U.S. Department of the Interior

U.S. Geological Survey

Conditions and Processes Affecting Sand Resources at 

Archaeological Sites in the Colorado River Corridor

Amy E. East, Pacific Coastal and Marine Science Center

Brian D. Collins, Geology, Minerals, Energy, & Geophysics Science Center

Joel B. Sankey, Grand Canyon Monitoring and Research Center

Skye C. Corbett, Geology, Minerals, Energy, & Geophysics Science Center

Helen C. Fairley, Grand Canyon Monitoring and Research Center

Joshua Caster, Grand Canyon Monitoring and Research Center
East, A.E., Collins, B.D., Sankey, J.B., Corbett, S.C., Fairley, H.C., and Caster, J., 2016, 

Conditions and processes affecting sand resources at archeological sites in the Colorado River 

corridor below Glen Canyon Dam, Arizona: U.S. Geological Survey Professional Paper 1825, 

104 p., http://dx.doi.org/10.3133/pp1825.
The problem: Landscapes downstream from Glen Canyon Dam contain archaeological 

resources that are affected by fluvial (river), aeolian (wind), and hillslope (gravity and 

rainfall-runoff) geomorphic processes.

The question: Can Colorado River sediment enhance the preservation of river-corridor 

archeological resources in these landscapes through aeolian sand deposition and 

mitigation of gully erosion?

The results: Relatively few archeological sites are now ideally situated to receive aeolian sand 

supply from sandbars deposited by recent controlled floods from Glen Canyon Dam.

The possible solutions to increase preservation potential for sand-dependent resources:

Sediment-rich high flows above 45,000 CFS, and/or 

Seasonal low flows below 8,000 CFS, and/or 

Riparian vegetation removal

“Active” River Channel

East et al., 2016 Professional Paper 1825
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)

Landscapes downstream from Glen Canyon Dam 

contain archaeological resources that are affected by 

geomorphic processes
Sand can potentially help preserve archaeological 

features by direct burial and/or by mitigating gullying
Aeolian sand exists within a variety of landscape 

characteristics along the river corridor...
Aeolian sand exists within a variety of landscape 

characteristics along the river corridor (cont’d)

“Active” w/ respect 

to aeolian transport “Inactive” w/ 

respect to aeolian 

transport
Aeolian sand is currently predominantly sourced

from river sandbars and therefore from 

controlled floods (High Flow Experiments)...
Aeolian sand is currently predominantly sourced

from river sandbars and therefore from 

controlled floods (High Flow Experiments) (cont’d)

“A” previous slide

Approximate elevation of controlled floods

Direction of wind

Direction of Colorado River Flow

Pre-flood Post-flood
Aeolian dune 

6.5 years after 2008 HFE 

41, 000 CFS

Sandbar

1 month after 2008 HFE 

Aeolian 

dune 

7 months 

after 2008 

HFE 

Joe Hazel, Northern Arizona University,

unpublished data, do not cite

Higher elevation River

valley margin
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Objectives

 Are archeological sites in the Colorado River corridor eroding or 

changing faster or in a significantly different manner than they would 

if Glen Canyon Dam were operated differently than it has been?

 What number, and what proportion, of cultural sites in the Colorado 

River corridor potentially receive aeolian sand supply from controlled 

flood flows?

 How effective is aeolian sand activity as a gully-annealing process?

 Does aeolian sand supply from controlled-flood sandbars to 

archeological sites cause enough deposition to offset erosion, and 

thereby protect the archeological resources? 

 In areas with modern aeolian sand supply, and with land surfaces 

undergoing both gully erosion and active aeolian sand transport, is there 

net sediment loss and topographic lowering such that cultural resources 

are affected?
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Potential Aeolian Sand Supply to 

River-Corridor Archeological Sites in 

Grand Canyon National Park

What number, and proportion, of cultural sites in 

the Colorado River corridor potentially receive 

aeolian sand supply from controlled flood flows?

East et al., 2016 

Professional Paper 

1825
Potential Aeolian Sand Supply to River-Corridor 

Archeological Sites in Grand Canyon National Park

What number, and proportion, of 

cultural sites in the Colorado 

River corridor potentially receive 

aeolian sand supply from 

controlled flood flows?

Number of Sites

East et al., 2016 Professional Paper 1825
What number, and proportion, of 

cultural sites in the Colorado 

River corridor potentially receive 

aeolian sand supply from 

controlled flood flows?

Number of Sites

Potential Aeolian Sand Supply to River-Corridor 

Archeological Sites in Grand Canyon National Park

East et al., 2016 Professional Paper 1825
What number, and proportion, of 

cultural sites in the Colorado 

River corridor potentially receive 

aeolian sand supply from 

controlled flood flows?

Number of Sites

Potential Aeolian Sand Supply to River-Corridor 

Archeological Sites in Grand Canyon National Park

How is this related to dam operations?

“Under current dam operations, elevated baseflows and infrequent HFEs without sediment rich large floods 

greater than 45,000 CFS promote the expansion of riparian vegetation onto bare sand and limit the duration of 

time that sand is subaerially exposed and therefore available for aeolian transport.”

How is this science useful for river management?

“1. For every single archaeological site we have the data to determine how and why it is affected by dam 

operations. And we went through this exact exercise in multiple meetings with DOI including the BOR and NPS 

during 2015 and 2016.

2. The geomorphic and biological processes that we highlight here are the same for archaeological sites as they 

are for other areas within the landscape outside of the active river channel. This means that we can similarly 

identify effects of dam operations for camp sites and other river-derived sediment deposits within and above the 

active river channel

3. These data give us a trajectory of expected future changes in sand resources as a function of dam 

operations. The timeline here specifically suggests that under current dam operation protocols, there will be a 

future trajectory of dwindling sand source areas below the stage of HFEs and dwindling sand resources above 

the stage of HFEs”

Small white text in quotes was not on original slide, but paraphrases what Joel said orally in presentation
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Gullies and Aeolian Sand Activity in the Geomorphic 

Context of the Colorado River Corridor

How effective is aeolian sand activity 

as a gully-annealing process?

Gullies are less prevalent in river 

reaches w/ more sand that is active 

w/ respect to aeolian transport

active

inactive

East et al., 2016 Professional Paper 1825
Gullies and Aeolian Sand Activity in the Geomorphic 

Context of the Colorado River Corridor

How effective is aeolian sand activity 

as a gully-annealing process?

Gullies are less prevalent in river 

reaches w/ more sand that is active 

w/ respect to aeolian transport

active

inactive

How is this related to dam operations?

“Under current dam operations, elevated baseflows and infrequent HFEs without sediment rich large floods greater than 

45,000 CFS promote the expansion of riparian vegetation onto bare sand and limit the duration of time that sand is 

subaerially exposed and therefore available for aeolian transport. This in turn results in landscapes above the stage of HFEs

that contain less active aeolian sand and are therefore more erodible by rainfall runoff than they could be if the dam were 

operated differently.”

How is this science useful to river management?

“This science is useful because we have produced an inventory of sand resources than spans the active river channel to the 

historic high water zone and those data can be used as a baseline for tracking changes into the future. Specifically the data

can be used to simulate effects of different hydrographs for sand resources at and above the HFE stage.“

Small white text in quotes was not on original slide, but paraphrases what Joel said orally in presentation
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Landscape Change at Archeological Sites Receiving 

Sand Supply After Controlled Floods, Grand Canyon 

National Park

Does aeolian sand supply from controlled-flood sandbars to archeological sites cause 

enough deposition to offset erosion, and thereby protect the archeological resources? 

In areas with modern aeolian sand supply, and with land surfaces undergoing both gully 

erosion and active aeolian sand transport, is there net sediment loss and topographic 

lowering such that cultural resources are affected?

East et al., 2016 Professional Paper 1825
Landscape Change at Archeological Sites Receiving 

Sand Supply After Controlled Floods, Grand Canyon 

National Park

Does aeolian sand supply from controlled-flood sandbars to archeological sites cause 

enough deposition to offset erosion, and thereby protect the archeological resources? 

In areas with modern aeolian sand supply, and with land surfaces undergoing both gully 

erosion and active aeolian sand transport, is there net sediment loss and topographic 

lowering such that cultural resources are affected?

East et al., 2016 Professional Paper 1825
Landscape Change at Archeological Sites Receiving 

Sand Supply After Controlled Floods, Grand Canyon 

National Park

Does aeolian sand supply from controlled-flood sandbars to archeological sites cause 

enough deposition to offset erosion, and thereby protect the archeological resources? 

In areas with modern aeolian sand supply, and with land surfaces undergoing both gully 

erosion and active aeolian sand transport, is there net sediment loss and topographic 

lowering such that cultural resources are affected?

How is this related to dam operations?

“We infer that under dam operations during this time frame sand loss from erosion exceeded aeolian deposition of riverderived sand. However, it is clear that these sites are coupled with upwind river sand supplies (sandbars). It is also clear 

that river-sourced sand deposition is a time-dependent process, and the outer limit of that process may extend for many 

years after any individual HFE for example.”

How is this science useful for river management? 

“There can be a slow response to individual HFEs. Here we specifically see that the amount of aeolian deposition 

between the 2010 and 2013 interval and the 2013 to 2014 interval suggest that the current protocol of potentially annual 

HFEs in conjunction with targeted vegetation removal could produce a net sediment surplus at some of these sites. 

However we would need to be able to both work with the data we currently have and collect more data to determine 

this.”

Small white text in quotes was not on original slide, but paraphrases what Joel said orally in presentation
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Landscape Change at Archeological Sites in a 

Sediment-Starved Reach: Glen Canyon National 

Recreation Area

Downstream of Glen Canyon 

Dam, but upstream of the Paria

River at Lees Ferry (sand 

supply for controlled floods)

East et al., 2016 Professional Paper 1825
Landscape Change at Archeological Sites in a 

Sediment-Starved Reach: Glen Canyon National 

Recreation Area

Downstream of Glen Canyon 

Dam, but upstream of the Paria

River at Lees Ferry (sand 

supply for controlled floods)

How is this science useful for river management?

“The one site in Glen Canyon that experienced net aeolian deposition is not sourced so much by an upwind sand bar 

as by an older, higher elevation and unvegetated terrace. This emphasizes the utility of maintaining sand sources that 

aren’t covered by vegetation above the HFE stage

This work also underscores the fact that Glen Canyon is subject to a different suite of processes compared to Grand 

Canyon because it is sediment starved. And because of this our emphasis is now really on trying to help Glen Canyon 

NPS staff monitor cumulative effects of dam operations to terraces and specifically terrace erosion.”

”

How is this related to dam operations?

“These results show us that without a modern river sand supply, sites and landscapes above the stage of HFEs are 

dominated by erosion

” 

Small white text in quotes was not on original slide, but paraphrases what Joel said orally in presentation
Outline

1) Introduction and Background (8 slides)

2) Project Objectives (1 slide)

3) Potential Aeolian Sand Supply to River-Corridor Archeological 

Sites in Grand Canyon National Park (3 slides)

4) Gullies and Aeolian Sand Activity in the Geomorphic Context of 

the Colorado River Corridor (1 slide)

5) Landscape Change at Archeological Sites Receiving Sand 

Supply After Controlled Floods, Grand Canyon National Park (2 

slides)

6) Landscape Change at Archeological Sites in a Sediment-Starved 

Reach: Glen Canyon (1 slide)

7) Conclusions and A Path Forward (6 slides)
Conclusions

 Most of the river-corridor archeological sites are not ideally 

situated to receive aeolian sand supply from sandbars 

deposited by recent controlled floods from Glen Canyon 

Dam, and therefore are at elevated risk of net erosion under 

present dam operations.

 For archeological sites that depend upon river-derived 

sand, we infer elevated erosion risk owing to a combination 

of reduced sand supply (both fluvial and aeolian) through 

(1) the lower-than-natural flood magnitude, frequency, and 

sediment supply of the controlled-flooding protocol; (2) 

reduction of open, dry sand area available for wind 

redistribution under current normal (nonflood) dam 

operations, which do not include flows as low as natural 

seasonal low flows and do include substantial daily flow 

fluctuations; and (3) impeded aeolian sand entrainment and 

transport owing to increased riparian vegetation growth 

due to high baseflows and in the absence of larger, morefrequent floods.

East et al., 2016 Professional Paper 1825
Path Forward

 The possible solutions to increase preservation potential 

for sand-dependent resources

 Sediment-rich high flows above 45,000 CFS, and/or

 Seasonal low flows below 8,000 CFS, and/or

 Riparian vegetation removal

East et al., 2016 Professional Paper 1825
Path Forward – What are we doing in Project 4 to address possible 

solutions and provide science that is useful for river management?

Kasprak and others, preliminary examples, do not cite

Low Flows Large Floods
Kasprak and others, preliminary examples, do not cite

Path Forward – What are we doing in Project 4 to address possible 

solutions and provide science that is useful for river management?

Estimates increase with better 

incorporation of vegetation data 
Path Forward – What are we doing in Project 4 to address possible 

solutions and provide science that is useful for river management?

Kasprak and others, preliminary examples, do not cite

Small decreases in 

low flows

= large increases in 

exposed sand
Path Forward – What are we doing in Project 4 to address possible 

solutions and provide science that is useful for river management?

Kasprak and others, preliminary examples, do not cite

Riparian vegetation 

removal = more 

exposed sand
Path Forward – What are we doing in Project 4 (TWP) to 

address possible solutions and provide science that is useful 

for river management?

?

?

Time
Professional Paper 1825 Acknowledgements

 This study was supported by funding from the Bureau of Reclamation 

through the U.S. Geological Survey (USGS) Grand Canyon Monitoring 

and Research Center, and was conducted in collaboration with the 

National Park Service (NPS; Grand Canyon National Park and Glen 

Canyon National Recreation Area). 

 We thank:

 David Bedford (USGS), 

 David Rubin, Jack Schmidt, Paul Grams, Ted Melis, Ivo Lucchitta, 

Richard Hereford, Bob Webb, Keith Kohl, Carol Fritzonger, Seth 

Felder, Dave Foster, Mark Mastin, Katherine Jacques, Jacqueline 

Olson (USGS),

 Jennifer Dierker and Thann Baker (NPS), 

 Mary Barger (Bureau of Reclamation),

 Aaron Borling, Joe Hazel, Paul Rauss,Carolyn Alvord, Don Bacco, 

Kirk Burnett, Mark Perkins, Dom Zanzucchi,Kathleen Nicoll, Joel 

Pederson (various affiliations)
East, A.E., Collins, B.D., Sankey, J.B., Corbett, S.C., Fairley, H.C., and Caster, J., 2016, 

Conditions and processes affecting sand resources at archeological sites in the Colorado River 

corridor below Glen Canyon Dam, Arizona: U.S. Geological Survey Professional Paper 1825, 

104 p., http://dx.doi.org/10.3133/pp1825.