High Elevation Sand/Cultural Sites:

The response of source-bordering aeolian dunefields to the 2012-

2016 High Flow Experiments of the Colorado River in Grand Canyon 

Joel B. Sankey (jsankey@usgs.gov)

US Geological Survey,

Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ

Glen Canyon Dam Adaptive Management Program Annual Reporting Meeting,

March 13th, 2019, Phoenix, AZ
• Joel B. Sankey, US Geological Survey, SBSC, GCMRC, Flagstaff, AZ

• Alan Kasprak, US Geological Survey, SBSC, GCMRC, Flagstaff, AZ

• Joshua Caster, US Geological Survey, SBSC, GCMRC, Flagstaff, AZ

• Helen Fairley, US Geological Survey, SBSC, GCMRC, Flagstaff, AZ

• Amy East, US Geological Survey, CMSC, Santa Cruz, CA

• Jen Dierker, National Park Service, Grand Canyon, AZ

• Laura Durning, NAU, School of Informatics, Computing and Cyber Systems

• Ashton Bedford, NAU, School of Informatics, Computing and Cyber Systems

• Paul Grams, US Geological Survey, SBSC, GCMRC

• Dan Buscombe, NAU, School of Earth Science and Environmental Sustainability

• Temuulen T. Sankey, NAU, School of Informatics, Computing and Cyber Systems

The response of source-bordering aeolian dunefields to 

the 2012-2016 High Flow Experiments of the Colorado 

River in Grand Canyon 
Bare, unvegetated sand is important for recreation, habitat, and 

cultural resources along the Colorado River in Grand Canyon
River Corridor Remote Sensing 

Assessment of Bare 

Unvegetated Sand

https://www.aopa.org/news-and-media/allnews/2015/march/10/pilot-getaways-mineralcanyon-utah

RM 45

RM 53

RM 62

RM 58

(RM 0)

(RM 280) Sankey et al. 2018, Sand 

classifications along the Colorado River 

in Grand Canyon derived from 2002, 

2009, and 2013 high-resolution 

multispectral airborne imagery: U.S. 

Geological Survey data release, 

https://doi.org/10.5066/P99TN424.
The Distribution of Colorado River Sand in Grand Canyon

Kasprak et al., 2018, Quantifying and forecasting changes in the areal extent of river valley sediment in response to altered hydrology and land 

cover. Progress in Physical Geography, https://doi.org/10.1177/0309133318795846

~ 1/3 is almost always underwater

~ 1/6 is periodically underwater

Baseflow Discharge

HFE Discharge

~ 1/2 is above the HFE high water line

Bare, Unvegetated, Exposed Sand Area (m

2)
~ 1/3 is almost always underwater

~ 1/6 is periodically underwater

Baseflow Discharge

HFE Discharge

?

~ 1/2 is above the HFE high water line

The Distribution of Colorado River Sand in Grand Canyon

Bare, Unvegetated, Exposed Sand Area (m

2)

Kasprak et al., 2018, Quantifying and forecasting changes in the areal extent of river valley sediment in response to altered hydrology and land 

cover. Progress in Physical Geography, https://doi.org/10.1177/0309133318795846

Sankey et al. (2018a) The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley 

morphodynamics. Aeolian Research, 32, pp.228-245.

Sankey et al. (2018b) The response of source-bordering aeolian dunefields to sediment-supply changes 2: Controlled floods of the Colorado River in Grand 

Canyon, Arizona, USA. Aeolian Research, 32, pp.154-169.
• Dunefields aren’t inundated by contemporary discharges from GCD, and 

they are located above the stage of HFEs.

• Are they affected by dam operations? 
Lees Ferry Dunefield – Relict River Sediment Supply Example 

Remote sensing topographic change detection 2002-2013

Sankey et al. (2018a) The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics. 

Aeolian Research, 32, pp.228-245.
Lees Ferry Dunefield – Relict River Sediment Supply Example 

Remote sensing topographic change detection 2002-2013

Sankey et al. (2018a) The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics. 

Aeolian Research, 32, pp.228-245.
Lees Ferry Dunefield – Relict River Sediment Supply Example 

Remote sensing topographic change detection 2002-2013

Sankey et al. (2018a) The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics. 

Aeolian Research, 32, pp.228-245.

1923 (La Rue)

2017 (Fairley)
Soap Creek Dunefield – Modern River Sediment Supply Example

Sankey et al. (2018a) The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics. 

Aeolian Research, 32, pp.228-245.

Remote sensing topographic change detection 2002-2013
Did the 2012-16 HFEs resupply dunefields with sand by 

rebuilding upwind sandbars? 

Sankey et al. (2018b) The response of source-bordering 

aeolian dunefields to sediment-supply changes 2: 

Controlled floods of the Colorado River in Grand Canyon, 

Arizona, USA. Aeolian Research, 32, pp.154-169.
Dunefield response to HFEs

Sankey et al. (2018b) The 

response of source-bordering 

aeolian dunefields to sedimentsupply changes 2: Controlled 

floods of the Colorado River in 

Grand Canyon, Arizona, USA. 

Aeolian Research, 32, pp.154-169.
Dunefield response to HFEs

Sankey et al. (2018b) The 

response of source-bordering 

aeolian dunefields to sedimentsupply changes 2: Controlled 

floods of the Colorado River in 

Grand Canyon, Arizona, USA. 

Aeolian Research, 32, pp.154-169.
Dunefield response to HFEs

Sankey et al. (2018b) The 

response of source-bordering 

aeolian dunefields to sedimentsupply changes 2: Controlled 

floods of the Colorado River in 

Grand Canyon, Arizona, USA. 

Aeolian Research, 32, pp.154-169.
Dunefield response to HFEs

Change in dunefield sediment 

storage from aeolian processes (m

3)

Post-2012 HFE

Post-2013 HFE

Post-2014 HFE

Post-2016 HFE

Increase in sediment storage with consecutive annual HFEs

Sankey et al. (2018b) The response of 

source-bordering aeolian dunefields to 

sediment-supply changes 2: Controlled 

floods of the Colorado River in Grand 

Canyon, Arizona, USA. Aeolian 

Research, 32, pp.154-169.
Dunefield archaeological site response to HFEs

Unpublished results, do not cite

Increase in sediment storage owing to resupply from 2012-2016 HFE sand
Dunefield response to HFEs

Mean elevation change from

aeolian processes at the upwind 

dunefield boundary (m)

Post-2012 HFE

Post-2013 HFE

Post-2014 HFE

Post-2016 HFE

Aeolian 

resupply 

attributed to 

sediment from 

individual HFE

Resupply occurred for 50 % (8 of 16) of flood-dunefield instances

Analogous to resupply of sandbars by HFEs;

e.g., ~ 1⁄2 of monitored sandbars increased in size following the 

2012, 2013, 2014 HFEs (Grams et al., 2015)

Sankey et al. (2018b) The response of 

source-bordering aeolian dunefields to 

sediment-supply changes 2: Controlled 

floods of the Colorado River in Grand 

Canyon, Arizona, USA. Aeolian 

Research, 32, pp.154-169.
• In Grand Canyon, approximately 1⁄2 of the area of bare, unvegetated sand 

derived from the Colorado River is located in 117 large dunefields

• HFEs do not directly inundate most of these dunefields, however, HFEs resupply 

the dunefields with sand by rebuilding upwind sandbars

• Aeolian dunefields were resupplied with windblown sand from HFE deposits in 

half of the instances monitored after the 2012, 2013, 2014, and 2016 HFEs

• Frequency of dunefield resupply by HFEs is analogous to resupply of 

sandbars by HFEs

• Dunefield sediment storage increases cumulatively when HFEs are conducted 

consistently on an annual basis. Sediment storage decreased with 1-year 

hiatus from HFE in 2015.

• Sediment storage increased at dunefield archaeological sites owing to 

resupply from 2012-2016 HFE sand

Summary - The response of source-bordering aeolian dunefields to 

the 2012-2016 High Flow Experiments of the Colorado River in 

Grand Canyon 
Implications and Future Work

• Bare sand area has decreased by 49% since 1965 owing to a combination of 

vegetation expansion, increase in baseflow, and erosion (Kasprak et al., 2018).

• Bare sand area is projected to decrease by an additional 12% by 2037 due to 

future riparian vegetation expansion (Kasprak et al., 2018)

• The past, present, and likely future expansion of riparian vegetation onto 

sandbars reduces the supply of HFE sand for dunefields
Implications and Future Work

• Bare sand area has decreased by 49% since 1965 owing to a combination of 

vegetation expansion, increase in baseflow, and erosion (Kasprak et al., 2018).

• Bare sand area is projected to decrease by an additional 12% by 2037 due to 

future riparian vegetation expansion (Kasprak et al., 2018)

• The past, present, and likely future expansion of riparian vegetation onto 

sandbars reduces the supply of HFE sand for dunefields

1923 (La Rue) 2018 (Fairley)
Implications and Future Work

• In April, 2019 the NPS will implement experimental vegetation removal 

treatments in Grand Canyon to increase aeolian sediment supply to several 

dunefields that host archaeological sites

• GCMRC will monitor the outcome of the treatments relative to future HFEs