Scour and Fill in Tujunga Wash 

A Faiihead Valley in Urban 

Southern California 1969

> GEOLOGICAL SURVEY PROFESSIONAL PAPER 732-B

1 

I

K Prepared in cooperation with the

e California Department of

$ Water Resources

us

1

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Scour and Fill in Tujunga WashA Fanhead Valley in Urban 

Southern California 1969

By KEVIN M. SCOTT

PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

GEOLOGICAL SURVEY PROFESSIONAL PAPER 732-B

Prepared in cooperation with the 

California Department of 

Water Resources

An analysis of well-documented large and 

destructive changes of a stream channel 

in an urbanized area subject to floods

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1973
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary

GEOLOGICAL SURVEY 

V. E. McKelvey, Director

Library of Congress catalog-card No. 72-600245

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

Washington, D.C. 20402 - Price 70c domestic postpaid or 50c GPO Bookstore

Stock Number 2401-00322
CONTENTS

Abstract. ___________________________________________

Introduction and acknowledgments.____________________

The storms.--__--------__-__________._______________

Precipitation and runoff___________________________

Recurrence intervals of the 1969 floods._____________

The environment-----__-_----_________________-______

Characteristics of the drainage basin________________

Characteristics of Tujunga Wash.__________________

Terrace levels of Tujunga Wash__-_________________

Bed material of Tujunga Wash____________________

Scour and fill- ----_-.----____-__-_______-_-___________

Factors that influence scour and fill in fanhead valleys 

and on alluvial fans____________________________

Changes in water discharge and sediment load___ 

Movement of bed forms and debris flows________

Lateral shift of channel.______________________

Change in channel slope_-_-__-______________-_

Change in base level__________________________

Tectonic effects and long-term aggradation or 

degradation. ______________________________

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Page

Scour and fill Continued

Factors that influence scour and fill in fanhead valleys 

and on alluvial fans Continued 

Manmade changes__________________________ BIO

Methods of study photogrammetric determination of 

scour and fill. _____________________________________ 10

Types and accuracy of photogrammetric mapping. _ _ _ 10 

Construction of cross sections- _____________________ 11

Scour and fill in Tujunga Wash-_--___-____-___________ 11

Scour and fill portrayed on cross sections.___________ 11

Summary and conclusions.____________________________ 25

Flow diverted to distributary channel_____________ 25

Vertical scour due to local reduction in base level- _ _ _ 25 

Lateral scour of terraces._________________________ 27

Changes in longitudinal profiles ____________________ 27

Photogrammetric methods applied to the determination of scour and fill.___________________________ 28

Application of results_____-__-__-_______-_____---_ 28

References cited___________--___-__-____-___--_---__ 28

ILLUSTRATIONS

FIGURE 1. Index map of study area_______________.__________________________________________________________________

2. Longitudinal profile of Tujunga Creek______________________-_____________________. ________________________

3. Map of Tujunga Wash showing limits of urbanization and location of cross sections..______-________-__--_----__

4. Photograph showing view looking upstream along the south channel of Tujunga Wash._________________________

5. Longitudinal profiles of the main channels of Tujunga Wash._-_______-__-_____________-___-__-_------_-_---_

6. Sections A-A', B-B', and C-C', Tujunga Wash_______________________________-_-__-_____-____.._-_-_----_-

7. Sections D-D' and E-E', Tujunga Wash__----_________-____-______-___-___--__-_-_--___-__--_----------__-

8. Photograph showing inundation along south channel of Tujunga Wash, February 25, 1969_______________________

9. Sections F-F' and G-G', Tujunga Wash,.. _____-______________________-_.-_____-___---_-------_---_-_----_-

10. Sections H-H' and /-/', Tujunga Wash.....__._._______.._____________._.___._______________-. --_-_..._

11. Sections J-J' and K-K', Tujunga Wash.______.-____________--__--________-_________-_-____----_-_-_------

12. Photograph of south channel of Tujunga Wash showing destruction of the south-channel Foothill Boulevard bridge. _

13. Sections L-L' and M-M', Tujunga Wash_________________._____________._______-..________-___-__---_.--__

14. Photograph showing view looking northwest of what remained of the Bengal Street terrace after February 25 flood 

	peak.-_---____---_______________________________________________________________--__-_.._--_------_

15. Section N-N', Tujunga Wash.______________________________________________-__-__--____-__--------_----_

16. Sections O-O' and P-P', Tujunga Wash. _________________.__...._______.________-_._.._-.._.-_.._.-_ _.__

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TABLE

TABLE 1. Summary of flood discharges at gaging stations in Tujunga Creek drainagePage 

B3

ill

PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

SCOUR AND FILL IN TUJUNGA WASH A FANHEAD 

VALLEY IN URBAN SOUTHERN CALIFORNIA 1969

By KEVIN M. SCOTT

ABSTRACT

A unique combination of substantial channel change and documentation of the changes by high-order photogrammetry was 

studied in Tujunga Wash in southern California. Extensive scour 

and fill occurred during the recordbreaking 1969 floods in this 

3-mile-long, partly urbanized fanhead valley. Maxima of 20 ±2 

feet of net scour and 35±2 feet of net fill were measured on 31,000 

scale-feet of cross sections plotted to illustrate changes in distributary channels of the wash. Net elevation change of the channel 

thalweg varied from as much as 14 ±2 feet of scour to as much as 

16 ±2 feet of fill.

The most dramatic causes of scour and fill in Tujunga Wash 

were (1) the unexpected yet possibly natural diversion of floodflow to a major distributary channel of the wash in which urbanization had progressed, (2) local reduction in base level which 

occurred when floodflow in both of the main distributary channels 

entered a large gravel pit, and (3) lateral scour of an aggradational 

surface within the wash because of natural adjustment of a distributary channel to flood discharge. Additional scour and fill 

were due to locally raised base level and to the natural lateral 

shift characteristic of channels in the broad, ephemeral washes of 

arid and semiarid regions.

Scour proceeded upstream from the edge of the gravel pit probably as much as 3,000 feet and was instrumental in the failure of 

three highway bridges. An entire residential street and seven homes 

built on an unstabilized cutback of the channel were destroyed 

by lateral scour. Damage at most, if not all, of the localities could 

be indirectly ascribed to man's disregard of natural geomorphic 

processes on alluvial fans and in fanhead valleys.

The textural similarity of the bed material of the active channels 

and the deposits exposed within the wash by the 1969 floods suggests that all the deposits were formed under the present, or a 

similar, hydrologic regime. Thus, rapid lateral shifts of channel 

position as a result of major floods should not be unexpected anywhere in the wash. During long intervals of dry weather, however, 

the memories of previous flood disasters become dim, and building 

sites in the washes and on bordering terraces prove irresistible 

to developers and home buyers. Urban development on the unstabilized cutbank of a natural flood channel on an alluvial fan 

or fanhead valley is generally a poor risk.

Comparing preflood and postflood profiles downstream from the 

point of a fanhead jump, it is apparent that channel diversion 

locally resulted in scour of one major channel which corresponded 

in amount with fill in the other major channel. Not only were scour 

and fill comparable in amount, but the postflood profiles of both

channels became nearly parallel, after smoothing of pronounced 

preflood irregularities in the channel which were both natural 

and the result of the works of man. Analogies with mechanisms 

active in the maintenance of a long-term equilibrium in the formation of alluvial fans are possible.

Analysis of the photogrammetric data indicated that accuracy 

of design mapping (contour interval, 2 feet; scale, 1: 600) is sufficient to define net changes in scour and fill throughout a flood 

course, in parts of the channels to the nearest foot of elevation. 

Detection of minor gullying outside the main distributary channels 

was possible on low slopes.

INTRODUCTION AND ACKNOWLEDGMENTS

Many urban areas in southern California are bounded 

by rugged mountain ranges. Streams draining the 

mountains flow initially through steep bedrock channels, then debouch during floods from the steep fronts 

of the ranges to rapidly deposit debris on broad, semicircular cones known as alluvial fans.

Streams that drain the frontal watersheds of the 

San Gabriel and San Bernardino Mountains form 

alluvial fans directly at the mountain front. Larger 

streams that drain the interior of the mountain ranges, 

although confined to deep V-shaped canyons throughout much of their courses, make the final 1-5 miles of 

their departure from the mountain front through broad, 

expanding valleys hydrologically similar to the pieshaped segment of a fan. These valleys, here described 

as fanhead valleys, are the intermountain extensions 

of fan alluviation. Such upper fan embayments also 

have been described as fanbay areas which, however, 

are generally features of a smaller scale.

In their natural state, channels both on the fans and 

in the fanhead valleys are unstable washes like those 

of desert regions ephemeral and capable of shifting 

rapidly in response to changes in flow.

It was on the fans, particularly in fanhead areas, 

where stream processes were most active and where 

the greater part of the damage caused by the recordbreaking floods of January and February 1969 was

Bl
B2 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

concentrated. It was also on the upper parts of the fans 

where the conflict between urbanization and the 

natural environment was most dramatically illustrated. 

Such areas are often the last land available in southern 

California in a pattern of urbanization moving upward 

from the level land of the basins toward the mountain 

front. Individual flood-control facilities for every 

major fan-forming drainage have not kept pace with 

urban development. Well-planned flood-control facilities in older developed sections held damage to a minimum in basin areas and on most of those fans where 

facilities were complete.

Several indirect factors contribute to the local 

destructive intensity of floods in southern California. 

One is the ephemeral nature of stream channels on 

fans and in fanhead valleys. Little or no surface flow 

occurs during most of the year, and in many years 

storm runoff is of small magnitude and short duration. 

During the long intervals of dry weather, memories 

of previous flood disasters become dim, and building 

sites in the washes and on bordering terraces prove 

irresistible to developers and home buyers. This 

problem was magnified by a prolonged dry period, 

lasting from the mid-1940's to 1965, that coincided 

with a time when the population of southern California multiplied explosively. In addition, urban 

planners have not been uniformly cognizant of the 

geomorphic setting and the nature of floodflows on 

alluvial fans. At the heart of this aspect of the problem, 

as noted by Rantz (1970), is the lack of a direct central 

planning authority to exercise uniform control over 

the 78 municipalities that exist in Los Angeles County 

alone.

The problem of flooding on fans generally was not 

one simply of damage from rising flood waters; rather, 

it was largely one of rapid lateral shift in channel position, either by erosion of the banks of stream terraces 

supporting structures seemingly safe from the greatest 

flood or by the seemingly random jump of the flow to 

old or completely new channels radiating from the fan 

apex. Property destruction from this cause occurred 

on fans throughout southern California in 1969.

This report treats an example of flood effects on both 

channel morphology and the activities of man in a 

fanhead valley Tujunga Wash (fig. 1). The purpose 

of the study is to (1) provde urban planners with a 

case history of the changes in channel morphology in a 

fan environment; (2) analyze these changes in terms 

of scour and fill; (3) indicate the causes of scour and 

fill wherever possible; and (4) show how high-order 

photogrammetry can detect such channel changes. 

The circumstances connected with scour and fill in 

Tujunga Wash are examples that apply in principle to

innumerable other fanhead valleys that may become 

urbanized in a similar manner throughout the Southwestern United States.

The changes in Tujunga Wash were of two general 

kinds: changes that would have occurred under natural 

conditions, and changes that were interrelated with 

human modification of the channel. In the first, if 

destruction in similar geomorphic settings is to be 

avoided in the future, planners must appreciate the 

potential magnitude of the natural changes the way 

in which ephemeral fan channels adjust to changing 

flow conditions before making zoning decisions. Secondly, with knowledge of the harmful effects of a few 

of man's activities in the channels, control of such 

activities must be exercised, or compensating protective measures planned in the event of economic 

justification.

The study was made in cooperation with the California Department of Water Resources. Agencies that 

provided information are acknowledged in the body of 

the report; individuals who provided assistance are too 

numerous to mention, but lack of space does not reflect the lack of the author's gratitude.

THE STORMS

PRECIPITATION AND RUNOFF

The storms of late January and late February 1969 

caused floods approaching or exceeding the previous 

flows of record at many localities (Waananen, 1969). 

Moist tropical air moved strongly out of the Pacific 

as a series of storms during the periods January 18-22, 

January 24-27, and February 22-25. The pattern of 

precipitation for the February storm, which caused the 

greatest damage in Tujunga Wash, is shown in figure 1.

Distribution of rainfall in the upstream drainage 

basin of Tujunga Creek generally was similar in the 

January 18-22 and February 22-25 periods. During 

the January 24-27 storm, greater quantities of precipitation, 18-20 inches, fell in the central part of the basin 

near Big Tujunga Reservoir. Totals for the January 

18-22 and February 22-25 storms ranged from 12 to 

14 inches in the same area. Precipitation during 

February maintained saturated-soil conditions that 

permitted the runoff from the storm of February 22-25 

to compare with that of the more intense storm of 

January 24-27.

The January 1969 floods in southern California were 

comparable to those of March 1938, the greatest since 

the legendary flooding of 1862. This was not true in 

the Tujunga Canyon area, however, where peak discharges were less than in 1938 (table 1), in part because 

the 1938 storm was unusually intense in the Tujunga
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B3

M T S /"^V \ -^-. ' yyPacifico X Mtn

Ephemeral drainage 

Drainage-basin boundary

Mountain- front boundary

Line of equal rainfall, in 

inches, for storm period 

February 22-25, 1969

Stream-gaging station

DRAINAGE AREAS

1. Tujunga Creek above mountain-front 115 sq mi

2. Tujunga Creek above Sunland (gaging station 

11-0955)-106 sq mi

3. Tujunga Creek above Big Tujunga Dam 81.4 sq mi

4. Tujunga Creek above Mill Creek, near Colby Ranch 

(gaging station 11-0940) 64.9 sq mi

FIGURE 1. Index map of study area. The stream-gaging stations shown are operated by the Los Angeles County Flood-Control 

District. Isohyetals compiled by the Los Angeles County Flood-Control District.

Creek watershed. Although renewed flooding in February 1969 produced peak discharges in Tujunga Creek 

comparable to those of January (table 1), the February 

flows proved to be more devastating in their effects on 

urbanization in the area studied because of factors 

described below.

Values of peak discharges through Tujunga Wash are 

not well defined. Maximum mean hourly inflow into 

Hansen Flood-Control Basin (fig. 1) during the February storm period was 26,000 cfs (cubic feet per second) 

from 0700 to 0800 hours on February 25 (Simpson, 

1969b, pi. 86). Inflow from an additional drainage area 

of 21 square miles is included in this figure. Discharge 

in the wash is estimated to have reached a maximum 

of more than 17,000 cfs during the predawn hours of 

February 25 (Simpson, 1969a, p. 40).

TABLE 1. Summary of flood discharges at gaging stations in 

Tujunga Creek drainage

Stream and 

Station place of 

No. determination

Drainage

area 

(square 

miles)

Period

of 

record

Maximum 

discharges

Date

Cfs

Recurrence

interval

(ratio to

50-year

flood)

11-0940. Tujunga

Creek below Mill

Creek, near

64.9 1948-69 1-23-43

12-29-65

1-25-69

2-25-69

i 14,800

6,550

12,900

13,500

1.2

.42

1.02

1.1

Colby 

Ranch. 

11-0955. Tujunga

Creek near 

Sunland.

106 1916-69 3- 2-38 *.3 50,GfoO

1-25-69 3 20-, 600

2-25-69 320,000

2.6 

1.1 

1.05

> Exceeded by March 1938 flood. Peak inflow to Big Tujunga Reservoir (drainage 

area 81.4 sq mi) 35,000 cfs, Mar. 2, 1938.

2 Estimated.

3 Affected by storage in Big Tujunga Reservoir (constructed 1931).
B4 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

RECURRENCE INTERVALS OF THE 1969 FLOODS

A perspective of the relative significance of the 1969 

floods in the Tujunga Creek basin is indicated by their 

recurrence intervals the number of years, on the average, in which a given peak flow will be equaled or 

exceeded once by the annual peak discharge. A 50-year 

flood, for example, has one chance in 50 of being equaled 

or exceeded in any one year. Such a flood need not recur 

only once every 50 years; because of the irregularity of 

climatic trends, it could occur several times in a shorter 

time interval.

The recurrence intervals of peak discharges on both 

January 25 and February 25 were slightly in excess of 

50 years at both the upstream station, Tujunga Creek 

below Mill Creek, near Colby Ranch, and at the station 

only 3 miles above the canyon mouth, Tujunga Creek 

near Sunland (table 1). The back-to-back occurrence 

of two 50-year floods in the basin does not lengthen 

the odds against another major flood in the near future, 

however.

THE ENVIRONMENT 

CHARACTERISTICS OF THE DRAINAGE BASIN

Tujunga Creek above the mountain front drains 

115 square miles of the western San Gabriel Mountains. 

Big Tujunga Flood-Control Reservoir (fig. 1) acts as 

catchment for 71 percent of the basin, but its capacity is 

small (3,819 acre-ft in 1966) in relation to its drainage 

area (81.4 sq mi). Large flows, such as those of January 

and February 1969, may pass the spillway only slightly 

attenuated.

The area is one of normally erosion-resistant rocks 

which, because of geologically recent faulting and 

fracturing, supply large quantities of debris to drainage 

courses through processes of mass movement, as well 

as normal runoff-erosion mechanisms. Annual debris 

yields to Big Tujunga Reservoir, in 39 seasons (1930- 

31 to and including 1968-69), have averaged 2,500 

cu yd per sq mi per yr (cubic yards per square mile 

per year), or 1.56 acre-ft per sq mi per yr. Debris inflow 

between October 1966 and March 1969 was 7,550 

cu yd per sq mi per yr, or 4.68 acre-ft per sq mi per yr. 

Most of the debris represented by the 1966-69 figure 

was deposited during the 1969 storms.

Geologically recent uplift of the basin is indicated 

by steep, dissected slopes, which average 40 percent 

throughout the watershed, and convexity in parts of 

the stream profile (fig. 2). Other explanations of a 

convex profile are possible, but the nearness of a convexity to the range front suggests that change of base 

level by uplift relative to the San Fernando Valley is 

the most probable cause. The rift zone of the San 

Gabriel fault, a major lateral-slip fault with many 

miles of displacement, controls the stream-channel

0 5 10 15 20 25 

MILES ABOVE HANSEN FLOOD-CONTROL BASIN

FIGURE 2. Longitudinal profile of Tujunga Creek.

alinement in the northwest-southwest reaches upstream from the gaging station, Tujunga Creek near 

Sunland. Relative uplift of the upper part of the basin 

may have been accompanied by lateral movement on 

this fault. The continuing nature of tectonic activity in 

the watershed was illustrated by the major earthquake 

of February 9, 1971, during which as much as 4 feet of 

vertical displacement occurred along a faultline of 

thrusting at the north side of Tujunga Wash.

Basin relief is more than 5,000 feet, ranging from 

elevations of 7,124 feet at the summit of Pacifico 

Mountain to 1,290 feet where Tujunga Creek leaves 

the mountain front and enters Tujunga Wash. Valleys 

are V-shaped, except for parts of the main channel in 

which bedrock constrictions have acted as natural 

debris dams to form flat areas of alluviation. The 

average slope of the main channel over most of its 

25-mile course is 135 feet per mile.

Hillslopes throughout the basin are covered with a 

dwarf forest of chaparral, an association of xerophytic 

shrubs and stunted tree forms that reflect the semiarid, 

Mediterranean climatic pattern one of summer 

drought and winter rains. Such vegetation is highly 

inflammable during the dry season. Loss of watershed 

cover by fire can greatly increase runoff and erosion 

in the basin, but this was not a factor in 1969.

CHARACTERISTICS OF TUJUNGA WASH

Downstream from the mountain canyon Tujunga 

Creek enters a reach, Tujunga Wash, which can best 

be described as a fanhead valley (fig. 3). The contrast 

with the mountain canyon is sharp. When viewed from 

the air, the wash appears as a sinuous white ribbon of 

coarse alluvium poured from the mountain front, and 

is the most striking physiographic feature in San Fernando Valley. The wash forms the floor of Tujunga 

Valley and is 3 miles long and half a mile wide in the 

interval before surface flows reach the spillway eleva-
Approximate limits of urbanization 

at time of flood

Thalweg of preflood 

low-water channel

Line of cross section CONTOUR INTERVAL 20 FEET ON VALLEY FLOOR

40 FEET ON VALLEY-SIDE SLOPES

DATUM IS MEAN SEA LEVEL

FIGURES. Limits of urbanization and location of cross sections of channels in Tujunga^Wash. Cross sections are shown in figures 6, 7, 9, 10, 11, 

is from U.S. Geological Survey 1:24,000 quadrangle map (Sunland quadrangle) and is riot comparable with elevation data used to p
B6 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

tion of the Hansen Flood-Control Basin. It was in this 

reach that large quantities of scour and fill occurred, 

and along which property damage was most severe.

Tujunga Wash is a complex of active and abandoned 

channels. It resembles an alluvial fan in that it likewise 

is an alluvial fill formed by deposition from a stream 

whose competence is suddenly reduced as it leaves the 

confining reaches of its mountain course. Rather than 

an abrupt change in slope of the channel where it 

meets the fan apex, it is the change in hydraulic factors 

associated with flow through noncohesive materials an 

increase in width and a decrease in depth of flow 

that generally causes deposition of debris on fans and 

in fanhead valleys such as Tujunga Wash. Infiltration of 

flow in permeable valley deposits is an additional factor 

which causes the concentration of deposition in fanshaped loci at mountain fronts.

The stream channel of Tujunga Wash in an unmodified state is free to migrate laterally through bed 

material of boulder gravel, but only floodflows have the 

competence to transport material of that size. The main 

active channel on the north side of the wash (fig. 3) has a 

nearly constant slope marked by small irregularities, 

both natural and man-made. A second, historically 

less-active, major channel branches from the main 

channel at the mountain front and runs along the south 

side of the wash. As on an alluvial fan or delta, the 

tendency is one of formation of distributaries at the 

point where flow leaves the mountain front, but in 

Tujunga Wash this tendency is restricted by the bedrock side slopes of Tujunga Valley.

The channels, though typical of ephemeral desert 

washes, do not readily fit the systems of channel 

nomenclature that were developed in humid regions. 

Channel patterns include a spectrum of types, depending on flow regime. At low flow each sand-floored 

distributary meanders in a bar-braided pattern with 

low sinuosity (less than 1.3) within its individual wash. 

Little lateral cutting of the boulder-gravel banks takes 

place. Pools and riffles are not well defined by bed relief. Features possibly analogous to riffles appear 

during periods of no flow as concentrations of boulders 

spaced at regular intervals along the channel (Leopold, 

Emmett, and Myrick, 1966, p. 207); similarly, features 

that may correspond to pools are seen as sand-covered 

reaches underlain by gravel apparently less coarse than 

that in the rifflles. At high discharges (fig. 4), flow fills 

the main drainage courses, and the flow pattern becomes complexly braided with multiple bars. Rapid 

lateral shift of individual channels is common, although, 

during the floodflows of 1969, this occurred within the 

confines of the two large-scale braided channels discussed above.

TERRACE LEVELS OF TUJUNGA WASH

The most widespread of the depositional surfaces 

in Tujunga Valley is the central floor of Tujunga Wash 

into which the present natural channels have been 

entrenched, to a preflood depth of 8-10 feet near the 

Foothill Boulevard crossing. This surface is similar to 

that of undissected alluvial fans elsewhere in southern 

California undulating, broadly convex upward in 

lateral profile, covered with mature desert vegetation. 

It is the most conspicuous surface on each side of the 

valley and is that upon which urbanization has encroached most extensively. The preflood location of 

the destroyed Bengal Street (fig. 3) was on this surface.

Other terraces observed were a level sporadically 

present 7-8 feet above the channel on the south side 

of the wash, and two higher levels, one 10-15 feet and 

another 70-90 feet above the natural channel along 

the north side of Tujunga Valley. The lower o* the latter 

two levels has been extensively urbanized; the higher 

is an old surface, also aggradational, grading to a former, 

higher level of valley fill.

BED MATERIAL OF TUJUNGA WASH

The gravel underlying the most widespread surface 

of the wash is similar in all sedimentological respects 

to the bed material of the channels. There was no significant difference in the size distributions of four 

samples of material underlying the main surface and 

five samples of bed material from the active channels. 

All samples were boulder gravel of bimodal distribution with the primary mode in the phi-classes 6.0 to

-7.0 (64-128 mm) or -7.0 to -8.0 (128-256 mm). 1 

Mean size of the samples ranged from phi values of

 5.3 to 6.6 (40-100 mm). Sorting, nearly equivalent 

to standard deviation of the size distribution, was 

between 1.8 and 2.5 phi units, ranges commonly 

characterized as poorly sorted.

It is clear, considering the similarity in size distributions, that all the deposits exposed within the wash 

were formed under the present, or a similar, hydrologic 

regime. The significance of this conclusion is that there 

is no basis for assuming that any part of the main 

depositional surface of Tujunga Wash, because of 

greater coarseness of material, is immune to destruction 

by lateral shift of the channels. As noted above, it was 

this main depositional surface upon which new urbanization was progressing most rapidly prior to the 

1969 flooding.

SCOUR AND FILL

Scour as discussed in this report is the removal of 

sediment from the channel and overbank areas of a 

stream by the action of fluid flow, virtually the defi1 The phi (0) grade scale may be compared with size in millimeters by the relation, mm = ^*.
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B7
B8 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

nition of Culbertson, Young, and Brice (1967, p. 1). 

Conversely, fill is the deposition of material on bed 

or banks.

The connotation of scour is related to the method of 

measurement. For example, scour recorded by scour 

chains or ribbons buried vertically in a bed is the maximum depth of dilation of the grain bed during a flood. 

The net amount of scour, determined from preflood 

and postflood surveys of Tujunga Wash, is not the 

maximum depth of scour that existed in much of the 

wash during passage of the 1969 flood peaks. However, 

the large magnitude of channel changes in Tujunga 

Wash as well as the extreme coarseness of the bed 

material precluded study with scour chains. Values of 

scour and fill as measured by means of preflood and 

postflood surveys are the net subtraction or addition, 

respectively, of sediment on the valley floor.

The following summary of the causes of scour and 

fill is not comprehensive but includes the dominant 

processes that account for most scour and fill in ephemeral streams. It describes those processes most active 

in fanhead valleys and on alluvial fans.

FACTORS THAT INFLUENCE SCOUR AND FILL 

IN FANHEAD VALLEYS AND ON ALLUVIAL FANS

CHANGES IN WATER DISCHARGE AND SEDIMENT LOAD

The flow of water and sediment in alluvial channels 

is complex and involves the mutual adjustment of a 

number of variables water discharge, sediment discharge, size of bed material, the fall velocity of a characteristic sediment particle, width, depth, velocity, 

slope, and a characteristic of the pattern of streamflow 

(Haddock, 1969).

The adjustment of channels to changes in flow variables can be partly illustrated by the channel changes 

that accompany the passage of a flood. Width, mean 

depth, and mean velocity each increase as power 

functions with increasing discharge at a cross section, 

part of the set of relations described as the hydraulic 

geometry of .channels by Leopold and Haddock (1953). 

Shear stress on the bed increases, and sediment is 

scoured. If a large debris load is introduced on the rising 

stage, however, deposition may occur, associated with 

a decrease in flow resistance, or roughness, a change in 

bed form, and a reduction in depth. On the falling stage, 

competence of the flow to transport sediment is reduced, 

and fill generally occurs, most commonly back to the 

same or a similar level as that which existed before the 

flood. Similarly, temporary episodes of scour, also 

related to changes in debris load, and contrary to the 

trend toward fill, are possible on the falling stage.

Few studies have been able to define the variation 

in scour and fill due to change in flow factors longitudinally along a stream. In general, the ephemeral 

channels of semiarid areas have been found to scour

temporarily during floods (Leopold, Wolman, and 

Hiller, 1964, p. 235). Lane and Borland (1954) concluded, from sediment yield to a reservoir, that the 

substantial scour in a few cross sections must be 

balanced by fill elsewhere in the same section of channel. 

Studies of perennial streams in humid areas suggest that 

scour and fill alternate in certain reaches.

MOVEMENT OF BED FORMS AND DEBRIS FLOWS

Large-scale gravel waves representing either dune 

forms or the snouts of debris flows were associated 

with 1969 flood discharges in other canyons along the 

front of the San Gabriel Hountains. Cessation in movement of concentrations of gravel formed by either 

process caused substantial quantities of fill at points 

along some expanding reaches. In Tujunga Wash and 

other large drainages the receding stages of water 

discharge were sufficiently prolonged to destroy dune 

forms characteristic of a high flow regime.

No gravel dunes or debris-flow snouts were visible 

during field inspection of all reaches of Tujunga Wash. 

Dune movement doubtless occurred during the peak 

flows, however, and caused small, temporary quantities 

of scour and fill.

LATERAL SHIFT OF CHANNEL

The position of the type of channel found on alluvial 

fans may change either by sudden redirection, or jump, 

of the flow, such as when distributaries form at the 

fan apex, or by the lateral migration of a single channel 

that will occur under constant flow conditions in most 

channels formed in noncohesive materials. In truly 

braided flow, the multiple channels are subject to 

continuous shift and splitting. Huch the same mechanism is responsible for the major changes in direction 

that occur at the apex of a fan or fanhead valley when 

the bedrock-confined flow first enters an environment 

where flow is unconfined and bed material is noncohesive. Fahnestock (1959) illustrated the manner in 

which braided streams flowing through glacial-outwash 

debris change their channels: As flow increases the 

channel widens and in some places depth decreases, 

until competency is not sufficient to transport bed 

material; a bar is then formed, commonly near the 

middle of the channel, and flow divides into two channels. This process is repeated as flow increases and the 

channels anastomose in the constantly changing pattern characteristic of braided flow. Figure 4 shows the 

major division of flow that occurred near the apex of 

Tujunga Valley, top-center part of photograph, and 

the anastomosing of braided flow in the south channel, 

left of center.

The thalweg of alluvial channels may undergo lateral 

shift without a similar shift in overall channel position. 

In humid-region streams, this shift commonly is tern-
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B9

porary during high discharges. In ephemeral washes, 

the changes are greater and are more likely to survive 

the runoff event.

CHANGE IN CHANNEL SLOPE

A major channel shift in a fanhead valley or on an 

alluvial fan is commonly associated with a change in 

slope. Diversion of the channel at a fan apex is generally 

to a radial path with a steeper slope, temporarily increasing the ability of the stream to scour. However, 

over a longer interval, deposition will build on the new 

segment of the fan until another channel shift occurs 

along a path of greater slope. It is this occasional shifting of the watercourse and the locus of deposition at 

the fan apex that gives the alluvial fan its symmetrical, 

conical form. Such change is a natural, expectable 

phenomenon.

CHANGE IN BASE LEVEL

The level of the body of water into which a stream 

flows, its base level, affects the gradient of the stream 

channel. If the base level of a stream changes, scour or 

fill is induced in the channel upstream from the new 

base level.

If a new and higher base level is introduced, by construction of a dam, for example, fill will occur throughout a length of the upstream reach. The distance to 

which fill will extend in such a case cannot be well 

defined and varies for different types of streams; 

Leopold, Wolman, and Miller (1964, table 7-6) 

reviewed a number of case histories. In general, introduced base levels affect only limited sections of upstream reaches. A similar, unknown degree of fill could 

be expected to have occurred in Tujunga Wash above 

the Hansen Flood-Control Basin (fig. 1).

A reduction in base level, on the other hand, will 

increase the erosive ability of a stream through increase 

in gradient. A steep headcut formed at the point of 

lowered base level may move upstream, commonly 

flattening with time and extending the increase in 

slope over a greater length of channel. Such a lowered 

base level occurred in Tujunga Wash when floodflows 

from both main channels poured into a large gravel 

pit (fig. 3).

TECTONIC EFFECTS AND LONG-TERM AGGRADATION 

OR DEGRADATION

If there is a trend toward fill lasting over a period of 

years, the change represents aggradation; if the change 

is one of net long-term scour, it is called degradation.

Plainly, the fan or fanhead valley itself is the site of 

net aggradation over geologic intervals at the same time 

the channels of the watershed that supply the sediment 

to the fan are being degraded. Periods of aggradation 

and degradation can affect channels in both geomorphic 

settings, however, generally because of climatic and

human effects on the hydrologic regimen of the drainage 

basin. The trend of the changes at present is helpful 

in the practical considerations of scour and fill bridge 

siting and design, lined-channel construction, allowance 

for sediment supply in the design of impoundments, 

to name a few.

In southern California the picture is complicated by 

tectonic changes raising or lowering of the mountain 

masses relative to the depositional areas. Uplift, geologically recent and continuing at present in some areas, 

has greatly increased the sediment supply and rate of 

fan construction along the fronts of many ranges, 

including the San Gabriel Mountains. The effect is that 

of lowering the base level or locally increasing the slope 

of the stream channel within the mountains.

Yet another factor to consider in the interpretation 

of available data is the difference in effects on channels 

of a large floodflow as opposed to a period of low and 

moderate flows. A single catastrophic flood in California 

streams often has resulted in extensive fill in most areas 

(Stewart and LaMarche, 1967; Scott and Gravlee, 

1968), followed by degradation during successive periods 

of lower flows if discharges remain sufficient to transport bed material deposited by the flood. Unfortunately, 

it is exceedingly difficult to generalize on this subject 

because of the other variables that affect scour and 

fill.

In few places is there more topographic diversity to 

affect the variables controlling scour and fill than in 

southern California. Consequently, it is not surprising 

that an unpublished survey of 1968-69 changes in 

streambed elevations at gaging stations in the region 

by R. P. Williams of the Geological Survey showed no 

significant overall trend toward either scour or fill. 

Study of Williams' data with reference to physiographic 

position of the gaging stations showed a probably 

significant trend toward aggradation in settings similar 

to Tujunga Wash.

Differences in long-term trends of scour and fill, 

that is, aggradation or degradation, on parts of the 

same river system in southern California are illustrated 

by the channel of the Santa Ana River prior to the 

construction of major dams. At the station Santa Ana 

River near Mentone, in a fanhead reach, fill occurred 

during, and for years previous to, the major flood of 

1938. Downstream, at the station Santa Ana River 

near Prado, scour occurred progressively over the same 

period (Troxell and others, 1942, fig. 40). Firm conclusions obviously cannot be based on data from single 

stations. Every study of scour and fill based on cross 

sections at gaging station sites must note that such 

locations are likely to be unrepresentative of the stream 

as a whole. And, even though a trend toward scour or 

fill may be recorded at a particular section for years,
BIO PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

there is no assurance that the trend will continue, 

or that it could not be reversed in the future.

More uniform results were presented by Hickey 

(1969) for gaging-station sites in coastal northern 

California, an area more humid and less physiographically diverse than southern California. Streambedelevation changes at 42 of 51 sites represented fill in 

response to the 1964 flood, the largest of record at most 

stations in that region. No regional trends toward 

aggradation or degradation were evident from yearly 

measurements during the periods of record at the 

stations.

There can be little doubt, however, that trends toward both aggradation and degradation are occurring 

in streams in southern California. Regionally, the area 

shows evidence of what may be the same long-term 

alluviation noted by Leopold, Emmett, and Myrick 

(1966, p. 194) in the Southwest. Also, as in the Southwest, deposits of this period of alluviation are now 

undergoing dissection in southern California.

MANMADE CHANGES

Most of the above causes of scour and fill can be 

related to the works of man, and, as will be seen below, 

this was true of many of the channel changes in Tujunga 

Wash.

Not previously discussed were the effects of manmade obstacles, such as bridge piers and constrictions 

of the channel. Culbertson, Young, and Brice (1967) 

summarized the effects of construction of river structures on channels, generally those of humid regions, 

and the principles clearly extend to the ephemeral 

channels of semiarid areas.

A specific aspect is the effect of a dam on the downstream channel. One common effect of a reservoir is 

to reduce flood discharges, increase base flow, and, by 

trapping most sediment, cause the release of clearwater flows downstream. With the change in discharge 

and change in sediment load relative to discharge, the 

downstream channel is scoured and may change its 

cross-sectional configuration. Or, fill may occur in response to large sediment contributions from tributaries, 

increased vegetation due to reduction of peak discharges, or approximately uniform releases. The effects 

of Big Tujunga Flood-Control Reservoir (fig. 1) on 

the morphology of Tujunga Wash expectably are 

minor because of the small capacity of the reservoir 

and the channel distance between the dam and the 

mountain front that allows the sediment load of floodflows to readjust to discharge.

METHODS OF STUDY PHOTOGRAMMETRIC 

DETERMINATION OF SCOUR AND FILL

A study of scour and fill in Tujunga Wash was 

possible because of the unique combination of largemagnitude channel changes and the availability of 

high-order photogrammetry. Preflood and postflood 

photogrammetry of nearly the entire reach of interest 

was included in four sets of maps: two derived from 

aerial photography before both floods and two from 

photography flown within a short time after the February flood.

The photography was flown on the following dates, 

and maps were constructed with the following scales 

and contour intervals:

Date of 

photography

Scale of map

Contour

interval

of map

(feet)

Source

Preflood

9-13-66__-_._- 1 in. = 100 ft 

(1:1,200)

6-10-68.______ lin.= 50ft

(1:600)

Postflood

3- 6-69_______ 1 in.= 50ft

(1:600)

__.._ lin. = 100ft 

(1:1,200)

5 City of Los Angeles.

2 California Division of 

Highways.

2 Do.

5 City of Los Angeles.

Dates on the cross-section lines in the following 

figures indicate the photography from which each 

was derived. Maps at the smaller scale (1:1,200) and 

larger contour interval (5 ft) covered the upstream end 

of the wash where changes from flood-induced scour 

and fill were relatively minor. Where scour and fill 

could be defined only by overlap of data at the two 

differing scales, the smaller scale was expanded computationally two times during the section-plotting process 

to match the larger scale. Fortunately, however, the 

area of greatest changes was covered by the larger 

scale maps. Because flow of sufficient competence to 

move boulder gravel did not occur between September 

1966 and June 1968, it was assumed that the 1966 

photography recorded conditions virtually constant 

through 1968. Both sets of photography define the 

configuration of Tujunga Wash at the start of the 

1968-69 storm season.

TYPES AND ACCURACY OF PHOTOGRAMMETRIC 

MAPPING

Two types of mapping are common in highwayengineering practice in California reconnaissance mapping and design mapping (Kulhan and Slavoj, 1969, 

p. 58-61). Both types may include extensive reaches 

of important channels, thus lending themselves to 

study of channel morphology, and both are illustrative 

of the techniques and accuracy available in photogrammetry which can be specifically applied to studies of 

channel morphology.

Reconnaissance mapping is primarily for route 

planning. Terrain factors control the combination of
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 Bll

scales and contour intervals, which range from 1:1,200 

to 1:4,800 and 5 to 20 feet, respectively.

Design maps commonly are prepared at a scale of 

1:600 with a 2-foot contour interval and include spot 

elevations at locations where interpolation between 

contours will not give a correct elevation. Such maps 

are of an accuracy that permits their use in many 

cases as a substitute for a final location survey and as 

the basis for calculation of earthwork volumes. Katibah 

(1968) noted that maps of this scale commonly are 

plotted by the 5-diameter direct projection plotter and 

that, with this instrument, as relief increases, the 

practical mapping width possible with each photograph 

decreases in proportion to the total relief. If there is 

no relief, the practical mapping width is 1,500 feet, 

using a width of 6 inches on the photographs. With as 

much as 200 feet of relief, for example, a channel survey 

with photography at the design scale could be included 

in a single flight line with a practical mapping width of 

1,300 feet.

Both types of maps conform to the National Map 

Accuracy Standards. The standards, among other requirements, state that 90 percent of all contours 

must be accurate to within one-half of the contour interval and that all shall be within one interval of their 

true elevation, except where terrain is hidden by brush. 

No less than 90 percent of the spot elevations should 

be within one-fourth of the contour interval from true 

elevation. In addition, present specifications for design 

maps in California state that the arithmetic mean 

shall not exceed:

±0.40 foot for 20 points tested, 

±0.30 foot for 40 points tested, and 

±0.20 foot for 60 or more points tested.

Tolerances for the mean are based on a standard deviation of 0.60 foot and a 99 percent probability. Amounts 

of scour and fill measured in this report are based on 

differences in elevations of two maps with the above 

standards of accuracy. Although, as will be seen below, 

the accuracy of the maps used surpasses these standards, 

critical values of scour and fill are described as approximate, with the above error factors understood to apply. 

Standards for horizontal control are rigorous to the 

point that horizontal-control error has less effect on 

accuracy of the data than does scale-change or sectionplotting error.

CONSTRUCTION OF CROSS SECTIONS

Tujunga Wash was initially studied in the field to 

select representative sites. Cross sections then were 

located on the topographic maps, and individual 

points,on cross sections were plotted at the map scale 

before reduction to publication size. , ,

Emphasis in plotting was placed on accurate determination of slope inflections and thalweg depths; 

at such points, elevations were determined by graphical 

interpolation between contours and between spot 

elevations and contours. Points so located are marked on 

the sections as questionable. Other points on the cross 

sections that do not coincide with contour elevations 

and that are not marked as questionable indicate 

close proximity (at map scale) of section lines to spot 

elevations.

Finally, the cross-section locations were reexamined 

in the field to assess the degree of artificial modification 

of the channel that occurred in the short interval 

between the time of the floods and the postflood 

photography.

SCOUR AND FILL IN TUJUNGA WASH

Cross sections were located to show the most significant changes due to scour and fill, and to be representative of changes within each section of reach. 

Sites that would overemphasize the magnitude of 

local changes were avoided. Location of the sections 

had to conform to the overlap areas of the different 

sets of maps, and the selected sites utilize the maximum coverage. In the upper half of the wash, section 

lines are the grid lines of the California coordinate 

system. Flow in the rest of the wash was oblique to the 

coordinate system; sections located there were referenced 

to permanent structures or topographic features whenever possible. Coordinate-section line intersections 

are shown on the sections for reference in possible 

future studies.

Profiles showing change in elevation of the channel 

thalwegs (fig. 5) were constructed from the crosssection data, to illustrate the longitudinal variation in 

scour and fill diagrammatically. Conclusions regarding 

the general behavior of ephemeral channels on alluvial 

fans will be based on these profiles following the 

description of the changes at individual sections.

Specific aspects of each preflood and postflood cross 

section are discussed in the following section.

SCOUR AND FILL PORTRAYED ON CROSS SECTIONS

SECTION A-A'

Little change that is not artificial is evident in 

section A-A' (fig. 6), in the confined channel within 

the mountain front. The fill indicated on the south bank 

(left bank in the cross sections) is a riprapped highway 

embankment. Scour or fill that might have occurred1 in 

the thalweg as a result of constriction of the natural 

channel by the highway embankment did not take 

place. The north bank (right bank in the cross sections) is bedrock., Close . correspondence of photogrammetrically oriented points on this steep slope
B12 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

1300 r

> 1200

< 1100

z 

o

1000

North channel profile prior to diversion

'M(S)

'L(S)

-North channel profile 

after downstream 

diversion to south 

channel

N(S)

EXPLANATION

North channel, preflood

North channel, postflood

P(S) South channel, preflood

 1060 Spillway elevation 

Hansen Flood-Control Basin South channel, postflood

Cross section, (N) north channel; 

or (S) south channel

0.5 1.0 1.5 2.0 2.5 

HORIZONTAL DISTANCE FROM HANSEN FLOOD-CONTROL BASIN, IN MILES

3.0

FIGURE 5. Longitudinal profiles of the main channels of Tujunga Wash illustrating scour and fill.

testifies to the accuracy of the mapping from which 

the sections were constructed.

SECTION B-B'

Fill across the entire channel apparently occurred 

at site B-B' (fig. 6) and cannot definitely be ascribed 

to any one cause. The section is at the point Tujunga 

Creek leaves the mountain front and enters Tujunga 

Wash.

Downstream from this section, between the January 

and February storms, a causeway embankment was 

constructed in place of a private bridge destroyed by 

the flow of January 25. The bridge previously provided 

the sole access for about 200 residents living on the 

north side of Tujunga Valley. Culverts through the 

causeway were designed to transmit flows substantially 

larger than those of January, but in the early morning 

hours of February 25 the causeway acted as a temporary 

impoundment and failed, releasing a surge of unknown, 

but probably small, magnitude into the valley. The 

fill at section B-B' may represent debris trapped 

behind this temporary impoundment. Again, apparent 

fill on the left bank is a highway embankment.

SECTION C-C'

No significant change occurred at section C-C' 

(fig. 6), located just below the point where Tujunga 

Creek enters Tujunga Wash. Near this point, floodflows were split into two main channels, one on each 

side of the valley, and the beginning of the south channel can be seen in this cross section. Splitting of the

main flow near the valley apex can be seen at the top 

center of figure 4.

Although splitting of the flow may have been influenced by the temporary causeway, the important 

point is that formation of single or multiple distributaries at the apex of the fanhead valley was a phenomenon to be expected under natural conditions. 

Preflood topographic maps reveal that the course of 

the south channel had a thalweg similar in elevation to 

that of the normal low-water channel adjacent to the 

north bank, and therefore virtually equivalent in its 

ability to capture flow under natural flood conditions. 

It can be seen in this section and downstream sections 

that the medial part of the wash actually had the highest elevation.

SECTION D-D'

The convex-upward shape of the floor of the wash 

is well illustrated in sections D-D' and E-E' (fig. 7), 

supporting the basic analogy of Tujunga Wash to an 

alluvial fan.

The left 500 feet of cross section D-D' corresponds 

closely with the rear property line of houses on the west 

side of Wescott Street (figs. 4, 8). The line of section 

D-D' is along the fence separating the houses on 

Wescott Avenue from the abandoned orchard shown 

in figure 4 and along the remnants of fence behind the 

inundated homes shown in the left-center part of 

figure 8.
Intersection of 

N 4,212,500; 

E 4,194,000 

1340 r

1330

1320

£ 1310

1300

3-15-69

8-24-66

A'

Intersection of 

N 4,213,500; 

E 4,193,000

B

1330

1320

1310

1300

1290

> 1280

Intersection of 

N 4,212,000; 

E 4,193,000

1300

1290

1280

1270

Intersection of 

N 4,211,500; 

E 4,192,000

8-24

9'

Same point as D

0 250 FEET

I I I I I I

TUJUNGA

INDEX MAP

FIGURE 6. Sections A-A', B-B', and C-C'. Locations of these and all following sections are shown in figure 3.
D

N 4,210,000 

1290

1280

1270

1260

D

N 4,211,000

Rear property line 

We scot-Avenue

Previous site of end 

of Grove Street

Line of section is rear property line of houses on west side of Wescott Avenue 

(projected across channel)

1250

Line of section is E 4,191,000

0 250 FEET

I I I I I I

INDEX MAP

FIGURE 7. Sections D-D' and E-E'
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B15
B16 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

The west end of Grove Street was covered by flooddeposited sediment, shown as fill in section D-D'. 

At the time of the 1969 floods, urbanization, as represented by Grove Street, was spreading rapidly across 

the channel on the south side of the valley (figs. 4, 8). 

Fill shown in the vicinity of Grove Street on section 

D-D', about 2 to 3 feet, is slightly less than that 

observed at nearby points in the field by means of 

buried automobiles and other debris.

Fill occurred in the north channel, but not to any 

significant degree.

SECTION E-E'

Little change is evident in section E-E' (fig. 7). 

The broadly convex-upward shape of the valley floor 

stands out plainly. Flow did not overtop the central 

part of the valley in this reach, and some of the differences in elevation in the central part of the valley more 

likely are due to bulldozing than to error in the method 

or in plotting, although error is a possibility. Poor 

correspondence of some elevations on this section is due 

to the fact that postflood control is less accurate, being 

derived from the 1:1,200-scale mapping.

The left bank in this reach is the outside of the concrete Haines Canyon Flood-Control Channel, which 

fortuitously diverted the south channel flows away 

from a highly urbanized part of the wash and stopped 

lateral scour that might have damaged many more 

homes.

Fill apparent in the south channel is natural and 

may reflect normal aggradation near the apex of a 

fan or fanhead valley.

SECTION F-F'

Fill near the left bank of section F-F' (fig. 9) is 

similar to that on section E-E' and can be ascribed to 

the same origin. Concomitant scour and fill, typical 

of the lateral migration of ephemeral channels, occurred 

in the north channel. Lateral scour was restricted there 

by the steep valley-side slope.

Surprisingly close correspondence of the preflood 

and postflood surveys in the middle section of the wash, 

which was not inundated, verifies the accuracy of the 

changes seen in the channels. Again, some of the small 

apparent differences are due to the difference in scale 

and level of accuracy between the preflood and postflood maps. Also, the connection of widely spaced control points with straight lines does not necessarily 

portray the actual shape of the section between control 

points.

SECTION G-G'

From section G-G' (fig. 9) and those preceding, it is 

clear that the south channel was a major natural 

drainage of the wash, having actually a lower thalweg

elevation than the north channel in this section of the 

wash. It is not surprising, therefore, that a substantial 

part of the floodflow entered this channel in spite of 

levees intended to contain flow from Tujunga Creek 

in the north channel.

As in the upstream sections, there is evidence of fill 

in the south channel and shift in position of the north 

channel.

SECTION H-H'

At this point in Tujunga Wash (fig. 10), the pattern 

of fill in the south channel ceased. Section H-H' may 

be the possible upstream limit of the effects of locally 

reduced base level which occurred at a large gravel 

pit, 2,600-3,000 feet downstream.

Note the beginning of enlargement and an apparent 

slight deepening of the north channel.

SECTION /-/'

A pronounced increase in the amount of net vertical 

scour can be seen to have occurred in the north channel 

at section /-/' (fig. 10). The south channel also was 

deepened, and in both, the scour represented net removal of bed material from the cross section. There is 

little corresponding fill as was true in the simple lateral 

shift of a channel seen in sections F-F', G-G', and others 

upstream. These changes, in both channels, point incontestably to the effects of lowered base level further 

downstream.

SECTION /-/'

Net vertical scour of the thalweg increased to more 

than 10 feet in the north channel and to about 4 feet in 

the south channel at section J-J' (fig. 11). Again, 

there is little corresponding fill. The above figures 

probably approach the maximum amounts of scour 

that occurred at this point during peak flow because, in 

these oversteepened channels, scour may have continued on the receding stage of the flood. In other words, 

most of the scour that occurred at this section constituted net removal of bed material from the reach.

Minor gullying from local runoff in the central part 

of Tujunga Wash is detectable in this cross section. Section J-J' and all sections downstream are direct 

comparisons of design maps at the highest order of 

accuracy (contour interval: 2 ft).

SECTION K-K'

The section line of K-K' is parallel to Foothill Boulevard (fig. 3) and 150 feet upstream (fig. 11). Net scour 

that occurred at this section is representative, on the 

conservative side, of the net scour that took place at 

the two Foothill Boulevard bridges and the single 

span, downstream from Foothill Boulevard, of Wentworth Place (fig. 3). The large Foothill Boulevard 

bridge over the north channel did not fail during the
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B17

in v n in CM CM CM CM

133d Nl H3A3T V3S NV3W 3AO8V NOI1VA313
FEET IN LEVEL, SEA MEAN ABOVE ELEVATION 

(?) fill Artificial 

(?) fill Artificial 

(?) fill Artificial 

\

813 QNV onavnaAH samaxs do SH3MH 
J

1220 r

1210

1200

1190

1180

> 1170

South channel / 6-10-68

Line of section is 680 feet east and parallel to Foothill Boulevard crossing of Tujunga Wash

K

Edge of Foothill Boulevard bridge abutment 

< 1210

Z

o

< 1200

1190

1180

1170

1160

Line of section is 150 feet east and parallel to Foothill Boulevard

0 250 FEET

I I I I I I

FIGURE 11. Sections J-J' and K-K',
B20 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

January flows, although the Los Angeles Fire Department reported erosion around pier supports and considerable vibration on the span. Failure of the structure, 

built in 1937, occurred during the peak February flow 

by scour around the piers.

It was surprising that the bridge stood as long and as 

well as it did. Net thalweg scour was about 9 feet in 

the north channel and 5 feet in the south channel at 

this section; these figures do not approach the maximum net scour that occurred at specific points in the 

section about 20 feet in the north channel and 15 

feet in the south channel. The large amounts of debris 

from both lateral and vertical scour were uncompensated by any significant degree of fill in either channel.

Figure 12 shows the south channel upstream from 

the Foothill Boulevard bridge. The incision of the 

main part of the south channel is clearly evident in 

the steep sides of the wash and the knickpoint and 

plunge pool formed where tributary flow, as shown at 

the bottom of the photograph, joins the larger channel.

The accuracy of the photogrammetry is such that 

minor gullying in the central part of the wash also is 

detectable in section K-K'.

SECTION L-L'

Only the south channel is shown in cross section 

Lr-L' (fig. 13) because of a gap in the photogrammetry. 

The line of section transects the Bengal Street terrace 

which, before the floods, was the site of middle-class 

suburban homes with lots extending to the edge of the 

terrace. Before the floods, the terrace level at this 

point was 8 feet above the south channel. Postflood, 

however, the remnant of the terrace is 19 feet above the 

bottom of the channel. Net vertical scour of about 11 

feet took place in the channel thalweg during the 1969 

floods at this site.

Of more practical concern was the lateral scour that 

removed 75 feet of the terrace at this line of section, 

including all of Bengal Street and seven of the homes 

that bordered Bengal Street. A comparable amount of 

scour occurred on the right bank of the south channelChannel change at this site basically was one of incision 

and enlargement of the old channel without much tendency of the channel to shift laterally. The cause of the 

incision was the lowering of local base level which took 

place when flow entered the gravel pit a short distance 

downstream combined with adjustment of the channel 

configuration to the large flood discharge. That the 

scour at this site was primarily a function of the reduced base level, however, is proved by corresponding 

scour in the north channel and an increase in scour in 

both channels in a downstream direction.

Figure 14 shows the incision of the wash into the 

residential area and the remnant of the Bengal Street 

terrace early on the morning of February 25, shortly 

after most of the lateral scour had already taken 

place.

SECTION M-M'

Section M-M' (fig. 13) crosses the upstream end of 

the gravel pit into which both north and south channels 

flowed. Earthen embankments intended to channel 

flow around the pit were not effective, particularly in 

the south channel where flow was much greater than 

expected, primarily due to branching of the flow at 

at the valley apex.

Sand and gravel were mined sporadically at this site 

from 1925 until the mid-1960's when, after failure of 

the lessee to obtain appropriate zoning on additional 

acreage, the operation became inactive. Estimates by 

the landowner of the amount of debris added to the 

main pit were 200,000-300,000 tons for the January 

period and 2-3 million tons for the February storm, 

the latter figure presumably including the earlier total. 

Mining of the newly added debris began in 1969.

The cross, section shows that about 20 feet of fill 

occurred uniformly across the bottom of the pit. The 

north channel, seen at the right end of the section, 

entered the pit a short distance downstream. About 14 

feet of net vertical scour took place in the northchannel thalweg, and as much as 24 feet of scour occurred at a single point. The steepness of the northchannel thalweg, indicated here by its still considerable 

elevation above the pit bottom, suggests that erosion of 

channels upstream from the pit would have continued, 

had large discharges continued for a longer period 

of time.

SECTION N-N'

A greater quantity of fill, as much as 35 feet, is shown 

near the downstream end of the gravel pit in section 

N-N' (fig. 15). At this point, flows from both the north 

and the south channels had entered the pit and rejoined, the total flow then exiting through an old 

channel along the south side of the valley where desilting ponds had been constructed.

Visible on the right side of this section is the riprapped berm against which the main channel was 

apparently intended to be confined downstream from 

Foothill Boulevard. Construction of a small levee to 

confine the low-water channel against the riprapped 

berm can be seen near the right end of the section. 

The berm itself was undamaged by the floodwaters 

which, unfortunately, were diverted away from the 

berm through both natural and manmade causes.
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B21
Point on terrace 

1200 r

Preflood positionv «... of Bengal Street\ South channel

11900 " -* *-

1180

1170 

L'

Edge of Foothil I 

Boulevard

td to to

1160

1120-

1110

-3-6-69

TUJUNGA WASH

.-XT

4000 FEET

I I

Base of highway fillFoothill Boulevard

W*! ro

hH

OI^

whH

O

>

55

OW*! 

O

gcj F

hH 

O

H 

Of

W

W 

w

FIGURE 13. Sections L-L' and M-M'.
o

Od

ad 2

e

w >

W MMCQ 

Od

Hw

FIGURE 14. View looking northwest of what remained of the Bengal Street terrace shortly after the February 25 flood peak. Bengal Street originally ran 

east-west (upper left to lower right in photograph) across the area now occupied by the south channel of Tujunga Wash and intersected the street shown 

at left center. Height of the cutbank at the edge of the terrace is 18 feet. Photograph by Harold Morby.

bdto

w
wto

N

Top of hill

Elevation: preflood, 1160.9 ft; 

postflood, 1160.7 ft 

1190

1180

1170116011501140

1130

<

> 1120

1110

1100

Point on terrace above berm

North channel

(flood diverted to south channel) f Berm

with 

riprap

N

O

o

W

CQ

Hd

oI IH 

CQO

CQ

INDEX MAP

FIGURE 15. Section N-N'.
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B25

SECTION O-O'

That most of the floodflow was in the south channel 

is readily apparent in cross section 0-0' (fig. 16); 

little scour and fill occurred in the north channel during 

the period before flow entered the gravel pit upstream 

from this section. The scour that proceeded upstream 

from the pit edge captured all the subsequent floodflow 

in the north channel.

The most significant change in the south channel 

was one of fill net vertical deposition in the thalweg 

of about 10 feet. The channel widened by some 60 feet 

to accommodate the unusually high discharge, but no 

marked net erosion of the main terrace level occurred. 

It is difficult to assign an exact cause to the thalweg 

fill that occurred at this point; upstream effects of 

the Hansen Flood-Control Basin, or deposition in the 

preflood channel which apparently was deepened to 

drain the gravel pit, are likely explanations.

Note the extremely close correspondence of the 

topography outside the flood channels.

SECTION P-P'

A similar quantity of fill about 12 feet in the southchannel thalweg occurred at section P-P' (fig. 16). 

About 3 feet of fill also occurred in the north-channel 

thalweg, lending support to the idea that channel 

fill here and at the preceding site was due in part to 

the backwater effects of the reservoir. The spillway 

elevation of the reservoir is reached 4,100 feet downstream from this section.

Not evident at this section line and undocumented 

by the photogrammetric coverage was a severe quantity 

of lateral erosion that occurred just downstream. 

There, south-channel flow was directed strongly against 

the bedrock wall of the canyon and removed a twoblock section of Wentworth Street, previously a major, 

four-lane arterial highway. Similar destruction of 

Wentworth Street at the same locality occurred during 

the 1938 flood; this damage went unrepaired and 

Wentworth Street remained impassable until the early 

1960's.

SUMMARY AND CONCLUSIONS

Changes in the channels of Tujunga Wash and the 

resulting property damage caused by the 1969 floods 

were great because of both natural and manmade 

causes. The effects of man were significant, not necessarily because of incomplete flood-control measures, 

but because of man's failure to recognize the true 

character of the natural landscape in this area, the 

fact that Tujunga Wash is similar in most respects to 

an alluvial fan and that its natural ephemeral channels 

can be expected to change dramatically during floods.

The chief difference between Tujunga Wash and an 

alluvial fan is that the wash continues to be partly 

constricted by bedrock valley-side slopes for a considerable distance after surface flow leaves the mountain front. The practical significance of this difference 

is that flood effects, such as channel changes, are concentrated in a smaller radial segment, centered at the 

mountain front, than is typical of an alluvial fan.

Scour or fill due to a variety of specific causes occurred in Tujunga Wash. The causes included possible 

natural channel aggradation, lateral movement of 

distributaries, local decrease in base level, local increase 

in base level, and natural adjustment and shift of the 

channel in response to changes in flow parameters. 

However, several major changes in the channel and the 

resultant property damage serve as especially graphic 

examples of what can be expected to occur under similar 

conditions the combination of a major flood and an 

urbanized alluvial fan. These major changes are summarized in the following sections.

FLOW DIVERTED TO DISTRIBUTARY CHANNEL

Although attempts had been made to contain all 

expected flow in the north channel of Tujunga Wash, 

a significant part (about one-half) of the flood discharge 

entered the south channel (figs. 4, 8; sections C-C', 

D-D', and E-E'). No judgment can be made as a 

result of this study as to whether or not the causeway 

created as an access road to the north side of Tujunga 

Valley was the cause of this diversion. A significant 

point, however, is that formation of distributaries at 

the apex of a fan or fanhead valley was a natural, 

expectable occurrence. Splitting of the February 1969 

floodflow occurred where and when it likely would 

have done so under entirely natural conditions. The 

south channel was nearly as probable a natural flood 

course within Tujunga Wash as was the north channel.

The question as to why urbanization was allowed to 

proceed within the south channel (fig. 8) before completion of adequate flood-control measures is one that 

must be left to others. Damage along the south channel 

farther downstream (between sections D-D' and F-F'} 

would have been high were it not for the fortunate 

protection afforded by the concrete outlet channel 

from Haines Canyon.

VERTICAL SCOUR DUE TO LOCAL REDUCTION IN BASE 

LEVEL

The thalwegs of both north and south channels were 

scoured from the vicinity of section H-H' to the 

point where both channels entered the gravel pit west 

of Foothill Boulevard, a distance of 2,600-3,000 feet. 

The net vertical scour of the channel thalweg increased progressively downstream to about 14 feet 

in section Af-AP.
0

Point on Cottonwood Avenue terrace 

1160r

1150

1140

1130

1120

1110

1100

South channel 

6-10-68

0'

Top of berm on right bank 

Elevation: preflood, 1154.8 ft; 

postf lood, 1155.2 ft

North channel 

(flow diverted to south channel).

P'

O Point on terrace 

< 1140 r

1130

1120

1110

1100

1090

1080

North channel 

(flow diverted to south channel)

Point behind 

berm on terrace

FIGURE 16. Sections O-O' and P-P'.
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B27

The vertical scour in this section of the channel was 

largely the direct result of the lowering of base level 

when flow broke through from each channel into the 

gravel pit. Scour then proceeded upstream and ceased 

in the oversteepened reaches only when flow was no 

longer competent to transport the bed material.

The failure of three bridges spanning this reach, 

two on Foothill Boulevard and one on Wentworth 

Place, was one result of the scour. This event emphasizes 

the need for hydrologic considerations in the issuance 

of future gravel-mining permits in streambeds without 

effective flood-control channels. Because sand and 

gravel constitute the most important inorganic mineral 

resource in southern California, plans for mining must 

be made in certain channels. Such planning could 

help forestall a potential shortage of aggregate as well 

as reduce the harmful effects of channel diversion and 

scour triggered by mining operations in active channels.

LATERAL SCOUR OF TERRACES

The most dramatic damage (fig. 14, section L-Z/) 

was due to lateral scour of the main surface in Tujunga 

Wash. Bengal Street and seven homes bordering it 

disappeared shortly after 5:30 a.m. on February 25. 

Scour along the sides of the south channel removed 

75 feet of land surface from the urbanized left bank 

and 125 feet from the right bank. This lateral scour 

was concomitant with net thalweg scour of 11 feet, 

caused basically by the change in base level discussed 

above. The effects of vertical scour combined with the 

lateral scour served to remove 18 feet of the land surface (net vertical scour) at the site of Bengal Street in 

section L-Z/.

Basically what occurred in the south channel adjacent to the Bengal Street terrace was dimensional 

enlargement of the flooded channel cross section by a 

factor of two; shape and hydraulic parameters of the 

channel remained the same. The increased flow in the 

south channel was the result of the distribution of part 

of the flow from Big Tujunga Canyon at the apex of 

the wash combined with flow from Haines Canyon. A 

greater degree of impervious surface due to urbanization 

in the Haines Canyon drainage acted to increase peak 

discharge from that source which, however, was minor 

compared to flow within the wash. Generally, lateral 

change in the south channel was one of adjustment to 

the increased discharge. Added to this change was the 

increased scour due to reduced base level; this effect 

served to incise the channel and reduce its tendency 

toward lateral movement.

The equilibrium configuration toward which the 

stream with its lowered base level was tending is largely 

a matter of opinion, but it is probable that equilibrium 

would not have been attained even with continued

high discharges for several days. Channel instability 

would probably have continued. What channel changes 

would have occurred with only the increased discharge, 

had not incision of the channel taken place, can only 

be surmised. Without the base-level effects of the gravel 

pit, thalweg scour of a lesser amount would have 

occurred and would have been in large part temporary 

during passage of the flood peaks. Lateral erosion locally 

would have been greater but also more subject to the 

vagaries of a constantly shifting, alluvial-fan drainage 

course; erosion of the Bengal Street terrace might have 

been greater or may not have occurred at all. Natural 

channel shift probably was the cause of the loss of 

Wentworth Street, downstream from the cross-section 

sites.

Once again, however, it is clear that the danger to 

homes on the terrace was evident before the flood from 

a consideration of the geomorphic setting of Tujunga 

Wash. Urbanization on the unstabilized cutbank of a 

natural flood channel on an alluvial fan or fanhead 

valley generally is a poor risk.

CHANGES IN LONGITUDINAL PROFILES

Inspection of figure 5 reveals some potentially significant conclusions regarding the general behavior of 

ephemeral channels on alluvial fans. Comparing preflood and postflood profiles downstream from where 

much of the flow left the north channel and entered 

the south channel, the point of fanhead jump, it is 

apparent that the diversion locally resulted in scour 

of the north channel that corresponded in amount with 

fill that occurred in the south channel. The correspondence is most notable in the reach from 1.7 to 1.4 miles 

above the spillway elevation of Hansen Flood-Control 

Basin (fig. 5). Not only was scour in the first channel 

matched by fill in the channel to which the fanhead 

jump occurred, but the postflood profiles of both channels became nearly parallel, after smoothing of pronounced preflood irregularities in the channel which 

were both natural and the result of the gravel pit and 

other .works of man.

By analogy to a natural fan, the smoothing and 

similarity in gradient of the profiles may be functions 

in maintenance of a long-term trend toward equilibrium. 

Small floods or debris-flows and mudflows, both of the 

latter commonplace on many fans, may over the short 

term create distributary channels in the fanhead area 

with irregular profiles representing temporary inequilibrium. The preflood, largely manmade irregularities 

in Tujunga Wash may be considered analogous to 

these smaller, natural features. Thus, the jump of a 

major channel during a major flood, as seen in Tujunga 

Wash, will involve smoothing as well as steepening 

and through this action represents an essential median-
B28 PHYSIOGRAPHIC AND HYDRAULIC STUDIES OF RIVERS

ism by which the maintenance of an equilibrium is 

accomplished over geologic time.

It is probable that with sustained flow over a long 

period, this change in accord with long-term equilibrium 

would have been even more pronounced in Tujunga 

Wash, but,as noted above, the exact equilibrium profile 

is a matter of conjecture. In any event, the jump in 

flow from the north channel to the south channel at the 

apex of Tujunga Wash was a likely natural adjustment 

of the alluvial system.

PHOTOGRAMMETRIC METHODS APPLIED TO THE 

DETERMINATION OF SCOUR AND FILL

Photogrammetry of the order of that used for highway-design maps can be a valuable tool in the quantitative study of channel change. Comparison of four 

sets of design maps of Tujunga Wash, two compiled 

before and two after the 1969 floods, clearly allowed 

significant measurements of scour and fill. Most of 

the maps used had a contour interval of 2 feet and were 

plotted at a scale of 1 inch equals 50 feet (1:600). 

Others with a contour interval of 5 feet at a scale of 

1 inch equals 100 feet (1:1,200) were used locally.

Accuracy standards by which such maps are prepared 

required that contour lines be accurate to within onehalf of the contour interval, resulting in confidence 

limits of ±1 foot for design maps. Specification accuracy 

of amounts of scour and fill derived from differences 

between two such maps is ±2 feet. Empirically, 

however, comparing the elevations on design maps of 

points not affected by scour or fill, accuracy generally 

surpassed this figure. Even specification accuracy was 

acceptable in dealing in this study with scour of as 

much as 20 feet (section K-K'} and fill of as much as 

35 feet (section N-N'}.

APPLICATION OF RESULTS

The scour and fill that occurred in Tujunga Wash, 

although possibly unique in magnitude and diversity of 

cause, is a concentrated example of many of the changes 

that may occur under natural or urbanized conditions 

during floods on alluvial fans and in fanhead valleys. 

Such changes, before urbanization, went largely unnoticed except when catastrophic, and their widespread 

effects on urbanization in southern California became 

substantially more than academic for the first time 

during the 1969 floods.

An increasingly greater proportion of new urbanization is subject to the processes described in this 

report. Pressure is relentless for development of increasingly marginal areas in terms of danger from 

geologic and hydrologic hazards. Fanhead valleys 

similar to Tujunga Wash represent the last undeveloped areas not subject to slope-stability problems in 

much of urban southern California.

Solutions need not involve only the construction of 

engineering works in such areas. The flood-control 

structures in the Los Angeles County Flood-Control 

District functioned well during the 1969 floods. However, as programs of a scale to assure safe urbanization 

are applied to smaller areas, diminishing returns 

rapidly become evident. It is economically impractical 

to protect the area downstream from every frontal 

watershed in the mountains of southern California. 

The present program of debris-basin construction by 

the Los Angeles County Flood-Control District, for 

example, does not attempt to do this and is based on 

sound economic considerations made by the county, 

not by developers. What is generally needed is an increased focus on the natural realities of the environment before urbanization in arid and semiarid areas, 

followed by uniform zoning and planning in accord 

with those realities. It may even appear in some instances that the greatest eventual benefit-cost ratio 

will be achieved in fanhead washes through uses other 

than as additions to an existing sea of homesite 

congestion.

REFERENCES CITED

Culbertson, D. M., Young, L. E., and Brice, J. C., 1967, Scour and 

fill in alluvial channels, with particular reference to bridge 

sites: U.S. Geol. Survey open-file report, 58 p.

Emmett, W. W., and Leopold, L. B., 1965, Downstream pattern 

of river-bed scour and fill, in Proceedings Federal InterAgency Sedimentation Conference, 1963: U.S. Dept. Agriculture, Agr. Research Service Misc. Pub. 970, p. 399-409.

Fahnestock, R. K., 1959, Dynamics of stream braiding as shown 

by means of time lapse photography[abs.]: Geol. Soc. America 

Bull., v. 70, p. 1599.

Hickey, J. J., 1969, Variations in low-water streambed elevations 

at selected stream-gaging stations in northwestern California: 

U.S. Geol. Survey Water-Supply Paper 1879-E, 33 p.

Katibah, G., 1968, Photogrammetry in highway practice: California Div. Highways, p. 8-17.

Kulhan, E. F., and Slavoj, D. E., 1969, Photogrammetry: Berkeley, 

California Univ., Inst. Transp. and Traffic Eng., 70 p.

Lane, E. W., and Borland, W. M., 1954, River-bed scour during 

floods: Am. Soc. Civil Engineers Trans., v. 119, p. 1069-1089.

Leopold, L. B., Emmett, W. W., and Myrick, R. M., 1966, Channel 

and hillslope processes in a semiarid area, New Mexico: 

U.S. Geol. Survey Prof. Paper 352-G, p. 193-253.

Leopold, L. B., and Maddock, Thomas, Jr., 1953, The hydraulic 

geometry of stream channels and some physiographic implications: U.S. Geol. Survey Prof. Paper 252, 57 p.

Leopold, L. B., Wolman, M. G., and Miller, J. P., 1964, Fluvial 

processes in geomorphology: San Francisco, W. H. Freeman 

& Co., 522 p.

Maddock, Thomas, Jr., 1969, The behavior of straight open channels with movable beds: U.S. Geol. Survey Prof. Paper 

622-A, 70 p.

Rantz, S. E., 1970, Urban sprawl and flooding in southern California: U.S. Geol. Survey Circ. 601-B, 11 p.

Scott, K. M., and Gravlee, G. C., 1968, Flood surge on the Rubicon River, California hydrology, hydraulics, and boulder 

transport: U.S. Geol. Survey Prof. Paper 422-M, 40 p.
SCOUR AND FILL IN TUJUNGA WASH A FANHEAD VALLEY IN URBAN SOUTHERN CALIF. 1969 B29

Simpson, L. D., 1969a, Summary report, storms of 1969: Los 

Angeles County Flood-Control District, 55 p.

 1969b, Hydrologic report on storms of 1969: Los Angeles 

County Flood-Control District, 286 p.

Stewart, J. H., and LaMarche, V. C., Jr., 1967, Erosion and 

deposition produced by the flood of December 1964 on Coffee 

Creek, Trinity County, California: U.S. Geol. Survey Prof. 

Paper 422-K, 22 p.

Troxell, H. C., and others, 1942, Floods of March 1938 in southern

California: U.S. Geol. Survey Water-Supply Paper 844,

399 p. 

Waananen, A. 0., 1969, Floods of January and February 1969 in

central and southern California: U.S. Geol. Survey open-file

report, 233 p.

' U.S. GOVERNMENT PRINTING OFFICE: 1973 SIS 638/33