Stream Gaging 

Control Structure for the 

Rio Grande Conveyance 

Channel Near Bernardo 

New Mexico

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1369-E
tream Gaging

ontrol Structure for the 

lio Grande Conveyance 

Channel Near Bernardo 

Mexico

?;- D. D. HARRIS and E. V. RICHARDSON

? IVER HYDRAULICS

EOLOGICAL SURVEY WATER-SUPPLY PAPER 1369-E

Design of a control structure

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

The U.S. Geological Survey Library has cataloged this publication as follows :

Harris, David Dell, 1925-

Stream gaging control structure for the Rio Grande conveyance channel near Bernardo, New Mexico, by D. D. Harris 

and E. V. Richardson. Washington, U.S. Govt. Print. Off., 

1964.

iv, 123-154 p. illus., maps, diagrs., profiles, tables. 24 cm. (U.S. 

Geological Survey. Water-Supply Paper 1369-E) 

River hydraulics. 

Bibliography: p. 154.

1. Stream measurements New Mexico Rio Grande. 2. Hydraulicengineering. I. Richardson, Everett V. 1924- joint author. II.

Title. (Series)

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402
CONTENTS

Page

Abstract________________________________________________________ 123

Introduction ______________________________________________________ 123

Proposed control structure..._______________________________________ 131

Recommended control-structure design___________________________ 131

Recommended control-structure position _________________________ 134

Discharge measurements on the control structure.______-_-_-_-____ 138

Sediment sampling from the control structure _________ ____________ 139

Suggestions for construction and operation________________________ 140

Experimental procedure and equipment- __________________-----_---__ 141

Flumes.._ ____________________________--______-__-_------_--__ 141

Sediment-_-___--_____----------------_---------_------------- 142

Weir models__________________________-__-_---_-_--__-_-----__ 142

Model scales._________________________________________________ 142

Experimental results and discussions_________________________________ 143

Weir A.__._.________________________-___--___---_---_---_--__ 143

Weir B.._.___________________________________________________ 143

Weirs C, D, E, and F__._______________________________________ 143

Weir G._._-..______.__.__.-._________---------------------_-. 145

Weir H...._..__.____________.._.___-___.___-___.-.--_____--._ 145

WeirI_-______________ ________-__--_ -- __ -- 147

Weir J____________________________________ _- _ -___ 147

Weir K__________________- ____--_____ -___ --- _---_--_ 148

Baffle study______________________________-___-__-__-_-_-_------- 149

Energy dissipator study._________-___--_-_-___---___-_-_-------__-- 152

Literature cited______________-__-_______----_-_-___-____-_---__--- 154

ILLUSTRATIONS

Page 

FIGURE 29. Duration curve of daily flow, Rio Grande conveyance channel

near Bernardo_____________________________________ 124

30. Map of Bernardo area_-_______-_______________________- 125

31. Rio Grande conveyance channel, near Bernardo, with a flow

of 700.._-________________________________-___._ 126

32. Rio Grande conveyance channel, near Bernardo, without

flow-.______________________________________________ 127

33. Relation of width and depth to discharge on the Rio Grande

conveyance channel near Bernardo ___________________ 127

34. Relation of velocity to discharge on the Rio Grande conveyance channel near Bernardo_-_________________________ 128

35. Variation in water-surface elevation, bed elevation, and discharge during 1957_________________________________ 128
IV CONTENTS

FIGURE 36. Variation in water-surface elevation, bed elevation, and

discharge during 1958-__-_---_----___---_-_-_-______- 129

37. Details of proposed control structure.____________________ 132

38. Accessories of proposed control structure.________________ 133

39. Stage-discharge relation for control K____________________ 134

40. Water-surface profiles for control K__-_-___--__-__--_____ 135

41. Stage-discharge relations for maximum and average tail-water

levels._________-______-_____--_____--_____--_____ 135

42. Submergence curves for control K_______________________ 136

43-44. Comparison of free fall average submergence and maximum

submergence ratings______--___-_-___-_-_____-_-_____ 137

45-46. Vertical-velocity curves, 9 feet upstream from the crest____ 138

47. Design of model weirs A, B, C, D, E, and F______________ 144

48. Stage-discharge relations for controls C, D, and E_________ 145

49. Design of model weirs G, H, I, and J____________________ 146

50. Stage-discharge relations for controls H, I, and J.._________ 147

51. Comparison of stage-discharge relations for basic controls H

and J______________________________________________ 148

52. Comparison of stage-discharge relations for controls J and K_ 149

53. Baffle model study-_____________________________ 150

54. Energy dissipator study_-____________-_________________ 153

TABLES

Page 

TABLE 1. Observations of the gage height and mean sea level elevations

of the water surface at the present and auxiliary gage..____ 129 

2. Tail-water depths above low bed elevation.________________ 152
WRIVER HYDRAULICS

STREAM GAGING CONTROL STRUCTURE FOR THE

RIO GRANDE CONVEYANCE CHANNEL NEAR

BERNARDO, NEW MEXICO

By D. D. HARRIS and E. V. RICHARDSON

ABSTRACT

A stream gaging control structure to stabilize and increase the sensitivity of 

the stage-discharge relation of the Rio Grande conveyance channel near Bernardo, 

N. Mex., was designed on the basis of model studies and observed field conditions. 

The structure is designed to eliminate the effect of changes in bed configuration 

and bed elevation on the stage-discharge relation. These changes have shifted 

the water-surface elevation at the gaging station as much as 5 feet without a 

change in discharge. In addition to improving the stage-discharge relation, 

the structure provides a section where the concentration of the total sediment 

discharge of the channel can be measured.

INTRODUCTION

A stream gaging control structure for the Rio Grande conveyance 

channel near Bernardo, N. Mex., was designed on basis of model 

studies and field observations of the channel characteristics. The control structure is intended to stabilize the stage-discharge relation and to 

facilitate measurement of total sediment discharge at a site 5 miles 

below the channel-head gates. This report describes the problems 

and site conditions for the conveyance channel, the recommended control design and position in the channel, and the details of the model 

study.

The conveyance channel, which is about 80 feet wide and has bed 

and banks composed of fine sand (median diameter of 0.24 mm), is 

designed to transport all riverflows up to about 2,000 cfs (cubic feet 

per second); the old river channel is now used as a floodway. Flows 

greater than 100 cfs occupy the full width of the channel; lesser flows 

occupy only the streambed. Median flow is 280 cfs, and flows exceed 1,000 cfs 16 percent of the time (fig. 29). The bottom slope ranges 

from about 0.00055 foot per foot in the upper V/2 miles to about 0.0008

123
124 RIVER HYDRAULICS

3000

2000

1000

500

400

300

200

100

30

20

5

4

3 -

1955 to 1960 water years

Note: No flow 6 percent of the time

005 0.1 0.2 05 1 20 30 40 50 60 70

PERCENT OF TIME DISCHARGE EQUALED 

OR EXCEEDED THAT SHOWN

FIGDEE 29. Duration curve of daily flow, Rio Grande conveyance channel near 

Bernardo, N. Mex.
FIGURE 30. Map of Bernardo area. bO
126 RIVER HYDRAULICS

foot per foot in the lower reaches. The location of the present gaging 

station and the site selected by engineers of the U.S. Geological Survey 

and the U.S. Bureau of Reclamation for the control structure are given 

in figure 30. Photographs of the control-structure site are showyn in 

figures 31 and 32.

Both the configuration and mean elevation of the channel bed 

change wy ith discharge. As shown in figure 33, twy o different depthdischarge relations occur. During lo\v flows dune-bed configuration 

generally occurs, changing to plane-bed configuration at discharges between 500 and 1,200 cfs. However, a dune bed has been observed at 

flows as large as 2,000 cfs and a plane bed, at flows as small as 200 cfs. 

The change in velocity associated with the change in bed configuration 

is given in figure 34. Channel conditions for 1961 are indicated on 

figures 33 and 34 by measurements numbered 968 to 975. The stagedischarge relation, in addition to being affected by all the factors of 

variability of the depth-discharge relation, is affected by the changes 

in bed elevation. The mean bed elevation at the gage has varied between a maximum gage height of about 5 feet and a minimum gage 

height of slightly less than 1 foot during the period 1955-61. This 

variation of 4 feet in mean bed elevation may occur in a single \vater 

year. (See fig. 36.) An increase in discharge is generally accompanied 

by an increase in bed elevation, and a decrease in discharge is usually 

accompanied by a decrease in bed elevation; however, exceptions have 

occurred, as showT n in figures 35 and 36. Bankfull stage, about 9.5 feet, 

occurs at discharges of about 2,000 cfs, accompanied by a combination 

of high bed elevation and a dune-bed configuration.

FIGURE 31. Rio Grande conveyance channel, near Bemardo, with a flow of 700 cfs. 

is downstream toward proposed control site.

View
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 127

FIGURE 32. Rio Grande conveyance channel, near Bernardo, without flow. View is 

downstream toward proposed control site.

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ote: Numbers 968 to 975 indicate 

measurements made in 1961

^-

0 200 400 600 800 1000 1200 1400 1600 1800 

DISCHARGE, IN CUBIC FEET PER SECOND

FIGURE 33. Relation of width and depth to discharge on the Rio Grande conveyance 

channel near Bernardo, N. Mex.

735-728 O-64-2
128 RIVER HYDRAULICS

969 Plane bed

970 974 Dune bed

z

Note: Numbers 968 to 975 indicate 

measurements made in 1961

0 200 400 600 800 1000 1200 1400 1600 1800 

DISCHARGE, IN CUBIC FEET PER SECOND

FIGURE 34. Relation of velocity to discharge on the Rio Grande conveyance channel near

Bernardo, N. Mex.

10

9

8

7

6

5

4

3

2

1

0

2000

1500

8 1000

50°

Water-surface 

elevation

Mean bed elevation

Feb April May June July Aug Sept Oct Nov Dec

FIGURE 35. Variation in water-surface elevation, bed elevation, and discharge during 1957.
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 129

Mean bed elevation

FIGURE 36. Variation in water-surface elevation, bed elevation, and discharge during 1958.

An auxiliary gage was operated at the proposed site during the 

summer of 1961 to determine prototype conditions. The data for this 

gage is given in table 1. The auxiliary gage was 1,000 feet downstream 

from the present gage, and the differences in mean sea level elevation 

are consistent with the slope of the channel. The hydraulic characteristics of the channel at the site of the proposed control structure are 

probably the same as those at the present gage, on the basis of channel 

appearance and a comparison of observations at the auxiliary gage 

with the record at the present gage.

The purpose of the model study was to determine a control-structure design that would increase the accuracy of the water-discharge

TABLE 1. Observations of gage height and mean sea-level elevations, in feet, of the 

water surface at the present and auxiliary gage

Date

5-19-61_.____-___._

Do_______.___.

5-22-61-__________-

5-26-61_..___-_____

6- 2-61 _.- _ . __

6- 5-61__.___._____

6- 9-61.____--_____

Discharge 

(cfs)

0 

1,210 

1, 170 

1,230 

1,090

932

Present gage

Gage 

height

0 

8.44 

8. 30 

8.29 

7.95 

8. 08 

7.47

Mean 

sea level

4, 719. 23 

4, 727. 67 

4, 727. 53 

4, 727. 52 

4, 727. 18 

4, 727. 31 

4, 726. 70

Auxiliary gage

Gage 

height

0 

4.70 

4.66 

4. 72 

4.25 

4.46 

3.86

Mean 

sea level

4, 722. 14 

4, 726. 84 

4, 726. 80 

4, 726. 86 

4, 726. 39 

4, 726. 60 

4, 726. 00
130 RIVER HYDRAULICS

records from 10-15 percent (at present) to 5 percent and to decrease 

the number of discharge measurements needed to obtain the record

(at present discharge measurements are made weekly). Also, the 

control structure should provide for the measurement of the total 

sediment discharge of the channel.

The objectives of the model study were as follows:

1. Determination of a suitable control-structure design that would 

stabilize and increase the sensitivity of the stage-discharge relation. The structure would have to eliminate, or at least minimize, the effects of changes in bed configuration and changes in 

bed elevation on the stage-discharge relation. The desired sensitivity of the control structure would be a stage-discharge 

relation in which the change in discharge would be less than 1.5 

percent for a 0.01-foot change in stage.

2. Determination of the maximum elevation of a control crest which 

would not create sufficient backwater to interfere with the maximum design capacity of the channel (2,000 cfs) ; also, determination of the backwater characterists of the control under 

various degrees of submergence. This information, along with 

the prototype stage-discharge relation, would be used in determining the recomended elevation of the control crest.

3. Selection of a section or sections where accurate measurements of 

water discharge and sediment discharge can be made.

4. Design an energy dissipator to eliminate adverse scour downstream 

from the control structure.

The site conditions present many problems in meeting the objectives 

of the control study. The major problems are (1) the variation in 

the bed elevation, (2) the changing bed form, (3) the low bankfull 

stage, (4) the proximity of the head gates, and (5) the scouring 

nature of the fine-grained bsd material.

The control structure must be located above the maximum bed 

elevation to be stable and free of sediment; however, the low bankfull 

stage governs the maximum elevation of the crest. Also, the changing bed form creates a problem in determining the crest elevation 

because a control crest that is too high may cause a rougher dune bed 

form, resulting in greater resistance to flow and consequent larger 

flow depths. Larger flow depths would restrict the capacity of the 

channel, either because of overbank flow or backwater at the diversion 

structure. If the control crest is too near the maximum bad elevation, 

submergence is a problem because changing bed form and elevation 

downstream will result in variable submergence.

The fine-grained bed material scours easily, and probably requires 

laying down some riprap for protection. Also, the horizontal con-
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 131

striction desired for control sensitivity is limited by the resulting sand 

erosion.

The authors gratefully acknowledge the advice and assistance given 

by D. B. Simons, D. W. Hubbell, W. L. Haushild, and W. L. Heckler 

of the U.S. Geological Survey, E. L. Pemberton of the U.S. Bureau of 

Reclamation, and R. V. Asmus and R. Garza of Colorado State 

University.

PROPOSED CONTROL STRUCTURE 

RECOMMENDED CONTROL-STRUCTURE DESIGN

On the basis of the model studies (see Experimental procedures and 

equipment) conducted in the hydraulic laboratory at Colorado State 

University, the following control structure (type K) is proposed for 

installation at the Rio Grande conveyance channel near Bernardo, 

N. Mex.

The recommended control-structure design is given in figures 37 and 

38. Model studies indicated that a control surface, 16 feet long, having 

a longitudinal slope of 16:1 and a transverse slope of 35:1, an approach apron slope of 2:1, and a downstream apron slope of 3:1 would 

provide a control structure with a stable stage-discharge relation under 

all but the most severe conditions. The transverse crest slope forms 

a low V-notch to provide a higher degree of rating sensitivity and to 

concentrate the low flows. A V-notch having a 40:1 lateral slope was 

found to change discharge 1.5 percent or less for a 0.01-foot change in 

stage at 400 cfs or more (fig. 39). At less than 400 cfs, the change in 

discharge for a 0.01-foot change in stage increases gradually to 7 

percent at 30 cfs. A transverse slope of 35:1 is recommended for the 

proposed control structure. Additional convergence or installation 

of a sharper V-notch in the control structure tends to create an irregular 

water surface and causes scour.

A set of baffles mounted on the upstream edge of the crest apron 

(fig. 10) served to keep the low part of the V-notch clear of sand under 

all model conditions. A small teardrop-shaped mounting provided 

a means of keeping the bubbler-gage orifice above any layers of sand 

that encroached downstream toward the crest. The "teardrop" was 

located with its top 0.05 foot below the crest at a point 4 feet upstream 

from the crest (fig. 38). Water-surface profiles (fig. 40) showed that 

auxiliary orifices could be placed at points 5 feet and 8 feet upstream 

from the crest. Orifices placed any further than 8 feet upstream 

from the crest could be affected by a small surface wave or by sand 

encroachment. Sand intrusion on the control surface outside the 

baffle zone did not seem to create any unusual water-surface conditions 

or to affect the rating adversely.
132 RIVER HYDRAULICS 

Cutting surface C 

Cutting surface B

Cutting surface D

Cutting surface A

T

Section A

6.65'

5.5'

Section C

Section B

Section D 

FIGURE 37. Details of proposed control structure.
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 133

Control crest

Dissipator

Section of downstream apron showing 

energy dissipator and sampling curb

Control crest

Auxiliary orifice' 

mount

Main orifice 

mount

Proposed orifice positioning

3.7'

Flow

Upstream edge 

of crest

3' 2.8'

Baffle positioning 

FIGUEE 38. Accessories of proposed control structure.
134 RIVER HYDRAULICS

4.0

Q

Ld

K hD OT 

Cfl Ld

Ld CJ

Q CC 

Ld V)

3.0 h

2.0

1.0 h

0.5

0.3

5 percent accuracy

G Plane bed and washed-out dunes (40 baffles)

A Washed-out dunes and dunes (40 baffles)

V Washed-out dunes and dunes (10 baffles)

30 50 100 300 500 1000 2000

DISCHARGE, IN CUBIC FEET PER SECOND 

FIGURE 39. Stage-discharge relation for control K.

An energy dissipator sill, 1.5 feet high, at the toe of the downstream 

face of the control prevented excessive downstream scour. However, 

for protection against scour, riprap may be needed on the bed and 

along banks for a short distance downstream from the dissipator. 

Riprap along banks in the vicinity of and upstream from the control 

structure may also be necessary. The elevation of the top of the sill 

should be the same as the low bed elevation. This elevation would 

be 4,720.2 feet at the present gage or 4,719.5 feet at the auxiliary site, 

if one assumes that a change in bed elevation would be equal to the 

change of the water-surface elevation given in table 1.

BECOMMENDED CONTBOL-STBUCTUBE POSITION

It is recommended that the elevation of the crest of the control structure be located 4.50 feet below bankfull stage, which is equivalent to 

a mean sea level elevation of 4,724.2 feet at the present gage and 4,723.5 

feet at the auxiliary gage (proposed control-structure site).

Discharge measurements, made in the spring of 1961 and plotted 

on figures 30, 31, and 41, indicate lower regime flow having great 

depth, low velocity, and maximum gage height. Therefore, elevations 

given in table 1 should indicate maximum water-surface conditions 

for the given water discharge. The crest, elevation 4,723.5 feet, would 

be approximately 1.5 feet above the mean bed elevation. However, 

the crest of the control structure would be only 0.5 foot above the
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 135

10 15 20 

DISTANCE, IN FEET

25 30

FIGURE 40. Water-surface profiles for control K. (Free-fall conditions.)

10

O Discharge measurements of highest 

water-surface elevation

500 1000 1500 2000 

DISCHARGE, IN CUBIC FEET PER SECOND

2500

FIGURE 41. Stage-discharge relations for maximum and average tail-water levels. (Based

on field data.)

735-728 O-64-3
136 RIVER HYDRAULICS

maximum bed elevation measured in 1958 and would be 0.25 foot lower 

than the maximum bed elevation measured in 1957. A higher crest 

elevation is not recommended because the effects on the bed configuration are not known; a change in the bed configuration could result in 

higher resistance to flow and in greater depths, which would cause the 

channel not to operate at design capacity.

The elevation of the control was determined from the model study, 

which indicated that at 2,000 cfs and 100 percent submergence the 

upstream water-surface elevation would be 4.0 feet above the crest 

of the control (fig. 42). If 4.0 feet is subtracted from the maximum 

tail-water elevation at 2,000 cfs (fig. 41) the crest is computed to be 

4.25 feet below bankfull stage. However, if 0.5 foot of freeboard from 

bankfull stage is allowed, the control crest is placed 4.50 feet below 

bankfull stage or elevation 4,724.2 feet at the present gage. If the 

change in water-surface elevation between the present gage and the 

auxiliary gage is assumed to be the same for 2,000 cfs as for the lower 

discharges, the crest elevation is 4,723.5 feet.

If the crest is placed at 4.50 feet below bankfull stage, the data 

from the present gaging station indicate that free fall would occur 

at flows of less than 300 cfs under maximum tail-water conditions. 

However, under average tail-water conditions, free fall would occur 

at flows as great as 1,100 cfs. The rating curves shown in figures 

43 and 44 were constructed to indicate possible measurement scatter

Percent submergence 

10 20 30 40 50 * 60 70 80 90 100

EXPLANATION

a Measured 4 ft upstream from sill 

6 Measured 16 ft upstream from silt

DEPTH OF TAILWATER ABOVE SILL, IN FEET 

MEASURED 60 FEET DOWNSTREAM

1.0 2.0 3.0 4.0 5.0 6.0

FIGURE 42. Submergence carves for control K.
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 137

50 100 200 500 1000 

DISCHARGE, IN CUBIC FEET PER SECOND

2000

FIGURE 43. Comparison of free fall average submergence and maximum submergence 

ratings for a control crest 4.5 feet below bankfull stage. (Based on field and model 

data.)

4.0

D CO

co uj 3.0

.< o:

2.0

UJ CO

r Q1 H

1.0

Average submer 

m submergence

Free-fall rating 

(K control)

50 100 200 500 1000 

DISCHARGE, IN CUBIC FEET PER SECOND

2000

FIGOBE 44. Comparison of free fall average submergence and maximum submergence 

ratings for a control crest 4.0 feet below bankfull stage. (Based on field and model 

data.)
138 RIVER HYDRAULICS

resulting from variable submergence. Figure 43 was constructed 

under the assumption that the crest was 4.5 feet below bankful stage. 

Figure 44 indicates the improvement in the rating, if the controlstructure height is raised 0.5 foot. The curves show the maximum 

scatter that could be anticipated as a result of variable submergence. 

A comparison of the flow-duration curve (fig. 29) and figure 43 indicates that free-fall conditions could be expected 50 percent of the time 

under maximum submergence conditions and 87 percent of the time 

under average submergence conditions.

DISCHARGE MEASUREMENTS ON THE CONTROL STRUCTURE

Vertical-velocity curves for a cross section 9 feet upstream from 

the control-structure crest are shown in figures 45 and 46. Slight 

velocity irregularities are indicated directly downstream from the 

baffles. However, reasonably consistent mean velocities could be obtained by using the three-point method in the baffle area (Corbett 

and others, 1945). Outside the baffle area or from 8 feet either side 

of the crest to the banks, indications are that 0.6-foot depth readings 

would yield a velocity as close or closer to the true mean than 0.2-foot 

and 0.8-foot depth readings. Small horizontal angles may exist downstream from the baffles, although the model study indicates that the 

angles are negligible.

Station 40 Station 30 Station 20 Station 10

20 

40 

60 

80 

nn

c

J

jf

f

0

[

= 2000 cfs

VELOCITY (FPS) 

Mean velocity=2.40 fps 

0.2 and 0.8 velocity=2.34 fps 

0.6 velocity=2.47 fps 

3-point method=2.40 fps

VELOCITY (FPS) 

Mean velocity=2.55 fps 

0.2 and 0.8 velocity = 2.60 fps 

0.6 velocity^ 2.57 fps

VELOCITY (FPS) 

Mean velocity=2.56 fps 

0.2 and 0.8 velocity=

2.61 fps 

0.6 velocity= 2.57 fps

VELOCITY (FPS) 

Mean velocity=2.65 fps 

0.2 and 0.8 velocity=2.64 fps 

0.6 velocity=2.63 fps

Station 

40 30 20 10 0

Note: Velocities are for model. 

Convert to prototype by 

multiplying by factor 3.15

Plan view of control

FIGURE 45. Vertical-velocity curves based on data taken 9 feet upstream from the crest.

(Free-fall conditions.)
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 139

Station 40 Station 30 Station 20 Station 10

80

100

VELOCITY (FPS) 

Depth =1.7 ft 

Mean velocity=0.85 fps 

0.2 and 0.8 velocity=0.86 fps 

0.6 velocity=0.86 fps

80

100

VELOCITY(FPS) 

Depth = 3.10 ft 

Mean velocity=1.80 fps 

0.2 and 0.8 velocity = 1.70 fps 

0.6 velocity = 1.87 fps 

3 point velocity=1.78 fps

= 500 cfs

VELOCITY (FPS) 

Depth=1.4 ft 

Mean velocity=0.87 fps 

0.2 and 0.8 velocity=0.87 fps 

0.6 velocity=0.86 fps

VELOCITY (FPS) 

Depth = l.l ft 

Mean velocity=0.74 fps 

0.2 and 0.8 velocity=0.75 fps 

0.6 velocity = 0.75 fps

Q= 1200 cfs

1

VELOCITY(FPS) 

Depth=3.98 ft 

Mean velocity= 1.87 fps 

0.2 and 0.8 velocity= 1.88 fps 

0.6 velocity=1.87 fps

VELOCITY (FPS) 

Depth 2 67 ft 

Mean velocity=1.85 fps 

0.2 and 0.8 velocity=1.86 fps 

0.6 velocity= 1.85 fps

VELOCITY (FPS) 

Depth=0.9 ft 

Mean velocity=0.61 fps 

0.2 and 0.8 velocity=0.62 fps 

0.6 velocity=0.61 fps

VELOCITY (FPS) 

Depth 2.45 ft 

Mean velocity=1.71 fps 

0.2 and 0.8 velocity=1.72 fps 

0.6 velocity=1.70 fps

FIGURE 46. Vertical-velocity curves based on data taken 9 feet upstream from control crest.

(Free-fall conditions.)

The vertical-velocity curves are actually plotted to model velocities. 

By multiplying by the factor 3.15 to convert to prototype velocities, 

it is evident that velocities exceeding 8 fps (feet per second) are possible at 2,000 cfs under free-fall conditions. Actually, the control 

structure should be submerged at the higher flows. If so, it is unlikely 

that the velocities would exceed 6 fps. Because of the longitudinal 

and transverse crest slope, care must be taken in sounding and positioning the meter in order to ensure that the true depth and velocity are 

measured. This procedure may require heavier sounding weights 

than are normally used.

SEDIMENT SAMPLING FROM THE CONTROL STRUCTURE

A curb, 0.2 foot high, installed at a position 0.5 foot vertically below 

the crest on the downstream apron (fig. 10) provides a means of taking 

total sediment-load samples. The design and location of the curb 

were determined by a study made in conjunction with the energy 

dissipator. The horizontal fillet upstream from the curb eliminated 

excessive water-surface disturbance on the apron and improved the 

vertical distribution of the sediment. The curb, in addition to improving the sediment distribution, provided a satisfactory means of
140 RIVER HYDRAULICS

sampling the total flow depth by allowing the sample nozzle to touch 

the apron floor. The curb was positioned 0.5 foot below the crest to 

eliminate any possibility of affecting the depth-discharge relation. 

If it had been positioned any lower, there would have been a possibility 

of the sand bed covering the sampling point under adverse conditions. 

Samples could be obtained from the curb under low-flow conditions by 

wading on the crest of the control structure and reaching downstream 

to sample the flow. Naturally, care would have to be taken when 

sampling by this method so as not to disturb the flow upstream from 

the sampler. Sampling under high-flow conditions would have to be 

accomplished by using a guide to position the sampler. It is suggested 

that a channel iron be bolted to the apron, and the area between the 

apron and the upstream leg be filled with cement. The area between 

the upstream and downstream legs of the channel should be left open 

to serve as guide-rod supports. Another possibility would be to use 

the angle between the apron and the horizontal fillet as guide-rod 

supports.

A pump sampler developed by the Federal Inter-Agency Sedimentation Project at the St. Anthony Falls Hydraulic Laboratory (H. H. 

Stevens, Jr., oral commun.) could be used to measure the sediment 

concentration. Accomodations could be provided for the piping 

leading from the pump sampler to oe mounted either in the curb fillet 

or downstream from the lower leg of the channel iron. If a pump 

sampler is used, two nozzles should be installed: one nozzle downstream from the low point in the control and the other nozzle downstream from the lateral, one-third position. The clearing effect of the 

baffle in the center of the control should be considered when obtaining 

pump samples. By proper calibration of the two nozzles, accurate 

total sediment-load samples could be obtained.

SUGGESTIONS FOB CONSTRUCTION AND OPERATION

A control structure built of loosely grouted rock to a depth 10 feet 

below bankfull stage or 1.5 feet below low bed elevation should provide 

a stable structure. Cutoff walls of sheet piling at or near the upstream 

and downstream toes of the weir would add to the stability. A 3- to 

5-inch concrete cap should be placed at the top of the structure. A 

smooth crest surface would decrease both the amount of backwater and 

the possiblity that large sand deposits might accumulate, as indicated 

in baffle studies. Possible exposure of the bare rocks on the downstream apron may be useful for additional dissipation of energy.

David Hubbell, associated with the Dunning flume (Benedict and 

others, 1953), indicates that baffles constructed of sheet steel welded to 

angle irons would be superior to the mounting used for the Dunning
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 141

installation. Bolts could be set in the proper position on the control 

apron, and the welded angle iron baffles could be installed or removed 

as needed.

Installation of a simple tail-water gage at a point 60 feet downstream 

from the control crest (this distance provided representative tail-water 

readings in the model studies) would provide submergence information. A small well and shelter containing a continuous recorder would 

be adequate. The low-water record at this tail-water gage would be 

unnecessary because submergence would occur only at the higher flows.

EXPERIMENTAL PROCEDURES AND EQUIPMENT

The model study was made in three phases. First, two-dimensional models were tested in the 2- by 60-foot flume to determine the 

most suitable design. This design was then checked and modified in 

a three-dimensional model in the 8- by 150-foot flume. The third 

phase was the development of an energy dissipator to decrease downstream scour.

In order to simulate the different bed forms that occur in the 

prototype in the 2-foot flume, the slope of the flume was varied. At a 

slope of 1.0 percent, a plane bed existed for all model discharges. At 

a slope of 0.7 percent, a plane bed existed for discharges larger than 

about 1,000 cfs, and a dune-bed form existed for discharges less 

than 1,000 cfs. At a slope of 0.3 percent, a dune-bed form existed 

for all discharges. Eatings were established for each control at 

the different flume slopes.

Slope was not changed in the 8-foot flume. Instead, the vertical 

position of the model control structure was changed to create the 

various bed conditions.

PLUMES

The 2-foot-wide flume used in the two-dimensional study was 60 

feet long and 2.5 feet deep. Its walls were of plexiglass, and its 

bottom was of metal. The flume was equipped with a 12-inch centrifugal pump that recirculated sediment and flows up to 7.5 cfs. The 

discharge was regulated by a gate valve and was measured by a calibrated orifice in the discharge line. The slope of the flume could be 

changed automatically.

The 8-foot-wide flume used for the three-dimensional study was 

150 feet long and 2 feet deep. The flume was equipped with a 12-inch 

and a 19-inch recirculating pump system having a discharge capacity 

of up to 21 cfs. The walls were of plexiglass and plywood, and the 

bottom was of plywood. The discharge was regulated by valves and 

measured by calibrated orifice meters in discharge lines from each 

pump. In this study either the 12-inch or the 19-inch recirculating
142 RIVER HYDRAULICS

pump was used, but they were never used together. The model control structure was installed 12 feet from the downstream end. To 

study the effect of submergence, an adjustable gate at the downstream 

end of the flume was used to create backwater. To determine the most 

effective energy dissipator, the limits of scour were determined; the 

control structure was moved 60 feet upstream to obtain a sufficientlength of sand bed.

SEDIMENT

The sediment used in the 2-foot flume was quartz sand having a 

median fall diameter of 0.33 mm and a specific gravity of 2.65. The 

material in the 8-foot flume was quartz sand having a median 

fall diameter of 0.19 mm. and a specific gravity of 2.65. The sediment in both flumes was about 0.5 foot deep.

WEIR MODELS

Most of the models were made of %-inch plywood, although some 

were made of sheet metal and molding plaster. Various models were 

tried, but all had the basic dimensions found most favorable in the 

Del Kio studies (Karaki, 1961) . All models had a downstream apron 

slope of 3 : 1 and an upstream apron slope of 2 : 1.

MODEL SCALES

A scale of 1 : 8 was chosen for the two-dimensional studies. This 

scale was chosen for the 8-foot flume to amplify the detail of the basic 

structure. This scale related only to the structure and to the fluid 

flow and not to the sand grain size or dune heights. The following 

relationships apply :

A scale of 1 : 10 was used for the 8-foot flume. This ratio was convenient because the average prototype channel width is 80 feet ; hence, 

0.1 on the model represents 1 foot on the prototype. The following 

relationships apply to the 8- foot flume models :
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 143

EXPERIMENTAL RESULTS AND DISCUSSIONS

WEIR, A

Weir A, figure 47, was a modification of Karaki's (1961) type G 

control. A transverse slope was incorporated into the downstream 

control lip to form a V-notch, whose purpose was to increase the accuracy of results and to confine low flows. Adverse waves occurred, 

however, just upstream from the lip at flows of more than 900 cfs. 

After a short period, the sand moved in and covered the apron upstream from the control lip. This encroachment eliminated this control structure from consideration.

WEIR B

Weir B used a longitudinally sloping crest similar to Karaki's 

(1961) type F control (fig. 47). During tests of high flows the crest 

stayed clear, but at flows of less than 800 cfs fingers of sand encroached 

to within 2 feet of the crest.

WEIRS C, D, E, AND F

Weirs C, D, E, and F (fig. 47) were tested using the same basic shape 

as weir B, but their longitudinal crest slope was 18 : 1. Also, various 

forms of transverse sloping crests were superimposed on the basic 18 : 1 

longitudinal slope to concentrate the flow, to improve the rating, and 

to increase movement of sand over the control. Weirs C, D, and E 

represented varying degrees of convergence. The sand was swept 

across the apron for all flows of 500 cfs and greater. At flows of less 

than 500 cfs, the sand encroached to within 1 foot of the crest and was 

concentrated in the middle of the apron. Convergence of the flow to 

the center was noticeable on all three weirs. Adverse waves were also 

noted. Weir F was of the same design as weir E, except that baffles 

were mounted on the upstream edge.
144 RIVER HYDRAULICS

Flow

0.2ft

Side

Weir A

0.19'

Front

Side

Weir B

Control

C«? =63.5°) 

D(0 =47°) 

E(0 =24.5°) 

F(Same as E, but with 

baffles upstream)

-2.0 ftPart modeled in 2-ft flume 

plan

1-1.0 ft-l

Side Front 

FIGURE 47. Design of model weirs A, B, C, D, B, and F.
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 145

Three rows of baffles having spacing and heights similar to the 

turbulence flume on the Middle Loup River were used (Benedict and 

others, 1953; see also "Baffle studies", this report). The three rows of 

baffles were not effective in keeping the weir clear of sand, and an 

irregular water surface resulted. Because these control structures had 

some undesirable characteristics, further modification to obtain a more 

suitable design seemed desirable. Stage-discharge curves are shown 

in figure 48.

WEIR G

Weir G used a V-shaped apron having a longitudinal crest slope 

of 18:1 and transverse crest slope of 35:1 (fig. 49). Water-surface 

conditions were relatively smooth at all flows. At flows below 500 

cfs there was a tendency for the sand to collect in the low part of the 

control. Deflecting baffles were used upstream, and by proper 

positioning the sand was eliminated.

WEIR H

Because of the success of weir G, a new basic control structure, weir 

H, was modeled for further and more detailed study. This control 

had a longitudinal crest slope of 16:1 but no transverse slope to converge the flow (fig. 49). Rating for weir H is shown in figure 50.

Ul

DC H 

D <S) 

V) UJ 

< QC 

UJ O

H O

Ul rr

Ul u.

. UJ 

Q QC

4.0

3.0

2.0

£ LJ- 1.0

 © Control C: Plane and dune bed 

A A Control D: Plane and dune bed 

T V Control E: Plane and dune bed

500 1000 1500 2000 

DISCHARGE, JN CUBIC FEET PER SECOND

FIGURE 48. Stage-discharge relations for controls C, D, and, E.

2500
146 RIVER HYDRAULICS

Note: Made of sheet metal

Flow

18:1

Side

Part modeled in 2-ft flume

Front

WeirG

-2.0 ft16:1

Weir H (basic structure flat surface)

0.5'

Note: Weirs I and J used same 1.5'

basic structure as H but I

with converging apron J_

-2.0 tPart of I modeled in 2-ft flume 

plan

18:1

Front (I)

35:1

Front (J) 

FIGURE 49. Design of model weirs G, H, I, and J.

1

0.38'

T
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 147

4.0

sg £ l±J O

I- O

UJ DC

Q DC

3.0

2.0

< UJ

l±J UJ

£ " 1.0

</> t 

Q.

D a Control H: Dune bed

O Control I: Dune bed and plane bed

A A Control J: Dune bed and plane bed

0 500 1000 1500 2000 2500

DISCHARGE. IN CUBIC FEET PER SECOND 

FIGURE 50. Stage-discharge relations for controls H, I, and J.

WEIR I

Weir I was a modification of weir H, to which a transverse crest slope 

was added. The longitudinal crest slope was 16:1, and the transverse 

slope was 18:1 (fig. 49). This model control structure gave a smooth 

and even rating (fig. 23), except that at the 1-percent slope there was 

a shift in critical flow point between 1,000 and 1,500 cfs. This shift 

probably resulted from the modeling technique used to obtain a plane 

bed, and so will not occur in the prototype. Sand encroached on the 

low part of the V-notch to within 2 feet of the crest. A set of deflecting baffles, installed at the upstream edge of the crest, cleared off the 

low part of the crest. The transverse crest slope resulted in an1 undesirable convergence of the flow.

WEIR J

Weir J was of the same design as weir I, except that the transverse 

crest slope was changed to 35:1 (fig. 49). The rating for this control 

had the same shape as the rating for control I at the 1 percent slope 

(fig. 50). Baffle arrangements 2 and 9 (fig. 53) were effective in keeping the crest free of sand.

Because of the favorable results obtained in the two-dimensional 

model study, control J was selected for study in the 8-foot flume. In
148 RIVER HYDRAULICS

the 8-foot flume the longitudinal crest slope was 16:1, the transverse 

crest slope was 40:1, the approach apron slope was 2:1, the downstream apron slope was 3:1, and there was variable slope in the transition from the approach apron to the crest of the weir. A comparison 

of the basic control structure (control H) and the control J as modeled 

in the 8-foot flume is given in figure 51. The figure also includes a 

comparison of control J as modeled in the 2 and 8-foot flumes. Obviously the two-dimensional model study did not take into account the 

converging effect that the transverse slope had on the flow.

A series of 40 baffles was installed at the upstream edge of the transition from the approach apron to the crest. The transition slope on 

the upstream end of the apron rendered the outside baffles ineffective. 

Also, small bits of debris collected on the closely spaced baffles.

WEIR K

Weir K was a modification of weir J and was designed to eliminate 

unfavorable water-surface conditions and to simplify the shape for 

easier construction. This design was tested and recommended for 

installation at the proposed site. (See "Proposed control structure.")

Q

UJ K. \- 

D CO CO UJ

< o: 

iu O

£ <

UJ 

Q K <r i~ 

S oo

4.0

3.0

2.0

1.0

0.5

J contro 

J contro 

H contr 

J contro 

J contro 

J contro

I

EXPLANATION

I: Dune and plane bed (no baffl 

I: Dune and plane bed (baffles) 

I: Ripple and dune bed 

I: Ripple and dune bed 

I: Dune and plane bed 

I: Plane bed

2-ft flume

8-ft flume

100 200 500 1000 2000 

DISCHARGE, IN CUBIC FEET PER SECOND

FIGURE 51. Comparison of stage-discharge relations for basic controls H and J, modeled in

2- and 8-foot flumes.
STREAM GAGING CONTROL NEAR BERNARDO, N. HEX. 149

A comparison of the ratings for controls J and K modeled in the 8- 

foot flume is given in figure 52.

BAFFLE STUDY

A study was made to determine the effectiveness of baffles located 

along the upstream edge of a control structure in keeping the structure 

clear of sand. Position 9 (fig. 53) more than any other baffle arrangement modeled kept the crest clear of sand, brought about less watersurface disturbance, and lessened the occurrence of horizontal angles 

on the crest. The baffles in the upstream row were of the same dimensions as those used in the Dunning flume ; that is, 1.0 foot high and 2.0 

feet wide. The downstream baffle was 0.5 foot high and 2.0 feet wide. 

The baffles brought about less water-surface disturbance and were still 

effective when the top of the upstream row of baffles was set 0.1 foot 

(prototype distance) below the level of the control crest. However, 

if the baffles were set at too great a distance below crest elevation they 

were less effective. The baffle study is summarized in figure 53.

Q 

LU

£ I3 Cfl

(/) LU

< Of.

UJ

Q Of.

< \-

LJJ C/)

0.5

100 200 500 1000 

DISCHARGE, IN CUBIC FEET PER SECOND

2000

FIGURE 52. Comparison of stage-discharge relations for controls J and K, modeled in

2- and 8-foot flumes.
150 RIVER HYDRAULICS

Baffle positioning

^6 '~i ~ii:i 

t Flow 2>r

^ 0.5'

Upstream edge of apron 1 

Position 1

_\^v.z/4

Position 2

V

_\^X.ZZ/1

Position 3

\/

Position 4

Position 5

*HF=high flow 

**LF=low flow

Water surface

Extremely rough 

for all flows

*HF: A little choppy 

**LF: Pretty choppy

HF:Fairly smooth 

LF: Still a little 

choppy, but 

smoother than 

in position 1

HF:High hump at 

upstream baffles

LF: Creates bad 

wave in front of 

front baffles

Same as in 

position 2

Clearing effectiveness

Not too effective; 

slows down velocity so that sand 

will deposit on

Very good, but would 

make angular flow 

for measuring

Clears sand out 

at high flows 

(1000 and up). 

"V" baffle not 

as effective 

at low flow

Not as effective 

at high or low 

flow because it 

seems to slow 

down velocity 

and allow sand 

to deposit

Middle 6 to 8 feet 

of apron is 

kept clean

FIGURE 53. Baffle model study.
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX.

Baffle positioning

4

Flow \ \ / / 

Position 6

.Y^_

Position 7

~\ 2T 

_\_\V^_

Position 8

-|1.4|~| 2' |-

1 t

X.^_Z.^_.JL7

Position 9

»l O' L »

N ___ *j_

1 2'

Position 10

_\._____.Z_

Position 11

Water surface

Same as position 3

Same as position 5

Same as position 2, 

except does not 

cause as much 

turbulence

Same as position 8 

except slightly 

more turbulence 

but less than 

position 2

Very rough

Smoother than

Clearing effectiveness

Same as position 3

Same as position 5

Does not spread sand 

out quite as much 

as position 2

Less angular flow than 

position 2. Does not 

spread sand out quite 

as much as position 2 

More effective than 

position 8

Same as position 1

Fair. Not quite as 

good as positions

2 or 9

FIGURE 53. Continued.
152 RIVER HYDRAULICS

ENERGY DISSIPATOR STUDY

A model study was conducted to determine the most effective energy 

dissipator for controlling and minimizing downstream scour. It must 

be emphasized that model studies of scour can give only qualitative 

results. For example, the model study indicates that a reverse roller 

keeps sand piled against the downstream toe of the structure. Presumably, the design that performs best in the laboratory will perform 

best in the field. For this reason, all the results of the test are reported for the model except the discharge, which is reported for the 

prototype.

The study involved the use of sills located at various positions on 

the downstream apron whose slope was 3:1. Also, baffles upstream 

from the sills were tried in an attempt to determine if they could improve the jump action.

Two tail-water conditions were considered in conducting the study. 

One, termed "theoretical minimum tail-water elevation" was the tailwater elevation that resulted from adding the depth of flow (fig. 33) 

for the discharge being modeled to the low bed elevation. The other 

condition, termed "low tail-water elevation," was taken from the low 

gage-height curve (fig. 41). Low bed elevation from a study of the 

field data was 4 feet below the low point on the control crest. These 

tail-water elevations, in feet above low bed elevation, are given in 

table 2.

TABLE 2. Tail-water depths, in feet, above low bed elevation

QP (cfs) 

(Prototype)

500. ______________

1,000___. _____________ _

1,500_____________

2,000_________________ _._

Minimum tail-water elevation

Prototype

1. 64 

2. 47 

3. 29

4. 09

Model

0. 16 

. 25 

. 33 

. 41

Low tail-water elevation

Prototype

2. 7 

3. 7 

5.2 

6.6

Model

0. 27 

. 37 

. 52 

. 66

The study of the various sill heights and locations and the results of 

the study are summarized in figure 54. Models 1 and 2 had sills that 

were located too high above low bed elevation. This situation resulted 

in excessive scour downstream, as compared with scour in other models. 

The top of the sill in model 3 was located at low bed elevation, and as 

indicated in figure 26, scour was lessened at 500 and 1,000 cfs but not 

at 1,500 and 2,000 cfs when tail-water elevation was at a minimum or 

lower. Under low tail-water conditions, however, scour was lessened. 

The purpose of model 4 was to decrease scour by extending the apron 

length without increasing the height of the sill. At minimum or 

lower tail-water elevation this model worked well at the two lower
STREAM GAGING CONTROL NEAR BERNARDO, N. MEX. 153

in M >

s »1

m ? "L

§ s

5 g E

O °. D

(/) CSJ I

O 00

o o o

o o o

CSJ IT) O ) O IT) IT) O O

) O O OO

g

o o o

o oo
154 RIVER HYDRAULICS

flows, but excessive scour occurred at the higher flows. Model 5 was 

an attempt to decrease the scour by using a horizontal basin. In 

this model also excessive scour occurred downstream from the sill. 

Model 6 was a slight modification of model 3, in which the sill height 

was increased 0.5 foot, but in which the sill crest was kept at low 

bed elevation by extending the apron 1.5 foot. This energy dissipator 

performed very well under minimum tail-water conditions, except at 

2,000 cfs. However, when the tail-water elevation was low, the scour 

was not excessive. It is questionable if tail-water elevation would ever 

be at the minimum theoretical elevation.

So that the performance of model 6 might be improved, baffles 0.03 

foot high and 0.2 foot long (model distance), spaced the same as those 

in position 1 (fig. 53) were placed on the face of the apron. Also 

placed were three rows of baffles, in which the crest of the lowest row 

was at the same elevation as the sill crest. The upper row was then 

removed so that only two rows were on the apron. The upper row was 

replaced and the lowest row was moved above the other two rows. No 

matter what the position of the baffles, they resulted in a decrease in 

efficiency because they caused the flow to leave the face of the apron 

and to override the sill. Preliminary investigation in which larger 

baffles were used indicated the same result.

The test data indicate that model 6 will protect the control structure 

and that excessive scour will not occur downstream unless tail-water 

elevation at 2,000 cfs becomes much lower than indicated by gageheight records. Then, a moderate amount of riprap may have to be 

laid down for protection. Model 3, although adequate, was not as 

effective as model 6.

LITERATURE CITED

Benedict, P. C., Albertson, M. L., and Matejka, P. Q., 1953, Total sediment load 

measured in turbulence flume: Am. Soc. Civil Engineers Proc., Separate 230.

Corbett, D. M., and others, 1945, Stream-gaging procedure: U.S. Geol. Survey 

Water-Supply Paper 888.

Karaki, S. S., 1961, Stream gaging control structure in the Rio Grande: Colorado 

State Univ. Research Found. Rept. CER 61-SSK17.
River Hydraulics

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1369

This water-supply paper was published as 

"eparate chapters ^4-E
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director
CONTENTS

[The letters in parentheses designate separately published chapters]

Page

(A) Selected topics of fluid mechanics, by Carl E. Kindsvater_ _ 1

(B) Energy losses associated with abrupt enlargements in pipes, with 

special reference to the influence of boundary roughness, by Carl E. 

Kindsvater ___________________________________ 53

(C) Surges in natural stream channels, by S. E. Rantz___________ 77

(D) Flow through openings in width constrictions, by Jacob Davidian,

P. H. Carrigan, Jr., and John Shen____________ __ 91

(E) Stream gaging control structure for the Rio Grande conveyance channel near Bernardo, New Mexico, by D. D. Harris and E. V. 

Richardson ___________________________________ 123

O