- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Application of a rational model of stream equilibrium...
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Application of a rational model of stream equilibrium for predicting channel adjustments MacVicar, Bruce Jonathan
Abstract
In this thesis, channel geometry adjustments and possible restoration efforts were modeled and interpreted for three streams in British Columbia using the physical model of Millar and Quick (1993). The major challenge of the project was to overcome limitations in our ability to quantify important physical processes such as flow resistance, sediment transport, and bank stability in order to access the inherent predictive and modeling capabilities of a rational approach. In practical terms this meant the model had to be calibrated to past adjustments of channel geometry before it could be used to predict future changes. The success of calibration was found to be dependent on the type of disturbance a stream was adjusting to. Disturbances of bank stability were readily modeled. Calibration was facilitated by the sensitivity of modeled widths to changes in bank stability and the availability of air photographs to measure historical changes in channel width. Slesse Creek was found to have been disturbed by a reduction in bank stability due to forest harvesting in the riparian area of the creek. The creek adjusted by widening its channel and switching from a single to a multiple thread. Modeling results indicated that a moderate increase in bank stability could be used to reinstate a singlethread channel, reduce bank and floodplain erosion and allow vegetation to recover. Disturbances to water discharges were also readily modeled provided that flow records existed or that past flows could be estimated from a clearly defined bankfull flow condition. Shovelnose Creek was found to have been disturbed by an increase in the discharge conveyed by the channel. The creek adjusted to the increase by widening and deepening its channel, and breaks in the slope were introduced. These breaks were now control points as channel discharge has been reduced to pre-disturbance levels. Modeling indicated that the use of point deflectors to narrow and deepen the channel may be particularly suited to Shovelnose Creek due to the lateral and vertical stability of the channel. Disturbances to the sediment transport regime were not readily modeled. The example of Harris Creek highlighted the difficulty of assessing simultaneous changes of particle sizes, channel roughness, and sediment transport. The longer time scale of sediment supply waves and effect of bedrock control on slope were additional difficulties. The approach used to apply the rational model of Millar and Quick (1993) was advantageous because it focused on stream processes, produced exact numerical results and resulted in a stream response framework that was specific to each stream. The approach thus represents a step forward from other available approaches. Further research that could increase the applicability of the rational model is discussed.
Item Metadata
Title |
Application of a rational model of stream equilibrium for predicting channel adjustments
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
1999
|
Description |
In this thesis, channel geometry adjustments and possible restoration efforts were modeled and
interpreted for three streams in British Columbia using the physical model of Millar and Quick
(1993). The major challenge of the project was to overcome limitations in our ability to quantify
important physical processes such as flow resistance, sediment transport, and bank stability in
order to access the inherent predictive and modeling capabilities of a rational approach. In
practical terms this meant the model had to be calibrated to past adjustments of channel geometry
before it could be used to predict future changes. The success of calibration was found to be
dependent on the type of disturbance a stream was adjusting to.
Disturbances of bank stability were readily modeled. Calibration was facilitated by the sensitivity
of modeled widths to changes in bank stability and the availability of air photographs to measure
historical changes in channel width. Slesse Creek was found to have been disturbed by a
reduction in bank stability due to forest harvesting in the riparian area of the creek. The creek
adjusted by widening its channel and switching from a single to a multiple thread. Modeling
results indicated that a moderate increase in bank stability could be used to reinstate a singlethread
channel, reduce bank and floodplain erosion and allow vegetation to recover.
Disturbances to water discharges were also readily modeled provided that flow records existed or
that past flows could be estimated from a clearly defined bankfull flow condition. Shovelnose
Creek was found to have been disturbed by an increase in the discharge conveyed by the channel.
The creek adjusted to the increase by widening and deepening its channel, and breaks in the slope
were introduced. These breaks were now control points as channel discharge has been reduced to pre-disturbance levels. Modeling indicated that the use of point deflectors to narrow and deepen
the channel may be particularly suited to Shovelnose Creek due to the lateral and vertical stability
of the channel.
Disturbances to the sediment transport regime were not readily modeled. The example of Harris
Creek highlighted the difficulty of assessing simultaneous changes of particle sizes, channel
roughness, and sediment transport. The longer time scale of sediment supply waves and effect of
bedrock control on slope were additional difficulties.
The approach used to apply the rational model of Millar and Quick (1993) was advantageous
because it focused on stream processes, produced exact numerical results and resulted in a stream
response framework that was specific to each stream. The approach thus represents a step
forward from other available approaches. Further research that could increase the applicability of
the rational model is discussed.
|
Extent |
18324774 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-06-12
|
Provider |
Vancouver : University of British Columbia Library
|
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.
|
DOI |
10.14288/1.0063747
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
1999-05
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
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.