Sandbars and Sand Storage in Marble 

and Grand Canyons

Paul Grams (pgrams@usgs.gov): U.S. Geological Survey, Grand Canyon 

Monitoring and Research Center, Flagstaff, Arizona

With contributions from: Dan Buscombe, Tom Gushue, Erich Mueller, Rob Ross, Jack 

Schmidt, David Topping, Bob Tusso: U.S. Geological Survey, Grand Canyon Monitoring 

and Research Center, Flagstaff, Arizona

AND

Dan Hadley, Dan Hamill, Joe Hazel, Matt Kaplinski, and Rob Weber: Northern Arizona 

University, School of Earth Sciences and Environmental Sustainability, Flagstaff, Arizona

Grand Canyon Monitoring and Research Center

Annual Project Reporting Meeting

Phoenix, Arizona

January 29, 2014
Overview

• Sandbar response to sediment-rich high flows

• Changes in campsites relative to changes in sandbars 

and vegetation

• Expanding the sample size: sandbar area in Marble 

Canyon, 2002-2009

• Expanding the temporal scale: sandbars in 1984

• Channel Mapping: implications for sand storage and 

sandbar monitoring
Sandbar response to sediment-rich high flows

• November 2012 HFE

– Images from remote cameras: 

• 52% (17 out of 33): noticeable gain

• 39% (13 out of 33): no substantial change

• 9% (3 out of 33): noticeable loss

– Sandbar surveys: 54% of sites (27 out of 50) larger in Oct. 2013 than in 

Oct. 2011

• November 2013 HFE

– Images from remote cameras:

• 53% (21 out of 40): noticeable gain

• 30% (12 out of 40): no substantial change

• 18% (7 out of 40): noticeable loss

Bob Tusso, unpublished data, do not cite
Sandbars 10 months following 2012 high flow

Grand Canyon (RM 88-225)

10 of 16 sites larger than Oct. 2011

11 of 16 sites larger than Oct. 2008

Eastern Grand Canyon (RM 62-87)

1 of 3 sites larger than Oct. 2011

1 of 3 sites larger than Oct. 2008

Lower Marble Canyon (RM 30-62)

11 of 16 sites larger than Oct. 2011

9 of 16 sites larger than Oct. 2008

Upper Marble Canyon (RM 0-29)

5 of 7 sites larger than Oct. 2011

3 of 7 sites larger than Oct. 2008

2012 HFE

Joe Hazel, unpublished data, do not cite
Sandbars 10 months following 2012 high flow

Grand Canyon (RM 88-225)

10 of 16 sites larger than Oct. 2011

11 of 16 sites larger than Oct. 2008

Eastern Grand Canyon (RM 62-87)

1 of 3 sites larger than Oct. 2011

1 of 3 sites larger than Oct. 2008

Lower Marble Canyon (RM 30-62)

11 of 16 sites larger than Oct. 2011

9 of 16 sites larger than Oct. 2008

Upper Marble Canyon (RM 0-29)

5 of 7 sites larger than Oct. 2011

3 of 7 sites larger than Oct. 2008

2012 HFE

Joe Hazel, unpublished data, do not cite
Sandbars 10 months following 2012 high flow

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2000 2004

2004 HFE 2008 HFE

2010

2012 HFE

2002 2006 2008 2012

Marble Canyon, n=23

Grand Canyon, n=22

• Sediment enriched HFEs and relatively low release volumes 

•  relatively large bars 10 months following HFE

Joe Hazel, unpublished data, do not cite
10 of 16 sites larger in 2013 than 

2011

8 of 16 sites larger in 2013 than 

2008 post-HFE

1 of 3 sites larger in 2013 than 2011

2 of 3 sites larger in 2013 than 2008 

post-HFE

11 of 16 sites larger in 2013 than 

2011

4 of 16 sites larger in 2013 than 

2008 post-HFE

5 of 7 sites larger in 2013 than 2011

1 of 7 sites larger in 2013 than 2008 

post-HFE

Sand Budget trending positive

Sand Budget trending negative

Sand Budget trending neutral

Upper Marble 

Canyon 

(RM 0-29)

Lower Marble 

Canyon 

(RM 30-62)

Eastern Grand 

Canyon 

(RM 62-87)

Grand Canyon 

(RM 88-225)

Sand Budget trending positive

Segment Sand Budget Sandbar Condition

Sandbars and Sand Budget: 2011 – 2013

Joe Hazel, unpublished data, do not cite
Change in Vegetation Within 504 Campsite Boundaries 

throughout Grand Canyon based on the 2002 and 2009 

Remote Sensing

• ~13% increase in vegetation cover within campsite boundaries, 2002-2009

Vegetation in both years

Vegetation gain

Vegetation loss

Dan Hadley, unpublished data, do not cite
Factors Contributing to Loss of Usable Camp Area at 

Long-term Monitoring Sites, 2002-2009

~4 to 20% of 

losses in usable 

camp area 

associated with 

increases in 

vegetation

~10 to 80% of 

losses in usable 

camp area 

associated with 

sandbar erosion

Non-critical

Reach 1

(RM 0-11)

Critical

Reach 1

(RM 11-41)

Non-critical

Reach 2

(RM 41-77)

Critical

Reach 2

(RM 77-116)

Non-critical

Reach 3

(RM 116-131)

Critical

Reach 3

(RM 0-131-164)

Non-critical

Reach 4

(RM 164-225)

Dan Hadley, unpublished data, do not cite
Sandbar Area throughout 

Marble Canyon based on 2002-

2009 Remote Sensing

• 7 study reaches with detailed mapping 

from air photos for 1935 to 1996 (Jack 

Schmidt and students at USU)

• Covers ~50% of the reach between Lees 

Ferry and RM 72

• Updated with sandbar extents depicted 

on 2002, 2005 and 2009 overflights

REACH 0-8 29-35 42-47 48-50 60-72

Pre-dam

1965-96

1996-09

Rob Ross, unpublished data, do not cite
• No significant change in exposed 

sandbar area in period of stable (or 

slight positive) trend in sand budget

Sandbar Area throughout 

Marble Canyon based on 2002-

2009 Remote Sensing

Rob Ross, unpublished data, do not cite
1984 bar much 

larger than present

Indicative of a site 

that requires large 

floods to build 

large bars

1984 bar slightly 

larger than 

present

HFE’s consistently 

build a bar a bit 

smaller than 

existed in 1984

1984 bar smaller 

than present

HFE’s and 

vegetation 

expansion has 

resulted in a large, 

stabilized bar

1984 2009

Joe Hazel, unpublished data, do not cite
1984 bar much 

larger than present

Indicative of a site 

that requires large 

floods to build 

large bars

1984 bar slightly 

larger than 

present

HFE’s consistently 

build a bar a bit 

smaller than 

existed in 1984

1984 bar smaller 

than present

HFE’s and 

vegetation 

expansion has 

resulted in a large, 

stabilized bar

1984 2009

• Sandbars not universally “large” 

in 1984

• Provides context when looking 

at bar size following HFEs

• Contributes to emerging 

understanding of sandbar 

behavior

Joe Hazel, unpublished data, do not cite
Monitoring Sand Storage in Grand Canyon

• Track sand storage to:

– Plan floods

– Evaluate “progress”

– Make predictions 

about long-term 

prognosis

• The scientific 

Challenges:

– Where is the sand?

– What controls sand 

storage changes at 

“local” and “reach” 

scales?
Colorado River Channel Mapping: 

2009 – 2012

• Lower Marble Canyon (RM 29.4 to 

61.7).

• Measurements of sand flux indicate 

~0 to ~300,000 metric tons of sand 

accumulation

• What actually happened on the 

river bed and to sand bars???
• Make digital elevation 

models like this for 

each survey 

• Compute changes by 

differencing the two 

maps:

View is looking upstream

Black dots are 0.1 mi intervals

Repeat Measurements of Channel 

Topography with multibeam Sonar
Geomorphic Base Map

• A map to:

– Include all Colorado River 

alluvial deposits

– Identify depositional setting

• Eddy/non-eddy

• Separation/reattachment zone

– Identify channel units (e.g. 

rapid/gravel riffle/pool)

• Map covers ALL of RM 29 to 

61 (including reaches with 

we did not survey)

Map Unit

Number in 

Study Reach

Number 

Surveyed

Percent Surveyed 

(by area)

Channel segments 229 206 84%

Eddies 222 199 89%

Eddy sand bars 204 183 87%

Channel margin sand bars 60 54 76%

Gravel bars 23 8 16%

Debris fans 142 121 55%

Surveyed 87% of sand bars

(long-term monitoring sites 

are 14% of the bars in same 

reach)

Paul Grams, unpublished data, do not cite
• Deposition in eddy at 

35.07 (Nautiloid): 2nd

ranked eddy change

+15,000 m3

Paul Grams, unpublished data, do not cite
May 2009

Paul Grams, unpublished data, do not cite
May 2012

Paul Grams, unpublished data, do not cite
• Channel at RM 43.55: 

largest single change 

in 30-mi reach

• Eddy at RM 43.55: 3rd

rank change in entire 

reach; largest change 

in eddy for entire 

reach

-41,500 m3

-26,700 m3

Paul Grams, unpublished data, do not cite
May 2009

Paul Grams, unpublished data, do not cite
May 2012

Paul Grams, unpublished data, do not cite
38% of gross storage change in eddies

55% of gross storage change in channel

7% of gross storage change in bars

Paul Grams, unpublished data, do not cite
7% of gross storage change in bars

38% of gross storage change in eddies

55% of gross storage change in channel

> 0.5 mm

~0.45 mm

< 0.4mm

Paul Grams, unpublished data, do not cite
Average Sandbar Change

• Bars net erosional for May 

2009 to May 2012 period

• Mean erosion of about 30 cm

124 Bars in 30-mi reach

18 with > 10 cm deposition

65 with > 10 cm erosion

41 with < 10 cm change

Paul Grams, unpublished data, do not cite
Comparison with Long-term Sandbar 

Monitoring (NAU) Sites

• Both sets show net erosion

• Less variability and less erosion at NAU sites

• However, the data for the NAU sites only show changes above the 

8,000 cfs stage, while the channel mapping data includes erosion 

below that elevation

Paul Grams, unpublished data, do not cite
Comparison with Long-term Sandbar Monitoring (NAU) 

Sites – Only for changes above 8,000 ft3/s stage elevation

Mean 

Change

Maximum 

Deposition

Maximum 

Erosion

Standard 

Deviation

Monitoring Sites -0.06 m 0.54 m -0.54 m 0.23 m

All Bars above 8,000 ft3/s elevation -0.06 m 1.01 m -1.12 m 0.35 m

Paul Grams, unpublished data, do not cite
Sandbars and the sand mass balance on 

the Colorado River in Grand Canyon

Sand accumulates on 

the bed and in eddies 

during low flows
Floods build sandbars 

and export sand 

downstream

Sandbars and the sand mass balance on 

the Colorado River in Grand Canyon
Following floods, sandbars 

erode, and the cycle can 

repeat...

... as long as there is 

enough sand. 

Sandbars and the sand mass balance on 

the Colorado River in Grand Canyon
Summary

• High flows

– Recent sediment-rich high flows (Nov. 2012 & Nov. 2013) have built sandbars on par with 

other high flows

• Campsites

– Vegetation is an important cause of usable camp area change at some sites

– Erosion causes a larger proportion of change at many sites

• Sandbar area in Marble Canyon from Air Photos

– Sandbar area remains substantially lower than predam period

– Sandbar area is larger in recent period than the pre-1996 period

– Sandbar area has been approximately stable between 2002 and 2009

• Sandbars in 1984

– Analyzed at 6 sites

– Some sites show larger bar in 1984, some similar or smaller than present

– Will be valuable in improving understanding of different behavior of different sites in response 

to floods

• Channel Mapping: implications for sand storage and sandbar monitoring

– Bars, eddies, and channel do not have same trend for period

• Bars (negative storage change)

• Eddies (slightly positive storage change)

• Channel (negative storage change)

• Change in bars measured by channel mapping (84 exposed bars) agrees 

with change measured by long-term sandbar monitoring (18 bars) for 

same reach

• BUT: Those changes are less than 7% of the changes in the reach

Paul Grams, unpublished data, do not cite
Summary

• Periods with relatively low releases, ample Paria

river sand inputs, and sediment-rich high flows 

(most of 2002-2013):

• may have approximately stable sand budgets 

• and sandbars may be stable (air photo analysis of many bars), or 

increase in size (long-term monitoring of relatively few sites)

• Periods with above average releases (e.g. 2011 

equalization flows)

• cause net scour from the channel and a decrease in sandbar size

Paul Grams, unpublished data, do not cite