Engineering Activities
The engineering history from 1933 to 1995 indicates that beach fill placement has been
a significant source of littoral material, or a significant means of inlet bypassing (for those
activities involving channel dredging and downdrift beach placement), from Shinnecock
Inlet through Gilgo Beach. Fig. 3 shows the cumulative volumetric rate of littoral material
placement for the study area beaches for 1979 to 1995 and 1933 to 1979. "Adjusted" data
are also presented, which assumed that 75-percent of the breach fill placed during 1979 to
1995 replaced barrier littoral material that had been transported in the cross-shore direction,
either towards the bay or offshore. The remainder (25-percent) of this material was
assumed to be available for LST. Because pre- and post-breach data were unavailable, this
assumption was based on visual inspection of pre- and post-breach aerial photographs. For
comparison, also noted in Fig. 3 are the results of the Democrat Point Spit Analysis
(discussed below) and Taney' (1961a,b) range of LST rates at Fire Island Inlet. Of primary
s
interest is that the rate of littoral material placement (or transfer from inlets to the barrier
beaches) is of the same magnitude as accepted values of net LST.
Fig. 3. Cumulative rate of beach fill placement from Fire Island Inlet
to Montauk Point.
Profile Data and Topographic Sheets
Profile data from 1979 and 1995 were used to define B(x) and DC (x) for the barrier
island ocean shoreline. Values of B(x) and DC (x) for the bay shoreline, used in an analysis
of spit growth for Democrat Point prior to stabilization, were assumed by reducing the
ocean values. For the Montauk Point bluff region, values for B(x) ranged from those
determined for the barrier island ocean shoreline (Alternative 1) to higher values
representing the bluff crest line as derived from 1980 topographic sheets (Alternative 2).
In an analysis determining the rate of new spit growth at Democrat Point prior to
7
Rosati et al.
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