Mean Annual Runoff as 

Related to Channel Geometry 

of Selected Streams in California

By E. R. HEDMAN

CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES 

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1999-E

Prepared in cooperation with the 

California Department of 

Water Resources

UNITED STATES GOVERNMENT PRINTING OFFICE. WASHINGTON : 1970
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

First printing 1970 

Second printing 1977

For sale by the Branch of Distribution, U.S. Geological Survey, 

1200 South Eads Street, Arlington, VA 22202
CONTENTS

Abstract _________________________________ El

Introduction ___________________ _ ___ ___ _ 1

Study of channel geometry _______ ___ _ ___ _ 2

Collection of field data _ ________________ .: ____ - _ _ - 5

Method of analysis ___________________________ __ 10

Perennial streams _ __ _ __ __ ________ ____________ 11

Ephemeral streams _____________________________ 12

Repeated measurements at gaging stations ________ _ _ _____ 15

Conclusions ______________________________ _ _ 16

ILLUSTRATIONS

Tuge

FIGURES 1-6. Photographs showing 

1. Point bar along one bank of a perennial stream E6

2. Bars and berms along one bank of an ephemeral

stream __________________ 7

3. Vegetation line on right bank and bar on left

bank ________________________ 8

4. Well-defined point bar downstream from large

boulders in Taquitz Creek near Palm Springs 9

5. Material forming point bar at section 1 in

Arroyo Seco near Pasadena ___________ 9

6. Material forming point bar at section 3 in

Arroyo Seco near Pasadena __________ 10

7-10. Graphs showing 

7. Relation of annual runoff to channel width and

mean depth for perennial streams ______ 12

8. Comparison of observed and computed runoff

for perennial streams ______________ 13

9. Relation of annual runoff to channel width and

mean depth for ephemeral streams ______ 14

10. Comparison of observed and computed runoff

for ephemeral streams _____________ 15

TABLE

Page

TABLE 1. Computed and observed runoff at 48 gaging stations in

California ____________________________ E3

2. Results of repeated channel geometry measurements at

gaging stations ________________________ 16

III
CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

MEAN ANNUAL RUNOFF AS RELATED

TO CHANNEL GEOMETRY OF SELECTED

STREAMS IN CALIFORNIA

Bv E. R. HEDMAX

ABSTRACT

The channel geometry of 48 gaged streams in California where mean annual runoff is known was studied in 1967 and 1968. The analyses show 

that the mean annual runoff is related to selected dimensions of channel 

geometry. The width and the average depth of the cross section between 

bars or berms can be used to estimate annual runoff from ungaged streams. 

Separate relations are needed for perennial and ephemeral streams. The 

analyses also showed that it is better to measure several cross sections, compute the discharge for each cross section, and average these discharge? to 

obtain the discharge for the site. A 10-year period, 1958-67, was analj'zed 

to determine if the channel dimensions were affected by recent hydrologic 

or climatic events. It was determined that the computed runoff represented 

a long-term mean; that is, the standard error of estimate was less for the 

regression using the runoff for the period of record rather than for the 10- 

year period.

INTRODUCTION

The cost and the length of time required to collect data necessary for hydrologic studies of drainage basins in arid and sMbhumid regions have created the need for other methods for determining runoff. Reconnaissance studies are commonly made to 

provide preliminary estimates, but most studies are based on 

sparse and questionable data concerning precipitation and evapotranspiration. On the basis of some exploratory work, W. B. 

Langbein (written commun., 1966) suggested a method of estimating mean annual runoff based on width and average depth 

of stream channels at point bars in meandering channels, at 

island bars in braided channels, or at berms. These bars rnd 

berms are described by Leopold and Wolman. 1

1 Leopold, L. B., and Wolman, M. G., 1957, River channel patterns: braided, meandering, and 

straight: U.S. Geol. Survey Prof. Paper 282-B, p. 38-85.
E2 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNIT'S) STATES

Moore2 expanded the work of Langbein and developed separate relation curves for ephemeral and perennial streams in 

Nevada. Streams are commonly classed according to types on the 

basis of flow. Perennial streams carry flow at all times, except 

during extreme drought. Intermittent streams carnr flow only 

at certain times during the year when they receive water from 

springs or from surface sources, such as melting snow or ice in 

mountainous areas. Ephemeral streams carry floT^ only after 

periods of precipitation. Because of the lack of adequate data 

concerning flow duration, it was not reasonable to cla ssif y streams 

as intermittent; therefore, in this report all stream'' were classified as perennial if they were flowing and ephemeral if they were 

dry.

This report was prepared by the U.S. Geological Survey, Water 

Resources Division, in cooperation with the California Department of Water Resources. The work was done during 1967 and 

1968 under the general supervision of R. Stanley Lord, district 

chief in charge of water-resources investigations in California, 

and under the immediate supervision of L. C. Dutcher, chief of 

the Garden Grove subdistrict.

STUDY OF CHANNEL GEOMETRY

On the basis of the results of the earlier studies by Langbein 

(written commun., 1966) and Moore,3 the emphasis of this study 

was placed on developing a relation of the unique dimensions of 

width and depth of the channels at bars and bems to annual 

runoff. An alluvial channel adjusts in size to accommodate the 

discharge it receives. Although the channel geometry is influenced by the slope, channel pattern, sediment loads cohesiveness 

of the banks, and vegetation, these studies indicate that the dimensions of the cross sections at the bars and berms are not significantly affected, and that they are related to the annual runoff.

The channel dimensions of 48 gaged streams in the arid and 

subhumid parts of California were studied in 1967 and 1968. 

These streams are listed in table 1. Because these dimensions 

vary greatly in the different cross sections of a stream, as many 

as five sections were surveyed in a reach of charnel about 10 

stream widths in length at each site. Each site wavs chosen near 

the gaging station, so that the drainage area above the site was

2 Moore, D. O., 1968, Estimating mean runoff in ungaged semiarid area1 in Intemat. Assoc. 

Sci. Hydrology Bull., v. 13, no. 1, p. 29-39.

3 Moore, D. O., op. cit.
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E3

about the same as above the gaging stations, and runoff data 

would be available. Measurements were made of width and average depth at each cross section.

TABLE 1. Computed and observed runoff at 48 gaging stations in Califcrnia

[Period of record: e, ephemeral stream; p, perennial stream]

Mean annual runoff

Observed

Station 

No.

Drainage Period Period of

Station name of record

(sq mi) record (acre ft)

10 year Comperiod puted 

(1958-67) (acre- 

(acre-ft) ft)

10-2.W8.8r> San Felipe Creek

near Westmoreland.

2560 __ Whitewater River 

at White Water.

2580 Tahquitz Creek

near Palm Springs.

2585 __ Palm Canyon Creek 

near Palm Springs.

2605 _ Deep Creek near 

Hesperia.

2610 __ West Fork Mojave 

River near 

Hesperia.

11-0315 __ Agua Caliente Creek 

near Warner 

Springs.

0400 __ San Luis Rey River

at Monserate

Narrows, near

Pala. 

0410 __ San Luis Rey River

near Bonsall. 

0424 __ Temecula Creek

near Aguanga. 

0465 __ San Juan Creek

near San Juan

Capistrano. 

0470 _ Arroyo Trahuco near

San Juan

Capistrano. 

0570 __ San Timoteo Creek

near Redlands.

0585 __ East Twin Creek 

near Arrowhead 

Springs.

0586 _ Waterman Canyon 

Creek near 

Arrowhead Springs.

1,693 1960-67 e3,000 ___ 3,660

57.4 1948-67 p9,050 10,210 5,800

16.8 1947-67 e2,290 2,880 3,760

93.3 Zg e2,720 1,300 2,850 

136 | Jg^22 } 1)48,510 36,970 6^,300

74.6 |J9^^2 }p28,020 17,380 41,400 

19.0 1961-67 e573 ___ 805

,7o (1935-41) - 

3 ' 3 11946-67 f e>K490 1.490 5.400

512 * e!3,680 1,790 9,940

131 1957-67 e2,690 2,720 3,050

10(5 1954-67 1)0,660 7,250 17,000

35.7 1930-67 p3,460 3,070 2,290

119 1926-67 el,010 753 1,350

8.80 1919-67 p3.160 2,390 1,630

p1'800 2'080

0 Observed runoff, 13,680, for 1929-67.
E4 CONTRIBUTIONS TO THE HYDROLOGY OP THE UNITED STATES

TABLE 1. Computed and observed runoff at 48 gaging stations in California

Continued

Mean snnual runoff

Observed

Station

No.

0670 __

0734.7.

0780 _.

0845 __

0980 __

1105 __

1130 __

1135 __

1145 __

1160 __

1195 __

1200 

1205 __

1265 __

1284 __

1390 __

1395 __

1430 __

1435 __

1470 __

1476 __

1478 __

Station name

Day Creek near 

Etiwanda.

Cucamonga Creek 

near Upland.

Santa Ana River 

at Santa Ana.

Fish Creek near 

Duarte.

Arroyo Seco near 

Pasadena.

Hopper Creek near 

Piru.

Sespe Creek near 

Fillmore.

Santa Paula Creek 

near Santa Paula.

Matilija Creek 

above Reservoir

near Matilija 

Hot Springs.

North Fork Matilija 

Creek at Matilija 

Hot Springs.

Carpinteria Creek 

near Carpinteria.

Atascadero Creek 

near Goleta.

San Jose Creek near 

Goleta.

Santa Agueda Creek 

near Santa Ynez.

Alisal Creek near 

Solvang.

La Brea Creek near 

Sisquoc.

Tepusquet Creek 

near Sisquoc.

Big Sur River near 

Big Sur.

Salinas River near 

Pozo.

Jack Creek near 

Templeton.

Huerhuero Creek 

near Creston.

Cholane Creek near 

Shandon.

Drainage 

area 

(sq mi)

4.59

10.1

1,685

6.36

16.0

23.6

251

40.0

50.7

15.6

13.1

18.8

5.51

55.8

12.2

93.8

28.6

46.5

74.1

25.3

101

227

Period 

of 

record

1950-67

1927-67

1940-67

1917-67

1910-67

1930-67

1927-67

1927-67

1948-67

(1928-32) 

( 1933-67 J

1941-67

1941-67

1941-67

1940-67

1954-67

1943-67

1943-67

1950-67

1942-67

1949-67

1958-67

1958-67

Period of

p2,610

po,150

elO,50C

p2,870

p6,390

e3,600

p72,40C

p!3,680

1)15,930

p6,530

el,400

e3,26C

pl,17C

e2,37C

e4,200

e3,84C

p89C

1>67,04C

plO,79C

p9,990

el,150

el,67C

10 year 

period 

( 1958-67 

( acre ft )

3,000

4,950

8,270

3,150

5,810

4,130

79,930

15,930

22,150

6,800

1,980

3,530

1,760

3,420

4,660

5,560

1,160

64,500

12,790

10,810

1,140

1,670

Computed 

) (acre2,560

7,000

10,300

4,290

6,430

2,480

47,100

13,200

14,000

7,440

2,130

2,930

2,050

2,840

2,870

3,190

1,450

62,100

12,800

11,800

762

1,440
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E5

TABLE 1. Computed and observed runoff at 48 gaging stations in California

Continued

Mean annual runoff

Observed

Station 

No.

IfiOO __

1615 __

162.") __

1605 __

1760 __

1765 __

1964

1972.5

2245 __

3375 __

45HO __

Station name

Soquel Creek at

Soquel.

Branciforte Creek 

at Santa Cruz.

Pescadero Creek

near Pescadero.

Saratoga Creek

at Saratoga.

Arroyo Mocho near 

Livermore.

Arroyo Valle near 

Livermore.

Caliente Creek

above Tehachapi

Creek, near

Caliente.

Avenal Creek

near Avenal.

Los Gatos Creek

above Nunez Canyon

near Coalinga.

Marsh Creek near

Byron.

Napa River near 

St Helena.

Drainage 

area 

(sq mi)

10.2

17.3

45.!)

9.22

38.2

147

165

57.1

95.8

42.6

81.4

Period Period of 

of record 

record ( acre ft )

1951-67

(1940-431 

(1952-67)

1951-67

1933-67

(1912-30) 

(1963-67)

(1912-30) 

(1957-67)

1961-67

1961-67

1945-67

1953-67

(1929-32 ) 

t 1939-67 )

p31,780

p!4,620

p30,!20

p7,010

p2.980

p22,080

el,050

el,250

e2.1-SO

p5,880

D65.230

10 year Cornperiod puted 

(1958-67) (acre- 

(acre-ft) ft)

29,130

13,090

27,100

5,720

 -

23,220

3.380

6,400

67,620

20,700

11.600

33.500

4,830

3,780

16,600

1,220

1,080

2,010

 S,740

48,500

COLLECTION OF FIELD DATA

The reaches of channel near the gages were reconnoitered to 

locate cross sections with well-defined and consistent reference 

levels for obtaining the required channel dimensions. The bars 

and berms used for the reference level represent the highest 

streambed forms of which particles are subject to annual sediment movement, and the lowest prominent bed forms. The total 

reach of channel used for the survey was inspected to be certain 

that the correct reference levels were chosen. Reference levels 

should all be about the same elevation above the streambed, and 

the bars or berms used to determine the reference levels should
EG CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

continue along- the reach. Figure 1 shows the point bar alongone bank of a perennial stream. The white metallic tape is at 

the reference level. The bars and berms were usually only 0.2-0.6 

foot above the water surface at the low-flow condition in perennial streams and almost level from bank to bank.

Figure 2 shows the reference level defined by bars and berms 

in a channel of an ephemeral stream. For those streams investigated the bars and berms formed by an ephemeral stream were 

often more evident than those formed by a perennial stream.

The bed forms that were the basis of the survey were usually 

related to vegetal zones. Lang-bein (oral commun., 1967) noted 

that in midsummer three vegetal zones can be recognized: (1) 

the in-channel, which is usually free of vegetation; (2) the zone 

between the level defined by the tops of the point and island bars 

and the flood plain, which is usually occupied by annuals (forbs 

and grasses) ; and (3) the true flood plain, which is occupied by 

shrubs, some species of which may be phreatophytes. The bars 

that were used as the reference level in this study were always 

much lower than the flood plain. The crests of the bars alongthe perennial streams were often covered with vegetation, and, 

in some place, the crests were held in place by the vegetation.

FIGURE 1. Point bar along one bank of a perennial stream. White tape is at

reference level.
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E7

FIGURE 2. Bars and berms along one bank of an ephemeral stream. White 

tape is at reference level. Photograph by D. O. Moore.

The reference level was then chosen at the base of the vegetation. 

Figure 3 shows a vegetation line along the right bank and a bar 

on the left bank.

Where pools and riffles existed in the channel, it was necessary 

that cross sections be measured at or near the riffles. The bars 

or berms that were used to determine the reference levels are 

not formed along the edges of the pools, and those that are present will probably give erroneous results.

It was often difficult to locate good reference levels on both 

banks. One bank may be almost vertical. It was also apparent 

from cross sections with bars on both banks that the elevation 

was about the same on both banks for straight reaches of channel. Therefore, good results could also be obtained by stretching 

a level line from a good reference point to the opposite bank.

Manmade structures in the channel, such as bridge piers, gaging-station controls, and lined banks, did not inhibit the formation of the bars or berms, especially if their influence was at 

elevations higher than the reference level. Point bars and berms 

with well-defined reference levels were found just downstream 

from bridges and gaging-station controls. Well-defined point bars 

were also found just downstream from large boulders in the
E8 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

channels as shown in figure 4 a view of a cross section in Taquitz 

Creek near Palm Springs. In figure 4 the white tape is at the 

reference level.

Channel-bed slope and material size appeared to have little 

effect on width and depth of the cross sections between the bars 

or berms. The same relation of these channel dimensions to runoff existed for steep reaches of channel in the mountains to the 

flat slopes of the valley floor. The bed-material size ranged widely 

even from cross section to cross section within the same reach 

of channel. Figure 5 shows the material which forms the point 

bar at section 1 in Arroyo Seco near Pasadena. Figure 6 shows 

much coarser material on the bar at section 3 about 100 feet 

downstream from section 1. The relation of channel dimensions 

to runoff was the same at both sections.

Because the channel dimensions, width and depth, varied 

greatly along the reaches, several cross sections were taken in 

each reach. As many as five cross sections were surveyed if it 

was possible to locate that many independent sections. Sections 

were located one to two stream widths apart, and the reference 

level for each cross section was determined from separate bars 

or berms.

FIGURE 3. Vegetation line on right bank and bar on left bank. View downstream. White tape is at reference level. Photograph by D. 0. Moore.
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E9

FIGURE 4. Well-defined point bar downstream from large boulders in Taquitz 

Creek near Palm Springs. White tape is at reference level. Photograph by 

D. O. Moore.

'¥> '2T«'J5di, v-* I*' X » > - ">:T^ ii^^f^?^^

FIGURE 5. Material forming point bar at section 1 in Arroyo Seco near

Pasadena.
E10 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

A line was stretched tightly across the channel at right angles 

to the thalweg at each cross section for which reference levels 

could be determined. Width was measured between the streamward shoulders of the bars or berms at the reference level. The 

depths were measured from the line to the streambed at about 

20 equidistant points, and the mean depth computed. If the channel was so wide that sag in the line was a factor, a level or transit 

and rod were used. The widths and mean depths at each cross 

section were recorded for the reach of channel. Photographs were 

taken at each cross section for review and, at some cross sections, 

for determination of bed-material size, as shown in figures 5 and 6.

METHOD OF ANALYSIS

Multiple regression was used to obtain the best fit of the variables by an equation of the form:

Y = a + biXj. + b2X2 + b3X3 (1)

where Y is a dependent variable, Xi, X2, and X3 are independent 

variables, a is the regression constant, and b1 , b2, and b3 are regression coefficients.

FIGURE 6. Material forming point bar at section 3 in Arroyo Seco near

Pasadena.
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA Ell

The dependent variable, Y, and the independent variable, X, are 

known data. The regression constant, a, and the regression coefficients, &!, b2, and 63, are constants which are computed with 

the criterion that the sum of the squares of residuals of the relation be minimized. A logarithmic transformation will linearize 

the relations of many hydrologic variables. This transformation 

was done so the resulting equation has the form:

Log Y = log a -j- &! log Xi + 62 log X2 + & 3 log Xa. 

By taking antilogs we obtain the equivalent form:

Y = a,XJ»Xl»Xj». (2)

The calculations involved in solving for the constants are very 

extensive, and therefore have been programed on a digital computer.

All streams were classified as perennial or ephemeral, and 

separate analyses were made for the perennial and ephemeral 

streams using (1) the mean annual runoif for the period of 

record at the gaging station and (2) the mean annual runoif for 

the 10-year period (water years 1958-67, if available) at the 

gaging station. The 10-year period was analyzed to determine if 

channel dimensions were aifected by recent hydrologic everts 

and to have a common base period. The length of record for the 

published mean annual runoif ranged from 6 to 58 years.

PERENNIAL STREAMS

Using width and depth for each cross section as independent 

variables for the 28 perennial streams for the period of record 

gave the smaller standard error of estimate, about 38 percent, 

and the equation:

Qp = 186PF 54 D0-88 (3)

where Qp is runoif in acre-feet per year for perennial streams, 

W is width in feet, and D is depth in feet.

Figure 7 shows equation 3 in graphical form. Either equatior 3 

or the graph can be used for estimating runoif when the width 

and the depth of the cross sections between bars or berms f re 

known. However, neither the equation nor the graph is reliable 

beyond the range of the independent variables, that is, wid% 

6-56 feet, and depth, 0.2-1.3 feet. Table 1 and figure 8 show a 

comparison of the observed runoif, which is published data for 

each gaging station, and the computed runoif from equation 3 

for the 28 perennial streams. The computed runoif was obtaired 

by computing the runoif at each cross section with equation 3 and
E12 CONTRIBUTIONS TO THE HYDROLOGY OP THE UNITED STATES

X u!i 10,000

o t£

i

,'/

*////// '////// v////

W7/77i

W7/7

z

Z2Z

WIDTH, IN FEET

FIGURE 7. Relation of annual runoff to channel width and mean depth for

perennial streams.

taking the average of the cross sections at each gating site. The 

gaging station numbers are given in table 1 and firure 8.

The analyses for the perennial streams using run off for the 10- 

year period 1958-67 showed that the standard error of estimate of 

the computed annual runoff was about 43 percent.

EPHEMERAL STREAMS

Using width and depth for each cross section as independent 

variables for the 20 ephemeral streams for the period of record
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E13

/

/

/

11-

/

11

13

/

 1

15

/

0

>

I 

5 

f

f

11-08

11-17

f""\

/

11

 1

11-0

15^.

iO ^

/

11 

-33

1-11

04

,

5-

60

734.7-^

x-11

 .

 

/

65-

11 

1-

1

J 

/

-0670 

-11-1

-1! -o

^ 

1 

4

 »

y

4

51

135 

70-

7

f

 

^ ^

0

5

10-26

11-11

:y4

/ "*»

-11-09»0

k -10-2560

-11-1605

»-2«VS

11-^431

11-4!

"^

25 

/

. ; 11-11 

1-113 

1-161

./

1-1 

45

i

5

EXPLANATION

11-0585

Station number

s,

 !

CO

/

1-

65

*

6

/

I

11

0

2

2

1130

100 1000 10 000 100.000

OBSERVED RUNOFF, IN ACRE-FEET PER YEAR 

(Period of record)

FIGURE 8. Comparison of observed and computed runoff for perenrial

streams.

gave a standard error of estimate, about 29 percent and the 

equation:

Qe = 258 W°-*° D °-60 (4)

where Qe is ephemeral runoif in acre-feet per year, W is width 

in feet, and D is depth in feet.

Figure 9 shows equation 4 in graphical form. The equation or 

the graph can be used for estimating runoff in ephemeral streams 

when the width and the depth of the cross sections between bars 

or berms are known. However, neither equation 4 nor the graph 

is as reliable beyond the range of the independent variables ur^d 

in the regression, that is, width 10-135 feet, and depth 0.2-1.1 

feet. Figure 10 shows a comparison of the observed runoff, which 

is published data for each gaging station, and the computed 

runoff from equation 4 for the ephemeral streams. The computed
E14 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

runoff was obtained for these ephemeral sites by computing the 

runoff at each cross section with equation 4 and taking the average 

of all cross sections at each gaging site. The gaging station numbers are given in table 1 and figure 10.

In the anlysis of the shorter period of record (1958-67) for the 

ephemeral streams, the standard error 6f estimate of the computed 

mean runoff was about 48 percent.

WIDTH, IN FEET

FIGURE 9. Relation of annual runoff to channel width and mean depth for

ephemeral streams.
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E15

/

1

/

 03

/

15-

/

11- 

.1-

/

11

05 

1!

/

119

70- 

C4-

/

/

10-255

10-2580- 

11-0424-

11-1265 

10-25

~X 

~X 11

/

 ~-il-l'

 \

-d* '

Y

\l 

-11-1 

-1972

78

^

 22' 

78 

5

/

* 

2,

5

11 -0 710

= 17

y[ y -'

X-ii-o

-

i-

-11 

-i 

i13

20- 

1(

r91

21' 

°J

-/.

400

/

0410

/

EXPLANATION

11-147*

Station number

/

/

/

7

2

1000 to ooo 

OBSERVED RUNOFF, IN ACRE-FEET PER YEAR 

(Period of record)

FIGURE 10. Comparison of observed and computed runoff for ephemeral

streams.

REPEATED MEASUREMENTS AT GAGING STATIONS

Two or three visits were made to selected gaging stations following individual storms to see if the results of the measurements 

could be duplicated and if the channel bars retained their relative 

position and size following peak flows. Three series of measurements made at Arroyo Seco near Pasadena and two series at Santa 

Ana River at Santa Ana indicated that measurements could be 

duplicated and that the bars retain their relative position rnd 

size. The results of the computed runoff are given in table 2. The 

peak discharge that occurred between the series of measurements 

and the computed average annual runoff are given in cubic feet 

per second (cfs) to show the relative magnitude of the peak discharge to the average annual runoff.
E16 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

TABLE 2. Results of repeated channel geometry measurements at gaging

stations

Date

1967 

Nov. 17

Do _

Do

Nov. 19

1968 

Jan. 19

Do

Do _ _

Mar. 8

Mar. 21

Do __

1967 

Nov. 18

Do

Nov. 21 __

1968 

Jan. 19 _

Width

(feet)

Arroyo Seco near

_ __ _ 18.5

__ __ 19.0

_ _ 13.0

15.0

15.5

18.0

14.0

_ 24.0

Santa Ana River at

- __ - - _ 135

130

120

Depth P

(feet)

Pasadena

0.36 

.39 

.49

.42 

.38 

.40

.43

.29

, ... Computed eak discharge _ 

, f \ average runoff

(cfs)

(perennial)

> 9.0

1,720

> 8.3 

192

> 9.3

( acre feet )

6,510

6,040

6,730

Santa Ana (ephemeral)

0.72 

.77

.66

I 14.4

1,250 

} 12.8

10,400 

9,300

CONCLUSIONS

These analyses indicate that the best results an obtained by 

computing the runoff using the width and depth between bars 

or berms for each cross section and then averaging the runoff 

for each cross section to determine the runoff for the site. The 

analyses also indicate that the runoff computed f~om measurements of the channel dimensions more nearly represents the 

average annual runoff for longer periods of record. The computed annual runoff for 48 streams studied is given in table 1.

The standard error of estimate for perennial streams (about 

38 percent) and for ephemeral streams (about 29 percent) compared favorably with a study of streamflow generalization in 

the California Central Valley by R. W. Gruff (written commun., 

1966). His study showed a standard error of estimate of 33 percent using drainage area, surface storage index, and mean annual precipitation to compute mean annual discharge for perennial and ephemeral streams. Other methods are also available 

for estimating runoff on ungaged streams usinp climatologic 

or topographic factors, but there is a need for a reconnaissance 

technique based on measurements of the stream itself. Accurate
CHANNEL GEOMETRY OF SELECTED STREAMS IN CALIFORNIA E17

data and good maps are not always available for determiring 

the climatologic and topographic factors, especially in arid and 

semiarid regions. This method meets the need, and the results 

obtained were even better for the ephemeral streams that are 

so common in arid regions than for perennial streams.

 fr U.S. Government Printing Office: 1977 240-961/126