This study is an examination of the rate at which organic debris and clastic sediment
accumulate in a gully after it is scoured by a debris torrent. Of particular interest is the
effect that a change in land use from old-growth to clear-cut conditions may have on these
rates. This change should result in a reduction in the delivery of large organic debris
(LOD), which is a major factor in sediment storage in gullies. It is hypothesized that this
change in land use, and the subsequent reduction in the LOD supply, should result in a
significant difference in debris recharge rates between old-growth and clear-cut gullies.
Twenty-nine gullies in both land-treatment groups were sampled on the west coast of
the Queen Charlotte Islands. Sampling procedures involved the estimation of the volume of
LOD and sediment in storage (normalized by the gully surface area) and the determination
of the time elapsed since the last debris torrent. These data were then used to estimate
recharge rates(3h1)am’year of LOD, sediment, and total debris.
Recharge rates of each material were compared between land-treatment groups using
the nonparametric Mann-Whitney test. This test revealed that LOD has been delivered to
old-growth gullies at a significantly higher rate relative to clear-cut gullies. There was no
significant difference in sediment and total debris recharge rates between gullies in the two
groups, but this outcome was partially a result of the small samples and the different debris
recharge times in each data set. Graphical representations of the data permitted the
identification of possible temporal trends in sediment and debris accumulation, which may
be strengthened with larger data sets.
Debris recharge rates have several applications. The estimate of sediment volume
stored in a gully can be used in the construction of local sediment budgets, as one
component of a watershed sediment cascade is quantified. The calculation of debris
recharge rates will provide insight into the transfer rate of sediment from hillslopes to low
order channels and to the storage capacity of the channels. Finally, debris recharge rates
can be used to improve knowledge of the frequency-magnitude characteristics of debris
torrents in an area. / Arts, Faculty of / Geography, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/5488 |
| Date | 11 1900 |
| Creators | Oden, Marian Elizabeth |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 4315530 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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