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UBC Theses and Dissertations

Bank and slope morphology as an indicator of Arctic terrain stability : (field studies along the rivers and coasts of Banks Island, N.W.T.) Miles, Michael J.

Abstract

Field studies were undertaken on Banks Island, N.W.T., to investigate the. feasibility of using bank or slope morphology as an indicator of the lateral stability of coastal and riverine areas located in regions of permafrost. The study investigated the material characteristics and naturally occurring erosion rates associated with the range of bank or slope forms occurring within the study area. Morphologic features which were studied included repose banks, solifluction slopes, skin flows, retrogressive thaw flow slides, thermo-erosional niches, organic deposits and deflation features. The investigation indicated that the morphology of a bank or slope composed of unlithified sediments is related to the texture and ice content of the associated materials, and to the relative exposure of the site to fluvial or littoral processes of sediment removal. Each morphologic type was found to have a characteristic range of values for each of these parameters. Material genesis was also an important factor as it affects grain size, topographic position and the availability of pore water. Nivation processes, ice wedges, vegetation cover and eolian processes were observed to modify morphology in varying degree. Rates of erosion as determined from field measurements, air photograph interpretation and literature review were found to vary with bank or slope form. Observations on the timing of sediment movement indicate that the peak period of suspended sediment transport occurs during spring snow melt runoff. However sediment production from thermokarst and nivation processes was observed to continue throughout most of the summer. As the post spring peak discharges are generally incompetent to transport this material, significant amounts of within channel sediment storage occur on an annual basis. Thus the seasonal timing of erosion does not directly correspond to the annually observed pattern of suspended sediment transport. The distinctive bank and slope forms identified in this thesis are generally of sufficient size to be identified on existing aerial photography. As each morphologic type was observed to have a typical range in material characteristics and erosion rates, air photograph interpretation of the distribution of these features has practical application in the reconnaissance level analysis of arctic terrain stability.

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