U.S. Department of the Interior 

U.S. Geological Survey

Verification of Roughness Coefficients 

for Selected Natural and Constructed 

Stream Channels in Arizona

U.S. Geological Survey Professional Paper 1584

Prepared in cooperation with the

Flood Control District of Maricopa County

m
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Verification of Roughness Coefficients 

for Selected Natural and Constructed 

Stream Channels in Arizona

By JEFF V. PHILLIPS anc/TODD L. INGERSOLL

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1584

Prepared in cooperation with the

FLOOD CONTROL DISTRICT OF MARICOPA 

COUNTY

1998
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

thomas J. Casadevall, Acting Director

The use of firm, trade, and brand names in this report is for 

identification purposes only and does not constitute 

endorsement by the U.S. Government.

Library of Congress Cataloging in Publications Date

Phillips, Jeff V., 1962-

Verification of roughness coefficients for selected natural and 

constructed stream channels in Arizona / by Jeff V. Phillips and 

Todd L. Ingersoll.

p. cm.--(U.S. Geological Survey professional paper ; 1584)

"Prepared in cooperation with the Flood Control District of 

Maricopa County."

ISBN 0-607-88875-X (alk. paper)

1. Channels (Hydraulic engineering)~Arizona. 2. Frictional 

resistance (Hydrodynamics) I. Ingersoll, Todd L., 1970- . 

II. Flood Control District of Maricopa County. III. Title. 

IV. Series. 

TC175.P45 1998

627'.23'097921»dc21 97-48313

CIP

For sale by U.S. Geological Survey, Information Services

Box 25286, Federal Center

Denver, CO 80225
CONTENTS

Abstract..................................................................._ 1

Introduction .................................................................................................................................................^ 1

Purpose and scope ...................................................................................................................................................... 2

Acknowledgments...................................................................................................................................................... 2

Description of study area...................................................................................................................................................... 2

Field measurements for verified roughness coefficients....................................................................................................... 4

Site selection.......................................................................................................................................................^ 4

Data collection.....................................................................................................................................................^ 4

Computation of reach properties and roughness coefficients............................................................................................... 5

Assumptions and limitations ................................................................................................................................................ 7

Changing boundary conditions................................................................................................................................... 7

Changing vegetation conditions ................................................................................................................................. 7

Uncertainties of discharge measurements .................................................................................................................. 8

Flow depth and magnitude ......................................................................................................................................... 8

Changing bed forms.................................................................................................................................................... 9

Presentation of verified roughness coefficients .................................................................................................................... 10

Hassayampa River near Arlington.............................................................................................................................. 11

Skunk Creek above Interstate 17................................................................................................................................ 16

Agua Fria River below New Waddell Dam................................................................................................................ 23

Cave Creek above Deer Valley Road.......................................................................................................................... 27

Cave Creek below Cave Buttes Dam ......................................................................................................................... 31

Hassayampa River near Morristown .......................................................................................................................... 35

Indian Bend Wash above Curry Road......................................................................................................................... 40

Salt River above Interstate 10..................................................................................................................................... 44

Verde River below Beeline Highway ......................................................................................................................... 48

West Fork Sycamore Creek near Sunflower............................................................................................................... 52

SanPedro River near Charleston................................................................................................................................ 55

Santa Cruz River at Cortaro........................................................................................................................................ 59

Verde River near Paulden........................................................................................................................................... 63

Salt River below Stewart Mountain Dam................................................................................................................... 66

Discussion of significant results ............................................................................................................................................ 69

Components of Manning's n....................................................................................................................................... 69

Base value of Manning's n for gravel-bed streams .................................................................................................... 69

Influence of vegetation on Manning's n ..................................................................................................................... 74

Summary and conclusion...................................................................................................................................................... 74

Selected references............................................................................................................................................................... 75

FIGURES

1. Map showing study area and n-verification sites in Maricopa, Pima, Cochise,

and Yavapai Counties, Arizona.............................................................................................................................. 3

2. Drawing showing open-channel flow reach in plan and profile views.................................................................. 6

3. Graph showing relation of stream power and median grain size to form of bed roughness................................. 9

4A-H. Hassayampa River near Arlington:

A. Graph showing cross-section 3.................................................................................................................... 12

B. Drawing showing plan view........................................................................................................................ 12

C. Graph showing Manning's n and hydraulic radius...................................................................................... 13

D. Graph showing particle-size distribution for bed material.......................................................................... 13

Contents III
E. Photograph showing view of typical bed material for low-flow channel..................................................... 14

F. Photograph showing view from right bank showing a current-meter measurement

made in the low-flow channel....................................................................................................................... 14

G. Photograph showing view looking upstream from midreach of low-flow channel...................................... 15

H. Photograph showing view from right bank and midreach looking downstream following

flow of February 9, 1993............................................................................................................................... 15

5A-K. Skunk Creek above Interstate 17:

A. Graph showing cross-section 2 ..................................................................................................................... 17

B. Drawing showing plan view.......................................................................................................................... 18

C. Graph showing Manning's n and hydraulic radius........................................................................................ 18

D. Graph showing particle-size distribution for bed material............................................................................ 19

E. Photograph showing view of typical bed material in channel reach............................................................. 19

F. Photograph showing view from left bank and bottom of reach looking upstream during flow

of March 1, 1991........................................................................................................................................... 20

G. Photograph showing view from midchannel looking upstream following flow of March 1,1991.............. 20

H. Photograph showing view from midchannel and bottom of reach looking upstream following

artificial maintenance of the channel vegetation, May 23, 1994................................................................... 21

I. Photograph showing view from midchannel of reach looking upstream during

flow of Januarys, 1995................................................................................................................................. 21

J. Photograph showing view from midchannel looking upstream at regrowth of vegetation .......................... 22

K. Photograph showing view from midchannel looking upstream following flow of August 14, 1996 ........... 22

6A-G. Agua Fria River below New Waddell Dam:

A. Graph showing cross-section 2 ..................................................................................................................... 23

B. Drawing showing plan view.......................................................................................................................... 24

C. Graph showing particle-size distribution for bed material............................................................................ 24

D. Photograph showing view of typical bed material in channel reach............................................................. 25

E. Photograph showing view from bottom of the reach looking upstream

on March 10, 1993 ........................................................................................................................................ 25

F. Photograph showing view from midchannel looking toward left bank of cross-section 4........................... 26

G. Photograph showing view from midchannel in cross-section 2 of typical vegetation in the reach ............. 26

7A-G. Cave Creek above Deer Valley Road:

A. Graph showing cross-section 2 ..................................................................................................................... 28

B. Drawing showing plan view.......................................................................................................................... 28

C. Graph showing Manning's n and hydraulic radius........................................................................................ 28

D. Graph showing particle-size distribution for bed material............................................................................ 29

E. Photograph showing view of typical bed material in channel reach............................................................. 29

F. Photograph showing view from bottom of reach looking upstream during flow of January 9, 1995........... 30

G. Photograph showing view from top of reach looking downstream ............................................................. 30

8A-G. Cave Creek below Cave Buttes Dam:

A. Graph showing cross-section 4 ..................................................................................................................... 32

B. Drawing showing plan view.......................................................................................................................... 32

C. Graph showing Manning's n and hydraulic radius........................................................................................ 32

D. Photograph showing view from cross-section 7 looking upstream toward transition from subcritical

to supercritical flow....................................................................................................................................... 33

E. Photograph showing view from cross-section 4 looking upstream toward subcritical flow reach

during survey of the water surface, November 2, 1995 ................................................................................ 33

F. Photograph showing view from top of reach looking downstream .............................................................. 34

G. Photograph showing view from midchannel looking downstream............................................................... 34

9A-G. Hassayampa River near Morristown:

A. Plot showing cableway cross section, bed geometry for each current-meter measurement,

and water-surf ace elevations ......................................................................................................................... 36

B. Drawing showing plan view.......................................................................................................................... 37

C. Graph showing Manning's n and hydraulic radius........................................................................................ 37

D. Graph showing particle-size distribution for bed material............................................................................ 38

E. Photograph showing view upstream from midchannel during no-flow period............................................. 38

IV Contents
F. Photograph showing view from cableway looking upstream during flow

of February 9, 1993 ....................................................................................................................................... 39

G. Photograph showing view from cableway looking upstream during flow of

February 9, 1993 ........................................................................................................................................... 39

10A-G. Indian Bend Wash above Curry Road:

A. Graph showing cross-section 3 ..................................................................................................................... 41

B. Drawing showing plan view.......................................................................................................................... 41

C. Graph showing Manning's n and hydraulic radius........................................................................................ 41

D. Photograph showing view from midchannel looking downstream at laid-over grass

following flow of October 6, 1993................................................................................................................ 42

E. Photograph showing view from midreach looking upstream following flow of October 6, 1993................ 42

F. Photograph showing view from bottom of reach looking upstream during low flow................................... 43

G. Photograph showing view from midchannel looking upstream before flow of December 26, 1994............ 43

11A-G. Salt River above Interstate 10:

A. Graph showing cross-section 1 ..................................................................................................................... 44

B. Drawing showing plan view.......................................................................................................................... 45

C. Graph showing Manning's n and hydraulic radius........................................................................................ 45

D. Graph showing particle-size distribution for bed material............................................................................ 46

E. Photograph showing view of typical bed material in channel reach............................................................. 46

F. Photograph showing view from top of reach looking downstream during flow of January 15, 1992.......... 47

G. Photograph showing view from top of reach looking downstream .............................................................. 47

12A-G. Verde River below Beeline Highway:

A. Graph showing cross-section 2 ..................................................................................................................... 48

B. Drawing showing plan view for flow of March 28, 1991............................................................................. 49

C. Graph showing Manning's n and hydraulic radius........................................................................................ 49

D. Graph showing particle-size distribution for bed material............................................................................ 50

E. Photograph showing view of typical bed material........................................................................................ 50

F. Photograph showing view from right bank and midreach looking upstream

during flow of September 14, 1989............................................................................................................... 51

G. Photograph showing view from cableway looking downstream during flow of March 28, 1991................ 51

13A-E. West Fork Sycamore Creek near Sunflower:

A. Graph showing cross-section 2 ..................................................................................................................... 52

B. Drawing showing plan view.......................................................................................................................... 53

C. Photograph showing view from bottom of reach looking upstream

toward cross-section 2, February 25, 1963 ................................................................................................... 53

D. Photograph showing view from midreach looking upstream

toward right bank of cross-section 1, February 25, 1963.............................................................................. 54

E. Photograph showing view from bottom of reach looking upstream

toward cross-section 3. February 25, 1963 ................................................................................................... 54

14A-E. San Pedro River near Charleston:

A. Graph showing cross-section 2, ................................................................................................................... 56

B. Drawing showing plan view.......................................................................................................................... 56

C. Graph showing particle-size distribution for bed material............................................................................ 57

D. Photograph showing view from left bank looking downstream toward right

bank of cross-section 1, October 8, 1964...................................................................................................... 57

E. Photograph showing view from left bank of cross-section 2 looking downstream, October 8, 1964 .......... 58

15A-F. Santa Cruz River at Cortaro:

A. Graph showing cross-section 2 ..................................................................................................................... 60

B. Drawing showing plan view.......................................................................................................................... 60

C. Graph showing particle-size distribution for bed material............................................................................ 61

D. Photograph showing view from cableway looking downstream, August 5, 1954,

at a discharge of 7,000 cubic feet per second................................................................................................ 61

E. Photograph showing view from cableway looking downstream, October 2, 1964....................................... 62

Contents V
F. Photograph showing view from midchannel looking upstream toward right

bank of cross-section 1 after flow of September 10, 1964............................................................................ 62

16A-D. Verde River near Paulden:

A. Graph showing cross-section 2 ..................................................................................................................... 64

B. Drawing showing plan view.......................................................................................................................... 64

C. Photograph showing view from top of reach looking downstream during low flow.................................... 65

D. Photograph showing view from top of reach looking downstream at time of

verification measurement, April 16, 1965 ..................................................................................................... 65

17A-D. Salt River below Stewart Mountain Dam:

A. Graph showing cross-section 2 ..................................................................................................................... 67

B. Drawing showing plan view.......................................................................................................................... 67

C. Photograph showing view looking upstream along left bank below cross-section 6.................................... 68

D. Photograph showing view looking downstream along left bank from cross-section 2................................. 68

18. Graph showing relation of Manning's n and relative roughness for gravel-bed stream

channels in Arizona and throughout the world...................................................................................................... 72

19. Graph showing relation of vegetation components for vegetated channels

studied and the estimated percentage of vegetation that blocks flow.................................................................... 75

TABLES

1. Flow data and computed roughness coefficients, HassayampaRiver near Arlington............................................. 11

2. Average-reach properties, Hassayampa River near Arlington................................................................................. 11

3. Flow data and computed roughness coefficients. Skunk Creek above Interstate 17............................................... 16

4. Average-reach properties. Skunk Creek above Interstate 17................................................................................... 17

5. Flow data and computed roughness coefficient, Agua Fria River below New Waddell Dam................................. 23

6. Average-reach properties, Agua Fria River below New Waddell Dam................................................................... 23

7. Flow data and computed roughness coefficients. Cave Creek above Deer Valley Road......................................... 27

8. Average-reach properties, Cave Creek above Deer Valley Road ............................................................................ 27

9. Flow data and computed roughness coefficients, Cave Creek below Cave Buttes Dam......................................... 31

10. Average-reach properties, Cave Creek below Cave Buttes Dam ............................................................................ 31

11. Flow data and computed roughness coefficients, Hassayampa River near Morristown ......................................... 35

12. Data obtained from discharge measurements and field surveys, Hassayampa River near Morristown.................. 36

13. Flow data and computed roughness coefficient, Indian Bend Wash above Curry Road......................................... 40

14. Average-reach properties, Indian Bend Wash above Curry Road ........................................................................... 40

15. Flow data and computed roughness coefficients, Salt River above Interstate 10.................................................... 44

16. Average-reach properties, Salt River above Interstate 10........................................................................................ 44

17. Flow data and computed roughness coefficients, Verde River below Beeline Highway ........................................ 48

18. Average-reach properties, Verde River below Beeline Highway ............................................................................ 48

19. Flow data and computed roughness coefficient. West Fork Sycamore Creek near Sunflower................................ 52

20. Average-reach properties, West Fork Sycamore Creek near Sunflower.................................................................. 52

21. Flow data and computed roughness coefficient, San Pedro River near Charleston ................................................ 55

22. Average-reach properties, San Pedro River near Charleston................................................................................... 55

23. Flow data and computed roughness coefficient, Santa Cruz River at Cortaro ........................................................ 59

24. Average-reach properties, Santa Cruz River at Cortaro .......................................................................................... 59

25. Flow data and computed roughness coefficient, Verde River near Paulden............................................................ 63

26. Average-reach properties, Verde River near Paulden.............................................................................................. 63

27. Flow data and computed roughness coefficient. Salt River below Stewart Mountain Dam ................................... 66

28. Average-reach properties, Salt River below Stewart Mountain Dam...................................................................... 66

29. Summary of verification measurements that include magnitude of base n values, 

	factors required to adequately describe flow retardance, channel and hydraulic 

	components, and an estimated percentage of flow that was blocked by vegetation................................................ 70

30. Equations for relations among base n values, hydraulic radius, and median

	diameter of bed material for gravel-bed streams in different parts of the world..................................................... 72

VI Contents
CONVERSION FACTORS

Multiply

inch (in.)

foot (ft) 

cubic foot per second (ft3/s) 

mile (mi) 

square mile (mi2 )

By

25.4

0.3048 

0.02832 

1.609 

2.590

To obtain

millimeter

meter 

cubic meter per second 

kilometer 

square kilometer

VERTICAL DATUM

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 the 

United States and Canada, formerly called Sea Level Datum of 1929.

GLOSSARY OF TERMS

Antidune: Bed forms of curved symmetrically shaped sand waves that may move 

upstream, remain stationary, or move downstream. Antidunes occur in trains that are 

in phase with and strongly interact with gravity water-surface waves. The watersurface waves have larger amplitudes than the coupled sand waves. At large Froude 

numbers, the waves generally move upstream and grow until they become unstable 

and break like surf (breaking antidunes). The agitation accompanying the breaking 

obliterates the antidunes, and the process of antidune initiation and growth is 

repeated. At smaller Froude numbers, the antidunes generally remain stationary and 

increase and decrease in amplitude without breaking (standing waves; Simons and 

Richardson, 1966, p. v).

Backwater: Water backed up or retarded in its course as compared with its normal or 

natural condition of flow. In stream gaging, a rise in stage produced by a temporary 

obstruction such as ice or weeds, or by the flooding of the stream below.

Bank, left and right: Reference terms used to specify the banks on the left and right when 

facing downstream.

Bedform: Alluvial-channel bottom feature whose form depends on bed-material size, 

flow depth, and flow velocity. Bedforms include ripples, dunes, antidunes, and plane 

bed.

Conveyance: A measure of the carrying capacity of a channel section and is directly 

proportional to channel discharge. Conveyance is that part of Manning's equation 

that excludes the square root of the energy gradient or friction slope.

Crest-stage gage: A device for recording the peak water-surface elevation during a flood 

by means of a cork line that adheres to a wooden rod placed in a 2-inch-diameter 

metal pipe that has been secured near the channel margins.

Critical flow: If the flow is critical, the Froude number is equal to unity, and the inertial 

forces balance the gravitational forces. This balance takes place at the depth at which 

flow is at its minimum energy.

Dryland: Streams located in regions of semiarid to extremely arid climatic conditions. 

For the conterminous United States, this would apply to regions that accrue less than 

20 in. of precipitation annually.

Ephemeral: A stream or reach of a stream that flows briefly in direct response to 

precipitation or snowmelt in the immediate vicinity, and whose channel is at all times 

above the water table.

Flood peak: The largest value of the runoff flow which occurs during a flood, as observed 

at a particular point in the drainage basin.

Contents VII
Flood plain: A flood-prone area, as identified on Federal Emergency Management 

Agency (FEMA) flood insurance rate maps, generally contains a floodway district 

and floodway fringe district, or contains areas of land adjoining (or near) the channel 

of a water course which has been, or may be, covered by floodwaters. A flood plain 

functions as a temporary channel or reservoir for overbank flows. The lowland that 

borders a river, usually dry but subject to flooding (Hoyt and Langbein, 1955, p. 12).

Flow regime: A range of flows producing similar bed forms, resistance to flow, and mode 

of sediment transport. The lower flow regime occurs with tranquil flow and produces 

bed forms of ripples, ripples on dunes, or dunes. The upper flow regime produces bed 

forms of plane bed with sediment moving, standing waves, or antidunes. Watersurface undulations are generally in phase with bed undulations. Between these two 

stable regimes is the transition regime, which produces instability in the stage-todischarge relation and in the typical bed forms.

Froude number: A dimensionless number used as an index to characterize the type of 

flow (subcritical, critical, and supercritical) in an open channel. The Froude number 

is the ratio of the inertial forces to the gravitational forces, and is computed as the 

mean flow velocity divided by the square root of the product of the mean depth times 

the acceleration of gravity.

Grain size, coarse and fine: Coarse-grained bed material generally refers to those 

particles (gravel, cobble, boulder) whose size can be individually measured with a 

graduated rule or caliper; fine-grained material (sand, silt, clay) is measured by 

passage through a sieve or by rate of sedimentation. See also particle size.

High-water marks: Evidence of the highest stage reached by flow. High-water marks 

generally consist of debris and scour marks found along the channel boundaries.

Hydraulic radius: The ratio of the stream channel's cross-sectional area to its wetted 

perimeter in a plane normal to the direction of flow.

Hydrograph: The functional relation between time and flow discharge, as observed at a 

particular point within a drainage basin. In the case of a detention and (or) retention 

facility, an inflow hydrograph depicts the relation of time and runoff inflow to the 

facility, and an outflow hydrograph is a graph of flow discharge from the facility 

compared to time.

Intermittent stream: A stream that flows only at certain times of the year when it 

receives water from some surface source (rainfall or snowmelt) or from an 

intermittent spring and ceases to flow during other periods of the year. The channel is 

usually above the water table.

Manning's roughness coefficient (n value): A measure of the frictional resistance 

exerted by a channel on the flow. The n value also can reflect other energy losses such 

as those resulting from unsteady flow, extreme turbulence, and transport of 

suspended material and debris, that are difficult or impossible to isolate and quantify.

Particle-size: The size of material on the bed of a stream, referenced to a specific diameter 

(either maximum, intermediate, or minimum) of the measured particles.

Perennial stream: A stream that discharges continuously all year during dry as well as 

wet years.

Relative roughness: Relative roughness is the ratio of mean depth (usually represented by 

hydraulic radius, R) to the size of roughness elements (usually represented by the 

median value of the intermediate diameter of the streambed material, ^50)-

Runoff: The portion of precipitation on land that ultimately reaches streams—especially 

water from rain or melted snow that flows over the land surface.

Scour: Erosion due to flowing water, usually considered as being localized as opposed to 

general bed degradation.

Slope, water-surface: The slope of the water surface, computed as the change in 

elevation per unit change in the channel's length.

VIM Contents
Slope-area method of discharge measurement: A computational procedure whereby

stream discharge is calculated "on the basis of a uniform-flow equation involving

channel characteristics, water-surface profiles, and a roughness coefficient"

(Dalrymple and Benson, 1967). 

Stream power: A measure of energy transfer of the flow. Stream power is computed as

62RSV, where R, S, and V are the hydraulic radius, in feet; water-surface slope, in feet

per foot; and mean velocity, in feet per second, respectively; and 62 is the specific

weight of water. Stream power also is defined as the energy dissipated per unit area of

streambed per unit time. 

Subcritical flow: If the flow is subcritical, the Froude number is less than one and the

inertial forces are less than the gravitational forces. The flow depth in subcritical flow

is greater than the flow depth in critical flow. 

Supercritical flow: If the flow is supercritical, the Froude number is greater than one and

the inertial forces are greater than the gravitational forces. The flow depth in

supercritical flow is less than the flow depth in critical flow. 

Uniform flow: Flow of constant water area, depth, discharge, and average velocity

through a reach of a channel. 

Velocity head: Represents the kinetic energy of the flowing fluid, generally expressed as

V2/2g, in feet, but actually is the energy per pound of flowing fluid. 

Velocity-head coefficient: A factor used to adjust the velocity of the head computed from

the mean velocity in a channel section to give the true mean kinetic energy of the

flow for nonuniform distribution of velocities. 

Wash load: The material which is transported by the river but is not found in significant

quantities in the bed material. 

Water-surface profile: A longitudinal plot of the water-surface elevation as a function of

the distance downstream through a channel reach. 

Wetted perimeter: The length of the line of intersection of the channel's wetted surface

with a cross-sectional plane normal to the direction of flow.

Contents IX
Verification of Roughness Coefficients for 

Selected Natural and Constructed Stream 

Channels in Arizona

By Jeff V. Phillips and Todd L Ingersoll

ABSTRACT

Physical and hydraulic characteristics are 

presented for 14 river and canal reaches in Arizona 

for which 37 roughness coefficients have been 

determined. The verified roughness coefficients, 

which ranged from 0.017 to 0.067, were computed 

from discharges, channel geometry, and watersurface profiles measured at each of the sites. The 

reaches studied cover a wide range of channel 

conditions including alluvial channels, boulder 

channels, constructed channels, and channels containing varying amounts of riparian vegetation. 

The information given for each stream segment 

includes bed and bank descriptions, data tables 

showing channel and hydraulic components, a 

plan view, a representative cross-section plot, and 

color photographs that can be used as a comparison standard to aid in determining roughness coefficients for similarly characterized channels.

Relations derived from the data presented 

relate Manning's roughness coefficient (ri) to various hydraulic components. For gravel-bed 

streams, verified roughness coefficients are related 

to median grain size of the bed material and 

hydraulic radius resulting in an equation that can 

be used to transfer results to similar dryland channels. The equation developed for base values of n 

for gravel-bed channels in Arizona is significantly 

different from similarly derived equations for 

other regions of the United States and the world. 

Another equation was developed to quantify the 

magnitude of the vegetation component of

Manning's roughness coefficient for channels in 

which vegetation is present.

INTRODUCTION

The U.S. Geological Survey, in cooperation with 

the Flood Control District of Maricopa County, has 

been studying the hydraulic effects associated with 

channel-roughness elements in streams in Arizona. 

Manning's roughness coefficient, n, commonly is used 

to represent flow resistance for hydraulic computations 

of flow in open channels. The procedure for selecting n 

values is subjective and requires judgment and skill 

that is developed primarily through experience. The 

expertise necessary for proper selection of roughness 

coefficients can be obtained, in part, by examining 

characteristics of channels that have known or verified 

coefficients. The roughness coefficient can be verified 

by computations made using data from streamflow 

measurements and from measurements of the physical 

features of the channel. Photographs of channel 

segments where n values have been verified can be 

used as a comparison standard to aid in assigning n 

values to similar channels.

Verified values of Manning's n have been 

presented for streams that represent a wide range of 

channel conditions in the United States and other 

countries throughout the world. Past investigations 

include verified roughness coefficients for 50 selected 

stream channels in the United States (Barnes, 1967), 21 

high-gradient streams in Colorado (Jarrett, 1985), 15 

flood plains in the southeastern United States 

(Arcement and Schneider, 1989), 78 rivers and canals 

in New Zealand (Hicks and Mason, 1991), 11 gravelbed streams in California (Limerinos, 1970), 67 gravelAbstract 1
bed streams in Canada (Bray, 1979), and 21 perennial 

channels in New York State (Coon, 1995). However, 

only a few n-verification measurements have been 

obtained for dryland (Graf, 1988) stream channels in 

arid and semiarid regions of the southwestern United 

States (Aldridge and Garrett, 1973). Roughness 

coefficients for a variety of channel conditions are 

needed to substantiate the validity of guidelines 

currently used by hydrologists and engineers to assess 

flow resistance for dryland channels (Aldridge and 

Garrett, 1973; Thomsen and Hjalmarson, 1991).

Purpose and Scope

The purpose of this report is to present verified 

Manning's roughness-coefficient values for 37 

discharge measurements at 14 selected stream sites in 

Arizona (fig. 1). The information includes geometry 

and roughness characteristics of the 14 sites. The 

selected sites represent a wide range of channel 

conditions that include unstable alluvial channels, 

high-gradient boulder-strewn channels, and manmade 

flood-control channels. Of the sites presented, five 

were published in previous n-value assessment reports 

and are included herein to increase the range of stream 

types and transferability of the information (Barnes, 

1967; Aldridge and Garrett, 1973).

The verification-measurement data are used to 

develop empirical relations between channel and 

hydraulic components and Manning's n. The relations 

presented include an equation for gravel-bed streams 

that relates Manning's n to relative roughness and an 

equation to determine the effect of vegetation on total 

roughness. These relations can be used to transfer 

results to similar dryland stream channels in Arizona 

and the southwestern United States.

This study is the second phase of a two-phase 

investigation to assess roughness coefficients for 

stream channels in Arizona. Thomsen and Hjalmarson 

(1991) concluded the first phase by establishing 

guidelines for determining roughness coefficients and 

presented estimated n values for 16 stream channels in 

central Arizona. Some of the 14 verification sites used 

in this report are on the same streams as those 

described by Thomsen and Hjalmarson (1991) but at 

different locations. This report is intended to be used in 

conjunction with Thomsen and Hjalmarson's report to 

aid hydrologists and engineers in assessing and 

estimating n values for channels in arid to semiarid 

environments.

Acknowledgments

B.N. Aldridge, R.D. Jarrett, K.M. Nolan, U.S. 

Geological Survey; Joseph Tram and Ted Lehman, 

Flood Control District of Maricopa County; and H.W. 

Hjalmarson and B.W. Thomsen contributed 

significantly to the technical substance of this report. 

Personnel in the USGS, Tempe Office assisted with 

field and office work during the study.

DESCRIPTION OF STUDY AREA

The basin and range topography typical in most 

parts of Arizona is characterized by steep block-faulted 

mountains separated by gently sloping valleys. 

Dryland streams in the study area cover a wide variety 

of conditions ranging from unstable alluvial channels, 

generally stable channels of cobble to boulder-sized 

bed material, and extremely stable bedrock channels. 

Sand-dominated streambeds commonly are 

characterized by unstable boundary conditions, high 

sediment loads, and long periods of low or no flow 

punctuated by brief floods that increase discharge 

several orders of magnitude within minutes (Parker, 

1995). Although generally more stable than sand 

channels, some gravel-dominated channels in Arizona 

also are ephemeral and subject to flooding for brief 

periods. Flash flooding and the general instability of 

channel beds of natural channels in Arizona can 

complicate the task of obtaining accurate flow-rate and 

channel-geometry measurements that represent 

conditions during peak discharge. Many stream 

channels in urban areas are relatively stable, manmade, 

and composed of either soil cement, concrete, riprap, 

grouted and wire enclosed rock, grass, or a 

combination of these materials (NBS Lowry Engineers 

and Planners and McLaughlin Water Engineers, Ltd., 

1992).

The type, distribution, and density of riparian 

vegetation can vary in the study area. Vegetation types 

found in and along many streams in central Arizona 

include saltcedar, willow, cottonwood, mesquite, palo 

verde, and many brush and grass species. The spatial 

distribution and density of riparian vegetation mainly 

depend on water availability, characteristics of flow, 

and water quality. The few perennial stream channels 

in the study area have vegetation growing parallel to 

base-flow channels; whereas vegetation can be found 

growing randomly throughout the main channel of 

ephemeral streams. In addition, many effluentVerification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
112°

34

33°30'

32°30'

40 MILES

KILOMETERS

Base from U.S. Geological Survey digital data, 1:100,000, 1983

Lambert Conformal Conic projection

Standard parallels 29°30' and 45°30', central meridian -111°30'

EXPLANATION

n-VERIFICATION STUDY SITE AND NUMBER

1. Hassayampa River near Arlington

2. Skunk Creek above Interstate 17

3. Agua Fria River below New Waddell Dam

4. Cave Creek above Deer Valley Road

5. Cave Creek below Cave Buttes Dam

6. Hassayampa River near Morristown

7. Indian Bend Wash above Curry Road

8. Salt River above Interstate 10

9. Verde River below Beeline Highway

10. West Fork Sycamore Creek near Sunflower

11. San Pedro River near Charleston (state map)

12. Santa Cruz River near Cortaro (state map)

13. Verde River near Paulden (state map)

14. Salt River below Stewart Mountain Dam

Figure 1. Study area and n-verification sites in Maricopa, Pima, Cochise, and Yavapai Counties, Arizona.

Description of Study Area 3
dominated streams in the study area (the lower 

Hassayampa River, for example) contain elevated 

nutrient levels resulting in increased vegetation 

growth. Vegetation conditions in dryland streams in 

Arizona can be the primary factor in determining total 

resistance to flow.

Mean annual precipitation in the study area 

ranges from about 7 in. near Phoenix to more than 30 

in. in the adjacent mountain regions. Precipitation in 

Arizona occurs mainly during two seasons, summer 

(June through October) and winter (December through 

March), and rainfall is about equal in each period 

(Sabol and others, 1990). Summer precipitation 

normally is produced by convective thunderstorms. 

These storms are characterized by rainfall of high 

intensity and short duration, which usually cover small 

areas and may result in flash floods (Burkham, 1970). 

Winter precipitation normally is produced by regional 

frontal systems that are characterized by low-intensity 

rainfall of long duration that covers a large areal extent. 

These storms often result in substantial runoff volumes 

and create the potential for major floods. Dissipating 

tropical cyclones, a third storm type in Arizona, occur 

primarily in September and October (Hirschboeck, 

1985; Webb and Betancourt, 1992). These storms can 

cause record floods of regional extent (Aldridge and 

Eychaner, 1984; Roeske and others, 1989). Dissipating 

tropical cyclones and winter-frontal storms can 

generate runoff volumes large enough to require 

discharge from reservoirs in Arizona. Twelve of the 37 

verification measurements presented in this report were 

made during regulated release of waters from upstream 

reservoirs.

FIELD MEASUREMENTS FOR VERIFIED 

ROUGHNESS COEFFICIENTS

Site Selection

The verification-site locations were selected to 

meet, as closely as possible, criteria presented by 

Dalrymple and Benson (1967) for indirect 

measurement of discharge by the slope-area method, 

and guidelines presented by Jarrett and Petsch (1985) 

and Coon (1995) for required hydraulic conditions and 

reach characteristics for accurate n-verification 

measurements. The site conditions that relate to the 

specified criteria are summarized as follows.

1. Discharge mainly stayed within the channel banks, 

and extensive flow in flood plains or overbank 

areas did not exist. Also, the cross-sectional area 

of the channels was fully effective and carrying 

water in accordance with the computed conveyance.

2. For verification measurements in which a welldefined stage-discharge rating was used to obtain 

discharge, good water-surface elevation indicators or high-water marks were available to define 

the water-surface profile.

3. Channels generally were straight and uniform for 

some distance upstream and downstream from the 

reach. Severe channel bends and channel expansions were avoided.

4. Reaches were long enough to develop adequate fall 

according to at least one of the following criteria, 

a. Length of the reach was equal to or greater than

75 times the mean depth, 

b. Fall in the reach was equal to or greater than

the velocity head. 

c. Fall in the reach was equal to or greater than

0.50 ft.

Data Collection

Discharge used for each verification 

measurement was obtained by the current-meter 

method or determined from a well-defined stagedischarge relation (Rantz and others, 1982). For 

verification measurements in which discharge was 

measured with a current meter, the water surface was 

marked with flagging at the time the discharge 

measurement was taken. Adjustments were made to the 

elevation of the markers if the stage or water surface 

was rising or falling during the current-meter 

measurement (Coon, 1995). Crest-stage gages were 

installed at several sites to aid in obtaining accurate 

peak water-surface elevations at cross sections.

A transit-stadia survey was conducted for each 

reach either at the time of the current-meter 

measurement or soon after flow subsided to obtain 

accurate water-surf ace elevations and channelgeometry data. Standard surveying techniques were 

employed throughout the study and are described in 

detail by Benson and Dalrymple (1967). The 

information obtained from the surveys was used to plot 

the channel-geometry data and to determine the 

required channel-geometry components for 

computation of Manning's roughness coefficient.

Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Photographs of the reaches were taken to reflect where 

the major flow-retarding elements in each of the 

channels. For most w-verification measurements, 

photographs of the sites were taken during and after the 

flow.

A particle-size distribution of the bed material 

was measured for most sites because energy losses can 

be influenced by the size of the bed material (Chow, 

1959). For alluvial channels, frequency distributions of 

bed-material size were determined by sieve analysis. 

For bed material too large to sieve, such as gravel-bed 

channels, frequency distributions were obtained by 

measuring the intermediate axis of particles selected at 

random from the study reach (Wolman, 1954; Benson where 

and Dalrymple, 1967). These data were used to 

determine the median grain-size diameter (d50) for 

most of the study sites.

Suspended-sediment samples also were 

collected for many flows because large amounts of 

sediment can become entrained during flooding and 

may require substantial amounts of energy to transport 

the material. As indicated by several investigations 

(Chow, 1959; Costa, 1987; Jarrett, 1987; Glancy and 

Williams, 1994), suspended sediment can have 

discernible effects on the fluid characteristics by 

increasing its density and viscosity, which increase 

flow resistance and the verified n values. For most of 

the flows from which verification measurements were 

made, however, suspended sediment was considered 

wash load and probably had no effect on energy losses.

_. 1.486 D2/3 cl/2

V = ———— K b ,

V = mean velocity of flow, in feet per second;

R = hydraulic radius, in feet;

Sf = energy gradient or friction slope, in feet

per foot; and 

n = Manning's roughness coefficient.

The continuity equation is expressed as:

Q = AV, (2)

Q = discharge, in cubic feet per second;

A = cross-sectional area of channel, in square

feet; and 

V = mean velocity of flow, in feet per second.

Substitution of equation 1 for V in equation 2 yields a 

variation of Manning's equation often used to compute 

discharge in open channels:

G = (3)

COMPUTATION OF REACH PROPERTIES 

AND ROUGHNESS COEFFICIENTS

The fundamental equations on which many 

open-channel hydraulic computations are based 

include the Manning's equation, the continuity 

equation, and the energy equation. The computer 

program NCALC, developed by Jarrett and Petsch (h + k 

(1985), is based primarily on these equations and was 

used to compute most of the values of Manning's n in where 

this report. The equations are essentially identical for 

sites presented in this report for which verified n values 

were published previously. Manning's equation is 

defined as:

The equation was developed for conditions of 

uniform flow in which the water-surface slope and 

energy gradient are parallel to the streambed, and the 

area, depth, and velocity are constant throughout the 

reach. Equation 3 is assumed for nonuniform reaches if 

the energy gradient is modified to reflect only the losses 

resulting from boundary friction (Barnes, 1967). The 

energy equation for a nonuniform stream channel reach 

between sections 1 and 2 (fig. 2) is:

h =

h =

(1)

elevation of the water surface at the 

respective section above a common 

datum, in feet;

velocity head at the respective section 

equals aW2^, in feet; 

= energy loss due to boundary friction in 

reach, in feet;

Computation of Reach Properties and Roughness Coefficients 5
CROSS-SECTION 1

PLAN VIEW

•2?*fl WAOrENT hf + k(btiv )

PROFILE VIEW 

Figure 2. Open-channel flow reach in plan and profile views (modified from Dalrymple and Benson, 1967, fig. 1).

Ahv = upstream velocity head minus the

downstream velocity head, in feet; 

k(Ahv) = energy loss due to acceleration of 

velocity in a contracting reach, or 

deceleration of velocity in an expanding 

reach, in feet; and

k = coefficient assumed to be equal to 0 for 

contracting reaches, and 0.5 for 

expanding reaches (Barnes, 1967).

where

oc = velocity-head coefficient', and 

g = acceleration due to gravity, in feet per 

second per second.

In computing the values of n using this method, 

the value of cc is always considered to be 1.00. This

requirement limits verification computations to unit 

channels that do not require segmenting or subdividing 

(Jarrett and Petsch, 1985). Although cc can be much 

larger than 1.00 in natural channels (Jarrett, 1985), any 

resulting error in the computation of n is assumed to be 

minimal because the effect of cc actually depends on 

the relative difference between the velocity-head 

coefficients from upstream and downstream cross 

sections rather than their actual magnitudes (Coon, 

1995).

The friction slope, Sp to be used in Manning's 

equation is defined as:

hf Ahv -k(Ahv )

(5)

where

Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
A/?= difference in water-surface elevation at

the two sections, in feet; and 

L= length of the reach (Dalrymple and 

Benson, 1967), in feet.

In Manning's equation, the quantity (1.486/rc) 

AR2/3 is called conveyance, K, and is computed for each 

cross section. The mean conveyance in the reach 

between any two sections is computed as the geometric 

mean of the conveyance of the two sections. The 

discharge equation in terms of conveyance is expressed

as:

Q =

.1/2 (6)

In this investigation, n is computed for each 

reach of known discharge, the water-surface profile, 

and the hydraulic properties of the reach as defined by 

the cross sections. The following equation was 

primarily used to compute n for this study and is 

applicable to a multisection reach of M cross sections, 

designated 1,2,3,... M - l,M:

where

,(7)

1.486

e

p-[(fcA/. v ) 1 _ 2 +(tAftv ),_ 3

^-2^2-3

t^i 77 t^T ^.-^^T 77

+ ... (A'A/z v )

L (M-1) -Af

Z (Af-l) ZM

) -Af]

(3 = (/I + /I V )

Z = AR2/3 (Barnes, 1967).

ASSUMPTIONS AND LIMITATIONS

Although efforts were made to strictly follow the 

site-selection and data-collection criteria, assumptions 

were required for some of the verification 

measurements as channel and hydraulic conditions 

were not always ideal. The main sources of potential 

errors in calculations of roughness coefficients for 

dryland channels include changing boundary and 

vegetation conditions, discharge measurement 

uncertainties, and changing bedforms. The verification 

measurements presented in this report are qualified or 

rated on the basis of these four factors. Additionally,

transfer of results presented in this report to similar 

sites may be limited because of uncertainties 

associated with extrapolating n values obtained for 

relatively low flows to flows of greater magnitudes.

The accuracy of verification measurements 

presented in this report is rated as either good, fair, or 

estimated. These categories correspond to potential 

percent errors of less than 10, 15, or 20 percent, 

respectively. Verification measurements with an error 

of greater than 20 percent were not considered for 

publication in this report.

Changing Boundary Conditions

In the performance of hydraulic computations of 

flow in streams that are dominated by sand-sized 

material, constant-bed geometry often is assumed to 

persist throughout flow events. Several investigators 

indicate sand-dominated streams do not scour 

appreciably in a uniform segment of river channel 

(Culbertson and Dawdy, 1964; Benson and Dalrymple, 

1967). Although most of the channel segments studied 

for this report are uniform, scour of substrate material 

during the rise and peak of the flow and subsequent 

backfill during the flow recession requires 

consideration. Accuracy ratings for the ^-verification 

measurements made in sand-dominated streams where 

changing boundary conditions are possible, thus, were 

downgraded according to the potential amount of scour 

and fill.

Although the channel-geometry changes may 

not be as significant as with sand-dominated streams, 

flood-stage flows in gravel-bed streams also may 

mobilize and transport bed material. Hydraulic 

components measured for the verification measurements made in gravel-bed streams, however, probably 

were not large enough to cause a considerable change 

in boundary conditions resulting from substantial 

movement of the bed material.

Changing Vegetation Conditions

In arid and semiarid environments, vegetation 

commonly grows throughout the main channel of 

dryland streams. The vegetation can significantly 

impede flow and result in large increases in roughness 

coefficients, as suggested by several past studies 

(Aldridge and Garrett, 1973; Thomsen and 

Hjalmarson, 1991). The force and power of flows,

Assumptions and Limitations
however, can lay over and even remove vegetation, 

thereby decreasing channel roughness and increasing 

channel conveyance (Burkham, 1976; Phillips and 

Hjalmarson, 1994).

The flow-induced changes in vegetation 

conditions are commonly assumed to occur before 

peak flow, and postflow vegetation conditions are 

assumed to reflect the roughness conditions when the 

high-water marks were formed. However, for certain 

conditions, this may be an erroneous assumption. 

Water-level indicators in vegetated channels surveyed 

following flows may not actually represent the watersurface during the time of peak discharge. The force 

and power of flow may be large enough to substantially 

affect (lay over or remove) vegetation just before peak 

flow and thus cause the water surface to drop 

dramatically because of the decrease in flow resistance. 

This phenomenon may result in a lower water-surf ace 

elevation during peak discharge than that suggested by 

the high-water indicators. This phenomenon may have 

occurred for the flow of February 9, 1993, at 

Hassayampa River near Arlington. The high-water 

indicators may actually have been deposited before and 

not during peak discharge. This verification 

measurement, therefore, was rated as estimated. 

Vegetation documented during and shortly after flow at 

the other study sites appeared to have little or no 

change compared to preflow conditions.

Uncertainties of Discharge Measurements

The accuracy of the verified n values directly 

depends on the precision of the measured discharge. As 

mentioned previously, discharge was determined either 

by a current-meter measurement or from a well-defined 

stage-discharge relation. Current-meter measurements 

made by the USGS are rated as excellent, good, fair, or 

poor depending on factors that include the number of 

subsections in the measurement, stability of the 

•channel, and accuracy of the equipment (Rantz and 

others, 1982). These ratings correspond to possible 

errors of less than 2, 5, 8, or greater than 8 percent of 

the actual discharge, respectively. Errors for discharges 

determined from a well-defined and stable stagedischarge relation are assumed to be less than 

10 percent. Discharge accuracy is considered when 

determining the overall accuracy rating for each of the 

n-verification measurements.

Flow Depth and Magnitude

In the absence of bank vegetation and other 

obstructions, the roughness for low flows in a uniform 

gravel-bed stream generally decreases with increasing 

depth of flow. As flow approaches bank-full stage, 

however, roughness may asymptotically approach a 

constant value, as shown by several previous 

investigations (Limerinos, 1970; Bray, 1979; Sargent, 

1979; Griffiths, 1981; Jarrett, 1985; Blodgett, 1986; 

Hicks and Mason, 1991; Coon, 1995).

The basic roughness coefficient for these streams 

should not vary greatly with depth of flow if the 

relative roughness is greater than about 5 (Benson and 

Dalrymple, 1967). Many of the verification 

measurements presented in this report, however, have 

values of relative roughness that are less than or close 

to 5, and the variation in Manning's roughness 

coefficient with depth is apparent.

For many previously published ^-verification 

manuals and for this report, verified n values are 

obtained from flow discharge data that may not result 

in a reliable value for studies requiring estimates of 

roughness coefficients for design purposes. Design 

discharge typically is determined on the basis of the 

estimated flood having a particular recurrence interval 

(100-year flood, for example). Roughness-coefficient 

verification studies, however, generally are limited to 

flows that may not exceed even the 5-year flood (Wahl, 

1994). This limitation is caused by the relatively short 

duration of /i-value studies and the difficult logistics 

involved in making ^-verification measurements 

during floodflows. Roughness coefficients can be 

extrapolated to the design discharges using relations 

between hydraulic components, such as R and n\ 

however, large uncertainties may be associated with 

these extrapolations (Wahl, 1994). Water-resource 

managers and engineers need to be aware of these 

limitations when using this and other ^-verification 

manuals.

For sand-dominated streams, the amount of 

variance in Manning's n with depth is much more 

difficult to describe and quantify compared to gravelbed streams. Roughness in sand-dominated streams 

depends not only on grain size but also on flow regime 

and type of bedform manifested. As indicated by the 

verification measurements made at the Hassayampa 

River near Morristown, the relation of Manning's n to 

flow depth (hydraulic radius) can actually be the 

inverse of the relation for gravel-bed streams (fig. 9C, 

see p. 37).

8 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Changing Bed Forms

Resistance to flow can vary greatly in sand 

channels because the bed material is unstable and may 

take on different configurations or bedforms 

throughout a single period of flow. The type of bedform 

is a function of many components that include flow 

velocity, grain size, shear stress, temperature, and other 

variables (Aldridge and Garrett, 1973). The magnitude 

of Manning's roughness coefficient may relate directly 

to the type of bed form that is manifested, which makes 

accurate assessment of n values in sand channels a 

difficult and complex procedure.

On the basis of data obtained with the aid of 

laboratory flumes, Simons and Richardson (1966) 

proposed that median grain size and stream power can 

be used to determine the flow regime and the type of 

bed form that will develop in sand channels. Stream 

power is determined from the equation:

where

SP

62

SP = 62RSV, (8)

stream power, in foot-pounds per second 

per square foot;

specific weight of water, in pounds per 

cubic foot;

R = hydraulic radius, in feet;

S = water-surface slope, in feet per foot; and

V = mean velocity, in feet per second.

Other investigators have modified results 

presented by Simons and Richardson (1966, p. J24, 

fig. 28) in order to develop practical criteria for 

determining Manning's roughness coefficient in sanddominated streams (Benson and Dalrymple, 1967). As 

shown in figure 3, flow in sand channels can be 

classified as either lower-regime or upper-regime flow 

separated by a transition zone.

In lower-regime flow (fig. 3), the bed may have 

a plane surface with little or no movement of sand or 

small uniform waves (ripples), or large irregular waves 

(dunes) that are formed by sediment moving 

downstream. Water-surface undulations manifested in 

lower-regime flow generally are out of phase with the 

bed surface. The fact that the water surface is out of 

phase with the bed surface is a positive indication that 

the flow is tranquil or subcritical (Froude number < 1; 

Simons and Richardson, 1966, p. J9).

The bed configuration in the transition zone can 

be erratic and may range from that typical of the lowerflow regime to that typical of the upper-flow regime 

depending mainly on antecedent conditions (Simons 

and Richardson, 1966, p. Jll). Resistance to flow and 

sediment transport also have the same variability as the

Bb°rO

£§ 

^g

LU 

DC

co

0.8

CA DC Q: LU 0.6

So

DC^ 0.4 ujO 

> o

>LU

Oco

0.2

0.1

Upper regime

Lower regime

0.2 0.4 0.6 0.8 

MEDIAN GRAIN SIZE, IN MILLIMETERS

1.2

Figure 3. Relation of stream power and median grain size to form of bed roughness. (Modified from 

Benson and Dalrymple, 1967.)

Assumptions and Limitations
bed configuration in the transition zone. A 

discontinuity in stage-discharge relations may occur at 

the transition between lower-regime and upper-regime 

flow (Culbertson and Dawdy, 1964).

In upper-regime flow, the bed may have a plane 

surface or it may have long smooth sand formations in 

phase with the surface waves (Leopold and others, 

1964, and Karim, 1995). These waves are known as 

standing waves or antidunes where, during upperregime flow conditions, roughness can be much larger 

than for plane-bed conditions (Simons and Richardson, 

1966). As the size of the antidunes grow, the watersurface slope on the upstream side of the waves 

becomes steeper, and the antidune may eventually 

collapse. Following collapse of antidunes, the flow 

generally will shift back to plane-bed conditions. If the 

antidunes do not collapse, however, resistance to flow 

can be about the same as for plane-bed conditions. 

When antidune formation occurs in upper-regime flow 

and the water and bed surfaces are in phase, the flow is 

rapid or supercritical (Froude number > 1; Simons and 

Richardson, 1966, p. J9).

On the basis of criteria presented by Simons and 

Richardson (1966) and Benson and Dalrymple (1967), 

upper-regime flow conditions were exhibited for all 

verification measurements that were made in sanddominated streams (sites 6 and 12, fig. 1). In addition 

to the uncertainties associated with changing boundary 

conditions for sand channels, the possibility of 

intermittent antidune formation and subsequent 

collapse of the antidunes could result in intermittent 

surging of the water surface along the banks of the 

channel. The surges may result in super elevation of 

high-water marks that normally are surveyed when the 

flow subsides. This phenomenon occurred on March 6, 

1995, about 1,000 ft upstream from the USGS 

streamflow-gaging station at Hassayampa River near 

Morristown. Discharge was about 9,000 ft3/s, and the 

authors witnessed trains of large antidunes (about 6 ft 

from trough to crest) that were forming and collapsing 

at regular intervals. The collapse resulted in a surge of 

the water surface along the channel banks of more than 

1 ft in elevation. Following collapse of the antidunes, 

the flow would return to plane-bed conditions until 

another train of antidunes formed.

Intermittent surging of the water surface causing 

super elevation of the high-water marks along the 

channel banks complicates the task of obtaining 

accurate and representative water-surface elevations 

for ^-verification measurements made in sand

channels, and may introduce errors into the hydraulic 

computations. The accuracy of the verification 

measurements that were made in sand channels, 

therefore, was qualified according to the potential 

amount of error resulting from difficulties in obtaining 

accurate water-surface elevations and channelboundary configuration.

PRESENTATION OF VERIFIED 

ROUGHNESS COEFFICIENTS

A total of 37 verified n values are presented for 

discharge measurements at 14 separate stream 

locations in Arizona. Data for 4 of the 14 sites are from 

Aldridge and Garrett (1973), and data for Salt River 

below Stewart Mountain Dam is from Barnes (1967). 

General information is presented on the location of the 

site, drainage area of the stream, date and discharge of 

each measurement, computed roughness coefficients 

for the reach, median size of bed material (if available), 

concentration of suspended sediment (if available), and 

a general description of the channel. Tabulated data 

presented are from field surveys and hydraulic 

computations. These data include average values for 

area, top width, hydraulic radius, mean velocity, and 

Froude numbers. The total reach length and fall in 

water surface also are included. Plan-view sketches are 

presented to show the location of the cross sections and 

general shape of the channel. A representative cross 

section is illustrated with water-surf ace elevations 

shown for each flow. Information for two or more 

discharges is available for most sites to show changes 

in roughness with depth. The changes are demonstrated 

by plots of Manning's n and hydraulic radius. The 

assumption is made that hydraulic radius closely 

approximates mean flow depth for each of the sites. 

Color photographs are presented for each study reach 

to be used as a comparison standard to aid transfer of 

results to sites with similar channel and hydraulic 

characteristics. Selected photographs also show flow 

conditions at the time of the measurement. The average 

water level corresponding to the measured flow is 

indicated in certain photographs by a horizontal rod. 

The frame of the square grid (painted orange) in several 

photographs has an outside dimension of 1.5 ft and an 

internal grid spacing of 1 in.

10 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Hassayampa River near Arlington

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Remarks:

Latitude 33°20'50", longitude 112°20'30". Reach begins about 1,000 ft downstream 

from streamflow-gaging station 09517000, Hassayampa River near Arlington.

1,471 mi2.

Low-flow channel = 87 mm (0.28 ft); Overbank area = 0.53 mm (0.0017 ft).

The channel is straight and uniform throughout the study reach, and cross sections 

are trapezoidal in shape. The low-flow channel is approximately 25 ft wide, and the 

bed consists primarily of cobble-sized material. Overbanks are mainly composed of 

coarse sand and small gravel-sized material. Grass and small brush grow on the 

overbanks and appear to have kept the overbank-bed material fairly stable during the 

flow of February 9, 1993. The site is in a section of the river that is considered 

intermittent. The nearly constant low flows are dominated by irrigation return flow.

Following the flow of February 9, 1993, the grass was in a prone position and the 

brush was bent in the direction of flow. The timing of the vegetation changes is not 

known. A thin layer of fine sand appears on the overbanks that probably was 

deposited following the peak. No significant amount of scour or fill was apparent in 

the reach during any of the flows recorded. For the three low-flow verifications, 

water mainly consisted of irrigation return flow and appeared to be clear [suspended 

sediment was 172.8 mg/L for a sample taken during a low-flow period (June 20, 

1995) and was considered as wash load]. Suspended-sediment concentrations can 

exceed 35,000 mg/L for flows that result from runoff in upstream basins.

Table 1. Flow data and computed roughness coefficients, Hassayampa River near Arlington

Date of flow

02-09-93

07-06-94

06-16-94

06-15-94

Discharge, in cubic feet per second

5,580

80.5

45.5

17.0

Roughness coefficient

0.027

.034

.036

.036

Rating

Estimate

Good

Good

Good

Table 2. Average-reach properties, Hassayampa River near Arlington

Date

02-09-93

07-06-94

06-16-94

06-15-94

Area, in 

square feet

725

24.8

17.5

9.29

Top width, in 

feet

174

18.2

17.3

15.7

Hydraulic 

radius, in 

feet

4.12

1.29

.97

.58

Mean 

velocity, in feet 

per second

7.75

3.26

2.61

1.86

Froude 

number

0.67

.49

.46

.43

Total 

length, in 

feet

715

571

571

571

Total 

fall, in feet

2.44

2.22

2.22

2.25

Water-surface 

slope

0.0034

.0039

.0039

.0039

Hassayampa River near Arlington 11
Hassayampa River near Arlington—Continued

JULY 6, 1994 

JUNE 15, 1994

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

STATIONING FROM LEFT BANK, IN FEET

Figure 4A Cross-section 3, Hassayampa River near Arlington.

31

Figure 4B. Plan view, Hassayampa River near Arlington. 

12 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Hassayampa River near Arlington—Continued

0.045

LLJ

0.040

LU

o

O

CO 

CO 

LU

O

DC 

CO

0.035

0.030

0.025

0.020 i i i I i i i i I i i i i I i i i i I i i i i I i i i i I i i i i I i i i i I i i i i

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 

HYDRAULIC RADIUS, IN FEET

Figure 4C. Manning's n and hydraulic radius, Hassayampa River near Arlington.

LU

O 

DC 

LU

100

80

60

20

0

LOW- FLOW 

CHANNEL

0.1 0.2 0.5 1 2 5 10 20 50 100 200 500 1,000 

PARTICLE SIZE, IN MILLIMETERS

Figure 4D. Particle-size distribution for bed material, Hassayampa River near 

Arlington.

Hassayampa River near Arlington 13
Hassayampa River near Arlington—Continued

Figure 4E. View of typical bed material for low-flow channel, Hassayampa River n 

Arlington. The square grid (painted orange) has an outside dimension of 1.5 feet and 

internal grid spacing of 1 inch.

near 

an

5scr**H-.£ ••''• ,'- -' '5

Figure 4F. View from right bank showing a current-meter measurement made in the low-flow 

channel, Hassayampa River near Arlington.

14 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Hassayampa River near Arlington—Continued

Figure 4G. View looking upstream from midreach of low-flow channel, Hassayampa River 

near Arlington.

^&Kmmfmxm

Figure 4W. View from right bank and midreach looking downstream following flow of 

February 9, 1993, Hassayampa River near Arlington.

Hassayampa River near Arlington 15
Skunk Creek above Interstate 17

Reach location;

Drainage area: 

Bed-material size: 

Channel description:

Remarks;

Latitude 33°43'56", longitude 112006'57". Reach begins about 1,000 ft upstream 

from streamflow-gaging station 09513860. Skunk Creek near Phoenix.

64.9 mi2.

d50 - 88 mm (0.29 ft).

The constructed channel is fairly uniform, and bed material is mainly cobble-sized 

clasts partially surrounded by finer silt- and sand-sized material. Vegetation consists 

of brush of moderate spatial density and grows randomly throughout the channel. 

The stream is ephemeral and flow is unregulated.

Nine verification measurements were made for several stages of vegetation growth 

within the study reach. The first measurement on March 1,1991, was made when the 

vegetation was fully grown (average height, about 5 ft). Verifications 2-5 were made 

after the reach had been artificially maintained and cleared of all the vegetation. 

Verifications 6 and 7 were made during a period of regrowth (average height was 

about 2 ft). Verifications 8 and 9 were made after the vegetation was again fully 

grown (average height, about 5 ft). Although flow magnitude was greater for the 

postmaintenance measurement of January 26, 1995, compared to the 

premaintenance measurement of March 1, 1991, the water-surface elevations were 

lower (fig. 5A). The vegetation was little affected by flow for all measurements. 

According to survey data, channel geometry and bed conditions did not appear to 

change significantly after clearing of the vegetation. For the flow of September 28, 

1995, the suspended-sediment concentration was 198.8 mg/L and was considered 

wash load. Suspended-sediment concentrations probably did not exceed wash-load 

conditions for any of the verification measurements.

Table 3. Flow data and computed roughness coefficients, Skunk Creek above Interstate 17

Condition of reach

Premaintenance of vegetation

Postmaintenance of vegetation

Do.

Do.

Do.

Partial regrowth of vegetation

Do.

Regrowth of vegetation

Do.

Date of flow

03-01-91

01-26-95

01-05-95

01-26-95

01-05-95

09-28-95

11-01-95

08-14-96

09-02-96

Discharge, in cubic 

feet per second

618

723

393

180

168

822

500

403

215

Roughness 

coefficient

0.048

.031

.034

.035

.037

.035

.039

.048

.052

Rating

Good

Fair

Fair

Good

Good

Fair

Fair

Fair

Fair

16 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Skunk Creek above Interstate 17—Continued

Table 4. Average-reach properties, Skunk Creek above Interstate 17

Date

03-01-91

01-26-95

01-05-95

01-26-95

01-05-95

09-28-95

11-01-95

08-14-96

09-02-96

Area, 

in square 

feet

176

140

97.5

63.2

57.6

162

130

126

88.1

Top width, 

in feet

88.3

81.8

76.1

70.8

69.6

84.2

80.7

78.6

73.5

Hydraulic 

radius, 

in feet

1.97

1.71

1.28

.90

.83

1.91

1.60

1.60

1.20

Mean velocity, 

in feet 

per second

3.52

5.18

4.06

2.91

3.07

5.09

3.16

3.24

2.48

Froude 

number

0.44

.70

.63

.55

.61

.64

.54

.45

.40

Total 

length, 

in feet

658

677

677

677

677

677

677

677

677

Total 

fall, 

in feet

3.61

3.93

4.19

3.92

4.55

4.18

3.71

3.54

3.67

Watersurface 

slope

0.0055

.0058

.0062

.0058

.0067

.0062

.0055

.0052

.0054

18

17

UJ

— 2

14

13 SECTION 2

12 

-10 0 10 20 30 40 50 60 70 80

STATIONING FROM LEFT BANK, IN FEET 

Figure 5A. Cross-section 2, Skunk Creek above Interstate 17.

90 100 110

Skunk Creek above Interstate 17 17
Skunk Creek above Interstate 17—Continued

Figure 5B. Plan view, Skunk Creek above Interstate 17.

g

1- 

Lu 0.050

0

LL

LL.

g 0.045

0

CO 

CO

^ 0.040

X

CD

Z)

§• 0.035

CO

CD

1 0.030

0.025 —————— ———

i t \ ,, t I f i<> i t v J I I r t Ir l Is l l J <-,"!< i t i s l i i

L * j:

I <j PREMAINTENANCE H Q |I

- ;* iPOSTMAINTENANCE - — ^ —

: D PARTIAL REGROWTH 3

I • FULL REGROWTH :

- o ^

_ <TMA Z

r D i

L * _:

~ i t 1 i t- M ! l J I1 . I l M M I 1 1' : I i' 'i 1 h i < f.....\ 1 it ...1 1

0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.

HYDRAULIC RADIUS, IN FEET

Figure 5C. Manning's n and hydraulic radius, Skunk Creek above Interstate 17. 

18 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
O

(D (D

0) 0"

1

H -n

a°i 

m

_. CD -

"° 

<

III - Q) CD W =.

o, a. II

W ju 

Q.' ^3 S

II "

tn 

O

alQJ Q)

&£Q) CD

CQ _,. 3. ^i

/««' •*"' • fcV <-,If TKF V'*-f JH«Plt *"J^M^^»S fe5^ ¥l^iS^^''iiii

(D Ol

(73 *•

3 ^~

O 

8CD ^~&) CTi

CD

CUMULATIVE PERCENTAGE FINER

c3 ^*

O3(D ^-fi) U" O

(D

a I

O 

Oi-h5' c

CD Q.
Skunk Creek above Interstate 17—Continued

Figure 5F. View from left bank and bottom of reach looking upstream during flow of March 1, 

1991, Skunk Creek above Interstate 17.

Figure 5G. View from midchannel looking upstream following flow of March 1, 1991, Skunk 

Creek above Interstate 17. Vegetation was little affected by flow.

20 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Skunk Creek above Interstate 17—Continued

~ 

-

.•^S"?^*S£,"-

.

.,"

Figure 5H. View from midchannel and bottom of reach looking upstream following artificial 

maintenance of the channel vegetation, May 23, 1994, Skunk Creek above Interstate 17. 

The crest-stage gages were installed in surveyed cross sections to aid in obtaining accurate 

water-surface elevations and profiles.

I

Figure 5/. View from midchannel looking upstream during flow of January 5, 1995, Skunk 

Creek above Interstate 17.

Skunk Creek above Interstate 17 21
Skunk Creek above Interstate 17—Continued

Figure 5J. View from midchannel looking upstream at regrowth of vegetation, Skunk Creek 

above Interstate 17. The brush is about 2 feet in height and was little affected by flow.

•-^if*<r-~-**br ^.''•»••'^ fit ^1fcr^^*»i J~^^»TS*^"^-*"V5! ' «. ••Mmjer-^A^i T-^tsJtvi. ^>TW^^SC *s •sSi- * ».- *'•"•*-tfk^i-^NiS^ifcS^c- . ^sJ-"-3**^: ->-*£&^2. ^

*^^^©^i^^i|^ 

- :*" ^-^:*?5^ --^0^*^1-4 • ^

^J^- J ^fc*l*>fe^^; ^*i '£$?&? :JfcC^tri%*Tl!TM* 

fctr -it^^^iSffiSK^

Figure 5/C. View from midchannel looking upstream following flow of August 14, 1996, Skunk 

Creek above interstate 17.

22 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Agua Fria River below New Waddell Dam

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Latitude 33°50'03", longitude 112°16'33". The reach begins about 3,000 ft below 

New Waddell Dam.

1,459 mi2.

d50 = 82 mm (0.27 ft).

The channel generally is straight throughout the reach. The reach narrows 

considerably from cross-sections 1 to 4. A small ridge is along the middle of the 

reach with poorly defined low-flow channels on either side. Outcroppings of 

bedrock are near the left bank of cross-sections 3 and 4. Saltcedar ranges in height 

from about 5-10 ft in the reach and grows mostly along the middle ridge. The 

channel bed consists mainly of small- to medium-sized cobbles. The stream was 

perennial before construction of Waddell Dam.

Remarks: Following the recorded flow, the saltcedar appeared to be little affected by the flow.

A small nonconveying area is at the right bank of cross-section 4 (investigation of 

the debris deposited by the flow indicated a zone of separation and a backwater area) 

that was not included in the verification computations.

Table 5. Flow data and computed roughness coefficient, Agua Fria River below New Waddell Dam

Table 6.

Date

Date of flow

02-09-93

Average-reach

Area, 

in square 

feet

02-09-93 1,978

Discharge, in cubic feet per second

properties,

9,000

Agua Fria River below New Waddell

Hydraulic 

Top width, radius, 

in feet in feet

418 4.78

Mean 

velocity, in feet 

per second

4.6

Roughness coefficient

0.042

Dam

Froude Total length, 

number in feet

0.37 447

Rated

Fair

Total fall, Water-surface 

in feet slope

1.11 0.0025

40

35

30

FEBRUARY 9, 1993

^SECTION 2

O

< 25

LLJ

20

15 

-50 0 50 100 150 200 250 300 350 400 450 500

STATIONING FROM LEFT BANK, IN FEET 

Figure 6A Cross-section 2, Agua Fria River below New Waddell Dam.

Agua Fria River below New Waddell Dam 23
Agua Fria River below New Waddell Dam—Continued

NONCONVEYING AREA

Figure 6B. Plan view, Agua Fria River below New Waddell Dam.

100

LU 

CD

LU 

O 

DC 

LU 

Q_

LU

3

=> 

^ 

Z) 

O

100 

PARTICLE SIZE, IN MILLIMETERS

1,000

Figure 6C. Particle-size distribution for bed material, Agua Fria River below New 

Waddell Dam.

24 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Agua Fria River below New Waddell Dam—Continued

Figure 6D. View of typical bed material in channel reach, Agua Fria River below New 

Waddell Dam. The square grid (painted orange) has an outside dimension of 1 .5 feet and an 

internal grid spacing of 1 inch.

Figure 6£. View from bottom of reach looking upstream on March 10, 1993, Agua Fria River 

below New Waddell Dam.

Agua Fria River below New Waddell Dam 25
Agua Fria River below New Waddell Dam—Continued

*t*&x$iB%?*.$ &&*:*$5Jp * • ^ 7^f€l

^M^^^f^J^^^

Figure 6F. View from midchannel looking toward left bank of cross-section 4, Agua Fria River 

below New Waddell Dam.

Figure 6G. View from midchannel in cross-section 2 of typical vegetation in the reach, Agua 

Fria River below New Waddell Dam. Length of measuring rod, 6 feet. Photograph taken at 

time of survey on May 19, 1993.

26 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Cave Creek above Deer Valley Road

Reach location:

Bed-material size: 

Channel description:

Remarks:

Latitude 33°41'13", longitude 112°03'32". Reach ends about 1,000 ft above Deer 

Valley Road.

d50 = 9] mm (0.30 ft).

The channel is straight and uniform throughout the reach. The cross sections are 

trapezoidal in shape, and vegetation of moderate spatial density is along the banks. 

Bed material found in the reach is mostly small- to medium-sized cobbles. The 

stream is ephemeral, and flow is regulated by Cave Buttes Dam.

The bank vegetation probably had a discernible effect on total flow retardance for 

the two larger flows. This bank vegetation was little affected by flows. The 

suspended-sediment concentration was 228 mg/L for the flow on January 9, 1995, 

and is assumed to be indicative of suspended-sediment concentrations for all three 

flows. The suspended sediment was regarded as wash load and was considered to 

have negligible effects on n values.

Table 7. Flow data and computed roughness coefficients, Cave Creek above Deer Valley Road

Date of flow

01-06-95

01-09-95

01-10-95

Discharge, in cubic feet per second

297

193

39

Roughness coefficient

0.033

.033

.034

Rating

Estimate

Good

Good

Table 8. Average-reach properties, Cave Creek above Deer Valley Road

Date

01-06-95

01-09-95

01-10-95

Area, 

in square 

feet

58.2

48.9

17.5

Hydraulic 

Top width, radius, 

in feet in feet

22.8 2.33

21.8 2.07

17.4 .98

Mean velocity, 

in feet 

per second

5.13

3.96

2.32

Froude 

number

0.57

.49

.42

Total length, 

in feet

225

225

225

Total fall, 

in feet

1.03

.65

.55

Watersurface 

slope

0.0046

.0029

.0024

Cave Creek above Deer Valley Road 27
o

5* 5'

3

o

F Roughness

O

Si

o13'%31i

S§S.5*

ci.

Q)

Q.

O O

3a

1

(0

3Q)

O3"Q)

33(D(05'

>

s

n -«j PO

Tl03

I! MANNING'S ROUGHNESS COEFFICIENT (n) ^ ID m' 

^ ooooop< (D bbbbbb- ^j N)N)COCO^*>./-s 0 

0ooiooi

0 oiO

bo

^

03

D DD' _L

CQw"

3031 

c

<

Q- I

03 •<

c a^ 3] r^ ° > -^

S 

c

Io

y 3] _.

0 § 

b 3 

§ CD CO

O - CD Z ^ 

CD Tl 00 ^- 

m

0) fn CT H

o

0 00

D

CDCD

of !»= N)CD 

<

TJos 1°

1111111:11 I 1 1 1 1 1 :1 1 1 1 I 1 1 1 1

~ ~

- """""""" ^^ —— _ _

- — 

— _- — _ „

—— •:.: ' *~———— ————

-~ ~

_-TM. , ————

- TM «H.

————— , , —————— I *: [

—— ——— ___ ——

o

i i i i 1 t 1 i i 1 i i i i 1 i i i i i i i i

CD

O

CDCD

7?

03CTiCD

DCDCD

<

9Lcb~

<

TJ o03 Q.

o0) 

0O

ID 

§O

o w ww | o'

N)

O

D CD

CD ^<

TJ oa

ELEVATION, IN FEET

-i ->• -1 -1 N) | 0) -«J 00 CO 

O

CO 01

3oz z o

3 °

O

m 

3]DO -•• 

> 01

ZTl

m=1 

8

TT

0*•

N) Q) ^ $•

m

Ln

'Z

C 

C

3 

5

CO 0>

CO COCO CO

Ol Ol

0

D 0 0

^SL 0"

X o0) Q.O 

O

r+5' C

0 Q.
Cave Creek above Deer Valley Road—Continued

LU 

CD

LU 

O 

CC 

LU 

D.

O

100

80

60

40

20

10 100 

PARTICLE SIZE, IN MILLIMETERS

1,000

Figure 7D. Particle-size distribution for bed material, Cave Creek above Deer 

Valley Road.

Figure 7E. View of typical bed material in channel reach, Cave Creek above Deer Valley 

Road The square grid (painted orange) has an outside dimension of 1.5 feet and an internal 

grid spacing of 1 inch.

Cave Creek above Deer Valley Road 29
Cave Creek above Deer Valley Road—Continued

Figure 7F. View from bottom of reach looking upstream during flow of January 9, 1995, Cave 

Creek above Deer Valley Road.

Figure 7G. View from top of reach looking downstream, Cave Creek above Deer Valley 

Road. Rod indicates water-surface elevation for the peak flow of January 6, 1995.

30 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Cave Creek below Cave Buttes Dam

Reach location:

Bed-material size: 

Channel description;

Remarks:

Latitude 33°42'55", longitude 112° 02'44". Reach begins about 500 ft below Cave 

Buttes Dam.

See channel description.

The constructed reach is straight, and cross sections are trapezoidal in shape. The 

bottom and sides of the channel are composed of rounded cobbles imbedded in a 

matrix of cement (approximate mean diameter of the rock projections was 80 mm, 

about half of which seemed to be exposed to flow). Roughness elements are constant 

throughout the reach. The channel gradient increases from about 0.002 ft/ft at crosssection I to about 0.010 ft/ft at cross-section 8. The stream is ephemeral, and flow is 

regulated by Cave Buttes Dam.

Roughness coefficients were determined for both subcritical (Froude number < 1.0) 

and supercritical (Froude number > 1.0) flow regimes. The Froude number at crosssection 5 approximated 1.0 (critical flow) for both flows and was not incorporated 

in the analyses. A decrease in Manning's n occurred when flow transitioned from 

subcritical flow to supercritical flow. This change could be the result of unstable 

flow conditions as investigated by Koloseus and Davidian (1966). According to their 

results, roughness depends on the Froude number when unstable flow conditions 

occur (generally flow is considered unstable if Froude numbers are larger than about 

1.6). Although Froude numbers in the supercritical reach averaged about 1.6 or less, 

the Froude number increased to over 1.8 in cross-section 8. The suspended-sediment 

concentration was 224 mg/L for the flow of January 9, 1995, and may be indicative 

of suspended-sediment concentration for the flow on November 2, 1995. This 

amount of suspended sediment is considered as wash load and to have negligible 

effects on n values.

Table 9. Flow data and computed roughness coefficients, Cave Creek below Cave Buttes Dam

Roughness coefficient

Date of flow

01-09-95 

11-02-95

Discharge, in cubic feet per second

197 

165

Subcritical

0.025 

.025

Supercritical

0.017 

.017

Rating

Good 

Good

Table 10. Average-reach properties, Cave Creek below Cave Buttes Dam

Area, in 

Date square feet

Top width, Hydraulic Mean velocity, Froude Total length, 

in feet radius, in feet in feet per second number in feet

Total fall, Water-surface 

in feet slope

Subcritical flow regime (cross-sections 1-4)

01-09-95 46.6 21.4 2.03 4.36 0.53 311 0.94 0.0030

Supercritical flow regime (cross-sections 6-8)

01-09-95 21.9 19.1 1.12 9.21 1.54 148 2.19 .0148

Subcritical flow regime (cross-sections 1-4)

11-02-95 42.0 20.4 1.91 4.06 .51 311 .95 .0031

Supercritical flow regime (cross-sections 6-8)

11-02-95 18.1 17.9 .99 9.16 1.61 148 1.92 .0130

Cave Creek below Cave Buttes Dam 31
Cave Creek below Cave Buttes Dam—Continued

O

I •

LJJ

_l 

LJJ

I——T T——I——T

SECTION 4

10 20 30 40 50 

STATIONING FROM LEFT BANK , IN FEET

Figure 8A Cross-section 4, Cave Creek below Cave Buttes Dam.

60

2' 3" 4' 5' 6' T

Figure 8B. Plan view, Cave Creek below Cave Buttes Dam.

LJJ 

O

LJJ

O 

O

CO 

CO

0.030

0.025

0.020

0.015

0.010

SUBCRITICAL

SUPERCRITICAL 

O O

0.6 0.8 1 1.2 1.4 1.6 1.8 

HYDRAULIC RADIUS, IN FEET

2.2

Figure 8C. Manning's n and hydraulic radius, Cave Creek below Cave Buttes Dam. 

32 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Cave Creek below Cave Buttes Dam—Continued

Figure 8D. View from cross-section 7 looking upstream toward transition from subcritical to 

supercritical flow, Cave Creek below Cave Buttes Dam.

Figure 8E. View from cross-section 4 looking upstream toward subcritical flow reach during 

survey of the water surface, November 2, 1995, Cave Creek below Cave Buttes Dam.

Cave Creek below Cave Buttes Dam 33
Cave Creek below Cave Buttes Dam—Continued

Figure 8F. View from top of reach looking downstream, Cave Creek below Cave Buttes Dam.

"*"

*^- r^jN&£V^r ;^k^"

&

*^-._ .^-->'-«..•"• --^ , •*•£-• v^.>, .":,=! ' , r*-- &;

Figure 8G. View from midchannel looking downstream, Cave Creek below Cave Buttes Dam. 

34 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Hassayampa River near Morristown

Reach location:

Drainage area: 

Bed-material size: 

Channel description;

Latitude 33°53'06", longitude 112039'41". Reach is at streamflow-gaging station 

09516500, Hassayampa River near Morristown.

796 mi2.

J50 = 0.42 mm (0.0014 ft).

The channel bed in the reach consists of sand-sized material, and the channel is 

straight and uniform. The right bank is a straight vertical railway embankment, and 

the left bank is a vertical bedrock cliff. The sparse vegetation is mainly mesquite 

along the right bank. The stream is intermittent, and flow is unregulated.

Remarks: Data from current-meter measurements were used to obtain an accurate

representation of the bed configuration. This technique was required because the bed 

is highly unstable and may take on different configurations during moderate to high 

flows (fig. 9A). Only channel-geometry measurements obtained during flow from 

this one section, therefore, were used for the n-verification computations. The 

measured water-surface slope is assumed to approximate the slope of the energygradient line. Uniformity of the reach probably prevents significant energy losses 

due to expansion and contraction. Potential errors incurred by the required 

assumptions probably are offset by the accurate measurements of the channel 

configuration during flows on this highly unstable bed. Upper-regime flow 

conditions were encountered during all of the verification measurements (fig. 3). 

Plane-bed or nearly plane-bed conditions were reported for the two lower flow 

measurements, and waves that slowly propagated downstream, nearly extended 

bank to bank, and periodically collapsed were observed during the two high-flow 

measurements. Increased suspended-sediment concentrations and turbulance 

generated by the waves probably resulted in the larger verified n values. The 

suspended-sediment concentration was 18,916 mg/L at a flow rate of about 

9,000 ft3/s on March 6, 1995.

Table 11. Flow data and computed roughness coefficients, Hassayampa River near Morristown

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

02-20-93

02-09-93

01-19-93

01-21-93

7,330

6,180

2,470

787

0.025

.026

.019

.018

Estimate

Estimate

Estimate

Estimate

Hassaympa River near Morristown 35
Hassayampa River near Morristown—Continued

Table 12. Data obtained from discharge measurements and field surveys, Hassayampa River near Morristown

[N/A, not applicable]

Date

02-20-93

02-09-93

01-19-93

01-21-93

Area, in 

square feet1

652

518

300

155

Top width, 

in feet1

173

172

165

170

Hydraulic

radius, 

in feet1

3.8

3.4

1.8

.9

Mean

velocity,

in feet per 

second1

11.20

11.93

8.23

5.08

Froude 

number1

1.01

1.13

1.09

.94

Total

length, 

in feet

N/A

N/A

N/A

N/A

Total fall, 

in feet

N/A

N/A

N/A

N/A

Watersurface 

slope

0.0062

.0062

.0050

.0043

Obtained from current-meter measurements.

16

14

LU i 0 LU 12

10

CABLEWAY SECTION

FEBRUARY 9, 1993 

JANUARY 19, 1993

20 40 60 80 100 120 140 160 

STATIONING FROM LEFT BANK, IN FEET

EXPLANATION 

CHANNEL BOTTOM ON INDICATED DATE

180 200 220

JANUARY 19, 1993—2,470 cubic feet 

per second

JANUARY 21, 1993—787 cubic feet 

per second

FEBRUARY 9, 1993—6,180 cubic feet 

per second

FEBRUARY 20, 1993—7,330 cubic feet 

per second

Figure 9A. Cableway cross section, bed geometry for each current-meter measurement, and 

water-surface elevations, Hassayampa River near Morristown.

36 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Hassayampa River near Morristown—Continued

CABLEWAY 

SECTION

Figure 98. Plan view. Hassayampa River near Morristown.

0.028

LU 0.026 

O

LL

O

0.024

0.022

0.020

b

0.018

0.016

i i i i i i i i i i i i i r

PLANE BED

WAVES AND DUNES

i i i i I i i i i I i i i i I i i i

0.5 1 1.5 2 2.5 3 3.5 4 4.5 

HYDRAULIC RADIUS, IN FEET

Figure 9C. Manning's n and hydraulic radius, Hassayampa River near Morristown.

Hassaympa River near Morristown 37
Hassayampa River near Morristown—Continued

100

m 

CD

LU

o

QC 

LU 

CL

ID 

O

0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20 50 100 

PARTICLE SIZE, IN MILLIMETERS

Figure 9D. Particle-size distribution for bed material, Hassayampa River near 

Morristown.

Figure 9£. View upstream from midchannel during no-flow period, Hassayampa River near 

Morristown. Rod indicates water-surface elevation for the peak flow of January 8, 1993.

38 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Hassayampa River near Morristown—Continued

Figure 9F. View from cableway looking upstream during flow of February 9, 1993, 

Hassayampa River near Morristown. Disturbance is a wave propagating slowly downstream 

and is indicative of hydraulic characteristics in alluvial channels during upper-regime flow 

conditions.

Figure 9G. View from cableway looking upstream during flow of February 9, 1993, 

Hassayampa River near Morristown. Disturbance is a wave propagating slowly downstream 

and is indicative of hydraulic characteristics in alluvial channels during upper-regime flow 

conditions. Photograph taken soon after photograph shown in figure 9F.

Hassaympa River near Morristown 39
Indian Bend Wash above Curry Road

Reach location: Latitude 33°26'50", longitude 111°54'55". Reach begins about 1,500 ft upstream

from streamflow-gaging station 09512162, Indian Bend Wash at Curry Road.

Drainage area: 82.0 mi2. 

Bed-material size: See channel description.

Channel description: The constructed channel is uniform and cross sections are trapezoidal in shape. The

channel bottom is firm earth with seasonal growth of grasses and small brush. The 

stream is ephemeral.

Remarks: The grass generally was laid over following the flow on October 6, 1993, and in a

direction parallel to flow, whereas the sparse brush appeared to be little affected by 

the flow. Postflow conditions indicate that the flow of December 26, 1994, did not 

significantly affect either the brush or the grass. Suspended-sediment concentration 

was 365.4 mg/L at a discharge of about 500 ft3/s on September 28, 1995, and was 

considered wash load. As the drainage area is mainly urbanized, this wash-load 

condition probably is indicative of suspended-sediment concentrations for most 

flows at this site (Possum and Davis, 1996).

Table 13. Flow data and computed roughness coefficient, Indian Bend Wash above Curry Road

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

10-06-93 6,480 0.024 Fair

12-26-94 449 .036 Good

Table 14. Average-reach properties, Indian Bend Wash above Curry Road

Date

10-06-93

12-26-94

Area, in 

square feet

905

200

Top width, 

in feet

167

132

Hydraulic 

radius, in feet

5.36

1.52

Mean velocity, 

in feet per second

7.16

2.25

Froude 

number

0.54

.32

Total length, 

in feet

878

851

Total fall, 

in feet

1.27

1.36

Water-surface 

slope

0.0014

.0016

40 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
(Q

C

MANNING'S ROUGHNESS COEFFICIENT (n)

o

I

33 

§a

3 00000005" 

oobbbbbo.

-«. -'•r\3r\300GO.p^-P^TM1 O 010010010012J

f) -1 ————————————————————————————————^03 ->• 

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IT 5 01 •< -<

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D

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-~ - — 

— — — ~

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— — _ r • -

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-"~ i i i ~ ~i i i i 1 i i i i 1 i i i i 1 i i 1 i 1 i i i i 1 i i i r

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o03Q.

(Q

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o3w5" ^ 

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CDQ. 

^

03 CT 

OCDOcID O

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ELEVATION, IN FEET

i i | r—i—i— i -"i—i—i—i—r

3 

Q. 5'3CD (D3 

Q.

I

(A3"

Q) 

CT O(D 

O

I] 

o

Q) Q.

C (D Q.
Indian Bend Wash above Curry Road—Continued

Figure 10D. View from midchannel looking downstream at laid-over grass following flow of 

October 6, 1993, Indian Bend Wash above Curry Road. The square grid (painted orange) has 

an outside dimension of 1.5 feet and an internal grid spacing of 1 inch.

Figure 10E. View from midreach looking upstream following flow of October 6, 1993, Indian 

Bend Wash above Curry Road.

42 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Indian Bend Wash above Curry Road—Continued

Figure 10F. View from bottom of reach looking upstream during low flow, Indian Bend Wash 

above Curry Road.

Figure 10G. View from midchannel looking upstream before flow of December 26, 1994, 

Indian Bend Wash above Curry Road.

Indian Bend Wash above Curry Road 43
Salt River above Interstate 10

Reach location;

Drainage area: 

Bed-material size: 

Channel description;

Remarks:

Latitude 33°25'53", longitude 111°59'16". Reach begins about 3,000 ft above 

Interstate 10.

13,300 mi2.

d50 = 94mm(0.31ft).

The constructed channel has a uniform geometry and cross sections generally are 

rectangular in shape. Bed material is dominated by medium-sized rounded cobbles. 

The river was perennial before construction of upstream reservoirs.

Sparse growth of algae sometimes is observed growing on the cobbles following 

prolonged releases from the upstream reservoirs. Flow appeared to be clear during 

the three discharge measurements. Suspended-sediment data are not available.

Table 15. Flow data and computed roughness coefficients, Salt River above Interstate 10

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

02-1S-92 4,900

01-15-92 2,070

01-09-92 1,000

Table 16. Average-reach properties, Salt River above

Date

02-18-92

01-15-92

01-09-92

Area, in Top width Hydraulic

square feet in feet radius, in feet

1,090 416 2.61

665 405 1.64

462 399 1.16

15

14

13

ELEVATION, IN FEET li 00CO ON>

7

6

K

0.030 Good

.034 Good

.038 Good

Interstate 10

Mean velocity, in Froude Total length, Total fall, Water-surface

feet per second number in feet in feet slope

4.50 0.49 1,497 3.71 0.0025

3.13 .43 1,497 3.99 .0027

2.18 .36 1,497 3.91 .0026

- 1 i i i i i i i i i i i i i i i i i

EE- 1

E- I

i i [ i i i i i i i i i i i i i i i t i i i i i i i i i i i i -

-^

1' ~

FEBRUARY 18, 1992 / ~

~ \ JANUARY 15, 1992 / ~

— \ 1 —

— \> —— •X"*SVSS(^^

5-

~ i 1 i i i 1 i i i 1 i i i 1 i i i 1

JANUARY 9, 1992 / -

^*^J ~

SECTION 1 ~=

i i i I i i i I i i i I i i i I i i ii i i I t i i i i i -

-20 0 40 80 120 160 200 240 280 320 360 400 440 480 

STATIONING FROM LEFT BANK, IN FEET

Figure 11A Cross-section 1, Salt River above Interstate 10. 

44 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Salt River above Interstate 10—Continued

r

Figure 11S. Plan view, Salt River above Interstate 10.

LLJ

o

UJ

O 

O

CO 

CO

X 

CD

Z>

o

cc

CO 

CD

0.045

0.040

0.035

0.030

0.025

i i i I i i i i i i IT i in n TI i i i i i i ri rn r i rr^ i i \\ i i

i i i i i i i I i i i I i i i I i i i I i i i I i i i i i i i I i i i I i i i I i i i

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 

HYDRAULIC RADIUS, IN FEET

Figure 11C. Manning's n and hydraulic radius, Salt River above Interstate 10.

Salt River above Interstate 10 45
Salt River above Interstate 10—Continued

100

80

60

40

20

10 20 50 100 200

PARTICLE SIZE, IN MILLIMETERS

500 1,000

Figure 11D. Particle-size distribution for bed material, Salt River above 

Interstate 10.

Figure 11E. View of typical bed material in channel reach, Salt River above Interstate 10. 

The square grid (painted orange) has an outside dimension of 1.5 feet and an internal grid 

spacing of 1 inch.

46 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Salt River above Interstate 10—Continued

Figure 11F. View from top of reach looking downstream during flow of January 15, 1992, Salt 

River above Interstate 10.

Figure 11G. View from top of reach looking downstream, Salt River above Interstate 10.

Salt River above Interstate 10 47
Verde River below Beeline Highway

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Latitude 33°33'31", longitude 1 ll°40'07". Reach begins about 200 ft downstream 

from streamflow-gaging station 09511300, Verde River near Scottsdale.

6,615 mi2 .

d50 = 11 Omm (0.36 ft).

Although there is a slight curvature of the reach as indicated in the plan view 

(fig. \2B\ the channel is fairly uniform and consists mainly of cobble-sized material. 

The left bank is steep and is primarily bare soil. Root systems of the vegetation at 

higher elevations seem to keep the bank material fairly stable. Sparse vegetation 

(brush) is in the channel. The river is perennial and flow is regulated by upstream 

reservoirs.

The effect of the sparse brush in the main channel on flow resistance was considered 

negligible. Additionally, the bank vegetation evident in figure 12G was above the 

high-water line and did not affect flow. The low-flow verification measurement was 

made in a short section of the channel reach (not shown in figures).

Table 17. Flow data and computed roughness coefficients, Verde River below Beeline Highway

Remarks:

Date of flow

03-28-9 1 

09-14-89

Discharge, in cubic feet per second

2,860

225

Roughness coefficient

0.030 

.036

Rating

Good 

Good

Table 18. Average-reach properties, Verde River below Beeline Highway

Area, in Top width, Hydraulic Mean velocity, in 

Date square feet in feet radius, in feet feet per second

Froude Total length, Total fall, Water-surface 

number in feet in feet slope

03-28-91 

09-14-89

610 

87.9

157

87.4

3.94 

1.00

4.69 

2.57

0.42 

.45

1.045

243

1.38 

.92

0.0013 

.0038

SECTION 2

-4 

-10 0

J__L

20 40 60 80 100 120 

STATIONING FROM LEFT BANK, IN FEET

140 160 170

Figure 12A Cross-section 2, Verde River below Beeline Highway. 

48 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Verde River below Beeline Highway—Continued

Figure 12S. Plan view for flow of March 28, 1991, Verde River below Beeline Highway. The reach in which the lowflow verification measurement was made is between cross-sections 1 and 2.

0.045

0.040

O

cc

CO

0.035

0.030

0.025

0.020 I I I I I I I I I I I I I I I I I

0.5 1 1.5 2 2.5 3 3.5 4 4.5 

HYDRAULIC RADIUS, IN FEET

Figure 12C. Manning's n and hydraulic radius, Verde River below Beeline Highway.

Verde River below Beeline Highway 49
Verde River below Beeline Highway—Continued

LU 

CD

100

80

40

20

o

10 20 50 100 200

PARTICLE SIZE, IN MILLIMETERS

500 1,000

Figure 12D. Particle-size distribution for bed material, Verde River below Beeline 

Highway

Figure 12E. View of typical bed material, Verde River below Beeline Highway. The square 

grid (painted orange) has an outside dimension of 1.5 feet and an internal grid spacing of 

1 inch.

50 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Verde River below Beeline Highway—Continued

f'*f5W* £"*'•" ^^-"- *-'"> - 

fc'^sfe^C^v^^-,^, ^

Figure 12F. View from right bank and midreach looking upstream during flow of 

September 14, 1989, Verde River below Beeline Highway.

Figure 12G. View from cableway looking downstream during flow of March 28, 1991, Verde 

River below Beeline Highway.

Verde River below Beeline Highway 51
West Fork Sycamore Creek near Sunflower

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Remarks:

Latitude 33°57'20", longitude 111°29'25". Reach begins about 350 ft downstream 

from streamflow-gaging station 09510120, West Fork Sycamore Creek near 

Sunflower (Aldridge and Garrett, 1973).

8.6 mi2 .

See channel description.

The channel is fairly uniform throughout the study reach. The channel bottom 

consists mostly of pebble to boulder-size clasts. No grain-size analysis is available. 

A few trees are near the channel margins (figs. 13C-£). The stream is intermittent, 

and flow is unregulated.

The trees probably had a slight effect on total flow resistance. Discharge was 

obtained from a well-defined stage-discharge relation. High-water indicators were 

plentiful and were rated good to excellent (E.E. Denis, hydrologist, U.S. Geological 

Survey, written commun., 1963).

Table 19. Flow data and computed roughness coefficient, West Fork Sycamore Creek near Sunflower

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

02-11-63 117 0.067 Good

Table 20. Average-reach properties, West Fork Sycamore Creek near Sunflower

Area, in Top width, Hydraulic Mean velocity, in Froude Total length, Total fall, Water-surface 

Date square feet in feet radius, in feet feet per second number in feet in feet slope

02-11-63 36.2 29.4 1.21 3.29 0.53 108 1.96 0.0181

16

15

SJ 14

O

13

12

11

2'

SECTION 2 —

10 -5

i i i i I i i i i I i i i i I i i i i I j i i i I i i i i I i i i i I i i i i I i i i i I i i \ t

0 5 10 15 20 25 30 35 40 45

STATIONING FROM LEFT BANK, IN FEET 

Figure 13A Cross-section 2, West Fork Sycamore Creek near Sunflower.

52 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
West Fork Sycamore Creek near Sunflower—Continued

Figure 13B. Plan view, West Fork Sycamore Creek near Sunflower.

Figure 13C. View from bottom of reach looking 

upstream toward cross-section 2, February 25, 1963, 

West Fork Sycamore Creek near Sunflower.

West Fork Sycamore Creek near Sunflower 53
West Fork Sycamore Creek near Sunflower—Continued

Figure 13D View from midreach looking upstream 

toward right bank of cross-section 1, February 25, 1963, 

West Fork Sycamore Creek near Sunflower.

Figure 13E. View from bottom of reach looking 

upstream toward cross-section 3, February 25, 1963, 

West Fork Sycamore Creek near Sunflower.

54 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
San Pedro River near Charleston

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Remarks:

Latitude 31°37'33", longitude 110°10'26". Reach is just downstream from 

streamflow-gaging station 09471000, San Pedro River near Charleston (Aldridge 

and Garrett, 1973).

1,234 mi2.

See channel description.

The bed material is mainly hard conglomerate overlain by deposits that range from 

sand to angular and rounded boulders 2 to 3 ft (610 to 920 mm) in diameter. The 

material surrounding the boulders has a median grain size of 1.2 mm (fig. 14Q. At 

the upper end of the reach, conglomerate projections are exposed across the entire 

channel. The projections are several feet across, and many stand 2 to 3 ft (610 to 920 

mm) above the average bed level. Grass and small brush grow along bars at the 

channel sides. The stream is perennial, and flow is unregulated.

Two other channel reaches also were used to verify roughness coefficients for this 

same discharge measurement. These reaches were in sections of the stream where 

the bed was primarily composed of sand-sized material and was considered highly 

unstable. Owing to the uncertainty of channel geometry during peak flow (D.E. 

Click, hydrologist, U.S. Geological Survey, written commun., 1964), these reaches 

were not included in this report.

Table 21. Flow data and computed roughness coefficient, San Pedro River near Charleston

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

08-14-64 7,550 0.048 Fair

Table 22. Average-reach properties, San Pedro River near Charleston

Area, in Top width, Hydraulic Mean velocity, in Froude Total length, Total fall, Water-surface 

Date square feet in feet radius, in feet feet per second number in feet in feet slope

08-14-64 1,268 276 4.62 5.9 0.44 293 1.42 0.0048

San Pedro River near Charleston 55
San Pedro River near Charleston—Continued

34

32

30

I- 28

LLJ

^ 26

z 

- 24

I 22

QJ 20 

^ 18

16

14

12 

-10 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280

STATIONING FROM LEFT BANK, IN FEET 

Figure 14A Cross-section 2, San Pedro River near Charleston.

SECTION 2

i___i i i

Figure 14S. Plan view, San Pedro River near Charleston. 

56 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
San Pedro River near Charleston—Continued

LU

o

LU 

O

cc

LU 

0.

o

100

80

60

40

20

0

0.01 0.02 0.05 0.1 0.2 0.5 1 2 5 10 20 50 100 

PARTICLE SIZE, IN MILLIMETERS

Figure 14C. Particle-size distribution for bed material, San Pedro River near 

Charleston.

Figure 14D. View from left bank looking downstream toward right 

bank of cross-section 1, October 8, 1964, San Pedro River near 

Charleston.

San Pedro River near Charleston 57
San Pedro River near Charleston—Continued

Figure 14E. View from left bank of cross-section 2 looking 

downstream, October 8, 1964, San Pedro River near Charleston.

58 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Santa Cruz River at Cortaro

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Remarks:

Latitude 32°21'04", longitude 111°05'38". Reach begins about 1,200 ft downstream 

from streamflow-gaging station 09486500, Santa Cruz River at Cortaro (Aldridge 

andGarrett, 1973, p. 48).

3,503 mi2.

d50 = 1.2 mm (0.0039 ft).

The channel is fairly straight and uniform and has steeply sloping dirt banks. Heavy 

brush covers the banks. The cross sections are trapezoidal in shape. The bed is 

composed mainly of sand-sized material. The river is ephemeral, and flow is 

unregulated.

A current-meter measurement was made at the time of peak discharge. Upper-flow 

regime conditions persisted during the discharge measurement (fig. 3). High-water 

marks surveyed after flow were rated good to excellent. JJ. Ligner (hydrologist, 

U.S. Geological Survey, written commun., 1964) made the following observations 

during flow on September 10, 1964.

"The river carried a great deal of drift of all sizes, ranging from seeds 

and twigs to large desert-type trees. As we watched, we were able to see the 

material that forms the normal high water mark as it advanced up the river 

bank. It was interesting to note that the grass and small shrubs acted as a fine 

sieve, and that there was clear water usually from 3 to 6 in. (laterally) ahead of 

the drift line. It appeared to us that the very top of the drift pile was a close 

approximation of the ultimate elevation of the water surface. During most of the 

time we observed the flow, there were chains of standing waves building and 

breaking into antidunes. There were a number of times that I observed rather 

long waves that were formed parallel to the flow of the river and that would 

break (almost like an antidune) towards the right bank."

Table 23. Flow data and computed roughness coefficient, Santa Cruz River at Cortaro

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

09-10-64 14,200 0.020 Fair

Table 24. Average-reach properties, Santa Cruz River at Cortaro

Area, in Top width, Hydraulic Mean velocity, in Froude Total length, Total fall, Water-surface 

Date square feet in feet radius, in feet feet per second number in feet in feet slope

09-10-64 1,137 175 6.36 12.5 0.87 860 3.16 0.0037

Santa Cruz River at Cortaro 59
Santa Cruz River at Cortaro—Continued

105

100

95

90

85

SECTION 2

i I i

40 60 80 100 120 140 160 180 200 220 240 260 

STATIONING FROM LEFT BANK, IN FEET

Figure 15A Cross-section 2, Santa Cruz River at Cortaro.

Figure 1 5B. Plan view, Santa Cruz River at Cortaro. 

60 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Santa Cruz River at Cortaro—Continued

100

80

60

40

20

0

0.01 0.02 0.05 0.1 0.2 0.5 1 2 

PARTICLE SIZE, IN MILLIMETERS

10

Figure 15C. Particle-size distribution for bed material, Santa Cruz River at 

Cortaro.

Figure 15D. View from cableway looking downstream, 

August 5, 1954, at a discharge of 7,000 cubic feet per 

second, Santa Cruz River at Cortaro.

Santa Cruz River at Cortaro 61
Santa Cruz River at Cortaro—Continued

*VY?* '•:&'

Figure 15E. View from cableway looking downstream, 

October 2, 1964, Santa Cruz River at Cortaro.

Figure 15F. View from midchannel looking upstream 

toward right bank of cross-section 1 after flow of 

September 10, 1964, Santa Cruz River at Cortaro.

62 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Verde River near Paulden

Reach location:

Drainage area: 

Bed-material size: 

Channel description:

Remarks:

Latitude 34°53'40", longitude 112°20'32". Reach begins about 80 ft below 

streamflow-gaging station 09503700, Verde River near Paulden (Aldridge and 

Garrett, 1973).

2,530 mi2.

See channel description.

The low-flow channel is 40 to 50 ft wide and has irregular, vertical banks about 2 ft 

high. The bed of the low-flow channel is composed of compacted sand, cobbles, and 

scattered boulders as much as 2 ft (610 mm) in diameter. Above this channel are 

grass-covered benches. The right bench is narrow and bare except for a growth of 

very short grass; the bank slopes steeply above the bench. The slope of the left bank 

is gentle. The reach expands slightly throughout its length. The river is perennial, 

and flow is unregulated.

H.W. Hjalmarson (hydrologist, U.S. Geological Survey, written commun., 1965) 

stated:

"The computed n value seems lower than would be indicated by the 

size of the bed material, but most of the rocks were immersed in a smooth flow 

of water and caused very little turbulence. The top of the surge was marked 

throughout the reach before and after the current-meter measurement."

Table 25. Flow data and computed roughness coefficient, Verde River near Paulden

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

04-16-65 313 0.029 Fair

Table 26. Average-reach properties, Verde River near Paulden

Date

Area, in Top width, Hydraulic Mean velocity, in Froude Total length, 

square feet in feet radius, in feet feet per second number in feet

Total fall, Water-surface 

in feet slope

04-16-65 139 68.3 2.19 2.19 0.27 333 0.26 0.0008

Verde River near Paulden 63
Verde Valley near Paulden—Continued

4.5

4

3.5 - 2

LJJ

LJ 2

1.5

\ ———— T

SECTION 2

I —— I

i i i i i I i t I i n - H -. .1.

10 20 30 40 50

STATIONING FROM LEFT BANK, IN FEET

Figure 16A Cross-section 2, Verde River near Paulden.

60 70

3'

Figure 16S. Plan view, Verde River near Paulden. 

64 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Verde River near Paulden—Continued

Figure 16C. View from top of reach looking downstream during 

low flow, Verde River near Paulden.

Figure 16D. View from top of reach looking downstream at time of 

verification measurement, April 16, 1965, Verde River near 

Paulden.

Verde River near Paulden 65
Salt River below Stewart Mountain Dam

Reach location: Latitude 33°33'00". longitude lH 0 34'3r 1 . The reach begins about 2.25 mi

downstream from streamflow-gaging station 09502000, Salt River below Stewart 

Mountain Dam (Barnes, 1967).

Drainage area: 6,230 mi2 . 

Bed-material size: See channel description.

Channel description: The reach is fairly uniform and slightly contracting in a downstream direction. Bed

and bank material consist of smooth cobbles that range from 4 to 10 in. (100 to 250 

mm) in diameter. As indicated in the photographs, a sand-and-pebble matrix is 

between the cobbles. A grain-size analysis was not available. The river is perennial, 

and flow is regulated by upstream reservoirs.

Table 27. Flow data and computed roughness coefficient, Salt River below Stewart Mountain Dam

Date of flow Discharge, in cubic feet per second Roughness coefficient Rating

03-24-50 1,280 0.032 Good

Table 28. Average-reach properties, Salt River below Stewart Mountain Dam

Area, in Top width, Hydraulic Mean velocity, in Froude Total length, Total fall, Water-surface 

Date square feet in feet radius, in feet feet per second number in feet in feet slope

03-24-50 405 190 2~l4322O391,886 159 0.0019

66 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Salt River below Stewart Mountain Dam—Continued

103

102

101

100

2 99

Z QR 

O

< 97

LJJ

DJ 96 

95 

94 

93

LJJ

SECTION 2

0 20 40 60 80 100 120 140 160 

STATIONING FROM LEFT BANK, IN FEET

Figure 17A Cross-section 2, Salt River below Stewart Mountain Dam.

180 200 220

7'

Figure 17B. Plan view, Salt River below Stewart Mountain Dam.

Salt River below Stewart Mountain Dam 67
Salt River below Stewart Mountain Dam—Continued

Figure 17C. View looking upstream along left bank below 

cross-section 6, Salt River below Stewart Mountain Dam.

Figure 17D. View looking downstream along left bank from 

cross-section 2, Salt River below Stewart Mountain Dam.

68 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
DISCUSSION OF SIGNIFICANT RESULTS

Components of Manning's n

Attempts were made, using various techniques, 

to quantify the separate components or adjustment 

factors of Manning's n for each of the verification 

measurements presented in this report (table 29). The 

purpose of presenting this information is to supply 

additional aid to designers and engineers who need to 

assess roughness characteristics of stream channels for 

hydraulic studies in arid to semiarid environments. 

According to current guidelines (Thomsen and 

Hjalmarson, 1991), the general approach for estimating 

resistance to flow in stream channels is to first select a 

base value of Manning's n for the bed material. The 

base value of Manning's n is represented by the size 

and shape of the grains of the material that form the 

wetted perimeter and that produce a retarding effect on 

flow (Chow, 1959). Cross-section irregularities, 

channel alignment, vegetation, obstructions, and other 

factors that increase roughness then are added to the 

base value of n. The following equation, first 

introduced by Cowan (1956), is used to compute the 

equivalent total Manning's n for a channel using this 

approach:

n =

where

nb =

n2 =

m =

base value of n for a straight uniform

channel,

surface irregularities,

variations in shape and size of the

channel,

obstructions,

vegetation, and

correction factor for meandering or

sinuosity of the channel.

Detailed explanations for each adjustment factor can 

be found in Cowan (1956), Chow (1959), Aldridge and 

Garrett (1973), and Thomsen and Hjalmarson (1991).

Base Value of Manning's n for Gravel-Bed 

Streams

A variety of techniques and methods have been 

presented in literature that aid in estimating the base 

value of Manning's n for hydraulic computations in 

gravel-bed streams. Referencing tables and photographs of verified roughness coefficients is one 

method; another is the use of equations that relate 

Manning's n to easily measured hydraulic and channel 

parameters.

Previous investigators have presented data that 

indicate trends exist among hydraulic radius, median 

grain-size diameter, and verified base values of n for 

gravel-bed streams in specific regions of the world. For 

example, Limerinos (1970) examined verified values 

of n for 11 gravel-bed streams in California. Other 

researchers, such as Bray (1979) and Griffiths (1981), 

presented similar information for gravel-bed streams in 

Canada and New Zealand, respectively (table 30). 

These three investigators developed equations that 

relate Manning's n to hydraulic radius and mediangrain size of the bed material (table 30). A similar 

equation was developed for gravel-bed streams in 

Arizona in which the base n value was the only factor 

that contributed to total roughness (table 30; Phillips 

and Ingersoll, 1997).

The four equations are plotted to show the 

relation between Manning's n and relative roughness 

(R/d5Q) for gravel-bed streams in different parts of the 

world (fig. 18). In order to perform this simple 

comparison of equations, a constant d5Q value of 0.30 

ft was used, and hydraulic-radius values ranged from 

0.6 to 7.5 ft (fig. 18).

The plots in figure 18 have a similar trend that is 

fairly steep for relative roughness values less than 

about 5. Although the general trend among the different 

relations is similar and, for relative roughness values 

larger than about 5, all the trend lines asymptotically 

approach constant values, a significant shift is apparent 

in the relation for verified n values presented in this 

report (fig. 18). As indicated by the three equations 

developed for areas outside Arizona, the asymptotic n 

values range between approximately 0.036 and 0.041. 

According to the data presented for dryland gravel-bed 

streams in Arizona, however, the data trend 

asymptotically approaches a base n value of about 

0.028. If the equations presented are to be properly 

used as aids in determining base values of Manning's 

n, adequate descriptions of channel characteristics 

from which the data were obtained must be presented.

Discussion of Significant Results 69
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70 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
Table 29. Summary of verification measurements that include magnitude of base n values, factors required to adequately 

hydraulic components, and an estimated percentage of flow that was blocked by vegetation—Continued

CO (5*

3_

o'

D> 

DO

i

»

Discharge, in cubic 

Date feet per second n "b "1 "2 "3 /74 177 R 

Hassayampa River near Morristown

02-09-93 

01-19-93 

01-21-93

6,180

2,470 

787

0.026 

.019 

.018

0.023 

.016 

.015

—

'0.003 

'.003 

'.003

1.0 

1.0 

1.0

3.4 

1.8 

.9

0

Indian Bend Wash above Curry Road

10-06-93 

12-26-94

02-18-92 

01-15-92 

01-09-92

6,480 

449

4,900 

2,070 

1,000

.024 

.036

.030 

.034 

.038

.021 

.025

.030 

.034 

.038

::: : :

Salt River above Interstate

...

'.003 

'.Oil

10

...

1.0 

1.0

1.0 

1.0 

1.0

5.36

1.52

2.61 

1.64 

1.16

Verde River below Beeline Highway

03-28-91 

09-14-89

2,860

225

.030 

.036

.030 

.036 — —

1.0 

1.0

3.94 

1.00

West Fork Sycamore Creek near Sunflower

02-11-63 117 .067 .064 ...

'.003 1.0 1.21 

San Pedro River near Charleston

08-14-64 7,550 .048 .039 0.006 '.003 1.0 4.62 

Santa Cruz River at Cortaro

09-10-64 14,200 .020 .017 ...

'.003 1.0 6.36 

Verde River near Paulden

04-16-65 313 .029 .025 .001 '.003 1.0 2.19 

Salt River below Stewart Mountain Dam

03-24-50 1,280 .032 .032 — — 1.0 2.14 

'Obtained from equation 14. 

"Obtained from equation 13.
Table 30. Equations for relations among base n values, hydraulic radius, and median diameter of bed material for gravel-bed 

streams in different parts of the world

[Equations 10-12 are from Coon (1995)]

Source

Limerinos (1970)

Griffiths (1981)

Equation Range in o*50 (ft) Location

(10)

1/fi 0.02 to 0.83 California, U.S.A. 

0.09267?

0.35 + 2.01og(7?A/50 )

(11)

, /fi 0.04 to 0.99 New Zealand 

0.09277?

77 0.760 + 1.981og (7?A/50)

Bray(1979)

(12)

0.09277?

0.248 + 2.361og (/?/</50 )

0.06 to 0.48 Alberta, Canada

n verification

(13)

0.0926/?

1.46+ 2.23log

0.28 to 0.36 Arizona, U.S.A.

'Phillips and Ingersoll (1997).

0.080

0.020

10 15

RELATIVE ROUGHNESS, R/d50

Figure 18. Relation of Manning's n and relative roughness for gravel-bed stream channels in Arizona 

and throughout the world. All trend lines are plotted for values of d5Q equal to 0.30 foot, and values of 

R range from 0.6 to 7.5 feet.

72 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
A discussion, therefore, follows that presents potential 

factors that may account for the differences between 

the relations (fig. 18).

Possible explanations for the apparent shift in 

relations may be found by examining differences in 

channel and flow characteristics for the separate 

regions in which the data for the equations were 

obtained. For example, most of the streams used in the 

derivation of equations 10, 11, and 12 (table 30) for 

California, New Zealand, and Canada, respectively, are 

perennial and in relatively humid climates; whereas 

many of the streams that were studied in Arizona are 

ephemeral and in an arid to semiarid climate. Channels 

of ephemeral streams in dry climates, such as Skunk 

Creek above Interstate 17, may contain substantial 

amounts of fine-grained particles between the larger 

cobble-sized particles primarily because of the lack of 

regular base-flow conditions required for sediment 

transport. The presence of a fine-grained matrix may 

result in mitigated turbulence around the cobbles. The 

overall hydraulic effect would be a lower expenditure 

of energy by the fluid during flow resulting in lower 

values of nb .

The substantial shift in trendlines also may 

reflect extraneous flow-retarding effects associated 

with irregularities in bank shape and changes in 

channel alignment. Many of the sites used to develop 

equations 10, 11, and 12 are located in relatively 

pristine areas where streams are not substantially 

affected by human influences. Three of the sites used 

to derive equation 13, however, are located in river 

reaches that have been channelized. In addition to 

stabilizing channel banks, channelization projects 

generally tend to increase conveyance by straightening 

rivers, potentially resulting in a decrease of flowretarding effects associated with channel meanders and 

other irregularities (Phillips and Ingersoll, 1997).

A third possible reason for the lower values of nb 

for gravel-bed streams in Arizona may be the result of 

the location of the selected sites with respect to the 

stream's headwaters. Many of the selected sites in 

Arizona are at great distances from the stream's source, 

where the stream is considered base level. Particles in 

base-level streams generally are rounder and reflect 

better sorting and homogeneity than higher-gradient 

piedmont channels (Leopold and others, 1964). For 

piedmont streams where homogeneity of particles may 

be relatively low, the particles that are substantially 

larger than the median size can play an important role 

in flow resistance (Leopold and others, 1964). For

similar values of J50, therefore, greater turbulence may 

occur near channel beds of piedmont streams than near 

channel beds of base-level streams resulting in larger 

values of nb. Several of the ^-verification measurements used for calibration of equations 10, 11, and 12 

(table 30) were made in piedmont streams. 

Additionally, the range in median diameter of particles 

for streams in central Arizona is much narrower than 

the range used to develop equations for gravel-bed 

streams in other regions of the world (table 30). The 

sites with relatively large median grain sizes that were 

employed in the development of equations 10, 11, and 

12 may have had a disproportionate effect on 

roughness, a consequence that may weight the relations 

toward higher values of n (fig. 18; Phillips and 

Ingersoll, 1997).

A final explanation for the apparent shift in 

relations may be found by examining potential 

extraneous flow-retarding elements in the streams that 

were used in the derivation of each equation. Although 

the previous investigators attempted to incorporate 

gravel-bed stream sites in which nb was the only flowretarding factor, examination of several sites indicates 

that the flow-retarding effects associated with bank 

vegetation may have contributed to the overall value of 

n. As discussed previously, Manning's n generally 

decreases with depth until a constant value is 

asymptotically reached. For channels that contain an 

appreciable amount of bank vegetation, however, the 

inverse is likely, and n can increase substantially with 

flow depth (Barnes, 1967; Jarrett, 1985; and Coon, 

1995). One of the sites used by Limerinos (1970), for 

example, is the Merced River at Happy Isles Bridge, 

near Yosemite, California. According to sitedescription information and visual examination of the 

major flow-retarding elements for this site (Barnes, 

1967, p. 194-197), an extensive amount of vegetation 

in the form of trees was present along the channel 

banks, which may have had an influence on computed 

n values (Limerinos, 1970, table 1). Additionally, in the 

derivation of the equation for gravel-bed streams in 

New Zealand (table 30, equation 11), Griffiths (1981) 

used several streams that also contain bank vegetation 

that may have influenced the overall computed 

roughness coefficient (Hicks and Mason, 1991). If the 

flow retarding effect of bank vegetation contributed to 

total flow retardance at a substantial number of sites 

used to derive the respective equations, the result could 

be an apparent upward shift for the relation between n 

and relative roughness (fig. 18). The contribution of

Discussion of Significant Results 73
bank vegetation to total flow retardance for sites used 

to develop equation 13 appeared to be negligible.

Whatever the reason for the difference between 

the separate equations, it seems that the relations 

presented generally are subject to the hydraulic, 

hydrologic, and geologic conditions of the respective 

research areas. Because the established equations are 

limited to the range in hydraulic and channel 

components used in their derivation, application of 

equation 13 to similar gravel-bed dryland streams also 

is limited to this same range. For example, when 

transferring results to similarly characterized dryland 

stream channels, caution must be used for sites where 

values of hydraulic radius are above about 4 ft (fig. 18), 

and values of d$Q are outside the range of the data set 

(table 29). Further research is required to extend the 

relation developed for gravel-bed streams in Arizona 

to larger magnitude flows that occur less frequently.

Influence of Vegetation on Manning's n

For 19 of the 37 n-verification measurements 

made in dryland streams, vegetation was determined to 

have contributed to total roughness and, therefore, 

required quantifying (table 29). The vegetation 

component for several of the gravel-bed streams that 

contained an appreciable amount of vegetation was 

determined indirectly. Using equation 13, base n values 

were computed for five verification measurements 

made at Skunk Creek above Interstate 17 and two 

verification measurements made at Cave Creek above 

Deer Valley Road (table 29). Because HI through n3 

were considered to have no effect on total roughness at 

these two study reaches, the corresponding effect of 

vegetation on total roughness was quantified for each 

measurement by subtracting the computed base n value 

from total verified n (table 29).

For each of the seven ^-verification measurements, the average percent area of flow blocked by 

vegetation was estimated. The vegetation component 

data obtained indirectly using equation 13 and the 

corresponding percent area of flow blocked by 

vegetation were used to develop a simple best-fit 

relation that can be used to estimate n4 in similarly 

vegetated stream channels (equation 14 and figure 19).

where

B =

vegetation component of Manning's n, and 

percentage of flow blocked by vegetation.

n A = 0.0008 B- 0.0007 (14)

Equation 14 was used to estimate n^ for the 

twelve other ^-verification measurements that contained an appreciable amount of vegetation (table 29). 

For 3 of the 12 measurements, an estimate of n2 was 

required to adequately account for variations in 

channel shape and size (table 29). The estimates of /z2 

primarily were made using standard guidelines for 

assigning components of n to dryland streams 

(Aldridge and Garrett, 1973; Thomsen and Hjalmarson, 1991).

SUMMARY AND CONCLUSIONS

Thirty-seven roughness coefficients were 

determined for 14 selected natural and constructed 

stream channels in Arizona. The sites were selected to 

represent a wide range of channel conditions that 

include alluvial, boulder, and constructed channels that 

contain varying amounts of riparian vegetation. 

Computed roughness-coefficient values ranged from 

0.017 for constructed channels to 0.067 for boulder 

channels.

This report is intended to be used in conjunction 

with current guidelines that describe techniques and 

methods for assigning Manning's n. The descriptions of 

hydraulic and physical characteristics and photographs 

that reflect the major flow-retarding elements in 

channel reaches for which n values have been verified 

can be used as comparison standards to aid in assigning 

n values to similarly characterized channels.

Relations derived from the data in this study 

relate Manning's n values to various hydraulic and 

channel components. For gravel-bed channels that 

have a median bed-material size from 0.28 to 0.36 ft, 

the median diameter of bed material, hydraulic radius, 

and the verified n values are used to develop an 

equation that can be used to determine nb for similarly 

characterized dryland streams. This equation indicates 

substantially lower n values compared to similarly 

developed equations for gravel-bed channels in other 

regions of the world. The larger verified base values of 

Manning's n for gravel-bed channels in California, 

New Zealand, and Canada may be the result of the 

flow-retarding effects associated with channel

74 Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona
LU 

Z 

O 

Qo

O 

O

UJ 

O 

UJ

0.020

0.018

0.016

0.014

0.012

0.010

0.008

0.006

0.004

0.002

0

VEGETATION COMPONENTS

FOR ARIZONA STREAMS

5 10 15 20 25 

PERCENTAGE OF FLOW BLOCKED BY VEGETATION, B

30

Figure 19. Relation of vegetation components for vegetated channels studied and the estimated 

percentage of flow blocked by vegetation (average vegetation conditions for all cross sections at each 

site).

irregularities, poorly sorted bed material, or bank 

vegetation.

The equation developed for base n values in 

gravel-bed streams also is used to quantify the 

magnitude of the vegetation component of Manning's n 

value for several gravel-bed channels where vegetation 

was present. A simple relation was developed for the 

estimated percent area of flow blocked by vegetation 

and the vegetation component. This relation can be 

used at similar sites in the arid to semiarid 

southwestern United States for which the effect of 

vegetation on total roughness must be determined. 

Further study is needed to extend the relations 

developed for this study beyond current limitations of 

the data sets presented in this report.

SELECTED REFERENCES

Aldridge, B.N., and Eychaner, J.H., 1984, Floods of October 

1977 in southern Arizona and March 1978 in central 

Arizona: U.S. Geological Survey Water-Supply Paper 

2223, 143 p.

Aldridge, B.N., and Garrett, J.M., 1973, Roughness coefficients for stream channels in Arizona: U.S. Geological 

Survey unnumbered open-file report, 87 p.

Arcement, G.J., and Schneider, V.R., 1989, Guide for selecting Manning's roughness coefficient for natural channels and flood plains: U.S. Geological Survey WaterSupply Paper 2339, 38 p.

Barnes, H.H., Jr., 1967, Roughness characteristics of natural 

channels: U.S. Geological Survey Water-Supply Paper 

1849, 213 p.

Benson, M.A., and Dalrymple, Tate, 1967, General field and 

office procedures for indirect discharge measurements: 

U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. Al, 30 p.

Birkeland, P.W, 1984, Soils and geomorphology: New York, 

Oxford University Press, 365 p.

Blodgett, J.C., 1986, Rock riprap design for protection 

of stream channels near highway structures: U.S. 

Geological Survey Water-Resources Investigations 

Report 86^127, 60 p.

Bray, D.I., 1979, Estimating average velocity in gravel-bed 

rivers: American Society of Civil Engineers, 

Journal of the Hydraulics Division, v. 105, no. HY9, 

p. 1103-1122.

Burkham, D.E., 1970, Precipitation, streamflow, and major 

floods at selected sites in the Gila River drainage basin 

above Coolidge Dam, Arizona: U.S. Geological Survey 

Professional Paper 655-C, p. C1-C13.

————1976, Hydraulic effects of changes in bottom-land 

vegetation on three major floods, Gila River in southeastern Arizona: U.S. Geological Survey Professional 

Paper 655-J, p. 14.

Selected References 75
Chow, V.T., 1959, Open-channel hydraulics: New York, 

McGraw-Hill, 680 p.

Coon, W.F., 1995, Estimates of roughness coefficients for 

selected natural stream channels with vegetated banks 

in New York: U.S. Geological Survey Open-File Report 

93-161, 127 p.

Costa, J.E., 1987, Hydraulics and basin morphology of the 

largest flash floods in the conterminous United States: 

Journal of Hydrology, v. 93, p. 313-338.

Cowan, W.L., 1956, Estimating hydraulic roughness 

coefficients: Agricultural Engineering, v. 37, no. 7, 

p. 473-475.

Culbertson, J.K., and Dawdy, D.R., 1964, A study of fluvial 

characteristics and hydraulic variables middle Rio 

Grande, New Mexico: U.S. Geological Survey WaterSupply Paper 1498-F, 74 p.

Dalrymple, Tate, and Benson, M.A., 1967, Measurement of 

peak discharge by slope-area method: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 3, chap. A2, 12 p.

Possum, K.D., and Davis, K.G., 1996, Physical, chemical, 

biological, and toxicity data from the study of urban 

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U.S. GOVERNMENT PRINTING OFFICE: 1998-647-628 Selected References 77
Selected Series of U.S. Geological Survey Publications

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ISBN D-b07-flflfl75-X

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