Oscillations in arid alluvial-channel geometry

Jon Pelletier, Stephen DeLong

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Arid alluvial channels on piedmonts and valley floors often exhibit an oscillating pattern of narrow, deeply incised reaches and wide, shallow reaches with a characteristic wavelength. How do these oscillations develop and what controls their wavelengths? To address these questions we developed a two-dimensional numerical model that couples erosion and deposition in a channel bed with cross-sectional widening and narrowing. This model is inherently unstable over a range of spatial scales dependent on the channel width, depth, and slope. In the initial phase of model evolution, wider-than-average channel reaches become zones of distributary flow that aggrade, lose stream power, and further widen in a positive feedback. Simultaneously, narrower-than-average reaches incise, gain stream power, and further narrow. In the second stage of model evolution, this instability is balanced by the diffusive nature of longitudinal profile evolution, and solitary topographic waves propagate in the upstream direction with a characteristic wavelength and amplitude. The model predicts a specific quantitative relationship between the oscillation wavelength and channel width, depth, and slope that is verified by a database of channel geometries in southern Arizona.

Original languageEnglish (US)
Pages (from-to)713-716
Number of pages4
JournalGeology
Volume32
Issue number8
DOIs
StatePublished - Aug 2004

Fingerprint

oscillation
geometry
wavelength
erosion
valley

Keywords

  • Arizona
  • Arroyo
  • Channel geometry
  • Instability
  • Numerical modeling

ASJC Scopus subject areas

  • Geology

Cite this

Oscillations in arid alluvial-channel geometry. / Pelletier, Jon; DeLong, Stephen.

In: Geology, Vol. 32, No. 8, 08.2004, p. 713-716.

Research output: Contribution to journalArticle

Pelletier, Jon ; DeLong, Stephen. / Oscillations in arid alluvial-channel geometry. In: Geology. 2004 ; Vol. 32, No. 8. pp. 713-716.
@article{07fb0df477c042c3ba32030ac33bbbf1,
title = "Oscillations in arid alluvial-channel geometry",
abstract = "Arid alluvial channels on piedmonts and valley floors often exhibit an oscillating pattern of narrow, deeply incised reaches and wide, shallow reaches with a characteristic wavelength. How do these oscillations develop and what controls their wavelengths? To address these questions we developed a two-dimensional numerical model that couples erosion and deposition in a channel bed with cross-sectional widening and narrowing. This model is inherently unstable over a range of spatial scales dependent on the channel width, depth, and slope. In the initial phase of model evolution, wider-than-average channel reaches become zones of distributary flow that aggrade, lose stream power, and further widen in a positive feedback. Simultaneously, narrower-than-average reaches incise, gain stream power, and further narrow. In the second stage of model evolution, this instability is balanced by the diffusive nature of longitudinal profile evolution, and solitary topographic waves propagate in the upstream direction with a characteristic wavelength and amplitude. The model predicts a specific quantitative relationship between the oscillation wavelength and channel width, depth, and slope that is verified by a database of channel geometries in southern Arizona.",
keywords = "Arizona, Arroyo, Channel geometry, Instability, Numerical modeling",
author = "Jon Pelletier and Stephen DeLong",
year = "2004",
month = "8",
doi = "10.1130/G20512.1",
language = "English (US)",
volume = "32",
pages = "713--716",
journal = "Geology",
issn = "0091-7613",
publisher = "Geological Society of America",
number = "8",

}

TY - JOUR

T1 - Oscillations in arid alluvial-channel geometry

AU - Pelletier, Jon

AU - DeLong, Stephen

PY - 2004/8

Y1 - 2004/8

N2 - Arid alluvial channels on piedmonts and valley floors often exhibit an oscillating pattern of narrow, deeply incised reaches and wide, shallow reaches with a characteristic wavelength. How do these oscillations develop and what controls their wavelengths? To address these questions we developed a two-dimensional numerical model that couples erosion and deposition in a channel bed with cross-sectional widening and narrowing. This model is inherently unstable over a range of spatial scales dependent on the channel width, depth, and slope. In the initial phase of model evolution, wider-than-average channel reaches become zones of distributary flow that aggrade, lose stream power, and further widen in a positive feedback. Simultaneously, narrower-than-average reaches incise, gain stream power, and further narrow. In the second stage of model evolution, this instability is balanced by the diffusive nature of longitudinal profile evolution, and solitary topographic waves propagate in the upstream direction with a characteristic wavelength and amplitude. The model predicts a specific quantitative relationship between the oscillation wavelength and channel width, depth, and slope that is verified by a database of channel geometries in southern Arizona.

AB - Arid alluvial channels on piedmonts and valley floors often exhibit an oscillating pattern of narrow, deeply incised reaches and wide, shallow reaches with a characteristic wavelength. How do these oscillations develop and what controls their wavelengths? To address these questions we developed a two-dimensional numerical model that couples erosion and deposition in a channel bed with cross-sectional widening and narrowing. This model is inherently unstable over a range of spatial scales dependent on the channel width, depth, and slope. In the initial phase of model evolution, wider-than-average channel reaches become zones of distributary flow that aggrade, lose stream power, and further widen in a positive feedback. Simultaneously, narrower-than-average reaches incise, gain stream power, and further narrow. In the second stage of model evolution, this instability is balanced by the diffusive nature of longitudinal profile evolution, and solitary topographic waves propagate in the upstream direction with a characteristic wavelength and amplitude. The model predicts a specific quantitative relationship between the oscillation wavelength and channel width, depth, and slope that is verified by a database of channel geometries in southern Arizona.

KW - Arizona

KW - Arroyo

KW - Channel geometry

KW - Instability

KW - Numerical modeling

UR - http://www.scopus.com/inward/record.url?scp=4344609128&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4344609128&partnerID=8YFLogxK

U2 - 10.1130/G20512.1

DO - 10.1130/G20512.1

M3 - Article

AN - SCOPUS:4344609128

VL - 32

SP - 713

EP - 716

JO - Geology

JF - Geology

SN - 0091-7613

IS - 8

ER -