RIVER ICE INFLUENCES ON FORT PECK REACH, MISSOURI RIVER
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Specific issues for survey sites
The survey necessitated sets of activities aimed at determining if and how the
ice-related erosion mechanisms discussed above affect bank and channel condi-
tions at the sites. Each site was monitored with the following questions in mind:
What evidence exists that the ice-related channel change or erosion
mechanisms are active at the site?
How do the erosion mechanisms affect the site?
If the mechanisms appear significant, what structural or bathymetric
methods would mitigate them?
What further investigation would be needed to confirm the mechanisms
and establish the methods identified to mitigate them?
Features of survey sites
Culbertson, RM 16201621
This site is representative of river reaches with upstream and downstream
ends that are constrained and narrowed to a single channel by a bluff located
along one side of the river. Figure 3 shows the site in the summer of 1996 and
Figure 2a shows the reach immediately upstream of the Culbertson site.
Between these two constrictions, the channel widens along the greater por-
tion of the reach and initially divides into two subchannels around a vegetated
bar as illustrated by Figure 16. Then, it further subdivides into as many as three
subchannels. The channel subsequently narrows as the river becomes constrained
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