To appear: Shore & Beach, Vol 72, No. 1, 2004.
Inlet is marginally stable, which is indicated by a constant relative position of the
inlet cross-sectional areas relative to pertinent closure curves in the Escoffier
relation (Headland et al., 1999). There is a considerable amount of sediment
entering Fire Island Inlet each year through littoral transport and the excessive
length of the inlet channel makes it hydraulically inefficient.
An ESRI Arcviewtm extension, known as BeachTools (Hoeke, et al. 2001),
was developed to identify and quantitatively establish the position of the
shoreline and other coastal features from aerial imagery. The extension uses
image analysis techniques to extract a polygon representation known as a
shoreline shapefile to map the beach between the vegetation line and the wet/dry
line (saturation line). The BeachTools extension also calculates transects from a
user-defined baseline at selected intervals, allowing for high frequency, shore-
perpendicular measurements of the wet/dry and vegetation lines. Differencing
the transect lines from various aerial survey sets provide quantitative estimates
of erosion and accretion of the beach between the lines.
The project methodology included shoreline extraction from a database of
aerial photography and the creation of gridded topographic surfaces from 1933
and 1950-1951 hydrographic surveys and the May 1996 Scanning Hydrographic
Operational Airborne Lidar Survey or SHOALS data (Irish et al., 2000). The
vertical accuracy is 6 in for the hydrographic survey data, and 10 in for the
SHOALS data. Horizontal accuracy for both types of surveys is expected to be
on the order of 10 to 20 ft. From these datasets, volume and spatial change
calculations were performed.
Morphologic evolution and engineering over the past 70 years
The Fire Island Inlet system includes a 17-mi span of barrier islands and
water, stretching from the town of Gilgo Beach on Jones Beach-Cedar Beach
Barrier Island to the village of Saltaire on Fire Island. The aerial photography