Patterns of bar development and sand flat initiation in the South Saskatchewan River
Date
1990
Authors
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Journal ISSN
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Publisher
ORCID
Type
Degree Level
Masters
Abstract
This is a study of the development of bars and the
initiation of sand flats in a braided sand-bed river. The changes in
morphology, flow direction and hydraulic character on the surface of
bars are documented. This information is used to assess conditions on
the surface of the bar as it migrates downstream and prior to the
initiation of a sand flat. The relationship between channel topography
and bar development is also considered.
Several bars were monitored in the sandy braided South
Saskatchewan river from May to August, 1988. Measurements included flow
direction, depth, velocity, bedload transport and topographic surveys of
the channel reach. Diagrams illustrating channel topography, bar
morphology, flow direction and hydraulic character of the surface are
presented. These diagrams are used to identify changes in the spatial
pattern of the variables as the bar features migrate downstream, and to
identify changes in channel topography.
The data suggest that bar development and sand flat development
are associated with the channel topography and morphology, particularly
with the location and alignment of deep troughs such as the thalweg.
The troughs tend to draw flow over the surface of the bars creating
asymmetric hydraulic conditions, thus affecting the downstream migration
of the bar. The flow and sediment are directed away from the downstream edge of the bars resulting in some of them diminishing into the channel
bed. In some cases, the asymmetric hydraulic conditions over the
surface of the bars resulted in the feature changing from one
descriptive bar type to another.
The exposure of sand flats was only monitored at one study site,
however observations were made in other parts of the river. At the
site which was monitored, flow directed toward a channel trough created
a shallow sluice which locally lowered the water surface elevation, thus
contributing to the exposure of the sand flat. The channel morphology
was also a strong influence on the development of the sand flat at this
site. In other parts of the river, shoaling of the channel thalweg and
general aggradation of the channel preceeded the initiation of sand
flats.
Description
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Citation
Degree
Master of Science (M.Sc.)
Department
Geography
Program
Geography