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Airphoto mosaic of Topsail Beach after Hurricane Bonnie

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Karen Morgan
  Middle Section - Topsail Beach
34°26.05'N   77°31.32'W

The low dunes at Topsail Beach, which had been rebuilt after Hurricane Fran in 1996, were again overwashed by Hurricane Bonnie. This is evident in the change plot below, where dark blue (accretion) lies directly landward of reds and yellows (erosion). In the pre-storm elevation data, a faint, straight continuous pale green line can be seen directly seaward of the front row of beach houses. This pale green line represents the post-Fran reconstructed dune. In the 1998 elevation data the green line is broken in areas and "smeared" inland. The change plot shows the extent of sheet overwash (modified by crews moving sand off the roads before the ATM data was flown). Houses appear as gray (non-change) areas in the blue band of overwash. In profile comparison 1, sand was removed from the beach and transported inland resulting in 2.5 m of vertical accretion. Similarly, profile comparison 2 shows extensive erosion and overwash deposition amounting to 0.5-0.9 meters of vertical accretion. Note the accretion commonly occurs landward of houses indicating that flow during the storm went underneath the houses, most of which were built on stilts. In profile comparison 3, the proximity of the house to the dune obscures the fate of the dune, however, the photograph shows there is overwash under and behind the house. Note the "new" house 200 meters landward of the beach. This house was build after the 1997 survey.

About the Change Plot 1997-1998 Change Change Scale Elevation Data
Elevation Data
About the Elevation Data

Passive Data
Passive Data

About the Passive Data

Coastal and Marine Program > St. Petersburg Coastal and Marine Science Center > Research by Theme > Hazards > Hurricane and Extreme Storm Impact Studies > Hurricane Bonnie > Coastal Change From Lidar > Middle Section


U.S. Department of the Interior, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center
http://coastal.er.usgs.gov/hurricanes/bonnie/lidar/middle.html
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Updated December 05, 2016 @ 11:24 AM (THF) North Section South Section Profile 1 Profile 2 Profile 3