Vol. 9, No. 4 April 1999

GSA TODAY

A Publication of the Geological Society of America

ABSTRACT

Erosion of sandbars and beaches in

the Grand Canyon National Park downstream from Glen Canyon Dam has

become a major problem that needs to

be addressed. Geomorphic and geologic

mapping provide a link between sandbar elevations and discharge measurements. This link allows an estimate of

discharges that will deposit sand far

enough above normal high water to

prevent frequent depletions by erosion.

The sand is needed to protect habitats

and archaeological sites and to maintain beaches used by recreationists. It is

proposed that when the Little Colorado

is in flood, discharge at Glen Canyon

Dam be increased to bring the total discharge to the desired high value. Analysis of the flow records show that such

opportunities are presented on the average once in eight years, suggesting that

the proposal has a reasonable chance of

success.

INTRODUCTION

The Colorado River in the Grand

Canyon section in Arizona once fluctuated

greatly in its flow. Year-to-year and seasonto-season variability was large. Peak discharges ranged from 300 000 cfs (cubic

feet per second) to 19 200 cfs, a difference

of 16 times. The amount of sediment

transported as suspended load was very

large. Measurements carried out at the

Grand Canyon for the period December

1940 to June 1941 show that, at 50 000

cfs, about 2 000 000 tons were moved per

day during the rising stage of the flood,1

and 500 000 tons during the falling stage,

whereas almost 5 000 000 tons per day

were moved during the peak of the flood

Floods and Sandbars in the Grand Canyon

Ivo Lucchitta, 6969 Snowbowl View Circle,

Flagstaff, AZ 86001

Luna B. Leopold, 400 Vermont Avenue,

Berkeley, CA 94707

Glen Canyon Dam at high discharge during the June 1983 flood. The dam is 710 ft (216 m) high. The

four jets of water issuing from near the lower right corner of the dam are from the outlet works.

Releases from the right spillway are hidden by the cloud of mist and spray near the lower left corner of

the dam. The left spillway, whose exit is visible a short distance downstream from the outlet-work jets,

was inactive when the photo was taken. Discharge from the powerplant is below river level and not

visible. Photo courtesy of David L. Wegner

Grand Canyon continued on p. 2

D

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1999

INSIDE

• Call for Papers 

— Page D1

• Electronic Abstract 

Submission 

— Page D12

• Registration 

Issue — June 

GSA Today

1Sediment transported during the rising

stage of a flood is much greater than that

transported during the falling stage (Leopold

and Maddock, 1953).
2 GSA TODAY, April 1999

Floods and Sandbars in the 

Grand Canyon ....................... 1

In Memoriam .......................... 2

Memorial Preprints ..................... 2

Environment Matters ................... 3

SAGE Remarks ......................... 8

Farouk El-Baz Award . . . . . . . . . . . . . . . . . . . 10

New Service for Bulletin and 

Geology Authors . . . . . . . . . . . . . . . . . . . . . . . 10

Washington Report . . . . . . . . . . . . . . . . . . . . 11

Cordilleran Meeting Field Trips . . . . . . . . . 12

1999 Annual Meeting Call for Papers . . . D1

Letter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Environmental & Engineering Geoscience

Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Bulletin and Geology Contents . . . . . . . . . . 18

GSAF Update . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Future GSA Meetings . . . . . . . . . . . . . . . . . . 20 

1999 GeoVentures . . . . . . . . . . . . . . . . . . . . . 21

Calendar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Classifieds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

IN THIS ISSUE GSA TODAY April

Vol. 9, No. 4 1999

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Printed in U.S.A. using pure soy inks.

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at ~130 000 cfs (Leopold and Maddock,

1953).

The closure of Glen Canyon Dam in

1963 wrought immense changes in the

river. The high peaks were eliminated and

the maximum controllable discharge—

through power-plant and outlet works—is

only ~45 000 cfs (1274 m3/s). The sediment, so characteristic of the river, is now

deposited in the reservoir behind the dam,

and the releases are clean and cold. All

this materially affected the riparian zone2

in the Grand Canyon, bringing about

changes in erosion, vegetation, and the

biotic communities (Johnson, 1991;

Stephens and Shoemaker, 1987; Stevens et

al., 1995, 1997; Webb, 1996). The annual

peak discharges now are usually in the

range of 25 000 to 35 000 cfs. Only five

times in the 35 years since dam closure

has the peak flow in the Grand Canyon

equaled or exceeded 45 000 cfs. Such discharges come about when water going

over the dam spillways is added to the

maximum discharge through power-plant

and outlet works.

The curtailment of sediment passage

in the canyon has resulted in little replenishment of the sandbars, on which the

maintenance of the original riparian community depended. The release of water

In Memoriam

Richard J. Anderson

Dublin, Ohio

February 5, 1999

Peter J. Coney

Tucson, Arizona

February 20, 1999

Jesse L. Dally

Houston, Texas

February 7, 1999

Julian R. Goldsmith

Chicago, Illinois

January 24, 1999

Robert M. Hutchinson

Golden, Colorado

Terry W. Offield

Reston, Virginia

February 5, 1999

Charles E. Sears

Hampton, Virginia

July 8, 1998

Memorial Preprints

The following memorial preprints are now available, free of charge, by writing

to GSA, P.O. Box 9140, Boulder, CO 80301-9140.

Charles Banks Belt, Jr.

Edward S. Belt

Ralph J. Bernhagen

Michael C. Hansen, Thomas M. Berg

Wallace Woodrow Hagan

Martin C. Noger, James C. Cobb,

Elizabeth Wade Hall

Wilson M. Laird

F. D. Holland, Jr.

Robert F. Walters

Daniel F. Merriam, Robert D. Cowdery

Quido Záruba

Jaroslav Pasek

Grand Canyon continued from p. 1

Grand Canyon continued on p. 3

ˆ

2The zone along a river that is directly

affected by the river and its fluctuations.
from the dam has been governed by

demand for electricity from the power

plant. This demand fluctuates widely and

quickly, so the discharge in the river has

changed radically hour by hour and day

by day. Not only has the riparian ecosystem been affected, but a decline in recreational use of the canyon has caused

significant commercial loss.

These various effects have become so

serious that scientific teams studying the

issue have recommended various remedies, including the trial release of water

at high controllable discharges to test

whether such discharges were sufficient to

put in motion sand stored in the bed and

in side draws and perhaps build back at

least some of the sandbars. In 1996, a “test

flood” consisted of the release of 45 000

cfs for a week; in 1997, a discharge of

31 000 cfs for 48 h was designed to transfer from channel bottom to channel margins at least some of the 2.2 million tons

of sand and 2.7 million tons of silt and

clay that had been delivered to the Colorado River by a sequence of floods on the

Paria River (Kaplinski et al., 1998). Both

flows deposited sand, to the jubilation of

all concerned, but an important part of

the deposited volume was subsequently

washed away (Kaplinski et al., 1998). Several floods on the Little Colorado River in

January and February 1993 brought a large

amount of new sand into the Colorado

What factors determine the success or failure of integrated

scientific efforts? Are these factors scientific themselves?

Social? Cultural? Are they fundamentally dollar-based and

administrative? Will collaboration necessarily yield integrated

approaches and results? Are there things that organizations

can do to enable collaborative efforts among scientists? 

The Geological Society of America, the Ecological Society

of America (ESA), and the U.S. Geological Survey (USGS) organized a workshop, attended by 24 invited participants and 12

organizers, to investigate these questions. The workshop,

“Enhancing Integrated Science” was held November 4–5, 1998,

in Reston, Virginia. The participants represented life sciences,

earth sciences, economics, social sciences, science administration, and institutional and agency leadership. The results of

the workshop illustrate its emergent focus on leadership roles

and include a set of “guiding principles” for integrated science,

a set of recommendations for the USGS, and a set of recommendations for the larger community of science-enabling organizations and institutions. A summary report, including the

results listed above as well as operating definitions, a list of

participants, agenda and discussion topics, candid quotes from

participants, and an action plan for disseminating the results

of the workshop can be found on the USGS Website at:

www.usgs.gov/integrated_science/index.html. 

The process of organizing the workshop became a microcosm—a real-time illustration of the social and cultural progression by which individuals become a functional collective.

A shared vision of the approach to the workshop evolved as

individuals came to rely on one another's perspective of the

problems we would tackle. Shared responsibility for the products of the workshop evolved as we came to trust each other's

contribution during the workshop. These attributes—shared

vision, interdependence, and trust—appear to be essential elements of genuine collaboration. Many of the features of the

systems in which we work (academic, governmental, or otherwise) are inimical to interdependent, collaborative working

relationships. This is not news. Science is a competitive

endeavor. 

How do we get beyond competition? One of the overarching understandings to emerge from the workshop was that

leadership is imperative. If we are to expand the culture of

science to include the collaboration so essential to integrated

scientific approaches, individuals and institutions alike must

embrace the leadership imperative. Only leadership can modify funding structures to remove organizational barriers to collaboration. Only leadership, among the entire scientific community, can expand reward systems to include something

other than individual achievement. Leadership is required to

ensure that “interdisciplinary” does not come to mean “antidisciplinary.” Scientific societies, academic institutions, funding agencies, and federal agencies all share the leadership challenge. Leadership is required to safeguard the pursuit of deep

understandings, rigorous methodologies, and technologies of

individual disciplines without which we cannot achieve useful

understandings of complex natural systems. 

N. Metzger and R. N. Zare (Science, v. 283, p. 642–643)

directly address the leadership imperative by focusing on science policy, “Federal structures . . . strongly militate against

interdisciplinary programs cutting across jurisdictional lines.”

These authors recommend an ambitious interagency approach,

funded by Congress through direct appropriations, to bring

interdisciplinary research “from belief to reality.” In essence,

Metzger and Zare challenged Congress and the federal system

to actively embrace the leadership imperative.

Even as the Metzger and Zare article reached the community, one federal agency moved to the fore with a bold action

to enable interdisciplinary science. In a February 1, 1999, news

release, USGS Director Chip Groat proclaimed his agency's

“commitment to integrating USGS's scientific disciplines. . .”

and announced budget restructuring that includes a line item

for integrated science (see www.geosociety.org/science). This

action signals, at least in the USGS, federal recognition of the

exigencies of organizational leadership to interdisciplinary

science.

GSA, ESA, and the USGS will continue their joint efforts to

enhance integrated science by following through on the

imperatives for organizational leadership we derived through

our workshop last November. Some plans for implementation

in the near future are contained in the summary report cited

above. Long-range planning for collaborative leadership efforts

is in the works. If your organization or institution is interested

in active leadership to enable interdisciplinary science, please

contact us through Cathleen May, (303) 447-2020 ext. 195 or

at cmay@geosociety.org.

GSA TODAY, April 1999 3

ENVIRONMENT MATTERS

Enhancing Integrated Science: 

The Leadership Imperative

Cathleen May, Director, Institute for Environmental Education 

Mary Barber, Ecological Society of America

Linda Stanley, U.S. Geological Survey

Institute for

Environmental

Education

Grand Canyon continued from p. 2

Grand Canyon continued on p. 4
4 GSA TODAY, April 1999

River and built conspicuous beaches

throughout the Grand Canyon. A year

later, these beaches were largely gone

(I. Lucchitta, 1994, personal observation).

This paper offers an additional or

alternative plan to rebuild the sandbars

utilizing floods on the Little Colorado

River. The plan is designed in such a way

that important parts of the deposition are

above the usual moderate peak discharges,

so would be less likely to be eroded away.

THE PROPOSAL

A significant amount of sand is

brought into the canyon from tributaries

entering downstream of

the dam, especially the

Little Colorado River,

which has a large drainage

area, more than 26 000 mi2

(67 340 km2). The Paria,

with an area of 1570 mi2

(4082 km2), is helpful (see

Fig. 1). 

It is proposed that

when the Little Colorado

approaches a significant

flood discharge, the operators at Glen Canyon Dam

open penstocks and outlet

works so that a combination of high flow from the

tributary added to a maximum release from the dam

would produce a discharge

in the Grand Canyon sufficiently high that its effects

may provide on a small

scale what the original

undammed river accomplished in sand

movement and deposition. 

This study uses information and data

from several disciplines to examine the

feasibility of the proposal. Such analysis

involves more than the hydrology and

hydraulics of the river basin but must perforce deal with the geomorphology of the

canyon bottom, which gives an insight

into the long-term functioning of the

river. Then, in order to estimate what a

flood of any size might deposit, it is necessary to analyze in simplified form the various strandlines and terraces, and determine their dates of deposition or renewal.

THE RECENT GEOLOGIC PAST

Extensive and reliably dated Quaternary deposits of the Colorado River in the

Grand Canyon go back about 500 000 yr

(Lucchitta et al., 1995, 1999), and perhaps

about 750 000 yr (Machette and Rosholt,

1991). There have been nine discrete levels

of deposition, datable by modern techniques, that are seen in the canyon varying from 10 to 205 m above the present

river. Older and higher levels undoubtedly

were once present, but have been eroded.

Most deposits consist of remnants

of terraces produced by aggradation and

underlain by far-traveled river gravel

locally intermixed with coarser and more

angular debris of local derivation from

nearby tributary washes. Taken as a whole,

the gravel terraces indicate overall downcutting through the Quaternary, interrupted periodically by aggradation, probably in glacial or late-glacial times.

Cobbles greater than 10 cm are common

in the gravel, indicating considerable

energy and discharge. Tributary rivers and

washes mimicked the activities of the

main river.

The data show that the Colorado

River has cut down an average rate of

~0.4 m/ka for this time interval, within

the 0.4–1.09 m/ka range calculated

(Lucchitta, 1988) for carving the Grand

Canyon as a whole. In reality, this rate

averages intervals of aggradation (negative

downcutting) with intervals of downcutting at a faster, but unknown, rate. An estimate of the rate at which erosion occurs

following a period of aggradation is given

by the most recent deposits.

Near-Stream Terrace Levels

The more recent depositional units

and sandbars of immediate concern are

those that stand at elevations ~10 m or

less above the present river. These deposits

Figure 1. The only tributaries

shown in this location map

are the Paria and the Little

Colorado Rivers, which are

pertinent to this paper. Rivers

are in blue; stream gages are

in orange. The Lees Ferry

gage measures the discharge

from Glen Canyon Dam. The

Cameron gage measures the

discharge of the Little Colorado River, except for the

relatively small flow from a

spring near the confluence

with the Colorado River. The

Grand Canyon gage measures

the combined discharges of

the Colorado, Little Colorado,

and Paria Rivers, plus the

contribution of small tributary

streams within the Grand

Canyon, and minus seepage

and evaporation losses. Oak

Cave and Tsegi Wash, in

green, are the location of

Holocene deposits discussed 

in the text.

Figure 2. Strandlines and terraces in eastern Grand Canyon. Shown schematically are terrace treads and risers, strandlines

marked by driftwood lines, and the vegetation types characteristic of each terrace level.

Grand Canyon continued from p. 3
GSA TODAY, April 1999 5

include the last aggradational terrace, as

well as terraces produced during the current period of erosion, which includes the

decades since Glen Canyon Dam was

built. Geomorphic and geologic studies

(Lucchitta and colleagues) provide a general profile of the units in this range,

shown in Figure 2. 

The archeological unit—the last

aggradational terrace—is given this informal name (Lucchitta et al., 1995) because

prehistoric Puebloan people lived and

farmed on these deposits, leaving abundant evidence of their passage in the form

of sites and artifacts of many kinds (Fairley

et al., 1994). The unit corresponds in a

general way to Hack’s (1942, 1945) Tsegi

Formation, present in washes tributary to

the Colorado River in the southwestern

Colorado Plateau. The relation of this formation to Puebloan artifacts and to the

present channel is similar to those of the

archeological unit, as is the fine grain size.

Ages are comparable.

The archeological unit consists of a

terrace whose base (strath) is below present river level, and the top (tread) about

10 m above it. The unit is composed predominantly of fine to very fine grained

sand. The grain size, excellent rounding,

and common frosting of the sand grains

suggest derivation from Mesozoic eolian

sandstone units abundant on the Colorado Plateau. Far-traveled material is

scarce in most places. The sand grades laterally into coarser colluvium derived from

local slopes and washes, giving the unit a

striped appearance. 

The archeological unit commonly is

modified by wind action and overlain by

resulting eolian deposits. In many places,

these deposits bury Pueblo II sites built on

top of fluvial material. These relations

show that the unit stopped being

deposited 800–750 yr B.P., and has been

incised ~10 m since that time. The oldest

age obtained so far from the unit is

5259–4985 calibrated 14C yr B.P. (Lucchitta

et al., USGS data) from a level ~3 m below

the top of the unit, and at least 7 m above

the base. This suggests that the beginning

of deposition may well have been in early

Holocene—or even late Pleistocene—time.

Pollen associated with the sediments

in Oak Cave, southern Utah (Fig. 1),

records the initiation of a regime of heavy

summer rains, indicated by the expansion

of ponderosa pine, which requires summer

rain, and the stripping of interfluve soil

mantles, indicated by the waning of sagebrush, which requires deep soil (Lucchitta

and others, USGS data). The late Pleistocene to early Holocene age of these sediments either slightly precedes that of the

archaeological unit, or corresponds to

early deposition of this unit. 

These depositional, age, and palynological data are interpreted to indicate

regional stripping of soil mantles, with

accompanying overloading and aggradation of the regional drainage network

resulting in deposition of the archeological unit and correlatives. We prefer the

aggradational origin for the unit (the

grade of the river increased with time) to

the origin proposed by O’Connor et al.

(1994), which invokes slackwater deposition from large floods (the grade remained

constant), for the following reasons,

among others: (1) Deposits correlative

with the archeological unit are regionally

widespread, and not restricted to the Colorado River and its floods. (2) Deposits of

tributaries to the Colorado River are

graded to the top of the unit, indicating

general aggradation of the drainage network. (3) The unit is present in all types of

reaches, not just back-eddy areas downstream from constrictions, where slackwater deposits would be typical.

The end of alluviation and onset of

vigorous downcutting that incised the

archeological unit started about 800 yr

ago; downcutting has occurred at the high

rate of 12.5 m/ka. The significance of

these data is that the last period of major

aggradation by the Colorado River is represented by the archeological unit,

whereas the river has been operating in a

regimen of strong downcutting for

approximately the past 800 yr, continuing

to this day. Glen Canyon dam was built

during a strongly erosive regimen.

Among the levels below the archeological unit are two prominent terraces

traceable along many reaches of the Grand

Canyon. They have been named the

Green Arrowweed and the Silver Arrowweed terraces, respectively (Lucchitta et

Figure 3. Discharge rating

curve, Grand Canyon station.

Many of the deviations from

the curve are due to measurements being taken on the rising or falling stages of a flood.

Figure 4. Photo of beach on the Colorado River produced by the 1993 flood of the Little Colorado

River. The beach is a short distance downstream from the confluence. The beach must have resulted

from the flood on the Little Colorado because no such beaches were present upstream from the confluence, and because the sand contained abundant basaltic detritus. Basalt is common along the course of

the Little Colorado River. One year later, the beaches visible in the photograph were virtually gone.

Grand Canyon continued on p. 6
6 GSA TODAY, April 1999

al., 1995), from the local flora found there

when the studies were carried out (Fig. 2).

All levels below the archeological unit

have been created and refurbished by

floods during the historic period.3 Lines of

flood debris and driftwood are found in

consistent relations to treads and risers of

the terraces, as shown in Figure 2. The

younger (and lower) strandlines of large

driftwood include abundant worked wood

and artifacts such as cans. Plastic objects

are common in the 1983 strandline, but

very rare in the pre-dam 120 000–140 000

cfs strandline. In pre-dam time, beaches

and strandlines produced by lesser floods

tended to be modified or destroyed by the

higher floods, so they cannot be recognized easily. Floods greater than 120 000–

140 000 cfs were rare; the 1884 flood of

300 000 cfs (8490 m3/s)4 is marked locally

by deposits and a strandline composed of

large rotten logs, scarce worked wood, and

a few artifacts that include no plastic

items. The 97 300 cfs (2755 m3/s) flood of

1983, which marks the greatest post-dam

discharge, is represented by a sand terrace

and a drift line composed chiefly of fresh,

relatively small wood and modern artifacts, including abundant plastic items.

The various strandlines were surveyed by

total station (Lucchitta et al., 1995, and

USGS data).

The test flood of 1997 covered only

the Green Arrowweed terrace. The 1996

test flood reportedly just reached the

lower end of the Silver Arrowweed terrace

(various sources, personal communications). Subsequent discharges have

removed a considerable volume of the

sand deposited by the test floods (personal

observations by Lucchitta in 1998; Kaplinski et al., 1998; and Hazel et al., 1999).

Relation of Terraces to Floods

The geomorphic terraces must be

placed within a hydrologic context. This is

best done by relating the levels of the terraces to the discharge rating curve, which

correlates gage height with discharge. The

best gaging station to use for this purpose

is that at Grand Canyon, near Bright

Angel Creek. Measurements by current

meter at this station began in 1921, but

a reliable estimate of 300 000 cfs at Lees

Ferry was also obtained for the flood of

July 8, 1884 (see above).

A plot of the rating curve (Fig. 3)

shows that there has been no progressive

change during the period of record. The

rating curve for Grand Canyon is a reasonable approximation of the action of the

river in the canyon and, combined with

the general cross section provided by geomorphic studies, is used here to represent

the relation of terrace heights to discharge.

From Figure 3, it can be seen that a

discharge of about 55 000 cfs, corresponding to a gage height of 19 to 20 ft (6 m), is

required for water to reach a significant

part of the Silver Arrowweed terrace. However, an appreciable deposit of sand probably will require 65 000 to 70 000 cfs and

a gage height of about 22 ft (7 m). Such a

deposit would be relatively durable

because it would be well away from the

lower step of the terrace, and thus from

the erosive action of the river.

In the 35 years since the dam began

controlling the flow, only six events

equaled or exceeded the 45 000 cfs of the

1996 “test flood” and of these, only two

were significantly higher, 58 400 on

June 15, 1965, and 96 200 cfs on June 29,

1983. All events exceeding 45 000 cfs

required a contribution from the spillway

of the dam.

The Little Colorado River can provide

the 10 000 to 25 000 cfs needed to raise

the maximum controllable outflow from

the dam (45 000 cfs) to the required discharge. The floods of the Little Colorado

in January and February 1993 indicate

that not only is such a contribution possible, but that such floods also bring much

sand into the Grand Canyon. The peak

discharge of these floods was 18 200 cfs at

Cameron, the sixth largest in the period of

record. On March 3, a few weeks after the

peak, the magnificent beaches (Fig. 4) produced by these floods lined the length of

the river from the Little Colorado River

confluence to at least as far as Diamond

Creek, Mile 226 (Lucchitta and colleagues,

personal observations).

ON THE POSSIBILITY OF

RESTOCKING SAND ON THE

BEACHES

In contrast to the test “floods,” which

essentially mined the sand in the channel

of the Colorado River—a depletable

resource—or redistributed sediment

brought in by floods on the Paria—which

are puny compared to the sediment transported by the Colorado River in pre-dam

times—the Little Colorado flood introduced enough new sand to form beaches

the length of the river below the confluence (Fig. 4), in addition to the sand that

remained in the channel or made its way

to Lake Mead. Such floods provide an

opportunity for restocking beaches in the

Grand Canyon downstream from the confluence. 

First, one must achieve a combined

Colorado–Little Colorado River discharge

sufficient to keep sand entrained rather

than allowing it to settle in the channel,

and this discharge must be maintained

long enough to build adequate beaches.

Second, the discharges must attain a high

enough stage to park the sand where it

will not be readily eroded by the river in

its normal modern flows. 

In the period of record, seven days of

the highest peak discharges (> 18 000 cfs)

of the Little Colorado at Cameron

included four that increased the discharge

at Grand Canyon enough to overflow the

Silver Arrowweed terrace. These four

occurrences in the 50 years of measurement means one occurrence about every

12 years.

Alternatively, one may estimate the

possible contribution by counting the

number of days when the daily flow near

Cameron exceeded 10 000 cfs. The daily

flow often is high on two to four successive

days, which would mean little attenuation

by channel storage. In the 50 years of

record, there were six such occurrences, two

of which were not identical with the seven

analyzed above. Thus, there appears to be

the possibility of six useful events in 50

years, or one in eight years on the average. 

The concept is that the flow of the

Little Colorado River be monitored at the

most downstream gaging station at

Cameron, Arizona. When the discharge

reaches a high enough level, the operator

of Glen Canyon Dam would, on short

notice, increase the discharge through

power-plant and outlet works to the maximum capacity of 45 000 cfs. A direct radio

link from gage to dam would make the

opportunity practical. Furthermore,

advance notice of a possible peak at

Cameron could be obtained from careful

observation of the gages on the Little Colorado River upstream of Cameron.

Given the potential for useful events

to occur on average once in eight years, it

is quite within reason that the high flow

of the Little Colorado River could be made

to coincide with a release of 45 000 cfs

from Glen Canyon Dam, resulting in the

deposition of abundant sand at a substantial elevation above present river grade,

within the Silver Arrowweed terrace. In

this position, sand would have considerable durability, probably enough to last

until the next restocking event.

The proposal discussed here pertains

to a geological process—the restocking of

beaches. However, it is well known that

proper managing of the Grand Canyon

involves a complex and often contradictory interplay of geological, biological,

and other considerations (Schmidt et al.,

1998). All of these must be considered

when making management decisions.

Nevertheless, the proposal attempts to

recreate—to the extent possible now that

the dam is built—the sediment transport

and river stage characteristics of the predam river. These are the conditions to

which the Grand Canyon ecosystem was

originally adjusted.

Grand Canyon continued from p. 5

3Defined here as the time interval, starting

in 1884, for which observational information is

available.

4This discharge is based on the observed

level reached by the flood at Lees Ferry—within

the orchard of Lee’s Lonely Dell Ranch. In the

1920s, a profile was surveyed from this level to

the river, allowing determination of the channel cross section during the flood. This, in turn,

led to an evaluation of the flood discharge.
GSA TODAY, April 1999 7

ACKNOWLEDGMENTS

The U.S. Bureau of Reclamation’s

Glen Canyon Environmental Studies program supported Lucchitta’s work in the

Grand Canyon. A U.S. Geological Survey

Gilbert fellowship to T. C. Hanks and

Lucchitta supported the work on the Rainbow Plateau, where Oak Cave is. The

Grand Canyon National Park staff kindly

allowed research to be conducted within

the park. Our colleagues at the U.S. Geological Survey’s Water Resources section in

Flagstaff, especially Frank Brewsaugh and

Bob Hart, supplied us with river data and

other assistance. Mark Caffee and Robert

Finkel of the Center for Accelerator Mass

Spectrometry at Lawrence Livermore

National Laboratory provided the cosmogenic radio-nuclide exposure ages and

radiocarbon ages. Sid Davis and Marie

Davis of Davis2 have concerned themselves with soils and paleoagriculture.

James Hasbargen and Susan Smith of

Northern Arizona University studied the

palynology of the archaeological unit and

equivalents. Our river-guide friends, for

whom nothing is impossible, especially

Steven Bledsoe, Kelly Burke, Brian Dierker,

and Chris Geanious, made the study feasible by providing safe conveyance through

the fastness and perils of the Grand

Canyon. Finally, detailed reviews by L. L.

Ely, Karl Karlstrom, J. L. Pederson, D. J.

Topping, and two anonymous reviewers

helped us to improve the manuscript. To

all these individuals and organizations,

thanks.

REFERENCES CITED

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 Canyon: National Park Service

Cooperative Agreement No. 9AA-40-07920, 276 p.

Hack, J. T., 1942, The changing physical environment

of the Hopi Indians of Arizona: Papers of the Peabody

Museum of American Archaeology and Ethnology, Harvard University, v. 35, no. 1.

Hack, J. T., 1945, Recent geology of the Tsegi Canyon:

Appendix 1 of Archaeological studies in northeast Arizona, in Beals, R. L., et al, eds., Publications in American Archaeology and Ethnology, Volume 44: Berkeley

and Los Angeles, University of California Press.

Hazel, J. E., Kaplinski, M., Parnell, R. A., Manone, M. F.,

and Dale, A., 1999, Topographic and bathymetric

changes at thirty-three long-term study sites: American

Geophysical Union Monograph (in press).

Johnson, R. R., 1991, Historic changes in vegetation

along the Colorado River in the Grand Canyon:

Washington, D.C., Water Science and Technology

Board, Colorado River Ecology and Dam Management,

p. 176–209.

Kaplinski, M., Hazel, J. E., Manone, M. F., Parnell, R. A.,

Dale, A. R., and Topping, D., 1998, Sediment storage

changes following short-duration, high-flow releases

from Glen Canyon Dam, Colorado River in Grand

Canyon: Geological Society of America Abstracts with

Programs, v. 30, no. 6, p. 12.

Leopold, L. B., and Maddock, T., Jr., 1953, The

hydraulic geometry of stream channels and some

physiographic implications: U.S. Geological Survey

Professional Paper 252, 57 p.

Lucchitta, I., 1988, Canyon maker: Plateau, v. 59, 

no. 2, 32 p.

Lucchitta, I., Dehler, C. M., Davis, M. E., Burke, K. J.,

and Basdekas, P. O., 1995, Quaternary geologic map of

the Palisades Creek–Comanche Creek area, eastern

Grand Canyon, Arizona: U.S. Geological Survey OpenFile Report 95-382, 39 p., maps.

Lucchitta, I., Curtis, G. H., Davis, M. E., Davis, S. W.,

and Turrin, B., 1999, Cyclic aggradation and downcutting, fluvial response to volcanic activity, and calibration of soil carbonate stages in the western Grand

Canyon, Arizona: Quaternary Research (in press).

Machette, M. M., and Rosholt, J. N., 1991, Quaternary

geology of the Grand Canyon, in Morrison, R. B., ed.,

Quaternary nonglacial geology: Conterminous U.S.:

Boulder, Colorado, Geological Society of America, Geology of North America, v. K-2, p. 397–406.

O’Connor, J. E., Ely, L. L., Wohl, E. E., Stevens, L. E.,

Melis, T. E., Kale, V. S., and Baker, V. E., 1994, A 4500-

year record of large floods on the Colorado River in the

Grand Canyon, Arizona: Journal of Geology, v. 102,

p. 1–9.

Schmidt, J. C., Webb, R. H., Valdez, R. A., Marzolf,

R. G., and Stevens, L. E., 1998, Science and values in

river restoration in the Grand Canyon: BioScience,

v. 48, no. 9, p. 735–747.

Stephens, H. G., and Shoemaker, E. M., 1987, In the

footsteps of John Wesley Powell: Boulder, Colorado,

Johnson Books, 286 p.

Stevens, L. E., Schmidt, J. C., Ayers, T. J., and Brown,

B. T., 1995, Flow regulation, geomorphology, and

Colorado River marsh development in the Grand

Canyon, Arizona: Ecological Applications, v. 5, no. 4,

p. 1025–1039.

Stevens, L. E., Buck, K. A., Brown, B. T., and Kline, N.

C., 1997, Dam and geomorphological influences on

Colorado River waterbird distribution, Grand Canyon,

Arizona, USA: Regulated Rivers, v. 13, p. 151–169.

Webb, R. H., 1996, Grand Canyon; a century of change;

rephotography of the 1889–1890 Stanton expedition:

Tucson, University of Arizona Press, 290 p.

Manuscript received August 12, 1998; accepted February 8,

1999. ■

P U B L I C A T I O N S N E W S F R O M t h e G S A

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edited by Allison Macfarlane, Rasoul Sorkhabi, Jay Quade, 1999

More than 30 international authors contributed to the first

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The serious professional will appreciate the breadth of this

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