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Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes

DiBiase, Roman A. and Lamb, Michael P. and Ganti, Vamsi and Booth, Adam M. (2017) Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes. Journal of Geophysical Research. Earth Surface, 122 (4). pp. 941-960. ISSN 2169-9003.

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Existing hillslope sediment transport models developed for low-relief, soil-mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels. Here we address this knowledge gap using a series of field and numerical experiments to inform a particle-based model of sediment transport by dry ravel—a mechanism of granular transport characteristic of steep hillslopes. We find that particle travel distance increases as a function of the ratio of particle diameter to fine-scale (<1 m) topographic roughness, in agreement with prior laboratory and field experiments. Contrary to models that assume a fixed critical slope, the particle-based model predicts a broad transition as hillslopes steepen from grain-scale to hillslope-scale mean particle travel distances due to the trapping of sediment on slopes more than threefold steeper than the average friction slope. This transition is further broadened by higher macroscale (>1 m) topographic variability associated with rocky landscapes. Applying a 2-D dry-ravel-routing model to lidar-derived surface topography, we show how spatial patterns of local and nonlocal transport control connectivity between hillslopes and steep headwater channels that generate debris flows through failure of ravel-filled channels following wildfire. Our results corroborate field observations of a patchy transition from soil-mantled to bedrock landscapes and suggest that there is a dynamic interplay between sediment storage, roughness, grain sorting, and transport even on hillslopes that well exceed the angle of repose.

Item Type:Article
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Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2017 American Geophysical Union. Received 26 MAY 2016; Accepted 23 MAR 2017; Accepted article online 26 MAR 2017; Published online 20 APR 2017. This work was supported by funding from a Davidow Foundation grant to M.P.L. Laser altimetry data were acquired and processed by the National Center for Airborne Laser Mapping (NCALM) with support from the California Institute of Technology, Arizona State University, and the U.S. Geological Survey. V.G. acknowledges support from the Imperial College London Junior Research Fellowship. We thank Fanny Brun, Phairot Chatanantavet, Zhongxin Chu, Mathieu Lapotre, Jeff Prancevic, and Joel Scheingross for assistance with fieldwork. Thorough and constructive comments from Manny Gabet, two anonymous reviewers, Associate Editor Jason Kean, and Editor John Buffington greatly improved the manuscript. All data, including MATLAB scripts for generating figures, are included in the supporting information available online.
Funding AgencyGrant Number
Davidow FoundationUNSPECIFIED
Imperial College LondonUNSPECIFIED
Subject Keywords:dry ravel; nonlocal transport; steep hillslopes; postwildfire debris flows; topographic roughness
Issue or Number:4
Record Number:CaltechAUTHORS:20170601-085108736
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Official Citation:DiBiase, R. A., M. P. Lamb, V. Ganti, and A. M. Booth (2017), Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes, J. Geophys. Res. Earth Surf., 122, 941–960, doi:10.1002/2016JF003970
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:77884
Deposited By: Tony Diaz
Deposited On:12 Jun 2017 16:23
Last Modified:03 Oct 2019 18:02

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