|
|
|
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.
|
