ERDC/CHL CHETN-III-66
June 2003
concentrated around the jetties' seaward heads. An area of concern was noted during the walking
inspection at the tip of the south jetty where a broken unit had resulted in exposure of the core stone
under the jetty cap. During the period October 1991 through March 1994, three major storm events
(northeasters) occurred in the vicinity of Manasquan Inlet. These events probably significantly
contributed to the armor unit movement and breakage at the heads of the jetties.
The August 1998 photogrammetric survey revealed significantly less dolos movement between 1994
and1998 as detected during previous survey periods. Movement of dolos targets in the horizontal
direction ranged from 0 to 0.55 m (0 to 1.8 ft), and vertical displacement ranged from 0 to 0.07 m
(0 to 0.22 ft). Only three target positions on the north jetty moved over 0.15 m (0.5 ft) in the
horizontal direction, and all other targets on the north structure moved 0.08 m (0.25 ft) or less. On
the south jetty, all targets moved 0.06 m (0.21 ft), or less, horizontally. In the vertical direction,
target movement did not exceed 0.07 m (0.22 ft) on the north jetty and 0.06 m (0.21 ft) on the south
structure. Between 1994 and 1998, the average movements of the targets on the north jetty were
0.05 and 0.03 m (0.15 and 0.09 ft) in the horizontal and vertical directions, respectively. On the
south jetty, the average movements of the targets in the horizontal and vertical directions, were 0.02
and 0.03 m (0.07 and 0.09 ft), respectively. During the previous surveys, the more significant
movement occurred around the heads of the jetties. During this period (1997), however, the jetty
heads were rehabilitated with CORE-LOCs. Some dolosse were covered and/or repositioned during
this process. Therefore, no correlation in movement could be made for armor units in areas where
the more significant movement had occurred previously. During the November 1998 broken armor
unit survey, eight broken/cracked dolos armor units were observed. Four broken units were
observed on each structure. Of the eight broken armor units observed, six were identified in the
previous 1994 survey, and two were new breaks. As stated earlier, 17 broken units were observed in
1994. During the 1997 CORE-LOC rehabilitation, however, several broken dolosse were removed
from the heads of the structures. Records indicate that several northeasters occurred between 1994
and 1998. During the 1998 periodic inspection, initial base data were obtained for the CORE-LOC
armor units installed on the heads of the jetties. These data will establish a base from which to
evaluate the effectiveness and analyze the performance of the CORE-LOCs in subsequent
inspections.
ADDITIONAL INFORMATION: Questions relative to this CHETN may be addressed to
Mr. Robert R. Bottin, Jr., Coastal Harbors and Structures Branch, Coastal and Hydraulics
Laboratory, U.S. Army Engineer Research and Development Center at (601-634-3827), FAX (601-
634-4827), or e-mail: Ray.R.Bottin@erdc.usace.army.mil. Additional information on the MCNP
Program may be obtained from: http://chl.wes.army.mil/research/navigation/mcnp_site/default.htm.
This CHETN summarizes data obtained for concrete-armored coastal structures under the "Periodic
Inspections" work unit of the MCNP Program. Detailed information relative to photogrammetric
techniques, design and model studies, and case histories, etc. of the structures discussed herein may
be obtained from individual references listed in the following "References" section.
REFERENCES
Bottin, Robert R., Jr., and Boc, Stanley J. (1996). "Periodic inspection of Nawiliwili Harbor breakwater, Kauai, Hawaii;
Report 1: Base conditions," Technical Report CERC-96-5, U.S. Army Engineer Waterways Experiment Station,
Vicksburg, MS.
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