a. Jamming at a bar.
b. Jamming aggravated by border
ice and grounded ice on a bar.
Figure 16. Jamming due to ice congestion at confluence bars. Note that
jamming may occur for an ice run from either one or both channels.
conditions in both confluent channels, ice from the smaller channel may ground
on exposed alluvial bars and dunes. Grounded ice may lead to arching of ice
pieces and, thereby, to jam initiation.
SELECTED OBSERVATIONS
A selection of observations from the pro-
cess model are presented here to illustrate
the two mechanisms described above and
to show how they are affected by conflu-
ence angle α, relative magnitudes of inflow
discharge, Q1/Q2, and relative widths of
inflow channel, b1/b2. Three confluence
angles are considered, α = 180, 90, and
45. In the ensuing brief series of illustra-
tive examples of observations from the
small-scale model, channel 1 is the larger
inflow channel, and the outflow channel
is of the same dimensions. Channel 2 is the
smaller inflow channel. Table 1 briefly
summarizes the main observations.
α = 180 confluence
Figure 18 depicts the model setup at this
angle. The discharge ratio, Q1/Q2, was set
Figure 17. Ice jamming at discordant-
successively at 0, 1, and 4. Forming a jam
bed confluence with deltaic bars.
29
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