Bedload transport in a meltwater stream, Miers Valley, Antarctica: controls and prediction

Bedload transport rates in a meltwater stream in the Miers Valley of Antarctica are highly variable. The major control on the transport of the predominantly sand-sized material is the energy available as a function of discharge; however, the relationship is neither simple nor constant. Change in dis...

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Bibliographic Details
Published in:Journal of hydrology, New Zealand New Zealand, 2001-01, Vol.40 (1), p.1-18
Main Authors: Hawke, R.M., McConchie, J.A.
Format: Article
Language:English
Subjects:
Antarctic regions
Bedforms
Earth sciences
Earth, ocean, space
Exact sciences and technology
Flow velocity
Fluvial transport
Glaciers
Hydrology
Hydrology. Hydrogeology
Sand
Sediment transport
Sediments
Streams
Valleys
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Summary:Bedload transport rates in a meltwater stream in the Miers Valley of Antarctica are highly variable. The major control on the transport of the predominantly sand-sized material is the energy available as a function of discharge; however, the relationship is neither simple nor constant. Change in discharge was able to explain 85% of the variation in bedload transport rates at a site where intensive sampling was undertaken over two 12-hour periods. At discharges below approximately 2401 s⁻¹ bedload transport rates vary as a simple power function of discharge. At greater discharges the relationship becomes less regular. The bedform changes from ripples to sand waves and dunes and, as these migrate past the sampling site, they cause wide fluctuations in bedload flux. The higher velocities also exceed the erosion threshold of the sands that make up the banks, leading to undercutting and bank collapse if the ice "cementing" the sands thaws. This results in random pulses of sediment which cause further variation in the actual transport rates. Bagnold's equation, although it predicted the general trend in bedload transport, does not work well in an absolute sense, even in this relatively simple study reach. It under-estimates bedload transport rates by a factor of five. However, once "corrected" for depth and grain size a transport equation based on excess stream power could explain 90% of the variation in the measured bedload transport rate. The slope of this relationship is consistent with that previously reported.
ISSN:0022-1708
2463-3933