UBC Theses and Dissertations
Reach-scale contributions of road-surface sediment to the Honna River, Haida Gwaii, B.C. Reid, David A.
Unpaved resource road surfaces may act as dominant sources of fine sediment to streams, yet their relative contribution to in-channel sediment yields remains poorly understood. Significant quantities of road-surface sediment have been observed entering the Honna River, B.C, a 5th order channel located is close proximity to a major, intensively used resource road. In September 2012, a reach of the Honna River was selected for measurement and instrumentation to compile a sediment balance with a focus on the relative importance of road surface sediment over an annual scale. An additional four months of suspended-sediment data were collected at 6 locations in the reach to determine spatial and temporal dynamics of suspended-sediment concentrations and yields. Road surface sediment contributed 19% ± 6% of the total annual fine sediment balance for the reach, even though only ~20% of the road area was an effective sediment source. Persistent clockwise hysteresis was observed in the SSC-discharge relation in the main river channel, but was not as apparent in ditch drainage channels. As a proportion of total input, road surface material ranged from 0.5% to 15% during dry conditions from April to the end of September, and from 5% to 70% in the wet season from October to the end of March. Road surface material appears likely to settle on the river channel bed during low flow conditions, but only temporarily, and in small quantities relative to natural sediment sources. Additional research is needed to assess basin-scale contributions of road surface sediment.
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Attribution-NonCommercial-NoDerivs 2.5 Canada