PART
SUMMARY OF CORPS BREAKWATER
JETTY STRUCTURES IN NCD
3.
NCD has a total of 107 projects
in the Great
regfon
which include breakwater and/or jetty structures.
refers to many struc-
tures as piers which actually function as jetties. Therefore, the term "pier"
used in this report will carry the same meaning as the term "jetty." Seventy
of the projects are within US Army Engineer District, Detroit's
area
of responsibility; six are located within US Army Engineer District, Chicago's
boundaries; and thirty-one are under the jurisdiction of US Army
Engineer District, Buffalo (NCB). Figures 1-3 show the locations of these
projects along the Great Lakes.
Overall, there is a total of about
4 8 1 , 5 7 0 lin ft* of breakwater and/or jetty structures in
Breakwaters ac-
count for approximately 6 9 percent of this total, and jetty structures account
for the remaining 31 percent.
Construction materials used for these struc-
tures include stone, concrete, steel sheetpiling, woodpiling, timber, and con-
crete armor units (dolosse used at Cleveland Harbor, Ohio).
Twenty-one projects are located on the United States shoreline of
4.
Lake Superior, thirty-eight on the Lake Michigan shoreline, fifteen on the
Lake Huron shoreline, one on the Lake
Clair shoreline (small lake between
Lake Huron and Lake Michigan), twenty-two on the southern shore of Lake Erie,
and ten on the Lake Ontario shoreline. Structures within NCD have experienced
problems in all four major REMR problem areas (runup and overtopping, local-
ized damage, toe stability, and use of dissimilar armor). Many of
proj-
ects have deteriorated and have been repaired or modified since construction.
5.
Breakwaters and jetties in NCD have been constructed on top of exist-
ing sediments (usually fine to coarse sand) in water depths ranging from 8 to
These structures have crest elevations (el) ranging from 4 to 18 ft
7 0 ft.
and crest widths ranging from 1 to about 6 0 ft. Side slopes of stone struc-
tures range from
to
Design guidance for breakwater cross-
sections (stone sizes, crest height, width, etc.) is provided by the Shore
Protection Manual (SPM) ( 1 9 8 4 ) or other appropriate Corps engineering manuals.
projects have been model tested at the US Army Engineer
Several of
Waterways Experiment Station.
*
A table of factors for converting non-SI units of measurement to SI
(metric) units is presented on page 3 .
6
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