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Mechanics of Sediment Transport and Bedrock Erosion in Steep Landscapes


Scheingross, Joel Simon (2016) Mechanics of Sediment Transport and Bedrock Erosion in Steep Landscapes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9B8562B.


Erosion is concentrated in steep landscapes such that, despite accounting for only a small fraction of Earth’s total surface area, these areas regulate the flux of sediment to downstream basins, and their rugged morphology records transient changes (or lack thereof) in geologic and climatic forcing. Steep landscapes are geomorphically active; large sediment fluxes and rapid landscape evolution rates can create or destroy habitat for humans and wildlife alike, and landslides, debris flows, and floods common in mountainous areas represent a persistent natural and structural hazard. Despite the central role that steep landscapes play in the geosciences and in landscape management, the processes controlling their evolution have been poorly studied compared to lower-gradient areas. This thesis focuses on the basic mechanics of sediment transport and bedrock incision in steep landscapes, as these are the fundamental processes which set the pace and style of landscape evolution. Chapter 1 examines the spatial distribution of slow-moving landslides; these landslides can dominate sediment fluxes to river networks, but the controls on their occurrence are poorly understood. Using a case-study along the San Andreas Fault, California, I show that slow-moving landslides preferentially occur near the fault, suggesting a rock-strength control on landslide distribution. Chapter 2 provides the first field-measurements of incipient sediment motion in streams steeper than 14% and shows a large influence of slope-dependent flow hydraulics and grain-scale roughness on particle motion. Chapter 3 presents experimental evidence for bedrock erosion by suspended sediment, suggesting that, in contrast to prevailing theoretical predictions, suspension-regime transport in steep streams can be the dominant erosion agent. Steep streams are often characterized by the presence of waterfalls and bedrock steps which can have locally high rates of erosion; Chapters 4 and 5 present newly developed, experimentally validated theory on sediment transport through and bedrock erosion in waterfall plunge pools. Finally, Chapter 6 explores the formation of a bedrock slot canyon where interactions between sediment transport and bedrock incision lead to the formation of upstream-propagating bedrock step-pools and waterfalls.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Geomorphology, sediment transport, bedrock erosion, waterfalls, landscape evolution
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lamb, Michael P.
Thesis Committee:
  • Avouac, Jean-Philippe (chair)
  • Simons, Mark
  • Thompson, Andrew F.
  • Ampuero, Jean-Paul
  • Lamb, Michael P.
Defense Date:31 August 2015
Funding AgencyGrant Number
Keck Institute for Space StudiesAdvanced Earth Surface Observation Project
National Science FoundationGraduate Research Fellowship
National Science FoundationEAR-1147381
National Aeronautics and Space Administration12PGG120107
Projects:Daniel Y. Lo, SURF 2012, Waterfall plunge pool evolution under constant forcing: A study using low temperature polyurethane foam., Juliane Preimesberger, 2014, The mechanics of river erosion and waterfall formation at steep slopes.
Record Number:CaltechTHESIS:10092015-125804519
Persistent URL:
Related URLs:
URLURL TypeDescription DOIPublished version of Chapter 1 version of Chapter 2 version of Chapter 3
Scheingross, Joel Simon0000-0002-7220-8084
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9208
Deposited By: Joel Scheingross
Deposited On:13 Oct 2015 20:34
Last Modified:04 Oct 2019 00:10

Thesis Files

PDF (Final thesis PDF) - Final Version
Creative Commons Attribution Non-commercial.

[img] Video (MPEG) (Supplementary movie (.mp4) for Chapter 4) - Supplemental Material
Creative Commons Attribution Non-commercial.


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