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Valley Evolution by Meandering Rivers

Citation

Limaye, Ajay Brian Sanjay (2015) Valley Evolution by Meandering Rivers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9MG7MFJ. http://resolver.caltech.edu/CaltechTHESIS:10272014-105243856

Abstract

Fluvial systems form landscapes and sedimentary deposits with a rich hierarchy of structures that extend from grain- to valley scale. Large-scale pattern formation in fluvial systems is commonly attributed to forcing by external factors, including climate change, tectonic uplift, and sea-level change. Yet over geologic timescales, rivers may also develop large-scale erosional and depositional patterns that do not bear on environmental history. This dissertation uses a combination of numerical modeling and topographic analysis to identify and quantify patterns in river valleys that form as a consequence of river meandering alone, under constant external forcing. Chapter 2 identifies a numerical artifact in existing, grid-based models that represent the co-evolution of river channel migration and bank strength over geologic timescales. A new, vector-based technique for bank-material tracking is shown to improve predictions for the evolution of meander belts, floodplains, sedimentary deposits formed by aggrading channels, and bedrock river valleys, particularly when spatial contrasts in bank strength are strong. Chapters 3 and 4 apply this numerical technique to establishing valley topography formed by a vertically incising, meandering river subject to constant external forcing—which should serve as the null hypothesis for valley evolution. In Chapter 3, this scenario is shown to explain a variety of common bedrock river valley types and smaller-scale features within them—including entrenched channels, long-wavelength, arcuate scars in valley walls, and bedrock-cored river terraces. Chapter 4 describes the age and geometric statistics of river terraces formed by meandering with constant external forcing, and compares them to terraces in natural river valleys. The frequency of intrinsic terrace formation by meandering is shown to reflect a characteristic relief-generation timescale, and terrace length is identified as a key criterion for distinguishing these terraces from terraces formed by externally forced pulses of vertical incision. In a separate study, Chapter 5 utilizes image and topographic data from the Mars Reconnaissance Orbiter to quantitatively identify spatial structures in the polar layered deposits of Mars, and identifies sequences of beds, consistently 1-2 meters thick, that have accumulated hundreds of kilometers apart in the north polar layered deposits.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Landscape evolution, river valleys, meandering rivers, river terraces, Mars, stratigraphy, numerical modelinng
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Planetary Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lamb, Michael P.
Thesis Committee:
  • Ingersoll, Andrew P. (chair)
  • Ehlmann, Bethany L.
  • Thompson, Andrew F.
  • Lamb, Michael P.
Defense Date:8 September 2014
Funders:
Funding AgencyGrant Number
Keck Institute for Space Studies Graduate FellowshipUNSPECIFIED
National Defense Science and Engineering Graduate FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:10272014-105243856
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:10272014-105243856
DOI:10.7907/Z9MG7MFJ
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2013JF002854DOIArticle adapted for ch. 2
http://dx.doi.org/10.1002/2013JF002997DOIArticle adapted for ch. 3
http://dx.doi.org/10.1029/2011JE003961DOIArticle adapted for ch. 5
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8713
Collection:CaltechTHESIS
Deposited By: Ajay Limaye
Deposited On:24 Nov 2014 23:50
Last Modified:02 Oct 2017 19:26

Thesis Files

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PDF (Full Thesis. Text and figures) - Final Version
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[img] Plain Text (Description of supplementary movies.) - Supplemental Material
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[img] Video (MPEG) (Supplementary Movie 1 (mp4). Movie based on simulation in Figure 3.) - Supplemental Material
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[img] Video (MPEG) (Supplementary Movie 2 (mp4). Movie based on simulation in Figure 4B, which begins with a partially confined initial alluvial belt (wab* = 0.75).) - Supplemental Material
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[img] Video (MPEG) (Supplementary Movie 3 (mp4). Movie based on simulation in Figure 4C, which begins with an unconfined initial alluvial belt (wab* = °).) - Supplemental Material
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[img] Video (MPEG) (Supplementary Movie 4 (mp4). Movie based on simulation in Figure 5A, which has a low non-dimensional vertical incision rate with sediment banks (EVs* = 0.001).) - Supplemental Material
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3381Kb

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