U.S. Department of the Interior 

U.S. Geological Survey 

Project B Update and 

Riverbed and sandbar response to dam operations and high-flow experiments 

Glen Canyon Dam Adaptive Management Program 

Annual Reporting Meeting 

January 24, 2024 

Paul Grams 

U.S. Geological Survey 

Southwest Biological Science Center 

Grand Canyon Monitoring and Research Center 

*This information is preliminary and is subject to revision. It is being 

provided to meet the need for timely best science. The information is 

provided on the condition that neither the U.S. Geological Survey nor 

the U.S. Government shall be held liable for any damages resulting 

from the authorized or unauthorized use of the information. 
 

 

 

Acknowledgements Project B personnel: 

Paul Grams, Katie Chapman, Matt Kaplinski, Keith Kohl, 

Gerard Salter, Shannon Sartain, and Robert Tusso 

GIS and website support: 

Thomas Gushue and Erica Byerley 

Collaborators and cooperators: 

David Topping and Project A, Erich Mueller, Scott Wright, Jon Nelson, 

photo: Geoff Gourley 

photo: Jeff Behan 

photo: Geoff Gourley 

Additional collaborators and field assistants: 

GCRG, Jeff Behan, Sinjin Eberle, Jesse Collier, 

Daniel Buscombe, Robert Ross, Daniel Hamill, 

David Rubin, Joel Sankey, Jack Schmidt, Rod 

Parnell, Bryan Cooperrider, Karen Koestner, 

Emily Thompson, Daniel Hadley, Ryan 

Seumptewa, Geoff Gourley. Somer Morris. Lydia 

Manone, Lauren Tango, John O’Brien, Morgan 

Barnard, Pete Koestner, Logistics team: Seth 

Felder, Dave Foster, Clay Nelson, Lucien Bucci, 

and Ann-Marie! 
 

 

 

 

 

 

 

Project B: Sandbar and Sediment Storage Monitoring and 

Research 

• Project Elements

• B.1 Sandbar Monitoring 

• B.2 Bathymetric and topographic mapping for monitoring long-term trends in sediment storage 

• B.3 Control Network and Survey Support 

• B.5* Sediment and Sandbar Modeling 

• FY 2023 involvement in other projects: 

• O.2 (sediment dynamics in Western Grand Canyon) 

• L (overflight remote sensing) 

• Project Objectives

• Track the effects of individual High Flow Experiments (HFEs) on sandbars. 

• Monitor the cumulative effect of successive HFEs and intervening operations on sandbars and sand 

conservation. 

• Investigate and model interactions between dam operations, sand transport, and eddy sandbar 

dynamics. 

• Cooperators: Grand Canyon River Guides, Southern Utah University, Northern Arizona University 

* Funded with carryover and non-AMP supplemental sources. 
 

 

 

 

 

 

 

 

 

 

Project B: AMP goals addressed, and information provided 

• LTEMP goal: 

– “Increase and retain fine sediment volume, area, and distribution in the Glen, Marble, and Grand 

Canyon reaches above the elevation of the average base flow for ecological, cultural, and 

recreational purposes.” 

• Question from HFE Protocol: 

– “Can sandbar building during HFEs exceed sandbar erosion during periods between HFEs, such 

that sandbar size can be increased and maintained over several years?” 

• Project B address these questions by two monitoring efforts and modeling: 

– Annual sandbar and campsite monitoring (sandbar surveys and daily photographs) 

• Annual assessment of the effects of HFEs and other dam operations on selected sandbars and campsites. 

• Assessment of immediate response to HFEs by network of remote time-lapse cameras 

– Periodic channel mapping (Combined topographic and bathymetric mapping) 

• Evaluation of LTEMP performance by measuring long-term trends in sand area, volume, and distribution from a large 

sample of sandbars. 

• Measurement of long-term trends in sand storage on the riverbed. 

– Modeling to predict fine sediment transport and sandbar response 
 

 

 

 

April 2023 HFE 

Reservoir conditions 

• All previous HFEs implemented when Powell was 

at ~3550 feet or higher 

• April 2023 HFE implemented at ~3525 feet, but 

ahead of anticipated rise of > 50 feet 

Sediment conditions 

• More than 1.5 million Mg sand accumulation in 

Marble Canyon between 7/1/2022 and HFE. 

• HFE exported from Marble Canyon ~ 1 million 

MG of sand. 

• Summer 2023 operations exported additional 

~700,000 Mg of sand. 

www.gcmrc.gov/discharge_qw_sediment 
 

 

 

“cost of business” 

Builds high-elevation sandbars 

“lost sand” 

Erosion of bars deposited by HFE 

Can increase low-elevation bars 

 

 

April 2023 HFE 

Reservoir conditions 

• All previous HFEs implemented when Powell was 

at ~3550 feet or higher 

• April 2023 HFE implemented at ~3525 feet, but 

ahead of anticipated rise of > 50 feet 

Sediment conditions 

• More than 1.5 million Mg sand accumulation in 

Marble Canyon between 7/1/2022 and HFE. 

• HFE exported from Marble Canyon ~ 1 million 

MG of sand. 

• Summer 2023 operations exported additional 

~700,000 Mg of sand. 

www.gcmrc.gov/discharge_qw_sediment 
 

Sandbar monitoring data 

Hazel and others (2022); www.usgs.gov/apps/sandbar 

Data collection: total station and 

survey rod 

Allows data collection 

down to 8,000 cfs stage 

and in dense vegetation. 

Neither of which can be 

done reliably with modern 

methods (lidar etc.) 

data processing and analysis 

Topographic 

surfaces modeled in 

survey software 

Data processed 

and analyzed in 

sql database 

Data served in 

sandbar web 

application 
 

 

 

Sandbar monitoring study sites 

20 sites in Marble 

Canyon 

24 sites in Grand Canyon 

1 site in 

Glen 

Canyon 

Monitoring Data 

• 45 sites currently monitored 

• 32 monitored since 1990 

• Data collected annually in October 

• 42 of the sites instrumented with 

remote cameras 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

 

Sandbar response to 2023 HFE 

2023 HFE 

• Reattachment bars and upper pool bars as large or larger 

compared to 2013-2019 

• Separation and undifferentiated bars increased, but not 

as large as some previous years 

• HFE reversed 2019 to 2022 downward 

trend 

• Increases in bar volume at most, but not 

all, sites 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

 

 

Campsite response to 2023 HFE 

• Increases in campsite area in critical and noncritical camping reaches 

• Loss in campsite area only in non-critical reach 

below 15,000 cfs stage 

* Critical reaches are those reaches where campsites are 

fewer than average and finding a campsite can be 

competitive. 

Hazel and others (2022) and preliminary data, do not cite 
 

 

 

 

 

 

 

Why measure sand storage by 

mapping the riverbed? 

• Sandbar replenishment controlled by: 

– Flow (need high flows to build large bars) 

– Sand supply (if supply in the channel is low, a 

net loss from eddy sandbars is risked) 

• Sand supply is controlled by: 

– Dam releases (annual volume and release 

pattern) 

– Inputs from tributaries 

• The sand that builds sandbars is stored on the 

bed of the river and understanding the sand 

supply is critical to understanding and 

predicting sandbar response Adapted from Hazel and others (2010) 
 

 

 

 

 

 

Sand Budgets in Grand Canyon have been incorrect or ambiguous because of 

inadequate measurements or because of measurement uncertainty 

1990’s 

Stable rating curves  sand accumulation 

(Glen Canyon Dam Environmental Impact Statement, 1994) 

2000’s 

Analysis of historical and uncertainty is large 

data  no 

accumulation 

(Topping et al., 2000) 

2010’s 

Continuous measurements of flux 

either accumulation or evacuation may occur, 
How are channel mapping data used to evaluate the 

effects of dam operations? 

 

 

 

 

“high-elevation sandbar” 

loss gain 

Mining 

sand from 

storage to 

build 

sandbars 

Accumulating 

sand and 

building 

sandbars 

Mining Accumulating 

sand and sand, but not 

losing building 

sandbars sandbars. 

loss gain 

“total sand storage in 

channel and eddies” 
 

 

 

 

 

How are channel mapping data used to evaluate the 

effects of dam operations? 

 

 

 

 

“high-elevation sandbar” 

loss gain 

Mining 

sand from 

storage to 

build 

sandbars 

Mining 

sand and 

losing 

sandbars 

Accumulating 

sand and 

building 

sandbars 

Accumulating 

sand, but not 

building 

sandbars. 

loss gain 

• The 2004 and 2008 HFEs demonstrated sandbar building 

“total sand storage in under conditions of greater sand enrichment  less 

channel and eddies” erosion of sand from storage in eddies and channel 

1996 2008

More sites with net eddy 

erosion 

More sites with net eddy 

deposition 
 

How we measure sand storage on the bed 

• Repeat topographic and 

bathymetric measurements 

– Multibeam sonar 

– Singlebeam sonar 

– Total station 

• Referenced to geodetic control 

network 

• Use backscatter to classify 

sand/gravel/rock 

• High spatial resolution 

• Uncertainty accumulates 

spatially – not over time 

- = 

May 2016 May 2013 Difference 

Blue = deposition 

Red = erosion 
 

 

 

 

 

Repeat channel mapping in Lower Marble Canyon 

• Repeat measurements of channel bed (red points) verify mass balance sand budget 

(black line with gray uncertainty band) 

• Sand budget has trended upward with the exception of periods of high dam release 

volumes (equalization and reservoir balancing flows) 

www.gcmrc.gov/discharge_qw_sediment; Grams et al., 2018; and Preliminary results. Do not cite. 
 

Repeat channel mapping in Lower Marble Canyon 

2009 to 2012 

• Period of sand erosion during equalization 

flows 

• Sand volume change above 8,000 ft3/s stage 

(blue) is ~4% of total erosion (red) 

2012 to 2019 

• Period of sand accumulation 

• Sand volume change above 8,000 ft3/s stage 

(blue) is ~6% of total accumulation (red) 

www.gcmrc.gov/discharge_qw_sediment and Preliminary results. Do not cite. 
Repeat channel mapping: Implications for 

high flows and dam management 
 

Repeat channel mapping: Implications for 

high flows and dam management 

Repeat measurements during HFEs (diamonds) 

• HFEs are “deficit spending” 

• Need to mobilize all the sand to build sandbars and a 

large fraction is exported 

• But a short-term negative that can be recovered from 

Repeat measurements over many years (circles) 

• Downward spiral: Equalization flows and no HFEs 

• Deficit spending: Equalization flows and HFEs 

• Sustainable: No equalization flows and HFEs 

Schmidt and Grams, 2011; Grams et al. 2018; and Preliminary results. Do n

The 2004 and 2008 HFEs demonstrated sandbar building under 

conditions of greater sand enrichment was most effective with less 

erosion of sand from storage in eddies and channel (Hazel and 

others, 2010; Schmidt and Grams, 2011). 

ot cite. 
Conclusions: Sandbars and in -channel sediment storage 

Sandbar response to HFEs 

• When implemented, HFEs under sand-enriched conditions cause increases in 

sandbar area and volume. 

– When HFEs are not implemented, sandbars and campsites decline. 

• From 2019 through 2022, sandbar volume decreased for most bar types because 

monsoon failure (2019, 2020) and low reservoir levels (2021, 2022) prevented HFE 

implementation for 4 consecutive years. 

• Sandbar building accomplished by April 2023 HFE comparable to previous 

November HFEs for most bar types. 

• Deposition at sandbars is likely stage-limited (bars not likely to get larger without 

larger HFEs). 

Changes in sand storage 

• Lower Marble Canyon has alternately gained and lost sand as function of dam 

operations and tributary sediment supply. 

• Because changes in sandbars above 8,000 ft3/s stage comprise less than 10% of 

total changes in sand storage, the evaluation of sediment response to dam 

operations requires measurements of total sediment storage change. 

• Measurements indicate “sustainable” sand management has only occurred during 

periods that include both HFEs and “normal” reservoir operations (no equalization 

flows). 
Project B: Publications (2021-2023) 

• Alvarez, L. V., & Grams, P. E. (2021). An eddy-resolving numerical model to study 

turbulent flow, sediment, and bed evolution using Detached Eddy Simulation in a 

lateral separation zone at the field-scale. Journal of Geophysical Research: Earth 

Surface, 126,e2021JF006149. https://doi.org/10.1029/2021JF006149 

• Durning, L.E., Sankey, J.B., Yackulic, C.B., Grams, P.E., Butterfield, B.J. and Sankey, 

T.T. 2021. Hydrologic and geomorphic effects on riparian plant species occurrence 

and encroachment: remote sensing of 360 km of the Colorado River in Grand Canyon. 

Ecohydrology (e2344). https://doi.org/10.1002/eco.2344. 

• Grams, P.E., Hazel, J.E., Jr., Kaplinski, M., Ross, R.P., Hamill, D., Hensleigh, J., and 

Gushue, T., 2020, Long-term sandbar monitoring data along the Colorado River in 

Marble and Grand Canyons, Arizona: U.S. Geological Survey data release, 

https://doi.org/10.5066/P93F8JJK. 

• Grams, P.E., Alvarez, L., Kaplinski, M., and Wright, S., 2021, Repeat measurements 

of bathymetry, streamflow velocity and sediment concentration made during a high 

flow experiment on the Colorado River in Grand Canyon, March 2008: U.S. Geological 

Survey data release, https://doi.org/10.5066/P9O00Z44. 

• Hazel, J. E., Jr., Kaplinski, M. A., Hamill, D., Buscombe, D., Mueller, E. R., Ross, R. 

P., Kohl, K., & Grams, P. E. (2022). Multi-Decadal Sandbar Response to Flow 

Management Downstream from a Large Dam-The Glen Canyon Dam on the Colorado 

River in Marble and Grand Canyons, Arizona. U.S. Geological Survey Professional 

Paper 1873, 104 p, https://doi.org/10.3133/pp1873. 

• Kaplinski, M., Hazel, J. E. J., Grams, P. E., Gushue, T., Buscombe, D. D., & Kohl, K. 

(2022). Channel mapping of the Colorado River from Glen Canyon Dam to Lees Ferry 

in Glen Canyon National Recreation Area, Arizona. U.S. Geological Survey Open-File 

Report 2022-1057. https://doi.org/10.3133/ofr20221057. 

• Kaplinski, M., Hazel, J.E. Jr, Grams, P.E., Gushue, T., Buscombe, D.D., and Kohl, K., 

2022, Channel mapping Glen Canyon Dam to Lees Ferry in Glen Canyon National 

Recreation Area, Arizona - Data: U.S. Geological Survey data release, 

https://doi.org/10.5066/P98GFP93. 

• Le Coz, J., Perret, E., Camenen, B., Topping, D.J., Buscombe, D.D., Leary, K.C.P., 

Dramais, G., and Grams, P.E., 2022, Mapping 2-D bedload rates throughout a sandbed river reach from high-resolution acoustical surveys of migrating bedforms: Water 

Resources Research, v. 58, no. 11, e2022WR032434, p. 1-16,

https://doi.org/10.1029/2022WR032434. 

• Mueller, E.R., and Grams, P.E., 2021, A Morphodynamic Model to Evaluate 

Long-Term Sandbar Rebuilding Using Controlled Floods in the Grand Canyon:

Geophysical Research Letters, v. 48, p. 1–10, doi:10.1029/2021GL093007. 

• Sabol, T.A., Griffiths, R.E., Topping, D.J., Mueller, E.R., Tusso, R.B., and Hazel,

J.E., Jr., 2021, Strandlines from large floods on the Colorado River in Grand 

Canyon National Park, Arizona: U.S. Geological Survey Scientific Investigations 

Report 2021-5048, 41 p., https://doi.org/10.3133/sir20215048. 

• Sabol, T.A., Griffiths, R.E., Topping, D.J., Mueller, E.R., Tusso, R.B., and Hazel,

Jr., J.E., 2021, Surveyed peak-stage elevations, coordinates, and indicator data 

of strandlines from large floods on the Colorado River in Grand Canyon National 

Park, Arizona: U.S. Geological Survey data release,

https://doi.org/10.5066/P9GIQ9ZN 

• Unema, J.A., Topping, D.J., Kohl, K.A., Pillow, M.J., and Caster, J.J., 2021, 

Historical floods and geomorphic change in the lower Little Colorado River 

during the late 19th to early 21st centuries: U.S. Geological Survey Scientific 

Investigations Report 2021–5049, 34 p., https://doi.org/10.3133/sir20215049. 

Web applications 

• Images from remote camera monitoring of sandbars:

https://grandcanyon.usgs.gov/gisapps/sandbarphotoview

er/RemoteCameraTimeSeries.html 

• Images from GCRG adopt-a-beach program:

https://grandcanyon.usgs.gov/gisapps/adopt-abeach/index.html 

• Data from long-term sandbar monitoring sites:

https://www.usgs.gov/apps/sandbar/ 
Additional references 

• Grams, P. E., Topping, D. J., Schmidt, J. C., Hazel, J. E., & Kaplinski, M. (2013). Linking morphodynamic response with sediment mass balance on the 

Colorado River in Marble Canyon: Issues of scale, geomorphic setting, and sampling design. Journal of Geophysical Research, 118, 21. 

https://doi.org/doi:10.1002/jgrf.20050 

• Grams, P. E., Buscombe, D., Topping, D. J., Kaplinski, M., & Hazel, J. E. (2018). How many measurements are required to construct an accurate sand budget 

in a large river? Insights from analyses of signal and noise. Earth Surface Processes and Landforms, 44(1), 160 –178. https://doi.org/10.1002/esp.4489 

• Hazel Jr., J. E., Grams, P. E., Schmidt, J. C., & Kaplinski, M. (2010). Sandbar response following the 2008 high -flow experiment on the Colorado River in 

Marble and Grand Canyons. U.S. Geological Survey Scientific Investigations Report 2010 -5015, 52 p. http://pubs.usgs.gov/sir/2010/5015 

• Hazel, J.E., Jr., Kaplinski, M.A., Hamill, D., Buscombe, D., Mueller, E.R., Ross, R.P., Kohl, K., and Grams, P.E., 2022, Multi -decadal sandbar response to flow 

management downstream from a large dam —The Glen Canyon Dam on the Colorado River in Marble and Grand Canyons, Arizona: U.S. Geological 

Survey Professional Paper 1873, https://doi.org/10.3133/pp1873 

• Mueller, E.R., and Grams, P.E., 2021, A morphodynamic model to evaluate long -term sandbar rebuilding using controlled floods in the Grand Canyon: 

Geophysical Research Letters, v. 48, no. 9, e2021GL093007, https://doi.org/10.1029/2021GL093007. 

• Schmidt, J. C., & Grams, P. E. (2011). The high flows --physical science results. In T. S. Melis (Ed.), Effects of three high -flow experiments on the Colorado 

River ecosystem downstream from Glen Canyon Dam, Arizona, U.S. Geological Survey Circular 1366 (pp. 53 –91). https://pubs.usgs.gov/circ/1366/ 

• Topping, D. J., Rubin, D. M., & Vierra, L. E. (2000). Colorado River sediment transport 1. Natural sediment supply limitation and the influence of Glen 

Canyon Dam. Water Resources Research, 36(2), 515 –542. https://doi.org/10.1029/1999WR900285 

• Wiele, S.M., Andrews, E.D., and Griffin, E.R., 1999, The effect of sand concentration on depositional rate, magnitude, and location in the Colorado River 

below the Little Colorado River, in Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, R.A., eds., The controlled flood in Grand Canyon: Washington, D.C., 

American Geophysical Union, Geophysical Monograph Series, v. 110, p. 131 –145. 

• Wright, S.A., Topping, D.J., Rubin, D.M., and Melis, T.S., 2010, An approach for modeling sediment budgets in supply -limited rivers: Water Resources 

Research, v. 46, p. 1 –18, doi:10.1029/2009WR008600. 

• U.S. Department of the Interior, 1996, Record of Decision, Operation of Glen Canyon Dam Final Environmental Impact Statement. 

• U.S. Department of the Interior, 2016, Record of Decision for the Glen Canyon Dam Long -Term Experimental and Management Plan Final Environmental 

Impact Statement, https://ltempeis.anl.gov/ 
Supplemental figures 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Project B: Key findings with respect to LTEMP Goals and 

Knowledge Assessment 

• LTEMP goal: 

– “Increase and retain fine sediment volume, area, and distribution in the 

Glen, Marble, and Grand Canyon reaches above the elevation of the 

average base flow for ecological, cultural, and recreational purposes.” 

• Assessment: 

– Although specific targets for sandbars are not defined, each HFE has 

resulted in deposition demonstrating that the general objective of retaining 

and/or increasing sand volume above the 8,000 cfs stage can be achieved 

when sand inputs occur and HFEs are implemented (2012-2018 and 2023). 

• Prognosis: 

– Deposition at sandbars is likely stage-limited (bars not likely to get larger 

without larger HFEs) 

– Sandbar volume increased and maintained from 2011 to 2018 when dam 

releases were relatively low and sand inputs from Paria River average or 

above and HFEs were implemented. 

– From 2019 through 2022, sandbar volume decreased for most bar types 

because monsoon failure (2019, 2020) and low reservoir levels (2021, 2022) 

prevented HFE implementation for 4 consecutive years. 

– The “preemptive” HFE implemented in April 2023 rebuilt eroded sandbars 

OR 

Status: unknown, because targets not 

defined; or good, because sand volume and 

area are not currently decreasing 

Trend: unchanging because HFEs result in 

deposition, but bars are not progressively 

expanding 

Confidence: high, because the monitoring is 

robust. 

Preliminary results. Do not cite. 
 

Marble Canyon – Downward trend 1990-2023 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

Marble Canyon – Upward trend 1990-2023 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
Marble Canyon 2000-2023 

Upward trend Flat or downward trend 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

Grand Canyon – Downward trend or flat 1990-2023 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

Grand Canyon – Upward trend 1990-2023 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

Grand Canyon – Upward trend 1990-2023 

Hazel and others (2022); www.usgs.gov/apps/sandbar 
 

 

Grand Canyon – 2000-2023 

Upward trend Flat or downward trend 

Hazel and others (2022); www.usgs.gov/apps/sandbar