*tris\ i *; ' i yi r* / a i * * f* i

Debns rlows trom tributaries of the 

Colorado River, Grand Canyon

U.S. PBOF1SSIONAI, PAPEH

in cooperation with the U-.S* Bureau of Reclamation
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Debris Flows from Tributaries of the 

Colorado River, Grand Canyon 

National Park, Arizona

By ROBERT H. WEBB, PATRICK T. PRINGLE, and GLENN R. RINK

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1492

Prepared in cooperation with the U. S. Bureau of Reclamation

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1989
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government

Library of Congress Cataloging-in-Publication Data

Webb, Robert H.

Debris flows from tributaries of the Colorado River, Grand Canyon National Park, Arizona / by Robert H. 

Webb, Patrick T. Pringle, and Glenn R. Rink.

p. cm. (U.S. Geological Survey professional paper ; 1492)

"Prepared in cooperation with the U.S. Bureau of Reclamation."

Bibliography: p.

Supt. of Docs, no.: I 19.16:1492

1. Mass-wasting Arizona Grand Canyon. I. Pringle, Patrick T. II. Rink, Glenn R. III. United States. Bureau 

of Reclamation. IV. Title. V. Series.

QE598.5.U6W43 1989 557.3 s dc20 89-600091

[551.3'07'0979132] CIP

For sale by the Books and Open-File Reports Section, U.S. Geological Survey 

Federal Center, Box 25425, Denver, CO 80225
CONTENTS

Page

Abstract- --------------------------- l

Introduction- ------------------------- 1

Acknowledgments- -------------------- 2

Extent of debris flows in the Grand Canyon --------- 3

Hydraulics of debris flows- ------------------ 3

Debris flows in three tributaries of the Colorado River - - - - 5

Methods-------------------------- 5

Lava-Chuar Creek drainage ---------------- 5

Stratigraphy- --------------------- 6

Longitudinal variation in the 1966 debris-flow

deposits ----------------------- 8

Discharge calculation ----------------- 9

Monument Creek drainage ---------------- 9

Stratigraphy---------------------- 10

Longitudinal variation in the 1984 debris-flow

deposits ----------------------- 11

Page

Debris flows in three tributaries of the Colorado RiverContinued 

Monument Creek drainage Continued

Discharge calculations- ---------------- 12

Sediment volume ------------------- 13

Crystal Creek drainage ------------------ 14

Stratigraphy- --------------------- 16

Longitudinal variation in the 1966 debris-flow 

deposits ----------------------- 17

Discharge calculations- ---------------- 19

Similarities and contrasts among the drainages ------ 21

Fluvial events in other drainages --------------- 23

Factors responsible for debris flows- ------------- 24

Hydrologic effects of debris flows on the Colorado River - - - 25 

Summary --------------------------- 26

References cited- ----------------------- 27

ILLUSTRATIONS

Page

FIGURE 1. Map showing areas of study in Grand Canyon National Park, Arizona- -------------------------- 2

2. Map showing the Lava-Chuar Creek drainage at mile 65.5 on the Colorado River --------------------- 6

3. Photographs showing Lava Creek at the confluence with Chuar Creek, 3.8 miles upstream from the Colorado River - - - 7

4. Graph showing stratigraphy of debris-flow deposits in the Lava-Chuar Creek drainage ------------------ 8

5. Photographs showing Lava Creek, 0.2 mile upstream from the confluence with Chuar Creek --------------- 8

6. Graph showing particle-size distributions of the debris flow of 1966 in the Lava-Chuar Creek drainage ---------- 9

7. Map showing the Monument Creek drainage at mile 93.5 on the Colorado River --------------------- 10

8. Photographs showing the mouth of Monument Creek ----------------------------------- 10

9. Graph showing stratigraphy of debris-flow deposits in the Monument Creek drainage ------------------- 12

10. Graph showing particle-size distributions of the debris flow of 1984 in the Monument Creek drainage- ---------- 12

11. Plan map and longitudinal profile for indirect-discharge site B in Monument Creek, 0.5 mile upstream from the Colorado

	River- --------------------------------------------------------- 13

12. Hypothetical hydrograph of the debris flow of 1984 in Monument Creek as suggested by stratigraphic evidence ----- 14

13. Map showing the Crystal Creek drainage at mile 98.2 on the Colorado River ----------------------- 15

14. Graph showing stratigraphy of debris-flow deposits in the Crystal Creek drainage -------------------- 17

15. Photographs showing Dragon Creek, 6.2 miles upstream from the Colorado River -------------------- 18

16. Graph showing particle-size distributions of the debris flow of 1966 in the Crystal Creek drainage ------------ 19

17. Photographs showing Crystal Rapid at the mouth of Crystal Creek ---------------------------- 20

18. Longitudinal profiles for indirect-discharge sites in the Crystal Creek drainage ---------------------- 22

19. Graphs showing relation of characteristics of rapids and the contributing drainage area of the tributaries -------- 25

20. Schematic diagram showing geomorphic features of a typical rapid controlled by debris flows on the Colorado River - - - 26

TABLES

Page

TABLE 1. Selected tributaries of the Colorado River, Grand Canyon National Park -------------------------- 30

2. Indirect-discharge calculation for the debris flow of 1966 on Lava-Chuar Creek, 0.2 mile upstream from the Colorado

River ---------------------------------------------------------- 31

3. Indirect-discharge calculation for the debris flow of 1984 on Monument Creek at Tapeats Alcove, 1.5 miles upstream from

the Colorado River --------------------------------------------------- 31

Hi
IV CONTENTS

Page

TABLE 4. Indirect-discharge calculations for the debris flow of 1984 on Monument Creek at site B, 0.5 mile upstream from the

Colorado River ----------------------------------------------------- 32

5. Indirect-discharge calculation for the debris flow of 1984 on Monument Creek at site C, 0.3 mile upstream from the

Colorado River ----------------------------------------------------- 32

6. Four scenarios of deposition on the Monument Creek debris fan used to calculate volumes of sediment deposited during

the debris flow of 1984 ------------------------------------------------- 33

7. Indirect-discharge calculation for the debris flow of 1966 on Dragon Creek at site E, 5.0 miles upstream from the

Colorado River ----------------------------------------------------- 34

8. Indirect-discharge calculation for the debris flow of 1966 on Dragon Creek at site F, 4.8 miles upstream from the

Colorado River ----------------------------------------------------- 34

9. Indirect-discharge calculations for the debris flow of 1966 on Crystal Creek at site G, 0.9 mile upstream from the

Colorado River ----------------------------------------------------- 35

10. Comparison of discharges calculated at all superelevation sites by the cross-sectional area at the highest superelevation

marks and an average of the upstream and (or) downstream cross-sectional areas ------------------- 35

11. Historic flow events or channel changes in tributaries of the Colorado River in Grand Canyon National Park ------- 36

12. Relation between difficulty rating for rapids and drainage area of the contributing tributaries for 67 rapids on the

Colorado River ----------------------------------------------------- 38

METRIC CONVERSION FACTORS

For readers who prefer to use the metric (International System) units, the conversion factors for 

the inch-pound units used in this report are listed below:

Multiply inch-pound unit

inch (in.)

foot (ft)

square foot (ft 2)

cubic foot (ft 3)

foot per second (ft/s)

cubic foot per second (ft 3/s)

mile (mi)

square mile (mi2)

acre-foot per year (acre-ft/yr)

pound (Ib)

ton

By

25.4

0.3048

0.09294

0.2832

0.3048

0.02832

1.609

2.59

1,233

453.6

0.9072

To obtain metric unit

millimeter (mm)

meter (m)

square meter (m2)

cubic meter (m3)

meter per second (m/s)

cubic meter per second (m3/s)

kilometer (km)

square kilometer (km2)

cubic meter per year (m3/yr)

gram (g)

megagram (Mg)

Sea level: In this report "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD 

of 1929) A geodetic datum derived from a general adjustment of the first-order level nets of both 

the United States and Canada, formerly called "Mean Sea Level of 1929."
DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, 

GRAND CANYON NATIONAL PARK, ARIZONA

By ROBERT H. WEBB, PATRICK T. PRINGLE, and GLENN R. RINK

ABSTRACT

A reconnaissance of 36 tributaries of the Colorado River indicates that 

debris flows are a major process by which sediment is transported to 

the Colorado River in Grand Canyon National Park. Debris flows are 

slurries of sediment and water that have a water content of less than 

about 40 percent by volume. Debris flows occur frequently in arid and 

semiarid regions. Slope failures commonly trigger debris flows, which 

can originate from any rock formation in the Grand Canyon. The largest 

and most frequent flows originate from the Permian Hermit Shale, the 

underlying Esplanade Sandstone of the Supai Group, and other formations of the Permian and Pennsylvanian Supai Group. Debris flows also 

occur in the Cambrian Muav Limestone and underlying Bright Angel 

Shale and the Quaternary basalts in the western Grand Canyon.

Debris-flow frequency and magnitude were studied in detail in the 

Lava-Chuar Creek drainage at Colorado River mile 65.5; in the Monument Creek drainage at mile 93.5; and in the Crystal Creek drainage 

at mile 98.2. Debris flows have reached the Colorado River on an average 

of once every 20 to 30 years in the Lava-Chuar Creek drainage since 

about 1916. Two debris flows have reached the Colorado River in the 

last 25 years in Monument Creek. The Crystal Creek drainage has had 

an average of one debris flow reaching the Colorado River every 50 

years, although the debris flow of 1966 has been the only flow that 

reached the Colorado River since 1900. Debris flows may actually reach 

the Colorado River more frequently in these drainages because evidence 

for all debris flows may not have been preserved in the channel-margin 

stratigraphy.

Discharges were estimated for the peak flow of three debris flows that 

reached the Colorado River. The debris flow of 1966 in the Lava-Chuar 

Creek drainage had an estimated discharge of 4,000 cubic feet per second. The debris flow of 1984 in the Monument Creek drainage had a 

discharge estimated between 3,600 and 4,200 cubic feet per second. The 

debris flow of 1966 in the Crystal Creek drainage had a discharge estimated between 9,200 and 14,000 cubic feet per second. Determination 

of the effective cross-sectional area was a problem in all calculations 

involving superelevations on bends because areas near superelevation 

marks were 1.5 to 3.5 times larger than areas of upstream or downstream cross sections.

Debris flows in the Grand Canyon generally are composed of 10 to 

40 percent sand by weight and may represent a significant source of 

beach-building sand along the Colorado River. The particle-size distributions are very poorly sorted and the largest transported boulders were 

in the Crystal Creek drainage. The large boulders transported into the 

Colorado River by debris flows create or change hydraulic controls 

(rapids); these controls appear to be governed by the magnitude and 

frequency of tributary-flow events and the history of discharges on the 

Colorado River. Reworking of debris fans by the Colorado River creates 

debris bars that constrain the size of eddy systems and forms secondary rapids and riffles below tributary mouths.

INTRODUCTION

Sediment transported from small drainages is a potentially significant contribution to the sediment budget of 

the Colorado River in Grand Canyon National Park, 

Arizona (fig. 1). Little is known about the annual sediment 

yields from these drainages; however, many researchers 

have noted the efficacy of tributaries for moving large 

boulders into the Colorado River, which locally form 

rapids (Dolan and others, 1978; Graf, 1979; Hamblin and 

Rigby, 1968; Kieffer, 1985; Leopold, 1969). Indeed, large 

rapids may be the most obvious geomorphic and hydrologic manifestation of sediment transport from small 

drainages in Grand Canyon National Park.

Estimation of sediment yields from ungaged Colorado 

River tributaries in Grand Canyon National Park is difficult and uncertainties in cited figures are large. Howard 

and Dolan (1981) estimated an average annual sediment 

yield for these tributaries of 2,100 acre-ft/yr by use of a 

sediment-mass balance for the Colorado River. However, 

they estimated the change in storage of sediment in the 

bed of the Colorado River by using an average channel 

width and by assuming that sand covered an average of 

75 percent of the channel bed. Laursen and others (1976) 

estimated an average annual sediment yield of 0.7 acreft/yr of "beach-building sand" on the basis of differences 

in suspended-sediment transport between the gaging 

stations at the Colorado River at Lees Ferry and the 

Colorado River at Grand Canyon. Mass-balance estimates 

of sediment yields contain considerable uncertainty 

because the change in bed storage is unknown.

Sediment yields from these tributaries also could be 

estimated using methodology presented by the Pacific 

Southwest Inter-Agency Committee (1968). This methodology was developed from rangeland monitoring efforts 

on terrain with low to moderate topographic relief. Sediment yields are determined from a quasi-analytical 

procedure that is based on geology, soils, climate, 

drainage-basin characteristics, and channel stability. Use 

of the methodology requires the tacit assumption that 

sediment is transported by Newtonian streamflow. The
DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

method produces a sediment yield per unit area, which 

implies that drainage-basin area is the most important factor influencing sediment yield.

In the study of the tributaries of the Colorado River, 

the key to estimating sediment yield is an understanding 

of the sediment-transport process. A previous flood report 

(Cooley and others, 1977) and recent mapping of alluvial 

deposits in tributary canyons during this project indicate 

that debris flow is the dominant process for sediment 

transport in small drainages in Grand Canyon National 

Park. Debris flows are common in arid and semiarid 

drainages (Blackwelder, 1928); however, their importance 

in supplying sediment to the Colorado River has not been 

previously recognized.

The purpose of this report is to document the extent 

of debris flows in Grand Canyon National Park and the 

occurrence and magnitude of debris flows in three Colorado River tributaries. The effects of these events on the 

mainstem-channel morphology are necessary in understanding sediment transport and hydraulic controls in the 

Colorado River. This study was funded in cooperation with 

the U.S. Bureau of Reclamation as part of a larger study 

entitled "Glen Canyon Environmental Studies."

ACKNOWLEDGMENTS

The authors thank J.T. Brown, M.D. Daggett III, S.L. 

Reneau, and V.A. Yocum for their help with the fieldwork 

and companionship during the river trip. R.M. Turner of 

the U.S. Geological Survey rephotographed historic 

scenes in Monument, Crystal, and Dragon Creeks. R.C. 

Euler of the National Park Service shared his Grand 

Canyon archaeological experiences and provided photographs of the Crystal Creek and Lava-Chuar Creek 

drainages. Hal G. Stevens, formerly of the U.S. Geological 

Survey, generously provided his matched photograph of 

Killers' view of the mouth of Monument Creek. V.A.S. 

McCord and T.P. Harlan of the Laboratory of Tree-Ring 

Research, University of Arizona, examined tree-ring 

specimens that exhibited damage from debris flows. J.D. 

Rogers, Rogers/Pacific Consultants, Lafayette, California, provided published and unpublished manuscripts on 

debris flows and geology of the Grand Canyon. Bryan 

Brown, Kim Crumbo, Larry Stevens, and Mike Yard, 

Colorado River boatmen, shared their experiences with 

Grand Canyon navigation and changes in rapids. Mike 

Walker and Mike Yard provided eyewitness accounts of

EXPLANATION

(so) River miles 

Study area

Roaring 

Twenties CRYSTAL 

CREEK 

DRAINAGE 

(see fig. 13)

LAVA-CHUAR CREEK 

Grand Canyon DRAINAGE (see fig. 2)

National Park

Boundary Lava , Falls L

Rapid

__ . Grand

MONUMENT l_Canyon 

CREEK 

DRAINAGE

(see fig. 7) Ho nee 

Rapid

25 KILOMETERS

FIGURE 1. Areas of study in Grand Canyon National Park, Arizona.
HYDRAULICS OF DEBRIS FLOWS

Grand Canyon debris flows. S.W. Kieffer and T.C. Pierson of the U.S. Geological Survey and S.L. Reneau of the 

University of California at Berkeley critically reviewed 

the manuscript. Jack C. Schmidt and Julia B. Graf, U.S. 

Geological Survey, Tucson, discussed aspects of the 

research and provided a different perspective on the 

hydrologic effects of debris flows on the Colorado River. 

We especially thank Curt Green, Bob Marley, and Tom 

Wise of the U.S. Geological Survey for being excellent 

field assistants and skeptics; we hope to share more field 

seasons with them.

EXTENT OF DEBRIS FLOWS 

IN THE GRAND CANYON

Debris flows are flowing water-based slurries of poorly sorted clay- to boulder-sized particles (Costa, 1984). 

Terms sometimes intended to be synonymous include 

mudflows, debris slides, debris torrents, mud slides, or 

lahars (volcanic debris flows). Debris flows occur in many 

different environments ranging from deserts (Johnson 

and Rodine, 1984) to montane forests (Gallino and Pierson, 1985) and offshore continental shelf slopes (Piper and 

others, 1985). Debris flows tend to form their own channels between levees that are parallel to the flow direction 

when unconfined by an existing channel. These levees are 

composed of boulders which commonly appear to be 

floating in a matrix of gravel, sand, and clay (Costa, 1984; 

Johnson and Rodine, 1984) and have a distinctly different 

morphology from typical alluvial deposits.

Many classification schemes have been proposed for 

coarse-grained sediment flows based on water content 

during transport (Beverage and Culbertson, 1964), characteristics of the resultant alluvial deposits (Smith, 1986; 

Pierson and Scott, 1985), or on assumed rheological 

models of flow dynamics (Postma, 1986). Debris flows 

typically have 15 to 40 percent volumetric water content 

compared with 40 to 80 percent for hyperconcentrated 

flows and 80 to 100 percent water for streamflows 

(Beverage and Culbertson, 1964). The main distinction in 

this study is the difference between debris-flow deposits 

and hyperconcentrated-flow deposits (Beverage and 

Culbertson, 1964; Scott, in press) because debris flows can 

transform into hyperconcentrated flow with distance from 

the source area (Pierson and Scott, 1985). This distinction is important because hyperconcentrated flows are 

quasi-Newtonian fluids and debris flows are not.

Debris-flow deposits are differentiated from hyperconcentrated-flow deposits on the basis of characteristic 

particle sorting, sedimentary structures, and inferred 

rheological properties. Readers are referred to detailed 

descriptions of each type of deposit in Smith (1986) and 

Scott (1985). Debris-flow deposits are characterized by 

lack of sedimentary structures, poor sorting of particles, 

matrix support of cobbles and boulders, and, in some

cases, inverse fine to coarse grading. Hyperconcentratedflow deposits are also poorly sorted but exhibit clast support of large particles, have weak sedimentary structures, 

and cannot transport the extremely large boulders moved 

during debris flows. Streamflow deposits are well-sorted, 

have imbricated clasts and well-developed sedimentary 

structures, and are easily distinguished from debris-flow 

deposits.

We studied 36 tributaries of the Colorado River, and 

all had characteristic debris-flow deposits (table 1). Most 

tributaries have only debris-flow deposits and inconspicuous hyperconcentrated-flow deposits; a few tributaries in 

the western Grand Canyon (such as Havasu Creek, fig. 

1) have both well-sorted streamflow deposits and debrisflow deposits. Twenty-one of the 36 tributaries have 

evidence of debris flows within the last 25 years, including 

fresh boulder levees and matrix-supported deposits. This 

sampling of the nearly 310 ungaged tributaries of the 

Colorado River between Lees Ferry and Diamond Creek 

(fig. 1) suggests that debris flows are a major process of 

sediment transport from small drainages to the Colorado 

River in Grand Canyon National Park.

HYDRAULICS OF DEBRIS FLOWS

Debris flows have properties important both to hydraulic calculations and preservation of evidence for past 

events. Debris flows are non-Newtonian, or cohesive fluids 

that commonly move essentially as a plug in high-velocity 

laminar flow (Enos, 1977; Johnson and Rodine, 1984). 

Viscosities for debris flows may be several orders of 

magnitude higher than the viscosity of water (Costa, 

1984). Particle interlocking in the dense fluid results in 

internal friction and shear strength. As a result, debris 

flows have a finite thickness called the critical thickness 

at a velocity of zero. Turbulence is dampened in the moving fluid (Enos, 1977), which results in laminar flows that 

have significantly higher Reynolds numbers than in 

streamflows (Costa, 1984; Johnson and Rodine, 1984). 

These properties enable debris flows to be extremely 

erosive in channels and yet to flow around brittle plants 

on nearby channel margins. As a result, evidence for past 

debris flows was found entrained in the spines of live cacti, 

whereas 2-ft diameter cottonwoods were sheared off on 

nearby flood plains in Colorado River tributaries that have 

had recent debris flows.

One facet of debris-flow hydraulics facilitates the creation and maintenance of Colorado River rapids. Debris 

flows can transport large boulders long distances from 

source areas. This property may result from cohesive 

strength, which is largely a function of clay content; from 

buoyancy forces on large particles that increase because 

of lessened density differences with the surrounding 

debris-flow matrix; from greater shear stress and high 

drag forces at the base of the debris flow; from slightly
DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

positive pore-water pressures in debris flows; or from a 

combination of these factors (Costa, 1984; Johnson and 

Rodine, 1984; Pierson, 1981). Regardless of the process, 

the characteristic boulder fans at the mouths of Colorado 

River tributaries (Hamblin and Rigby, 1968; Howard and 

Dolan, 1981; Stevens, 1983) result from debris-flow 

deposition and subsequent reworking of the deposits to 

remove the matrix.

The hydraulics of debris flows are unusual compared 

with streamflow because of the high sediment concentrations and interactions among particles. Most indirect 

velocity calculations for streamflow use Manning's 

equation

#0.67 . 50.5

n

(1)

where v = mean velocity, R = hydraulic radius, S= the friction slope, and n=the roughness coefficient. Equation 1 

cannot be applied to debris flows because the roughness 

coefficient cannot be accurately estimated (Antonious 

Laenen, U.S. Geological Survey, written commun., 1986; 

Laenen and others, 1987) and because debris flows are 

not Newtonian fluids. Application of the Manning equation using the slope-area method (Chow, 1959) resulted 

in a substantial overestimation of discharge for debris 

flows in Colorado (Costa and Jarrett, 1981).

Debris flows have been modeled as a Bingham substance (Johnson and Rodine, 1984) and as a viscoplastic 

fluid (Chen, 1985). Use of either method for calculating 

velocities of debris flows requires estimation of coefficients related to shear strength or flow behavior. These 

coefficients have large ranges and considerable error is 

involved in their estimation. For example, A. Laenen 

(written commun., 1986) has shown that Chen's (1985) 

flow-behavior index, back-calculated from measured 

debris flows, varied by an order of magnitude during a 

single event and varied by more than three orders of 

magnitude when different events were compared. Such 

variation indicates that calculation of velocities from postevent evidence using these methods would involve considerable potential error.

For this study, we used simplified hydraulic formulae 

to calculate flow velocities for debris flows (Pierson, 1985). 

Evidence for the elevation of the velocity head (Chow, 

1959) usually is found where an obstacle is oriented 

perpendicular to the flow direction. In the Grand Canyon, 

flow impinging on vertical bedrock walls generally will 

leave runup evidence in sites that are protected from 

weathering. The mean velocity, v, is calculated by equating the kinetic energy of the flow to the potential energy 

of the runup by

(2)

where g= gravitational acceleration (32.2 ft/s) and bhr = 

the difference between the runup and unobstructed flowsurface elevations. An energy-correction coefficient 

normally applied to open-channel hydraulics is assumed 

to be 1 because of plug flow. Energy losses are assumed 

to be negligible.

Superelevation occurs on bends as a result of centrifugal-acceleration forces. The water-surface profile on the 

inside and outside of a bend drops and rises, respectively, to form an elevation difference khs (Pierson, 1985, fig. 

4). Assuming that all streamlines follow the same radius 

of curvature (assumed to be the centerline radius of curvature, Rc ), fully developed plug flow, and negligible 

energy losses, the mean velocity around a bend is calculated from

\0.5 (3)

where W=the effective channel width and k = a correction factor (Hungr and others, 1984). Hungr and others

(1984) suggest that A; = 2.5 to correct for reported overestimation of debris-flow velocities; however, we used 

k= 1 because equations 2 and 3 then provided internally 

consistent velocities. More sophisticated equations for 

calculating velocity from superelevation (Apmann, 1973) 

probably are not warranted for debris flows in irregular 

natural channels.

Application of equations 2 and 3 to debris flows has been 

widely used but the results have been uncertain. Pierson

(1985) found that use of these formulae resulted in computed velocities averaging 15 percent lower than actual 

velocities on the basis of measured travel times. Hence, 

use of equations 2 and 3 may result in a slightly conservative estimate of velocity. The amount of error introduced by the other assumptions is unknown but probably 

is high. 

The resultant discharge Q is estimated from

Q=A v (4)

where A = cross-sectional area. Use of equation 4 requires 

the assumption that all of the fluid passing through crosssectional area A is moving at a mean velocity of v. This 

assumption may not be valid because of ineffective flow 

areas on bends (see section "Similarities and Contrasts 

Among the Drainages"). Froude numbers were calculated 

from

F =

9'D (5)

where D is the hydraulic depth (AIW). In Newtonian 

streamflow, Froude numbers greater than 1 indicate 

supercritical flow while Froude numbers less than 1 in-
LAVA-CHUAR CREEK DRAINAGE

dicate subcritical flow. It is uncertain whether Froude 

numbers have the same significance when applied to 

debris flows. Enos (1977) found no consistent quantitative 

measure to define different energy regimes in debris 

flows.

DEBRIS FLOWS IN THREE TRIBUTARIES 

OF THE COLORADO RIVER

The magnitude and frequency of debris flows were 

evaluated in three Colorado River tributaries (fig. 1). 

Lava-Chuar Creek drainage at mile 65.5 on the Colorado 

River had a debris flow during a storm on December 3-6, 

1966 (Cooley and others, 1977). Monument Creek at mile 

93.5 had a debris flow during a summer thunderstorm on 

July 25,1984 (Potochnik and Reynolds, 1986). The Crystal 

Creek drainage at mile 98.2 also had a debris flow during 

the storm in December 1966 (Cooley and others, 1977). 

Peak discharges for these three events were estimated, 

and the channel-margin stratigraphy was analyzed for 

other past events. The fieldwork for this project was completed in March and April 1986.

METHODS

The stratigraphy in the drainages that were investigated was described to provide a chronology of debris 

flows. Correlations among deposits were made on the 

basis of characteristic lithologies, sedimentary structures, 

color, stratigraphic position, and degree of particle-size 

sorting. Organic samples contemporaneous with past 

debris flows were collected for radiocarbon analysis by 

accelerator-dating techniques (Taylor and others, 1984) 

or conventional gas-proportional counting. Accelerator 

dating was used for some samples because they were too 

small to be analyzed by conventional gas-proportional 

counting. Analyses of scarred trees (Hupp, 1984), 

historical photographs, aerial photographs, and damage 

to historic structures provided additional dating of events.

The deposits from the debris flow of 1966 were identified from photographs in Cooley and others (1977) and 

by observation of damaged trees and recent deposits in 

the Lava-Chuar Creek and Crystal Creek drainages. 

Deposits from the 1984 debris flow in Monument Creek 

were fresh and easily identified. Deposits were traced 

longitudinally using stratigraphic and sedimentologic 

characteristics. High-water marks were preserved as lines 

under small rock overhangs; as mud deposits in and under 

cacti, trees, and shrubs; as distinct levees or overbank 

deposits; and as distinct mud lines deposited over older 

material on hillslopes. The red color of the debris-flow 

deposits in Crystal Creek, for example, was vivid when 

emplaced against the dark brown soils on hillslopes or as 

a mud line against the reddish brown Cambrian Tapeats 

Sandstone.

We collected 5- to 10-pound samples of debris-flow 

matrix (diameter less than 16 mm) for reconstitution of 

water content during the event (Cooley and others, 1977; 

Gallino and Pierson, 1985; Johnson and Rodine, 1984). 

Water was gradually added to the samples until the mixture had observable cohesion and matrix support of 

16-millimeter particles. This method is relatively precise 

because small changes in the water content cause large 

changes in cohesion (Costa, 1984). In the samples, a 1 to 

2 percent by weight (2 to 4 percent by volume) range in 

water contents that created a debris-flow type of fluid was 

measured. Additional uncertainty occurs from changes in 

the particle size of deposits during post-event dewatering (Gallino and Pierson, 1985) or by lateral or longitudinal 

facies changes. This uncertainty was minimized by selective sampling of intact debris-flow matrix in protected 

sites and near sites where discharges were estimated. 

Samples were sieved to obtain particle-size distributions 

by weight percent, and point counts of particle diameters 

were made in the field. The two methods yield a numerically equivalent particle-size distribution (Kellerhals and 

Bray, 1971; Pierson, 1980).

LAVA-CHUAR CREEK DRAINAGE

The Lava-Chuar Creek drainage, 21.3 mi2 in area, 

heads on the Walhalla Plateau in the eastern Grand Canyon (figs. 1, 2). The bedrock geology of this drainage consists of an entire Paleozoic section of rocks (McKee, 1969) 

that form cliffs in the headwaters, Precambrian Galeros 

Formation that underlies more than 75 percent of the 

drainage in the open Chuar Valley, and Precambrian Dox 

Sandstone that is exposed in the first mile above the confluence with the Colorado River (Huntoon and others, 

1986). The topographic relief in the drainage basin is 5,300 

ft and the average channel slope is 0.1.

A debris flow occurred in the drainage as a result of 

intense rainfall in December 1966. An estimated 12 to 14 

in. of precipitation fell during the 5-day storm (Cooley and 

others, 1977). A debris flow began with multiple slope 

failures in the Permian Hermit Shale and Esplanade 

Sandstone in Natchi Canyon (fig. 2) and continued 6.5 mi 

to the Colorado River. Additional slope failures from the 

same formations in Lava Canyon (fig. 2) may have contributed sediments to the debris flow. Cooley and others 

(1977) report considerable damage throughout the canyon 

from the debris flow but do not report a discharge for the 

event. R.C. Euler (National Park Service, oral commun., 

1986) visited archaeological sites in the canyon before and 

after the debris flow, and his photographs illustrate the 

extent of channel changes (fig. 3A, B). It is not certain 

to what extent Lava Canyon Rapid at the mouth of the 

Lava-Chuar Creek drainage on the Colorado River was 

affected by this debris flow.
DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

STRATIGRAPHY

In addition to the debris flow of 1966, at least two debris 

flows have occurred historically in the Lava-Chuar Creek 

drainage. Exposures of debris-flow sediments deposited 

before and after 1966 were present at intervals along the 

entire length of the Lava-Chuar Creek drainage (fig. 4). 

Replication of photographs presented in Cooley and others 

(1977) indicates that a debris flow occurred after 1966 (fig. 

5). A comparison of aerial photographs indicated that this 

flow occurred between 1973 and 1984. The peak stage for 

the post-1966 debris flow was lower than the 1966 debris 

flow near the confluence of Lava and Chuar Creeks (site 

C, fig. 2) but was about equivalent near the mouth. The 

relation of discharge to stage is unknown because the 

post-1966 debris flow or other unknown streamflows locally entrenched the bed of Lava Creek by 2 to 5 ft over a

10- to 15-foot width from the level of 1966 (fig. 5). In the 

1-mile reach above the Colorado River, the presence of 

substantial material from the Dox and Galeros Formations 

in post-1966 debris-flow deposits indicates significant local 

sediment contributions from small side drainages, scour 

of channel deposits, and (or) slope failures.

An older and substantially larger debris flow occurred 

in Lava Creek in historic times before 1966. Cooley and 

others (1977) report the presence of driftwood deposited 

before 1966 near the confluence with Chuar Creek; similar 

driftwood mixed with boulders in a debris-flow levee was 

found at higher elevations above the channel than 

reported by Cooley and others (1977). The older debris 

flow overtopped an abandoned grinding mill at MacDonald Spring (site D, fig. 2) that was probably constructed as part of a distilling operation between 1890 and 

1915 (Harvey Butchart, retired professor, Northern

36°I3' -

36°08 -

0 I KILOMETER

CONTOUR INTERVAL 2000 FEET

NATIONAL GEODETIC VERTICAL

DATUM OF 1929

Chidvria . 

Point

Drainage 

boundary

EXPLANATION

Path of debris flow 

Slope failure, December 1966 

Slope failures starting the debris flow 

Depositional area

Photo replication site (see figures 3, 5) 

MacDonald Spring 

Depositional splays 

Indirect - discharge site 

I

Lava Canyon 

Rapid

FIGURE 2. The Lava-Chuar Creek drainage at mile 65.5 on the Colorado River. See figure 1 for location.
LAVA-CHUAR CREEK DRAINAGE

Arizona University, oral commun., 1986). The debris flow 

deposited distinctive sediments in the mill and left the 

trunk of an uprooted cottonwood tree on the nearby

terrace. This flow also lapped onto a 10-foot-high terrace 

near the confluence with the Colorado River and nearly 

damaged an historic housepad. The pre-1966 debris flow 

deposited sediments twice as thick as the preserved 

sediments of the debris flow of 1966 in some places along 

the channel (fig. 4).

Evidence for at least five prehistoric debris flows is 

preserved in prominent terraces along Lava Creek (fig. 

4). Hyperconcentrated-flow deposits and possible channelfill facies of additional debris flows also were found. 

Sediments are preserved as much as 12 ft above the channel bed of 1986 near the Colorado River and as much as 

20 ft above the channel bed in the narrow reaches near 

the headwaters. Driftwood lodged in a debris-flow deposit 

(symbol Z; fig. 4) 12 ft above the channel bed of 1986 had 

a radiocarbon age of 250 + 80 yr B.P. (years before present) (sample number A-4543). This deposit could not be 

traced downstream from site B (fig. 2). Radiocarbon 

dating of entrained wood in debris-flow deposits X and 

W (fig. 4) indicate maximum ages of 625 + 65 (AA-1787) 

and 1,460 ±60 (AA-1788) yr B.P. for these debris flows, 

respectively. The younger of these events (X) had a 

hyperconcentrated-flow facies associated with the deposit. 

On the basis of deposit thickness and height above the 

channel, the debris flows W, X, and Y had little attenuation in stage in the 3-mile reach between sites E and F 

(fig. 2) and reached the Colorado River.

FIGURE 3. Lava Creek at the confluence with Chuar Creek, 3.8 miles 

upstream from the Colorado River. View B (May 1967) is slightly different from A (May 1966) and shows significant channel alteration 

following the 1966 debris flow. View C (March 1986) matches B and

shows revegetation and entrenchment of the channel after the 1966 

and subsequent debris flows. Photograph by R.C. Euler (National Park 

Service). See site C, figure 2, for location.
DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

The stratigraphy in the Lava-Chuar Creek drainage 

suggests an average interval of about 20 to 30 years 

between debris flows during the last 80 years, depending 

on the age used for the mill at MacDonald Spring. On the 

basis of radiocarbon-dated debris-flow deposits in terraces, the Lava-Chuar Creek drainage has had a minimum 

of one debris flow that reached the Colorado River every 

190 years during the last 1,500 years. Debris flows may 

actually reach the Colorado River more frequently 

because small prehistoric debris flows, such as debris flow 

Z, may not have overtopped the terraces to leave depositional evidence.

LONGITUDINAL VARIATION IN 

THE 1966 DEBRIS-FLOW DEPOSITS

Sedimentologic characteristics of the debris flow of 1966 

show little significant longitudinal variation in cohesiveness. As noted by Cooley and others (1977), the flow remained a debris flow the entire length of the drainage. 

The flow sustained or locally increased its volume by 

incorporation of bed material, talus, and exposed sedimentary rocks of the Galeros and Dox Formations. Abundant 

vesicles preserved in the debris-flow matrix at many sites 

indicate significant air entrapment in the flow or frothy,

Post 

1966

O.I O.Z 1.9 2.9 3.1 3.8 4.0

DISTANCE UPSTREAM FROM THE COLORADO RIVER,IN MILES 

" Channel bed

EXPLANATION

Radiocarbon age, in years before present

Post -1966 debris-flow deposit

1966 debris-flow deposit

Historic debris-flow deposit

Prehistoric debris-flow deposit

Soil or incipient soil

Stratigraphy hidden or not present

Talus, hillslope debris, or Colorado River deposit

Boulder

Labels for correlative debirs-flow deposits

mm

W.X.Y.Z

FIGURE 4. Stratigraphy of debris-flow deposits in the Lava-Chuar Creek

drainage.

turbulent conditions at the flow margins. Mudcoats preserved on bedrock walls and indurated calcic deposits also 

demonstrate that the flow retained its cohesive properties throughout the length of the drainage.

Upon debouching from Natchi Canyon, the debris flow 

deposited an extensive field of boulders over what 

previously was a marshy site (Cooley and others, 1977). 

The 1966 levee is 6 ft above the channel bed of 1986 

downstream of Natchi Canyon, whereas the debris-flow 

deposit Z and associated driftwood is 12 ft above the channel. Between sites B and C (fig. 2), the debris flow was 

confined in a narrow, boulder-clogged channel with a 

steplike appearance (Cooley and others, 1977, fig. 29B).

FIGURE 5. Lava Creek, 0.2 mile upstream from the confluence with 

Chuar Creek. View A (March 1967) shows that the debris flow of 1966 

has created a nearly level denuded channel. View B (March 1986) shows 

an entrenched channel and post-1966 debris-flow deposits in the 

foreground. See site C, figure 2, for location.
MONUMENT CREEK DRAINAGE

Little depositional evidence for the 1966 debris flow is 

preserved in this reach, and deep scour holes suggest this 

to be a reach of many transformations between laminar 

and turbulent flow (Fisher, 1983) and predominantly 

supercritical flow conditions. The reach immediately 

above MacDonald Spring (site D, fig. 2) is similar.

At site E, the debris flow was not confined by lateral 

terraces for 0.2 mi. A large levee formed and was 

repeatedly breached as the flow deposited lobate splays 

of sediment. The critical thickness of the deposit at which 

the debris flow stopped moving ranged from 1.6 to 2.3 

ft, and boulders 2 to 5 ft in diameter compose the preserved levee. The volume of sediment preserved in the 

lobes suggests that this debris flow was sustained for a 

relatively long time period rather than consisting of a 

single, short pulse behind a moving boulder dam. The 

debris flow of 1966 inundated a 6-foot-high terrace 800 

ft upstream from the Colorado River and deposited 

sediments 0.1 to 1.3 ft thick composed of poorly sorted 

particles and matrix-supported boulders.

Particle-size distributions for the debris flow of 1966 

indicate a poorly sorted and coarse-grained deposit (fig. 

6). The debris flow had 4 to 5 percent silt and clay and 

about 30 to 35 percent sand. One boulder at site F (fig. 

2) that was transported during the debris flow of 1966 

had a median diameter of 4.8 ft and weighed an estimated 

9 tons. More commonly observed boulders were 1 to 2 ft 

in diameter. Reconstitution of debris-flow deposits from 

the Lava-Chuar Creek drainage indicated a water content 

of 21 to 24 percent by volume.

DISCHARGE CALCULATION

Superelevation evidence deposited from the passage of 

the debris flow of 1966 around a 90° bend was surveyed

Ul

o 

cr

UJ

o.

I

o

UJ£

UJ

>

IID 

O

100

80

60

40

20

-8

PARTICLE DIAMETER,IN 0 UNITS 

-4048 12

Debris-flow deposit

Debris-flow deposit 

at site C

256 16 I 0.063 O.OO4

PARTICLE DIAMETER,IN MILLIMETERS

FIGURE 6. Particle-size distributions of the debris flow of 1966 in the 

Lava-Chuar Creek drainage. See figure 2 for locations of sites.

0.2 mi upstream from the Colorado River (site F, fig. 2). 

The 12-foot-thick debris-flow deposit was preserved 

against a near-vertical cliff of Dox Formation. The radius 

of curvature of the centerline of the channel is 37 ft, 

whereas the channel width is 110 ft. This apparent 

discrepancy results from the combination of a bend with 

a low radius of curvature and a width that includes flow 

over the point bar on the inside of the bend, and may invalidate the assumption that all streamlines follow the 

same radius of curvature (see section "Hydraulics of 

Debris Flows"). A velocity of 12 ft/s was estimated on 

the basis of an elevation difference (A/is) of 13.3 ft between the inside and outside high-water marks on the 

bend (table 2). The velocity could range from 10 to 14 ft/s 

because of uncertainties in the radius of curvature (Rc ).

Determination of the cross-sectional area of flow was 

unexpectedly difficult. The cross-sectional area at the 

superelevation site was about 3.5 times larger than 

upstream or downstream cross sections. The discharge 

calculated using the area at the superelevation site is 

14,200 ft3/s. If this discharge is correct, use of equation 

(4) suggests that the velocity must increase downstream 

to 46 ft/s over 250 ft. Similarly, the flow would have to 

decelerate from 41 to 12 ft/s over 125 ft as the flow enters 

the bend. The problem with large cross-sectional areas 

at superelevation sites compared with upstream and 

downstream cross sections occurred in the other two 

tributaries studied, and a justification for the discharge 

calculations is presented in the section "Similarities and 

Contrasts Among the Drainages."

The discharge for the 1966 debris flow was estimated 

from an average of the cross sections 125 ft upstream and 

250 ft downstream, respectively, from the site of maximum superelevation. Using an average area of 330 ft2, 

the debris flow of 1966 had a peak discharge of 4,000 

ft3/s (table 2) with a Froude number between 1.0 to 1.4. 

The average water content of reconstituted samples is 

22.5 percent, hence the peak sediment and water 

discharges are estimated to be 3,100 and 900 ft3/s, 

respectively.

MONUMENT CREEK DRAINAGE

Monument Creek, 3.3 mi2 in area, heads on the Coconino Plateau on the south side of the Colorado River (figs. 

1, 7). The bedrock geology of this drainage consists of the 

entire Paleozoic section (Huntoon and others, 1986), with 

the Permian Kaibab Limestone and Coconino Sandstone, 

Mississippian Redwall Limestone, and Cambrian Muav 

Limestone forming prominent cliffs. The Permian Hermit Shale and Permian and Pennsylvanian Supai Group 

form benches in the otherwise vertical cliffs. An erosional 

surface in the Cambrian Bright Angel Shale and underlying Tapeats Sandstone forms the Tonto Platform, which
10 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

is present in much of the Grand Canyon. Monument Creek 

cuts through the Precambrian Vishnu Schist in the 1.5 

mi upstream from the Colorado River and forms a deep, 

narrow canyon. Topographic relief in the drainage basin 

is 4,500 ft and the average channel slope is 0.2.

On July 27, 1984, a thunderstorm centered over the 

eastern part of Monument Creek initiated a debris flow. 

Rainfall recorded at Grand Canyon, about 1 mi from the 

headwaters (fig. 1), indicates a total of 1.08 in. for the 

storm, with 0.92 in. falling in 1 hour. These rainfall totals 

are not unusual for the station and the month of July 1984 

was not unusually wet. However, the high-intensity rainfall triggered a free-falling avalanche, which fell 2,000 ft 

into the canyon from the Esplanade Sandstone on the Mojave Wall (fig. 7). The coarse, poorly sorted, and angular 

debris filled the channel to a depth of 20 ft and created 

a debris dam that had not been breached by 1986. The 

avalanche transformed into a debris flow with the addition of runoff and water in the channel. Other eastern 

tributaries of Monument Creek also had debris flows initiated by smaller slope failures in the Supai Group (fig.

0 05KILOMETER 

CONTOUR INTERVAL 2000 FEET 

NATIONAL GEODETIC VERTICAL 

DATUM OF 1929

EXPLANATION

 Path of debris flow

X Slope failure, July 1984

A Tapeats alcove

B,C Indirect-discharge site

D New debris fan

E Debris bar ("Island")

FIGURE 7. Monument Creek drainage at mile 93.5 on the Colorado 

River. See figure 1 for location.

7). The resulting debris flow traveled 2.8 mi to the Colorado River, where deposition caused a significant constriction of the Colorado River at Granite Rapid (fig. 8).

STRATIGRAPHY

Deposits preserved in terraces and associated scarred 

catclaw trees indicate that a historic debris flow occurred 

before 1984 (fig. 9). Ring counts on scarred and healed 

catclaw trees suggest that this debris flow occurred 20 

to 25 years before 1986. The heights of the scarred trees 

are roughly equivalent to or slightly higher than the stage 

of the debris-flow peak of 1984. Aerial photographs, 

however, do not reveal obvious channel changes in Monument Creek after 1965. The pre-1984 debris flow was initiated near or upsteam from the avalanche source for the 

1984 debris flow. Locally, this flow deposited 3-foot-thick 

sediments and had a stage 28 ft above the channel.

Evidence for older debris flows in Monument Creek is 

scanty because of poor exposures and erosion during the

-T-?r tr

FIGURE 8. Mouth of Monument Creek. In view A (September 1872), 

the discharge in the Colorado River apparently is between 20,000 and 

25,000 cubic feet per second. Curved lines in the center of the 

photograph are cracks in the original glass-plate negatives. In view
MONUMENT CREEK DRAINAGE 11

historic events. Monument Creek has two terraces composed of layered debris-flow deposits a low terrace that 

was inundated in 1984 and a high terrace covered with 

mesquite and catclaw trees that was not inundated in 

1984. At Tapeats Alcove (site A, fig. 7), an exposure of 

the high terrace showed three prehistoric debris-flow 

deposits, one of which had a radiocarbon age of 170 ± 90 

yr B.P. (A-4542). Lack of longitudinal correlation of these 

deposits with others along Monument Creek, however, 

precludes any meaningful discussion of the frequency of 

prehistoric debris flows.

LONGITUDINAL VARIATION IN 

THE 1984 DEBRIS-FLOW DEPOSITS

The debris flow of 1984 was initiated at slope failures 

on the east side of the drainage (fig. 7). The largest slope 

failure, an avalanche, hit a water-filled channel and splattered mud and debris as much as 200 ft above the channel on the west side of the drainage. The particle-size

distribution near the slide (fig. WB) shows that the flow 

was poorly sorted with coarse clasts as much as 256 mm 

in diameter. A lithological count of clasts revealed that 

64 percent were sandstones from the Supai Group and 

36 percent were from the Redwall Limestone.

Downstream from the avalanche, the debris flow may 

have undergone several transformations from laminar to 

turbulent flow before reaching Tapeats Alcove (site A, fig. 

7). Lodged boulders created local 3- to 10-foot drops in 

the channel bed; recessional deposits upstream from these 

drops are clearly of debris-flow origin, whereas hyperconcentrated flow deposits occur downstream from the 

drops. A particle-size distribution measured above 

Tapeats Alcove (fig. WB) shows a poorly sorted debrisflow matrix with 40 percent sand.

Two small tributaries of Monument Creek downstream 

from the avalanche contributed debris flows to the main 

channel. A debris flow from the downstream tributary occurred after the peak, as inferred from a superelevation 

of the flow over the 7- to 10-foot-high banks of Monument

B (September 1968), the discharge in the Colorado River is about 8,000 

cubic feet per second. The river appears to be more constricted than 

in 1872 despite differences in discharge, and a debris flow that occurred 2 to 7 years prior to the photograph date may have contributed

to the constriction. In view C (April 1986), the discharge in the 

Colorado River is 28,500 cubic feet per second. The 1984 debris flow 

has constricted the river significantly, especially in comparison with 

1872 conditions.
12 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

Creek at the confluence. The flow remained overbank 230 

ft downstream and may have caused a recessional debrisflow pulse. No debris from these two tributaries remains 

in the channel of Monument Creek, indicating that flow 

in the main channel was still erosive enough to remove 

the additional sediments.

The peak of the debris flow sustained its cohesive properties until it reached the Colorado River. Superelevation 

marks appear on most bends, and lateral levees were 

deposited in channel irregularities. In the narrow bedrock 

canyon 0.25 mi downstream from Tapeats Alcove, three 

deposits with a lower stage than the peak discharge are 

preserved. These deposits are suggestive of recessional 

debris and (or) hyperconcentrated flows following the 

main pulse. The particle-size distribution for the debris 

flow in this section (fig. 10C) indicates an increased 

percentage of boulders and a sand content of 30 percent. 

The additional boulders were probably entrained from the 

bed and terraces. Below site B, one boulder transported 

by the flow is 9 ft in diameter; a second rectangular block

L

1964 

Levee

O.O I.I 12 16 1.8 21 3O

DISTANCE UPSTREAM FROM THE COLORADO RIVER,IN MILES 

Chonnel bed

EXPLANATION

I7O±9O Radiocarbon age. in years before present 

1984 debris-avalanche deposits 

1984 debris-flow deposit 

Pre-1984 debris-flow deposit 

Soil or incipient soil 

Stratigraphy hidden or not present 

 Boulder

FIGURE 9. Stratigraphy of debris-flow deposits in the Monument Creek 

drainage.

has an average length of 8 ft and weighs an estimated 

37 tons.

Near the Colorado River, the deposits in the center of 

the channel abruptly change to well-sorted and imbricated 

boulder bars (fig. 8C) superficially resembling sieve 

deposits (Hooke, 1967). The debris flow at this point was 

confined and deposition occurred to an average depth of 

5 ft. At locally unconfined sites, the critical thickness of 

the debris flow was 3 ft. The particle-size distribution (fig. 

10D) shows a well-sorted cobble deposit with a median 

diameter of 32 mm, although poorly sorted matrix was 

found on the channel margin. We speculate that either 

recessional or post-event streamflow, dewatering of the 

deposit after deposition, or positive pore pressures from 

springs in the channel bed caused the nearly complete 

removal of the debris-flow matrix from the boulders and 

its subsequent transport into the Colorado River.

DISCHARGE CALCULATIONS

Superelevations resulting from the debris flow of 1984 

were measured at three sites on Monument Creek in 

reaches 0.3, 0.5, and 1.5 mi upstream from the Colorado 

River. At Tapeats Alcove (site A, fig. 7), an elevation difference of 4.7 ft was measured from mudlines on the wall 

of a prominent overhang. Channel geometry at the site 

(table 3) was used to calculate a velocity of 12 ft/s for the 

debris flow. The bed of the channel consists of large blocks 

of Tapeats Sandstone, which had fallen from the roof of 

the alcove either before or during the debris flow. The

100

80

60

40

20

.-12

PARTICLE DIAMETER.IN 0 UNITS 

-8-4 0 4

256 16 I 0.063 0.004 

PARTICLE DIAMETER.IN MILLIMETERS

EXPLANATION

A Avalanche deposit

B Debris-flow deposit above site A

C Debris-flow deposit at site B

D Fan deposit at Colorado River

FIGURE 10. Particle-size distributions of the debris flow of 1984 in 

the Monument Creek drainage. See figure 7 for locations of sites.
MONUMENT CREEK DRAINAGE 13

cross sections measured at the superelevation mark and 

a wide, eroded reach upstream had twice the area of a 

cross section that was measured 50 ft downstream (table 

3). We used the cross-sectional area measured 50 ft 

downstream (320 ft 2) to calculate a peak discharge of 

3,800 ft 3/s for the debris flow. Reconstitution of a debrisflow matrix sample taken upstream indicates a water content of 32 to 34 percent by volume.

At site B (fig. 7), resistant Vishnu Schist forms the bed 

of the channel. A maximum superelevation of 3.7 ft was 

measured on this bend (fig. 11), which is 0.5 mi upstream 

of the Colorado River. A runup elevation of 2.1 ft was 

measured above the superelevation line. Velocities of 11.0 

and 11.5 ft/s were calculated from the superelevation and 

runup evidence, respectively (table 4). As observed 

previously, cross sections in the bend had significantly 

larger areas than upstream and downstream cross sections; hence, the average of the upstream and downstream 

cross sectional areas (320 ft 2 ; table 4) was used. The 

resulting discharge is between 3,600 and 4,000 ft 3/s, 

depending upon whether velocity was calculated from 

runup or superelevation evidence. The water content of 

the peak flow, reconstituted from a sample collected near 

the site, was 27 to 29 percent by volume.

At site C, 0.3 mi from the Colorado River (fig. 7), superelevation marks were preserved on a bend having considerable debris-flow deposition. No controls on channel 

depth are present in this reach and either aggradation or 

degradation may have occurred. Survey data revealed an 

ambiguous superelevation because of a slight channel expansion (97 to 106 ft) over a 20-foot distance. Use of the 

respective elevation differences (3.4 or 4.6 ft) with the 

associated width resulted in a velocity between 11.9 and 

13.2 ft/s. Possible deposition after the peak flow in 

upstream sections precluded any meaningful calculation 

of cross-sectional area. A cross section measured 45 ft 

downstream from the lower superelevation site yielded 

an area of 320 ft2 , although the actual area might be considerably larger due to possible deposition after the peak 

flow. The resulting discharge ranged from 3,800 to 4,200 

ft 3/s with a Froude number between 1.2 and 1.4 (table 

5). The water content of the flow was probably similar 

to that estimated for site B (28 percent).

SEDIMENT VOLUME

The new debris fan at the Colorado River (fig. 8) was 

surveyed to estimate the volume of material deposited 

during the debris flow of 1984. The debris flow entered 

and partially dammed the Colorado River (Mike Yard, 

boatman, Humphrey Summit Adventures, Flagstaff, 

Arizona, oral commun., 1986), which had a mean discharge of about 24,000 ft 3/s on July 25. Observers noted 

that the newly formed fan contained significant amounts 

of matrix immediately after the debris flow, but that the

mud was quickly eroded from the fan. Higher discharges 

on the Colorado River in the fall of 1984 and spring of 

1985 partially eroded the newly formed fan (Mike Yard, 

oral commun., 1986).

Without knowing the exact geometric configuration of 

the fan after the event, a volume of sediment was estimated on the basis of four hypothesized scenarios of 

deposition (table 6) and extension of the debris fan remaining in 1986 into the Colorado River. First, we assumed 

the deposit that remained in April 1986 was the entire 

extent of the deposition; this scenario results in an unrealistically low estimate of sediment volume. Second, we 

assumed that the debris flow completely dammed the river 

at Granite Rapid; this scenario results in an unrealistically

Maximum 

superelevation

Ruup

\

EXPLANATION

Channel bed 

Cross-section location 

Inside-bend debris-flow marks 

Outside-bend debris-flow marks

40 80 120 160 200 

DISTANCE ON THALWEG, IN FEET

FIGURE 11. Plan map and longitudinal profile for indirect-discharge 

site B in Monument Creek, 0.5 mile upstream from the Colorado River.
14 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

high estimate of sediment volume. Two additional 

scenarios of partial damming of the river that more 

realistically paralleled the eyewitness report also were 

assumed. River depth at Granite Rapid was 11 ft at a 

discharge of 25,000 ft 3/s in April 1984 (R.P. Wilson, U.S. 

Geological Survey, written commun., 1986). A triangular 

cross section was assumed for the 200-foot-wide channel. 

The depth of the fan deposit was estimated at 5 ft on the 

basis of natural exposures and the 3-foot depth of channel filling was suggested from critical thicknesses of the 

deposit on the fan margin.

The calculated volumes (table 6) indicate a range of 

possible volumes of sediment deposited during the debris 

flow. The most realistic estimate of sediment volume 

(scenario 3; table 6), with the debris flow partially damming the river, is about 300,000 ft 3. Using a measured 

sand content of 35 percent and assuming that all of the 

debris-flow matrix entered the Colorado River, thus explaining the fines-depleted boulder bar, the estimated 

volume of sand-sized particles is 84,000 ft 3 for this 

scenario. The estimated volume of sand ranged from 

56,000 to 150,000 ft 3 among the scenarios (table 6). This 

calculation indicates that a substantial volume of sand 

entered the Colorado River during the 1984 debris flow, 

although the exact volume is uncertain.

Further assumptions were made concerning the debris 

fan to estimate the minimum elapsed time of the discharge. Sedimentologic evidence suggests a saw-toothed

hydrograph of unknown duration (fig. 12). At least three 

recessional debris-flow surges followed the initial pulse 

although their stages were much lower (1-3 ft compared 

with greater than 10 ft). Similar multipeaked hydrographs 

of debris flows have been reported elsewhere (Hungr and 

others, 1984; Pierson, 1985). Flow between the surges 

may have been hyperconcentrated (see Pierson, 1985). We 

assumed that (1) the entire volume of material reaching 

the debris fan and the Colorado River was delivered in 

the first pulse and (2) the hydrograph shape could be 

modeled as a square wave with the recessional debris 

flows not reaching the debris fan (fig. 12). The resulting 

minimum duration times (table 6), which range from 1 to 

nearly 3 minutes, demonstrate the probable transitory 

nature of this event.

CRYSTAL CREEK DRAINAGE

The Crystal Creek drainage, 43.3 mi2 in area, is the 

largest of the three drainages studied (figs. 1, 13). The 

geology of this drainage consists of the Paleozoic section 

of Kaibab Limestone through the Muav Limestone that 

forms prominent cliffs in the headwaters, the nearly flat 

Tonto Platform developed on top of the Tapeats Sandstone, and the Vishnu Schist forming deep canyons along 

the lower 5 mi of the drainage (Huntoon and others, 1986). 

The topographic relief in the drainage is 6,500 ft and the 

average channel slope is 0.07.

EXPLANATION

 Hypothetical hydrograph

 Model of hydrograph peak 

Tp Time of peak discharge

TIME, DIMENSIONLESS 

FIGURE 12. Hypothetical hydrograph of the debris flow of 1984 in Monument Creek as suggested by stratigraphic evidence.
CRYSTAL CREEK DRAINAGE 15

A debris flow occurred during the storm in December 

1966 that also initiated a debris flow in the Lava-Chuar 

Creek drainage (Cooley and others, 1977). Because of the 

sustained nature of the storm, the flood consisted of 

streamflow of unknown discharge followed by a large 

debris flow and subsequent streamflow of moderate

discharge (Cooley and others, 1977). The debris flow 

reportedly had either a single pulse or multiple pulses in 

the lower parts of the drainage. The debris flow started 

at 11 slope failures in the headwaters of Milk Creek (fig. 

13) and travelled 13 mi through Milk Creek and down 

Dragon and Crystal Creeks to the Colorado River.

II2°07'

36°I5'

36° 10'

EXPLANATION

Debris flow path 

Slope failure 

Destroyed mescal pit 

Cooley indirect-discharge site 

Indirect-velocity site 

Tapeats narrows 

E,F,G Indirect-discharge site 

H Debris fan and rock garden

Drainage 

divide

Drainage 

boundary

2 MILES

0 I 2 KILOMETERS

CONTOUR INTERVAL 2000 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

FIGURE 13.-The Crystal Creek drainage at mile 98.2 on the Colorado River. See figure 1 for location.
16 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

Streamflow that followed the debris flow partially 

obliterated the lower parts of mudlines and caused significant channel erosion (Cooley and others, 1977). The debris 

fan resulting from the debris flow of 1966 significantly 

constricted the Colorado River at Crystal Rapid.

Cooley and others (1977) calculated discharges for the 

different phases of the flood from evidence at several sites 

in the Crystal Creek drainage. A peak flow of 100 ft 3/s 

was estimated for Crystal Creek above its confluence with 

Dragon Creek (fig. 13), indicating that this part of the 

drainage added little streamflow to the flood. In contrast, 

Cooley and others (1977) estimated a discharge of 29,000 

ft 3/s for the peak of the debris flow on Dragon Creek (site 

B, fig. 13) using the slope-area method and a Manning's 

n value of 0.070. Cooley and others (1977) calculated a 

velocity of 23 ft/s with a Froude number of 1.1 to 1.2 for 

the flow. A discharge of 1,000 ft 3/s was estimated for 

streamflow on Dragon Creek upstream from the confluence with Milk Creek. This discharge could have contributed to the post-debris-flow streamflow in the drainage.

The debris flow of 1966 caused considerable channel 

change and damaged archaeological and historical sites 

(Cooley and others, 1977). The archaeological site (site A, 

fig. 13), a mescal (agave-roasting) pit probably used between A.D. 1050 and 1150, was inundated and could not 

be exactly located during post-flood surveys. Cooley and 

others (1977) concluded on the basis of this evidence that 

the debris flow was the largest event in 800 years with 

a recurrence interval of several centuries. In contrast, the 

recurrence interval for the flood of December 1966 on 

Bright Angel Creek (4,000 ft 3/s) was estimated at 25 

years. The 1966 debris flow obliterated a mine shaft 3 to 

4 ft above the bed of Dragon Creek just upstream from 

its confluence with Crystal Creek (Harvey Butchart, 

retired professor, Northern Arizona University, oral 

commun., 1986). The destruction of this shaft, which was 

probably dug between 1893 and 1916, indicates that large 

floods or debris flows had not passed the confluence of 

Crystal and Dragon Creeks between 1916 and 1966.

STRATIGRAPHY

Most of the depositional record of prehistoric debris 

flows has been eroded from the Crystal Creek drainage 

because of the apparent high frequency of events. 

Stratigraphic sections (fig. 14) indicate at least three 

prehistoric debris flows have passed through the 2.5-mile 

reach of Crystal Creek upstream from the Colorado River. 

A radiocarbon age of 180 ±70 yr B.P. (AA-1784) from 

wood entrained in the lowermost of the debris-flow 

deposits suggests that a minimum of three debris flows 

have occurred in 200 years. On the basis of sedimentologic 

characteristics, longitudinal correlations of the deposits 

indicate that at least two of these flows reached a point 

2.1 mi above the Colorado River. Although we found no

stratigraphic evidence of old flows between mile 2.1 and 

the mouth, it is reasonable to assume that the three 

prehistoric debris flows reached the Colorado River.

In Tapeats Narrows on Dragon Creek (site D, fig. 13), 

an exceptional exposure of stratigraphy revealed a complex depositional record of at least seven debris flows 

beneath the 1966 deposit. Interbedded sand and debrisflow deposits and complex cut-and-fill structures in the 

stratigraphy indicate a fluctuating bed in Dragon Creek 

that existed in response to debris flows. A radiocarbon 

age of 355 ± 70 yr B.P. (AA-1786) near the base suggests 

that six of these flows occurred in the last 300 to 400 

years. A radiocarbon age of 130 + 50 yr B.P. (AA-1785) 

on a layer of accumulated organic debris beneath the last 

flow before 1966 and a "modern" (near A.D. 1950; 

A-4541) age on the bark of a buried tree (fig. 14) suggests 

a high frequency of events at this site. We interpret the 

radiocarbon age on the tree as more reliable than the age 

on the litter layer.

Debris flows occur more frequently in the Crystal Creek 

drainage than the frequency stated by Cooley and others 

(1977). The 1966 debris flow is the only historic event 

preserved in the stratigraphy; however, evidence for 

lower-stage, historic debris flows may have been obliterated in 1966. On the basis of stratigraphy preserved in 

the lower part of the drainage, four debris flows (including 

the one in 1966) have reached the Colorado River in 200 

years. Therefore, a debris flow that is large enough to 

reach the Colorado River occurs approximately every 50 

years. Smaller debris flows occur at about the same frequency near the headwaters and significantly aggrade the 

channel and possibly store sediment in advance of larger 

debris flows that are capable of reaching the Colorado 

River.

Relocation of the camera position for photographs taken 

in 1967 (Cooley and others, 1977; figs. 7, 33, 34B, and 

37) provided evidence for the longitudinal extent of a 

debris flow that occurred after 1966. At site A (fig. 13), 

debris-flow deposits fill the 1967 channel bottom by 2 to 

3 ft, and a prominent headcut on a side channel (Cooley 

and others, 1977, fig. 33) has migrated upstream 5 to 10 

ft. Flow past the site of Cooley and others' indirectdischarge measurement (site B, fig. 13) shifted large 

boulders but caused little aggradation. The major change 

that is apparent in the matched photographs is the 

collapse of the vertical banks that were present in 1967 

(fig. 15). Resurvey of this site revealed that the channel 

had widened by 5 to 15 ft, small talus deposits had encroached on the channel from the banks, and no aggradation had occurred on the bedrock channel. Changes caused 

by the post-1966 debris flow are less apparent downstream, although minor changes were observed in a comparison of aerial photographs of the fan deposit at the 

mouth of Crystal Creek taken in 1973 and 1984.
CRYSTAL CREEK DRAINAGE 17

LONGITUDINAL VARIATION IN 

THE 1966 DEBRIS-FLOW DEPOSITS

We found stratigraphic evidence to support both the sequence of fluvial events and a multiple-pulse debris flow 

reported for the flood of 1966 (Cooley and others, 1977). 

We based much of our interpretation and identification 

of deposits on photographs of Crystal and Dragon Creeks 

contained in Cooley and others (1977); these sites were 

relocated in 1986. Our descriptions provide additional insights into the nature of debris flows in this drainage and 

are not intended to supersede those of Cooley and others 

(1977).

20

1966

15

UJ 

UJ

C/3

O

Q_ 

UJ 

O

l_l_ 

O

HX 

O 

UJ

X

10

Stratigraphic sections between 4 and 5 mi upstream 

from the Colorado River had "sandy sole layers" (Scott, 

1985), consisting of relatively well-sorted, friable sand and 

gravel deposits (fig. 16), which underlie the poorly sorted 

debris-flow deposit. Sole layers have been interpreted as 

a debris flow interacting with streamflow at the front of 

the initial pulse (K.M. Scott, U.S. Geological Survey, oral 

commun., 1986). Streamflow probably was hyperconcentrated with sediment and may have been pushed down 

the channel by the more rapidly moving debris flow. The 

presence of sole layers supports the hypothesis of a flood 

preceding the debris flow (Cooley and others, 1977).

1966

1966

0.7 2.1 2.3 2.5 3.5 4.1 4.4

DISTANCE UPSTREAM FROM THE COLORADO RIVER,IN MILES 

 Channel bed

5.6

EXPLANATION

180db 70 Radiocarbon age, in years before present 

1966 debris-flow deposit 

Pre-1966 debris-flow deposit 

Hyperconcentrated or streamflow deposit 

Soil or incipient soil 

Stratigraphy hidden or not present 

Boulder

FIGURE 14. Stratigraphy of debris-flow deposits in the Crystal Creek drainage.
18 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

FIGURE 15. Dragon Creek, 6.2 miles upstream from the Colorado River. The piece of driftwood at the left center 

of view B (April 1986) is not the same piece as in view A (February 1967). Note in view B that the large rocks 

at the upper left and right have been moved downstream and the bank has collapsed in the foreground. Flow 

in the channel moves right to left.
CRYSTAL CREEK DRAINAGE 19

The debris flow of 1966 left considerable stage and 

sedimentologic evidence of its passage in the Crystal 

Creek drainage. In Tapeats Narrows (site D, fig. 13), 

mudlines were observed 40 ft above the current channel. 

The red color of debris-flow matrix contrasted greatly 

with the brown soils on terraces and hillslopes. The 

damaged mescal pit (site A, fig. 13) was buried under 0.1 

to 0.6 ft of red matrix deposit. The site, on the outside 

of a slight river bend, was inundated by the superelevated 

debris flow, but erosion was slight. Downstream, terraces 

of approximately the same height were not inundated.

Debris-flow deposits and mudlines have been preserved 

along the 4.5 mi of Crystal Creek below its confluence 

with Dragon Creek (fig. 13). The flow from Dragon Creek 

blocked Crystal Creek at the confluence with a 13-ft-high 

boulder deposit. Debris-flow deposits from Dragon Creek 

were found 300 ft upstream along Crystal Creek. Downstream, the debris flow entered a steep bedrock canyon 

in the Vishnu Schist and left mudlines as much as 20 ft 

above the current channel bed. Evidence for recessional 

debris flows after the main peak was preserved in the 

2.5-mile-long reach upstream of the Colorado River. The 

heights of the recessional debris-flow deposits, which 

create a sawtooth appearance on the floodplain, are approximately 5 and 6 ft below the high-water marks for 

the main debris-flow pulse at site G (fig. 13).

The effects of the debris flow of 1966 on Crystal Rapid 

are well known (Collins and Nash, 1978; Kieffer, 1985; 

Stevens, 1983). The debris flow almost certainly dammed 

the Colorado River temporarily until subsequent flows 

eroded through the left (south) side (Kieffer, 1985). In 

1965, the width of the Colorado River at Crystal Rapid 

was approximately 280 ft at a discharge of 48,000 ft 3/s 

(Bill Emmett, U.S. Geological Survey, written commun., 

1986). In March 1967, the width was only 100 ft at a 

discharge of about 10,000 ft3/s (Cooley and others, 1977). 

Maps prepared by S.W. Kieffer (U.S. Geological Survey, 

written commun., 1986) from aerial photographs taken 

in 1984 indicate a width of 130 ft at a discharge of 5,600 

ft3/s. A comparison of photographs of Crystal Rapid 

taken in 1966 and 1986 (fig. 17) documents the persisting 

changes. The rock garden (site H, fig. 13), or debris bar, 

located below the rapid and formed from outwash from 

the fan at the mouth of Crystal Creek, was substantially 

increased as a result of the debris flow. Photographs in 

Collins and Nash (1978) taken at low discharge in the 

Colorado River show a pre-1966 debris bar at the site of 

the present debris bar, but aerial photographs taken in 

1965 at a discharge of 45,000 ft 3/s reveal no obvious 

debris bar.

DISCHARGE CALCULATIONS

Velocities and discharges were calculated for the peak 

of the debris flow of 1966 from mudlines and deposits in

the Crystal Creek drainage. At site C (fig. 13), a tight, 

nearly 180° bend in Dragon Creek, an elevation difference 

of 11.9 ft was measured between the high-water marks 

in cacti and shrubs on the inside and outside of the bend. 

Based on a radius of curvature of 36 ft and width of 103 

ft, the debris flow had a mean velocity of 11.5 ft/s. The 

discrepancy between the radius of curvature and the 

width may invalidate the assumption that all streamlines 

follow the radius of curvature (see section "Hydraulics 

of Debris Flows"). The channel had significantly aggraded 

after 1966, and cross sections necessary for a discharge 

calculation could not be surveyed.

Below Tapeats Narrows, a runup deposit preserved 

under an overhanging ledge of Tapeats Sandstone provided an opportunity to estimate the discharge for the 

debris flow of 1966 (site E, fig. 13). We calculated a mean 

velocity of 15.9 ft/s from the runup evidence (table 7). One 

cross section with an area of 710 ft2 was measured at the 

runup site and resulted in an estimated discharge of 

11,300 ft3/s. The longitudinal variation in cross-sectional 

area was not investigated at this site, but it may have been 

substantial.

Photographs from Cooley and others (1977) were used 

to reconstruct high-water marks at site F (Cooley site 

number Ariz. B:16:42). The prominent superelevation

100

UJ

o

E 80 

Qj_T 60

PARTICLE DIAMETER,IN 0 UNITS 

-10 -6 -202 6 10

40

LJ 

>

< 20

ID

O 0

I I I I I I I f

/

/

/

/ Sole layer

i / i i i i

1024 64 40 0.25 0.016 

PARTICLE DIAMETER ,IN MILLIMETERS

EXPLANATION

 - COARSE-GRAINED FACIES Site G, 

0.9 mile upstream from Colorado River

 FINER GRAINED DEPOSIT Site G, 

0.9 mile upstream from Colorado River

 DEBRIS-FLOW DEPOSITS Confluence of 

Crystal and Dragon Creeks, 4.5 miles 

upstream from Colorado River

FIGURE 16. Particle-size distributions of the debris flow of 1966 in 

the Crystal Creek drainage. See figure 13 for locations.
20 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

marks (Cooley and others, 1977, fig. 16A) were relocated 

and surveyed. Elevation differences between terraces, 

mudlines, and the channel bed reported in Cooley and 

others (1977, fig. 36) indicated no net aggradation or 

deposition in the intervening 18 years. Relocation of the 

sites (especially Cooley and others, 1977, fig. 34C) revealed local channel widening upstream from the bend. 

Although the channel changed slightly between 1967 and 

1986, no evidence for post-1966 debris flows was found 

at this site.

We surveyed a longitudinal profile of mudlines and 

measured an elevation difference of 22.7 ft between lines 

on the inside and outside of the bend (table 8). The 

longitudinal profile (fig. ISA) shows an increase in the 

slope of the channel bed at the start of the bend that may 

have affected the flow regime. The mescal pit at this site 

(Cooley and others, 1977) was narrowly missed by a lowerstage superelevation on an upstream bend (fig. ISA).

Mean velocity on the larger bend was calculated to be 17.7 

ft/s. Surveyed cross sections indicate that the area at the 

highest superelevation marks is nearly three times larger 

than upstream and downstream areas (table 8). On the 

basis of an average area of upstream and downstream 

cross sections, we calculated a discharge of 14,000 ft3/s 

for the 1966 debris flow, although we estimate a numerical 

uncertainty of between 11,900 and 15,400 ft3/s. The 

water content of the flow, reconstituted from a sample 

taken 0.3 mi downstream, was 24 to 26 percent by volume. 

At site G, 0.9 mi upstream from the Colorado River, 

superelevation and runup marks were preserved on the 

walls of Vishnu Schist and in cacti. Superelevation 

evidence (fig. 185) was used to calculate a mean velocity 

of 10.3 ft/s (table 9). However, mean velocities calculated 

from runup evidence at two points (fig. 18B) were 15.0 

and 15.4 ft/s. As noted at all other superelevation sites, 

the area of cross sections measured near superelevation

FIGURE 17. Crystal Rapid at the mouth of Crystal Creek. The poor visual quality of view A (May 1966) results from deterioration of the original 

color slide. Note the small debris fan and smooth tongue of water entering the rapid at right center of the river. The discharge of the Colorado 

River is 16,000 cubic feet per second. In view B (April 1986), the tongue of the rapid has been forced to the left as a result of the debris 

fan deposited during the debris flow of 1966. The discharge of the Colorado River is 28,500 cubic feet per second.
SIMILARITIES AND CONTRASTS AMONG THE DRAINAGES 21

marks were significantly larger than the areas of cross 

sections upstream and downstream from the marks (table 

9). We estimated a discharge of between 9,200 and 13,500 

ft 3/s for the debris flow on the basis of the range in 

velocities and cross-sectional areas. The water content of 

the flow, reconstituted from a sample taken 0.1 mi downstream, was 31 to 33 percent by volume.

Particle-size distributions (fig. 16) show that extremely 

coarse, poorly sorted sediments were transported during 

the debris flow of 1966. The sediments contained 10- to 

15-percent sand and 5- to 10-percent silt and clay (fig. 16); 

different samples had similar particle-size distributions 

except in a coarse facies found 0.9 mi above the Colorado 

River. Boulders 7 ft in diameter were common in levee 

deposits. One boulder measured at site G was a rectangular block that had dimensions of 14x7x6 ft and 

weighed an estimated 49 tons. Nine other boulders on this 

0.1-mile-long levee had intermediate diameters in excess 

of 5 ft. Similar-sized boulders are found in the debris fan 

at the mouth of Crystal Creek (S.W. Kieffer, U.S. 

Geological Survey, written commun., 1986).

SIMILARITIES AND CONTRASTS AMONG THE DRAINAGES

The debris flows of 1966 in the Crystal Creek and LavaChuar Creek drainages and the debris flow of 1984 in the 

Monument Creek drainage have similar characteristics. 

The debris flows all were initiated by slope failures in the 

Hermit Shale and the Esplanade Sandstone during an intense storm event. All three debris flows transported a 

poorly sorted mixture of clay- to boulder-size particles in 

slurries. Water contents ranged from 23 to 33 percent 

during the initial peak. The flows were followed by recessional debris and (or) hyperconcentrated flows that 

deposited distinctive sawtooth-shaped levees on the flood 

plain. Peaks of the debris flows reached the Colorado 

River, and two of the three debris flows caused significant constrictions of the Colorado River at the tributary 

mouth.

Our limited data suggest an important mechanism of 

channel adjustment following debris flows that reached 

the Colorado River. As illustrated by the stratigraphy in 

Tapeats Narrows of Dragon Creek (fig. 14), not all debris

FIGURE 17. Continued.
22 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

flows reach the Colorado River. Small debris flows fill the 

headwater channels with sediments after they stop flowing and raise the bed elevation by tens of feet. Subsequent 

flows of larger volume may be able to erode through this 

stored sediment and incorporate it into the moving fluid. 

Smaller debris flows may prime the channel for larger 

debris flows that have sufficient volume of sediments to 

reach the Colorado River.

We determined a significant problem with the measurement of the effective flow area of debris flows at all sites 

where discharges were estimated. The cross-sectional 

areas at the superelevation marks are 1.3 to 3.6 times 

larger than upstream or downstream areas (table 10). 

Discharges calculated using the areas at superelevation

marks, therefore, are 1.3 to 3.6 times larger than those 

calculated using the upstream and downstream areas 

(table 10). If the cross sections at the superelevation 

marks are used, continuity of flow (equation 4) implies 

substantially higher velocities on the approaches and exits 

to the bends. Using site F in the Lava-Chuar Creek 

drainage as an example, the exit velocity would be 43 ft/s 

if the cross-sectional area at the superelevation marks 

were fully effective during the peak of the debris flow. 

The velocity would have increased 31 ft/s in 250 ft with 

no significant slope change under these conditions.

Discharges were estimated from upstream and (or) 

downstream cross-sectional areas and assumed that the 

velocity was not significantly changed through the bend

no

100

90

80 

70

Smoll bend neor 

roasting pit

ui 60 

> 40 

o

CD

80 120 160 200 240 280 320 360 400

DISTANCE ON THALWEGJN FEET

440 480 520 560

40 120 160 200 240 280 

DISTANCE ON THALWEG.IN FEET

320 360 400

EXPLANATION

Channel-bed elevation 

I Cross-section location

 Inside-bend debris-flow surface

 Outside-bend debris-flow surface

FIGURE 18. Longitudina1 profiles for indirect-discharge sites in the Crystal Creek drainage. A, Site F, 4.8 miles upstream 

from the Colorado River. B, Site G, 0.9 mile upstream from the Colorado River.
FLUVIAL EVENTS IN OTHER DRAINAGES 23

by energy losses. Several hydraulic properties of debris 

flows can be used to support the latter assumption. 

Because of their cohesive nature, debris flows may have 

large ineffective flow areas consisting of static sediment 

on the margins of channel bends. Superelevation formulae 

are used to calculate not only a mean velocity across a 

cross section but also a mean velocity around part of the 

bend. For example, Apmann (1973) uses the curvature 

angle of the bend in his formula, implying that superelevation is a function of both longitudinal and mean crosssectional velocity. Finally, the low turbulence and high 

momentum of debris flows probably reduces longitudinal 

variations in velocity. Calculation of velocities of debris 

flows using superelevation evidence appears to involve 

a considerable error that could not be estimated in this 

study.

The three drainages that we studied had different frequencies for debris flows reaching the Colorado River. We 

could not estimate a true magnitude-frequency relation 

because we estimated discharges only for a single flow 

in each drainage. Relative stages of successive debris 

flows were determined; however, channel changes between events may have changed the stage-discharge relation for the channel. The Lava-Chuar Creek drainage had 

the most frequent debris flows that reached the Colorado 

River with an average of one event every 20 to 30 years. 

Monument Creek had at least two debris flows this century, and they both occurred within 25 years. Crystal 

Creek had only one debris flow reaching the Colorado 

River this century and averages a minimum of one debris 

flow every 50 years that reaches the Colorado River.

The size of transported boulders varied considerably 

among the drainages. The largest boulder transported by 

the debris flow of 1966 in the Lava-Chuar Creek drainage 

weighed an estimated 9 tons. Boulders that were transported in the Monument and Crystal Creek drainages 

weighed an estimated 37 and 49 tons, respectively. In all 

drainages, larger boulders may have been transported 

into the Colorado River. The sand content of the flows 

ranged from 10 to 40 percent and represents a potentially significant source for beach sands along the Colorado 

River.

FLUVIAL EVENTS IN OTHER DRAINAGES

As previously stated, debris flows are common 

phenomena in Grand Canyon National Park. Individual 

drainages such as Lava-Chuar Creek may average 20 to 

30 years between debris flows that reach the Colorado 

River; in the park as a whole, however, such flows occur 

much more frequently. We gathered historical information and analyzed aerial photography from 1965, 1973, 

and 1984 to compile a list of historical fluvial events from 

ungaged tributaries that have affected their debris fans 

at the Colorado River (table 11). We also list known

historic debris flows and floods in table 11. The list is not 

all inclusive, because more than one flow could have induced the changes and not all floods were debris flows. 

However, the list provides a perspective on the frequency 

of fluvial events, many of which were debris flows, between 1965 and 1986.

In the historical record, the summer of 1983 probably 

was the most significant year for fluvial events from 

ungaged tributaries. Rainfall was above average during 

July and August. On July 25, Grand Canyon, Bright Angel 

Ranger Station, and Phantom Ranch had 3.14, 2.02, and 

1.85 in of rainfall, respectively. No intensity data are 

available for this storm; however, the daily totals suggest 

pervasive storms in the Grand Canyon on July 25. Almost 

all the drainages between Colorado River mile 42 and mile 

77 had flash floods during the summer of 1983 (table 11), 

possibly during the storm on July 25. Sediment-sampling 

data from the gaging station on the Colorado River at 

Phantom Ranch shows small peaks in sediment during 

July and August 1983, which may be attributable to these 

floods.

A winter storm in December 1966 caused widespread 

flooding within Grand Canyon National Park (Cooley and 

others, 1977). A storm originating in the north Pacific 

Ocean traveled slowly over northern Arizona and southern Utah between December 3 and 6 (Butler and Mundorff, 1970). Floods on the Virgin River in southern Utah 

exceeded the 100-year event (Butler and Mundorff, 1970), 

suggesting that this type of storm is rare. Precipitation 

totaling 11 to 14 in. fell on the North Rim (Cooley and 

others, 1977), triggering floods in Bright Angel Creek and 

several other drainages with headwaters on the Kaibab 

Plateau. The debris flows in the Lava-Chuar and Crystal 

Creek drainages (see "Debris Flows in Three Tributaries 

of the Colorado River") and ten other debris flows not 

reaching the Colorado River were initiated during this 

storm (Cooley and others, 1977).

In July 1984, a debris flow with a stage of greater than 

7 ft and width of 200 ft struck two 20-ton trucks stalled 

in the channel of Diamond Creek about 0.5 mi upstream 

from the Colorado River (Mike Walker, boatman, O.A.R.s, 

Modesto, California, oral commun., 1986). The trucks 

were carried into the river and later were found more than 

1,000 ft downstream on the opposite bank. Boulders 4 to 

5 ft in diameter were transported by the debris flow, 

which remained at uncrossable levels for 6.5 hrs. The 

debris flow reportedly caused 30-foot-high spray upon impact with the Colorado River and greatly enlarged the 

debris fan.

This brief history indicates that several storm types may 

initiate fluvial events, which include debris flows, in the 

Grand Canyon. Summer thunderstorms appear to be the 

most common type of storm that initiates debris flows. 

These storms generally are localized in one or two adja-
24 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

cent drainages and can be considered as random in time. 

Intense precipitation resulting from winter frontal storms 

also may initiate debris flows; however, this type of storm 

generally is rare.

FACTORS RESPONSIBLE FOR DEBRIS FLOWS

The bedrock geology of Grand Canyon National Park 

controls the location of the initiation sites for debris flows 

in tributaries of the Colorado River. The Grand Canyon 

is noted for spectacular cliffs of sedimentary rocks, and 

the combination of stratified rocks with different strength 

properties and high relief leads to a high potential for 

slope failures (Rogers and Pyles, 1979). In addition, fault 

planes control the location of drainages in Grand Canyon 

(Dolan and others, 1978; Potochnik and Reynolds, 1986), 

and the resultant shear zones provide abundant loose and 

poorly sorted material for debris-flow initiation. Abundant 

talus accumulates locally beneath cliff faces, providing a 

source for debris mobilization during intense storm 

events. The Grand Canyon is, in fact, an ideal location for 

debris flows.

The most common cause for debris flows is slope failures 

in the Hermit Shale and Supai Group throughout the 

Grand Canyon. In the only systematic mapping of slope 

failures, Cooley and others (1977) mapped 93 slope failures 

that occurred during the storm of 1966. Seventy percent 

were from the Hermit Shale and Supai Group; 19 percent 

from the Kaibab Limestone and underlying Toroweap 

Formation, or Coconino Sandstone; and 11 percent from 

the Muav Limestone. Most of these failures resulted in 

local debris flows, and failures in the Hermit Shale and 

the Supai Group initiated debris flows in the Lava-Chuar 

and Crystal Creek drainages that reached the Colorado 

River.

The composition and chemistry of the Hermit Shale and 

Esplanade Sandstone have the potential to generate 

debris flows. The Esplanade Sandstone at the top of the 

Supai Group consists of alternating layers of sandstone, 

siltstone, and mudstone and forms a morphologically 

distinct series of basal slope, cliff, and upper slope (McKee, 

1982). This formation is of continental origin, which 

contrasts with the marine origin of the other three formations of the Supai Group. Swelling clays, notably smectites and montmorillonites, are abundant in these rocks 

(McKee, 1982) and cause rapid weathering of the cliffs 

into potentially mobile talus. Both the Hermit Shale and 

Esplanade Sandstone contain dispersive clays, which 

disintegrate into colloidal suspension when water is added 

(J.D. Rogers, Rogers/Pacific Consultants, Lafayette, 

California, oral commun., 1986). When these rocks are 

located on top of cliffs of Redwall Limestone, catastrophic 

slope failures are possible as the rocks weather.

The combination of alternating rock types, dispersive 

clays, and the high relief in the drainage basins make

canyons with exposures of Hermit Shale and Esplanade 

Sandstone particularly susceptible to debris flows. The 

proximity of these rocks to the Colorado River may explain some of the longitudinal spacing of rapids. The Roaring Twenties (fig. 1) are a series of closely spaced, 

moderate-size rapids that occur where the Hermit Shale 

and Supai Group are first elevated above the river. In contrast, few moderate to large rapids occur between Kanab 

Creek and Prospect Creek (fig. 1), possibly because the 

Hermit Shale and most of the Esplanade Sandstone have 

been stripped from the nearby cliffs.

Several drainages exemplify other sources of sediments 

for debris-flow mobilization in Grand Canyon National 

Park. Red Canyon (fig. 1) has formed at the intersection 

of several major faults, and two large landslide deposits 

have been mapped in its headwaters (Huntoon and others, 

1986). Hance Rapid is formed where a debris fan from 

Red Canyon forces the Colorado River against a bedrock 

wall. Large boulders in the channel cause severe navigational difficulties at low water (Stevens, 1983). Debris 

flows from Red Canyon have occurred relatively frequently in geologic time as indicated by the large debris fan, 

multiple levees, and exposed debris-flow stratigraphy. The 

large landslides and shear zones in the headwaters are 

the probable source of sediments for the debris flows.

Lava Falls Rapid, generally regarded as the most difficult to navigate on the Colorado River (Collins and Nash, 

1978), is formed by debris transported from Prospect 

Creek (fig. 1) and not by outcrops of resistant rocks 

(Leopold, 1969). Four large basalt boulders form the infamous Ledge Hole in the center of the rapid. The fan 

at the mouth of Prospect Creek consists of four inset terraces, each of which is composed of multiple debris-flow 

deposits. The source of sediments for debris flows is the 

loose basalt talus in the shear zone of the Toroweap fault 

about 1 mi from the Colorado River (Huntoon and others, 

1981). Discharges in Prospect Creek cascade over a 

1,200-foot cliff and initiate slope failures in the loose talus.

The occurrence of debris flows is not controlled by an 

obvious basin morphometric factor in Grand Canyon 

National Park. Similar adjacent basins appear to have 

completely different histories of debris flows. For example, Monument Creek has had two debris flows that 

reached the Colorado River in 25 years and Hermit Creek, 

slightly larger in size and abutting Monument Creek on 

the west, has had no obvious debris flows that reached 

the river during the same period. Although the storm of 

December 1966 initiated a debris flow in the Crystal Creek 

drainage, the adjacent and larger Shinumo Creek 

drainage had only small debris flows in its headwaters, 

and only streamflow reached the Colorado River (Cooley 

and others, 1977). Clearly, debris flows that reach the 

Colorado River are a random occurrence controlled by the 

combination of accumulation rates of sediment available 

for transport and intense storm events.
HYDROLOGIC EFFECT OF DEBRIS FLOWS ON THE COLORADO RIVER 25

An attempt was made to explain the navigational 

difficulty and water-surface fall through 67 rapids of the 

Colorado River on the basis of contributing drainage areas 

of tributaries (table 12). Although navigational difficulty 

and water-surface fall through a rapid are not good predictors of the frequency or size of debris flows from the 

tributaries, they are the only known characteristics available for the entire Colorado River corridor. Drainagebasin area is the hydrologic variable most commonly used 

to assess regional flood and sediment-transport potential. 

All rapids with a maximum rating greater than 4 (Stevens, 

1983) are included with the exception of Lower Lava 

Rapid, which is controlled by outwash debris from Lava 

Falls Rapid and Prospect Creek, and Nixon Rock Rapid, 

which is controlled by rockfalls. Selected rapids with a 

maximum rating of 4 or less were also included (table 12). 

With the exception of the Paria and Little Colorado 

Rivers, all drainages included had obvious debris-flow 

deposits at the Colorado River.

Drainage areas of contributing tributaries do not explain either water-surface fall or navigational difficulty 

of rapids on the Colorado River (fig. 19). Local channel 

factors also cannot explain these variables because rapids 

with similar navigational difficulties have different watersurface falls and constriction ratios (S.W. Kieffer, U.S. 

Geological Survey, written commun., 1986). Local channel conditions such as bedrock spurs and confining-wall 

geometry may exacerbate a rapid. We attribute the noncorrelation of drainage area and rapid difficulty to the 

overwhelming control of rapid difficulty by local factors 

in each contributing drainage, particularly the size of 

debris-flow-transported boulders, the history of debris 

flows, and local channel conditions.

HYDROLOGIC EFFECTS OF DEBRIS FLOWS ON 

THE COLORADO RIVER

The magnitude and frequency of debris flows control 

the hydraulics of the Colorado River in Grand Canyon 

National Park. Debris flows from small tributaries aggrade fans which typically force the river against the 

opposite wall of the canyon (fig. 20). In some cases, debris 

fans from tributaries on opposite sites of the river, such 

as the Lava-Chuar Creek drainage and Palisades Creek, 

constrict the Colorado River without a directional change. 

Debris flows deposit very large boulders in the river that 

cannot be moved by ordinary discharges. Therefore, 

rapids tend to be maintained as hydraulic controls on the 

river until the boulders can be moved by rare, large 

discharges (Graf, 1979). The ability of small drainages 

such as Monument Creek to control the hydraulics of one 

of the largest rivers in the United States is of great 

hydrologic significance.

The combination of a debris fan and the increased 

velocity of flow in the rapid creates flow-separation zones

conducive to the formation of beaches (Schmidt and Graf, 

1988). Constriction ratios at debris fans range from 0.3 

to 0.7 (Kieffer, 1985), and separation zones (and consequently beaches) form upstream and downstream from 

rapids. The combination of sudden channel expansion and 

rapid deceleration of flow below rapids induces the 

recirculating-eddy systems common in Grand Canyon 

National Park (Schmidt and Graf, 1988). Debris-flow 

transport of boulders onto the fan surfaces is the key 

process in creating the system of flow separations on the 

Colorado River.

Control of local channel hydraulics extends beyond the 

rapid and debris-fan system. Prominent debris bars, 

referred to as islands or rock gardens, are formed downstream from the rapid by reworking of the debris fans 

after a debris flow. Commonly on the opposite side of the 

river from the tributary, these bars generally are composed of well-sorted, imbricated cobbles and boulders 

mixed with sand. At Crystal Creek, the rock garden was

o

z 

p

IT

-

3

n 

10

Q

8

7

6

5

4

3

2

1

0 

30

25

20

15

10

5 

0

0.

 i i mil.; -. ...in, i ii ! ' " "! ' ' '""1 ' ' """

-A

- . .

. ... . .

.. MM...

. ........

........

.... 

-

B

<-

. .

.. . . .

"."."".

.... ,...i .... ....i , . , . ....* . . . .....i , . . .....i , ..,.,,.

01 O.i 1 10 100 1,000 10,

DRAINAGE AREA,IN SQUARE MILES

FIGURE 19. Relation of characteristics of rapids and the contributing 

drainage area of the tributaries. A, Using the "rapid rating" (scale 

of 1 to 10; Stevens, 1983) for a discharge of 10,000 cubic feet per second 

in the Colorado River. B, Using the water-surface fall surveyed in 1921 

and adjusted to 10,000 cubic feet per second. This fall may have 

significantly changed as a result of historic debris flows, especially 

at Crystal Rapid.
26 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

greatly enlarged after the debris flow of 1966 and contains boulders that are unusually large for a debris bar. 

At Monument Creek, the island enlarged slightly after 

the 1984 debris flow. An island in the Colorado River at 

river mile 66 (Stevens, 1983) appears to be maintained 

by periodic debris flows from the Lava-Chuar Creek 

drainage and Palisades Creek. Debris bars, particularly 

in the form of islands, provide a control on the longitudinal 

extent of eddy systems. Large debris bars induce secondary riffles or rapids, such as Lower Lava Rapid at river 

mile 179.8, that may be additional navigational hazards 

or form secondary flow-separation zones.

Debris flows from tributaries have important influences 

on sediment transport in the Colorado River. Although 

the debris flows occur infrequently, they are the source 

of large volumes of sand that enter at discrete points along 

the river. Debris flows transport boulders into the Colorado River that create the hydraulic controls that are 

prominent in the longitudinal profile of the river (Howard 

and Dolan, 1981). Debris fans and bars control the formation and longitudinal extent of separation zones needed 

to trap sand. A thorough understanding of the magnitude 

and frequency of debris flows is of paramount importance

(Modified from Hamblinond Rig by ,1968)

EXPLANATION

1 Tributary debris fan

2 Rapid controlled by large immobile boulders

3 Debris bar (synonymous with "island" or "rock garden")

4 Riffle or rapid caused by debris bar

FIGURE 20. Geomorphic features of a typical rapid controlled by debris 

flows on the Colorado River.

to understanding and long-term estimates of sediment 

transport in the Colorado River in Grand Canyon National 

Park.

SUMMARY

Sediment transported from small drainages is a potentially large source of sand for beaches on the Colorado 

River in Grand Canyon National Park. Previous flood 

reports (Cooley and others, 1977) and recent mapping of 

alluvial deposits in tributary canyons during this project 

indicate that debris flows are a major process of sediment 

transport in small drainages in Grand Canyon National 

Park. Debris flows are common in arid and semiarid 

regions, but their importance in supplying sediment to the 

Colorado River has not been previously recognized.

We observed debris-flow deposits in all 36 tributaries 

of the Colorado River that were examined during this 

study. Twenty-one of the 36 tributaries have evidence for 

debris flows within the last 25 years. We selected three 

tributaries for more detailed study on the basis of previous 

reports of debris flows. The tributaries studied in detail 

are the Lava-Chuar Creek drainage at Colorado River 

mile 65.5, the Monument Creek drainage at river mile 

93.5, and the Crystal Creek drainage at river mile 98.2. 

Evidence for at least five prehistoric debris flows and 

three historic debris flows is preserved in the Lava-Chuar 

Creek drainage. Historic debris flows occurred between 

1973 and 1984, in December 1966, and between 1916 and 

1966. Debris flows have reached the Colorado on the 

average every 20 to 30 years since 1916 and every 190 

years over the last 1,500 years. Debris flows may reach 

the Colorado River more frequently because not all 

prehistoric debris flows may have overtopped the terraces 

to leave depositional evidence.

The debris flow of 1966 in the Lava-Chuar Creek drainage had a velocity of 12 ft/s and a discharge of about 4,000 

ft 3/s near the Colorado River. The debris flow began at 

slope failures in the Hermit Shale and Supai Group and 

traveled 6.5 mi to the Colorado River. The water content 

of the flow was estimated at 22.5 percent and yielded sediment and water discharges of 3,100 and 900 ft3/s, respectively. The debris flow had 30 to 35 percent sand and 

carried boulders 1 to 2 ft in diameter. The largest boulder 

measured that was transported during the 1966 debris 

flow weighed an estimated 9 tons.

Two debris flows have occurred in the last 25 years in 

the Monument Creek drainage. A storm on July 27,1984, 

initiated an avalanche and subsequent debris flow that 

reached the Colorado River. Scanty evidence suggests an 

earlier debris flow that occurred in the early 1960's. Older 

debris-flow deposits were radiometrically dated at about 

A.D. 1780, but lack of correlation with downstream 

deposits precluded any use of this date for determining 

frequencies of events.
REFERENCES CITED 27

The debris flow of 1984 in Monument Creek began as 

an avalanche from the Esplanade Sandstone of the Supai 

Group 2,000 ft above the channel. A 20-foot high avalanche deposit still dammed the channel in 1986. The 

debris flow traveled 2.8 mi to the Colorado River at a 

velocity of 11 to 13 ft/s and a peak discharge of about 

3,800 ft 3/s. The water content of the flow ranged from 

27 to 34 percent and the flow was composed of 30 to 40 

percent sand. One boulder transported during the flow 

weighed an estimated 37 tons.

The debris flow of 1984 created a new fan surface at 

the Colorado River that significantly constricted Granite 

Rapid. We estimated the volume of sediment transported 

onto the fan and into the river on the basis of hypothesized scenarios of post-debris-flow fan geometry. The most 

likely volume of sediment transported onto the fan and 

into the river is 300,000 ft 3. The absence of particles less 

than 16 mm in diameter on the debris fan in 1986 suggests that all finer particles including sand were quickly 

transported into the Colorado River. By assuming an 

average sand content of 35 percent, the estimated volume 

of sand that entered the river is 84,000 ft 3 with a range 

of 56,000 to 150,000 ft 3 for the scenarios that were considered. From the volume of sediment moved and the 

discharge estimated upstream, we estimated that the fan 

was created during the first pulse of the debris flow in 

1 to 3 minutes.

The Crystal Creek drainage has averaged a minimum 

of one debris flow that reached the Colorado River every 

50 years. A large debris flow in 1966 has been the only 

debris flow to reach the Colorado River in this century. 

Small debris flows, on reaching the Colorado River, have 

significantly aggraded the channel in the past, possibly 

storing sediments available to larger debris flows capable 

of reaching the river.

The debris flow of 1966 in the Crystal Creek drainage 

began at 11 slope failures in the Hermit Shale and Supai 

Group and traveled 13 mi to the Colorado River. The 

calculated flow velocity ranged from 10 to 18 ft/s, and the 

discharge ranged from 9,200 to 14,000 ft 3/s. The water 

content of the flow ranged from 24 to 33 percent, and the 

sediments had a sand content of 10 to 15 percent. One 

boulder transported by the debris flow weighed an 

estimated 49 tons, and boulders with diameters in excess 

of 5 ft were commonly transported. Upon reaching the 

Colorado River, the debris flow created a new fan surface that significantly constricted the Colorado River.

The debris flows studied had similarities that indicate 

the cause and nature of debris flows in Grand Canyon 

National Park. All three debris flows were initiated at 

slope failures in the Hermit Shale and Supai Group, 

especially the Esplanade Sandstone. All debris flows 

transported a poorly sorted mixture of clay- to bouldersized particles with water contents ranging from 23 to

33 percent by volume. The largest boulders transported 

ranged from 9 tons in the Lava-Chuar Creek drainage to 

37 and 47 tons in the Monument Creek and Crystal Creek 

drainages, respectively. Two of the three debris flows 

significantly constricted the Colorado River at the tributary mouths. The frequency of debris flows that reach the 

Colorado River is tentative, but the available data suggest one flow reached the Colorado River every 20 to 50 

years in these drainages. A compilation of the scanty 

historical information on flow events from Grand Canyon 

tributaries, however, indicates that debris flows occur 

more frequently throughout the park.

The bedrock geology of Grand Canyon National Park 

provides an ideal location for the initiation of debris flows. 

The high relief combined with differential strength properties of the rocks leads to a high potential for slope 

failures. The most common source of mobilized sediments 

for debris flows are the Hermit Shale and Esplanade 

Sandstone of the Supai Group. Other sources include the 

Kaibab Limestone, Toroweap Formation, and Coconino 

Sandstone; Muav Limestone and Bright Angel Shale; and 

Quaternary basalts in the western Grand Canyon. Dispersive and swelling clays in some of these formations aid 

in the initiation of debris flows.

The magnitude and frequency of debris flows control 

the hydraulics of the Colorado River in Grand Canyon 

National Park. Debris flows from the small tributaries 

aggrade fans that typically force the river against the 

opposite wall of the canyon. The ability of small drainages 

such as Monument Creek to form hydraulic controls 

(rapids) on one of the largest rivers in the United States 

is of great hydrologic significance. The debris fans also 

cause flow separation zones conducive to deposition and 

storage of sand on beaches, and reworking of debris fans 

by Colorado River discharges creates secondary riffles or 

rapids. Debris flows are the source of large volumes of 

sand entering the river at discrete points, although the 

debris flows occur infrequently. A thorough understanding of the magnitude and frequency of debris flows is of 

paramount importance to any understanding or long-term 

estimates of sediment transport in the Colorado River in 

Grand Canyon National Park.

REFERENCES CITED

Apmann, R.P., 1973, Estimating discharge from superelevation in bends: 

American Society of Civil Engineers, Journal of the Hydraulics Division, v. 99, p. 65-79.

Beverage, J.P., and Culbertson, J.K., 1964, Hyperconcentrations of 

suspended sediment: American Society of Civil Engineers, Journal 

of the Hydraulics Division, v. 90, p. 117-126.

Blackwelder, Eliot, 1928, Mudflow as a geologic agent in semiarid mountains: Geological Society of America Bulletin, v. 39, p. 465-494.

Butler, Elmer, and Mundorff, J.C., 1970, Floods of December 1966 in 

southwestern Utah: U.S. Geological Survey Water-Supply Paper 

1870-A, 40 p.
28 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

Chen, Cheng-lung, 1985, Hydraulic concepts in debris flow simulations, 

in Bowles, D.S., editor, Delineation of landslide, flash flood, and 

debris flow hazards in Utah: Logan, Utah, Utah Water Research 

Laboratory, General Series, UWRL/G-85/03, p. 236-259.

Chow, V.T., 1959, Open-channel hydraulics: New York, McGraw-Hill, 

680 p.

Collins, R.O., and Nash, R., 1978, The big drops: San Francisco, California, Sierra Club Books, 215 p.

Cooley, M.E., Aldridge, B.N., and Euler, R.C., 1977, Effects of the 

catastrophic flood of December, 1966, North Rim area, eastern 

Grand Canyon, Arizona: U.S. Geological Survey Professional Paper 

980, 43 p.

Costa, J.E., 1984, Physical geomorphology of debris flows, in Costa, 

J.E., and Fleisher, P.J., editors, Developments and applications of 

geomorphology: Berlin, Springer-Verlag Publishing, p. 268-317.

Costa, J.E., and Jarrett, R.D., 1981, Debris flows in small mountain 

stream channels of Colorado and their hydrologic implications: 

Bulletin of the Association of Engineering Geologists, v. 18, p. 

309-322.

Dolan, Robert, Howard, Alan, and Trimble, David, 1978, Structural control of the rapids and pools of the Colorado River in the Grand 

Canyon: Science, v. 202, p. 629-631.

Enos, Paul, 1977, Flow regimes in debris flow: Sedimentology, v. 24, 

p. 133-142.

Fisher, R.V., 1983, Flow transformations in sediment gravity flows: 

Geology, v. 11, p. 273-274.

Gallino, G.L., and Pierson, T.C., 1985, Polallie Creek debris flow and 

subsequent dam-break flood of 1980, East Fork Hood River basin, 

Oregon: U.S. Geological Survey Water-Supply Paper 2273, 22 p.

Graf, W.L., 1979, Rapids in canyon rivers: Journal of Geology, v. 87, 

p. 533-551.

Hamblin, W.K., and Rigby, J.K., 1968, Guidebook to the Colorado River, 

Part 1 Lees Ferry to Phantom Ranch in Grand Canyon National 

Park: Provo, Utah, Brigham Young University Geology Studies, v. 

15, part 5, 84 p.

Hooke, R.L., 1967, Processes on arid-region alluvial fans: Journal of 

Geology, v. 75, p. 438-460.

Howard, Alan, and Dolan, Robert, 1981, Geomorphology of the Colorado 

River in Grand Canyon: Journal of Geology, v. 89, p. 269-297.

Hungr, 0., Morgan, G.C., and Kellerhals, Rolf, 1984, Quantitative 

analysis of debris torrent hazards for design of remedial measures: 

Canadian Geotechnical Journal, v. 21, p. 663-677.

Huntoon, P.W., Billingsley, G.H., Jr., and Clark, M.D., 1981, Geologic 

map of the Hurricane Fault Zone and vicinity, western Grand 

Canyon, Arizona: Flagstaff, Arizona, Grand Canyon Natural History 

Association map, scale 1:48,000, 1 sheet.

Huntoon, P.W., Billingsley, G.H., Jr., Breed, W.J., Sears, J.W., Ford, 

T.D., Clark, M.D., Babcock, R.S., and Brown, E.H., 1986, Geologic 

map of the eastern part of the Grand Canyon National Park, Arizona: 

Flagstaff, Arizona, Museum of Northern Arizona Special Publication map, 1 sheet, scale 1:62,500.

Hupp, C.R., 1984, Dendrogeomorphic evidence of debris flow frequency and magnitude at Mount Shasta, California: Environmental 

Geology and Water Science, v. 6, p. 121-128.

Johnson, A.M., and Rodine, J.R., 1984, Debris flow, in Brunsden, D., 

and Prior, D.B., editors, Slope instability: New York, John Wiley 

and Sons, p. 257-361.

Kellerhals, Rolf, and Bray, D.I., 1971, Sampling procedures for coarse 

fluvial sediments: American Society of Civil Engineers, Journal of 

the Hydraulics Division, v. 97, p. 1165-1180.

Kieffer, S.W., 1985, The 1983 hydraulic jump in Crystal RapidImplications for river-running and geomorphic evolution in the Grand 

Canyon: Journal of Geology, v. 93, p. 385-406.

Laenen, Antonious, Scott, K.M., Costa, J.E., and Orzol, L.L., 1987, 

Hydrologic hazards along Squaw Creek from a hypothetical failure 

of a glacial moraine impounding Carver Lake near Sisters, Oregon: 

U.S. Geological Survey Open-File Report 87-41, 48 p.

Laursen, E.M., Ince, Simon, and Pollack, Jack, 1976, On sediment 

transport through the Grand Canyon, in Proceedings of the Third 

Inter-Agency Sedimentation Conference, Denver, Colorado, p. 4-76 

to 4-87.

Leopold, L.B., 1969, The rapids and pools Grand Canyon, in The 

Colorado River Region and John Wesley Powell: U.S. Geological 

Survey Professional Paper 669, p. 131-145.

McKee, E.D., 1969, Stratified rocks of the Grand Canyon, in The 

Colorado River Regions and John Wesley Powell: U.S. Geological 

Survey Professional Paper 669, p. 23-58.

___ 1982, The Supai Group of Grand Canyon: U.S. Geological Survey 

Professional Paper 1173, 504 p.

Pacific Southwest Inter-Agency Committee, 1968, Factors affecting sediment yield and measures for the reduction of erosion and sediment 

yield: Pacific Southwest Inter-Agency Committee Report, 23 p.

Pierson, T C., 1980, Erosion and deposition by debris flows at Mt 

Thomas, North Canterbury, New Zealand: Earth Surface Processes, 

v. 5, p. 227-247.

___ 1981, Dominant particle support mechanisms in debris flows at 

Mt Thomas, New Zealand, and implications for flow mobility: 

Sedimentology, v. 28, p. 49-60.

1985, Initiation and flow behavior of the 1980 Pine Creek and

Muddy River lahars, Mount St.Helens, Washington: Geological 

Society of America Bulletin, v. 96, p. 1056-1069.

Pierson, T.C., and Scott, K.M., 1985, Downstream dilution of a lahar 

Transition from debris flow to hyperconcentrated streamflow: Water 

Resources Research, v. 21, p. 1511-1524.

Piper, D.J.W., Farre, J.A., and Shor, A., 1985, Late Quaternary slumps 

and debris flows on the Scotian slope: Geological Society of America 

Bulletin, v. 96, p. 1508-1517.

Postma, George, 1986, Classification for sediment gravity-flow deposits 

based on flow conditions during sedimentation: Geology, v. 14, p. 

291-294.

Potochnik, A.R., and Reynolds, S.J., 1986, Geology of side canyons of 

the Colorado, Grand Canyon National Park: Arizona Bureau of 

Geology and Mineral Technology Fieldnotes, v. 16, p. 1-8.

Rogers, J.D., and Pyles, M.R., 1979, Evidence of catastrophic erosional 

events in the Grand Canyon of the Colorado River, Arizona, in Proceedings of the 2nd Conference on Scientific Research in the National 

Parks, 26-30 November, San Francisco, California [reprint].

Schmidt, J.C., and Graf, J.B., 1988, Aggradation and degradation of 

alluvial sand deposits, 1965 to 1986, Colorado, River, Grand Canyon 

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

87-555, 120 p.

Scott, K.M., 1985, Lahars and lahar-runout flows in the Toutle-Cowlitz 

River system, Mount St. Helens, Washington Origins, behavior, 

and Sedimentology: U.S. Geological Survey Open-File Report 85-500, 

202 p.

Smith, G.A., 1986, Coarse-grained nonmarine volcaniclastic sedimentTerminology and depositional process: Geological Society of America 

Bulletin, v. 97, p. 1-10.

Stevens, Larry, 1983, The Colorado River in Grand Canyon: Flagstaff, 

Arizona, Red Lake Books, 107 p.

Taylor, R.E., Donahue, D.J., Zabel, T.H., Damon, P.E., and Jull, A.J.T., 

1984, Radiocarbon dating by particle accelerators An archaeological perspective: American Chemical Society Advances in 

Chemistry Series, no. 205, Archaeological Chemistry, v. Ill, p. 

333-356.
TABLES 1-12
30 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

TABLE I. Selected tributaries of the Colorado River, Grand Canyon National Park

[X indicates that the attribute listed in the column heading was either 

observed or measured in the drainage.]

Tributary name

19 -Mile Canyon

24.5 Mile Canyon

Shinumo Wash

Buck Farm Canyon

Unnamed canyon

Saddle Canyon

Nankoweap Creek

Lava-Chuar Creek

Palisades Creek

Tanner Canyon

Cardenas Creek

Unkar Creek

75 -Mile Canyon

Red Canyon

Clear Creek

Bright Angel Creek

Monument Creek

Crystal Creek

Shinumo Creek

Elves Chasm

Blacktail Canyon

Forster Canyon

Fossil Canyon

Unnamed canyon

Deer Creek

Kanab Creek

Olo Canyon

Matkatimiba Creek

Havasu Creek

National Canyon

Fern Glen Canyon

Prospect Canyon

Parashant Wash

Fall Canyon

2 20 -Mile Canyon

Diamond Creek

Colorado Ancient 

River debris -flow 

mile 1 deposits

19.0

24.5

29.2

41.0

43.3

47.0

52.2

65.5

65.7

68.5

70.9

72.7

75.5

76.8

84.2

87.9

93.5

98.2

108.6

116.5

120.2

122.8

125.0

127.6

136.1

143.5

145.7

148.0

156.9

166.6

167.9

179.3

198.5

211.6

220.0

225.8

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Recent 

debris -flow 

evidence

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Strati- Events 

graphy analyzed

X

X X

X

X X

X X

X

X

X

X

X

X

x River miles are measured from Lees Ferry (Stevens, 1983).
TABLES 1-12 31

TABLE 2. Indirect-discharge calculation for the debris flow of 1966 on Lava-Chuar Creek, 0.2 mile

upstream from the Colorado River

SUPERELEVATION DATA

Radius of curvature (R ) - 37 feet Channel width (W) - 110 feet 

Elevation difference (Ah ) - 13.32 feet Channel slope (S) - 0.01 to 0.02 

V - 12.0 feet per second (F - 1.0 to 1.4)

CROSS SECTION DATA

Section

Upstream 

Superelevation 

Downstream

Thalweg 

distance 

from superelevation, 

in feet

125 

0 

250

Q - 4,000

Area, in 

square 

feet

350 

1,180 

310

cubic feet per

Hydraulic 

radius , 

in feet

5.1 

9.5 

3.2

second

Hydraulic 

depth, 

in feet

4.7 

10.6 

3.3

TABLE 3. Indirect-discharge calculation for the debris flow of 1984 on Monument Creek at Tapeats 

Alcove, 1.5 miles upstream from the Colorado River

SUPERELEVATION DATA

Radius of curvature (R ) - 75 feet Channel width (W) - 79 feet

Elevation difference (Ah ) - 4.73 feet Channel slope (S) - 0.068

V - 12.0 feet per second (F - 0.6)

CROSS SECTION DATA

Thalweg 

distance

from super- Area, in Hydraulic Hydraulic 

elevation, square radius, depth, 

Section in feet feet in feet in feet

Upstream 95 750 7.1 9.5

Superelevation 0 580 6.0 7.7

Downstream 50 320 6.0 7.4

Q - 4,000 cubic feet per second
32 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

TABLE 4. Indirect-discharge calculations for the debris flow of 1984 on Monument Creek at site B, 

0.5 mile upstream from the Colorado River

SUPERELEVATION DATA

Radius of curvature (R ) - 66 feet Channel width (W) - 65 feet 

c

Elevation difference (Ah ) - 3.73 feet Channel slope (S) - 0.065 feet

s

V - 11.0 feet per second (F - 0.6)

RUNUP DATA 

Elevation difference (Ah ) - 2.05 feet V - 11.5 feet per second (F - 0.6)

CROSS SECTION DATA

Section

Upstream 

Superelevation 

Downstream

Downstream

Average used

Thalweg 

distance

from superelevation, 

in feet

40 

0 

18

90

Q - 3,500 to 4,000

Area , in 

square 

feet

310 

340 

420

330

320

cubic feet

Hydraulic 

radius , 

in feet

5.0 

6.1 

5.2

4.9

per second

Hydraulic 

depth, 

in feet

5.8 

7.6 

6.2

6.0

TABLE 5. Indirect-discharge calculation for the debris flow of 1984 on Monument Creek at site C, 0.3 

mile upstream from the Colorado River

SUPERELEVATION DATA

Radius of curvature (R ) - 125 feet Width (W) - 97 or 106 feet

Elevation difference (Ah ) - 3.41 or 4.57 feet Channel slope (S) = 0.063

V - 11.9 to 13.2 feet per second (F - 1.2 to 1.4)

CROSS SECTION DATA

Thalweg

distance

from super- Area, in Hydraulic Hydraulic 

elevation, square radius, depth, 

Section in feet feet in feet in feet

Downstream 45 320 3.4 3.8 

Q - 3,800 to 4,200 cubic feet per second
TABLES 1-12

TABLE 6. Four scenarios of deposition on the Monument Creek debris fan used to calculate volumes 

of sediment deposited during the debris flow of1984

33

SCENARIOS

1. Assume that debris flow did not reach the Colorado River and that 

the debris fan present in 1986 is the maximum deposition 

(unrealistically low).

2. Assume that the debris flow covered the fan and half of the Colorado 

River bed to a depth of 3 feet.

3. Assume that the debris flow covered the entire bed of the Colorado 

River to a depth of 3 feet (most realistic).

4. Assume that the debris flow totally dammed the river to a depth of 

11 feet (unrealistically high).

FAN VOLUMES

Scenario

1

2

3

4

Fan

volume,

in

cubic

feetl

160,000

160,000

160,000

160,000

River

area,

in

square

feet

0

26,000

49,000

49,000

River

depth,

in

feet

0

3

3

11

River

volume

in

cubic

feet

0

80,000

150,000

270,000

Total

volume

in

cubic

feet

160,000

240,000

310,000

430,000

Sand

volume

in

cubic

feet2

56,000

84,000

110 , 000

150,000

Duration

of peak

<Tp ), in

seconds3

60

90

120

160

Average fan depth is an estimated 5 feet over a 32,000 feet2 area. 

2 The debris flow was approximately 35 percent sand.

3 A total discharge of 3,800 ft3 /s and a sediment discharge of 2,700 

ft3 /s was used to estimate the duration of peak discharge.
34 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

TABLE 7. Indirect-discharge calculation for the debris flow of 1966 on Dragon Creek at site E, 5.0 

miles upstream from the Colorado River

RUNUP DATA

Runup elevation (Ah ) - 3.93 feet Channel slope (S) - 0.01

V - 15.9 feet per second (F - 0.7)

CROSS SECTION DATA

Runup site

Area , in 

square 

feet

710

Q - 11,300 cubic

Hydraulic 

radius , 

in feet

9.5

feet per second

Hydraulic 

depth , 

in feet

12.0

TABLE S. Indirect-discharge calculation for the debris flow of 1966 on Dragon Creek at site F, 4-8 

miles upstream from the Colorado River

SUPERELEVATION DATA

Radius of curvature (J? ) - 75 feet Channel width (tf) - 175 feet 

Elevation difference (Ah ) - 22.67 feet Channel slope (S) - 0.06

V - 17.7 feet per second (F - 1.3 to 2.7)

CROSS SECTION DATA

Section

Upstream #1 

Upstream #2 

Superelevation 

Downstream 

Average

Thalweg 

distance

from superelevation, 

in feet

210

90

0

80

Area , in 

square 

feet

870

670

2,480

840

790

Hydraulic 

radius , 

in feet

7.0

3.9

12.5

5.9

Hydraulic 

depth , 

in feet

7.4

3.6

14.2

6.9

Q - 14,000 (11,900 to 15,400) cubic feet per second
TABLES 1-12

TABLE 9. Indirect-discharge calculations for the debris flow of 1966 on Crystal Creek at site G, 0.9 

mile upstream from the Colorado River

35

SUPERELEVATION DATA

Radius of curvature (R ) - 132 feet Channel width (tf) - 186 feet 

Channel slope (S) - 0.04 

V - 10.3 feet per second (F - 0.3 to 0.6)

Elevation difference (Ah ) - 4.65 feet

S

RUNUP DATA 

Elevation #1 (Ahp - 3.51 feet V - 15.0 feet per second (F - 0.6 to 1.2)

Elevation #2 (Ah ) - 3.68 feet V - 15.4 feet per second (F - 0.6 to 1.2)

CROSS SECTION DATA

Section

Upstream 

Downstream #1

Downstream #2

Average

Thalweg 

distance

from superelevation, 

in feet

135 

185

255

Q - 9,200 to 13,500

Area, in 

square 

feet

940 

1,240

890

920

cubic feet

Hydraulic 

radius , 

in feet

5.6 

10.2

9.7

per second

Hydraulic 

depth, 

in feet

5.9 

11.5

11.9

TABLE 10. Comparison of discharges calculated at all superelevation sites by the cross-sectional area 

at the highest superelevation marks and an average of the upstream and (or) downstream cross-sectional

areas

Location

Lava-Chuar Creek

at site F

Monument Creek

at Tapeats 

Alcove

Monument Creek

site B 

Monument Creek

site C

Dragon Creek 

site F

Crystal Creek 

site G

Mean 

velocity, 

in feet

per 

second

12.0

12.0

11.0

11.9-13.2

17.7

10.3

Area at 

or near 

superelevation,

in square 

feet

1,180

580

420

2,480

1,240

Discharge , 

in cubic 

feet

per 

second

14,200

7,000

4,600

43,900

12,800

Average of 

upstream 

and downstream

area, in 

square feet

330

320

320

320

790

920

Discharge , 

in cubic 

feet

per 

second

4,000

3,800

3,500

3,800-4,200

14,000

9,500
36 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

TABLE 11. Historic flow events or channel changes in tributaries of the Colorado River in Grand Canyon

National Park

[Determination of changes is somewhat subjective. A confidence rating of 1 indicates a change or event occurred; a rating of 2 indicates that though a change or event probably occurred, the evidence is not strong; a rating of 3 indicates little confidence in the 

reported change. An (*) asterisk indicates a major change or event.]

River 

mile side Tributary name

Nature of 

event or change Year

Confidence 

rating

7.

7.

11.

11.

11.

11.

16.

17.

26.

31.

35.

37.

37.

41.

41.

43.

43.

43.

44.

44.

44.

52.

52.

52.

65.

65.

65.

65.

66.

66.

66.

67.

67.

68.

69.

70.

70.

70.

70.

70.

70.

70.

71.

71.

71.

71.

72.

72.

72.

73.

73.

73.

73.

74.

74.

76.

87.

87.

87.

89.

91.

92.

92.

0

8

2

2

8

8

8

5

8

5

6

4

4

0

4

1

7

7

1

5

8

0

0

0

5

5

5

5

3

3

9

2

9

1

6

0

2

3

4

5

8

9

0

2

3

8

0

5

5

3

5

7

8

4

9

8

8

8

8

0

5

2

8

L

R

R

R

L

L

R

L

R

R

L

L

L

R

R

L

R

L

L

L

L

R

R

R

R

R

L

L

R

L

L

L

L

L

R

R

R

R

L

L

L

R

L

R

R

R

R

R

R

L

L

R

R

R

L

L

R

R

R

L

R

L

L

Unnamed chute 

Badger Creek 

Soap Creek 

Soap Creek 

Salt Water Wash 

Salt Water Wash 

Rider Canyon 

'Redneck Rapid' 

'MNA Rapid' 

South Canyon 

Unnamed channel 

Tatahatso Wash 

Tatahatso Wash 

Buck Farm Wash 

Bert's Canyon 

43 mile camp canyon 

President Harding 

President Harding 

Fan below Harding 

Fan below Harding 

Fan below Harding 

Nankoweap Creek 

Nankoweap Creek 

Nankoweap Creek 

Lava Creek 

Lava Creek 

Palisades Creek 

Palisades Creek 

Chute below Lava Cr 

Chute below Palisade 

Espejo Creek 

Comanche Creek 

Unnamed drainage 

Unnamed drainage 

Basalt Creek 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Cardenas Creek 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Unnamed drainage 

Unkar Creek 

Unkar Creek 

6-8 small gullies 

Unnamed drainage 

Unnamed chute 

Unnamed chute 

Unnamed chute 

Escalante Creek 

Red Canyon 

Bright Angel Creek 

Bright Angel Creek 

Bright Angel Creek 

Pipe Creek 

Trinity Creek 

Unnamed chute 

Salt Creek

Landslide 1970 1

Channel changes 1973-84 1

Channel changes 1935-65 2

Channel changes 1973-84 1

Channel changes 1935-65 2

Channel changes 1973-84 2

Channel changes 1935-73 2

Rockfall 1978-79 1

Rockfall 1975 1

Channel changes 1965-73 2

Fan changes 1973-84 1

Rockfall 1977 1

Channel changes 1973-84 2

Debris flow 1981-83 1

Channel changes 1973-84 2

Debris flow 1983 1

*Rapid formed 1911-23 1

Fan changes 1973-84 1

Fan changes 1983 1

Fan changes 1983 1

Fan changes 1983 1

Channel shifted 1935-65 1

Channel shifted 1966 1

Channel shifted 1973-84 1

Debris flow 1966 1

Debris flow 1973-84 1

*Debris flow 1965-73 1

Channel changes 1973-84 2

Fan changes 1965-84 1

Channel changes 1965-73 2

Fan changes 1973-84 1

Fan changes 1973-84 1

Fan changes 1965-84 1

Fan changes 1965-73 2

*Flood 1983 1

Fan changes 1973-85 1

Fan changes 1965-84 1

Fan changes 1965-84 1

Fan changes 1973-84 1

Fan changes 1973-84 1

Fan changes 1973-84 1

Fan changes 1973-84 2

Channel changes 1984 1

Fan changes 1965-84 1

Debris flow 1983 1

Fan changes 1973-84 1

Rockfall, flood 1983 1

Channel changes 1966 1

Channel changes 1973-84 1

Channel changes 1973-84 1

Fan changes 1965-84 2

Fan changes 1973-84 1

Fan changes 1973-84 1

Fan changes 1965-84 2

Fan changes 1973-84 1

Channel changes 1973-84 2

Large flood 1936 1

*Channel changes 1966 1

Channel changes 1973-84 1

Channel changes 1973-84 2

Flood or debris flow 1985 1

Channel changes 1973-84 2

Channel changes 1973-84 2
TABLES 1-12 37

TABLE 11. Historic flow events or channel changes in tributaries of the Colorado River in Grand Canyon

National Park Continued

River 

mile side

93.5

96.7

96.9

98.2

98.2

100.6

102.0

108.6

115.5

116.5

119.0

121.7

122.7

122.2

128.4

129.0

132.0

132.0

133.8

133.8

133.8

136.2

137.2

143.5

143.5

143.5

156.8

166.5

168.0

174.2

176.4

178.1

181.3

202.2

202.3

203.8

204.1

205.2

207.9

209.0

211.5

220.0

225.8

L

L

L

R

R

L

L

R

L

L

R

L

L

L

R

L

R

L

R

R

R

R

R

R

R

R

L

L

R

R

R

R

R

R

R

R

L

L

L

R

R

R

L

Tributary name

Monument Creek

Boucher Creek

Chute below Boucher

Crystal Creek

Crystal Creek

Agate Creek

Turquoise Creek

Shinumo Creek

Unnamed canyon

Elves Chasm

119 -Mile Creek

Unnamed chute

Forster Creek

Unnamed chute

128-Mile Creek

Spector Chasm

Stone Creek

Unnamed chute

Tapeats Creek

Tapeats Creek

Tapeats Creek

Deer Creek

Unnamed chute

Kanab Creek

Kanab Creek

Kanab Creek

Havasu Creek

National Canyon

Fern Glen Canyon

Cove Canyon

Saddle Horse Canyon

Unnamed chute

Unnamed chute

Unnamed canyon

Unnamed canyon

Unnamed canyon

Unnamed canyon

205 -Mile Creek

Unnamed canyon

Unnamed chute

Fall Canyon

220-Mile Creek

Diamond Creek

Nature of 

event or change

*Debris flow

Channel changes

Channel changes

*Debris flow

Channel changes

Channel changes

Channel changes

Channel changes

Channel changes

*Debris flow

Channel changes

Channel changes

*Channel changes

Channel changes

Channel changes

Channel changes

Channel changes

*New fan

*Debris flow

Flood

Flood

Debris flow

Debris flow

*Large flood

*Large flood

Channel changes

*Large flood

Channel changes

Channel changes

Channel changes

Channel changes

Debris flow

Debris flow

Debris flow

Debris flow

Debris flow

Channel changes

*Channel changes

Channel changes

Rockfall

Channel changes

Channel changes

*Debris flow

Confidence 

Year rating

1984

1973-84

1973-84

1966

1973-84

1973-84

1973-84

1973-84

1985

1985

1973-84

1973-84

1973-84

1973-84

1973-84

1973-84

1973-84

1872-1968

1961

1975

1984

1985

1973-84

1883

1909

1973-84

1911

1984

1973-84

1973-84

1973-84

1973-84

1973

1973-84

1973-84

1973-84

1973-84

1983

1973-84

1978-79

1973-84

1984

1984

1

2

3

1

1

1

2

2

1

1

1

1

1

1

1

2

2

1

1

1

1

1

1

1

1

1

1

1

2

1

1

1

1

2

1

3

2

1

3

1

1

1

1
38 DEBRIS FLOWS FROM TRIBUTARIES OF THE COLORADO RIVER, ARIZONA

TABLE 12. Relation between difficulty rating for rapids and drainage area of the contributing 

tributaries for 67 rapids on the Colorado River

[Rapid rating is a subjective scale from 1 (least severe) to 10 (most severe) based on navigational difficulty for oar-powered boats (Stevens,

1983)]

Rapid name

Paria Riffle

Badger

Soap Creek

House Rock

North Canyon

21 Mile

Indian Dick

24.5 Mile

25 Mile

Cave Springs

Tiger Wash

29 Mile

Saddle Canyon

Nankoweap

Kwagunt

Little Colorado

Lava Creek

Basalt

Unkar

Nevills

Nance

Sockdolager

Grapevine

83 Mile

Clear Creek

Zoroaster

85 Mile

Bright Angel

Pipe Springs

Horn Creek

Salt Creek

Granite

94 Mile Creek

Hermit

Boucher

Crystal

Tuna Creek

Sapphire

Turquoise

104 Mile

Ruby

Serpentine

Bass

Shinumo Creek

Waltenberg

112.5 Mile

Rancid Tuna

Blacktail

122 Mile

Forster

Fossil

128 Mile

Specter

Bedrock

Deubendorf

Tapeats

134 Mile

135 Mile

Doris

Fishtail

Kanab Creek

River 

mile

0.9

7.9

11.2

16.9

20.5

21.1

23.2

24.5

24.8

25.2

26.7

29.2

47.0

52.2

56.0

61.5

65.5

69.2

72.6

75.5

76.8

78.7

81.6

83.5

84.1

84.5

85.0

87.9

88.9

90.1

92.6

93.5

94.3

95.0

96.8

98.2

99.2

101.3

102.0

103.9

104.8

105.9

107.5

108.5

112.2

112.5

113.0

120.1

121.8

122.8

125.0

128.4

129.0

130.5

131.8

133.8

134.3

134.9

137.7

139.0

143.5

Contributing 

area of 

drainages , 

in square 

miles

1,410.0

46.6

35.3

308.6

154.1

0.3

0.1

9.9

0.4

0.7

19.8

60.8

11.3

32.6

15.2

26,955.0

22.9

5.3

14.5

4.6

4.1

9.0

14.6

1.7

35.7

1.5

0.1

101.0

6.6

1.6

1.2

3.3

3.7

12.6

6.4

47.9

23.3

3.7

5.7

1.7

6.6

1.5

5.5

85.5

6.3

0.9

0.5

9.3

3.1

3.9

13.2

3.0

3.1

8.2

7.3

82.9

2.2

1.8

0.3

7.7

2,290.0

10,000 

cubic feet 

per second 

rating

1

6

5

7

5

5

5

5

5

5

4

2

1

3

6

1

4

3

6

6

9

9

8

4

1

6

3

4

4

8

4

9

1

9

4

10

6

7

4

6

6

7

4

4

7

2

6

3

5

6

6

5

6

8

8

6

3

5

6

6

3

1921 

Water -surf ace 

fall, in feet

2

12

17

9

12

5

6

9

7

6

7

6

1

25

19

8

8

2

21

15

26

19

17

7

2

7

6

8

14

9

3

17

2

15

13

17

10

7

2

3

8

10

4

8

14

4

4

7

4

7

15

8

5

7

15

7

7

2

2

10

18
TABLES 1-12 39

TABLE 12. Relation between difficulty rating for rapids and drainage area of the contributing 

tributaries for 67 rapids on the Colorado River Continued

Rapid name

Upset

Lava Falls

205 Mile

209 Mile

L'il Bastard

217 Mile

River

mile

149.8

179.3

205.5

208.8

212.1

217.3

Contributing

area of

drainages ,

in square

miles

30.9

96.9

10.6

88.3

0.2

9.2

10,000

cubic feet

per second

rating

8

10

7

7

3

7

1921

Water -surf ace

fall, in feet

15

10

9

12

5

13
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over the counter in paperback booklet form only. Those wishing a free 

subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 

National Center, Reston, VA 22092.

Note.-Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the 

prices charged may differ from the prices in catalogs, announcements, 

and publications.