T A SO T
R NP R
LOSS TO SINKS
SECONDARY
NOOAL
POINT CELLS
Figure 3. a) Occurrence of historic barrier island inlet breakthrough features and offshore bathymetry in
vicinity of Bethune Beach, FL and b) schematic of hypothesized cell circulation and erosional nodal points
based on morphology and sediment distributions (After Stauble and Da Costa, 1987).
East Pass. FL: At coastal locations where projects have been maintained or recently constructed, it may
be difficult to separate natural from man-made influences on the local morphology. East Pass, Florida,
provides an example. A preliminary examination of aerial photographs would suggest that net drift must
be to the west. However, project files indicate that during construction of the jetties in 1968, sand was
deposited immediately east of the east jetty (Figure 4). From available data, it is not possible to
determine how much of the progradation of the east shore was natural and how much was man-made.
On the opposite side of the inlet, a weir near the landward end of the west jetty allowed sand to enter the
inlet, where it settled in a deposition basin. Since the weir was closed in 1986, the beach on the west
side has been prograding. Along most of this stretch of the Florida Panhandle, longshore drift has been
generally considered to be westward.However, the recurved beach ridges west of the inlet indicate that
this portion of Santa Rosa Island grew to the east. Also, the pre-1928 inlet ran northwest-southeast and
exited to the Gulf of Mexico about 1.5 miles east of the present inlet's mouth. Therefore, it appears that
net drift in the immediate vicinity of East pass is from west to east. Recent evidence (Morang, 1991)
suggests that a nodal point (cell boundary) may exist in the East Pass area, and that frequent drift
reversals occur. This may be driven by subtle variations in meteorology. This complicated example
underscores why a thorough examination of historical maps and project files should be undertaken when
examining morphologic indicators of drift at a site where man-made influences may be important.
SUMMARY: Each of the above examples of shore protection or navigation problems required studies
of the coastal processes that affect the area. The use of field observations, historical shoreline trends,
coastal processes data analysis, and the relationships of coastal morphology to the projects were combined
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