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F.S. Buonaiuto, N.C. Kraus / Coastal Engineering 48 (2003) 5165
Fig. 2. Bathymetry contours and transect locations for Moriches Inlet, 1996 survey.
To quantify the influence of grid interval on
that was poorly resolved (smoothed) by the larger
calculated slopes and depths of ebb-shoal features,
grid spacing produced large scatter. Filtering of small
data from New Pass (1997) and Moriches Inlet
bathymetric variations by the larger-spaced grids
(1996) were interpolated onto 3.048, 4.57, 7.62,
produced a smooth continuous contour plot, but this
15.24, 22.86, and 30.48 m square grids. Contour
resolution reduced the accuracy of determined slopes
plots and transects were constructed and analyzed for
and depths.
each interval selected. As expected, larger grid
Sensitivity tests were performed to assess the
interval filtered (removed) small bedforms, giving a
variability of slope magnitude and its dependence on
sample interval, Dx. The analysis compared several
smoother representation of the bottom. Loss of
information with larger sampling interval is illus-
transects from regions with small bathymetric gra-
trated in Fig. 3 for the 1997 Shinnecock Inlet survey
dients (minimal morphologic variation). These re-
(a survey with substantial spatial coverage), which
gions, located up-drift and down-drift of the ebb
shows the 1-m contours as produced from the six
shoal, were assumed to represent reliable measure-
grid intervals listed above. In contrast, a smaller
ments of the SHOALS uncontaminated by complex
interval produced larger fluctuations in slope and
bottom features of various scales. The average devia-
bathymetric variations that appeared in contour maps
tion of transects from this ideal bathymetry was taken
as isolated promontories. Discrepancies between dif-
as an estimate of variability, which for these data sets
ranged between 0.3 and 0.5j. Sensitivity of the
ferent grid intervals were most apparent in calcula-
tion of slopes along transects that bisected the lateral
variability estimates to grid spacing was examined
walls of the inlet channels. Here bathymetric change
by incrementing a decimated averaging-scheme along
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