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Weathering and abrasion of bedrock streambed topography

Brendan P. Murphy, Joel P. L. Johnson, Nicole M. Gasparini, Gregory S. Hancock and Eric E. Small
Weathering and abrasion of bedrock streambed topography
Geology (Boulder) (March 2018) 46 (5): 459-462


Our framework for understanding morphodynamic feedbacks in bedrock rivers is built upon the assumption that rock erodibility is reasonably uniform at the sub-reach scale. Here, we demonstrate that climate-controlled rock weathering combined with bedload abrasion can produce systematic spatial variations in erodibility across bedrock streambed topography. Rock strength data from five channel reaches across the Big Island of Hawai'i show that upstream-oriented rock surfaces are stronger than downstream-oriented surfaces on the same bedrock protrusion. Moreover, the overall strength of these protrusions correlates with local mean annual precipitation rate, demonstrating climatic control of streambed erodibility. Comparing inferred field abrasion rates with experimental flume measurements, we demonstrate that abrasion rates scale exponentially with the orientation of local bed topography relative to streamflow, independent of weathering. However, the spatial variability in abrasion rate across bedrock protrusions is significantly reduced in the field, where large spatial variations in erodibility occur due to weathering. The methods presented here provide a straightforward field-based approach for evaluating the potential influence of weathering on abrasion in bedrock rivers.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 46
Serial Issue: 5
Title: Weathering and abrasion of bedrock streambed topography
Affiliation: Utah State University, Department of Watershed Sciences, Logan, UT, United States
Pages: 459-462
Published: 20180322
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 21
Accession Number: 2018-037159
Categories: Geomorphology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2018154
Illustration Description: illus. incl. geol. sketch map
N20°07'60" - N20°07'60", W155°48'00" - W155°48'00"
Secondary Affiliation: University of Texas at Austin, USA, United StatesTulane University, USA, United StatesCollege of William and Mary, USA, United StatesUniversity of Colorado at Boulder, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201820
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