Amy Draut 

Research Geologist

U.S. Geological Survey, Santa Cruz, CA

Aeolian landscapes and 

archaeological sites: 2012 progress 

and new work plan (Project J)

January 23, 2013

U.S. Department of the Interior

U.S. Geological Survey
Processes shaping the landscape
Processes shaping the landscape
Processes shaping the landscape Size of flow (cfs)
What happens to upland landscapes = 

what happens to archaeological sites

 To understand 

processes and risks of 

site erosion, study at 

site- and landscapescale

 Highly likely that many 

yet-undocumented 

arch sites are within 

river-corridor dune 

fields
Scientific Context

 Fluvial (river) and aeolian (wind) sediment 

interactions are common worldwide, but the 

two processes are rarely studied together

 Scientific community sees need for more 

integrated studies (e.g., Belnap et al. 2011)

 Effects of river regulation on aeolian sand, 

upland geomorphology have not been 

studied elsewhere
2012 paper in Journal of Geophysical 

Research – Earth Surface
2012 paper in Journal of Geophysical 

Research – Earth Surface

 Significant differences (physical and 

biological) between aeolian landscapes with 

and without modern fluvial sand source

 Significant differences between aeolian 

landscapes of Grand, Cataract Canyons

 Conceptual model: floods, windblown sand 

supply, upland geomorphology and ecology
Unregulated

river

corridor

Regulated

river corridor
Aeolian landscapes form downwind of river 

sandbars: “source-bordering dunes” (Bullard & McTainsh, 2003)

WIND

Flood-deposited sandbar
New river sand moves inland by wind

HFEs supply new wind-blown sand to 

aeolian dunes where wind direction is 

right...
New river sand moves inland by wind

Surveys by Joe Hazel and the Nams, NAU
New river sand moves inland by wind

... but with modern (small) floods, some 

aeolian landscapes get sand, some don’t. 

To replenish sand in all aeolian 

landscapes (arch sites), floods would 

need to be much bigger.
Modern vs. Relict aeolian landscapes

Flow models by Magirl et al. (2008)

Magirl et al., 2008 

hydrologic/topographic model

Some get new sand from modern sandbars Others don’t.
Modern vs. Relict aeolian landscapes

Magirl et al., 2008 hydrologic/topographic model
Aeolian landscapes in GRCA largely 

originated from ‘extreme’ floods

Magirl et al., 2008
Aeolian landscapes in GRCA largely 

originated from ‘extreme’ floods

Magirl et al., 2008
Most, and largest, dune fields set by 

40-year flood (170,000 cfs)

Magirl et al., 2008
Most, and largest, dune fields set by 

40-year flood (170,000 cfs)

Magirl et al., 2008

 HFEs cover a 

small 

proportion of 

natural (predam) sand 

source area

 HFE deposits 

often too small, 

far away, 

blocked by 

riparian 

vegetation
Link between river sediment and 

upland aeolian landscapes

 Aeolian dunes get sand from fluvial (flood) sandbars

 Aeolian dunes without modern sand supply develop 

much more biologic soil crust, become less active
Aeolian dunes without modern sand supply:

Have:

More biologic crust

More vegetation

Less open sand

Less sand transport

Crusts stabilize sand, dunes immobile.
... compared with places that still get sand supply

More sand transport = dunes shift, migrate.

Artifacts covered/uncovered by dunes
Comparing active vs. inactive 

aeolian sand

“Active” aeolian 

sand has windrippled surfaces, 

slip faces at 

angle of repose 

(Lancaster, 1994)

Active

Inactive
Comparing active vs. inactive 

aeolian sand

Project J preview: 

Gullies in places 

like this

Active

Inactive
Proportions of active vs. inactive 

aeolian sand

 Mapped all aeolian sand 

locations in RM 44-61 

 Analyzed active / 

inactive sand area in GIS

Only 13% of aeolian sand 

area there is active
Compare with Cataract Canyon, Utah

Cataract Canyon

Grand Canyon

(Lees Ferry)

65% of aeolian sand area 

is active (Marble Canyon 

reach had 13%)
Sand activity in individual dune fields

 Some archaeologically significant dune fields have 

very little active sand area (mapped RM 66-72 in 2012)

 Influences susceptibility to gully incision

Palisades: 

1.6% active 

sand

70-mile: 4.1% active sand
Sand activity in individual dune fields

 Dune fields clearly getting HFE sand have higher % 

active sand area

 Probably less susceptible to gully incision

Basalt: 27% active sand
Project J: 2013-2014

Overview questions

 Do cultural sites erode or change faster or in a 

significantly different manner than they would if dam 

operations were different?

 How effective are HFEs at supplying aeolian sand to 

upland landscapes and archaeological sites, 

maintaining natural landscape structure and function?
Project J: 2013-2014

 J1: Cultural-site monitoring in Glen Canyon

 J2: Archaeological site condition, landscape 

processes at places benefiting from HFE sand

 J3: Large-scale landscape evolution – role of aeolian 

sand in limiting gully erosion; role of HFEs in 

maintaining aeolian sand activity
J1. Glen vs. Marble-Grand Canyon

 C:2:0032, C:2:0035, C:2:0075, C:2:0077

 Measure site topography with lidar 

(airborne & terrestrial), compare with 

previous data in Marble-Grand Canyon

 Compare weather records (Page vs. 

Phantom Ranch) with extent of erosion

 Input to geomorphic model of erosion 

(David Bedford)

 Are sites in Glen Canyon significantly more eroded 

than those downstream from Lees Ferry where 

fine-sediment supply is greater?
J2. Processes at sites that receive 

new aeolian sand from HFEs

 What number, proportion of archaeological sites can 

benefit from aeolian sand supply caused by HFEs?

 Aeolian sand is important at ~100 sites in Marble-Grand Canyon 

river corridor. Which are adjacent to and downwind of new HFE 

sandbars?

 Analyzing 2012 post-HFE oblique photos near each of those 

sites, using 1996 pre- and post-HFE aerial photos

 Short field visits in 2013 to identify local wind directions from 

surface geomorphology if no weather-station record nearby
J2. Processes at sites that receive 

new aeolian sand from HFEs

 At archaeological sites that receive HFE sand:

 Is aeolian sand transport, deposition enough to 

offset erosion and protect archaeological sites?

 Are gullying, deflation advanced enough to 

reduce site integrity?
J2. Processes at sites that receive 

new aeolian sand from HFEs

 Measure rainfall, wind at weather stations at 4 sites

 Terrestrial lidar scanning in 2013, 2014

 Stationary cameras for daily record of site conditions
J2. Processes at sites that receive 

new aeolian sand from HFEs

 At archaeological sites that receive HFE sand:

 What specific processes/conditions contribute to 

site stability or erosion – gullying, deflation, 

inflation, dune migration?

What types and rates of change at sites benefiting from HFEs? 
J3. Landscape-scale assessment

 How does relative abundance of active / inactive 

aeolian sand vary in different regions of the river 

corridor?

Hypothesis: Proportion of active sand will be less in wide reaches of 

the river corridor (where archaeological record is most extensive)
J3. Landscape-scale assessment

 How does the degree of gully erosion differ in 

sediment deposits that are active vs. inactive with 

respect to aeolian transport?

Hypothesis: Gullies will be more extensive, 

longer-lasting in inactive than in active sand.

True so far – of 1277 m of gully length mapped 

in RM 66-72, 98% in inactive sand deposits
J3. Landscape-scale assessment

 To what extent does aeolian sediment transport 

counteract or prevent gully incision?

Hypothesis: Aeolian sediment limits gully incision such that gullies are absent in 

places where, if not for aeolian sediment transport, they would be present.

Arroyo Grande, 1965 Arroyo Grande, 2004

 Aerial photograph analysis on decadal scales (Joel Sankey)

 Modeling (David Bedford) – model runoff on existing, smoothed 

terrain: does model predict gullies where instead dunes exist?
Project J: 2013-2014

Overview questions

 Do cultural sites erode or change faster or in a 

significantly different manner than they would if dam 

operations were different?

 How effective are HFEs at supplying aeolian sand to 

upland landscapes and archaeological sites, 

maintaining natural landscape structure and function?
Questions?

With thanks to:

Helen Fairley, Brian Collins, Joel Sankey, David Bedford, Skye Corbett

Josh East, Bob Tusso, Tom Gushue, Josh Logan
Ecosystem role of biologic crust

 Lichens, moss, 

cyanobacteria, fungi, 

algae

 Changes soil chemistry, 

nutrientes, plants, 

herbivore diet & 

abundance

 Loss of aeolian sand 

supply translates into 

upland ecosystem Heavily crusted dunes at Granite Park
What about loss of low flows?

 Loss of low flows post-dam means wind can’t 

mobilize sand from fluvial sandbars that were 

exposed in late summer/ fall

 Less important than loss of flood sand, 

because timing of low flows and driest, 

windiest weather didn’tcoincide. Pre-dam 

spring winds mostly reworked last year’s 

flood sand

 Low flows don’t expose sand upwind of large, 

archaeologically important dune fields
Most, and largest, dune fields set by 

40-year flood (170,000 cfs)

 HFEs cover a 

small 

proportion of 

natural (predam) sand 

source area

 HFE deposits 

often too small, 

far away, 

blocked by 

riparian 

vegetation
Open, bare sand space

These don’t These sites get modern windblown sand supply after HFEs

Box-and-whisker plots:

3rd quartile (x0.75)

Median (2nd quartile, x0.5)

1st quartile (x0.25)

Outliers: any points > 1.5 

times the inter-quartile range 

(box length)

Whiskers: highest and 

lowest non-outlier points

GC-Modern GC-Relict
Open, bare sand space

These don’t

p < 0.00001

t-test  p value 

Low p values mean the 

two groups are 

significantly different

These sites get modern windblown sand supply after HFEs

GC-Modern GC-Relict
Biologic soil crust

These don’t

p < 0.005

These sites get modern windblown sand supply after HFEs

GC-Modern GC-Relict
Vegetation cover

These don’t

p < 0.07

These sites get modern windblown sand supply after HFEs

GC-Modern GC-Relict
Sand transport by wind: raw data

These don’t These sites get modern windblown sand supply after HFEs

GC-Modern GC-Relict

378 measurements

at 14 sites

2003 - 2010
Sand transport by wind: normalized

These don’t

p < 0.05

These sites get modern windblown sand supply after HFEs

GC-Modern GC-Relict
What is the influence of Glen Canyon Dam 

operations above the high water line?

River-deposited (fluvial) 

sandbar

Wind-blown (aeolian) sand, 

upland landscapes
Example of gully filled by wind-blown sand 

from a controlled-flood deposit

Head of gully Middle of gully

Terminus of gully
Riparian vegetation growth will inhibit 

aeolian sand supply inland

Malgosa, 2005
Riparian vegetation growth will inhibit 

aeolian sand supply inland

Malgosa, 2010