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Experimental study on coarse grain saltation dynamics in bedrock channels

Chatanantavet, Phairot and Whipple, Kelin X. and Adams, Mark A. and Lamb, Michael P. (2013) Experimental study on coarse grain saltation dynamics in bedrock channels. Journal of Geophysical Research. Earth Surface, 118 (2). pp. 1161-1176. ISSN 2169-9003.

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Saltation of bed load particles on bedrock surfaces is important for landscape evolution and bedrock incision in steep landscapes. However, few studies have investigated saltation in bedrock channels where, unlike alluvial channels, the bed roughness height and the sediment size may be independent. To address this data gap, we measured the saltation hop height, hop length, and velocity of gravel saltating over a planar bed using 80–160 readings from high-speed photography and direct measurements. Two separate dimensional analyses are used: one leading to a bed shear stress scaling and another leading to a Froude number (Fr) scaling. Our new saltation data coupled with numerous data from previous studies suggest that both shear stress and Fr-scaling analyses are valid in characterizing bed load saltation dynamics with bed roughness ranging from smooth to alluvial beds. However, the Fr approach has the advantages that (1) there is no need to estimate a critical Shields stress (τ*_c), which alone can vary up to 2 orders of magnitude (e.g., 0.001–0.1) due to changes in relative bed roughness and slope and (2) the Fr-based scaling fits the saltation data set better in a least squares sense. Results show that the saltation velocity of bed load is independent of grain density and grain size and is linearly proportional to flow velocity. Saltation height has a nonlinear dependence on grain size. Saltation length increases primarily with flow velocity, and it is inversely proportional to submerged specific density. Our results suggest that either (τ*_c) or bed roughness coefficient must be properly estimated to yield accurate results in saltation-abrasion models.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Whipple, Kelin X.0000-0002-8430-6925
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2013 American Geophysical Union. Received 24 April 2012; revised 24 February 2013; accepted 1 March 2013; published 24 June 2013. This work was supported by U.S. NSF funding EAR-0821631 and EAR-0943407 to PI Kelin Whipple as well as EAR-0922199 to PI Michael Lamb. We thank Leonard Sklar, two anonymous reviewers, AE Dimitri Lague, and Editor Alex Densmore for their thorough reviews.
Funding AgencyGrant Number
Subject Keywords:saltation; bedrock river; bed load; steep channel; bed shear stress; Froude number
Issue or Number:2
Record Number:CaltechAUTHORS:20131104-091325592
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Official Citation:Chatanantavet, P., K. X. Whipple, M. Adams, and M. P. Lamb (2013), Experimental study on coarse grain saltation dynamics in bedrock channels, J. Geophys. Res. Earth Surf., 118, 1161–1176, doi:10.1002/jgrf.20053
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42212
Deposited By: Tony Diaz
Deposited On:04 Nov 2013 18:32
Last Modified:09 Mar 2020 13:19

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