January 20, 2004
10:23
WSPC/101-CEJ
00092
Coastal Engineering Journal, Vol. 45, No. 4 (2003) 565600
c World Scientific Publishing Company and Japan Society of Civil Engineers
RECENT DEVELOPMENTS IN THE GEOMORPHIC
INVESTIGATION OF ENGINEERED TIDAL INLETS
DUNCAN M. FITZGERALD
Department of Earth Sciences, Boston University,
675 Commonwealth Avenue, Boston, MA 02215
dunc@bu.edu
GARY A. ZARILLO
Division of Marine and Environmental Systems,
Florida Institute of Technology, Melbourne FL 32901
zarillo@fit.edu
SHELLEY JOHNSTON
Department of Earth Sciences,
Boston University, Boston, MA 02215
shelleyj@bu.edu
Received 15 July 2003
Revised 27 October 2003
In recent years, numerous technological advances have made field studies and laboratory
analyses of tidal inlets more time efficient while also substantially improved data qual-
ity. Mapping channel bathymetry was once a labor-intensive task that was accomplished
by measuring water depths along a detailed network of channel profiles. Now aircraft-
operated Light Detection and Ranging (LIDAR) can accurately map the bathymetry of
most tidal inlets in a few hours' time. If greater detail of the channel bottom is required,
then a multibeam acoustic system is utilized, although this technique is deployed from a
boat and is less time efficient. The topographic version of LIDAR enables the construc-
tion of inlet shoreline maps and determination of volumes associated with shoreline gains
and losses. In another advancement, side scan sonar mosaics now provide a picture of
the bottom indicating different sediment types, bedrock outcrops, and bedform distribu-
tions. These surveys have also become essential for identifying scour holes next to rock
jetties and assessing the susceptibility of these structures to collapse. The accretionary his-
tory and/or migrational trend of a tidal inlet can be determined from ground-penetrating
radar transects on land and from shallow seismic surveys in water. These records provide
a representation of the layers of sediment left behind as the inlet shifted positions. The hy-
draulic regime of a tidal inlet can be much more accurately determined using the Acoustic
Doppler Current Profiler (ADCP). This instrument produces velocity profiles for an entire
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