| Summary: | This thesis is an investigation of the sensitivity of alluvial single-thread gravel-bed rivers
with noncohesive banks to riparian disturbances. A riparian disturbance is any natural or
anthropogenic disturbance that causes a significant removal of large coniferous trees
from the riparian corridor and potentially leads to decreased bank strength and planform
morphology towards a braided system. A theoretical riparian disturbance sensitivity
index is formulated and tested in terms of its validity in estimating the sensitivity of the
rivers by means of change in width from a historic "natural" condition to a present day
disturbed condition.
The riparian disturbance sensitivity index is tested through the use of case studies at the
reach level collected within the province of British Columbia. A methodology is
suggested for collecting the necessary data to apply towards the sensitivity index. The
methodology includes reach longitudinal and cross-sectional surveys, grain size analysis,
discharge analysis through watershed delineation and regionalization techniques, and
historic aerial photo analysis. Fourteen out of fifteen data sets used in this study are
satisfactory data sets that fit the assumptions necessary to apply the index.
Even though there are large uncertainties in the accuracy of the field collected data, the
proposed sensitivity index appeared to perform well when tested against the case study
data sets. The role of large, or "catastrophic," floods is examined with two flood related
indices: flash flood magnitude index and peak/mean ratio. The results lend support
towards the theory of vegetation as a control of alluvial channel morphology, in
comparison to the control of large floods. === Applied Science, Faculty of === Civil Engineering, Department of === Graduate
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