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Assessing grain-size correspondence between flow and deposits of controlled floods in the Colorado River, USA

Journal of Sedimentary Research

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DOI: 10.2110/jsr.2013.79

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Abstract

Flood-deposited sediment has been used to decipher environmental parameters such as variability in watershed sediment supply, paleoflood hydrology, and channel morphology. It is not well known, however, how accurately the deposits reflect sedimentary processes within the flow, and hence what sampling intensity is needed to decipher records of recent or long-past conditions. We examine these problems using deposits from dam-regulated floods in the Colorado River corridor through Marble Canyon–Grand Canyon, Arizona, U.S.A., in which steady-peaked floods represent a simple end-member case. For these simple floods, most deposits show inverse grading that reflects coarsening suspended sediment (a result of fine-sediment-supply limitation), but there is enough eddy-scale variability that some profiles show normal grading that did not reflect grain-size evolution in the flow as a whole. To infer systemwide grain-size evolution in modern or ancient depositional systems requires sampling enough deposit profiles that the standard error of the mean of grain-size-change measurements becomes small relative to the magnitude of observed changes. For simple, steady-peaked floods, 5–10 profiles or fewer may suffice to characterize grain-size trends robustly, but many more samples may be needed from deposits with greater variability in their grain-size evolution.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Assessing grain-size correspondence between flow and deposits of controlled floods in the Colorado River, USA
Series title:
Journal of Sedimentary Research
DOI:
10.2110/jsr.2013.79
Volume
83
Issue:
11
Year Published:
2013
Language:
English
Publisher:
Society for Sedimentary Geology
Description:
12 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
962
Last page:
973
Number of Pages:
12