland. See pre- and post-storm photo comparisons for additional discussion.

Location 3

Pre-Storm
pre-storm lidar topography for a portion of Hatteras Village, North Carolina

    Post-Storm
post-storm lidar topography for a portion of Hatteras Village, North Carolina

Difference
topographic chang for a portion of Hatteras Village, North Carolina
 
Location 3: Lidar topography from November 27-December 1, 2009 (Pre-Storm) and August 28-29, 2011 (Post-Storm) and topographic change (Difference) for a portion of Hatteras Village, NC.
In the pre-storm image, note the prominent dunes (broad line of relatively high elevations) across the center of the image. In the post-storm, the band of dunes appears somewhat narrower. This is seen more clearly in the difference image, where landward of the eroded beach, there is a line of high erosion of the ocean-side of the dunes, presumably by waves during Irene. There is also some indication of overwash, with a more landward line of erosion followed by a line of deposition. See pre- and post-storm photo comparisons for additional discussion.

Location 4

Pre-Storm
pre-storm lidar topography for a portion of the Outer Banks near Rodanthe, North Carolina

    Post-Storm
post-storm lidar topography for a portion of the Outer Banks near Rodanthe, North Carolina

Difference
topographic change for a portion of the Outer Banks near Rodanthe, North Carolina
 
Location 4: Lidar topography from November 27-December 1, 2009 (Pre-Storm) and August 28-29, 2011 (Post-Storm) and topographic change (Difference) for a portion of the Outer Banks near Rodanthe, NC.
In the pre-storm image, note where the road bends seaward, approaching the Atlantic Ocean. Here, the road is protected by sand filled bags that appear dune-like in the lidar topography. The post-storm image reveals where the waves and surge from Irene broke through the protection and carved a breach. The difference image shows the extensive erosion associated with breach formation. See pre- and post-storm photo comparisons for additional discussion.
Caption: text.

Location 5

Pre-Storm
pre-storm lidar topography for a portion of the Outer Banks in the Pea Island National Wildlife Refuge, North Carolina

    Post-Storm
post-storm lidar topography for a portion of the Outer Banks in the Pea Island National Wildlife Refuge, North Carolina

Difference
topographic change for a portion of the Outer Banks in the Pea Island National Wildlife Refuge, North Carolina
 


Location 5: Lidar topography from November 27-December 1, 2009 (Pre-Storm) and August 28-29, 2011 (Post-Storm) and topographic change (Difference) for a portion of the Outer Banks in the Pea Island National Wildlife Refuge, NC. In the pre-storm image, note the two particularly low elevation areas between a relative high. During the storm, surge and waves were funneled through the lower areas, carving two breaches (post-storm image). The difference image shows the intricate pattern of erosion associated with the formation of the breaches. See pre- and post-storm photo comparisons for additional discussion.

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.

Location 1 Location 2 Location 3 Location 4 Location 5

St. Petersburg Coastal and Marine Science Center > Coastal Change Hazards: Hurricanes and Extreme Storms > Hurricane Irene

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