This study investigates channel bed scour and fill as a result of individual flood events in a
gravel-bed channel. Given the complexity of interactions between hydraulic force, the texture and
arrangement of bed material, and input of sediment to a particular point of the channel bed, study
objectives were pursued with the view that bed material movement is a stochastic phenomenon.
A two-year field program was conducted in Carnation Creek, a small gravel-bed stream
draining 11 km2 on the west coast of Vancouver Island, British Columbia. In the 900 m study
reach, an array of measurement techniques, including scour indicators, magnetically-tagged stones,
and conventional survey, yielded information about the fluctuations of the channel bed elevation
and movement of scoured material for individual flooding periods.
Frequency distributions of scour and fill depths associated with individual flooding periods
are adequately modeled by negative exponential functions over the range of flood peak magnitudes
observed in Carnation Creek. Analysis of scour depths measured in streams on the Queen
Charlotte Islands demonstrates the applicability of the exponential model to flooding periods and
flood seasons. Further, exploratory analysis suggests that a regional scour depth model is
possible.
Power functions relating mean depths of scour and fill to flood peak discharge show that
depth increases with an increase in peak magnitude. Observed maximum scour depths in flooding
periods are linked, in general, to streambed conditions influenced by antecedent flow conditions.
These patterns in scour and fill exist within an overall pattern of increasing variability in depths of
scour and fill as peak discharge increases.
Evaluation of a heuristic model for mean travel distance as a function of particle size
proposed by Church and Hassan (1992) provides convincing evidence for its general merit. Mean
travel distance decreases inversely with particle size as size increases beyond the median diameter
of subsurface sediment. This trend is consistent in both individual flooding periods as well as
flood seasons. The majority of material finer than the median diameter of surface sediment is
supplied from subsurface material, which influences the travel distances of these finer fractions
because of burial. Computation of volumetric transport rates of bed material, based on the active scour depth
and width of the channel bed, the virtual velocity of particle movement, and sediment porosity,
suggests the potential for building scale correlations with streamflow, which have usually been
defined by bedload sampling during floods. Error analysis indicates that determination of active
width contributes most significantly to the imprecision of transport rate estimates.
Results underscore the stochastic nature of sediment transport in gravel-bed channels. / Arts, Faculty of / Geography, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/4843 |
| Date | 05 1900 |
| Creators | Haschenburger, Judith Kay |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 9150355 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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