U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2008–1264

In cooperation with Northern Arizona University

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
This page intentionally left blank 
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

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

Open-File Report 2008–1264

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Suggested citation:

Hazel, Joseph E., Jr., Kaplinski, Matt, Parnell, Roderic A., and Fairley, Helen C., 2008, 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.
iii

Contents

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

Introduction.....................................................................................................................................................1

Physical Setting..............................................................................................................................................2

Methods...........................................................................................................................................................4

Results. .............................................................................................................................................................5

Changes Detected as a Result of the 2004 High-Flow Experiment...............................................5

South Gully Changes between December 2004 and May 2005.....................................................6

Comparison of the 1996 Controlled Flood and the 2004 High-Flow Experiment .........................6

Changes above the Elevations Reached by Experimental High Dam Releases.........................9

Discussion and Conclusions......................................................................................................................10

Acknowledgements.....................................................................................................................................13

References....................................................................................................................................................13

Figures

1. Maps showing the location of study area................................................................................2

2. Aerial photograph taken in May 2002 showing the Palisades gully network....................3

3. Photographs of the Palisades gully network taken on November 17, 2004........................4

4. Longitudinal gully profiles showing the stage elevations reached by flows of 227 m3/s 

and 1,161 m3/s and the mouth area discussed in the text......................................................5

5. Palisades drainage network topography constructed from the point data collected on 

November 20, 2004........................................................................................................................7

6. Pre- and post-flood centerline longitudinal profiles of the south gully mouth...................8

7. The south gully mouth viewed from the terminus at the Colorado River............................8

8. Pre- and post-flood changes along the centerline longitudinal profile of the south 

gully.................................................................................................................................................9

9. South gully mouth time series constructed from the average centerline elevation data 

in figure 8......................................................................................................................................10

10. Normalized longitudinal profiles .............................................................................................. 11

11. Cross sections established by the National Park Service in January 1998......................12

Tables

1. Topographic surveys conducted at the Palisades drainage network .................................6

2. Volume of sediment scoured and filled at the south gully.....................................................7

3. Lower and middle section gully slope gradients, February 1998–May 2005 ....................11
iv
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

By Joseph E. Hazel, Jr.1, Matt Kaplinski 1, Roderic A. Parnell 1, and Helen C. Fairley2

Abstract

This study examines a large drainage network incised 

into alluvial terraces located along the Colorado River downstream of Palisades Creek in Grand Canyon National Park, 

Ariz. Gully erosion in the drainage affects archaeological sites 

found on the wide, relatively flat alluvial terraces. In 1996, 7-d 

release of 1,274 cubic meters per second of water from Glen 

Canyon Dam, known as a controlled flood, deposited finegrained sediment—sand, silt, and clay—in the mouth of the 

network’s largest gully, informally known as south gully. The 

deposit persisted for several years, but the drainage network 

steepened in the downstream reaches between 1999 and 2004. 

A high-flow experiment similar to the 1996 controlled flood 

was conducted in November 2004. The 2004 experiment 

was of a lower magnitude and shorter duration compared to 

the 1996 controlled flood. Topographic surveys were made 

in the field before, immediately after, and 6 months following the November 2004 experiment, and these measurements 

were compared to those made in 1996 and in other years. 

Similar to the response in 1996, fine-grained sediment was 

deposited in the mouth of the south gully and this mass was 

largely retained during the 6 months following the 2004 event. 

The magnitude of deposition in 2004 was nearly two times 

greater than that resulting from the 1996 controlled flood. 

We attribute this marked difference to increased accommodation space for deposition in the gully mouth, which was more 

deeply eroded in 2004 than it was in 1996. The second of the 

two primary gullies found within the Palisades gully network, 

the north gully, was largely unaffected by either high flow. 

Between 1996 and 2005, erosion was primarily confined 

to the lower reach of the south gully, while the upper reach 

remained relatively stable. The available data suggest that 

local base-level changes in the south gully mouth were not 

linked to the stability of the upstream gully reach. It could 

not be determined whether temporary base-level increases 

or maintenance of erosion-control structures were causal 

factors in limiting erosion in the upstream reaches of the 

drainage network.

Introduction

This study examines topographic changes within a large drainage network that has incised alluvial terraces located along 

the Colorado River downstream of Palisades Creek in eastern 

Grand Canyon National Park, Ariz. (fig. 1). This area is known 

as the Palisades gully network. Prehistoric archaeological 

sites associated with these terraces (Fairley and others, 1994) 

are being affected by gully incision during intense, localized 

rainfall events and, to a lesser extent, by aeolian deflation and 

visitor impacts (Leap and others, 2000; Pederson and others, 

2003, 2006; Fairley, 2003). Increased erosion has been linked 

to a period of more intense precipitation during the mid1970s and to the presence and operation of Glen Canyon Dam 

(Hereford and others, 1993; Thompson and Potochnik, 2000). 

Closure of Glen Canyon Dam in 1963 altered the downstream 

hydrology of the Colorado River by cutting off the upstream 

sediment supply and eliminating flood flows; these changes 

have possibly affected the preservation potential of archeological sites (Draut and others, 2005). 

The Operation of Glen Canyon Dam Final Environmental 

Impact Statement included the testing of occasional high-flow 

releases from Glen Canyon Dam to redistribute channel-stored 

sediment to the banks of the Colorado River (U.S. Department 

of Interior, 1995). The deposition of sediment in gully mouths, 

which would potentially lessen or slow incision rates and thus 

reduce impacts to archaeological sites, was among one of the 

possible benefits thought to derive from redistributing sand 

using high-flow releases. The first high-flow release test was 

a 7-d release of 1,274 cubic meters per second (m3

/s) of water 

from Glen Canyon Dam from March 26 to April 2, 1996 (hereafter 1996 controlled flood; Webb and others, 1999). Topographic mapping of the Palisades drainage network before and 

after the 1996 controlled flood indicated that sediment was 

1

 Northern Arizona University, Department of Geology, Flagstaff, Ariz. 

2

 U.S. Geological Survey, Southwest Biological Science Center, Flagstaff, 

Ariz.
2 Aggradation and Degradation of the Palisades Gully Network, 1996 to 2005

deposited in the larger of the two main gullies (Yeatts, 1996). 

Repeat surveys in the years following the 1996 controlled 

flood demonstrated that the deposit remained largely intact as 

late as 1999 (Yeatts, 1998; Hazel and others, 2000); however, 

renewed incision, knickpoint development, and widening were 

observed in 2002 (Pederson and others, 2003).

In the present study, we surveyed the Palisades gully 

network immediately before, 2 weeks after, and 6 mo after 

a November 2004 high-flow experiment (HFE). The experiment began on Sunday, November 21, 2004, when the Bureau 

of Reclamation opened the bypass tubes of Glen Canyon 

Dam for 90 h. The peak high flows ran for 2.5 d (60 h) at 

about 1,160 m3/s. Similar to the 1996 controlled flood, the 

2004 experiment was designed to redistribute new tributarysupplied sediment to the channel margins (Topping and others, 

2006). We compare the data collected for the 2004 experiment 

with similar surveys conducted before and after the 1996 controlled flood and in other years to describe gully changes over 

a 9-yr period. The accuracy and utility of conventional total 

station ground surveys for change detection of gully erosion is 

also discussed.

Physical Setting

The study site is located at river mile 66.1 (66.1 river 

miles downstream from Lees Ferry, Ariz.) on the left bank (as 

viewed in a downstream direction) of the Colorado River in 

easternmost Grand Canyon, Ariz. (fig. 2). This area is within 

the “Furnace Flats” geomorphic reach of the Colorado River, as 

defined by Schmidt and Graf (1990). The Furnace Flats reach 

is characterized by a relatively wide, shallow channel. Bedrock 

at river level is the Precambrian Dox Formation and overlying 

Cardenas Basalt, and cemented Quaternary gravels (Huntoon 

and others, 1986). The drainage network is located on the 

downstream side of a large, low-gradient debris fan present at 

the mouth of Palisades Creek (Hereford and others, 1993).

The drainage network is actively eroding surficial deposits 

that consist of fluvial-derived fine-grained sediment, locally 

interbedded with aeolian sand and gravelly colluvium (fig. 

3A). Hereford and others (1993) mapped four extensive terrace 

deposits at the site that date from before A.D. 950 to slightly 

before 1890, based on archaeological artifacts and radiocarbon 

ages (Hereford, 1996; Hereford and others, 1996). Largely inactive aeolian dunes are located adjacent to and on top of the fluvial terraces described by Hereford and others (1993). The dune 

field is bordered at the eastern margin by ponded, playa-like 

deposits that are partly composed of slope wash from the nearby 

Dox Formation (fig. 3B). Aeolian deposits are closely associated 

or interbedded with the fluvial and ponded deposits (Draut and 

others, 2005). Vegetation is relatively sparse and consists of a 

small number of tamarisk (Tamarix ramosissima) and arrowweed (Pluchea sericea) bordering the river margin; mesquite 

trees (Prosopis glandulosa), grasses, and cryptogamic crust are 

present elsewhere (appendix F in Pederson and others, 2003).

37o

111o 112o 113o

36o

0 50 Kilometers

Streamflow-gaging station

Lake Mead

Lake Powell Glen

Canyon

Dam

Paria River

UTAH

ARIZONA

ARIZONA

Map Area

Grand Canyon National Park

L i t t l e

C o l o ra do

R i v e r Cameron

Grand Canyon

Lees Ferry

Colorado

River

Map area

shown below

EXPLANATION

Li ttle C o l oradoR iv er

River

36o 00'

111o 45'

36o 07' 30"

111o 52' 30"

Navajo Indian Reservation Boundary

Grand Canyon National Park Boundary

Palisades

of Desert

the

Comanche

Point

Cape

Solitude

Kaibab National Forest

Desert View

64

Colorado

Carbon

Creek Lava

Canyon

Creek

Palisades Creek

Basalt

Canyon

Creek

Espejo Creek

C oma nche Creek

T a a n er C

n

o n y C r ee k

n

0 3 Kilometers

Area of

Fig. 2

Cardenas

Creek

A

B

Figure 1. Maps showing the location of study area. A, Location 

map of study area within Grand Canyon National Park, Ariz. B, 

Location of Palisades gully network in eastern Grand Canyon 

National Park, Ariz.
 3

•

•

66

66. 1

222300 222400 222500

569500 569600 569700 569800

0 5 25 0 100 Meters

•

A

B

C

D E

F

VOLUME BOUNDARY

GULLY THALWEG

CROSS SECTIONS

GCMRC RIVER MILEAGE

PROFILE ENDPOINTS

•

•

• •

•

Figure 2. Aerial photograph taken in May 2002 showing the Palisades gully network. Colorado River discharge is approximately 226 

m3/s and flow is from top to bottom of the photograph. Location is shown on figure 1.

Physical Setting 3
4 Aggradation and Degradation of the Palisades Gully Network, 1996 to 2005

A

B

Figure 3. Photographs of the Palisades gully network taken 

on November 17, 2004. A, The south gully as viewed toward the 

playa catchment area. The Cardenas Basalt and a talus slope 

in background form the distal margin of the catchment area. B, 

The unvegetated playa catchment at the eastern margin of the 

Palisades area as viewed to the north. Photographs by David 

Topping, U.S. Geological Survey. 

At topographic levels adjacent to the river, separation 

and reattachment bars are deposited in a large eddy (Schmidt 

and Graf, 1990). The reattachment bar is located downstream 

from the drainage network and is exposed at lower flows 

(fig. 2). Historic oblique and aerial photographs of the area 

show that these sand deposits were considerably larger in the 

predam era (Grams and Schmidt, 1999). The upper terraces 

at the site were interpreted by Hereford (1996) to have been 

deposited in overbank channels by flows in excess of 2,700 

m3

/s. Driftwood elevation surveys and sedimentological 

analyses suggest the existence of an expansive eddy with 

upstream-directed flow during floods of 2,700 m3/s or greater 

(Draut and others, 2005).

The drainage network consists of two adjacent gullies, 

with numerous subsidiary channels (fig. 2). The local catchment is large (about 2 ha) and drains from the playa-dune 

complex on top of the highest terrace and from the southern 

margin of the Palisades debris fan (Hereford, 1996; Pederson 

and others, 2003). Terrace incision appears to have begun 

sometime after 1890; erosion increased dramatically between 

1973 and 1984 (Hereford and others, 1993). By 1980, the 

drainage network extended across the dunes to the Colorado 

River (Thompson and Potochnik, 2000). 

The two primary gullies in the network are informally 

named north and south, respectively, following the convention of Pederson and others (2003). The north gully is the 

shorter and steeper of the two gullies (fig. 4). As of May 2005, 

the north gully mouth debouched to the Colorado River at an 

elevation reached by a flow of about 800 m3

/s. The south gully 

was incised more deeply and entered the river at an elevation 

reached by a flow of about 300 m3/s. The north gully was less 

than 0.75 m deep along its entire length, whereas the south gully 

had better defined walls and was 1.0−1.5 m deep along much 

of its length (fig. 5). The two gullies dropped 5.2 m and 5.7 m 

over lengths of 103 m and 212 m (0.051 and 0.027 slope gradient), respectively. Both gullies have been the focus of remedial 

stabilization efforts by the National Park Service; approximately 

80 erosion-control structures composed of rock and brush check 

dams were built in 1995 from the head of the catchment area to 

the junction with the Colorado River (Leap and Coder, 1995). 

The check dams were periodically maintained or rebuilt into 

rock linings to armor the channel and banks in February 1997, 

February 1998, October 2000, April 2000, March 2003, March 

2004, and March 2005 (Dierker and Leap, 2006). 

Methods

Topographic changes were measured by field survey with 

electronic (optical) total stations. The mapping was focused 

on the area between the edge of the river and the playa area 

to an elevation reached by flows of about 4,500 m3

/s (table 

1). In general, field surveys were conducted by collecting 

ground points along break lines to define the edges and bottom 

thalweg of each gully. During the pre- and post-2004 HFE 

surveys, other areas were covered with individual points so that 

regular point spacing encompassed the entire site. Because 

of logistical constraints, the May 13, 2005, survey focused 

only on the gullies. The point density required for change 

detection depends on gully complexity. As a result, as many as 

1,500 ground points were collected during each survey. This 

typically corresponded to a point density of one point per 3–5 

m2

 for the entire site, with a greater density of one point per 

0.75 m2 concentrated in the gullies. The point data accuracy 

is on the order of +0.1 m horizontally and +0.05 m vertically. 

Survey accuracy in the field was maintained by horizontal and 

vertical checks of positional error between known reference 

points in the Grand Canyon Monitoring and Research Center’s 
 5

control network, an Arizona State Plane Coordinate System, entails visually selecting points in the middle of the channel 

1983, Arizona Central Zone (0202) grid. Previous surveys to represent the centerline.

collected by other researchers were also adjusted to this 

common datum. The historical surveys differ in the extent 

and types of data collected, varying from strictly thalweg 

profiles to complete topographic surveys of varying coverage Results

(table 1).

Digital elevation models (DEMs) were created from 

surveys where survey extent allowed using surface modeling Changes Detected as a Result of the 2004 High- software (fig. 5). The DEMs were used to calculate volume Flow Experiment changes and to delineate a channel centerline along equally 

spaced 0.2-m distances in the south gully mouth between the The 2004 HFE considerably modified the Palisades gully 566 and 1,274 m3

/s stage elevations. However, it is difficult network by depositing sediment at lower nearshore elevations, to account for channel sinuosity with this method, and eleva- infilling the south gully mouth, and eroding the lowermost tion errors are introduced with increasing gully length and downstream terrace margin. The north gully was largely convexity. Pederson and others (2003) developed a tech- unaffected by the 2004 event because the inundation depth at 

nique, which was adopted by this study, to compare longi- the gully mouth was less than 0.40 m (fig. 4). In contrast, the 

tudinal gully profiles by normalizing points collected along south gully was inundated to a maximum water depth of about 

the gully thalweg between two fixed endpoints. The endpoint 1.75 m. 

locations are shown in figures 2 and 4. Neither centerline Infilling of the south gully resulted in deposition of 24.7 

method nor the normalized alternative method is “noise m3

 of fine-grained sediment (table 2). Changes along the 

free,” and considerable variation is introduced to the profile length of the lower reach of the south gully (between approxidepending on how the check dams and thalweg were defined mately 566 and 1161 m3

/s stage elevation) are shown in figure 

and surveyed by different researchers. The centerline method 6. The depth of fill was greatest at or near the gully mouth. 

is less subjective than the normalized alternative, which The lowermost knickpoint, which was about 0.4 m high and 

0 20 40 60 80 100 120 140 160 180 200 220

794

795

796

797

798

799

800

801

802

1,161 m3/s

227 m3/s

SOUTH GULLY

NORTH GULLY

DISTANCE FROM ARBITRARY DATUM, IN METERS

ELEVATION, IN METERS

LOCATION OF 

CENTERLINE PROFILE

Figure 4. Longitudinal gully profiles showing the stage elevations reached by flows of 227 m3/s and 1,161 m3/s and the mouth area 

discussed in the text; the symbols indicate normalized profile endpoint locations. Note that the 1,161 m3

/s discharge of the 2004 highflow experiment was insufficient to inundate the north gully mouth.

Results 5
6 Aggradation and Degradation of the Palisades Gully Network, 1996 to 2005

capped by a 0.2-m-thick layer of silt and clay, was buried by 

nearly 1 m of new sediment (fig. 7A). Erosion and bank retreat 

at the southeast margin of the gully wall, near the edge of the 

lowermost terrace, resulted in widening of the gully mouth 

(fig. 7B). About 12.0 m3 of material was eroded from these 

areas, but the net change was positive (table 2). Infilling of 

the south gully was substantially greater in 2004 than infilling 

observed in 1996 because the gully mouth was considerably 

larger in 2004 (Increased accommodation space is discussed in 

a following section.). 

South Gully Changes between December 2004 

and May 2005

The sediment mass deposited in the south gully mouth 

was still largely intact 6 mo after the 2004 HFE; however, 

some minor reworking of the gully bottom was detected. 

Between December 2004 and May 2005, 3 mo of large daily 

release fluctuations—425 m3/s fluctuations with daily peaks 

of 566 m3

/s—occurred. These dam releases had little effect 

on the mouth of the south gully (fig. 6). However, 8.4 m3 of 

scour in the lower reach of the south gully, coupled with 3.8 

m3 of redeposition, resulted in a net erosion of 4.6 m3 of the 

flood-emplaced sediment (table 2). There was little evidence 

of substantial incision and no evidence to suggest that water 

had been flowing in the gullies during the interval between 

surveys. The weather station on river left in the Palisades area 

indicates that the largest daily precipitation amount, which 

occurred on March 24, 2005, was about 13.7 mm (Draut 

and Rubin, 2006)an amount we speculate did not result in 

surface flow in the drainage network. Therefore, we presume 

the erosion was likely a result of wind deflation rather than 

renewed gullying. Wind velocities capable of entraining fine 

sediment at the site were recorded in late December 2004, 

early January 2005, and during the 2005 spring months (Draut 

and Rubin, 2005, 2006). 

Comparison of the 1996 Controlled Flood and the 

2004 High-Flow Experiment

The channel centerline method was used to compare the 

effects of the 1996 controlled flood with those of the 2004 

HFE, because detailed thalweg profiles were not measured 

in 1996 (table 1). In order to directly compare a longitudinal 

profile in the south gully mouth, the centerline values interpolated from the DEMs were subtracted from the pre-1996 flood 

values, which was arbitrarily defined as the baseline condition (fig. 8). The points were then averaged to produce a time 

series of base-level change within the gully mouth (fig. 9).

Deposition in the south gully as a result of the 2004 HFE 

was nearly two times greater than that resulting from the 1996 

controlled flood (table 2), even though the peak stage reached 

by the lower magnitude 2004 HFE was about 0.20 m lower in 

elevation. For the south gully, the average gully bottom elevaTable 1. Topographic surveys conducted at the Palisades drainage network.

Survey Date Source Survey Description1 Profile Point Density2

(pts/m)

2-17-1996 Yeatts, 1996 Site topography up to 1,700 m3

/s NC

5-12-1996 Yeatts, 1996 Site topography up to 1,700 m3

/s NC

4-22-1997 Yeatts, 1998 Site topography up to 1,700 m3

/s NC

2-28-1998 Grand Canyon National Park, K. Kohl, U.S. 

Geological Survey, 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

1-6-2002 Pederson and others, 2003 Thalweg profiles and check dams 0.55

9-27-2002 Pederson and others, 2003 Thalweg profiles and check dams 1.02

11-11-2003 K. Brown, U.S. Geological Survey, written 

commun., 2006

Thalweg profiles 0.37

5-12-2004 Draut and others, 2005 Thalweg profiles 0.39 

11-20-2004 This study Site topography up to 4,500 m3

/s 0.52

12-10-2004 This study Site topography up to 4,500 m3

/s 0.42

5-13-2005 This study Site topography up to 4,500 m3/s 0.43

1

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)

2

NC denotes that the data were not collected
Results 7

Figure 5. Palisades drainage network topography constructed from the point data collected on November 20, 2004.

Table 2. Volume of sediment scoured and filled at the south gully.

Survey Dates Comparison interval 

(Days)

Scour (m3) Fill (m3) Net change (m3)

2-17-1996 to 5-12-1996 (1996 Controlled 

Flood)

85 6.5 10.0 3.5

10-07-1999 to 11-20-04 1,891 –66.5 2.7 –63.8

11-20-2004 to 12-10-2004 

(2004 High-Flow Experiment)

20 –12.0 24.7 12.7

12-10-2004 to 5-13-2005 154 –8.4 3.8 –4.6

2-17-1996 to 12-10-2004 3,216 –54.8 2.1 –52.7

ELEVATION, IN METERS

METERS
8 Aggradation and Degradation of the Palisades Gully Network, 1996 to 2005

0 5 10 15 20 25 30 35 40 45 50 55 60 65

794

795

796

797

798

FEB. 1996

MAY 1996

NOV. 2004

DEC. 2004

MAY 2005

566 m3/s

1,700 m3/s

1,161 m3/s

DISTANCE FROM ARBITRARY DATUM, IN METERS

ELEVATION, IN METERS

INTACT 

CHECK DAMS

FAILED 

CHECK DAMS

CLAY LENS

KNICKPOINT

Figure 6. Pre- and post-flood centerline longitudinal profiles of the south gully mouth. The gray shaded area represents infilling of the 

gully mouth by the 2004 high-flow experiment (HFE). Variation in the longitudinal profile at elevations higher than those reached by the 

experimental flows is possibly the result of remediation efforts between 1997 and 2004 but also may represent inaccuracies in centerline 

positioning.

12

Figure 6. Changes in thalweg elevation of the south arroyo. Distances along the thalweg are 

approximate because the thalweg shifted laterally in 2002. The gray shaded area represents infilling of 

the arroyo mouth by the 2004 high-flow experiment (HFE). Note that erosion had entirely removed as 

many as six checkdams prior to the 2004 HFE. 

Figure 7. The south arroyo mouth, viewed from the terminus at the Colorado River. A, The clay lens 

knick point as it appeared on November 20, 2004. B, Deposition in the arroyo bottom and erosion of the 

southern margin of the arroyo wall. Photographs provided by Amy Draut, U.S. Geological Survey. 

A B

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Distance along an arbitrary datum (m)

794

795

796

797

798

Elevation (m)

Feb. 1996

May 1996

Nov. 2004

Dec. 2004

May 2005

566 m3/s

1,700 m3/s

checkdams clay lens

nickpoint

1,161 m3/s

B

Figure 7. The south gully mouth viewed from the terminus at the Colorado River. A, The clay lens knickpoint as it appeared on 

November 20, 2004. B, Deposition in the gully bottom and erosion of the southern margin of the gully wall. Photographs by Amy Draut, 

U.S. Geological Survey.
 9

tion increase along the channel centerline following the 1996 

controlled flood was 0.16 m compared to 0.34 m following the 

2004 HFE (fig. 8). The sediment deposited in the south gully 

mouth by the 1996 controlled flood was still largely present 

in May 1999, after which the gully was incised 0.5 m in the 

4-yr period before the 2004 HFE (fig. 9). About 66.5 m3 of 

material was scoured from the 30 m length of the south gully 

mouth area (table 2), and four check dams present in the 1990s 

were entirely removed (fig. 6). As a result of renewed gullying 

between 1999 and 2004, the 2004 HFE flood peak extended 

about 10 m farther into the gully (fig. 8). Thus, the marked 

difference in depositional volume in the south gully mouth 

is likely the result of greater accommodation space available 

for deposition in 2004, rather than the result of differences 

in sediment supply or flood duration between the two flood 

experiments. 

Changes above the Elevations Reached by 

Experimental High Dam Releases

Erosional patterns and knickpoint retreat for a 7-yr period 

are shown in figure 10. The downstream endpoints are located 

in each gully mouth and the upstream endpoints are located 

at the eastern edge of the playa-like catchment area (fig. 2). 

Interpreting the results is complicated by profile point spacing 

(table 1) and the removal or maintenance of erosion-control 

structures between topographic surveys (Dierker and Leap, 

2006). This situation introduces considerable noise into the 

longitudinal profile because of small elevation changes (about 

0.10–0.20 m), which make it difficult to track localized erosion resulting from knickpoint retreat and breached or flanked 

erosion-control structures (fig. 10). Nonetheless, changes in 

profile gradient are useful for tracking longer term incision 

rates. 

The gradient in both gullies steepened between February 

1998 and February 2002 (table 3). In the subsequent 8 mo, 

between February and October 2002, there was a substantial 

erosional event documented by Pederson and others (2003). 

A new knickpoint with a clay lens cap developed in the south 

gully near the mouth, and a previously existing knickpoint 

advanced up the gully about 27 m (figs. 7A and 10B). The 

gradient of the south gully increased from 0.037 m in January 

2002 to 0.41 m in late September 2002. In the higher gradient 

north gully, the development of two small knickpoints resulted 

in a slight steepening of the gradient (fig. 10A).

The 2002 gullying in the lower gully reaches may have 

occurred during one storm. An unusual frontal system from 

the Pacific produced widespread rain and resulted in tributary 

debris flows to the Colorado River between the mouth of the 

Little Colorado River and Phantom Ranch on September 7, 

2002 (Webb, 2003). On or around this date, flooding in nearby 

Lava Canyon and Carbon Creek caused hydraulic and geomorphic changes that increased the water-surface elevation of the 

pool upstream from Lava Canyon Rapid by 0.3−0.5 m (Hazel 

and others, 2006).

10 15 20 25 30 35 40 45 50

-1.0

-0.5

0.0

0.5

1.0

MAY 1996

NOV. 2004

DEC. 2004

MAY 2005

CHANGE IN GULLY CENTERLINE

ELEVATION, IN METERS

DISTANCE FROM ARBITRARY DATUM, IN METERS

1996 

CONTROLLED 

FLOOD PEAK

CLAY LENS

KNICKPOINT

GULLY 

MOUTH

2004 HFE

PEAK

Figure 8. Pre- and post-flood changes along the centerline longitudinal profile of the south gully. Changes in gully elevation are with 

reference to a common datum (the solid horizontal line) defined by the pre-1996 flood condition. The gray shaded area represents 

infilling of the gully mouth by the 1996 controlled flood and 2004 high-flow experiment (HFE). Note that the 2004 HFE extended into the 

gully mouth about 10 m farther from the Colorado River than did the higher magnitude 1996 controlled flood.

Results 9
10 Aggradation and Degradation of the Palisades Gully Network, 1996 to 2005

-0.75

-0.5

-0.25

0

0.25

0.5

0.75

1996 1998 2000 2002 2004

YEAR

2004 HIGH-FLOW EXPERIMENT

1996 CONTROLLED FLOOD

CHANGE IN AVERAGE CENTERLINE

ELEVATION, IN METERS

Figure 9. South gully mouth 

time series constructed 

from the average centerline 

elevation data in figure 8. The 

February 1996 elevation equals 

0. Note that even though the 

deposition was two times 

greater in 2004 compared to 

1996, the base level of the gully 

mouth was not restored to the 

1996 pre-flood condition.

During the 2-yr period following the 2002 erosional the gullies draining the Palisades terraces by the 2004 HFE. 

event, it appears that both north and south gullies were When possible, the results were compared to previous studies 

relatively stable. Deposition as a result of the 2004 HFE of the site, particularly research associated with the 1996 coneffectively lessened the gradient of the south gully from 0.38 trolled flood. The 2004 HFE inundated the lowermost terrace 

to 0.33 m, whereas the north gully was largely unaffected of the Palisades gully network and deposited a substantial 

(table 3). The May 2005 survey found limited net change in volume (24.7 m3

) of fine-grained sediment in the mouth of the 

the upper reaches, suggesting that little if any aeolian infill- south gully; however, the north gully was largely unaffected. 

ing occurred as a result of the presence of nearby river-level The amount of sediment deposited in the south gully 

sandbars deposited by the 2004 HFE. mouth by the 2004 HFE was nearly two times larger than the 

Although profile analyses are instructive for examination 1996 controlled flood (table 2). Compared to 1996, the south 

of gully incision, other measures are needed to examine gully gully had eroded to a greater depth before the 2004 HFE, 

widening that results from channel avulsion or breaching and and, as a result, the south gully had a larger accommodation 

flanking of check dams. In order to examine possible lateral space available for deposition during the 2004 event. Thus, 

erosion, the sidewalls of the arroyos and major tributaries were the differences in the volume of sediment deposited by the examined by this study. Specifically, cross sections established two floods did not directly stem from differences in sediment by a 1998 National Park Service survey were compared to supply or flood duration but rather greater space available for cross-sectional data generated during November 2004 and May deposition in 2004. Additionally, the 2004 HFE deposit in the 2005 for the same locations (fig. 11). The results suggest that enlarged south gully mouth was largely retained in the 6 mo the upper reaches of both the north gully and the south gully and following the event (figs. 6 and 8). Infilling resulting from the major tributaries were largely the same width and depth in 2004 2004 HFE also affected the gradient of the gully. Compared as they were in 1998. It is unknown whether the sidewall stabil- to measurements taken in May 2005, the gradient of the south ity measured between 1998 and 2004 was the result of remedia- gully was less steep than it had been in February 1998, while tion efforts such as armoring the sides of the gullies with rocks. the gradient of the north gully, in contrast, was more steep Field observations during this study and repeat photography by because it was unaffected by either flood. Pederson and others (2003, 2006) indicate continued breaching The elevation of the gully mouth forms the effective base and flanking of erosion-control structures from surface flow at level for the drainage network. In both the south and the north other locations in the drainage network. gullies, most of the erosion was concentrated in the lowermost reaches near the gully mouths. Because infilling of gully 

mouths by experimental flows can establish a new higher 

Discussion and Conclusions effective base level, this may be an important finding. Hereford and others (1993) hypothesized that gully incision rates 

This study was largely focused on documenting the increased in the postdam era because gullies were eroding to 

amount and retention of sediment deposited in the mouths of the new, lower effective base level of the postdam Colorado 
 11

Figure 10. Normalized 

longitudinal profiles. A, The 

3.9-m drop of the north gully 

over a length of 85 m. B, The 

4-m drop of the south gully 

over a length of 122 m. Data 

from October 2002, May 2004, 

and December 2004 are not 

shown for brevity. Small arrows 

indicate check dam locations 

surveyed by the National Park 

Service in 1998. The profile 

endpoints are shown in figure 2.

Table 3. Lower and middle section gully slope gradients, February 1998–May 2005.

Date North gully South gully

February 1998 .046 .035

February 2002 .047 .037

September 2002 .047 .041

November 2003 .047 .038

November 2004 .048 .038

December 2004 .046 .033

May 2005 .048 .033

794

795

796

797

798

799

800

JAN. 1998

JAN. 2002

NOV. 2003

NOV. 2004

MAY 2005

1,161 m3/s

A

ELEVATION, IN METERS

NORMALIZED STATION (%)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

794

795

796

797

798

799

800

801

1,161 m3/s

FEB. 2002

NOV. 2003

NOV. 2004

MAY 2005

B

ELEVATION, IN METERS

JAN. 1998

NORMALIZED STATION (%)

2002 KNICKPOINT 

DEVELOPMENT

CLAY LENS 

KNICKPOINT

801

Discussion and Conclusions 11
12 Aggradation and Degradation of the Palisades Gully Network, 1996 to 2005

Figure 11. Cross sections established by the National Park Service in January 1998. A, The lower south gully. B, The middle of the 

south gully. C, The upper south gully above the confluence with the first major tributary. D, The lower south tributary. E, The upper south 

tributary. F, The middle of the north gully. Data from December 2004 are not shown. There was no change in the upper part of the gullies 

in the 19 days between surveys. Note that all cross sections are above the elevation reached by the 2004 high-flow experiment. Cross 

sections are viewed in a down-gully direction. Locations are shown in figure 2.

01234567

DISTANCE BETWEEN ENDPOINTS, IN METERS

798

799

800

801

ELEVATION, IN METERS

E

JAN. 1998

NOV. 2004

MAY 2005

012345

DISTANCE BETWEEN ENDPOINTS, IN METERS

798

799

800

801

ELEVATION, IN METERS

D

JAN. 1998

NOV. 2004

MAY 2005

01234567

DISTANCE BETWEEN ENDPOINTS, IN METERS

798

799

800

801

ELEVATION, IN METERS

F

JAN. 1998

NOV. 2004

MAY 2005

012345 6

DISTANCE BETWEEN ENDPOINTS, IN METERS

798

799

800

801

ELEVATION, IN METERS

C

JAN. 1998

NOV. 2004

MAY 2005

0 123456789 10

DISTANCE BETWEEN ENDPOINTS, IN METERS

798

799

800

801

E LE VATION, IN ME TE RS

B

JAN. 1998

NOV. 2004

MAY 2005

012345 6

DISTANCE BE TWEEN E NDPOINTS, IN ME TERS

797

798

799

800

E LE VATION, IN ME TE RS

A

JAN. 1998

NOV. 2004

MAY 2005
References 13

River shoreline deposits. Thompson and Potochnik (2000) 

revisited the base-level concept and proposed that deposition 

in gully mouths may provide a temporary base-level effect, 

resulting in reduced erosion upstream from gully mouths as 

well as providing a source of sand for aeolian deposition. 

This study found no discernible change in the upper drainage 

network of the two gullies at Palisades; however, the absence 

of noticeable change in the upper reaches could not be definitively linked to short-term base-level increases in the south 

gully mouth. Given the infrequency of high-flow events in the 

postdam era, any change in effective base level resulting from 

gully infilling is likely to be temporary. A local rainfall event 

will likely result in runoff sufficient to remove gully infilling, 

which is what occurred as the result of the 2002 storm discussed earlier. Nonetheless, despite the changes documented 

in the lower reach of the south gully, the uppermost reaches 

of both the north and south gullies appeared to be relatively 

stable, presenting little or no evidence of incision between 

1998 and 2005. 

Unfortunately, it was not possible to determine from this 

study whether or not gully mouth deposition or erosion-control 

structures were responsible for the channel stabilization. Differences in the types of data collected over time and changes 

in erosion-mitigation efforts that occurred between topographic surveys precluded accurate analysis of changes that 

may have occurred in the uppermost reaches of the gullies. To 

discern cause-and-effect relationship in the future, it is imperative that the same types of data be collected between surveys, 

maintenance of check dams be withheld, and more detailed 

local weather data be obtained. Future efforts to quantify and 

understand gully erosion in Grand Canyon National Park 

would be greatly enhanced by high-resolution survey mapping that encompasses the entire length of gully and catchment 

area, and accurately depicts gully width and depth. 

Acknowledgements

This study was sponsored by the U.S. Geological Survey 

and Bureau of Reclamation through the Grand Canyon Monitoring and Research Center. We thank Amber Gaul, Sarah 

Goeking, Eric Kellerup, Keith Kohl, Meagan Polino, Albert 

Reichert, Tom Sabol, and Bob Tusso for their valued field 

assistance. Thanks also to Mike Breedlove for GIS support. 

Reviews provided by Joel Pederson and two other anonymous 

reviewers greatly improved the quality of this report. 

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Hazel and others—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—Open-File Report 2008–1264