Prepared in cooperation with Northern Arizona University

Gully Monitoring at Two Locations in Grand Canyon 

National Park, Arizona, 1996–2010, with Emphasis on 

Documenting Effects of the March 2008 High-Flow Experiment

U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2014–1211
Cover: Surveyors mapping the Palisades gully network after the 2008 high-flow experiment on the Colorado River, Grand Canyon National 

Park, Arizona. Photograph by A. East, U.S. Geological Survey, December 10, 2004.
Gully Monitoring at Two Locations in the 

Grand Canyon National Park, Arizona, 1996–2010, 

with Emphasis on Documenting Effects of the 

March 2008 High-Flow Experiment

By Nathan D. Schott, Joseph E. Hazel, Jr., Helen C. Fairley, Matt Kaplinski, and Roderic A. Parnell

Prepared in cooperation with Northern Arizona University

Open-File Report 2014–1211

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

For more information on the USGS—the Federal source for science about the Earth,

its natural and living resources, natural hazards, and the environment—visit 

http://www.usgs.gov or call 1–888–ASK–USGS

For an overview of USGS information products, including maps, imagery, and publications,

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Suggested citation:

Schott, N.D., Hazel, J.E., Jr., Fairley, H.C., Kaplinski, M., and Parnell, R.A., 2014, Gully monitoring at two locations in 

the Grand Canyon National Park, Arizona, 1996–2010, with emphasis on documenting effects of the March 2008 highflow experiment: U.S. Geological Survey Open-File Report 2014-1211, 32 p., http://dx.doi.org/10.3133/ofr20141211.

ISSN 2331-1258 (online)

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report.
iii

Contents

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 2

High-Flow Experiments.............................................................................................................................................. 4

Purpose and Scope ................................................................................................................................................... 4

Background ................................................................................................................................................................... 4

Study Site Descriptions.................................................................................................................................................. 7

Palisades Gully Network ............................................................................................................................................ 7

Furnace Flats Gully.................................................................................................................................................... 9

Methods........................................................................................................................................................................11

Results..........................................................................................................................................................................13

Changes as a Result of the 2008 High-Flow Experiment..........................................................................................13

Gully Thalweg Evolution............................................................................................................................................18

Channel Widening.....................................................................................................................................................21

Discussion ....................................................................................................................................................................23

2008 High-Flow Experiment......................................................................................................................................23

Long-Term Changes .................................................................................................................................................23

Palisades Gully Network .......................................................................................................................................24

Furnace Flats Gully ...............................................................................................................................................25

Base-Level Hypothesis..........................................................................................................................................26

Changing Methodologies ..........................................................................................................................................26

Conclusions and Suggestions for Future Work.............................................................................................................27

References Cited..........................................................................................................................................................28

Figures

Figure 1. Map showing (A) general location of study area within the Grand Canyon National Park, Arizona and 

(B) the two specific study areas in the eastern Grand Canyon National Park, Arizona.................................................. 3

Figure 2. Photograph showing mouth of the Palisades South gully, Grand Canyon National Park, Arizona,

February 9, 2008 ........................................................................................................................................................... 5

Figure 3. Aerial photograph showing Palisades study area, Grand Canyon National Park, Arizona, May 2002.......... 8

Figure 4. Photographs showing examples of erosion control structures constructed to reduce gully erosion at 

the Palisades South gully .............................................................................................................................................. 9

Figure 5. Aerial photograph showing Furnace Flats gully, Grand Canyon National Park, May 2002 ......................... 10

Figure 6. Selected repeat photographs showing the Palisades South gully as viewed looking northeast from 

the terminus near the Colorado River.......................................................................................................................... 14

Figure 7. Repeat photographs showing Palisades South gully upper mouth area from (A) April 19, 2007, 

11 months prior to the 2008 high-flow experiment and (B) April 4, 2008, just after the 2008 high- flow experiment .... 15

Figure 8. Cross sections across the mouth of the Palisades South gully, Grand Canyon National Park, Arizona ..... 16

Figure 9. Normalized profile of the Palisades North gully, Grand Canyon National Park, Arizona, 1998–2010......... 17

Figure 10. Cross sections at the Furnace Flats gully, Grand Canyon National Park, Arizona.................................... 19

Figure 11. Normalized long profile of the Palisades South gully, Grand Canyon National Park, 

Arizona, 2004–2010..................................................................................................................................................... 20
iv

Figure 12. Normalized short profile of the Palisades South gully, Grand Canyon National Park, 

Arizona, 1998–2010..................................................................................................................................................... 20

Figure 13. Normalized profile of the Furnace Flats gully, Grand Canyon National Park, Arizona, 1996–2008 .......... 21

Figure 14. Cross sections at the Palisades gully network established by the National Park Service, 

Grand Canyon National Park, Arizona, January 1998 ................................................................................................. 22

Tables

Table 1. Topographic surveys conducted at the Palisades South gully network, Grand Canyon 

National Park, Arizona................................................................................................................................................. 12

Table 2. Volume of scour and fill in the mouth of the Palisades South gully for the three high-flow 

experiments (HFE) and the intervals in between ......................................................................................................... 13

Conversion Factors and Datums

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

kilometer (km) 0.5400 mile, nautical (nmi) 

meter (m) 1.094 yard (yd) 

Volume

cubic meter (m3) 6.290 barrel (petroleum, 1 barrel = 42 gal)

Datums

Vertical and horizontal coordinate information is referenced to the 2007 realization of the National Spatial Reference System, 

North American Datum of 1983, NAD83 (NSRS2007), in meters. 

Elevation, as used in this report, refers to GPS derived ellipsoid height above the GRS80 ellipse, in meters, and not NAVD88 

orthometric height. 
1 

Gully Monitoring at Two Locations in the 

Grand Canyon National Park, Arizona, 1996–2010, 

with Emphasis on Documenting Effects of the 

March 2008 High-Flow Experiment

By Nathan D. Schott1, Joseph E. Hazel, Jr.

1, Helen C. Fairley2, Matt Kaplinski1, and Roderic A. Parnell1

Abstract

Many archeological sites in the Grand Canyon are being impacted by gully incision. In 

March 2008, a high-flow experiment (2008 HFE) was conducted with the intention of 

redistributing fine sediment (sand, silt, and clay) from the bed of the Colorado River to higher 

elevations along the channel margin. Deposition of fine sediment in gully mouths has been

hypothesized to slow gully erosion rates and lessen impacts to archeological sites. The effects of 

the 2008 HFE on gullies were evaluated by comparing the topographic changes of three gullies at 

two study sites before and after the 2008 HFE. Comparison results indicated that sediment was 

deposited in gully mouths during the 2008 HFE, and that the inundated areas nearest to the river 

can be extensively altered by mainstream flow during high-flow events. Additionally, the history of 

gully evolution at the two study sites was examined between 1996 and 2010 and indicated that 

gullies have been subjected to thalweg incision and gully widening processes over a decadal 

timescale. Although the small sample size precludes extrapolating the results to other gullies, the 

findings contribute to the understanding of gully erosion in archeologically significant areas and 

have implications for future monitoring of gully erosion and evaluating the effectiveness of check 

dams intended to mitigate that erosion at archaeological sites in the Grand Canyon National Park. 

 

1

Northern Arizona University.

2

U.S. Geological Survey.
2

Introduction

Completion of Glen Canyon Dam in 1963 altered the downstream hydrology of the 

Colorado River by significantly reducing the supply of fine sediment (sand, silt, and clay), 

eliminating the annual spring snowmelt flood, replacing seasonal flow fluctuations with a regime of 

daily fluctuations, and increasing average base flows (Howard and Dolan, 1981; Topping and 

others, 2000, 2003). The consequences of these changes include the lack of sediment redistribution 

to the channel margins, including sediment deposition in the lower elevations of gullies (Hereford 

and others, 1993; Fairley, 2005; Wright and others, 2005). The lack of sediment-rich floods in the 

post-dam era is suspected to have increased gully erosion rates in the Grand Canyon (Hereford and 

others, 1993; Thompson and Potochnik, 2000; Fairley, 2003), and several studies are currently 

underway to explore how the presence and operations of Glen Canyon Dam may have affected 

erosion rates at archaeological sites along the Colorado River (for example, Collins and others, 

2012; Sankey and Draut, 2014). 

Gully erosion occurs when surface runoff during intense rainfall is localized in sufficient 

volumes to cut well-defined channels into unconsolidated surficial deposits. It is an important and 

sometimes dominant process of sediment loss in many watersheds, especially in arid and semi-arid 

regions (Valentin and others, 2005). Understanding gully erosion in the Grand Canyon is of 

particular interest to resource managers due to the negative impact of erosion on the integrity of 

archaeological sites within the Colorado River corridor. In 1990–91, 475 archaeological sites were 

documented between Glen Canyon Dam and Separation Canyon (river mile 2403) by the Grand 

Canyon River Corridor Survey Project (Fairley and others, 1994). Many of these sites are located 

on poorly consolidated alluvial terraces and aeolian dunes, and are actively being eroded by gully 

incision (Fairley and others, 1994; Leap and others, 2000; Fairley 2003, 2005). Although gully 

erosion is not a recent phenomenon in the Grand Canyon, gully erosion in the pre-dam era was 

partially offset by fine-sediment redistribution into gullies during annual spring runoff floods and 

migration of aeolian dunes into gully areas (McKee, 1938; Hereford and others, 1993; Sankey and 

Draut, 2014). In the post-dam era, the sediment load and magnitude of floods have been greatly 

reduced (Topping and others, 2003), along with the redistribution of flood sands by wind (Draut 

and Rubin, 2008; Draut, 2012); the degree to which these changes affect the preservation of 

irreplaceable archaeological resources in the Grand Canyon is a subject of on-going investigations 

(for example, Collins and others, 2009, 2012; Fairley and others, 2012; Sankey and Draut, 2014). 

To help alleviate effects of the reduced sediment redistribution potential of the Colorado 

River downstream of Glen Canyon Dam, the Operation of Glen Canyon Dam Final Environmental 

Impact Statement and Record of Decision included the proposal to use experimental high flows, 

termed beach/habitat-building flows, to redistribute sand from the river channel bottom to higher 

elevations along the river margins (U.S. Department of the Interior, 1995, 1996). The preservation 

of cultural resources also was linked to the potential for future high flows to deposit fresh or 

renewed sand deposition in established gullies (Hereford and others, 1993). It was hypothesized 

that redistribution of sediment from the channel of the Colorado River to the mouths of gullies by 

beach/habitat-building flows (also referred to as High-Flow Experiments) would potentially slow 

or lessen gully incision rates, reducing impacts to archaeological sites (Hereford and others, 1993; 

Yeatts, 1996; Thompson and Potochnik, 2000).

 

3

Because of its historical precedence, river mile is used to describe locations along the Colorado River. River miles are 

measured downstream of Lees Ferry (fig. 1), along the centerline of the Colorado River.
3

Figure 1. Map showing (A) general location of study area within the Grand Canyon National Park, Arizona

and (B) the two specific study areas in the eastern Grand Canyon National Park, Arizona.
4

High-Flow Experiments

Prior to 2008, there were two high-flow experiments (HFEs) (Melis, 2011; Melis and 

others, 2011). The first HFE was a 7-day release of 1,274 m3/s in March 1996 (Webb and others, 

1999). The second HFE was a 60-hour peak release of 1,175 m3/s in November 2004 (2004 HFE) 

(Topping and others, 2006). The 2008 HFE involved another 60-hour release with a peak 

discharge of 1,203 m3

/s in March 2008 (Melis and others, 2011). Since completion of the 

study described in this report, there have been two additional HFEs, one in November 2012 

and another in November 2013, with peak discharges of 1,269 and 1,048 m3/s, respectively 

(http://www.gcmrc.gov/discharge_qw_sediment/station/GCDAMP/09380000). The magnitude of 

discharge during the highest HFEs is approximately twice the peak discharge from Glen Canyon 

Dam under normal operations, and about one-half of the 2-year recurrence peak flow of the 

unregulated Colorado River (Topping and others, 2003). 

Purpose and Scope

This study addresses two primary topics. First, we document the effects of the 2008 HFE on 

three individual gullies in the eastern Grand Canyon by comparing results of gully surveys obtained 

before and after the 2008 HFE. Second, we compare the results of the 2008 gully surveys to older 

surveys dating back to 1996, as well as to one gully survey conducted in April 2010. With this 12 

to 14 year dataset, we are able to make observations about the evolution of gullies in the Grand 

Canyon on a decadal timescale and to explore implications for archaeological resource preservation

at these sites. In addition to the two primary study goals, we also assess the total station survey 

methodology used in this and other studies. Finally, we discuss management implications of our 

findings and suggest ideas for future research. 

Background

Because of their size and proximity to known archaeological sites, two gullies located in the 

eastern Grand Canyon near Palisades Creek have received considerable attention from previous 

researchers (see Hereford and others, 1993; Hereford, 1996; Yeatts, 1996, 1998; Hazel and others 

2000, 2008a; Pederson and others 2003, 2006; Draut and others, 2005; Collins and others, 2009, 

2012). Hereford (1996) provided evidence indicating that two incipient gullies began incising the 

alluvial terrace at Palisades prior to 1965. Comparison of aerial photographs taken in 1965 and

1973 show the two gullies at the Palisades site to be stable, both terminating on the pre-dam terrace 

alluvium and not directly integrated with the Colorado River (Hereford, 1996). By October 1984, 

however, aerial photographs indicate substantial erosion at the two gullies, herein referred to as the 

Palisades North and South gullies. The photographs show that both the north and south gullies 

lengthened by 80 and 100 m, respectively, linking both channels directly to the Colorado River 

(Hereford, 1996). The marked incision was attributed to a period of unusually high rainfall that 

occurred between 1978 and 1984 (Hereford and others, 1993; Hereford, 1996). 
5

Hereford and others (1993) hypothesized that, in the pre-dam era, runoff from gully mouths 

would rapidly lose velocity and spread out to form small, low-gradient alluvial fans as it flowed 

unconfined over the porous, permeable sand of essentially horizontal terraces (Hereford, 1996). 

Prior to dam closure, annual overtopping of pre-dam terraces by the spring snowmelt flood 

“removed any previously formed alluvial fans and filled incipient channels through deposition and 

partial erosion of the terrace,” thus maintaining a constant “effective base level” 3–4 m above 

typical post-dam era flows (Hereford, 1996, p. 6). Hereford and others (1993) suggested that Glen 

Canyon Dam operations exacerbated gully erosion as the former terrace-based gullies became 

integrated with the Colorado River and adjusted to the lower effective base level of typical postdam flows in the absence of large floods (fig. 2). Thompson and Potochnik (2000) hypothesized 

that the HFE-deposited sediment in and around gully mouths could help mitigate gully erosion by 

backfilling gully mouths and increasing the amount of sand available for aeolian migration into 

upper portions of gullies. 

Figure 2. Photograph showing mouth of the Palisades South gully, Grand Canyon National Park, Arizona, 

February 9, 2008. View is to the northwest. Black arrows indicate a typical base flow of the Colorado River in 

the post-dam era of 351 cubic meters per second. Photograph by J. Hazel, Northern Arizona University. 
6

Investigating sediment deposition after the 1996 HFE, Yeatts (1996) found that sediment 

was deposited in gully mouths at three out of the four sites he studied, including the Palisades site. 

The sediment deposited by the 1996 HFE persisted for several years (Yeatts, 1998; Hazel and 

others, 2000). Hazel and others (2008a) described gully evolution in the mouth of the Palisades 

South gully between 1996 and 2005. They reported significant erosion between 1996 and 2004 

(approximately 63 m3), net deposition during the 2004 HFE (approximately 10 m3), and minor 

erosion between the 2004 HFE and May 2005. Neither Yeatts (1996, 1998) nor Hazel and others 

(2008a) were able to determine if HFE-deposited sediment had any effect on gully incision rates in 

the upper reaches of the gully.

Approaching the topic from a different angle, Wiele and Torrizo (2005) applied numerical 

modeling methods to simulate deposition near archaeologically sensitive areas under variable flow 

and sediment supply conditions. Their study focused on four short reaches of the Colorado River 

between river miles 66 and 70, including the two study areas discussed in this report. Their 

modeling results showed significant variability in deposition volumes related to channel shape, as 

well as to discharge and sand supply. They found that in two reaches, including the Palisades reach, 

sand deposition increased with stage and sand supply, but this pattern was not evident in the other 

two reaches. They concluded that trends in sand storage were more predictable in the reaches 

dominated by recirculation zones, such as the Palisades reach, than in reaches where sand storage is 

dependent on small-scale variations in channel margin morphology, such as in Upper Unkar reach, 

which includes the Furnace Flats gully site discussed in this report where the river is relatively 

wide (Wiele and Torrizo, 2005). 

Since 1995, the National Park Service has been installing and maintaining rock and brush 

check dams at selected gullies within and in close proximity to known archaeological sites, 

including the Palisades site (Leap and Coder, 1995). Direct measurements by Hazel and others 

(2008a) in 2004 indicated that in-channel flow had destroyed four check dams installed in the 

Palisades South gully in the late 1990s. Pederson and others (2003, 2006) investigated the 

effectiveness of check dams and other erosion-control structures (ECS) at Palisades and eight other 

sites. They concluded that ECS do reduce erosion if they are actively maintained and that brush 

check dams are more effective than rock check dams and result in less damage when breached; 

however, in all cases, damaged check dams exacerbate gully erosion. In an ongoing study at several 

archaeological sites, the use of terrestrial lidar techniques for monitoring gully erosion in the Grand 

Canyon National Park is being investigated to track larger landscape-level changes at 

archaeological sites (Collins and others, 2009, 2012); these studies show that deposition behind 

ECS can be detected using repeat lidar measurements (Collins and others, 2009). 

Addressing the hypothesis that HFEs can reduce gully erosion by increasing sources of 

sediment for aeolian migration into gully areas, Draut and Rubin (2008) and Draut and others 

(2009a, 2009b, 2010) described weather and aeolian sand-transport data at the Palisades site 

between 2004 and 2009. The 2008 weather station data showed that although the flood-formed 

sandbar riverward (southwest) of the study sites was enlarged substantially during the 2008 HFE, 

the dominant wind direction did not move sand from the sandbar into the dune field (Draut and 

others, 2009b). The dominant wind direction in 2008 was similar to conditions measured in 

previous years (Draut and Rubin, 2008; Draut and others, 2009a, 2009b). 
7

Study Site Descriptions

The three gullies examined in this report are all located within the Furnace Flats 

geomorphic reach of the eastern Grand Canyon described by Schmidt and Graf (1990). The greatest 

concentration of archeological sites in the Grand Canyon National Park occur within this 

geomorphic reach (approximate river miles 62 to 77), averaging more than five sites per kilometer 

(Fairley and others, 1994). Downstream of the Palisades fault near river mile 66, the Furnace Flats 

reach is characterized by a relatively wide and shallow river channel. Hereford and others (1993) 

identified and mapped a number of Holocene stream terraces consisting of sandy alluvium that are 

locally interbedded with aeolian sand and gravelly colluvium in this reach. Based on radiocarbon 

dating and archeological artifacts, these terraces formed between 770 B.C. and A.D. 1890 

(Hereford and others, 1996). Bedrock geology of the reach was mapped and described by Huntoon 

and others (1986). The surficial geology of the immediate area was mapped and described by 

Hereford (1996). Additional work on the local terrace sedimentology is described by Draut and 

others (2005). 

The three gullies discussed in this report occur within two study areas—the Palisades Site 

and the Furnace Flats Site (fig. 1). The Palisades Site includes two gullies which are referred to as 

the Palisades South Gully and the Palisades North Gully, respectively. Collectively, these two

gullies comprise the Palisades Gully Network. The third gully is located in the Furnace Flats Site 

and is simply referred to as the Furnace Flats Gully.

Palisades Gully Network

The Palisades study area encompasses two adjacent gullies located on river left (as viewed 

in a downstream direction) at river mile 66.1 (fig. 3). Both gullies are located on the downstream 

side of a large debris fan extending from the mouth of Palisades Creek. This large, low-gradient 

debris fan creates a zone of recirculating water (eddy) downstream of the debris fan. A complete 

description of the Palisades gully network, including catchment area and vegetative cover, is 

provided by Pederson and others (2003). 

The larger of the two gullies is the downstream, southernmost gully. This gully is more than

300 m in length and is approximately 1.5 m deep near the confluence with the Colorado River. 

Using the convention established by Pederson and others (2003), this gully is referred to as the 

Palisades South gully. The upstream gully, herein referred to as the Palisades North gully, is 

slightly more than 100 m in length and less than 0.75 m deep at its deepest point. Erosion- control 

structures, including rock and brush check-dams, rock armoring and other bank stabilization 

efforts, are present in both of these gullies (fig. 4). 
8

Figure 3. Aerial photograph showing Palisades study area, Grand Canyon National Park, Arizona, May 2002.

Volume boundary was used to calculate volume changes within the gully mouth. The Colorado River is on the 

left and is flowing from north to south. 
9

Figure 4. Photographs showing examples of erosion control structures constructed to reduce gully erosion at 

the Palisades South gully. (A) A rock check dam; (B) Wall armoring. View for both photographs is to the east. 

Photographs by J. Hazel, Northern Arizona University, April 1, 2008. 

Furnace Flats Gully

The third gully studied in this paper is located on river right at river mile 71.9 (fig. 5). 

Yeatts (1996) examined this site because it was an actively eroding gully, located in proximity to 

but not within known cultural sites. Although there are several gullies in this area, we report only 

on the gully called Furnace Flats #1 by Yeatts (1996, 1998) and Hazel and others (2000), herein 

referred to as the Furnace Flats gully. This gully is approximately 35 m long, 1 m wide, and 0.5 m 

deep, and has not been altered by ECS stabilization efforts.

In contrast to the Palisades gully network, which has part of the catchment area located on a 

tributary debris fan, the Furnace Flats gully has incised into an alluvial terrace that slopes up to an 

outcrop of Precambrian Dox Sandstone bedrock close to the Colorado River. The alluvial terrace 

consists of unconsolidated fine-grained, silty sand that was likely deposited as a channel margin bar 

due to bank irregularities that create minor flow obstructions at high water (Hazel and others, 2000; 

Wiele and Torrizo, 2005).
10

Figure 5. Aerial photograph showing Furnace Flats gully, Grand Canyon National Park, May 2002. The 1,203 

m3/s line is the high water mark of the 2008 high-flow experiment. The Colorado River flows from east to west. 
11

Methods

In order to quantify sediment deposition in gully mouths as well as other potential 

geomorphological changes associated with the 2008 HFE, surveys of the gully thalwegs, gully 

walls and immediately adjacent topography were completed in February 2008 and again in April 

2008 with electronic (optical) total stations, similar to previous studies at the sites (see Yeatts, 

1996; Hazel and others, 2000, 2008a). Pre-HFE surveys of the South and North Palisades gullies 

occurred on February 9, 2008. A pre-HFE survey of the Furnace Flats gully took place on 

February 10, but due to technical problems, most of those data were not recoverable. Post-HFE 

surveys took place on April 4, 2008, at the two Palisades gullies and April 5, 2008, at the Furnace 

Flats gully. On April 15, 2010, a third round of survey at only the Palisades South Gully was 

completed.

Field surveys were conducted to define gully mouth topography in the area between the 

river’s edge and the elevations reached by flows in excess of approximately 1,700 m3/s. Above this 

elevation, data collection was limited to a profile of the gully thalweg. Inter-gully areas were not 

surveyed in 2008 or 2010. An accuracy of ±0.05 m was identified as the minimum horizontal and 

vertical precision of total station acquired ground points (Hazel and others, 2008b). Survey 

accuracy was maintained by horizontal and vertical checks for positional error between known 

reference points in the Grand Canyon Monitoring and Research Center’s control network. Positions 

are referenced to NAD83(NSR2007) and projected to the 1983 State Plane Coordinate System, 

Arizona Central Zone (0202) grid. To allow for comparisons, all older survey data were converted 

to this common datum by Hazel and others (2008a). Water elevations reached by the Colorado 

River during the 2008 HFE and other flow events were based on established stage relations 

between discharge measured at USGS gaging stations and previously surveyed water-surface 

elevations and flood-debris strand lines (Hazel and others, 2006). In general, survey data were 

collected with a feature-based methodology using break lines to define distinct changes in slope 

(for example, gully walls), lines of equal elevation (that is, high water marks), and along the gully 

thalweg.

Where sufficient gully topography was collected, the gully topography was modeled using 

the triangulated irregular network (TIN) method for surface modeling using survey-grade computer 

software. Changes in deposit volumes were calculated using direct TIN-to-TIN comparisons. These 

calculations were made at the mouth of the Palisades South gully. As previously described in Hazel 

and others (2008a), point density was about one point per 0.75 m2 in the gully mouth areas. 

Because of changes to the gully mouth area, the volume boundary used by Hazel and others 

(2008a) was modified to fit the 2008 and 2010 data. All volume changes presented in table 2 use 

the modified volume boundary. In addition, cross sections were generated from the TINs at the 

same locations examined by Hazel and others (2008a). The cross-section endpoints at the Palisades 

site were originally established by the National Park Service in 1998. 

We compared gully thalweg profiles using the normalized profile method devised by 

Pederson and others (2003) and adopted by Hazel and others (2008a). Although previous surveys 

concentrated efforts on collecting gully thalweg profiles, different researchers collected gully 

thalweg data at differing point densities (table 1). Additionally, thalweg sinuosity may change 

between surveys as the gully responds to various factors such as the installation or breaching of 

check-dams. Because of these inconsistencies, difficulties arise in comparing gully thalweg profiles 

collected by different researchers at different times. The normalized profile method utilizes two 

fixed endpoints common to all surveys being compared. Endpoints used in this study are shown in 

figures 3 and 5. By normalizing the distance of each thalweg profile survey point from the upper 

endpoint, all thalweg profiles can be plotted along a common x-axis. At the Palisades South gully, 
12

two different sets of endpoints were used; the short profile compares recent thalweg profiles to data 

dating back to January 1998, whereas the long profile highlights gully thalweg evolution between 

2004 and 2010 at the upper reaches of the Palisades South gully.

Table 1. Topographic surveys conducted at the Palisades South gully network, Grand Canyon National Park, 

Arizona.

[Modified from Hazel and others, 2008a. Survey Description: Discharge elevation determined from a stage-discharge 

relation partly based on surveyed elevations of driftwood logs inferred to represent historical flood strandlines (Draut 

and others, 2005). NC, data not collected; m3

/s, cubic meters per second; pts/m, points per meter]

Survey date Source Survey description

Profile point density

(pts/m)

02-17-1996 Yeatts, 1996 Site topography to 1,700 m3/s NC

05-12-1996 Yeatts, 1996 Site topography up to 1,700 m3/s NC

02-28-1998

Grand Canyon National Park, K. 

Kohl, USGS, written commun., 

2006

Thalwegs, cross sections, and 

check dams 0.40

10-14-1998 Hazel and others, 2000 Site topography up to 2,000 m3

/s 0.39

10-7-1999 Hazel and others, 2000 Site topography up to 2,000 m3

/s 0.59

09-27-2002 Pederson and others, 2003 Thalweg profiles and check dams 1.02

11-11-2003 K. Brown, USGS, written

commun., 2006 Thalweg profiles 0.37

11-20-2004 Hazel and others, 2008a Gully topography up to 4,500 m3

/s 0.52

12-10-2004 Hazel and others, 2008a Gully topography up to 4,500 m3

/s 0.42

05-13-2005 Hazel and others, 2008a Site topography up to 4,500 m3

/s 0.43

02-09-2008 This study Site topography up to 1,700 m3

/s

Thalweg profile up to 4,500 m3

/s 0.34

04-04-2008 This study Site topography up to 1,700 m3

/s

Thalweg profile up to 4,500 m3

/s 0.28

04-15-2010 This study Site topography up to 1,700 m3

/s

Thalweg profile up to 4,500 m3

/s 0.46
13

Results

Changes as a Result of the 2008 High-Flow Experiment

The 2008 HFE resulted in 12 m3 of deposition and 11 m3 of erosion resulting in net 

deposition of 1 m3 of sediment in the predefined mouth area of the Palisades South gully during the 

2008 HFE (volume boundary shown in fig. 3). Net deposition from the 2008 HFE was less than the 

10 m3 of deposition attributed to the 2004 HFE, but greater than the 1 m3 of erosion measured after

the 1996 HFE (table 2). Surface elevations within the mouth of the Palisades South gully increased 

by as much as 0.6 m (figs. 6E, 7B, and 8C) 

In addition to depositing sediment in the mouth of the Palisades South gully, the 2008 HFE 

significantly reshaped and widened the mouth area (figs. 6 and 7). Cross sections located in the 

upper elevations of the Palisades South gully mouth indicate gully widening of 0.5–1 m within the 

gully mouth (figs. 8A and 8B).

Table 2. Volume of scour and fill in the mouth of the Palisades South gully for the three high-flow experiments 

(HFE) and the intervals in between.

[m3

, cubic meters]

Survey dates

Comparison 

interval

(days)

Scour

(m3)

Fill

(m3) 

Net change

(m3) 

Feb. 1996–May 1996

(1996 HFE) 85 9 8 − 1 

May 1996–Nov. 2004 3,114 66 3 − 63

Nov. 2004–Dec. 2004

(2004 HFE) 20 13 23 10

Dec. 2004–Feb. 2008 1,157 13 7 − 5 

Feb. 2008–April 2008

(2008 HFE) 54 11 12 1 

April 2008–April 2010 741 17 7 − 10
14

Figure 6. Selected repeat photographs showing the Palisades South gully as viewed looking northeast from 

the terminus near the Colorado River. (A) The gully area mouth as it appeared on November 20, 2004; (B) 

deposition in the gully bottom on December 10, 2004, as a result of the 2004 high-flow experiment; (C) gully 

mouth area as it appeared on April 19, 2007; (D) evidence of recent surface flow in the gully bottom 

(photograph taken on February 9, 2008); (E) deposition in the gully bottom on April 4, 2008, as a result of the 

2008 high-flow experiment. Photographs 6A and 6B by A. East; U.S. Geological Survey; photographs 6C-6E 

by J. Hazel, Northern Arizona University. 
15

Figure 7. Repeat photographs showing Palisades South gully upper mouth area from (A) April 19, 2007, 11 

months prior to the 2008 high-flow experiment and (B) April 4, 2008, just after the 2008 high- flow experiment. 

View is to the east. Effects of the 2008 high-flow experiment, including infilling of the gully thalweg and gully 

widening along the southern wall, can be observed. Photographs by J. Hazel, Northern Arizona University. 
16

Figure 8. Cross sections across the mouth of the Palisades South gully, Grand Canyon National Park, 

Arizona. (A) Cross section 1; (B) cross section 2; and (C) cross section 3. All cross section locations are 

shown in figure 3 and are viewed in a down-gully direction.
17

The weather station located near the Palisades site indicates that the largest rainfall event 

between February 9 and April 4, 2008, occurred on February 22, 2008, with 16.5 mm of 

precipitation in less than 24 hours (Draut and others, 2009a). We believe that this amount or any of 

the lesser precipitation events that occurred between our February and April surveys were 

insufficient to produce surface flow in the gully network. Therefore, we attribute all change in the 

Palisades South gully between February 9 and April 4, 2008, to the 2008 HFE. 

Because the Palisades North gully did not contain a discernible mouth area with measurable 

walls, only the thalweg profile was collected. Analysis of the Palisades North gully thalweg profile 

indicates no significant change between February and April 2008 (fig. 9). This result is consistent 

with the findings in Hazel and others’ (2008a) report, which documented that the Palisades North 

gully was largely unaffected by both the 1996 and 2004 HFEs. 

Figure 9. Normalized profile of the Palisades North gully, Grand Canyon National Park, Arizona, 1998–2010. 

Profile endpoints are shown in figure 3. Profile length between endpoints is approximately 86 meters. 
18

Because most of the data collected at the Furnace Flats gully prior to the 2008 HFE was not 

recoverable due to a technical problem with the data logger, our analysis of sediment deposition 

within the gully mouth is limited to one cross section located near the confluence with the Colorado 

River (cross section 10) (fig. 10A). Cross section 10 shows that the gully thalweg was buried by 0.3 

m of flood-derived fine sediment.

Gully Thalweg Evolution

Gully thalweg evolution between 2004 and 2010 of the entire ~308 m length of Palisades 

South gully, including the two main tributaries, is shown in figure 11. The 2004 thalweg profiles 

were collected at an average spacing of 1 point per 2.8 meters (pt/m), whereas the 2008 thalweg 

profile has a coarser spacing of 1 pt/3.6 m. The April 2010 thalweg data were collected at the 

highest density, with an average spacing of 1 pt/2.2 m. At elevations above those reached by the 

2004 HFE, no discernible change can be detected between the February 2004 and April 2010 

surveys of the gully thalweg. The variance in thalweg profiles is likely attributable to differences in 

point spacing between the surveys. Interpretation is further complicated by evidence of gully 

widening over this same time period (described in the next section, “Channel Widening”), as well 

as continued ECS maintenance by National Park Service personnel in March 2005 (Dierker and 

Leap, 2006), and possibly at other times not reported. 

Prior to 2004, detailed topographic surveys were focused on the lowest ~150 m of the 

Palisades South gully. Gully evolution between January 1998 and April 2010 of the lowest ~135 m 

of the Palisades South gully is shown in figure 12. Comparison of the surveys shows as much as 

0.8 m of thalweg incision between 1998 and 2010 between 797.5 m (stage elevation of ~2,020 

m3

/s) and the Colorado River at base flow. Most of the erosion evident below an elevation of 797.5 

m is attributed to knickpoint retreat resulting from an unusual weather system that produced 

widespread rain and tributary debris flows to the Colorado River in the vicinity of the Palisades 

gully network on September 7, 2002 (Hazel and others, 2008a). Above this elevation, no significant 

change was detected over the same time period.

Long-term thalweg evolution of the Palisades North gully is shown in figure 9. This gully 

has remained relatively unchanged during 12 years of monitoring. Check dam installation and 

maintenance may explain the lack of detectable change at this gully, but the lack of detectable 

change also may be attributable to the variable survey coverage and different point densities 

between surveys.
19

Figure 10. Cross sections at the Furnace Flats gully, Grand Canyon National Park, Arizona. (A) Cross 

section 10; (B) cross section 11; and (C) cross section 12. All cross section locations are shown in figure 5, 

and are viewed in a down-gully direction.
20

Figure 11. Normalized long profile of the Palisades South gully, Grand Canyon National Park, Arizona, 

2004–2010. Gully long profile endpoints are shown in figure 3. Profile length between endpoints is 

approximately 308 meters. 

Figure 12. Normalized short profile of the Palisades South gully, Grand Canyon National Park, Arizona, 

1998–2010. Gully short profile endpoints are shown in figure 3. Profile length between endpoints is 

approximately 135 meters. 
21

The evolution of the Furnace Flats gully thalweg (fig. 13) is markedly different than that of 

the Palisades North gully. The Furnace Flats gully thalweg aggraded between February 1996 and 

October 1998. Aggradation may be attributed to sediment deposition in the gully mouth during the 

1996 HFE, aeolian deposition, or gully-wall collapse. Some, but not all, of this aggradation was 

eroded between October 1998 and October 1999. The long-term evolution of the Furnace Flats 

gully is characterized by substantial erosion, as evidenced by more than 0.2 m of incision across the 

entire thalweg profile between October 1999 and April 2008. Average point spacing for the 

Furnace Flats thalweg surveys ranged from 1 pt/1.3 m to 1 pt/1.8 m between the different surveys. 

The Furnace Flats gully has received no erosion mitigation actions, is rarely visited by 

recreationists, and is perhaps a better reflection of natural gully evolution in the Grand Canyon. 

Figure 13. Normalized profile of the Furnace Flats gully, Grand Canyon National Park, Arizona, 1996–2008. 

Gully profile endpoints are shown in figure 5. Profile length between endpoints is approximately 23 meters. 

Channel Widening

Channel widening at Palisades was examined by comparing the 2008 surveys to the surveys 

collected by Hazel and others (2008a) in 2004 at cross-section locations established by the National 

Park Service in 1998. Repeat surveys of the cross sections provide another glimpse into long-term 

gully evolution. Nearly all cross sections at the Palisades gully network show varying degrees of 

gully-wall erosion or wall slumping since 1998. Cross section 4 (fig. 14A) shows gully widening of 

more than 0.5 m between January 1998 and April 2008. Cross section 5 (fig. 14B) shows evidence 

of gully-wall slumping and smoothing of the gully floor during the same 10-year period. Cross 

sections 6, 7, and 8 (figs. 14C, 14D, and 14E) also indicate evidence of gully-wall slumping. The 

one cross section established by the National Park Service at the Palisades North gully indicates 

substantial wall slumping and sediment redistribution within the gully (fig. 14F). At all Palisades 
22

Figure 14. Cross sections at the Palisades gully network established by the National Park Service, Grand 

Canyon National Park, Arizona, January 1998. (A) Cross section 4; (B) cross section 5; (C) cross section 6; 

(D) cross section 7; (E) cross section 8; and (F) cross section 9. All cross section locations are shown in figure 

3 and are viewed in a down-gully direction. Modified from Hazel and others (2008a).
23

cross sections, gully thalweg elevations changed very little over the decade after establishment of 

the cross sections. Thus, either the material eroded from gully walls was transported through the 

gully network during runoff events without affecting gully thalweg elevation, or thalweg incision 

was offset by sediment derived from slumping gully walls.

In contrast to the changes at the Palisades gullies, the cross sections at the Furnace Flats 

gully show progressive incision and gully widening between 1996 and 2008 (fig. 10). These cross 

sections were established by Hazel and others (2000). Cross section 10, located on a flooddeposited sandbar, has been discussed above. Cross section 11 shows the formation of a tributary to 

the main gully between October 1999 and April 2008 (fig. 10B). More than 0.5 m of gully 

widening is evident at cross section 12 (fig. 10C). Between 1996 and 2008, there was as much as 

0.3 m of thalweg incision above the elevation inundated during HFEs (figs. 10B and 10C).

Discussion

2008 High-Flow Experiment

Sediment was deposited into the mouth of the Palisades South gully by the 2008 HFE. The 

net deposition in 2008 was 1 m3, an amount considerably less than the 10 m3 deposited by the 2004 

HFE. The difference in sediment deposition may be explained by the available accommodation 

space within the gully mouth at the time of the 2008 HFE. Hazel and others (2008a) showed that 

the large difference in sediment deposition between the 1996 and the 2004 HFE was the result of 

0.5 m of gully thalweg incision in the mouth area between 1999 and the 2004 HFE, evacuation of 

63 m3 of material from the mouth area between the two floods, and complete removal of four check 

dams that were present in the 1990s, thus increasing accommodation space available for deposition 

during the 2004 HFE. In our present study, only about one-half of the 10 m3 of fine sediment 

deposited by the 2004 HFE had eroded prior to the 2008 HFE. Thus, remnant sediment from the 

2004 HFE reduced the amount of space available for 2008 HFE derived sediment, resulting in a 

reduced volume of deposition. However, we cannot rule out differences in sediment-supply and 

sand concentrations between the two HFEs as other causal factors contributing to the reduced 

depositional volume in 2008. 

The 2008 HFE also deposited fine sediment in the mouth of the Furnace Flats gully. The 

2008 HFE deposits buried a portion of the old gully thalweg under approximately 0.3 m of 

sediment (fig. 10A). Although the exact amount of sediment deposition cannot be calculated, the 

post-flood survey confirms that sediment was deposited in the gully mouth during the 2008 HFE. 

In contrast, the Palisades North gully remained relatively unaffected by all three HFEs, a response 

attributed to an inundation depth of less than 0.4 m during the HFEs (Hazel and others, 2008a).

Long-Term Changes

There is a distinct difference in the long-term changes observed at the Palisades gully 

network and the Furnace Flats gully, despite both being located in the Furnace Flats geomorphic 

reach of the eastern Grand Canyon. These differences may be explained by differing catchment 

types and areas, dissimilar sedimentology of the eroding substrate, distinctive vegetative cover, and 

altered micro-climate variables. The installation and maintenance of ECS also may play a role in 

explaining long-term differences.
24

Palisades Gully Network

Long-term topographic change at the Palisades South gully is markedly different above and 

below an elevation of 797.5 m (about 2,020 m3/s stage). Between this elevation and the Colorado 

River at base flow (about 794.6 m), significant erosion is evident (fig. 12). Prior to the 2008 HFE, 

most of the thalweg profile of the lower reaches of the Palisades South gully was approximately 0.5 

m lower than the thalweg elevation measured in January 1998. Although sediment was deposited in 

the elevations reached by experimental floods, by April 2010, the thalweg profile still remained 

about 0.3–0.4 m below the January 1998 profile. Much of this erosion has been explained by a 

large precipitation event that occurred on September 7, 2002 (see Hazel and others, 2008a). 

Gully widening, which mostly erodes sediment not deposited by recent HFEs, is among the 

most important threats to the preservation of cultural deposits and their associated artifacts. The 

lower reaches of the Palisades South gully also show evidence of erosion by means of gully 

widening processes (fig. 15), including gully-wall slumping and gully-wall retreat. Pederson and 

others (2006) suggest that damaged ECS, especially failed rock check dams, tend to further 

exacerbate erosion. Hazel and others (2008a) report that several check dams present in the lower 

reaches of the Palisades South gully in the 1990s had washed out prior to the 2004 HFE. To date, 

they have not been rebuilt and may be a contributing factor in explaining erosion at the lower 

elevations of the Palisades South gully. Our surveys also show that HFEs can widen gullies within 

Figure 15. Photograph showing an example of gully-wall slumping at the Palisades South gully, Grand 

Canyon National Park, Arizona. Photograph taken by J. Hazel, Northern Arizona University, April 19, 2007.
25

the inundation zone. Although we may not be able to determine all causal factors, we do know that 

the lowest elevations of the Palisades South gully have shown progressive erosion by means of 

thalweg incision and gully widening processes over the monitoring record. 

The uppermost elevations of the Palisades South gully show relatively little change between 

2004 and 2010 (fig. 11). Although slight thalweg aggradation is evident between 2004 and 2008, 

explaining the aggradation in the upper reaches is complicated by point spacing issues and 

installation and maintenance of ECS in March 2005 (Dierker and Leap, 2006). Evidence of gullywall slumping in the higher elevations of the Palisades South gully (fig. 15) may explain the slight 

increase in gully thalweg elevation between 2004 and 2008. Although gully widening is a natural 

process in the Grand Canyon, some have suggested that it might be exacerbated by anthropogenic 

influences during monitoring efforts (see Collins and others, 2008), installation and maintenance 

(or lack thereof) of ECS (Pederson and others, 2006), and excavation of at-risk cultural sites 

(Collins and others, 2012). Although identifying the causes of gully widening, anthropogenic or 

not, is beyond the scope of this study, we conclude that the gully thalweg did slightly aggrade at the 

higher elevations of the Palisades South gully between 2004 and 2008. We attribute this 

aggradation to both widening of the gully (and deposition of this gully side-wall material in the 

thalweg), and infilling behind recently installed or maintained ECS. By April 2010, all evidence of 

thalweg aggradation had disappeared, and the thalweg profile very closely resembled the profile 

observed in November and December 2004. Gully-wall slumping and anthropogenic influences 

likely mitigated any thalweg incision that might have occurred between 2004 and 2010 in the 

uppermost reaches of the Palisades South gully. 

The Palisades North gully remained relatively stable between January 1998 and April 2008. 

We attribute the differences in the gully thalweg profiles shown in figure 9 to the variance caused 

by the different spacing of the ground points used to generate the profile, and the fact that not all 

surveyors collected thalweg profile data at exactly the same locations along the thalweg. Both 

brush and rock check dams were constructed at the Palisades North gully in 1995 and have been 

maintained or rebuilt in February 1997, February 1998, April 2000, October 2000, March 2003, 

March 2004, and March 2005 (Dierker and Leap, 2006), and perhaps at other times not yet 

reported. We believe that installation and maintenance of ECS, including check dams and wall 

armoring, could be partially responsible for stabilizing this gully. Slumping of the gully wall 

(shown in fig. 14F) and redistribution of this material to the thalweg also may play a role in the 

stability of the Palisades North gully profile.

Furnace Flats Gully

The Furnace Flats gully is an actively eroding gully, showing evidence of thalweg incision, 

gully widening, and formation of new tributaries to the main gully. The Furnace Flats gully is not 

located at a known archaeological site, so no cultural artifacts or structures have been lost as a 

result of gully erosion; however, this gully is similar in size and extent to other gullies located 

nearby where archaeological artifacts have been observed (see 

http://www.nps.gov/grca/historyculture/archeology-excavation.htm).
26

No excavations, monitoring, or check dam installations have occurred at the Furnace Flats 

site, so widening at this gully can be interpreted as a natural process that may or may not have been 

exacerbated by recent survey activities. Explaining why the Furnace Flats gully is actively eroding 

while the Palisades North gully (a gully similar in size) is stable is complicated by differences in 

catchment area, substrate, and slope. Geomorphic and sedimentological studies of the catchment 

area and the eroding substrate would help to separate the influence of ECS from other factors 

affecting erosion rates and characteristics at the two sites. More intense data collection efforts also 

would aid in understanding erosion characteristics as this site. 

Base-Level Hypothesis

Some scientists have suggested that the introduction of experimental floods in the Grand 

Canyon may be able to offset and potentially even reverse some gully erosion by back-filling gully 

mouths, thereby temporarily raising the “effective” base level of gullies and replenishing the sand 

sources that support additional back-filling of gullies by aeolian processes (Hereford and others, 

1993; Yeatts, 1996; Thompson and Potochnik, 2000; see also U.S. Department of Interior, 2008). 

Hereford and others (1993) suggested that the effective base-level of gullies has decreased by 3 or 

4 m in the post-dam era. Although our study shows that sediment has been deposited in gully 

mouths during HFEs, increases in the gully bottom elevations generally are less than 1 m. 

Our study also shows that HFE deposits are relatively short-lived, limiting their ability to 

impact long-term gully stability. HFE-derived sediment is fine-grained, unconsolidated, and highly 

erodible. In the gullies investigated in this report, most HFE derived sediment was evacuated from 

the mouth area within a couple of years. 

Because a multitude of factors affect gully erosion in the Grand Canyon, we believe that the 

gullies reported on in this investigation may not be representative of all gullies in the Grand 

Canyon. Although HFEs do appear to temporarily increase the lower thalweg elevation of certain 

gullies in the Grand Canyon, there is no evidence from the present study to indicate that these 

short-term changes in gully thalweg elevation influence long-term erosion rates. 

Changing Methodologies

Monitoring gully erosion at our study sites is complicated by differences in survey 

procedures. All surveys analyzed in this study were collected using electronic total stations.

However, because the gully survey project was one piece of a larger survey effort where time and 

resources were limited, some gully surveys focused on mapping the gully thalweg, while others 

concentrated on measuring gully cross sections. Certain surveys focused data collection in gully 

mouths; others surveyed the entire gully. Inter-gully areas have received attention in just a few 

studies (for example, Collins and others, 2009, 2012). The differing extents and densities of 

surveys complicate comparison. While methods such as normalizing thalweg profiles and 

interpolating cross sections from TIN surfaces allow us to track gully evolution, the lack of a 

consistently applied methodology has introduced unnecessary uncertainty. Much of this uncertainty 

could be eliminated by establishing and maintaining a standardized and detailed survey procedure. 
27

A systematic, canyon-wide approach is required to comprehensively monitor gully erosion 

in the Grand Canyon. Methods described in this report were sufficient to track gully widening and 

deposition in selected gullies over time; however, in order to more completely understand gully 

erosion, in the Grand Canyon, a more comprehensive approach is needed. A comprehensive 

approach would evaluate and categorize all gullies in the Colorado River ecosystem using a suite of 

relevant attributes (for example, geological setting, size of catchment, gradient, substrate 

characteristics) and then select a stratified random sample of gully systems to monitor intensively 

over a period of years. Monitoring the topography of the selected gullies could be accomplished 

with total stations using a standardized protocol, or using alternate survey methodologies. Groundbased lidar (light detection and ranging) is a promising technology that can provide high-density 

survey data and is especially useful and cost-effective for measuring detailed changes in 

topography of inter-gully terrain. Airborne lidar offers a practical, albeit expensive, technique for 

quantifying gully erosion for the hundreds of gullies that are potentially unearthing archaeological 

sites in the Grand Canyon. Other remote sensing techniques, such as analysis of aerial 

photography, offer another avenue for documenting the evolution of many gullies over long timescales, although this method precludes precise quantification of change (Collins and others, 2014). 

Whatever method is selected, it is important that future monitoring and mapping efforts be carried 

out with consistent, replicable protocols to ensure that data can be systematically and rigorously 

collected and compared over time.

Conclusions and Suggestions for Future Work

 This study has found that HFE deposits temporarily increase the thalweg elevation in some 

gully mouths. These increases typically were less than 0.6 m at the sites we studied. Additionally, 

this study reconfirmed previous observations indicating that increases in gully mouth elevation due 

to deposition of unconsolidated, highly erodible sediment are short-lived in the Grand Canyon. 

Thus, unless HFEs are of greater magnitude in the future, and occur with greater frequency than 

they have in the recent past, deposition of sediment in gully mouths by future HFEs is not likely to 

change gully erosion rates significantly, and gully erosion will likely continue until gullies have 

equilibrated with the post-dam base-level flows.

Our ability to understand gully erosion and the role of dam operations in contributing to the 

erosion of archaeological sites in the Grand Canyon has been hampered by the lack of a welldesigned, consistent approach to monitoring changes in physical context. To help understand gully 

evolution and rates of gully erosion or aggradation in the Grand Canyon, it is imperative that future

mapping encompass the entire length of gullies and their tributaries. Standardized data-collection 

methodologies, including increased cross-section analysis and use of an appropriately designed 

sample of gullies that reflect the range of geomorphic, topographic, and substrate diversity, along 

with maintained and unmaintained ECS plus a control group of unmodified gullies, would allow 

for a rigorous evaluation of the effects of erosion control treatments and gully-wall slumping on 

gully erosion/aggradation rates. Mapping of intervening terrain, sedimentological studies of 

catchment areas and the eroding substrate, and precise measurement of local weather events and the 

resulting runoff also can aid in increasing our understandings of gully erosion in the Grand Canyon. 

Until a well-coordinated monitoring program can be implemented and carried out consistently over 

an extended time period, it will be difficult to determine the primary factors affecting gully 

erosion/aggradation rates and thus, determine the best strategies for protecting cultural resources. 
28

References Cited

Collins, B.D., Brown, K.B., and Fairley, H., 2008, Evaluation of Terrestrial LIDAR for monitoring 

geomorphic change at archaeological sites in Grand Canyon National Park, Arizona: U.S. 

Geological Survey Open-File Report 2008-1384, 60 p., http://pubs.usgs.gov/of/2008/1384/. 

Collins, B.D., Corbett, S.C., Fairley, H.C., Minasian, D., Kayen, R., Dealy, T.P., and Bedford, 

D.R., 2012, Topographic change detection at select archeological sites in Grand Canyon National 

Park, Arizona, 2007–2010: U.S. Geological Survey Scientific Investigations Report 2012-5133, 

77 p. 

Collins, B.D., Minasian, D., and Kayen, R., 2009, Topographic change detection at select 

archaeological sites in Grand Canyon National Park, Arizona, 2006-2007: U.S. Geological 

Survey Scientific Investigations Report 2009-5116, 97 p., http://pubs.usgs.gov/sir/2009/5116/. 

Collins, B.D., Corbett, S.C., Sankey, J.B., and Fairley, H.C., 2014, High-resolution topography and 

geomorphology of select archeological sites in Glen Canyon National Recreation Area, Arizona: 

U.S. Geological Survey Scientific Investigations Report 2014–5126, 31 p., 

http://dx.doi.org/10.3133/sir20145126.

Dierker, J., and Leap, L.M., 2006, Fiscal year 2005 archaeological site monitoring and 

management activities along the Colorado River in Grand Canyon National Park: Grand Canyon 

National Park and Northern Arizona University, Draft report submitted to the Bureau of 

Reclamation, Report no. 91, 151 p. 

Draut, A., 2012, Effects of river regulation on aeolian landscapes, Colorado River, southwestern 

USA: Journal of Geophysical Research – Earth Surface, v. 117, F2, doi:10.1029/2011JF002329. 

Draut, A.E., Andrews, T., Fairley, H.C., and Brown, C.R., 2009a, 2007 weather and aeolian sandtransport data from the Colorado River corridor, Grand Canyon, Arizona: U.S. Geological 

Survey Open-File Report 2009-1098, 110 p., http://pubs.usgs.gov/of/2009/1098/. 

Draut, A.E., and Rubin, D.M., 2008, The role of eolian sediment in the preservation of archeologic 

sites along the Colorado River corridor in Grand Canyon National Park, Arizona: U.S. 

Geological Survey Professional Paper 1756, 71 p., http://pubs.usgs.gov/pp/1756]. 

Draut, A.E, Rubin, D.M., Dierker, J.L., Fairley, H.C., Griffiths, R.E., Hazel, J.E., Jr., Hunter, R.E., 

Kohl, K., Leap, L.M., Nials, F.L., Topping, D.J., and Yeatts, M., 2005, Sediment and 

stratigraphy of the Palisades, Lower Comanche, and Arroyo Grande Areas of the Colorado River 

corridor, Grand Canyon, Arizona: U.S. Geological Survey Scientific Investigations Report 2005-

5072, 74 p., http://pubs.usgs.gov/sir/2005/5072/. 

Draut, A.E., Sondossi, H.A., Hazel, J.E., Jr., Andrews, T., Fairley, H.C., Brown, C.R., and 

Vanaman, K.M., 2009b, 2008 weather and aeolian sand-transport data from the Colorado River 

corridor, Grand Canyon, Arizona: U.S. Geological Survey Open-File Report 2009-1190, 98 p., 

http://pubs.usgs.gov/of/2009/1190/. 

Draut, A.E., Sondossi, H.A., Dealy, T.P., Hazel, J.E., Fairley, H.C., and Brown, C.R., 2010, 2009 

weather and aeolian transport data from the Colorado River corridor, Grand Canyon, Arizona: 

U.S. Geological Survey Open-File Report 2010-1166, 98 p., http://pubs.usgs.gov/of/2010/1166/. 

Fairley, H.C., 2003, Changing river—Time, culture, and the transformation of landscape in Grand 

Canyon—A regional research design for the study of cultural resources along the Colorado River 

in lower Glen Canyon and Grand Canyon, National Park, Arizona: Statistical Research, Inc., 

Technical Series 79, 

http://www.gcmrc.gov/library/reports/cultural/Archaeology/Fairley2003.pdf. 

Fairley, H.C., 2005, Cultural resources in the Colorado River corridor, in Gloss, S.P., Lovich, J.E., 

and Melis, T.S., eds., The state of the Colorado River ecosystem in Grand Canyon: U.S. 

Geological Survey Circular 1282, p. 177–192. 
29

Fairley, H.C., Bungart, P.W., Coder, C.M., Huffman, J., Samples, T.L., and Balsom, J.R., 1994, 

The Grand Canyon river corridor survey project–Archaeological survey along the Colorado 

River between Glen Canyon Dam and Separation Rapid: Flagstaff, Ariz., Bureau of Reclamation 

Glen Canyon Environmental Studies Program, cooperative agreement no. 9AA-40-07920. 

Fairley, H.C., Draut, A., Collins, B., Corbett, S., Bedford, D., Davis, P., and Sankey, J., 2012, 

Project J—Monitoring cultural resources and at small scale and defining the large-scale 

geomorphic context of the processes affecting cultural resources, in Department of Interior, 

Bureau of Reclamation, Upper Colorado River Regional Office, and U.S. Geological Survey, 

Grand Canyon Monitoring and Research Center: Glen Canyon Dam Adaptive Management 

Program Biennial Budget and Work Plan—Fiscal Years 2013–14., p. 220–268, 

http://www.usbr.gov/uc/rm/amp/amwg/mtgs/12aug29/Attach_08b.pdf. 

Hazel, J.E., Jr., Kaplinski, M., Manone, M., and Parnell, R., 2000, Monitoring arroyo erosion of 

pre-dam river terraces in the Colorado River ecosystem, 1996–1999, Grand Canyon National 

Park, AZ: Flagstaff, Ariz., Report on file at the Grand Canyon Monitoring and Research Center, 

29 p. 

Hazel, J.E., Jr., Kaplinski, M., Parnell, R.A., and Fairley, H.C., 2008a, Aggradation and 

degradation of the Palisades gully network, 1996 to 2005, with emphasis on the November 2004 

high-flow experiment, Grand Canyon National Park, Arizona: U.S. Geological Survey Open-File 

Report 2008-1264, 14 p. 

Hazel, J.E., Jr., Kaplinski, M., Parnell, R., Kohl, K., and Schmidt, J.C., 2008b, Monitoring finegrained sediment in the Colorado River Ecosystem, Arizona—Control network and conventional 

survey techniques: U.S. Geological Survey Open-File Report 2008-1276, 15 p. 

Hazel, J.E., Jr., Kaplinski, M., Parnell, R., Kohl, K., and Topping, D.J., 2006, Stage-discharge 

relations for the Colorado River in Glen, Marble, and Grand Canyons, Arizona: U.S. Geological 

Survey Open-File Report 2006-1243, 7 p. 

Hereford, R., 1996, Map showing surficial geology and geomorphology of the Palisades Creek 

area, Grand Canyon National Park, Arizona: U.S. Geological Survey Miscellaneous 

Investigations Series Map I-2449, scale 1:2000 (with discussion). 12 p. 1 plate. 

Hereford, R., Fairley, H.C., Thompson, K.S., and Balsom, J.R., 1993, Surficial geology, 

geomorphology and erosion of archeologic sites along the Colorado River, eastern Grand 

Canyon, Grand Canyon National Park, Arizona: U.S. Geological Survey Open-File Report 93-

517, 45 p., 4 pl. 

Hereford, R., Thompson, K.S., Burke, K.J., and Fairley, H.C., 1996, Tributary debris fans and Late 

Holocene alluvial chronology of the Colorado River, eastern Grand Canyon, AZ: General 

Services Administration Bulletin, v. 108, no. 1, p. 3–19. 

Howard, A., and Dolan, R., 1981, Geomorphology of the Colorado River in Grand Canyon: Journal 

of Geology, v. 89, no. 3, p. 269–297. 

Huntoon, P.W., Billingsley, G.H., Breed, W.J., Sears, J.W., Ford, T.D., Clark, M.D., Babcock, 

R.S., and Brown, E.H., 1986, Geological map of the eastern part of Grand Canyon National Park, 

Arizona: Grand Canyon, Ariz., Grand Canyon Natural History Association, scale 1:62,500. 

Leap, L.M., and Coder, C.M., 1995, Erosion control project at Palisades delta along the Colorado 

River corridor, Grand Canyon National Park: Salt Lake City, Utah, River Corridor Monitoring 

Project, Report no. 73 prepared for the Bureau of Reclamation. 

Leap, L.M., Kunde, J.L., Hubbard, D.C., Andrews, N., Downum, C.E., Miler, A., and Balsom, J.R., 

2000, Grand Canyon Monitoring Project 1992-1999—Synthesis and Annual Monitoring Report 

FY99: Salt Lake City, Utah, Grand Canyon National Park River Corridor Monitoring Project 

Report No. 66, submitted to Bureau of Reclamation. 
30

McKee, E.D., 1938, Original structures in Colorado River flood deposits: Journal of Sedimentary 

Petrology, v. 8, no. 3, p. 77–83. 

Melis, T.S., ed., 2011, Effects of three high-flow experiments on the Colorado River ecosystem 

downstream from Glen Canyon Dam, Arizona: U.S. Geological Survey Circular 1366, 147 p. 

Melis, T.S., Grams, P.E., Kennedy, T.A., Ralston, B.E., Robinson, C.T., Schmidt, J.C., Schmit, 

L.M., Valdez, R.A., and Wright, S.A., 2011, Three experimental high-flow releases from Glen 

Canyon Dam, Arizona—Effects on the downstream Colorado River ecosystem: U.S. Geological 

Survey Fact Sheet 2011-3012, 4 p. 

Pederson, J.L., Petersen, P.A., MacFarlane, W.W., Gonzales, M.F., and Kohl, K., 2003, Mitigation, 

monitoring, and geomorphology related to gully erosion of cultural sites in Grand Canyon: 

Flagstaff, Ariz., Grand Canyon Monitoring and Research Center, Final report in fulfillment of 

Cooperative Agreement CA-01-WRAG-0074, 250 p., 

http://www.gcmrc.gov/library/reports/cultural/Archaeology/Pederson2003.pdf. 

Pederson, J.L., Peterson, P.A., and Dierker, J.L., 2006, Gullying and erosion control at 

archaeological sites in Grand Canyon: Earth Surface Processes and Landforms, v. 31, 

p. 507−525.

Sankey, J.B., and Draut, A.E., 2014, Gully annealing by aeolian sediment—Field and remotesensing investigation of aeolian–hillslope–fluvial interactions, Colorado River corridor, Arizona, 

USA: Geomorphology, v. 220, p. 68–80, ISSN 0169-555X, 

http://dx.doi.org/10.1016/j.geomorph.2014.05.028. 

Schmidt, J.C., and Graf, J.B., 1990, Aggradation and degradation of alluvial sand deposits, 1965 to 

1986, Colorado River, Grand Canyon National Park, Arizona: U.S. Geological Survey 

Professional Paper 1493, 74 p. 

Thompson, K.S., and Potochnik, A.R., 2000, Development of a geomorphic model to predict 

erosion of pre-dam Colorado river terraces containing archaeological resources: Flagstaff, Ariz., 

SWCA, Inc., SWCA Cultural Resources Report No. 99-257, prepared for Grand Canyon 

Monitoring and Research Center. 

Topping, D.J., Rubin, D.M., and Vierra, L.E., Jr., 2000, Colorado River sediment transport pt.1—

Natural sediment supply limitations and the influence of the Glen Canyon Dam: Water Resources 

Research, v. 36, no. 2, p. 515–542. 

Topping, D.J., Rubin, D.M., Schmidt, J.C., Hazel, J.E., Jr., Melis, T.S., Wright, S.A., Kaplinski, 

M., Draut, A.E., and Breedlove, M.J., 2006, Comparison of sediment-transport and bar-response 

results from the 1996 and 2004 controlled-flood experiments on the Colorado River in Grand 

Canyon: CD-ROM Proceedings of the Eighth Federal Inter-Agency Sedimentation Conference, 

Reno, Nev., April 26, 2006, ISBN 0-9779007-1-1.

Topping, D.J., Schmidt, J.C., and Vierra, L.E., Jr., 2003, Computation and analysis of the 

instantaneous-discharge record for the Colorado River at Lees Ferry, Arizona—May 8, 1921, 

through September 30, 2000: U.S. Geological Survey Professional Paper 1677, 118 p. 

U.S. Department of the Interior, 1995, Operation of Glen Canyon Dam final environmental impact 

statement, Colorado River Storage Project, Coconino County, Arizona: Salt Lake City, Utah, 

Bureau of Reclamation, Upper Colorado Regional Office, Utah, 337 p. 

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

Environmental Impact Statement, Colorado River Storage Project, Coconino County, Arizona: 

Salt Lake City, Utah, Bureau of Reclamation, 337 p. 

U.S. Department of the Interior, 2008, Final environmental assessment for experimental releases 

from Glen Canyon Dam, Arizona, 2008 through 2012: Salt Lake City, Utah, Bureau of 

Reclamation, 68 p., accessed October 19, 2010, at 

http://www.usbr.gov/uc/envdocs/ea/gc/2008hfe/index.html. 
31

Valentin, C., Poesen, J., and Li, Y., 2005, Gully erosion—Impacts, factors and control: Catena, v. 

63, p. 132–153. 

Webb, R.H., Schmidt, J.C., Marzolf, G.R., and Valdez, R.A., eds., 1999, The controlled flood in 

Grand Canyon—Scientific experiment and management demonstration: Washington, D.C., 

American Geophysical Union, Geophysical Monograph Series, v. 110, 367 p. 

Wiele, S.M., and Torizzo, M., 2005, Modeling of sand deposition in archeologically significant 

reaches of the Colorado River in Grand Canyon, USA, in Bates, P., Lane, S., and Ferguson, R., 

eds., Computational Fluid Dynamics — Applications in Environmental Hydraulics: West Sussex, 

England, John Wiley and Sons, p. 357–394. 

Wright, S.A., Melis, T.S., Topping, D.J., and Rubin, D.M., 2005, Influence of Glen Canyon Dam 

operations on downstream sand resources of the Colorado River in Grand Canyon, in Gloss, S.P., 

Lovich, J.E., and Melis, T.S., eds., The state of the Colorado River ecosystem in Grand Canyon: 

U.S. Geological Survey Circular 1282, 1,731 p. 

Yeatts, M., 1996, High elevation sand deposition and retention from the 1996 spike flow—An 

assessment for cultural resources stabilization: Report on file at the Grand Canyon Monitoring 

and Research Center, Flagstaff, Ariz., 32 p. 

Yeatts, M., 1998, High elevation sand retention following the 1996 spike: Report on file at the 

Grand Canyon Monitoring and Research Center, Flagstaff, Ariz., 15 p. 
32

This page left intentionally blank 
Publishing support provided by the U.S. Geological Survey

Science Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the

 SBSC staff, Southwest Biological Science Center

U.S. Geological Survey

2255 N. Gemini Drive

Flagstaff, AZ 86001 

http://sbsc.wr.usgs.gov/
Schott and others—Gully Monitoring at Two Locations in Grand Canyon National Park, Arizona, 1996–2010—Open-File Report 2014–1211

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141211