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Clastic sediment sources and suspended sediment yield in a Coast Mountain watershed, British Columbia

University of British Columbia

This dissertation investigates the clastic sediment sources and suspended sediment yields of clear-cut and undisturbed areas of a glacially- -modified, 33 km² watershed in the southern Coast Mountains of British Columbia. Surficial materials were mapped and the character of sediment movement interpreted by morphologic evidence. Basin sediment yields through snowmelt, summer low flow and fall storm periods were related to the magnitude of precipitation inputs, storage changes of snow and the availability of clastic sediment to the channel system. In the undisturbed area sediment activated along steep tributary streams of the till-mantled valley walls below treeline was considered most important to basin scale yield. In the alpine zone mass wastage activity is widespread yet effects mainly a redistribution of materials on slopes; sediment supply to the fluvial system is limited by the extensive presence of coarse materials and the lower drainage density. Snowmelt period sediment export exceeded that during summer low flow and October storm periods; however, approximately 60 percent of the total sediment yield observed took place during a November rain-on-snow event of an estimated 10 year recurrence interval. During the October storm period, when sediment yields from the forested and clear-cut slopes could be isolated, sediment removal from the clear-cut slope was greater by approximately eight times and this accelerated erosion was attributed almost entirely to road effects.

Text

2010-03-17

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http://hdl.handle.net/2429/22002

Geography

University of British Columbia

Graduate