Division of Science and Technology, Department of Geography, Tamaki Campus, University of Auckland, Private Bag 29019, Auckland, New Zealand.
Flow and sediment transport over large subaqueous dunes: Fraser River, Canada
Version of Record online: 14 JUN 2006
Volume 43, Issue 5, pages 849–863, October 1996
How to Cite
KOSTASCHUK, R. and VILLARD, P. (1996), Flow and sediment transport over large subaqueous dunes: Fraser River, Canada. Sedimentology, 43: 849–863. doi: 10.1111/j.1365-3091.1996.tb01506.x
- Issue online: 14 JUN 2006
- Version of Record online: 14 JUN 2006
- Manuscript received 7 July 1995; revision accepted 13 February 1996.
Large symmetric and asymmetric dunes occur in the Fraser River, Canada. Symmetric dunes have stoss and lee sides of similar length, stoss and lee slope angles <8°, and rounded crests. Asymmetric dunes have superimposed small dunes on stoss sides, sharp crests, stoss sides longer than lee sides, stoss side slopes <3° and straight lee side slopes up to 19°. There is no evidence for lee side flow separation, although intermittent separated flow is possible, especially over asymmetric dunes. Dune symmetry and crest rounding of symmetric dunes are associated with high sediment transport rates. High near-bed velocity and bed load transport near dune crests result in crest rounding. Long, low-angle lee sides are produced by deposition of suspended sediment in dune troughs. Asymmetric dunes appear to be transitional features between large symmetric dunes and smaller dunes adjusted to lower flow velocity and sediment transport conditions. Small dunes on stoss sides reduce near-bed flow velocity and bed load transport, causing a sharper dune crest. Reduced deposition of suspended sediment in troughs results in a short, steep lee slope. Dunes in the Fraser River fall into upper plane bed or antidune stability fields on flume-based bedform phase diagrams. These diagrams are probably not applicable to large dunes in deep natural flows and care must be taken in modelling procedures that use phase diagram relations to predict bed configuration in such flows.