concluded that about 26,000 ft of shoreline along
Three river areas monitored during years with
the St. Marys River was subject to significant ero-
winter navigation were selected for detailed ob-
sion due to all causes. Of this, about 12,000 ft had
servation during the closed period. One site ex-
been protected in some way, leaving 14,000 ft un-
periencing minor erosion over the course of sev-
protected. Based on data collected by the Detroit
eral years showed no measurable change during
District, they concluded that waves due to wind
the entire period bracketing both closed seasons.
and small boats were far more significant than
A second site previously exhibiting bluff reces-
waves generated by large ships. They recom-
sion on the order of 1.5 ft per year continued to
mended that eroding shorelines should be struc-
recede at about the same rate through the period
turally protected to prevent erosion due to natu-
of study. Of the total bluff recession recorded at
ral causes. They concluded that control of vessel
this site from 1976 to 1981, the maximum reces-
speed was not important since they considered
sion was 8 ft, with an average of about 5 ft.
the significance of large ship waves to be minor.
The third site, despite an apparent potential
Subsequently the U.S. Army Cold Regions Re-
for damage, had not experienced meaningful ero-
search and Engineering Laboratory began a se-
sion during previous years of winter navigation.
ries of studies of the influence of ship passage on
During the 1980 closed season, however, signifi-
sediment transport and shoreline erosion extend-
cant shoreline recession was noted at five of seven
ing over several years (Alger 1977a,b, 1978, 1979a,
profiles at the site (0.52 ft). Over the 1980-81 closed
1980, 1981, Gatto 1978, 1980a,b, 1982, Hodek et
season, this site again showed little change, sug-
al. 1986, Wuebben 1978, 1981a,b,c, 1983a,b,
gesting that the temporary increase in erosion may
Wuebben et al. 1978a,b, 1984). These studies ranged
have been due to the relatively high water levels
from field documentation to numerical model-
during 1979-80, which allowed water forces to
ing of the physical effects of vessel passage on
act directly on the low bluffs at the water 's edge.
shoreline and shore structure stability.
The shore at one of the profile locations had been
The reports by Alger provide data from re-
structurally protected during the study period.
peated surveys of shore profiles from 1977 to 1981
During the 1980-81 closed period no further
along the St. Marys, St. Clair and Detroit Rivers.
changes were noted. The data collected during
Ten sites received detailed monitoring over a pe-
extended season navigation (Alger 1977a,b, 1978,
riod of years, with multiple profiles at each site.
1979a) and the limited observations during peri-
Supplementary observations included documen-
ods closed to navigation do not provide evidence
tation of ice conditions and water levels and ve-
of increased erosion due to navigation in ice on
locities during ship passage. The maximum re-
the St. Marys River.
corded shoreline recession documented over a one-
Gatto (1978, 1980a,b, 1982) reviewed the shore-
year interval was somewhat less than 4 ft, and
line characteristics and historic shoreline reces-
for the full period from 1976 to 1981 the maxi-
sion rates for the St. Marys, St. Clair and Detroit
mum recession was about 8 ft for a site on the St.
Rivers. Most of this information has been incor-
Marys River, but most sites showed little or no
porated into the final 1982 report. The specific
change over the full period of study. Although
objectives were to document bank conditions and
he found that large vessel passage can produce
erosion sites along the rivers, to monitor and com-
large hydraulic effects and cause sediment trans-
pare the amounts of winter and summer bank
port, based on these studies, Alger found no evi-
recession and change, and to estimate the amount
dence of an increased potential for ship-induced
of recession that occurred prior to winter navi-
erosion due to the presence of ice.
gation. An analysis of historical air photos showed
On the St. Marys River, Wuebben (1981a,c,
that bank recession was active prior to winter
1983b) reported the results of shore and shore struc-
navigation along the St. Marys, St. Clair and De-
ture monitoring during two winter periods with
troit Rivers and was active without winter navi-
essentially no commercial shipping. During the
gation on the St. Lawrence River.
period from 15 January to 24 March 1980 there
An extensive field program was conducted to
were only eight passages (all by icebreakers), and
inventory shoreline characteristics in terms of soil
from 31 December 1980 to 24 March 1981 there
types, shore geometry and the presence and type
were nine passages (all icebreakers except for one
of vegetation and shore protection structures
tanker). Under the program, shoreline profiles
(Gatto 1982). Three hundred and forty-five miles
were repeatedly surveyed throughout the two
of river shoreline were observed and photo-
winters to detect any change due to natural agents.
graphed at least twice yearly from 1977 through