Post-dam removal geomorphologic adjustment of a stream channel has been documented in the scientific literature at watershed, hillslope, and laboratory scales. Hillslope-scale studies in channel cross sections are most common and add significant value in the dam-removal literature. This study examines geomorphic stream channel adjustment following dam removal at the hillslope scale under natural climatic conditions. A sedimentfilled silt fence dam (1 m tall, 12.65 m wide) was removed in three stages, and the width and depth of the upstream developing channel was monitored at six transects for 15 months. Headcut retreat and changes in channel sinuosity were also recorded. After the silt fence dam was removed, channel development was initiated by headcut formation, which migrated upstream at a rate of 4 cm/d for about 10 months and then gradually reached attenuation. The channel progressed through four distinct stages: Stage 1 (Initial conditions); Stage 2 (Downcutting)-wide, shallow, meandering channel incised to a maximum depth of 0.52 m, and sinuosity decreased; Stage 3 (Floodplain development)-upon reaching base level, surface runoff began to meander within the channel, widening it through bank slumps and erosion; and Stage 4 (Quasi-equilibrium)-channel development reached dynamic (quasi-) equilibrium with only minor widening at downstream transects (maximum width of the incised channel reached 0.46 m), accompanied by sediment aggradation. The stages of upstream channel development and headcut retreat pattern in this study are consistent with the findings of other studies at the laboratory and watershed scales, indicating that channel development after dam removal is scale independent.

In 1977, this study was carried out in a small drainage basin (33 km2) near Resolute (74°55'N, 94°50'W), Northwest Territories (1) to examine the manner in which meltwater runoff carves channels in the valley snowpack before the channels become stablised on their clastic beds, and (2) to assess the role played by valley snowpacks on fluvial processes. Major factors controlling channel development in the snowpack include the distribution and the characteristics of the snow, which in turn are related to the local topography and the prevailing directions of winter snowdrift. Based on this relationship, an attempt was made to predict the sequences of channel development in terms of several processes including ponding, tunnelling, lateral and vertical shifting, and stream capturing. Availability of water controls the rate of channel development sequences and hence the magnitude of fluvial processes over a flow season. In the case of substantial runoff, the rate of snowpack depletion is rapid. However, since the bulk of annual water discharge occurs while the snow is interposed between the running water and the bed material, little geomorphic work is performed during the early part of the flow season. For four selected sites, calculations suggest a protective effect of the snow in reducing the potential bed material transport. / Thesis / Master of Science (MSc)