Bedrock-controlled Fluvial Geomorphology and the Hydraulics of Rapids on the Colorado River

Persistent Link:
http://hdl.handle.net/10150/193919
Title:
Bedrock-controlled Fluvial Geomorphology and the Hydraulics of Rapids on the Colorado River
Author:
Magirl, Christopher Sean
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The fluvial geomorphology of the Colorado River cutting across the Colorado Plateau in the western United States is bedrock controlled and largely governed by rapids. Rapids on the Colorado River control the water-surface profile and influence the bathymetry, the storage of sand, and the aquatic ecology. Despite their importance, little data on the hydraulics, sediment transport, and long-term stability of rapids have been collected. By comparing water-surface profiles, the average rate of aggradation at the head of 91 rapids in Grand Canyon between 1923 and 2000 was calculated to be 0.26 ± 0.15 m. In addition, while in 1923, 50% of the cumulative drop through the river corridor occurred in just 9% of the distance, by 2000, the cumulative drop over the same distance increased to 66%. A new hydraulic model, incorporating one-dimensional step-backwater theory, was constructed for the Colorado River in Grand Canyon. The model includes 2,690 cross sections and simulates discharge up to 5,600 m³/s, offering the opportunity to simulate large floods, rare under the current regulated flow regime. Flow velocities were measured directly in rapids using three separate flow measurement instruments. An acoustic Doppler velocimeter (ADV) was used to measure velocity in five Grand Canyon rapids. While the instrument was able to measure velocity in three dimensions up to 3.0 m/s, limitations rendered data unusable for flow above 3.0 m/s. An acoustic Doppler current profiler (ADCP) was used to measure the flow field in rapids throughout the water column in Cataract Canyon. The peak average velocity measured by the ADCP was roughly 4.0 m/s. Similarly, average flow velocity of 5.2 m/s was measured in a Cataract Canyon rapid using a pitot-static tube. The pitot-static tube measured instantaneous flow velocities up to 6.5 m/s, one of the fastest velocity measurements made in a river. Using the combination of the ADCP and pitot-static tube, the flow structure and nature of turbulence within rapids were analyzed. Finally, techniques were developed to enable the measurement and construction of detailed water surface, shoreline, and bathymetric maps directly in rapids on the Colorado River.
Type:
text; Electronic Dissertation
Keywords:
Geomorphology; Rapids; Flow Measurement; Colorado River; Grand Canyon
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Hydrology; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Baker, Victor R.
Committee Chair:
Baker, Victor R.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleBedrock-controlled Fluvial Geomorphology and the Hydraulics of Rapids on the Colorado Riveren_US
dc.creatorMagirl, Christopher Seanen_US
dc.contributor.authorMagirl, Christopher Seanen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe fluvial geomorphology of the Colorado River cutting across the Colorado Plateau in the western United States is bedrock controlled and largely governed by rapids. Rapids on the Colorado River control the water-surface profile and influence the bathymetry, the storage of sand, and the aquatic ecology. Despite their importance, little data on the hydraulics, sediment transport, and long-term stability of rapids have been collected. By comparing water-surface profiles, the average rate of aggradation at the head of 91 rapids in Grand Canyon between 1923 and 2000 was calculated to be 0.26 ± 0.15 m. In addition, while in 1923, 50% of the cumulative drop through the river corridor occurred in just 9% of the distance, by 2000, the cumulative drop over the same distance increased to 66%. A new hydraulic model, incorporating one-dimensional step-backwater theory, was constructed for the Colorado River in Grand Canyon. The model includes 2,690 cross sections and simulates discharge up to 5,600 m³/s, offering the opportunity to simulate large floods, rare under the current regulated flow regime. Flow velocities were measured directly in rapids using three separate flow measurement instruments. An acoustic Doppler velocimeter (ADV) was used to measure velocity in five Grand Canyon rapids. While the instrument was able to measure velocity in three dimensions up to 3.0 m/s, limitations rendered data unusable for flow above 3.0 m/s. An acoustic Doppler current profiler (ADCP) was used to measure the flow field in rapids throughout the water column in Cataract Canyon. The peak average velocity measured by the ADCP was roughly 4.0 m/s. Similarly, average flow velocity of 5.2 m/s was measured in a Cataract Canyon rapid using a pitot-static tube. The pitot-static tube measured instantaneous flow velocities up to 6.5 m/s, one of the fastest velocity measurements made in a river. Using the combination of the ADCP and pitot-static tube, the flow structure and nature of turbulence within rapids were analyzed. Finally, techniques were developed to enable the measurement and construction of detailed water surface, shoreline, and bathymetric maps directly in rapids on the Colorado River.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectGeomorphologyen_US
dc.subjectRapidsen_US
dc.subjectFlow Measurementen_US
dc.subjectColorado Riveren_US
dc.subjectGrand Canyonen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineHydrologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBaker, Victor R.en_US
dc.contributor.chairBaker, Victor R.en_US
dc.contributor.committeememberWebb, Robert H.en_US
dc.contributor.committeememberDeCelles, Peter G.en_US
dc.contributor.committeememberLansey, Kevin E.en_US
dc.contributor.committeememberPelletier, Jon D.en_US
dc.identifier.proquest1885en_US
dc.identifier.oclc659746444en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.