WSP12655

• File Number: 8220.101.10.B
• Description: Colorado River - Water Projects - Glen Canyon Dam-Lake Powell - Glen Canyon TWG
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/2004
• Author: Schmidt - Topping - Grams - Hazel
• Title: System-Wide Changes in the Distribution of Fine Sediment in the Colorado River Corridor Between Glen Canyon Dam and Bright Angel Creek - Arizona - Final Report - 10-01-04
• Water Supply Pro - Doc Type: Report/Study

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Contents

Abstract
1.0 Introduction. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 The Importance of a Comprehensive History of Geomorphic Change. . . . . . 3
Water and Fine-Sediment Fluxes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3
The Valley of the Colorado River. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7
3.1 Longitudinal Profile and Bed-Material Distribution. . . . . . . . . . . . . . .. 10
3.2 The Fan-Eddy Complex. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
3.2.1 Longitudinal Distribution of Eddy Deposition Zones. . . . . . . . . . 15
3.3 Sedimentology of Fine-Grain Alluvial Deposits. . . . . . . . . . . . . . . . . .. 18
Previous Studies in Fine-Sediment Flux and Storage. . . . . . . . . . . . . . . . . . . . .. 20
4.1 Previous Projections of Long- Term Changes in the Fine-Sediment Budget. . . . . . 21
Changes in the Topography of the Main-Channel Bed. . . . . . . . . . . . . . . . . . .. . 23
5.1 Pre-dam Changes in the Main-Channel Bed, as Measured at the Lees Ferry and
Grand Canyon Gages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Post-Dam Changes of the Bed in Glen Canyon. . . . . . . . . . . . . . . . . .
5.2.1 Rate and Magnitude of Degradation . . . . . . . . . . . . . . . . . . . . .
Post-dam Changes in the Bed in Marble and Upper Grand Canyons. . . . . . . . .
5.3.1 Bed Changes in Marble and Grand Canyons That Are Probably Post-dam.
5.3.2 Changes at the Grand Canyon Gage between 1963 and 2000 and at the
Lower Marble Canyon Gage between 1983 and 2000. . . . . . . . . . .
5.3.3 Changes in Main Channel Pools Offshore from Eddies between 1992 and

2000. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The History of Fine Sediment Storage at Specific Sites. . . . . . . . . . . . . . . .
6.1 Badger Creek Rapids. . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 Eminence Break Camp. . . . . . . . . . . . . . . . . . . . . . . . . .
Long-Term Changes in Fine Sediment Storage Shown by Comparison of Oblique
Photographs. . . . . . . . . . . . . . . . . . . . . . . . . . 61
7.1 Previous Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
7.2 Methods and Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
7.2.1 Description of change depicted in some of the photographs . . . . . . .. 63
Changes in the Area of Fine-Grained Alluvial Deposits Determine by Aerial Photography
Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8.1 Methods............ . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8.1.1 Accuracy of mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . 72
8.1.2 Metrics used to describe changes in fine-grain deposits among years. . . . 74
Description of the Photograph Series That Were Analyzed. . . . . . . . . . . . . . . 75
8.2.1 Pre-dam conditions of the mid-1930s, 1952, 1954, 1956, 1958. . . . . . . . 75
8.2.2 Pulsed high releases of May 1965. . . . . . . . . . . . . . . . . . . . . . . . 75
8.2.3 Fluctuating flows of June 1973. . . . . . . . . . . . . . . . . . . . . . . . . 75
8.2.4 Bypass and spillway floods of the mid-1980s: October 1984. . . . . . . . . 76
8.2.5 Resumption of wide-ranging hydroelectricity-generating flows: June

1990. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Interim operating criteria: October 1992, May 1993, and March 1996. . . . 76
Effects of the 1996 Controlled Flood: April 1996. . . . . . . . . . . . . . . 76
Changes in bars after the 1996 Controlled Flood: September 1996 and
September 1997. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Changes in the Area of Fine-Grained Alluvial Deposits Determined by Aerial
Photograph Analysis' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
8.3.1 Changes in eddy bars. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 77

2.0
3.0

4.0

5.0

"""",\

5.2

. 23
25
31
32
33

5.3

34

6.0

. 35
. 37
. 42
. 49

7.0

8.0

8.2

8.2.6
8.2.7
8.2.8

76

8.3

Contents III