Document Type
Article
Department/Program
Geology
Journal Title
Earth Surface Processes and Landforms
Pub Date
Fall 10-2-2017
Volume
42
Issue
13
First Page
1997
Abstract
Erosion processes in bedrock-floored rivers shape channel cross-sectional geometry and the broader landscape. However, the influence of weathering on channel slope and geometry is not well understood. Weathering can produce variation in rock erodibility within channel cross-sections. Recent numerical modeling results suggest that weathering may preferentially weaken rock on channel banks relative to the thalweg, strongly influencing channel form. Here, we present the first quantitative field study of differential weathering across channel cross-sections. We hypothesize that average cross-section erosion rate controls the magnitude of this contrast in weathering between the banks and the thalweg. Erosion rate, in turn, is moderated by the extent to which weathering processes increase bedrock erodibility. We test these hypotheses on tributaries to the Potomac River, Virginia, with inferred erosion rates from similar to 0.1m/kyr to >0.8m/kyr, with higher rates in knickpoints spawned by the migratory Great Falls knickzone. We selected nine channel cross-sections on three tributaries spanning the full range of erosion rates, and at multiple flow heights we measured (1) rock compressive strength using a Schmidt hammer, (2) rock surface roughness using a contour gage combined with automated photograph analysis, and (3) crack density (crack length/area) at three cross-sections on one channel. All cross-sections showed significant (p
Recommended Citation
Shobe, Charles M.; Hancock, Gregory S.; Eppes, Martha C.; and Small, Eric E., Field evidence for the influence of weathering on rock erodibility and channel form in bedrock rivers (2017). Earth Surface Processes and Landforms, 42(13), 1997-2012.
10.1002/esp.4163
DOI
10.1002/esp.4163
Associated Materials
Link to supplemental data zip file for Data S1. Supporting info item below.
