Conclusions
The main interest of this study was to look into the glacially forced topographic anisotropy in BC and to look at the differences between BC and Washington in terms of geomorphic process domains. The plots showed evidence that topographic anisotropy exists, as the BC slope-area plots for the large basins (Figure 14) did not show very obvious process domains while the slope-area plots of the Washington study area (Figure 13) were more clear. This implies that there is something about British Columbia that causes the ‘normal’ slope-area relationship to be altered when plotted on a graph. Due to the fact that I had to use data from the entire drainage basin (not just longitudinal channels), it is very likely that anisotropy is the cause for the difference between BC and Washington. The sidewall processes of the basins probably interfered with the longitudinal processes thus creating a less visually analyzable plot.
The difference between the large basins and the transverse basins in
BC (Figures 14 and 15, respectively) was much less marked than
originally expected. This is probably because I had to use the entire
drainage basin for the transverse plots and because the large basins
(meant to show longitudinal processes) also included all of their
sidewalls. This ended up with the transverse basins looking more like
typical slope-area plots than expected and all falling within the slope
scatter of the large basins.
The two slope-area plots of the stream channels (Figure 11) showed an interesting difference between the hillslope areas above the channel heads. This is perhaps a result of the difference between the cirques of BC and the convex upper hillslopes of Washington. They also showed the important effect of hanging valleys in BC, characterized by large jumps in area values as the stream channel drops into the next valley, which do not show up on the Washington plot.
These results have shown that there are interesting differences in
the slope-area relationships between the glacially carved landscapes of
BC and the fluvially shaped valleys of Washington. However, they show
little about the anisotropic differences within a glacially carved
valley. It is obvious that the topography of the study areas in British
Columbia is still prominently glacial, with fluvial erosion and mass
wasting events creating only a small imprint. The principle of slope
being dependent only on contributing drainage area does not hold, as
the slope angle was created by glaciation. Therefore, using this
principle when creating slope-area plots will create inherent
differences with the final graph. This is especially evident for
hanging glaciers.
Works Cited
Brardinoni, F., and M. A. Hassan. 2006. Glacial erosion, evolution of river long profiles, and the organization of process domains in mountain drainage basins of coastal British Columbia, Journal of Geophysical Research 111, F01013
Canada’s National Climate Archive. <http://www.climate.weatheroffice.gc.ca>
Crosby, B., K. Whipple, C. Wobus, E. Kirby, and D. Sheehan. 2007.
New Tools for Quantitative Geomorphology: Extraction and Interpretation
of Stream Profiles from Digital Topographic Data. GSA Annual Meeting, Boulder, CO.
Istanbulluoglu, E., and R. L. Bras. 2005. Vegetation-modulated landscape evolution: Effects of vegetation on landscape processes, drainage density, and topography, Journal of Geophysical Research 110: F02012
Mitchell, S. D., and D. R. Montgomery. 2006. Influence of a glacial buzzsaw on the height and morphology of the Cascade Range in central Washington State, USA. Quaternary Research 65: 96 – 107
Tucker, G. E., and R. L. Bras. 1998. Hillslope processes, drainage density, and landscape morphology. Water Resources Research 34 (10): 2751–2764
US National Climatic Data Center. <http://www.ncdc.noaa.gov>
Background image from: <http://originalbooner.wordpress.com/2011/10/11/backpacking-to-tenquille-lake-2/>