ERDC/CHL CHETN-IV-61
December 2003
CONCLUSIONS: There are multiple factors to consider in the design of a jetty spur. This
document has discussed wave and tidal current processes and a few of the controlling factors,
spur elevation and length. Based on a limited set of field data for spurs, it was seen that for a S/L
(spur length over distance of spur from shore) ratio of 0.4 or greater, that the shoreline reached
the spur. Shoreline attachment to the spur may be acceptable if the wave climate is not too ener-
getic so that sediment does not by-pass the spur and move towards the channel or if the spur is
on the downcoast jetty and it is functioning to retain the by-passed sediment in the nearshore
region. It was noted from physical model study of spurs that the structure should be long enough
to significantly deflect the longshore currents away from their usual direction parallel to the jetty;
so in this respect, a spur length to shoreline distance ratio of greater than 0.4 may be necessary.
Physical and numerical models are available to develop and optimize spurs for site-specific
conditions. Modeling is likely to be necessary to understand complex current and sediment
circulation due to varying wave parameters of height, period and direction. Also the effect of
offshore bathymetry may be critical in controlling current and sediment circulation in the region
just upcoast of the jetty.
POINTS OF CONTACT: Questions about this technical note can be addressed to Mr. William
C. Seabergh (601-634-3788; e-mail: ). For informa-
tion about the Coastal Inlets Research Program, contact the Program Manager, Dr. Nicholas C.
Kraus at .
REFERENCES
Bottin, R. R., Jr. (1981). "Siuslaw River jetty extension, Oregon," Letter Report, Hydraulics
Laboratory, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.
Bottin, R. R., Jr. (1983). "Design for flood control, wave protection, and prevention of shoaling,
Rogue River, Oregon: Hydraulic model investigation," Technical Report HL-82-18, U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MS.
Kraus, N. C., and Arden, H. T. (2003). "North jetty performance and entrance navigation channel
maintenance, Grays Harbor, Washington," ERDC/CHL TR-03-12, U.S. Army Engineer Re-
search and Development Center, Vicksburg, MS.
Pollock, C. E., McGehee, D., Neihaus, R. W., Jr., Chesser, S. A., and Livingston, C. (1995).
"Effectiveness of spur jetties at Siuslaw River, Oregon: Report 1; Prototype monitoring
study," Technical Report CERC-95-14, Coastal Engineering Research Center, U.S. Army
Engineer Waterways Experiment Station, Vicksburg, MS.
Seabergh, W. C. (1999). "Physical model for coastal inlet entrance studies," Coastal Engineering
Technical Note CETN IV-19, U.S. Army Engineer Research and Development Center,
Vicksburg, MS.
Seabergh, W. C. (2002). "Weir jetties at Coastal Inlets, Part 1: Functional design considera-
tions," ERDC/CHL CHETN IV-53, U.S. Army Engineer Research and Development Center,
Vicksburg, MS.
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