UBC Theses and Dissertations
Sediment transport and storage in urban streams McIntyre, Amy
Sediment pulses into gravel-bed rivers in mountainous basins, such as those found throughout BC, Canada, can alter river systems. Pulses are generated through hillslope erosion, landslides, and debris flows. Human activity such as mining and logging can increase the frequency and magnitude of these events. There is research regarding impacts of increased streamflow on urban river systems, however, there is relatively little research on the impact of increased sediment. Knowing how urban stream channels respond to sediment pulses can help guide stream management and restoration projects. Experiments were conducted using a generic physical model of a gravel bed stream at the University of British Columbia. Three physical model configurations were used: a model of a channelized urban stream; a model of a channelized urban stream with a widened central reach representing a restoration technique; and an urban stream with a widened reach has been reenforced with a layer stabilizing grains on the floodplain surface. Two main experiments were conducted on each configuration, one where sediment was kept constant and a second where sediment pulses were introduced to the channel. Overall, sediment pulses into urban streams result in increased bed elevation and channel flooding localized to the upstream area. The urban channelized stream was resilient to a 25% pulse, whilst widening a reach reduced sediment transport and was unable to cope with any sediment increase. This demonstrates that bank protection would need to be introduced to prevent aggradation even at the background sediment supply rate. The use of additional bank protection increased the resilience of the restored channel to sediment pulses by increasing sediment transport. However, this set up flooded at the 25% pulse. Even with mitigation, the fully channelized urban streams are most resilient to increases in sediment supply.
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