IV    Report Title

Sandbar Response in Marble and Grand Canyons, Arizona,

Following the 2008 High-Flow Experiment on the

Colorado River

Scientific Investigation Report 2010–5015

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with Northern Arizona University and Utah State University
COVER:

View looking south (downstream) of the Colorado River and the sandbar at Carbon Canyon (study site 65R in Eastern Grand Canyon) on April 4, 2008. 

Discharge at the time was about 368 m3

/s. (Photograph by J.E. Hazel, Jr.)
Prepared in cooperation with Northern Arizona University and Utah State University

Sandbar Response in Marble and Grand 

Canyons, Arizona, Following the 2008 

High-Flow Experiment on the Colorado River

By Joseph E. Hazel, Jr., Paul E. Grams, John C. Schmidt, and Matt Kaplinski

Scientific Investigations Report 2010–5051

U.S. Department of the Interior

U.S. Geological Survey
Cataloging-in-publication data are on file with the Library of Congress (URL http://www.loc.gov/).

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia 2010

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Suggested citation: 

Hazel, J.E., J r., Grams, P.E., Schmidt, J.C., and Kaplinski, M., 2010, Sandbar response in Marble and Grand 

Canyons, Arizona, following the 2008 high-flow experiment on the Colorado River: U.S. Geological Survey 

Scientific Investigations Report 2010–5015, 52 p.

This report and any updates to it are available online at:

http://pubs.usgs.gov/sir/2010/5015/
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Physical Setting..............................................................................................................................................3

Units, Place Names, and Study Area ................................................................................................3

The Fan-Eddy Complex.........................................................................................................................3

Controlled Floods, Tributary Sand Inputs, and Fluctuating Flows..........................................................5

Methods...........................................................................................................................................................8

Results ...........................................................................................................................................................11

Overview of Topographic Response................................................................................................11

Styles of Topographic Response......................................................................................................11

Style 1 .........................................................................................................................................12

Style 2 With Net Eddy Erosion ................................................................................................12

Style 2 With Net Eddy Deposition ...........................................................................................14

Style 3 .........................................................................................................................................14

Spatial Pattern of Topographic Response ......................................................................................19

Longevity: Changes from April to October 2008.............................................................................21

Campsite Area.....................................................................................................................................23

Comparison of Three High-Flow Experiments: 1996, 2004, and 2008..........................................28

Discussion and Conclusions......................................................................................................................29

Acknowledgements.....................................................................................................................................35

References Cited..........................................................................................................................................36

Appendix A. Summary of study sites and types of data collected, Colorado River in Marble 

 and Grand Canyons.......................................................................................................................40

Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble 

 and Grand Canyons.......................................................................................................................46

Figures

1. The Colorado River and Grand Canyon National Park, between Lake Powell and 

Lake Mead reservoirs.............................................................................................................2

2. Geomorphic description of physical setting and boundary definitions for 

fan-eddy complexes of the Colorado River.........................................................................4

3. Instantaneous discharge of the Colorado River at USGS streamflow-gaging 

station (09380000), Lees Ferry, Arizona, for the 2008 calendar year...............................9

4. Histograms of net sandbar thickness change between February and April 2008 ...............13

5. Relation of proportional sand-volume change above reference stage 

for each site between February and April 2008 ...............................................................14

6. Comparison of repeat topographic and bathymetric surveys collected 

at site 172L illustrating Style 1 site response....................................................................15

7. Selected daily photographs of the reattachment bar at site 172L..........................................16
iv

8. Areal and volumetric elevation-change distributions from the erosion-deposition

 map at site 172L shown in figure 6C..................................................................................16

9. Comparison of repeat topographic and bathymetric surveys collected 

at site 44L illustrating a Style 2 sandbar response ..........................................................17

10. Selected daily photographs of the sandbars at site 44L ........................................................18

11. Areal and volumetric elevation-change distributions from the erosion-deposition 

map at site 44L shown in figure 9C.....................................................................................19

12. Comparison of repeat topographic and bathymetric surveys collected

 at 65R illustrating a variant of Style 2 response..............................................................20

13. Selected daily photographs of the reattachment bar at site 65R .........................................21

14. Areal and volumetric elevation-change distributions from the 

erosion-deposition map at site 65R shown in figure 12C................................................24

15. Comparison of repeat topographic and bathymetric surveys collected at site 3L............25

16. Selected daily photographs of the reattachment bar at site 3L............................................26

17. Areal and volumetric elevation-change distributions from the 

erosion-deposition map at site 3L shown in figure 15C ..................................................26

18. Downstream variations at study sites and sediment-transport-flux 

monitoring reaches in response to 2008 HFE ...................................................................27

19. Photographic sequence at site 68R showing rapid erosion following 

the change in fluctuating flow regime at Glen Canyon Dam 

on April 15, 2008.....................................................................................................................28

20. Boxplot showing temporal sequence of deposit thickness above

 the reference stage compared to daily mean discharge following the 2008 HFE.....29

21. Histograms showing the distribution of campsite area above the

 reference stage ....................................................................................................................30

22. Average campsite area above the reference stage 

before, after, and about 6 months after the 2008 HFE......................................................31

23. The relation of change in campsite area to change in sandbar area 

and volume for two time intervals in 2008, pre- to postflood 

(February-April) and the following 6 months (April-October) ........................................31

24. Cumulative probability distributions of total-site sand volume following 

the 1996, 2004, and 2008 HFEs..............................................................................................32

25. Boxplots showing normalized sand volumes of all sites within each 

sediment-transport-flux monitoring reach........................................................................33

26. Cumulative probability distributions of sand volume above reference 

stage following the 1996, 2004, and 2008 HFEs.................................................................34
v

Tables

 

1. Channel geometry and geomorphic characteristics for selected study sites, Colorado

River in Marble and Grand Canyons .................................................................... 6

2. Sediment-transport-flux monitoring stations and reaches of the Colorado River 

used to compare the 1996, 2004, and 2008 HFEs.............................................................11

3. Critical and noncritical recreational campsite reaches

 of the Colorado River........................................................ ...................................................12

4. Observations of erosion and deposition from repeat photography 

at sites along the Colorado River in Marble and Grand Canyons................................22

Table B1. High-elevation-zone area and volume at four measurement times in 2008

 at each study site................................................................................................................46

Table B2. Midelevation zone area and volume at four measurement times in 2008 

 at each study site................................................................................................................48

Table B3. Low-elevation-zone eddy area and volume, and main-channel volume 

 at four measurement times in 2008 at each study site .................................................50

Table B4. Midelevation zone and high-elevation-zone campsite area measured 

 at four measurement times in 2008 at each study site .................................................52
vi

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

 Length

mile (mi) 1.609 kilometer (km)

SI to Inch/Pound

Multiply By To obtain

 Length

meter (m) 3.281 foot (ft) 

 Area

square meter (m2

) 10.76 square foot (ft2) 

 Volume

cubic meter (m3

) 35.31 cubic foot (ft3)

Mass 

metric ton (t) 1.102 ton (2,000 lb)

 Flow rate

cubic meter per second (m3

/s) 35.31 cubic foot per second (ft3/s)

In this report, horizontal and vertical coordinate information is referenced in meters above 

the GRS80 ellipse defined by the North American Datum of 1983 (NAD 83). Elevation, as used 

in this report, refers to NAD83/GRS80 ellipsoid heights and not traditionally defined NAVD88 

orthometric heights.
Sandbar Response in Marble and Grand Canyons, Arizona, 

Following the 2008 High-Flow Experiment on the Colorado 

River

Abstract

A 60-hour release of water at 1,203 cubic meters 

per second (m3/s) from Glen Canyon Dam in March 2008 

provided an opportunity to analyze channel-margin response 

at discharge levels above the normal, diurnally fluctuating 

releases for hydropower plant operations. We compare measurements at sandbars and associated campsites along the 

mainstem Colorado River, downstream from Glen Canyon 

Dam, at 57 locations in Marble and Grand Canyons. Sandbar 

and main-channel response to the 2008 high-flow experiment (2008 HFE) was documented by measuring bar and bed 

topography at the study sites before and after the controlled 

flood and twice more in the following 6 months to examine the 

persistence of flood-formed deposits. The 2008 HFE caused 

widespread deposition at elevations above the stage equivalent 

to a flow rate of 227 m3

/s and caused an increase in the area 

and volume of the high-elevation parts of sandbars, thereby 

increasing the size of campsite areas. In this study, we differentiate between four response styles, depending on how sediment 

was distributed throughout each study site. Then, we present 

the longitudinal pattern relevant to the different response styles 

and place the site responses in context with two previous highrelease experiments conducted in 1996 and 2004. We find that 

(1) nearly every measured sandbar aggraded above the 227-

m3/s water-surface elevation, resulting in sandbars as large or 

larger than occurred following previous high flows; (2) reaches 

closest to Glen Canyon Dam were characterized by a greater 

percentage of sites that incurred net erosion, although the 

total sand volume in all sediment-flux monitoring reaches was 

greater following the 2008 HFE than following previous high 

flows; and (3) longitudinal differences in topographic response 

By Joseph E. Hazel, Jr.1, Paul E. Grams2, John C. Schmidt 3 , and Matt Kaplinski1

1

Northern Arizona University, School of Earth ScienceV and 

Environmental Sustainability, Flagstaff, Arizona

 2U.S. Geological Survey, Southwest Biological Science Center, Grand 

Canyon Monitoring and Research Center, Flagstaff, Arizona

3

Utah State University, Department of Aquatic, Watershed, and Earth 

Resources, Logan, Utah

in eddies and in the channel suggest a greater and more evenly 

distributed sediment supply than existed during previous controlled floods from Glen Canyon Dam. 

Introduction 

Operations of Glen Canyon Dam affect the downstream 

geomorphology and associated riverine ecosystem along the 

Colorado River in Marble and Grand Canyons (fig. 1). One 

feature of the geomorphic environment is the sand and finer 

sediment that occurs as eddy bars, channel-margin deposits, 

and as patches that cover parts of the coarser grained channel 

bed. These deposits are of interest, because sandbars are an 

attribute of the pre-dam riverine landscape, are used as campsites, are substrate for riparian plants, create aquatic habitat, 

and are a source of windblown sand that potentially buries and 

preserves archaeological sites (Wright and others, 2005; Draut 

and Rubin, 2008). 

Completion of Glen Canyon Dam in 1963 eliminated the 

supply of fine sediment delivered from the upper Colorado 

River Basin, decreased the magnitude of annual flood flows, 

and increased the magnitude of base flows (Howard and 

Dolan, 1981; Topping and others, 2003; Wright and others, 

2005). Collectively, these changes in hydrology and sediment 

supply caused evacuation of sand from the bed and margins 

of the river channel, such that the average size of sandbars 

emergent at base flows in 2001 was at least 25 percent less 

than before completion of the dam (Schmidt and others, 2004). 

Other factors, such as vegetation growth (Turner and Karpiscak, 1980), hillslope runoff or burial by debris flows (Melis 

and others, 1994), eolian processes (Draut and Rubin, 2008), 

and human activities (Phillips and others, 1986) have also contributed to reductions in the area of exposed bare sand, thereby 

reducing the area available for camping (Kearsley and others, 

1994; Kaplinski and others, 2005).

The Colorado River in Marble and Grand Canyons is currently the subject of a large-scale river rehabilitation program 

called the Glen Canyon Dam Adaptive Management Program 

(GCDAMP). A primary goal of the GCDAMP is to maintain 

or improve the condition of sandbars for their associated 
Figure 1. The Colorado River and Grand Canyon National Park, between Lake Powell and Lake Mead reservoirs. Shown are the lo

of Lees Ferry, the topographic survey sites, U.S. Geological Survey gaging stations (with station numbers), and the sediment-transpmonitoring reaches between the sediment-transport measurement sites. 

▲

▲

▲

▲

▲

▲

Colorado River
Physical Setting 3

ecosystem and resource values (U.S. Department of Interior, 

1995; National Research Council, 1999). One aspect of the 

GCDAMP is implementation of an experimental program that 

evaluates the environmental effects of dam releases (Patten and others, 2001; Wright and others, 2005). On March 

6, 2008, a 2.5-day (60-hour) controlled flood of 1,203 cubic 

meters per second (m3/s) was released from Glen Canyon Dam 

(U.S. Department of Interior, 2008). At the time of this release, 

the river bed had been supplied with fine sediment (sand, silt, 

and clay) by a series of floods from the Paria River (fig. 1) in 

fall 2006 and fall 2007. The purpose of the present study is to 

document the response of eddy bars and some of the associated resource attributes to this flood, termed the 2008 highflow experiment (2008 HFE). The findings are compared to 

results from two previous high-flow experiments conducted 

under differing sand-supply and flow conditions: the longer 

duration 1996 HFE of 1,275 m3/s (Webb and others, 1999) and 

the 2004 HFE of similar magnitude and duration as the 2008 

HFE (Topping and others, 2006a). 

Purpose and Scope

The principal goals of this study are: (1) evaluation of 

whether sandbars located throughout the Colorado River in 

Marble and Grand Canyons gained or lost sand in response 

to the 2008 HFE, (2) evaluation of the persistence of rebuilt 

sandbars under normal dam operations over the 6-month 

period that followed the 2008 HFE, (3) comparison of the 

river response to the 2008 HFE with the river response to the 

1996 and 2004 high flows at common monitoring sites, and (4) 

evaluation of changes in the area of campsites associated with 

sandbar changes resulting from the 2008 HFE. Site response 

was analyzed above and below the 227-m3/s water-surface 

elevation (hereafter referred to as the reference stage; sand 

below this elevation is almost always subaqueous, while sand 

above this elevation is either always subaerial or within the 

diurnal fluctuating zone of dam releases associated with peaking hydropower generation). In order to facilitate comparison 

with data collected during the two previous HFEs, detailed 

field measurements were made at the long-term study sites 

measured by Hazel and others (1999) and Kaplinski and others 

(2005), as well as additional sites, on five survey trips in 2008. 

Physical Setting

Units, Place Names, and Study Area

Measurements are reported in the SI system; however, 

locations and place names are reported in river miles (RM), 

downstream from Lees Ferry, Arizona (RM 0). The rivermile convention has long been used as the standard reference 

system for locations along the Colorado River in Marble and 

Grand Canyons and was formalized in 2006 (U.S. Geological 

Survey, 2006). Lees Ferry is located 15.5 miles downstream 

from Glen Canyon Dam and 1 mile upstream from the mouth 

of the Paria River and the northeastern boundary of Grand 

Canyon National Park (fig. 1). 

In this report, we refer to Marble Canyon as the reach 

of the Colorado River between the Paria River and the Little 

Colorado River, located at RM 61.5 (fig. 1). The Paria River 

is the primary source of sand to the upstream end of Marble 

Canyon (Topping and others, 2000). Although Grand Canyon 

extends downstream to the Grand Wash Cliffs (RM 276), 

for our purposes we refer to Grand Canyon as the segment 

downstream from the Little Colorado River and extending to 

Diamond Creek (RM 226). Place names were derived from 

Stevens (1990) and Belknap (2001). The “left” and “right” 

sides of the Colorado River are with respect to assuming the 

viewer is facing in a downstream direction.

For evaluation of downstream variations in response to 

the 2008 HFE, we defined five sediment-transport-flux monitoring reaches in Marble and Grand Canyons (fig. 1; table 2). 

These reaches are demarcated by locations at which tributary 

sediment inputs occur or mainstem bed sediment, suspendedsediment concentration, and grain size are monitored (Topping 

and others, 2006b). The fixed sediment-transport measurement 

sites are: (1) the Colorado River at Lees Ferry gaging station 

(USGS station number 09380000; RM 0), (2) the RM 30 sediment station, located at the midpoint of Marble Canyon, (3) 

the Colorado River above Little Colorado River near Desert 

View gaging station (gage was discontinued) (09383100; 

RM 61), (4) the Colorado River near Grand Canyon gaging 

station (09402500; RM 88), (5) the former Colorado River 

above National Canyon near Supai gaging station (09404120; 

RM167), and (6) the Colorado River above Diamond Creek 

near Peach Springs gaging station (09404200; RM 225). In 

the downstream order in which they occur, we refer to the 

sediment-transport-flux monitoring reaches as upper Marble 

Canyon (UMC), lower Marble Canyon (LMC), eastern Grand 

Canyon (EGC), central Grand Canyon (CGC), and western 

Grand Canyon (WGC). 

The Fan-Eddy Complex

The geomorphic framework of the Colorado River in 

Marble and Grand Canyons is dominated by an assemblage 

of channel features termed the fan-eddy complex by Schmidt 

and Rubin (1995). Debris flows and floods in steep, ephemeral 

tributaries to the Colorado River deliver large boulders to the 

Colorado River, some of which cannot be transported by the 

mainstem (Webb and others, 1989). The bouldery deposits 

create debris fans that constrict the mainstem channel flow 

and create rapids (fig. 2A). These hydraulic controls define 

the longitudinal profile of the river and affect flow patterns 

immediately upstream and downstream from each debris 

fan (Howard and Dolan, 1981). Immediately upstream from 

each debris fan is an area of ponded flow, where flow has 

decelerated, stage has increased, and water-surface slope has 

decreased so as to create sufficient potential energy to accelerate flow through the constriction, analogous to flow from a 
4 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Total Eddy Channel

Eddy

Boundary

High-Elevation

Zone

Minimum Surface

C

Low-Elevation Zone

Midelevation Zone

Reference Stage

708 m3/s

227 m3/s

a a’

A B

a

a’

Figure 2. Geomorphic description of physical setting and boundary definitions for fan-eddy complexes of the Colorado River. 

A, Aerial view (May 2002) of a typical fan-eddy complex (listed in table 1 as site 47R) in Marble Canyon at the reference stage 

(227 m3

/s). DF, tributary debris fan; R, rapid or riffle; S, scour hole; ES, exit slope; E, eddy; RB, reattachment bar; SB, separation 

bar, RCC, return-current channel. Arrows indicate flow direction. Box insert indicates area shown in B. B, Digital elevation model 

(1983 Arizona State Plane in meters, central zone projection) of the same site from the April 1, 2008, survey. The dashed blue line 

is the computational boundary for the channel expansion, with a dividing line between the eddy and main channel. The solid 

black and white lines are the stage elevations reached by flows of 227 m3

/s and 708 m3/s, respectively. These stage elevations 

separate high-elevation, midelevation, and low-elevation zones within the total eddy. The thin dashed black lines show the 

surveyed campsite area. Heavy white line is approximate location of schematic cross section a—a’ shown in C. C, Schematic of 

computational boundaries in a—a’ described in the text. Note that a—a’ is viewed in an upstream direction. 

nozzle (Kieffer, 1985). The area of ponded flow may extend 

upstream a few channel widths to a few kilometers and varies 

with discharge. Immediately downstream from each debris 

fan, channel width typically is wider than elsewhere (Schmidt, 

1990). Cross-sectional area here is much greater than in the 

rapid, because channel depth also increases greatly. Much of 

the increase in depth occurs where a deep scour hole typically develops immediately downstream from the rapid (fig. 

2A). Lateral recirculating eddies typically form between the 

boundary of the downstream flowing jet and the channel banks 

(Schmidt, 1990). Further downstream from the scour hole and 

lateral recirculating eddies, the channel typically narrows and 

shallows; this portion of the bed is referred to as the exit slope 

(fig. 2A). The acceleration of stream flow associated with 

the slight decrease in channel cross-sectional area terminates 

the downstream length of eddies along the channel banks. A 

midchannel or bank-attached cobble bar commonly occurs in 

these areas of somewhat shallow flow. The coarse debris is the 

result of erosion of the upstream debris fan during pre-dam 

high flows (Webb and others, 1989). At lower discharges, flow 

typically passes around the margins of these cobble bars and 

creates a riffle (fig. 2A).

Each of the sites selected to study 2008 HFE sandbar 

response is in the channel expansion immediately downstream 
Controlled Floods, Tributary Sand Inputs, and Fluctuating Flows 5

from the rapid. All sites include the entire bed of the lateral 

recirculating eddy, and most sites include the bed of the 

adjacent channel, where the predominant direction of flow is 

downstream. Although debris fans may become overtopped at 

high discharges, causing regions of recirculating flow to shrink 

and eventually disappear, all sites included in this study were 

eddies with recirculating flow across the full range of discharges that occurred during the study period. 

Lower flow velocities in eddies promote deposition from 

the suspended load. Eddies have the potential to completely 

fill with sediment (Wiele and others, 1996) and can contain 

sandbars more than 10 m thick (Rubin and others, 1994). The 

scour hole and main-channel bed adjacent to eddies may be 

completely covered with sand, forming subaqueous dune fields 

1 to 2 m thick in some locations, while in other locations the 

bed-sand area is patchy over large regions of the gravel, boulder, 

and bedrock bed (Anima and others, 1998; Howard and Dolan, 

1981; Wilson, 1986; Schmidt and others, 2007; D. Topping, 

U.S. Geological Survey, written commun., 2009). Much thicker 

sand deposits, however, can temporarily accumulate in the main 

channel during tributary flooding (Wiele and others, 1996).

Sand deposits in eddies have been described and classified by Schmidt (1990) as separation bars, which form near the 

upstream part of the eddy where flow separates from the bank, 

and reattachment bars, which form where flow reattaches to 

the bank (fig. 2A). Separation bars mantle the downstream 

surface of debris fans, but they do not exist downstream from 

all debris fans. Reattachment bars form a platform projecting 

upstream into the center of the eddy. A distinct geomorphic 

characteristic of reattachment bars is the return-current channel, where upstream-directed flow is redirected along the bank 

(Rubin and others, 1990). This deep channel typically divides 

the separation bar from the reattachment bar. At lower flows, 

the return-current channel becomes stagnant as recirculating 

flow is partially blocked by an emergent reattachment bar. 

This low-velocity condition can result in suitable habitat for 

certain native fish (Korman and others, 2004; Schmidt and 

others, 2007). We use the term “eddy bar” where the unique 

topography of separation bars and reattachment bars cannot 

be distinguished or where the distinction is not relevant to the 

discussion (table 1). 

Controlled Floods, Tributary Sand 

Inputs, and Fluctuating Flows

The 2008 HFE was the third controlled flood released 

from Glen Canyon Dam with the intention of rebuilding 

sandbars. The first such experimental flow occurred in 1996 

and consisted of a 7-day release of 1,275 m3/s (see Webb and 

others, 1999, for details on the 1996 HFE). Sandbar surveys 

and photographic analyses indicated that sediment was deposited on the channel margin as high-elevation sandbars but 

that low-elevation sandbars were eroded (Hazel and others, 

1999; Andrews and others, 1999; Schmidt and others, 1999). 

Sandbar deposits formed by the 1996 HFE exhibited upwardcoarsening grain size, indicating that the supply of fine sediment was exhausted during the course of the event (Rubin 

and others, 1998). This finding was supported by sediment 

budgets constructed for the 1996 high flow that showed eddies 

were the source for much of the suspended sediment, rather 

than the sandy bed of the main channel (Schmidt and others, 

1999; Hazel and others, 2006a). On the basis of the 1996 findings, researchers concluded that future high-flow experiments 

should only be conducted under conditions of enriched sand 

supply such that high flows would result in sandbar deposition, without depleting sand from storage as occurred in 1996 

(Rubin and others, 2002). 

This concept of sand-enriched high flows was first 

tested by the second high flow, conducted in November 2004, 

which was timed to follow a period of sand delivery from 

the Paria River. Because findings from the 1996 HFE indicated that most deposition occurred in the initial 1 to 2 days 

of that experiment (Andrews and others, 1999; Schmidt and 

others, 1999), and on the basis of later sandbar simulations 

conducted by Wiele and Torrizo (2005) with flow and sandsupply boundary conditions similar to those measured during 

the 1996 HFE, the 2004 HFE was shorter in duration (2.5 

days) and had a slightly smaller peak discharge (1,160 m3

/s). 

This experiment resulted in an increase of total sandbar area 

and volume in the upper end of Grand Canyon, but further 

downstream, where sand accumulation had not occurred, 

there was a net transfer of sand out of eddies (Topping and 

others, 2006a). Topping and others (2006a) concluded that in 

order to achieve increases in total sandbar area and volume 

throughout a greater proportion of Marble and Grand Canyons, more sand would be required than was available during 

the 2004 high flow. 

The 2008 HFE was released specifically to test the 

hypothesis that greater antecedent sand supply could result 

in sandbar building throughout most of Marble and Grand 

Canyons without depleting more sand than was accumulated 

by tributary inputs leading up to the event (Topping and others, 2006a). Tributary floods in the Paria River, primarly in 

October 2006 and August–September 2007, supplied about 

3.35±0.34 million metric tons of sand to the Colorado River 

between the 2004 and 2008 HFEs (D. Topping, U.S. Geological Survey, written commun., 2009). As a result, Marble 

Canyon contained approximately two to three times more sand 

than had accumulated before the 2004 high-flow release. In 

contrast, the year antecedent to the 1996 HFE had the least 

recorded accumulation of tributary-supplied sand in the Colorado River in Marble and Grand Canyons (D. Topping, U.S. 

Geological Survey, written commun., 2009). 

The 2008 HFE had a similar hydrograph as the 2004 

high-flow hydrograph (fig. 3). Beginning on March 4, 2008, 

releases were increased by 43 m3

/s per hour until hydropower 

plant capacity (892 m3/s) was reached, and then each of the 

four Glen Canyon Dam bypass tubes was opened for a total 

bypass release of 425 m3/s by March 6 (U.S. Department 

of the Interior, 2008). For the 60-hour period that discharge 
6 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

[Site names are from Belknap (2001) and Stevens (1990) or are informally used. **, sites surveyed before 

and after the 1996 and 2004 HFEs. *, sites surveyed before and after the 1996 HFE. -, not determined 

because bathymetry data were not collected at the site.]

Site 

ID1

River 

Mile 

(RM)2

Site Name Deposit 

Type3

Eddy

Size

(m2

)

4

Expansion Ratio5

Stage

Change6

(m) 242

(m3

/s)

1,203 

(m3/s)

1R 1.2 Paria Beach U 40,880 2.0 1.5 3.0

3L** 2.5 Cathedral Wash R 7,610 1.5 1.3 3.4

8L** 8.1 Below Jackass S - 1.6 1.5 3.0

9L 8.9 S,R 12,270 1.8 1.4 4.2

16L** 16.6 Hot Na Na Wash S 8,160 2.1 1.2 3.1

22R** 22.0 Twentytwo Mile R 7,160 1.5 1.5 5.8

24L 23.6 Lone Cedar U - 1.3 1.4 5.0

29L 29.5 Shinumuo Wash U - 1.2 1.0 4.8

30R** 30.7 Sand Pile R 8,520 1.7 1.6 5.0

32R** 31.9 South Canyon U 11,620 2.8 1.5 2.9

33L 33.3 Redwall Cavern R - - - 4.7

35L 35.1 Nautiloid S,R 21,390 2.5 1.4 5.0

41R 41.4 Buck Farm S,R 42,050 2.9 1.7 4.1

43L** 43.4 Anasazi Bridge R 8,460 1.7 1.3 4.3

44L** 44.6 Eminence S,R 26,570 1.9 1.4 4.1

45L 45.0 Willie Taylor 

Camp S,R 22,550 1.9 1.4 4.0

47R** 47.6 Lower Saddle R 28,440 2.6 1.9 3.5

49R 48.8 R 7,640 1.4 1.3 3.8

49L 48.9 S,R 14,470 1.4 1.2 3.8

50R** 50.2 Dinosaur S,R 8,691 1.0 1.0 3.9

51L** 51.0 Fiftyone Mile 

Camp R 31,690 1.6 1.5 3.5

54R 54.6 R 12,370 1.4 1.4 3.4

55R** 55.9 Kwagunt Marsh R 24,300 1.1 1.4 2.5

56R 56.6 KwaguntBeach U - 1.1 0.8 3.1

Table 1. Channel geometry and geomorphic characteristics for selected study sites, 

Colorado River in Marble and Grand Canyons. 
Controlled Floods, Tributary Sand Inputs, and Fluctuating Flows 7

Site 

ID1

River 

Mile 

(RM)2

Site Name Deposit 

Type3

Eddy

Size

(m2

)

4

Expansion Ratio5

Stage

Change6

(m) 242

(m3

/s)

1,203 

(m3/s)

[Site names are from Belknap (2001) and Stevens (1990) or are informally used. **, sites surveyed 

before and after the 1996 and 2004 HFEs. *, sites surveyed before and after the 1996 HFE. -, not 

determined because bathymetry data were not collected at the site.]

58L 58.1 Malgosa R - 0.9 0.8 3.6

62R** 62.9 Crash Canyon R 15,920 1.7 1.4 3.9

63L** 63.5 S,R 27,870 3.0 2.1 4.0

65R** 65.2 Carbon S,R 17,130 1.6 1.2 2.8

65L 65.8 R 12,300 1.6 1.4 2.5

66L 66.1 Palisades Creek S,R - 1.8 1.4 2.0

68R** 68.8 Tanner U 15,950 1.2 1.1 2.4

70R 70.1 Basalt R - 2.0 1.7 2.7

81L** 81.8 Grapevine U 3,410 1.5 1.6 3.7

84R 84.6 Clear Creek S,R - 1.3 1.3 4.9

87L** 87.6 Cremation U 1,150 1.5 1.1 3.8

88R 88.1 Boat Beach R 3,070 1.2 1.3 3.4

91R* 91.8 91 Mile S 4,490 1.3 1.2 4.2

93L* 93.8 Granite U 3,590 1.7 1.8 2.9

104R* 104.4 Upper 104 Mile R 1,020 1.3 1.0 3.9

119R* 119.4 Big Dune R 8,930 1.6 1.3 4.6

120R 119.8 119 Mile Camp R 10,080 1.9 1.3 4.5

122R* 122.7 122 Mile Camp R 8,240 2.2 2.1 4.2

123L* 123.3 Upper Forster R 8,050 1.4 1.3 4.0

137L* 137.7 Football Field R 5,140 1.2 1.2 4.3

139R* 139.6 Fishtail U 7,190 1.3 1.2 4.5

145L* 145.8 Above Olo R 1,320 1.4 1.5 5.0

165R 165.7 165 Mile S,R 5,150 1.1 0.9 4.6

166L 167.2 Lower National S - 2.4 1.1 3.6

Table 1. Channel geometry and geomorphic characteristics for selected study sites, 

Colorado River in Marble and Grand Canyons.—Continued 
8 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

exceeded 1,175 m3/s at the USGS streamflow-gaging station 

at Lees Ferry (09380000; fig. 1), beginning at 0600 hours 

(Pacific Standard Time) on March 6 and ending at 1830 hours 

on March 8, the mean discharge was 1,203 m3/s. The downramp rate was 43 m3

/s per hour until the normal hydropower 

plant releases scheduled for March were reached. In the first 

month following the 2008 HFE, diurnal peak flows were 

between 325 and 390 m3/s, with daily fluctuations of 142–227 

m3/s. On April 15, 2008, releases were increased to diurnal 

peak flows of 425–462 m3/s. In summer, monthly discharges 

were higher, with diurnal peaks flows of 500–530 m3/s and 

daily fluctuations of 200–227 m3/s. In September and October 

2008, there was a steady release regime of 354 m3/s. These 

major changes in flow regime allow comparison of sandbar 

stability under relatively lower fluctuating flows associated 

with normal spring operations (typically referred to as the 

modified low fluctuating flow dam operation) followed by the 

response after higher summer operations. 

Methods

Repeated high-resolution topographic surveys were made 

on five river trips in 2008 (fig. 3). Each measurement site is 

located in the downstream part of a fan-eddy complex (fig. 

2A). Sixty-two emergent sandbars, consisting of reattachment 

and/or separation bars, were surveyed down to the 227-m3

/s 

stage at 57 sites (appendix A). Three study sites were not 

surveyed on the February 2008 river trip (50R, 56R, and 62R), 

and we utilized data collected in October 2007 as the pre2008 HFE site condition at these sites. Subaerial topography 

172L* 172.6 Below Mohawk R 9,400 1.3 1.3 3.9

183L* 183.3 Below Chevron R 5,150 1.7 1.6 4.1

194R* 194.6 Hualapai Acres R 14,140 2.2 2.1 3.8

201R 201.6 R 12,060 2.5 1.4 3.4

202R* 202.3 202 Mile S,R 15,620 2.7 1.7 3.8

213L* 213.3 Pumpkin 

Springs U 3,990 3.1 2.4 5.8

214R 214.5 214 Mile R 5,250 1.4 1.1 3.8

220R* 220.1 Middle 220 U 2,450 1.4 1.1 3.0

225R* 225.5 R 5,635 2.3 1.8 2.9

1

The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of 

the river, respectively, facing downstream.

2

Approximate location based on the river mile centerline (U.S. Geological Survey, 2006) downstream 

from Lees Ferry (river mile 0), in Grand Canyon National Park.

3

Deposit type: R, reattachment bar, S, separation bar, U, undifferentiated eddy bar.

4

Eddy size determined by a fixed boundary between the main channel and eddy located at the base of 

the eddy sandbar.

5

Average channel width in expansion with associated eddy divided by average channel width in nearest upstream or downstream constriction. Channel width determined using the method for generating 

cross-sections by Magirl and others (2008).

6

Difference in water-surface elevation between the 227-m3/s and 1,203-m3/s stage (Hazel and others, 

2006b).

Site 

ID1

River 

Mile 

(RM)2

Site Name Deposit 

Type3

Eddy

Size

(m2

)

4

Expansion Ratio5

Stage

Change6

(m) 242

(m3

/s)

1,203 

(m3/s)

[Site names are from Belknap (2001) and Stevens (1990) or are informally used. **, sites surveyed 

before and after the 1996 and 2004 HFEs. *, sites surveyed before and after the 1996 HFE. -, not 

determined because bathymetry data were not collected at the site.]

Table 1. Channel geometry and geomorphic characteristics for selected study sites, 

Colorado River in Marble and Grand Canyons.—Continued 
Methods 9

0

400

800

1,200

1,600

2008 HFE

J F M A M JJ OSA N D

MONTHS, 2008 CALENDAR YEAR

DISCHARGE, IN CUBIC METERS PER SECOND

Figure 3. Instantaneous discharge of the Colorado River at USGS streamflow-gaging station (09380000), Lees 

Ferry, Arizona, for the 2008 calendar year. The solid, horizontal lines indicate the times of survey river trips.

and campsite areas were surveyed with Topcon GTS-313 and 

Topcon GPT-2003 electronic total stations. 

Bathymetry was measured and analyzed at 40 sites on 

the February and April trips with a multibeam sonar system 

installed on a 7-m motorized raft (appendix A). These measurements expanded the survey area to include the bed of the 

eddy and adjacent main channel, such that the entire area of 

sand and water ever inundated since 1990 was included in the 

survey. Typically, the longitudinal extent of each bathymetric 

survey was from the downstream end of the rapid or riffle to 

approximately one to two channel widths downstream of the 

eddy that existed at the time of the survey.

The combined topographic and bathymetric data have a 

positional accuracy better than 0.10 m and elevation accuracy 

that varies from 0.05 m or less for points acquired by total station to 0.10 m or less for bathymetric points. Point data were 

referenced to the Arizona State Plane NAD83, Arizona Central 

(FIPS 202) coordinate system, in meters, using established 

benchmarks. Specific details and error analysis of the topographic surveying techniques and the multibeam system are 

described by Hazel and others (2008) and Kaplinski and others 

(2009), respectively. 

The topographic and bathymetric point data for each 

study site were combined, and digital elevation models 

(DEMs) at 1-m resolution were constructed by building 

triangulated irregular networks (TINs) using Delaunay triangulation (McCullagh, 1988). Changes in topography were 

determined by subtracting the pre-2008 HFE DEM from the 

post-2008 HFE DEM to generate erosion-deposition maps. 

Kaplinski and others (2009) reported an average uncertainty 

of 5 percent in topographic surfaces generated using the same 

methods used in this study. 

The topographic surfaces were used to compute sand 

deposit volume within the two geomorphic settings that occur 

in the channel expansion: the eddy and the bed of the adjacent 

channel (fig. 2B). Because the size and exact position of the 

eddy change as a function of discharge, a fixed eddy boundary 

was delineated. This boundary divides the eddy from the main 

channel at the base of the eddy sand deposit (fig. 2B). Thus, 

the eddy for computational purposes includes all deposits 

separated from the main channel within the region between the 

separation and reattachment points of the eddy. Hereafter, we 

use “total eddy” to refer to this computational area. Sandbar 

deposits above the reference stage outside the eddy were not 

surveyed; thus the main-channel environment consists entirely 

of sand deposits below the 227-m3

/s water-surface elevation. 

To examine the entire site or channel-expansion response, we 

refer to the combined total eddy and main channel volumes 

as “total site sand volume.” However, it is not possible to 

report absolute sand volumes, because depths to the gravel, 

boulder, or bedrock substrate are known only for a very few 

locations (Rubin and others, 1994). Thus, the sand volumes 

reported in this study are computed by determining the volume 

of sand above a synthetically constructed minimum surface 
10 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

(fig 2C). The minimum surface was computed by determining 

the lowest sandbar elevation ever measured for each 1-m grid 

cell using all surveys for each study site, including all measurements made from 1990 to 2008. The minimum sandbar 

surface thus separates sediment that has never changed for 

the period of monitoring (below the minimum surface) from 

sediment that has been active during the period of monitoring. 

The minimum surfaces used in this report are an update of 

the minimum surfaces computed and described by Hazel and 

others (2006a). We also computed maximum sandbar surfaces 

with the same method in order to determine the percentage of 

the total eddy area filled at any given time by an eddy sandbar. 

Thus, we defined a reference eddy sand-storage volume for 

each site as the maximum volume of sand that can possibly be 

stored within the eddy below the maximum surface. 

To examine sandbar response within the total eddy computational area, we differentiate between three elevation zones 

(figs. 2B and C). The low-elevation zone is defined as the volume of sand between the calculated minimum surface and the 

elevation of the reference stage of 227 m3

/s. The midelevation 

zone is the region between the reference stage and the water 

surface elevation at a higher topographic level defined as the 

elevation reached by a discharge of 708 m3/s. The high-elevation zone includes the region above the 708-m3

/s water-surface 

elevation. We refer to the combined mid- and high-elevation 

zones as sand storage above the reference stage. These elevation zones were selected because 227 m3

/s represents the lowest discharge typical of normal hydropower plant operations 

and 708 m3/s represents the highest discharge of normal daily 

hydropower plant operations. The stage elevations for flows of 

227 and 708 m3/s were derived from the stage-discharge relations of Hazel and others (2006b). At some sites that had not 

been surveyed previously, new relations were computed using 

similar methods. 

The thickness of sandbars resulting from the 2008 HFE 

was determined from the change in sand volume over a 

defined area for each site within four bins that increase in spatial scale: high-elevation sand (within the eddy), sand above 

reference stage (within the eddy), total sand within the eddy, 

and total sand within the study site. To determine total sand 

thickness in eddies and total sand thickness within entire study 

sites, the total volume change at all zonal elevations within an 

eddy and the combined eddy and channel were divided by the 

measured area of the respective zones. Because the portion 

of the sandbar exposed above the reference stage occupies a 

small percentage of the overall eddy area, high-elevation sand 

thickness and the thickness of the sand above the reference 

stage were determined by dividing the volumetric change by 

the area of the maximum sandbar surface (that is, an estimate 

for the maximum potential sandbar area was computed with 

the same method as the minimum surface). 

Post-2008 HFE bar stability was evaluated by comparing 

sandbar thickness above the reference stage at a 36-site subset of 

the study sites collected in May 2008 to surveys at the same sites 

collected in September and October 2008 (appendix A). In order 

to calculate erosion rates, we divided volume change above the 

reference stage by the number of days between successive surveys 

at each site. To observe short-term changes at the sites and also 

to help interpret longer term changes, a combination of remote 

analog and digital cameras were utilized to collect repeated daily 

oblique images at 32 of the sites (appendix A).

To evaluate sandbar response in comparison with 

suspended-sand concentration, the study sites were grouped 

into reaches of similar sand concentration during the 2008 

HFE (table 2), based on proximity to the fixed sedimentmonitoring stations and also to measurements of suspendedsand concentration collected longitudinally during the 2008 

HFE (D. Topping, U.S. Geological Survey, written commun., 2009). A subset of the study sites were analyzed for 

comparison of the 2008 HFE results with results from the 

two previous HFEs in 1996 and 2004. For comparing total 

sand volume, there were 29 sites where sufficient data were 

collected in 1996 and 2008 to make comparisons (table 1). 

Of these sites, 10 sites in UMC, LMC, and EGC were also 

surveyed in 2004 (table 1). For comparisons of sand volume 

above reference stage, there were 38 sites that could be compared between 1996 and 2008 and 22 sites in UMC, LMC, 

and EGC that could be compared between 2004 and 2008. To 

compare sand volumes following the 2008 HFE, the measured values were normalized as the ratio of sand volume 

measured following each of the HFEs to the sand volume 

measured immediately before the 1996 HFE. This method of 

normalizing the data is consistent with the method used when 

analyzing such data for the 1996 HFE (Hazel and others, 

1999) and the 2004 HFE (Topping and others, 2006a). These 

normalized data were used to compute cumulative probability distributions and median response for each of the reaches 

of similar suspended-sediment concentration corresponding 

to the sediment-flux monitoring reaches (fig. 1).

Campsite area as measured in this study is the area of 

the sandbar that can be used as a kitchen or a place to sleep. 

We adopted the criteria of Kearsley and Warren (1993) in 

defining campsite area as that part of the sandbar with no 

more than an 8 degree slope and little or no vegetation. Slope 

angle was estimated by observation in the field. Points were 

surveyed that outline the perimeter of each camping area, 

as well as points surrounding features to exclude from the 

camping area, such as trees, bushes, and rocks (Kaplinski 

and others, 2005). The perimeter points were then used to 

define polygons of campsite area. Plan areas of the campsite 

area TIN models were summarized for high-elevation and 

midelevation zones. 

The campsite measurements were analyzed by their 

occurrence in “critical” and “noncritical” camping reaches. 

A critical reach was defined by Kearsley and Warrren (1993) 

as any contiguous stretch of the river in which the number 

of available campsites is limited because of geologic characteristics, high demand, or other logistical factors. Noncritical reaches were defined as any stretch of the river in which 

campsites are plentiful and little competition occurs for the 

majority of sites. There are presently more than 220 actively 

used river campsites in the Grand Canyon National Park 
Results 11

inventory of camps between Lees Ferry and Diamond Creek 

(http://www.nps.gov/grca/parkmgmt/riv_camp-atlas.htm). 

The number of campsites per river mile in noncritical reaches 

is about twice that in critical reaches (table 3). Sixteen of the 

sandbar monitoring sites chosen for campsite monitoring in 

this study are located within critical reaches, and 21 occur in 

noncritical reaches.

Results

Overview of Topographic Response 

Deposition in the high-elevation zone occurred at nearly 

every study site. The volume of sand in this zone increased by 

more than 5 percent at 48 of the 57 sites surveyed (appendix B, 

table B1). The median change in high-elevation deposit thickness was 0.21 m, and virtually all sites aggraded to some extent 

(fig. 4A). Nearly every measured eddy bar aggraded above 

the reference stage; however, the changes were more variable 

in the midelevation zone than observed in the high-elevation 

zone (appendix B, table B2). As a result, the median change in 

sand thickness above the reference stage was 0.26 m, but the 

changes from site to site were more variable (fig. 4B).

Because of substantial variability in the low-elevation eddy 

zone and on the bed of the main channel (appendix B, table 

B3), the total eddy sand thickness change ranged from -1.88 to 

1.13 m (fig. 4C). Fifty percent of the sites had a total eddy sand 

thickness change of 0.10 m or greater. In many cases, net deposition above the reference stage in eddies was approximately 

balanced by net erosion below the reference stage. Sandbar 

thickness change was also computed for each site, including 

above and below reference stage for all parts of the channel and 

eddies. Total site changes were highly variable, ranging from 

-2.27 to 0.80 m, with a median of 0.06 m (fig. 4D). 

Styles of Topographic Response 

The widespread deposition at all high-elevation sites 

and at most sites in the midelevation zone, and the variability 

in the low-elevation eddy zone and on the bed of the main 

channel, resulted in increases or decreases in total-site sand 

volume. Therefore, we examined the exchange between highand low-elevation areas of each study site by comparing the 

transfer of sand above and below the reference-stage elevation.

These responses were categorized into four styles of topographic change depending on the combination of (A) net 

change in sandbar volume within the eddy boundary above 

reference stage and (B) net change in volume for the entire 

site, including the channel and eddy below reference stage 

(fig. 5). The Style 1 response consisted of net increase in 

Table 2. Sediment-transport flux-monitoring stations and reaches of the Colorado River 

used to compare the 1996, 2004, and 2008 HFEs. 

[RM, approximate location based on the river mile centerline (U.S. Geological Survey, 2006) downstream 

from Lees Ferry (river mile 0) in Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing downstream.]

Reach

Sedinenttransport flux 

monitoring 

reach (RM)

Corresponding 

reach of similar 

suspended- sediment concentration

(RM)

Upstream and downstream study site 

used for comparison among high flows

Total site sand 

volume

Sand volume above 

reference stage

Upper 

Marble 

Canyon

0–30 15–40 22R–32R 16L–32R

Lower 

Marble 

Canyon 

30–61 40–65 43L–65R 43L–65R

Eastern 

Grand 

Canyon

61–87 65–130 68R–123L 68R–123L

Central 

Grand 

Canyon

87–166 130–180 137L–172L 137L–172L

Western 

Grand 

Canyon 

166–225 180–225 194L–225R 183L–225R
12 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

volume (deposition) at all elevations above and below reference stage, and this style characterized 45 percent of the 

study sites. The Style 2 response consisted of net decrease 

in volume (erosion) in the eddy and channel below reference 

stage and net deposition in the eddy above base flow stage. 

This was the second most common response and occurred at 

37 percent of the sites. The Style 3 response occurred where 

there was net erosion at all elevations above and below reference stage; this style characterized 16 percent of the measurement sites. The Style 4 response consisted of net erosion 

above reference stage and net deposition below reference 

stage. In the following section, we present examples of these 

response styles to illustrate some of their characteristics and 

show how erosion and deposition were distributed across 

individual sites. Because response Style 2 included some sites 

where there was net erosion across the channel and eddy and 

some sites where there was net deposition, an example of 

each case is included. Style 4 response was weak (nearly, a 

Style 1 response) and occurred at only 1 site; therefore, that 

response style is not discussed in detail. 

Style 1

The most common 2008 HFE response (Style 1) was 

one in which sand deposition increased the sand volume both 

above and below reference stage. In all of these sites there 

was net deposition in the eddy and in the entire study site. An 

example is 172L, where the post-2008 HFE volume at low elevation exceeded the pre-2008 HFE volume by 11 percent and 

the post-2008 HFE volume above reference stage exceeded 

the pre-2008 HFE volume by 29 percent (based on values 

reported in appendix B). The changes at this site are broadly 

representative of this style of response, although the magnitudes of proportional changes were greater at some sites (fig. 

5). In February 2008, a reattachment bar was present and the 

bar surface was covered by tamarisk (Tamarix ramosissima) 

near the talus slope and by arroweed (Pluchea sericea) along 

the shoreline (fig. 7A). In the high-elevation zone, the bar was 

eroding along a steep cutbank at the downstream end. The 

return-current channel was well defined at high elevation but 

nonexistent at flows in the low range of typical diurnal dam 

operating releases. Dunes present on the bed in the channel 

indicate that the bed was either sand or fine gravel. At the time 

of the February 2008 survey, the bar volume was 66 percent of 

the reference eddy-storage volume at the site. 

Deposition by the flood was greatest on the sandbar 

platform (fig. 6B). Much of the vegetation that had colonized 

the bar surface was buried beneath 1 to 2 m of sand (fig. 7C). 

Further upstream, there was deposition at low elevation, 

increasing the elevation of the bar platform. A distinct returncurrent channel separated the new deposit from the bank, as 

shown by the location of the 227-m3/s stage elevation in figure 

6B. The post-2008 HFE sandbar increased to 85 percent of the 

total eddy-storage volume above reference stage. 

The areal and volumetric change distributions calculated 

from the erosion-deposition map at 172L are shown in figure 

8. These changes are represented as histograms that show 

the area of the bed and volume of sand associated with each 

increment of bed elevation change. A unimodal distribution 

of change, in which 5,800 m2

 of the total eddy was increased 

0.25 to 1.0 m in elevation (62 percent of the eddy computational area), was also observed, as shown in figure 8A. A large 

part of the channel, about 5,600 m2, increased by 0.25 to 0.5 

m in elevation (64 percent of the channel computational area). 

Because the change in sand volume is the product of elevation change and the area over which that change occurred, the 

greatest volume of deposition occurred where the elevation 

increased between 0.75 and 1.0 m, and the greatest deposition 

in the channel occurred where the elevation increased 0.25 to 

0.5 m. There was a total of 3,657 m3

 of net deposition in the 

eddy and 1,595 m3 of net deposition in the channel. The site as 

a whole gained 5,252 m3 of sand (all reported values are listed 

in the tables contained in appendix B). 

Style 2 With Net Eddy Erosion

There were many sites where sand deposited above the 

reference stage but erosion occurred below that elevation. At 

some of these sites, both the eddy and channel environments 

were dominated by erosion, while at others there was net 

deposition in the eddy with a larger magnitude of net erosion 

in the adjacent channel. The changes at Eminence Break (44L) 

illustrate the Style 2 response for sites where there was net 

Table 3. Critical and noncritical recreational campsite reaches 

of the Colorado River (modified from Kearsley and Warren, 1993.

Reach

number

Reach name

Number of 

campsites 

per mile1

River mile

Starting Ending

1 Noncritical 0.5 0 11

2 Critical 1.1 11 41

3 Noncritical 1.5 41 77

4 Critical 0.9 77 116

5 Noncritical 1.7 116 139

6 Critical 0.7 139 164

7 Noncritical 1.1 164 226

1

Primary campsites originally inventoried by Kearsley and Warren (1993) and still 

considered active by Grand Canyon National Park (http://www.nps.gov/grca/parkmgmt/riv_camp-atlas.htm).
Results 13

A High-elevation zone

C Total eddy

0

5

10

15

20

-2.0 -1.0 0.0 1.0 2.0

0

5

10

15

20

-2.0 -1.0 0.0 1.0 2.0

0

5

10

15

20

-2.0 -1.0 0.0 1.0 2.0

0

5

10

15

20

-2.0 -1.0 0.0 1.0 2.0

B Above reference stage

D Total site (eddy and channel)

n = 62

Median = 0.21 m n = 62

Median = 0.26 m

n = 40

Median = 0.10 m

n = 39

Median = 0.06 m

NET THICKNESS CHANGE, IN METERS NET THICKNESS CHANGE, IN METERS

NET THICKNESS CHANGE, IN METERS NET THICKNESS CHANGE, IN METERS

NUMBER OF SITESNUMBER OF SITES

NUMBER OF SITESNUMBER OF SITES

erosion within the eddy even though deposition occurred in 

mid- and high-elevation zones (fig. 9). 

A large separation bar mantled the Eminence Break 

debris fan. In February 2008, the separation bar had two 

distinct topographic levels: the sand below the stage of 708 

m3/s gradually sloped toward the river; higher parts of the 

separation bar were partially vegetated, with scattered dunes 

(fig. 10A). The reattachment bar at the midelevation zone had 

a large platform, and there was a well-defined return channel shoreward from the sandbar (fig. 9A). The high-elevation 

zone of the reattachment bar was thickly vegetated and sloped 

steeply down to the midelevation surface. In the main channel, 

there was a scour hole adjacent to the eddy. At the time of the 

February 2008 survey, the volume of the eddy bars increased 

by 62 percent of the reference eddy-storage volume. 

Flood deposition was greatest on the downstream part 

of the reattachment bar, and erosion occurred in the upstream 

part of the eddy (fig. 9B). Deposition occurred on both bars 

at mid and high elevations. The return-current channel was 

widened and deepened through scour (note the new location 

of the 227-m3/s stage elevation in figure 9B). Deposition on 

the eddy bar above reference stage increased sand volume to 

80 percent of the reference eddy-storage volume. However, 

the 2008 HFE eroded more sand than was deposited at the 

site, because as much as 6 m of sand eroded from the lowelevation eddy zone by scour of the upstream reattachment 

bar (fig. 9C). In the main channel, there was erosion of sand 

adjacent to the scoured area of the eddy and sand deposition 

on the pool exit slope associated with growth of a dune field 

(fig 10B) 

The distribution of elevation change in figure 11A shows 

a bimodal distribution, with widespread, relatively lowmagnitude deposition (0.25-1.0 m) over an area of ~11,000 

m2 (42 percent of the total eddy area). The erosion of the 

upstream reattachment bar resulted in a smaller area (~7,500 

m2) with a depth of scour ranging from 1 to 5 m. In contrast, 

growth of the dune field on a large region of the channel bed 

(~11,500 m2) increased the sand elevation by 0.25 to 1.5 m 

Figure 4. Histograms of net sandbar thickness change between February and April 2008. A, High-elevation zone. B, 

Above reference stage. C, Total eddy. D, Total site (combined eddy and channel).
14 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

0 0.5 1 1.5 2

0

1

2

3

4

Style 1

Style 4

Style 2

Style 3

03L

65R

44L

172L

Net Eddy Deposition

Net Eddy Erosion

BELOW REFERENCE STAGE RATIO

OF POST- TO PRE-HFE SAND VOLUME

ABOVE REFERENCE STAGE RATIO

OF POST- TO PRE-HFE SAND VOLUME

Figure 5. Relation of proportional sand-volume 

change above reference stage (combined 

high-elevation and midelevation eddy zones) to 

below reference stage (combined low-elevation 

eddy and channel zones) for each site between 

February and April 2008. The four response 

styles (Styles 1, 2, 3, and 4) and specific example 

sites described in the text are shown. Also 

indicated is net total-eddy deposition or fill as 

indicated by the net thickness changes shown 

in figure 4C.

(66 percent of the channel area; fig. 11B). Because erosion 

of more than 6 m from the eddy was greater than the volume 

of sand deposited in the channel, the balance was toward net 

erosion at the site. There was a total of 13,132 m3 of net sand 

erosion in the eddy and 4,115 m3 of net deposition in the channel, resulting in total site erosion of 9,017 m3

. 

Style 2 With Net Eddy Deposition

A different variant of Style 2 is one in which there was 

net deposition in eddies (fig. 5). The changes at site 65R are 

typical of this style, where high-elevation eddy deposition 

exceeded low-elevation erosion (fig. 12). At 65R, lowelevation erosion reduced the volume of sand by 24 percent 

(based on values reported in appendix B) and deposition 

above the reference stage increased the volume of sand by 

about 300 percent. In February 2008, the separation bar was 

characterized by a zone of interspersed sand and boulders on 

the downstream end of the debris fan. A popular camp was 

located on a flat and level area on the downstream end of the 

separation bar. Only the highest part of the reattachment bar 

at the downstream end of the eddy was exposed at typical 

dam operating releases. A cutbank 2 to 3 m high separated 

the high-elevation sand deposit from the midelevation bar. 

A large reattachment bar occupied most of the low-elevation 

zone in the eddy (fig. 12A). 

Deposition was greatest in the downstream part of the 

eddy, where as much as 3 m of elevation increase occurred 

on the bar crest and platform, along and in front of the steep 

cutbank (fig. 12C). At this formerly low-elevation part of the 

eddy, the return-current channel was partially filled with sand 

as the reattachment bar aggraded toward the bank. Further 

upstream, a deeper return channel was excavated where more 

than 2 m of sand eroded from the upstream part of the reattachment bar. The deposition increased the eddy reference 

storage volume to 68 percent of maximum, and an extensive, 

uniform reattachment bar platform occupied a large region of 

the eddy above reference stage (fig. 13A). 

Widespread, relatively high-magnitude deposition (1.0-

3.25 m) occurred over approximately 6,000 m2

 of the total eddy 

area (fig. 14A). Erosion also occurred over a similar-sized area 

of the eddy, but the erosion was to a depth of 0.25-2.0 m (on 

average, less than the deposition), resulting in net eddy deposition. In the channel, moderate erosion (0.75-1.25 m) occurred 

over 7,500 m2 (83 percent of the channel area) of the bed (fig. 

14B). As at most other sites, erosion in the low-elevation zone 

of the eddy was accompanied by net erosion in the channel. 

There was a total of 5,294 m3 of net deposition in the eddy and 

5,975 m3 of net erosion in the channel, so the total site response 

was a net loss in sand volume of 681 m3. Nonetheless, both 

separation and reattachment bars substantially aggraded. 

Style 3

Changes at site 3L illustrate the Style 3 response (fig. 

15), wherein there was net erosion of both the eddy and main 

channel. At the time of the first survey in 

February 2008, the bar occupied 47 percent 

of the eddy. The highest part of the bar was 

at the downstream end of the eddy, and a 

well-defined return-current channel existed 

between a large reattachment-bar platform 

and the channel bank (figs. 15A, 16A). The 

channel bed shallowed downstream from the 

scour hole, and dunes covered much of the 

channel bed downstream from the eddy. 

Nearly the entire reattachment bar was 

inundated by the 2008 HFE (fig. 16B), and 

the topography of the bar and channel was 

significantly modified (fig. 15B). The only 

area of deposition was at the downstream 
Results 15

117855 118055

580702

580977

117855 118055

580702

580977

117855 118055

580693

580968

A Pre-2008 HFE DEM B Post-2008 HFE DEM

C Erosion-deposition map

Explanation

Elevation Change in C

(m)

DEM - Elevation in A and B

(m)

High: 585

Low: 485

0 50 100 meters

> 2.0

1.5 to 2.0

1.0 to 1.5

0.5 to 1.0

0.0 to 0.5

-1.0 to -0.5

-1.5 to -1.0

-0.5 to 0.0

-2.0 to -1.5

-3.0 to -2.0 ⇧ < -3.0

N

Figure 6. Comparison of repeat topographic and bathymetric surveys collected at site 172L illustrating Style 1 site 

response. A, Pre-2008 HFE digital elevation model (DEM). B, Post-2008 HFE DEM. C, The DEMs were differenced against 

each other to produce a map of spatially distributed elevation change. The solid black and white lines in A and B are the 

stage elevations reached by a flow of 227 m3

/s and 708 m3/s, respectively. The dashed blue line in C is the computational 

boundary described in figure 2. Flow in the main channel is right to left. The maps are inset on 2002 aerial photography. 

Northing and easting on the map projection is 1983 Arizona State Plane, central zone. 
16 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

A Areal and volumetric changes in eddy elevation 

B Areal and volumetric changes in channel elevation 

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

0

1,000

2,000

3,000

4,000

5,000

6,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

0

500

1,000

1,500

2,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

ELEVATION CHANGE, IN METERS ELEVATION CHANGE, IN METERS

0

500

1,000

1,500

2,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

ELEVATION CHANGE, IN METERS ELEVATION CHANGE, IN METERS

AREA, IN SQUARE METERSVOLUME, IN CUBIC METERS

AREA, IN SQUARE METERSVOLUME, IN CUBIC METERS

Erosion = 2,297 m2

Deposition = 7,104 m2

Erosion = 935 m3

Deposition = 4,592 m3

Net change = 3,657 m3

Erosion = 3,934 m2

Deposition = 9,638 m2

Erosion = 981 m3

Deposition = 2,486 m3

Net change = 1,595 m3

0

1,000

2,000

3,000

4,000

5,000

6,000

Figure 7. Selected daily photographs of the reattachment bar at site 172L. Flow in main channel is from left to right. The date 

and estimated discharges based on travel time between USGS stream-flow gaging stations on the Colorado River are given for 

each. A, A large, vegetated mid and high-elevation bar is present. B, The extent and height of site inundation by the 2008 HFE is 

shown. C, Post-HFE deposition. D, The bar was relatively stable after the onset of a higher flow regime (April 15, 2008). 

Figure 8. Areal and volumetric elevation-change distributions from the erosion-deposition map at site 172L shown in 

figure 6C. A, Total eddy. B, Main channel.
Results 17

219172 219362

597251

597471

219172 219362

597251

597471

219172 219362

597251

597471

A Pre-2008 HFE DEM B Post-2008 HFE DEM

C Erosion-deposition map

Explanation

Elevation Change in C

(m)

DEM - Elevation in A and B

(m)

High: 845

Low: 820

0 50 100 meters

> 2.0

1.5 to 2.0

1.0 to 1.5

0.5 to 1.0

0.0 to 0.5

-1.0 to -0.5

-1.5 to -1.0

-0.5 to 0.0

-2.0 to -1.5

-3.0 to -2.0

-4.0 to -3.0

-5.0 to -4.0

< -5.0

2.0 to 3.0

⇧

N

Figure 9. Comparison of repeat topographic and bathymetric surveys collected at site 44L illustrating a Style 2 sandbar 

response. A, Pre-HFE digital elevation model (DEM). B, Post-HFE DEM. C, The DEMs were differenced against each 

other to produce a map of spatially distributed elevation change. The solid black and white lines in A and B are the 

stage elevations reached by a flow of 227 m3

/s and 708 m3/s, respectively. The dashed blue line in C is the computational 

boundary described in figure 2. Flow in the main channel is from upper right to lower left. The maps are inset on 2002 

aerial photography. Northing and easting on the map projection is 1983 Arizona State Plane, central zone.
18 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Figure 10. Selected daily photographs of the sandbars at site 44L. In each sequence the separation bar is shown on 

the left and the reattachment bar is to the right. Flow in main channel is from left to right. The indicated discharges 

are estimates based on travel time between USGS stream-flow gaging stations on the Colorado River. A, Pre-2008 

HFE. Note the rocky shoreline on the upstream end of the separation bar and thick vegetation at high-elevation on the 

reattachment bar. B, The extent and height of site inundation by the 2008 HFE is shown. C, Post-2008 HFE response. D,

Erosion in the following months. 
Results 19

A Areal and volumetric changes in eddy elevation

B Areal and volumetric changes in channel elevation

0

1,000

2,000

3,000

4,000

5,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 11,693 m2

Deposition = 14,869 m2

0

500

1,000

1,500

2,000

2,500

3,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 23,750 m3

Deposition = 10,618 m3

Net change = -13,132 m3

0

1,000

2,000

3,000

4,000

5,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 5,174 m2

Deposition = 12,288 m2

ELEVATION CHANGE, IN METERS

AREA, IN SQUARE METERS

VOLUME, IN CUBIC METERS

ELEVATION CHANGE, IN METERS ELEVATION CHANGE, IN METERS

0

500

1,000

1,500

2,000

2,500

3,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 3,202 m3

Deposition = 7,317 m3

Net change = 4,115 m3

ELEVATION CHANGE, IN METERS

AREA, IN SQUARE METERS

VOLUME, IN CUBIC METERS

Figure 11. Areal and volumetric elevation-change distributions from the erosion-deposition map at site 44L shown in 

figure 9C. A, Total eddy. B, Main channel.

end of the eddy and in the adjacent channel, where more than 

2 m of sand deposited (figs. 15C, 16C). Erosion occurred 

elsewhere, especially in the upstream half of the eddy and in 

parts of the channel (fig. 15C). Scour of the reattachment-bar 

platform occurred to a depth of more than 5 m, resulting in 

a decrease in volume of sand above reference stage of 1,165 

m3. The volume of sand in the eddy above reference stage 

decreased to 23 percent of maximum. The adjacent main channel was also scoured to depths exceeding 5 m. The scour hole 

at the upstream end of the site deepened and lengthened. Erosion also occurred at the exit slope, where much of the dune 

field was removed (fig. 15B). 

The distributions of areal and volumetric change show 

that in nearly equal areas of the eddy (~2,000 m2) there was 

as much as 5.5 m of erosion and 2 m of deposition (fig. 17A). 

In contrast, a larger part of the channel, about 6,500 m2 was 

eroded about 3 to 5 m, and there was 1 to 2 m of sand deposited over a smaller area of the bed (fig. 17B). The greatest volume of sediment eroded from the eddy occurred where there 

was erosion of between 5 and 6 m of sand, and the greatest 

aggradation occurred where there was deposition of more 

than 1.5 m of sand. A scour depth of more than 3 m occurred 

over 43 percent of the entire site area, above and below reference stage. There was a total of 13,860 m3

 of net erosion 

in the eddy and 40,131 m3 of net erosion in the channel, and 

the site as a whole lost 53,991 m3 of sand. 

Spatial Pattern of Topographic Response

The three primary response styles occurred to different extents in different parts of Marble and Grand Canyons 

(fig. 18A). Response Style 1 (increase in sand volume at 

all elevations) occurred most commonly in Grand Canyon, 

and Style 2 (increase in sand volume above reference stage 

and decrease below reference stage) was most prevalent 

in Marble Canyon (fig. 18A). Style 3 (net decrease in sand 

volume above and below reference stage) occurred at 

least once in every sediment-transport-flux reach, but less 

commonly in CGC and WGC than in UMC and LMC. The 

Style 4 response (decrease in sand volume above reference 
20 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

222372 222512

571025

571205

222372 222512

571025

571205

222361 222501

571025

571205

A Pre-2008 HFE DEM B Post-2008 HFE DEM

C Erosion-deposition map

Explanation

Elevation Change in C

(m)

DEM - Elevation in A and B

(m)

High: 805

Low: 785

0 50 100 meters

2.0 to 3.0

1.5 to 2.0

1.0 to 1.5

0.5 to 1.0

0.0 to 0.5

-1.0 to -0.5

-1.5 to -1.0

-0.5 to 0.0

-2.0 to -1.5

-3.0 to -2.0

< -3.0

> 3.0

⇧

N

Figure 12. Comparison of repeat topographic and bathymetric surveys collected at 65R illustrating a variant of Style 2 

response. Flow in the main channel is from top to bottom. The maps are inset on 2002 aerial photography. Northing and 

easting on the map projection is 1983 Arizona State Plane, central zone. A, Pre-2008 HFE digital elevation model (DEM). B, 

Post-2008 HFE DEM. C, The DEMs were differenced against each other to produce a map of spatially distributed elevation 

change. The solid black and white lines in A and B are the stage elevations reached by a flow of 227 m3

/s and 708 m3/s, 

respectively. The dashed blue line in C is the computational boundary described in figure 2. 
Results 21

Figure 13. Selected daily photographs of the 

reattachment bar at site 65R. Flow in main channel is from 

bottom left to upper right. The indicated discharges are 

estimates based on travel time between USGS streamflow gaging stations on the Colorado River. A, The newly 

deposited reattachment bar. B, Onset of post-flood erosion. 

C, Extensive lateral cutbank retreat.

stage and increase below reference stage) occurred at only 

one site in EGC.

Despite downstream increase in the prevalence of Style 

1, sandbars in the high-elevation zone throughout Marble 

and Grand Canyons increased in thickness to about the 

same degree. However, the styles of the eddy and total-site 

responses were more variable. The median increase in sandbar 

thickness above reference stage was similar in all reaches 

(fig. 18B). In general, the occurrence of Style 1 (widespreaddeposition) increased longitudinally downstream, suggesting 

more sand was deposited than eroded. The variability between 

individual sites was greater in Marble Canyon and EGC; 

however, it is unclear whether that increased variability is the 

result of differences in behavior in those reaches or of greater 

study-site density. In contrast to the similarity between reaches 

of the median deposit response above the reference stage, 

the total-eddy median change in sandbar thickness increased 

from negative values in Marble Canyon to positive values 

downstream in Grand Canyon. However, the median change 

in total-eddy sandbar thickness in CGC was about half that in 

EGC and WGC. In contrast, the median change in total-site 

sand thickness progressively increased from 0.60 m of net 

erosion in upper Marble Canyon to 0.23 m of net deposition in 

western Grand Canyon (fig. 18B). 

Longevity: Changes from April to October 2008 

Sandbar erosion rates were greatest in the first 2 months 

following the 2008 HFE and declined thereafter, consistent 

with observations made following the 1996 HFE (Hazel and 

others, 1999). Between cessation of the high flow on March 10 

and the post-2008 HFE measurements on April 15, 2008, dam 

releases consisted of fluctuating flows with daily peaks of 390 

m3/s or less (fig. 3). During this period most newly deposited 

sandbars were stable or eroded gradually (table 4). On April 

15, 2008, release volumes increased and daily peak flows were 

between 425 and 462 m3/s. The daily photographs show that 

the rate of bar erosion accelerated at 5 out of 32 sites monitored by remote camera (table 4; fig. 19). The bulk of this 

erosion occurred at laterally migrating cutbanks in the new 

deposits (figs. 10D, 13C, 16D, 19C-E). These observations are 

consistent with the sandbar surveys, which show substantial 

decreases in sandbar thickness above the reference stage in the 

7 weeks between the post-2008 HFE surveys, conducted in 

late March and early April 2008, and the surveys conducted in 

May (fig. 20). During this 7-week period, the sandbar volume 

above reference stage eroded at a median rate of 5.3 m3

/day. 

From May to October 2008, the median erosion rate declined 

to 2.2 m3/day. The greatest erosion rate was observed at site 

65R, where the deposit above the reference stage eroded at a 

rate of 85 m3/day between April 3 and May 24, 2008. A small 

cutbank at the site was 0.2 m high when measured on April 3 

(fig. 13A). By the May 24 survey, the cutbank had migrated 

10 to 15 m into the bar and was approximately 0.4 m high 

(fig. 13B). Between the May and the October 2008 survey, the 
22 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Table 4. Observations of erosion and deposition from repeat photography at sites along the Colorado River 

in Marble and Grand Canyons.

[These changes are our observations based on available images from the fixed-camera network taken between April and October 

2008. S, bar was stable. GD, general deposition. GE, gradual erosion. RE, rapid erosion over a period ranging from 1 day to 2 

weeks. -, no images were available because of camera failure or the system was tampered with. Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in Grand Canyon 

National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing downstream.]

Site

ID

Observation interval

Notes

Feb. -2008 HFE

2008 

HFEApril

AprilMay May-Oct

3L S S S GD Minor erosion by late April. Deposition at low elevation 

upstream from the deposit.

8L S S GE S

16L S S GE GE Cutbank retreat. Surface modified by wind deflation on 

downstream end and aeolian dune development on 

upstream end.

22R S S GE GE Gradual sustained erosion by cutbank retreat during all 

months.

30R S - GE RE Mass failure of about half the bar platform on 6/3-6/4.

41R S - GE S Cutbank retreat.

44L S GE GE GE Cutbank retreat.

45L S GE RE RE Rapid initial cutbank retreat with rates slowing by July.

47R S S GE GE

50R S - S S

51L S S S S Very little new deposition to erode.

55R S - S S

58R S GE RE S Rapid erosion 4/15 – 4/16.

Cutbank retreat.

66L S S GE GE Cutbank development and evidence of wind deflation by 

April.

68R - RE - S Rapid erosion starting 4/17 via large-scale cutbank retreat. 

New deposit on upstream end mostly eroded by 5/8.

70R S S GE GE Cutbank retreat on the downstream end and formation of a 

large aeolian dune formation on the upstream end.

81L S S GE GE Large cutbank on downstream end but gradual retreat.

87L S S S S

91R GE GE S S Gully formed on 2/23 followed by a small rapid erosion 

event on 2/28.

104R S S GE - Minor cutbank development.
Results 23

119R S RE GE GE Cutbank development on downstream end immediately 

after 2008 HFE. Rapid cutbank retreat 4/15 – 4/18; 

gradual cutbank retreat 5/27-7/2.

122R S GE S S Cut bank retreat immediately after 2008 HFE.

123L S GE GE nc Gradual cut bank retreat after 2008 HFE.

137L S GE RE NC Gradual cutbank retreat in April followed by rapid cutbank 

retreat 4/15 – 4/18.

139R S S - -

145L S - S - 2-m cutbank on downstream end formed immediately after 

2008 HFE, but bar mostly stable.

172L S S S S Bar stable with rapid regrowth of buried vegetation.

183R - - GE, RE - Gradual cut bank retreat 4/11–4/15.

Rapid cut bank retreat 4/15–4/20.

194R - S S S

202R S S GE, RE S Gradual cutbank retreat 4/11–5/5.

Rapid cutbank retreat 5/5–5/6.

213L - S S S

225R S S S - Minor bank erosion.

Site

ID

Observation Interval

Notes

Feb. -2008 HFE

2008 

HFEApril

AprilMay May-Oct

Table 4. Observations of erosion and deposition from repeat photography at sites along the Colorado River 

in Marble and Grand Canyons.—Continued

[These changes are our observations based on available images from the fixed-camera network taken between April and October 

2008. S, bar was stable. GD, general deposition. GE, gradual erosion. RE, rapid erosion over a period ranging from 1 day to 2 

weeks. -, no images were available because of camera failure or the system was tampered with. Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in Grand Canyon 

National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, 

respectively, facing downstream.]

cutbank had migrated laterally another 20 to 25 m and was 0.5 

m high (fig. 13C). 

Another important process that potentially contributed to 

decreases in sandbar volume was surface deflation by wind. 

However, volume changes by surface deflation can also be 

offset by the deposition of eolian dunes as sand is redistributed 

to different areas of the bar. Eolian dunes initially measured in 

May had increased in size and extent by October (Draut and 

others, 2009, figs. 16-17, 41-42). Despite wind modification 

of sandbar surfaces, we estimate that the dominant erosional 

process was that of lateral cutbank retreat at approximately 60 

percent of the sites monitored with remote cameras (table 4). 

Other processes that result in bar erosion (that is, hillslope runoff and debris flows) were observed at one site (166L), where 

the eddy bar was incised by several distributary channels from 

September 2008 flooding in National Canyon, a tributary 

canyon to the Grand Canyon.

Campsite Area 

Sand deposition associated with the 2008 HFE increased 

campsite area. At 31 out of the 37 sites where campsite area 

was measured, the total campsite area (combined mid- and 

high-elevation zones) increased between the pre- and post2008 HFE measurements (appendix B; table 4). Increases in 

campsite area were as small as 3 m2

, and the greatest increase 

was more than 2,000 m2 (fig. 21). The median campsite 

area increased from 263 to 437 m2 (fig. 21). Campsite area 

increased in both mid- and high-elevation zones (fig. 22). 
24 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

A Areal and volumetric changes in eddy elevation 

B Areal and volumetric changes in channel elevation 

0

500

1,000

1,500

2,000

2,500

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 7,324 m2

Deposition = 8,529 m2

0

500

1,000

1,500

2,000

2,500

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 9,046 m2

Deposition = 32 m2

0

500

1,000

1,500

2,000

2,500

3,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 6,524 m3

Deposition = 11,818 m3

Net change = 5,294 m3

0

500

1,000

1,500

2,000

2,500

3,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 11,073 m3

Deposition = 4 m3

Net change = -11,069 m3

ELEVATION CHANGE, IN METERS

AREA, IN SQUARE METERS

VOLUME, IN CUBIC METERS

ELEVATION CHANGE, IN METERS

ELEVATION CHANGE, IN METERS ELEVATION CHANGE, IN METERS

AREA, IN SQUARE METERS

VOLUME, IN CUBIC METERS

Figure 14. Areal and volumetric elevation-change distributions from the erosion-deposition map at site 65R shown in 

figure 12C. A, Total eddy. B, Main channel.

Of the six sites where campsite area decreased, the largest 

decrease was 260 m2. 

Post-2008 HFE sandbar erosion resulted in declines in 

campsite area, particularly in the midelevation zone. Between 

measurements made in April and the measurements repeated 

in October 2008, total campsite area decreased at 31 of the 37 

sites. The median campsite area decreased from 437 to 319 

m2 (fig. 21). Midelevation campsite area in noncritical reaches 

was less than that measured in February. Despite the erosion 

measured between April and October, the total campsite area 

above the reference stage in October 2008 remained larger 

than the values measured in February 2008 (fig. 22).

To determine the effects of post-2008 HFE deposition and erosion on campsite area, the measured sandbar 

area and volume changes were compared to campsite area 

changes (fig. 23). Campsite area changes, including increases 

between February and April 2008 and decreases that occurred 

between April and October, were positively correlated with the 

magnitude of sandbar volume change (r2=0.72, significant at 

the 95-percent confidence level). Correlation of changes in 

campsite area and sandbar area were not as strong (r2=0.27). 

Sandbar volume has a better correlation with campsite area 

than with sandbar area because increases in volume frequently smooth irregular topography and temporarily bury 

vegetation; both of these processes can increase campsite 

area without affecting sandbar area.

The topographic changes described in the previous 

section show that sandbar deposition followed by cutbank 

retreat and resulting bar volume loss were the primary 

causes of the increases and then decreases in campsite area. 

As the result of the 2008 HFE, campsite area increased at 

all sites characterized by Style 1 and 2 responses. Deposition resulted in temporary burial of preexisting, vegetated 

portions of the sandbars (figs. 7A, 7C) and altered shorelines 

by covering rocks (figs. 10A, 10C). At several sites, campsite area increased dramatically where deposition in eddies 

created large, flat reattachment bars. For example, midelevation camp area at site 45L increased from 0 to 1,148 m2
Results 25

239990 240110

647848

648008

239983 240103

647848

648008

239989 240109

647848

648008

A Pre-2008 HFE DEM B. Post-2008 HFE DEM

C Erosion-deposition map

Explanation

Elevation Change in C

(m)

DEM - Elevation in A and B

(m)

High: 930

Low: 906

0 50 100 meters

> 2.0

1.5 to 2.0

1.0 to 1.5

0.5 to 1.0

0.0 to 0.5

-1.0 to -0.5

-1.5 to -1.0

-0.5 to 0.0

-2.0 to -1.5

-3.0 to -2.0

-4.0 to -3.0

-5.0 to -4.0

< -5.0

⇧

N

Figure 15. Comparison of repeat topographic and bathymetric surveys collected at site 3L. Flow in the main channel 

is from top to bottom. The maps are inset on 2002 aerial photography. Northing and easting on the map projection is 

1983 Arizona State Plane, central zone. A, Pre-HFE digital elevation model (DEM). B, Post-HFE DEM. C, The DEMs were 

differenced against each other to produce a map of spatially distributed elevation change. The solid black and white lines 

in A and B are the stage elevations reached by a flow of 227 m3

/s and 708 m3/s, respectively. The dashed blue line in C is 

the computational boundary described in figure 2. 
26 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

A Areal and volumetric changes in eddy elevation

B Areal and volumetric changes in channel elevation

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 

Erosion = 5,551 m2

Deposition = 2,046 m2

0

200

400

600

800

1,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 14,723 m2

Deposition = 2,084 m2

0 

1,000

2,000

3,000

4,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 

Erosion = 16,064 m3

Deposition = 2,204 m3

Net change = -13,860 m3

0

1,000

2,000

3,000

4,000

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5

Erosion = 41,936 m3

Deposition = 1,805 m3

Net change = -40,131 m3

ELEVATION CHANGE, IN METERS

AREA, IN SQUARE METERS AREA, IN SQUARE METERS

VOLUME, IN CUBIC METERS VOLUME, IN CUBIC METERS

ELEVATION CHANGE, IN METERS ELEVATION CHANGE, IN METERS

ELEVATION CHANGE, IN METERS

0

200

400

600

800

1,000

Figure 16. Selected daily photographs of the reattachment bar at site 3L. Flow in main channel is from left to right. The indicated 

discharges are estimates based on travel time between USGS stream-flow gaging stations on the Colorado River. A, A large, 

midelevation bar is present. B, The extent and height of site inundation by the 2008 HFE is shown. C, Upstream erosion and 

downstream deposition following the 2008 HFE. D, Erosion of the high-elevation bar between April and November 2008. 

Figure 17. Areal and volumetric elevation-change distributions from the erosion-deposition map at site 3L 

shown in figure 15C. A, The total eddy. B, Main channel.
Results 27

-2

0

2 UMC LMC EGC CGC WGC

Style 1

-2

0

2

Style 2

-2

0

2

Style 3

-2

0

2

0 50 100 150 200 250

Style 4

NET CHANGE IN SAND THICKNESS, IN METERS

SEDIMENT-FLUX MONITORING REACHES

-3

-2

-1

0

1

2

UMC LMC EGC CGC WGC

Above Reference Stage

Total Eddy

Total Site (Eddy + Channel)

DISTANCE DOWNSTREAM FROM LEES FERRY, IN RIVER MILES

NET CHANGE IN SAND THICKNESS WITHIN EDDY

A

B

Figure 18. Downstream variations at study sites and sediment-transport-flux monitoring 

reaches in response to 2008 HFE. Upper Marble Canyon (UMC), lower Marble Canyon (LMC), 

eastern Grand Canyon (EGC), central Grand Canyon (CGC), and western Grand Canyon (WGC) 

reaches are shown. A, Graph showing the distribution of total-eddy net change in thickness of 

sand for each response style with distance downstream. B, Boxplots showing the distribution 

of change for above-reference-stage, total-eddy, and total-site thickness within the five 

sediment flux monitoring reaches. A boxplot summarizes the distribution of data by showing 

the interquartile range (25th percentile to 75th percentile) as the height of the box, the median 

value as the center line within the box, lines drawn to smallest and largest values within one 

step (equal to 1.5 times the interquartile range) beyond either end of the box, and outliers 

(values greater than two steps outside the box) as circles.
28 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Figure 19. Photographic sequence at site 68R showing rapid 

erosion following the change in fluctuating flow regime at Glen 

Canyon Dam on April 15, 2008, when diurnal peak flows were 

increased to 425–462 m3

/s. Flow in main channel is from right to 

left. The indicated discharges are estimates based on travel time 

between USGS stream-flow gaging stations on the Colorado 

River. Flow rate at the time of each photograph is indicated. A,

The new sandbar one day after recession of the 2008 HFE. B, 

Little change evident 35 days later at the onset of the new flow. 

C, A new cutbank appeared within 1 day of arrival of the higher 

peak flows. D, Within 5 days a 1-2 m cutbank was eroding the 

thicker portion of the deposit. E, Within 10 days a large portion of 

the new deposit and associated camping area had eroded. 

(appendix B; table 4). The large increase in midelevation-zone 

area and volume that occurred at 65R is another example of 

this response (fig. 13A). Decreases in campsite area resulted 

largely from lateral cutbank retreat. The large decreases in 

midelevation-zone area at 65R and 68R between April and 

October 2008 are good examples of this process (figs. 13, 19). 

The development of eolian dunes and the occurrence of surface runoff were also noted as causing campsite area decreases 

at several sites, but these surface modifications were less 

significant factors than the erosion associated with cutbank 

retreat (table 4).

Comparison of Three High-Flow Experiments: 

1996, 2004, and 2008

Following the 2008 HFE, the volume of sand within the 

study sites was similar to or exceeded the volume of sand that 

existed following either the 1996 or 2004 HFEs. Cumulative 

probability distributions of total sand volume following each 

of the three high flows, expressed as the ratio of the volume 

measured following the high flow to the volume measured 

in February 1996, are depicted in figure 24. Although each 

sediment-transport-flux reach contains sites where the normalized sand volume was less than 1.0 (that is, less than the 

volume of sand measured in February 1996), the distribution 

curves for 2008 typically coincide with or are greater than the 

1996 and 2004 curves, indicating total-site sand volume was 

similar or greater in 2008 than for the previous two HFEs. The 

total sand volume following the 2008 HFE was greater than 

following the 1996 HFE in all reaches and was similar to the 

storage condition following the 2004 HFE for the two reaches 

(UMC and LMC) where total-site sand volume was measured 

that year. The median values from these distributions are 

shown for each respective reach in figure 25A. In contrast to 

the previous high flows, the median post-2008 HFE normalized sand volume was approximately equal to or greater than 

1.0 in all reaches.

The median sand volume above reference stage was 

similar to or exceeded the volumes following the previous 
Discussion and Conclusions 29

-1

0

1

2

3

4

0

250

500

750

1,000

1,250

1,500

J F M A M J J A S O N D

MONTHS, 2008 CALENDAR YEAR

DAILY MEAN DISCHARGE

IN CUBIC METERS PER SECOND

SAND THICKNESS

ABOVE REFERENCE STAGE,

IN METERS

Figure 20. Boxplot showing temporal sequence of deposit thickness above the reference stage compared to daily mean discharge 

following the 2008 HFE. A boxplot summarizes the distribution of data by showing the interquartile range (25th percentile to 75th 

percentile) as the height of the box, the median value as the center line within the box, lines drawn to smallest and largest values 

within one step (equal to 1.5 times the interquartile range) beyond either end of the box, and outliers (values greater than two steps 

outside the box) as circles. 

high flows in four out of the five sediment-flux monitoring reaches. Cumulative probability distributions for sand 

volumes above the reference stage are shown in figure 26. 

These plots indicate that the volume of sand above the 227-

m3/s stage was slightly less than 1996 and 2004 in UMC 

and similar or greater in LMC, EGC, CGC, and WGC. This 

pattern is also shown in figure 25B, where the median values 

are plotted for each reach. All median values, including that 

for upper Marble Canyon, are larger than 1.0, indicating that 

the volume of sand in sandbars above the reference stage was 

greater following the 2008 HFE than the volume measured 

before the 1996 HFE. 

Discussion and Conclusions

The 2008 HFE, which followed a period of greatly 

increased sand supply by the Paria River, resulted in a net 

increase in the size and volume of sandbars throughout Marble and Grand Canyons. One of the objectives of this third 

controlled-flood experiment was to evaluate whether a high 

flow conducted under sediment-enriched conditions could 

result in sandbar building throughout the system. These sandbar monitoring results show that there was (1) widespread 

high-elevation deposition and (2) less sand depletion at low 

elevation within eddies and the main channel than occurred 

during the two previous HFEs in 1996 and 2004. The net 

aggradational response also resulted in proportional increases 

in campsite area in both critical and noncritical reaches.

The increases in eddy deposit thickness above reference stage was similar in all sediment-transport flux reaches, 

while total-eddy response, strongly influenced by site-specific 

topographic changes below reference stage, was more variable. The response Style 1, in which all elevations increased in 

sand volume, occurred more commonly further downstream; 

upstream reaches had a response typically characterized by 

high-elevation deposition and low-elevation erosion (Style 2). 

The median change in total-site deposit thickness increased 

from negative values at sites located in Marble Canyon to 

positive values at sites located further downstream in Grand 

Canyon. Not every eddy aggraded in the same proportion, 

and there was at least one site in each sediment-transport-flux 

reach that experienced net erosion (for example, 3L, 55R, 

65R, 123L, 214R). Despite widespread deposition of high-elevation sandbars, this pattern was still accompanied by net erosion in some eddies, which also occurred during previous high 

flows (Andrews and others, 1999; Hazel and others, 1999; 

Topping and others, 2006a). Because sandbars above reference 

stage typically occupy a small percentage of total eddy area, 

large-scale low-elevation erosion, where it occurred, typically 

resulted in a net loss of sand from eddies and the adjacent 
30 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

0

2

4

6

8

10

12

14

16

18

NUMBER OF SITES

February 2008

A

0

2

4

6

8

10

12

14

16

18

NUMBER OF SITES

March 2008

B

0

2

4

6

8

10

12

14

16

18

200 600 1,000 1,400 1,800 2,200 2,600

NUMBER OF SITES

CAMPSITE AREA, IN SQUARE METERS

October 2008

C

median = 437 m2

median = 319 m2

median = 263 m2

Figure 21. Histograms showing the distribution of campsite area above the 

reference stage (combined mid- and high-elevation zones shown on figure 

2C). A, February 2008. B, April 2008. C, Six months after the 2008 HFE. 
Discussion and Conclusions 31

0 

1,000 

2,000 

3,000 

4,000 

5,000 

6,000 

7,000 

IN SQUARE METERS

A Critical reaches

Feb. 2008 Apr. 2008 Oct. 2008

MIDELEVATION HIGH-ELEVATION

0 

2,000 

4,000 

6,000 

8,000 

10,000 

IN SQUARE METERS

B Noncritical reaches

Feb. 2008 Oct. 2008

MIDELEVATION HIGH-ELEVATION

AVERAGE CAMPSITE AREA, AVERAGE CAMPSITE AREA,

Apr. 2008

Figure 22. Average campsite area above the reference stage before, after, and about 

6 months after the 2008 HFE. Error bars show plus and minus 10 percent of total. A, 

Critical reaches. B, Noncritical reaches. 

Figure 23. The 

relation of change 

in campsite area to 

change in sandbar 

area and volume for 

two time intervals in 

2008, pre- to postflood 

(February-April) and 

the following 6 months 

(April-October). A 

linear regression fit 

for both time intervals 

combined is shown. -4,000 -2,000 0 2,000 4,000

-4,000

-2,000

0

2,000

4,000

6,000

8,000

R2 = 0.27

-4,000-2,000 0 2,000 4,000 6,000 8,000

R2 = 0.72

Febuary to April

April to October

CAMPSITE AREA CHANGE

ABOVE REFERENCE STAGE, 

IN SQUARE METERS

SANDBAR AREA CHANGE

ABOVE REFERENCE STAGE,

IN SQUARE METERS

SANDBAR VOLUME CHANGE

ABOVE REFERENCE STAGE,

IN CUBIC METERS
32 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

0.2 0.3 0.4 0.5 0.6 0.7 0.80.9 1 2

0

20

40

60

80

100

UMC

RM 22 - 32

1996

2004

2008

PERCENTAGE OF SITES WITH NORMALIZED SAND 

VOLUME LESS THAN INDICATED VALUE

0.2 0.3 0.4 0.5 0.6 0.7 0.80.9 1 2

0

20

40

60

80

100

LMC

RM 43 - 65

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SAND 

VOLUME LESS THAN INDICATED VALUE

NORMALIZED SAND VOLUME

0.2 0.3 0.4 0.5 0.6 0.7 0.80.9 1 2

0

20

40

60

80

100 EGC

RM 68 - 123

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SAND 

VOLUME LESS THAN INDICATED VALUE

0.2 0.3 0.4 0.5 0.6 0.7 0.80.9 1 2

0

20

40

60

80

100

CGC

RM 137 - 172

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SAND 

VOLUME LESS THAN INDICATED VALUE

0.2 0.3 0.4 0.5 0.6 0.7 0.80.9 1 2

0

20

40

60

80

100

WGC

RM 194 - 225

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SAND 

VOLUME LESS THAN INDICATED VALUE

Figure 24. Cumulative probability distributions of 

total-site sand volume following the 1996, 2004, and 

2008 HFEs. Sand volumes are normalized by dividing 

the volume measured following each high flow by the 

volume measured before the 1996 HFE and shown on 

a logarithmic scale. Distributions are shown for upper 

Marble Canyon (UMC), lower Marble Canyon (LMC), 

eastern Grand Canyon (EGC), central Grand Canyon 

(CGC), and western Grand Canyon (WGC). Note that no 

data were collected in EGC, CGC, and WGC in 2004. RM, 

river mile measured downstream from Lees Ferry (RM 0).
Discussion and Conclusions 33

0.1

1

10

TOTAL NORMALIZED SAND VOLUME FOR STUDY SITE

UMC LMC EGC CGC WGC

SEDIMENT-FLUX MONITORING REACHES

1996

2004

2008

0.1

1

10

NORMALIZED SAND VOLUME ABOVE REFERENCE STAGE

UMC LMC EGC CGC WGC

SEDIMENT-FLUX MONITORING REACHES

1996

2004

2008

A

B

Figure 25. Boxplots showing normalized sand volumes of all sites within each sediment-transport-flux 

monitoring reach. Sand volumes are normalized by dividing the volume measured following each high flow by the 

volume measured before the 1996 HFE and shown on a logarithmic scale. Upper Marble Canyon (UMC), lower 

Marble Canyon (LMC), eastern Grand Canyon (EGC), central Grand Canyon (CGC), and western Grand Canyon 

(WGC) reaches are shown. A, Total-site volume. B, Above-reference-stage volume. A boxplot summarizes the 

distribution of data by showing the interquartile range (25th percentile to 75th percentile) as the height of the box, 

the median value as the center line within the box, lines drawn to smallest and largest values within one step 

(equal to 1.5 times the interquartile range) beyond either end of the box, and outliers (values greater than two 

steps outside the box) as circles.
34 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

0.1 1

0

20

40

60

80

100

UMC

RM 22 - 32

1996

2004

2008

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SANDBAR

VOLUME ABOVE REFERENCE STAGE LESS THAN INDICATED VALUE

3 0.1 1

0

20

40

60

80

100

LMC

RM 43 - 65

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SANDBAR

VOLUME ABOVE REFERENCE STAGE LESS THAN INDICATED VALUE

3

0.1 1

0

20

40

60

80

100 EGC

RM 68 - 123

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SANDBAR

VOLUME ABOVE REFERENCE STAGE LESS THAN INDICATED VALUE

3 0.1 1

0

20

40

60

80

100

CGC

RM 137 - 172

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SANDBAR

VOLUME ABOVE REFERENCE STAGE LESS THAN INDICATED VALUE

3

0.1 1

0

20

40

60

80

100 WGC

RM 183 - 225

NORMALIZED SAND VOLUME

PERCENTAGE OF SITES WITH NORMALIZED SANDBAR

VOLUME ABOVE REFERENCE STAGE LESS THAN INDICATED VALUE

3

Figure 26. Cumulative probability distributions of sand 

volume above reference stage following the 1996, 2004, and 

2008 HFEs. Sand volumes are normalized by dividing the 

volume measured following each high flow by the volume 

measured before the 1996 HFE and shown on a logarithmic 

scale. Distributions are shown for upper Marble Canyon 

(UMC), lower Marble Canyon (LMC), eastern Grand Canyon 

(EGC), central Grand Canyon (CGC), and western Grand 

Canyon (WGC). RM, river mile measured downstream from 

Lees Ferry (RM 0).
Acknowledgements 35

channel (fig. 18). These results are similar to those observed 

in association with the 1996 HFE, where the source of sand 

deposited at the sites differed between sites located in Marble 

and Grand Canyons (Schmidt, 1999). 

Direct comparison of the topographic response of 

sandbars with those observed during two previous high-flow 

experiments conducted in 1996 and 2004 indicate that the 

total-site sand volume was similar or greater following the 

2008 HFE in all sediment-transport-flux monitoring reaches. 

These results suggest that the antecedent condition prior to 

controlled flooding is an important factor in the resulting 

sandbar response. During the 2004 high flow, increases in 

sand volume above reference stage were much greater in 

UMC than in LMC and sand volume above reference stage 

in EGC decreased to a magnitude similar to that measured 

before the 1996 high flow. In contrast, sand volume above 

the reference stage following the 2008 HFE was similar to 

or larger than sand volume for the same sites following the 

1996 HFE in all reaches. The greater consistency among the 

sediment-transport-flux monitoring reaches observed following the 2008 HFE is consistent with the observation that 

accumulated sand was more evenly distributed throughout 

all geomorphic reaches preceding the 2008 HFE than it was 

before the 2004 HFE. 

In the 6-month period following the 2008 HFE, readjustment of the newly aggraded eddy bars to regular dam operations led to rapid, but declining rates of erosion. Post-2008 

HFE sandbar erosion also resulted in concomitant decreases in 

campsite area. Although newly deposited sandbars may differ 

in susceptibility to erosion during normal, diurnal fluctuatingflow dam operations associated with the modified low fluctuating flow operation, previous work has shown that elevated 

fluctuating flows following past sandbar-building experiments 

result in rapid, systemwide erosion of sandbars of all types 

(Schmidt and Graf, 1990; Hazel and others, 1999; Rubin and 

others, 2002). Observations by remote camera indicate that 

sandbars were stable or gradually eroding between the 2008 

HFE and the April 2008 sandbar measurements. Erosion 

rates were highest between April and May and lower between 

May and October 2008. The transition in dam operations 

from spring fluctuating flows to early summer fluctuating 

flows occurred immediately after the April sandbar measurements, and the remote camera observations show high rates of 

cutbank retreat at several sites from April to May 2008. These 

observations suggest that the transition from the spring flows 

to the higher volume early summer flows caused accelerated 

sandbar erosion, although the rate of erosion that would have 

occurred under a different flow regime is not known. Similarly, repeat daily photos of one of the study sites (30R) immediately following the 2004 HFE also demonstrated stability of 

a rebuilt sandbar until higher and more widely ranging flow 

fluctuations began in January 2005.

The marked decrease in erosion rates between the early 

summer flows and the higher, late summer flows is likely owing 

to the fact that many of the sandbars had substantially eroded 

by the time the late summer flows started (fig. 20). Previous 

studies have shown that erosion rates decrease as the availability of erodible sediment decreases (Schmidt and others, 1995; 

Hazel and others, 1999) or as a stable slope is reached (Budhu 

and Gobin, 1994). Thus, much of the redistribution of sand 

had already occurred by the time that the late summer fluctuations occurred, thereby limiting the potential of lower, steady 

flows released from the dam in September and October 2008 to 

enhance stability of the 2008 HEF sandbar deposits.

Monitoring and prediction of sandbar response to experimental controlled floods at Glen Canyon Dam are complicated 

by variations in channel and debris-fan geometry (Schmidt and 

Graf, 1990), the cumulative downstream nature of the limited 

sand supply, and the physics that governs sediment transport 

(Topping and others, 2000; Rubin and Topping, 2001; Topping and others, 2007; Rubin and Topping, 2008), as well as 

because of the spatial and temporal variability of study sites 

utilized for monitoring (Schmidt and others, 2004). It is still 

unclear whether controlled floods will provide a sustainable 

strategy for longer term habitat restoration and maintenance 

using only sand supplied by the remaining tributary sources of 

sand below the dam. This will require integration of the results 

described in this report with results from other studies and 

continued experimentation, monitoring, and evaluation.

Acknowledgements

This study was supported by the U.S. Geological Survey 

and Bureau of Reclamation through funds provided by the 

Grand Canyon Monitoring and Research Center. It is offered 

in tribute to the late Greg Sponenburgh, whose original surveys in 1990 inspired methodologies that remain unchanged 

today. Permission to work in the study area was granted by 

Grand Canyon National Park. We thank many people for 

assistance in collecting field data, including Eric Kellerup, 

Rod Parnell, Meagan Polino, Nathan Schott, and Emily 

Thompson. Nathan Schott did most of the bathymetry processing and work leading to topographic comparisons. Keith 

Kohl is thanked for assisting with various aspects of the study, 

including data collection and ensuring an accurate geodetic 

control network for consistent reference of data acquisition. 

Boat logistics were provided by Humphrey Summit Support. 

GIS support was provided by James Androwski and Rob Ross. 

David Topping shared ideas that led to some of the techniques 

used in this report. We also thank Amy Draut, Helen Fairley, 

Ted Melis, and Scott Wright for positive discussion and comments that helped clarify and focus this report. Finally, we 

thank Chris Magirl and two anonymous reviewers for their 

constructive comments. 
36 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

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Applications, v. 11, no. 3, p. 635–643.

Phillips, B.G., Johnson, R.A., Phillips, A.M., III, and Brian, 

N.J., 1986, Monitoring the effects of recreational use on 

Colorado River beaches in Grand Canyon National Park: 

Museum of Northern Arizona Bulletin 55, 131 p. 

Rubin, D.M., and Topping, D.J., 2008, Correction to “Quantifying the relative importance of flow regulation and 

grain-size regulation of suspended-sediment transport 

α, and tracking changes in bed-sediment grain size β”: 

Water Resources Research, v. 44, W09701, 5 p., doi: 

10.1029/2008WR006819 [http://www.agu.org/journals/wr/

wr0809/2008WR006819/2008WR006819.pdf, last accessed 

January 17, 2010].

Rubin, D.M., and Topping, D.J., 2001, Quantifying the relative importance of flow regulation and grain-size regulation 

of suspended-sediment transport α, and tracking changes in 

bed-sediment grain size β: Water Resources Research, v. 37, 

no. 1, p. 133–146 [http://www.agu.org/journals/wr/v037/

i001/2000WR900250/2000WR900250.pdf, last accessed 

January 12, 2010].

Rubin, D.M., Schmidt, J.C., and Moore, J.N., 1990, Origin, 

structure, and evolution of a reattachment bar, Colorado 

River, Grand Canyon, Arizona: Journal of Sedimentary 

Petrology, v. 60, no. 6, p. 982–991.

Rubin, D.M., Anima, R.A., and Sanders, R., 1994, Measurements of sand thickness in Grand Canyon, Arizona, and 

conceptual model for characterizing changes in sandbar 

volume through time and space: U.S. Geological Survey 

Open-File Report 94-597, 9 p. 

Rubin, D.M., Nelson, J.M., and Topping, D.J., 1998, Relation 

of inversely graded deposits to suspended-sediment grainsize evolution during the 1996 flood experiment in Grand 

Canyon: Geology, v. 26, no. 2, p. 99–102.

Rubin, D.M., Topping, D.J., Schmidt, J.C., Hazel, J.E.J., 

Kaplinski, M., and Melis, T.S., 2002, Recent sediment 

studies refute Glen Canyon Dam hypothesis: Eos (Transactions, American Geophysical Union), v. 83, no. 25, p. 273, 

277–278.

Schmidt, J.C., 1990, Recirculating flow and sedimentation 

in the Colorado River in Grand Canyon, Arizona: Journal 

of Geology, v. 98, no. 5, p. 709–724 [http://www.journals.

uchicago.edu/doi/abs/10.1086/629435, last accessed 

December 10, 2009].

Schmidt, J.C., 1999, Summary and synthesis of geomorphic 

studies conducted during the 1996 controlled flood in Grand 

Canyon, in Webb, R.H., Schmidt, J.C., Marzolf, G.R., and 

Valdez, R.A., eds., The controlled flood in Grand Canyon; 

scientific experiment and management demonstration: 

Washington, D.C., American Geophysical Union, Geophysical Monograph Series, v. 110, p. 329–341.

Schmidt, J.C., and Graf, J.B., 1990, Aggradation and degradation of alluvial sand deposits, 1965–1986, Colorado River, 

Grand Canyon National Park, Arizona: U.S. Geological 

Survey Professional Paper 1493, 74 p. 

Schmidt, J.C., and Rubin, D.M., 1995, Regulated stream-flow, 

fine-grained deposits, and effective discharge in canyons 

with abundant debris fans, in Costa, J.E., Miller, A.J., Potter, 

K.W., and Wilcock, P.R., eds., Natural and anthropogenic 

influences in fluvial geomorphology: Washington D.C., 

American Geophysical Union, Geophysical Monograph 

Series, v. 89, p. 177–195.

Schmidt, J.C., Grams, P.E., and Webb, R.H., 1995, Comparison of the magnitude of erosion along two large regulated 

rivers: Journal of the American Water Resources Association, v. 31, no. 4, p. 617–631.

Schmidt, J.C., Grams, P.E., and Leschin, M.F., 1999, Variation 

and magnitude of deposition and erosion in three long-term 

(8–12 km) reaches as determined by photographic analyses, 

in Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, 

R.A., eds., The controlled flood in Grand Canyon; scientific 

experiment and management demonstration: Washington, 

D.C., American Geophysical Union, Geophysical Monograph Series, v. 110, p. 185–204.

Schmidt, J.C., Topping, D.J., Grams, P.E., and Hazel, J.E., Jr., 

2004, 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: Logan, 

Utah., Utah State University, submitted to U.S. Geological 

Survey, Grand Canyon Monitoring and Research Center, 

cooperative agreement no. 1425-98-FC-40-22640, 107 p. 
38 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Schmidt, J.C., Grams, P.E., and Webb, R.H., 2005, Comparison of the magnitude of erosion along two large regulated 

rivers: Journal of the American Water Resources Association, v. 31, no. 4, p. 617–631.

Schmidt, J.C., Topping, D.J., Rubin, D.M., Hazel, J.E., Jr., 

Kaplinski, M., Wiele, S.M., and Goeking, S.A., 2007, 

Streamflow and sediment data collected to determine the 

effects of low summer steady flows and habitual maintenance flows in 2000 on the Colorado River between Lees 

Ferry and Bright Angel Creek, Arizona: U.S. Geological 

Survey Open-File Report 2007-1268, 79 p. 

Stevens, L.E., 1990, The Colorado River in Grand Canyon—a 

guide: Flagstaff, Ariz., Red Lake Books, 115 p.

Topping, D.J., Rubin, D.M., and Vierra, L.E., Jr., 2000, Colorado River sediment transport pt.1—natural sediment supply limitations and the influence of the Glen Canyon Dam: 

Water Resources Research, v. 36, no. 2, p. 515–542.

Topping, D.J., Schmidt, J.C., and Vierra, L.E., Jr., 2003, Computation and analysis of the instantaneous-discharge record 

for the Colorado River at Lees Ferry, Arizona—May 8, 

1921, through September 30, 2000: U.S. Geological Survey 

Professional Paper 1677, 118 p. 

Topping, D.J., Rubin, D.M., Schmidt, J.C., Hazel, J.E., Jr., 

Melis, T.S., Wright, S.A., Kaplinski, M., Draut, A.E., and 

Breedlove, M.J., 2006a, Comparison of sediment-transport 

and bar-response results from the 1996 and 2004 controlledflood experiments on the Colorado River in Grand Canyon: 

[CD-ROM ] Proceedings of the Eighth Federal Interagency 

Sedimentation Conference, Reno, Nev., April 2–6, 2006, 

ISBN 0-9779007-1-1.

Topping, D.J., Wright, S.A., Rubin, D.M., and Melis, T.S., 

2006b, High-resolution monitoring of suspended-sediment 

concentration and grain size in the Colorado River using 

laser diffraction instruments and a three-frequency acoustic system: [CD-ROM ] Proceedings of the Eighth Federal 

Interagency Sedimentation Conference, Reno, Nev., April 

2–6, 2006, ISBN 0-9779007-1-1.

Topping, D.J., Rubin, D.M., and Melis, T.S., 2007, Coupled 

changes in sand grain size and sand transport drive by 

changes in the upstream supply of sand in the Colorado 

River, relative importance of changes in bed-sand grain size 

and bed-sand area: Sedimentary Geology, v. 202, no. 2, p. 

538–561.

Turner, R.M., and Karpiscak, M.M., 1980, Recent vegetation 

changes along the Colorado River between Glen Canyon 

Dam and Lake Mead, Arizona: U.S. Geological Survey 

Professional Paper 1132, 125 p. 

U.S. Department of the Interior, 1995, Operation of Glen Canyon Dam final environmental impact statement, Colorado 

River Storage Project, Coconino County, Arizona: Salt Lake 

City, Utah, U.S. Bureau of Reclamation, Upper Colorado 

Regional Office, 337 p. 

U.S. Department of the Interior, 2008, Final environmental 

assessment for experimental releases from Glen Canyon 

Dam, Arizona, 2008 through 2012: Salt Lake City, Utah, 

U.S. Bureau of Reclamation, Upper Colorado Region, 68 p. 

[http://www.usbr.gov/uc/envdocs/ea/gc/2008hfe/index.html, 

last accessed January 13, 2010]. 

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[Spatial database, GIS.BASE_GCMRC_TenthMile] 1st 

rev. ed.: Grand Canyon Monitoring and Research Center 

[http://www.gcmrc.gov/products/ims/, last accessed June 

16, 2006].

Webb, R.H., Pringle, P.T., and Rink, G.R., 1989, Debris flows 

from tributaries of the Colorado River in Grand Canyon 

National Park, Arizona: U.S. Geological Survey Professional Paper 1492, 39 p. 

Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, R.A., 

1999, The controlled flood in Grand Canyon—scientific 

experiment and management demonstration: Washington, 

D.C., American Geophysical Union, Geophysical Monograph Series, v. 110, 367 p.

Wiele, S.M., and Torizzo, M., 2005, Modeling of sand deposition in archeologically significant reaches of the Colorado 

River in Grand Canyon, USA, in Bates, P.D., Lane, S.N., 

and Ferguson, R.I., eds., Computational fluid dynamics: 

applications in environmental hydraulics: Hoboken, N.J., 

Wiley, p. 357–394.

Wiele, S.M., Garf, J.B., and Smith, J.D., 1996, Sand deposition in the Colorado River in the Grand Canyon from flooding of the Little Colorado River: Water Resources Research, 

v. 32, no. 12, p. 3579–3596.

Wilson, R.P., 1986, Sonar patterns of the Colorado riverbed, 

Grand Canyon, in Fourth Federal Interagency Sedimentation Conference, Las Vegas, Nev., March 24–27, 1986, 

Proceedings, v. 2, p. 5-133, 135-142.

Wright, S.A., Melis, T.S., Topping, D.J., and Rubin, D.M., 

2005, Influence of Glen Canyon Dam operations on downstream sand resources of the Colorado River in Grand Canyon, in Gloss, S.P., Lovich, J.E., and Melis, T.S. eds., The 

state of the Colorado River ecosystem in Grand Canyon: 

U.S. Geological Survey Circular 1282, p. 17–31. 
Appendixes 39

Appendixes A–B
40 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Appendix A. Summary of study sites and types of data collected, 

Colorado River in Marble and Grand Canyons 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in 

Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing downstream. Date of study is that of topographic survey (month/day/year). Discharges were estimated from the water surface during 

topographic surveys using the stage-discharge relations of Hazel and others (2006b). √, data were collected. -, no data were collected or data were 

not recoverable.]

Site 

ID Date Discharge (m3/s)

Topographic 

survey

Bathymetric

survey

Campsite 

survey

Time-lapse

photography

Scour 

chains

1R

02/02/08

03/28/08

05/17/08

10/11/08

285

278

232

355

√

√

√

√

-

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

3L

02/02/08

03/28/08

05/17/08

10/11/08

322

352

318

394

√

√

√

√

√

√

-

-

-

-

-

-

√

√

√

√

-

-

-

-

8L

02/02/08

03/28/08

10/11/08

253

313

360

√

√

√

-

-

-

√

√

√

-

√

√

-

-

-

-

9L

02/03/08

03/29/08

05/17/08

10/12/08

252

300

369

358

√

√

√

√

-

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

16L

02/03/08

03/29/08

10/12/08

282

279

384

√

√

√

√

√

-

√

√

√

-

√

?

-

-

-

22R

02/03/08

03/29/08

05/17/08

10/12/08

284

267

265

366

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

-

-

-

-

24L

02/04/08

03/29/08

10/12/08

255

257

368

√

√

√

-

-

-

√

√

√

-

-

-

-

-

-

-

29L

02/04/08

03/30/08

09/22/08

287

246

309

√

√

√

-

-

-

√

√

√

-

-

-

-

-

-

30R

02/04/08

03/30/08

05/19/08

10/13/08

266

257

336

365

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

√

-

-

-

32R

02/05/08

03/30/08

10/13/08

265

235

379

√

√

√

√

√

-

√

√

-

-

-

-

-

-

-

-

33L

02/05/08

03/30/08

10/13/08

264

220

347

√

√

√

-

√

-

-

-

-

-

-

-

-

-

-

35L

02/05/08

03/30/08

10/13/08

272

212

348

√

√

√

√

√

√

√

√

√

-

-

-

-

-

-

-
Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons 41

Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons. —Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) 

in Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, 

respectively, facing downstream. Date of study is that of topographic survey (month/day/year). Discharges were estimated from the water 

surface during topographic surveys using the stage-discharge relations of Hazel and others (2006b). √, data were collected. -, no data were collected or data were not recoverable.]

Site 

ID Date Discharge (m3

/s)

Topographic 

survey

Bathymetric

survey

Campsite 

survey

Time-lapse

photography

Scour 

chains

41R

02/05/08

03/31/08

05/19/08

10/14/08

303

316

294

357

√

√

√

√

√

√

-

-

√

√

-

√

√

-

√

√

-

-

-

-

43L

02/06/08

03/31/08

05/19/08

10/14/08

282

273

301

368

√

√

√

√

√

√

-

-

√

√

-

√

-

-

-

-

-

-

-

-

44L

02/06/08

03/31/08

05/19/08

10/14/08

270

237

-

345

√

√

-

√

√

√

-

-

√

√

-

√

√

√

√

√

√

-

-

-

45L

02/07/08

03/31/08

05/20/08

10/15/08

320

227

385

358

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

-

-

-

-

47R

02/07/08

03/31/08

05/20/08

10/15/08

339

307

343

361

√

√

√

√

-

-

√

√

√

√

-

√

√

√

√

√

-

-

-

-

49R

02/07/08

03/31/08

05/20/08

09/24/08

253

282

394

346

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

49L

02/07/08

04/01/08

05/20/08

09/24/08

253

256

343

358

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

50R

04/01/08

05/20/08

10/15/08

292

309

360

√

√

√

√

-

-

√

-

√

√

√

√

-

-

-

51L

02/08/08

04/02/08

05/21/08

10/15/08

335

328

414

358

√

√

√

√

√

√

-

-

√

√

-

√

-

-

-

-

-

-

-

-

54R

02/08/08

04/02/08

10/16/08

334

319

358

√

√

√

√

√

-

-

-

-

-

-

-

√

-

-
42 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons. —Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in 

Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing downstream. Date of study is that of topographic survey (month/day/year). Discharges were estimated from the water surface during 

topographic surveys using the stage-discharge relations of Hazel and others (2006b). √, data were collected. -, no data were collected or data were 

not recoverable.]

Site 

ID Date Discharge (m3/s)

Topographic 

survey

Bathymetric

survey

Campsite 

survey

Time-lapse

photography

Scour 

chains

55R

02/08/08

04/02/08

05/21/08

10/16/08

318

275

328

348

√

√

√

√

√

√

-

-

-

√

-

-

√

√

√

√

-

-

-

-

56R

04/02/08

05/21/08

10/16/08

252

303

372

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

58L

02/08/08

04/03/08

05/23/08

10/16/08

307

337

-

368

√

√

√

√

-

-

-

-

-

-

-

-

√

√

√

√

-

-

-

-

62R

02/09/08

04/03/08

10/17/08

352

380

356

√

√

√

√

√

-

√

√

√

-

-

-

-

-

-

63L

02/09/08

04/03/08

05/24/08

10/17/08

337

340

397

340

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

65R

02/09/08

04/03/08

05/24/08

10/17/08

372

332

410

387

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

65L

02/09/08

04/04/08

05/24/08

10/17/08

375

347

424

368

√

√

√

√

√

√

-

-

-

-

-

-

√

√

√

√

-

-

-

-

66L

02/10/08

04/04/08

05/24/08

10/18/08

265

315

353

363

√

√

√

√

-

-

-

-

-

-

-

-

√

√

√

√

-

-

-

-

68R

02/10/08

04/05/08

05/25/08

10/18/08

279

341

420

344

√

√

√

√

√

√

-

-

-

-

-

-

√

√

√

√

-

-

-

-

70R

02/10/08

04/05/08

10/18/08

345

372

370

√

√

√

-

-

-

-

-

-

√

-

√

-

-

-

81L

02/11/08

04/06/08

05/25/08

09/26/08

303

293

405

362

√

√

√

√

-

-

-

-

√

√

-

√

√

√

√

-

-

-
Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons 43

Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons. —Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in 

Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing downstream. Date of study is that of topographic survey (month/day/year). Discharges were estimated from the water surface during 

topographic surveys using the stage-discharge relations of Hazel and others (2006b). √, data were collected. -, no data were collected or data were 

not recoverable.]

Site 

ID Date Discharge (m3/s)

Topographic 

survey

Bathymetric

survey

Campsite 

survey

Time-lapse

photography

Scour 

chains

84R

02/11/08

04/06/08

09/27/08

309

279

353

√

√

√

-

-

-

√

√

-

-

-

-

-

-

-

87L

02/11/08

04/06/08

10/19/08

334

329

368

√

√

√

√

√

-

√

√

-

√

√

√

-

-

-

88R

02/11/08

04/06/08

10/19/08

327

300

337

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

91R

02/12/08

04/07/08

10/19/08

346

280

372

√

√

√

-

-

-

-

-

-

√

√

√

-

-

-

93L

02/12/08

04/07/08

10/20/08

322

276

360

√

√

√

√

√

-

√

√

√

-

-

-

-

-

-

104R

02/12/08

04/07/08

10/20/08

323

303

360

√

√

√

√

√

-

√

√

√

√

√

√

-

-

-

119.4r

02/12/08

04/08/08

10/21/08

319

299

372

√

√

√

√

√

-

√

√

√

√

√

√

√

-

-

119.8r

02/12/08

04/08/08

05/27/08

10/21/08

317

318

386

368

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

122R

02/12/08

04/08/08

05/27/08

10/21/08

343

337

411

363

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

√

-

-

-

123L

02/13/08

04/08/08

05/28/08

10/21/08

358

286

360

376

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

-

-

-

-

137L

02/13/08

04/09/08

10/22/08

336

284

362

√

√

√

√

√

-

√

√

√

√

√

√

-

-

-
44 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons. —Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in 

Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing downstream. Date of study is that of topographic survey (month/day/year). Discharges were estimated from the water surface during 

topographic surveys using the stage-discharge relations of Hazel and others (2006b). √, data were collected. -, no data were collected or data were 

not recoverable.]

Site 

ID Date Discharge (m3

/s)

Topographic 

survey

Bathymetric

survey

Campsite 

survey

Time-lapse

photography

Scour 

chains

139R

02/13/08

04/09/08

10/22/08

346

299

380

√

√

√

√

√

-

√

√

√

√

√

√

-

-

-

145L

02/13/08

04/09/08

05/29/08

10/22/08

346

327

327

365

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

-

-

-

-

165R

02/14/08

04/10/08

05/29/08

09/30/08

351

325

329

367

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

166L

02/14/08

04/10/08

05/29/08

10/23/08

336

286

343

340

√

√

√

√

-

-

-

-

√

√

-

√

-

-

-

-

√

-

-

-

172L

02/14/08

04/10/08

05/30/08

10/23/08

344

297

362

346

√

√

√

√

√

√

-

-

-

-

-

-

√

√

√

-

√

-

-

-

183R

02/15/08

04/11/08

05/31/08

10/24/08

386

363

417

369

√

√

√

√

-

√

-

-

√

√

-

√

√

-

√

-

-

-

-

-

194L

02/15/08

04/11/08

05/31/08

10/24/08

376

349

377

363

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

-

-

-

-
Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand Canyons 45

Appendix A. Summary of study sites and types of data collected, Colorado River in Marble and Grand 

Canyons. —Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river 

mile 0) in Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right 

sides of the river, respectively, facing downstream. Date of study is that of topographic survey (month/day/year). Discharges were 

estimated from the water surface during topographic surveys using the stage-discharge relations of Hazel and others (2006b). √, 

data were collected. -, no data were collected or data were not recoverable.]

Site 

ID Date Discharge (m3/s)

Topographic 

survey

Bathymetric

survey

Campsite 

survey

Time-lapse

photography

Scour 

chains

201R

02/16/08

04/11/08

06/01/08

10/25/08

371

366

405

369

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

202R

02/16/08

04/11/08

06/01/08

10/25/08

381

322

418

366

√

√

√

√

√

√

-

-

√

√

-

√

√

√

√

√

-

-

-

-

213L

02/17/08

04/12/08

06/02/08

10/26/08

344

338

433

362

√

√

√

√

√

√

-

-

√

√

-

√

√

√

-

√

-

-

-

-

214R

02/17/08

04/12/08

06/02/08

10/26/08

363

343

453

374

√

√

√

√

√

√

-

-

-

-

-

-

-

-

-

-

-

-

-

-

220R

02/17/08

04/12/08

10/26/08

449

415

438

√

√

√

√

√

-

√

√

√

-

-

-

-

-

-

225R

02/18/08

04/13/08

06/03/08

10/26/08

372

328

391

364

√

√

√

√

√

√

-

-

-

-

-

-

√

√

-

√

-

-

-

-
46 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble 

and Grand Canyons

Table B1. High-elevation-zone area and volume at four measurement times in 2008 at each study site. 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in Grand 

Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing 

downstream. -, indicates no data were collected or data were not recoverable.]

 Site ID

Area

(m2

)

Volume

(m3)

February April May October February April May October

1R 901 960 961 999 817 845 842 843

3L 161 170 165 163 103 107 108 109

8L 781 841 - 802 420 432 - 395

9L 430 1,267 1,121 807 183 798 669 508

16L 88 170 - 153 32 42 - 60

22R 724 848 845 821 900 1,241 1,203 1,205

24L 117 152 - 149 17 26 - 24

29L 416 691 - 538 369 472 - 381

30R 598 1,131 1,095 808 641 1,077 1,041 794

32R 725 773 - 745 656 623 - 598

33L 3,291 3,364 - 3,299 9,876 9,964 - 9,791

35L 838 918 - 895 1,047 1,085 - 1,079

41R 3,886 6,083 - 5,833 3,600 4,964 - 5,515

43L 2,520 2,583 2,567 2,645 2,818 2,882 2,865 2,984

44L 3,192 4,239 4,239 3,914 3,775 4,721 4,721 4,460

45L 1,937 3,455 3,455 2,878 2,871 3,778 3,778 3,593

47R 1,022 2,130 2,010 1,623 707 1,222 1,220 1,090

49R 909 2,279 1,955 1,524 926 2,037 1,942 1,656

49L 1,394 1,674 1,660 1,656 1,343 1,863 1,835 1,875

50R 1,935 2,066 2,066 1,979 3,285 3,270 3,270 3,346

51L 6,002 6,194 6,182 6,189 5,585 6,070 6,038 6,056

54R 760 1,328 - 1,270 424 655 - 781

55R 6,004 6,659 6,608 6,558 3,879 4,424 4,555 4,276

56R 1,565 2,148 2,073 2,068 1,175 1,240 1,247 1,288

58L 3,141 3,608 3,621 3,635 4,198 5,007 4,945 5,049

62R 350 382 - 397 203 315 - 299

63L 256 714 714 736 121 295 295 316

65R 797 4,085 4,085 1,263 625 2,897 2,897 714

65L 324 1,589 1,630 1,651 105 717 899 735

66L 114 3,174 2,468 682 33 488 313 58

68R 2,347 3,294 2,912 2,856 1,276 1,733 1,776 1,834

70R 746 1,502 - 1,126 519 1,502 - 951

81L 1,103 1,558 1,491 1,445 867 1,341 1,239 1,162

84R 252 301 - 286 363 448 - 432

87L 344 369 - 362 309 390 - 376

88R 212 365 - 302 138 266 - 218
Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble and Grand Canyons 47

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in Grand 

Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing 

downstream. -, indicates no data were collected or data were not recoverable.]

Area 

(m2

) 

Volume 

(m3) Site ID 

February April May October February April May October 

Table B1. High-elevation-zone area and volume at four measurement times in 2008 at each study site.—Continued 

91R 550 589 - 583 1,006 1,057 - 1,048

93L 1,088 1,490 - 1,381 659 1,212 - 1,105

104R 246 312 - 265 232 330 - 284

119R 1,091 1,748 1,623 1,363 1,474 2,115 2,044 1,926

120R 817 1,096 1,085 1,062 867 1,401 1,399 1,381

122R 1,324 2,164 2,086 2,093 1,187 1,769 1,779 1,783

123L 1,114 1,313 1,240 1,195 2,038 2,330 2,312 2,320

137L 684 1,006 - 726 659 736 - 647

139R 432 477 - 476 274 382 - 378

145L 448 692 650 575 533 709 656 584

165R 280 1,165 1,123 1,081 100 700 684 677

166L 2,386 2,938 2,820 2,513 2,792 3,235 3,201 3,368

172L 1,593 2,825 2,763 2,759 1,364 2,388 2,322 2,266

183L 1,210 1,413 1,313 1,278 2,380 2,690 2,646 2,620

194R 5,633 6,140 6,157 6,029 5,755 7,165 7,170 7,008

201R 208 2,134 1,838 987 70 1,149 1,116 799

202R 1,007 1,508 1,308 1,205 673 1,116 1,115 1,064

213L 665 1,212 1,071 968 638 1,476 1,436 1,330

214R 232 198 196 187 161 144 143 134

220R 1,338 1,408 - 1,346 1,100 1,332 - 1,287 225R 1,443 1,891 - 1,819 1,076 1,608 - 1,585
48 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Table B2. Midelevation zone area and volume at four measurement times in 2008 at each study site.

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in Grand 

Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing 

downstream. -, indicates no data were collected or data were not recoverable.]

 Site ID

Area

(m2

)

Volume

(m3)

February April May October February April May October

1R 7,361 12,164 11,744 10,468 7,507 7,752 9,608 8,576

3L 2,297 754 588 598 2,143 978 838 765

8L 1,361 1,515 - 1,377 2,278 2,883 - 2,594

9L 3,417 2,383 2,429 2,045 4,841 6,838 6,150 4,537

16L 1,351 970 - 1,088 1,099 1,546 - 1,410

22R 1,962 1,701 1,677 1,283 5,148 5,698 5,321 4,831

24L 2,007 2,048 - 2,197 3,266 3,862 - 3,877

29L 1,208 1,774 - 1,758 2,529 4,970 - 4,296

30R 1,750 2,116 2,470 2,007 3,448 6,638 6,312 4,732

32R 2,748 2,471 - 2,317 3,014 3,504 - 3,198

33L 656 924 - 552 9,360 9,811 - 9,265

35L 1,450 1,220 - 1,047 7,922 9,096 - 7,930

41R 12,118 10,040 - 8,586 20,326 26,560 - 23,536

43L 1,401 1,206 1,218 1,175 7,910 7,966 7,989 7,989

44L 6,225 5,970 - 6,562 12,068 14,522 - 12,820

45L 2,214 3,316 2,483 2,842 5,888 11,778 10,002 8,760

47R 2,581 3,906 3,241 3,323 4,841 8,762 7,443 5,993

49R 2,248 1,147 558 1,211 2,746 4,891 3,831 3,347

49L 2,472 1,053 1,006 1,817 3,797 3,781 3,687 3,903

50R 2,141 1,711 2,026 1,446 6,439 6,532 6,386 5,894

51L 6,237 2,173 1,968 2,462 18,483 16,097 15,975 16,096

54R 3,312 1,323 - 3,109 3,821 3,770 - 4,826

55R 8,269 4,374 4,497 5,476 14,877 14,385 14,251 14,455

56R 2,507 1,433 1,700 2,095 3,582 4,830 4,700 4,765

58L 2,401 2,179 3,015 2,394 8,817 10,409 10,619 10,021

62R 716 687 - 692 1,407 1,428 - 1,443

63L 4,978 5,856 4,290 4,697 5,215 10,000 8,105 7,102

65R 6,705 4,271 3,160 3,759 4,525 12,425 8,365 4,239

65L 5,901 2,335 2,745 3,363 5,346 4,636 4,800 5,242

66L 5,134 4,389 4,067 4,121 1,873 7,990 6,637 3,927

68R 2,280 2,657 1,702 1,657 5,135 7,069 5,672 5,433

70R 607 1,602 - 1,764 1,955 1,602 - 2,953

81L 951 550 609 650 3,564 4,054 3,935 3,835

84R 830 636 - 743 1,462 1,390 - 1,340

87L 493 333 - 366 1,605 1,390 - 1,450

88R 1,455 1,174 - 1,252 1,660 1,841 - 1,689

91R 872 511 - 407 2,261 1,920 - 1,818

93L 1,221 624 - 601 3,220 3,197 - 2,943

104R 201 236 - 277 844 1,028 - 893

119R 2,280 1,762 1,588 1,447 4,989 7,200 6,245 5,235

120R 2,086 1,219 1,341 1,306 4,038 4,175 4,063 3,770

122R 2,739 1,804 2,614 2,246 6,492 7,899 8,054 7,613
Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble and Grand Canyons 49

123L 1,755 664 713 1,256 4,343 3,646 3,403 3,850

137L 2,845 2,045 - 2,742 4,710 5,671 - 5,156

139R 1,506 839 - 1,136 2,884 2,327 - 2,665

145L 492 265 - 358 1,916 2,268 - 2,029

165R 3,695 1,510 1,576 2,669 7,318 7,018 6,920 7,728

166L 1,877 1,296 1,429 1,715 6,612 7,021 6,787 6,556

172L 2,643 1,457 1,767 1,559 6,492 7,756 7,662 7,330

183L 1,333 718 860 1,647 4,206 4,391 4,036 4,390

194R 2,865 2,408 2,305 2,661 15,081 15,967 15,706 15,631

201R 3,315 2,888 2,846 3,300 2,677 9,258 6,612 4,000

202R 1,687 882 961 1,024 3,965 4,330 3,718 3,439

213L 1,356 1,029 674 835 5,005 6,237 5,227 4,772

214R 1,757 505 1,413 2,548 1,781 696 1,112 1,777

220R 423 428 - 453 2,796 2,820 - 2,791

225R 1,123 649 - 878 4,516 4,742 - 4,608

Table B2. Midelevation zone area and volume at four measurement times in 2008 at each study site.—Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 0) in Grand 

Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the river, respectively, facing 

downstream. -, indicates no data were collected or data were not recoverable.]

 Site ID

Area

(m2

)

Volume

(m3)

February April May October February April May October
50 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Table B3. Low-elevation-zone eddy area and volume, and main-channel volume at four measurement 

times in 2008 at each study site.

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry 

(river mile 0) in Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left 

and right sides of the river, respectively, facing downstream. -, indicates no data were collected or data were not recoverable.]

Low-elevation eddy zone Main-channel

Site ID

Area

(m2

)

Volume

(m3)

Volume

(m3)

February April February April February April

1R - 27,750 - 48,246 - -

3L 5,148 6,683 25,818 12,665 67,587 26,320 

8L - - - - - -

9L - 8,618 - 3,158 - -

16L 6,715 7,013 16,209 9,842 12,172 8,907 

22R 4,462 4,599 17,590 16,389 5,245 4,854 

24L - - - - - -

29L - - - - - -

30R 6,175 5,276 10,890 12,359 7,893 8,390 

32R 8,152 8,381 26,762 12,398 13,216 7,014 

33L - - - - - -

35L 19,088 19,233 33,324 39,397 35,196 47,696 

41R 26,046 25,913 27,687 24,685 7,443 7,714 

43L 4,538 4,670 8,141 7,199 58,758 56,612 

44L 17,147 16,351 53,466 34,263 24,379 28,442 

45L 18,399 15,779 16,762 17,886 4,564 7,170 

47R 24,835 22,402 23,350 51,026 25,630 31,591 

49R 4,483 4,215 22,398 19,793 - -

49L 10,604 11,743 52,857 35,025 41,368 49,553 

50R - - - - - -

51L 19,463 23,335 46,263 40,975 38,652 38,648 

54R 8,295 9,715 15,197 9,874 22,450 27,946 

55R 10,072 13,314 60,244 35,847 63,334 54,769 

56R - - - - - -

58L - - - - - -

62R 14,758 14,869 30,241 35,184 15,413 10,691 

63L 22,610 21,294 62,432 81,323 22,941 31,147 

65R 9,654 8,779 46,807 41,986 43,702 26,494 

65L 6,069 8,371 26,564 20,761 9,367 9,350 

66L - - - - - -

68R 10,500 9,176 22,300 29,374 21,605 29,095 

70R - - - - - -

81L - - - - - -

84R - - - - - -

87L 316 451 625 367 9,209 12,300 

88R 1401 1511 1430 966 31,008 23,296

91R - - - - - -

93L 1,285 1,479 4,303 3,838 9,339 12,265

104R 575 474 290 586 1,368 1,649

119R 5,558 5,419 11,788 9,929 6,805 6,315

120R - - - - - -
Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble and Grand Canyons 51

122R 4,178 4,273 7,521 8,222 4,798 5,363 

123L 5,179 6,072 13,080 5,306 17,662 10,801 

137L 1,609 2,088 1,556 1,090 1,214 1,939 

139R 5,249 5,870 12,072 7,844 6,199 8,329 

145L 380 363 435 426 2,441 2,901 

165R 1,180 2,479 10,857 8,704 4,345 4,679 

166L - - - - - -

172L 5,165 5,119 12,875 14,147 12,493 14,110 

183L - - - - - -

194R 5,638 5,590 9,880 10,980 24,944 28,775 

201R 8,533 7,035 3,432 7,890 30,702 798 

202R 12,919 13,227 21,018 25,795 8,811 10,904 

213L 1,973 1,753 2,407 3,783 7,734 7,967 

214R 3,256 4,545 4,637 2,058 11,301 12,229 

220R 688 612 580 841 - -

225 3,070 3,096 9,062 8,346 31,625 34,591 

Table B3. Low-elevation-zone eddy area and volume, and main-channel volume at four measurement 

times in 2008 at each study site.—Continued 

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry 

(river mile 0) in Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left 

and right sides of the river, respectively, facing downstream. -, indicates no data were collected or data were not recoverable.]

Low-elevation eddy zone Main-channel

Site ID

Area

(m2

)

Volume

(m3)

Volume

(m3)

February April February April February April
52 Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River

Table B4. Midelevation zone and high-elevation-zone campsite area measured at four measurement times in 2008 

at each study site.

[Site ID is river mile (RM) location based on the RM centerline (U.S. Geological Survey, 2006) downstream from Lees Ferry (river mile 

0) in Grand Canyon National Park. The descriptors “L” and “R” denote the location of the emergent sandbar on left and right sides of the 

river, respectively, facing downstream. -, indicates no data were collected or data were not recoverable. Recreational reaches as defined by 

Kearsley and Warren (1993); C, critical reach. NC, noncritical reach.]

Site Recreation 

Reach

February March October

Midelevation 

(m2

)

High-elevation

(m2)

Midelevation

(m2)

HighElevation

(m2)

Midelevation 

(m2)

High-Elevation

(m2)

8L NC 231 300 107 357 387 370

16L C 216 269 363 318 299 273

22R C 255 130 148 373 102 268

24L C 163 16 699 30 637 35

29L C 102 96 637 288 578 210

30R C 71 189 397 552 52 267

32R C 0 372 0 418 0 347

35L C 0 481 79 430 30 490

41R NC 104 229 96 341 36 145

43L NC 0 184 3 392 0 251

44L NC 257 576 249 762 175 571

45L NC 0 263 1,148 1,140 64 766

47R NC 717 384 1,837 1,092 232 330

50R NC 124 593 0 611 45 560

51L NC 0 110 0 161 0 98

55R NC 0 0 0 20 0 0

62R NC 0 31 0 135 40 132

81L C 77 391 60 1,170 0 853

84R C 109 82 97 98 65 64

87L C 0 0 0 302 9 206

91R C 256 218 0 214 2 197

93L C 88 45 8 325 4 231

104R C 0 70 6 107 0 76

119R NC 36 137 391 339 132 125

122R NC 208 98 299 657 92 719

123L NC 187 174 0 150 189 89

137L C 380 183 633 581 670 286

139R C 21 77 0 59 81 63

145L C 9 103 0 394 7 317

166L NC 70 88 43 128 169 42

172l NC 0 0 214 176 0 0

183L NC 0 0 17 37 0 6

183R NC 107 21 97 330 4 145

194R NC 85 493 0 581 270 317

202R NC 498 146 158 598 85 273

213L NC 238 76 106 444 11 323

220R NC 0 461 0 347 0 302

sum 4,609 7,086 7,892 14,457 4,467 9,747

median 85 137 79 341 45 251

s.d. 157 171 375 293 181 213
Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble and Grand Canyons 53

Produced in the Western Region, Menlo Park, California

 Manuscript approved for publication January 28, 2010

 Text edited by Peter Stauffer

 Layout and design by Judy Weathers
Appendix B. Basic Data Tables for Studied Sites on Colorado River, Marble and Grand Canyons 55

Hazel and others—Sandbar Response in Marble and Grand Canyons, Arizona, Following the 2008 High-Flow Experiment on the Colorado River—Scientific Investigations Report 2010–5015