tial site for controlling ice during breakup. Ac-
ice-control or ice-breaking equipment, which
shall be loaned to units of local government to-
cording to local residents, problem breakups typ-
gether with operating assistance, where appro-
ically consist of a 0.5- to 2-mile-long jam (though
priate.
sometimes as long as 4 miles), which propagates
The act also authorized and directed the Secre-
slowly in a series of jam and release cycles down
tary of the Army to undertake a series of demon-
the Yellowstone and continuing into the study
stration projects for the structural control of ice,
reach on the Missouri River. Flood flows and ice
projects that were to be exempt from the cost-shar-
breakup on the Missouri River generally occur
ing provisions of Section 103 of the Water Resourc-
several weeks after the Yellowstone River ice run.
es Development Act of 1986. Under this act the
One of the natural jamming points for the Yellow-
Corps of Engineers would have been authorized
stone River ice run is in the confluence area, and
and funded to assist local communities in analyz-
based on interviews with local residents concern-
ing their ice-related flooding and streambank ero-
ing jams in that area, the jams have not caused
sion problems, develop measures to control ice
significant damage in the past. Causing the jam to
and mitigate damages, and lend specialized "ice-
remain in this area would surely alleviate down-
breaking" equipment that could have been used to
stream ice jam flooding. Ideally the ice should be
implement some of the advance or emergency
retained and allowed to melt at this site. The ob-
measures described above. At some sites, structur-
servation that the spring breakup ice run propa-
al ice control measures would also have been im-
gates tens of miles while the jams remain relative-
plemented. Unfortunately the necessary funding
ly short and constant in length indicates that sig-
was never appropriated.
nificant melting is a common feature at breakup
and can be used to advantage in conjunction with
structural control.
SUMMARY AND
Numerous types of structures or stream alter-
CONCLUSIONS
ations could be used for ice control in the conflu-
This report has reviewed historical and recent
ence area. Rock-filled timber cribs, spur dikes, ice
information on ice processes and ice-related flood-
control weirs, ice booms and a dredged ice reten-
ing in the vicinity of the BufordTrenton Irrigation
tion pool are potential alternatives. If necessary a
District near Williston, North Dakota. Based on
high-level flood bypass or diversion channel
that information, an evaluation of the ice regime of
could be incorporated into the design to ensure
the Missouri and Yellowstone Rivers was conduct-
proper performance of the structure and to re-
ed to assess the potential severity of ice-related
duce flood levels in the vicinity. Numerous exist-
flooding. A scheme for estimating the potential for
ing water level gages that are either inoperable in
ice-related flooding in any given year was out-
winter or totally abandoned could be used as
lined, along with a suggestion that existing water
sites for detecting ice movement and providing
level gages be reactivated for winter activity to
advance warning of breakup or flooding.
provide an early warning mechanism for ice
Most ice control projects pursued by the Corps
breakup and flooding. Finally, a number of struc-
of Engineers in the past have been conducted un-
tural and nonstructural flood control measures
der the general authority of Section 205 of the
were reviewed from a technical applicability
1948 Flood Control Act, as amended. That act au-
standpoint. Mitigation techniques recommended
thorized the expenditure of funds for the con-
for further, detailed study include a program of ice
struction of small projects for flood control and
weakening in advance of spring breakup, im-
related purposes not specifically authorized by
provements to existing irrigation ditches to allow
Congress. More recently the Water Resources De-
them to afford an increased level of protection as
velopment Act of 1986, Title XI, Section 1101 (U.S.
pseudo-levees, and structural ice control or diver-
Congress 1986) directed the Secretary of the
sion on the Yellowstone River near its confluence
Army to undertake a program of research and
with the Missouri River.
community assistance for the control of ice and
ice-induced streambank erosion. Further, the act
authorized the Secretary of the Army to:
REFERENCES
...provide technical assistance to units of local
Andres, D.D., and G.D. Fonstad (1982) Freeze-up
government to implement local plans to con-
observations and aspects of the ice anchor on the
trol or break up such ice. As part of such au-
Bow River and Calgary. In Proceedings of the Work-
thority, the Secretary shall acquire necessary
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