ERDC/CHL CHETN-I-65
June 2002
Some CGWAVE results show an oscillatory variation seaward of the breakwater gap. This
variation disappeared in results from some additional runs with directionally spread, rather than
unidirectional spectra (not shown). Prototype waves are directionally spread, and physical
models may induce some directional spreading, even when wave generators are run in a
unidirectional mode.
SUMMARY: Prototype data were analyzed from several sources to determine incident wave
characteristics offshore of the Morro Bay Harbor entrance. For similar incident wave conditions,
prototype data at two gauge locations within the harbor entrance were compared with physical
and numerical model results. Physical model data revealed wave heights slightly lower at the
outer gauge location and slightly higher at the inner gauge location when compared to the
prototype. The difference is probably due to the actual gauge locations. In the physical model,
gauges were positioned in the center of the channel. It was not possible to locate prototype
gauges in the channels due to navigation hazards. The outer prototype gauge was placed in
shallower water shoreward of the entrance than the model gauge where an increase in wave
height would be expected due to shoaling. The inner prototype gauge location was placed in a
more protected area than the model gauge where decreased wave heights would be expected.
Considering these factors and noting transformations of wave energy through the entrance, it
appears that the physical model wave data obtained through the entrance were an accurate
representation of the prototype.
Comparison of the initial HARBD numerical model results to field and physical model data
indicates wave heights in the Morro Bay entrance were overestimated. The lack of wave
breaking and the use of monochromatic waves were limitations and probably contributed to the
overprediction of wave heights for HARBD. A comparison of CGWAVE, the most current
numerical harbor wave model, results with field and physical model data reveals wave heights to
be much more comparable in the Morro Bay Harbor entrance and much improved over the
original HARBD model.
ADDITIONAL INFORMATION: Questions relative to this CHETN may be addressed to
Dr. Edward F. Thompson at (601-634-2027), FAX (601-634-3433), or e-mail:
army.mil or, Mr. Robert R. Bottin, Jr., at (601-634-3827), FAX (601-634-4827), or e-mail:
. CGWAVE modeling for Morro Bay Harbor was performed by Mr. Steve
Bratos and Dr. Zeki Demirbilek. More detailed information on this study may be obtained from
(Thompson, Bottin, and Shak 2002). This technical note should be cited as follows:
Bottin, R. R., Jr. and Thompson, E. F. (2002). "Comparisons of physical and
numerical model wave predictions with prototype data at Morro Bay Harbor
Entrance, California," ERDC/CHL CHETN I-65, U.S. Army Engineer Research
and Development Center, Vicksburg, MS.
REFERENCES
Bottin, R. R., Jr. (1993). "Design for entrance channel navigation improvements, Morro Bay Harbor, Morro Bay,
California," Technical Report CERC-93-2, U.S. Army Engineer Waterways Experiment Station, Vicksburg,
MS.
14
Previous Page
