A Hydrologic Assessment of the 

September 14, 1974, Flood in 

Eldorado Canyon, Nevada 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 930 

Prepared in cooperation with the 

U.S. National Park Service 

A HYDROLOGIC ASSESSMENT OF THE 

SEPTEMBER 14, 1974, FLOOD IN 

ELDORADO CANYON, NEVADA 
Aerial view of Eldorado Canyon looking. upstream (west) on September 30, 1974. 
A Hydrologic Assessment of the 

September 14, 1974, Flood in 

Eldorado Canyon, Nevada 

By PATRICK A. GLANCY and LYNN HARMSEN 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 930 

Prepared in cooperation with the 

U.S. National Park Service 

A presentation of hydrologic data and interpretations, 

eyewitness accounts of destruction, 

and documentation of flooding 

UNITED STATES GOVERNMENT r-PRI NT I NG OFFICE, WASHINGTON: 197 5 
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS C. B. MORTON, Secretary 

GEOLOGICAL SURVEY 

V. E. McKelvey, Director 

Library of Congress Cataloging in Publication Data 

Glancy, Patrick A. 

A hydrologic assessment of the September 14, 1974, flood in Eldorado Canyon, Nevada. 

(Geological Survey Professional Paper 930) 

Bibliography: p. 27-28. 

Supt. of Docs. No.: I 19.16:930 

1. Floods-Nevada-Eldorado Canyon. I. Harmsen, Lynn, joint author. II. United States. National Park Service. 

Ill. Title. IV. Series: United States Geological Survey. Professional Paper 930. 

GB1225.N3G55 551.4'8 75-619132 

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

Washington, D.C. 20402 

Stock Number 024-001-02692-9 
CONTENTS 

Page Page 

Abstract ___ _ __ __ _ _ __ _ _ __ __ _ _ _ _ _ _ ____ _____ _ _ _ ___ _ _ ____ _ _ ___ 1 Runoff-Continued 

Introduction ---------------------------------------------- 1 Runoff volume ---------------------------------------- 10 

The setting _______________________________________________ _ 2 Measured streambed and high water profiles ____________ 10 

IIistory ---------------------------------------------- 5 Flood frequency and magnitude ________________________ 10 

Basin characteristics ____ ------------------------------ 5 Similar floods ---------------------------------------- 12 

Slope ------------------------------------------- 5 Sediment ------------------------------------------------ 14 

(}eology ----------------------------------------- 5 Sediment deposits ------------------------------------- 14 

Vegetation _____ ---------------------------------- 7 Sediment transport characteristics______________________ 16 

The storm ------------------------------------------------

Runoff----------------------------------------------------

7 Erosion ---------------------------------------------- 21 

8 Estimated landscape denudation________________________ 24 

Flow rates ___________________________________________ _ 8 Acknowledgments ---------------------------------------- 24 

Flood wave characteristics ---------------------------- 9 References cited ------------------------------------------- 27 

ILLUSTRATIONS 

Page 

FRONTISPIECE: Aerial view of Eldorado Canyon looking upstream (west) on September 30, 1974. 

FIGURE 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

15. 

16. 

17. 

18-28. 

Photographs of flood-damaged trailer, truck, and boats----------------------------------------------------------- 2 

Map showing location of area described in this report ----------------------------------------------------------- 3 

Map of Eldorado Canyon basin showing major tributary subbasins, area-altitude distribution, and location of streamflow 

estimate sites ---------------------------------------------------------------------------------~----------- 4 

(}raph showing longitudinal profiles of main drainage channels---------------------------------------~----------- 6 

Photograph showing eastward aerial view oflower Eldorado Canyon ___________________________ -------~----------- 6 

<1raph showing maximum water discharges in relation to drainage areas in the United States ---------~----------- 9 

Photographs of Eldorado Canyon mouth during late stagesoffloodflow and during postflood excavation of flood sediment 

deposits ___________________________________________________________________________________________________ 11 

Photograph of wave-cut bench (above debris line) along east shore of Lake Mohave _________________________________ 12 

(}raph showing trace of Lake Mohave stage at Davis Darn _______________________________________________________ 12 

Vertical aerial photo ofthe terminal reach of Eldorado Canyon drainage and adjacent drainages on September 20, 197 4 __ 13 

(}raph showing estimated flood hydrograph for September 14, 1974, near mouth of Eldorado Canyon _________________ 15 

Map of flood boundaries, streambed profile line, and specific cultural features _____________________________________ 16 

<1raph showing profiles of peak discharge high water lines and streambed at slope-area site in Eldorado Canyon ________ 18 

<1raph showing profiles of peak discharge high water lines and streambed, Eldorado Canyon Resort _________________ "19 

Downstream (eastward) aerial photograph of Eldorado Canyon terminus taken September 17, 1974 _________________ 20 

Photograph of heavily damaged trailer park at Eldorado Canyon Resort_ __________________________________________ 20 

Map showing sediment deposits and locations of preflood and postflood shorelines -----------------~---~----------- 22 

Photographs showing: 

18. Excavated sediments quantitatively described in table 5 ___________________________________________________ 23 

19. Stratified sediment deposited at the mouth of Eldorado Canyon ___________________________________________ 24 

20. Floating debris at the mouth of Eldorado Canyon _________________________________________________________ 25 

21. Downstream view of boulder deposits that probably moved on September 14 in Techatticup Wash ________ 25 

22. Large boulder that probably moved during flood in lower reaches of Eldorado Canyon _______________________ 25 

23. Position of high water line at canyon narrows just upstream from former restaurant _______________________ 26 

24. An automobile at rest in lower Eagle Wash after about a 1-rnile transit in flood _____________________________ 26 

25. Evidence of intense rill erosion in unnamed tributary to lower Eldorado Canyon ___________________________ 26 

26. Evidence of minor channel flow and only minimal rill erosion in Copper Canyon ___________________________ 27 

27. flighway damage in Techatticup Wash caused mainly by lateral channel scour _____________________________ 27 

28. Windrows of boulders bordering a pre-September 14, 1974 erosion scar _____________________________________ 27 

v 
VI 

TABLE 

CONTENTS 

TABLES 

Page 

1. Approximate area-altitude distribution of Eldorado Canyon basin ------------------------------------------------- 5 

2. Summary of hydraulic data resulting from peak-flow estimates --------------------------------------------------- 8 

3. Floods having peak flows per unit drainage area greater than that of Eldorado Canyon _____________________________ 12 

4. Estimated nonorganic sediment deposits _______________________________________________________________________ 14 

5. Approximate particle-size distribution of sediment samples _______________________________________________________ 15 

CONVERSION FACTORS 

For those readers who may prefer to use metric units rather than English units, the conversion 

factors for the terms used in this report are listed below: 

Multiply English unit 

Length 

inches (in.) _______________________ _ 

feet (ft)_ __________________________ _ 

yards (yd) ________________________ _ 

miles (mi) -------------------------

Area 

By To obtain metric unit 

25.4 ___________ millimetres (mm) 

.0254 ___________ metres (m) 

.3048 ___________ metres (m) 

.9144 ___________ metres (m) 

1.609 ___________ kilometres (km) 

square feet (ft2 ) ____________________ .0929 ___________ square metres (m2 ) 

acres------------------------------ 4047 ___________ square metres (m2 ) 

square miles (mi2) ________ :__________ 2.590 ___________ square kilometres (km2) 

Volume 

cubic feet (ft3)______________________ 28.32 ___________ cubic decimetres (dm3) 

cubic yards (yd3) __________________ _ 

acre-feet (acre-ft)-------------------1233 

Flow 

.02832 ___________ cubic metres (m3) 

.7646 ___________ cubic metres (m3) 

_ __________ cubic metres (m3) 

feet per second (ft/s)---------------- .3048 ----------- metres per second (m/s) 

cubic feet per second (ft3/s) ----------

miles per hour (mi/hr)--------------

Mass 

28.32 ___________ litres per second (1/s) 

1.609 ___________ kilometres per hour (km/hr) 

tons (short)------------------------ .9072 ----------- tonnes (t) 

Density 

pounds per cubic foot (lb/ft3)_________ 16.02 ___________ kilograms per cubic metre (kg/m3) 
A HYDROLOGIC ASSESSMENT OF THE SEPTEMBER 14, 1974, 

FLOOD IN ELDORADO CANYON, NEVADA 

By PATRICK A. GLANCY and LYNN HARMSEN 

ABSTRACT 

A devastating flash flood of thunderstorm origin struck Eldorado 

Canyon, a 22.9-square-mile drainage with a history of flooding, in 

southern Nevada, at about 2:30p.m., September 14, 1974. The flood 

killed at least 9 people, destroyed 5 trailer homes and damaged many 

others, obliterated a restaurant, destroyed 38 vehicles, 19 boat trailers, 23 boats, half of the boat-docking facilities, and the gas dock. The 

severe runoff resulted from intense basinwide rain and hail at rates up 

to 3 inches of precipitation per half an hour. The storm moved down basin and generally increased in intensity, which compounded runoff 

rates. Peak discharge was estimated to be 76,000 cubic feet per second 

just upstream from the developed area near the canyon mouth. About 

2,000 acre-ft of runoff reached Lake Mohave, the canyon terminus. 

Runoff dumped an estimated 70,000 cubic yards (about 100,000 tons) 

of inorganic sediment in Lake Mohave and throughout the lowermost 

canyon reach. It also delivered an estimated 4 acre-ft of organic or 

floating debris to Lake Mohave. The inorganic sediment was estimated to be less than 1 percent boulders, 40 to 60 percent gravel, 20 to 

40 percent sand, and 10 to 25 percent silt-clay. Although the recurrence interval for this magnitude runoff is great, a similar flood could 

occur in any given year. These types of flash floods, although common 

in the desert southwest, are not fully understood and are frequently 

ignored, and therefore the danger to developed areas is not decreased. 

With proper understanding and informed planning, the risk of damage from similar floods in the future can be greatly reduced. 

INTRODUCTION 

"It first looked like a dark heavy cloud of dust. Looked 

like a solid wall moving down. As it came down, every 

vehicle was pulled into this muck. I saw 4-6 vehicles in 

the debris. The wall of muck appeared to go under the 

lake when it hit the water, causing a swell of water at 

the surface." Lemuel Washington, a weekend fisherman 

from Las Vegas, vividly described his impression of the 

onrushing flash flood of September 14, 1974, at the 

mouth of Eldorado Canyon. In many ways the flood Mr. 

Washington witnessed probably resembled a dozen or 

more similar floods that occurred throughout Nevada 

during the summer of 1974. Hundreds of these floods 

have occurred during historic times though many have 

not been observed by man. The Eldorado Canyon flood 

was unique because it occurred in a popular recreation 

area, and several accounts by witnesses have helped to 

document the event. 

Although hydrologists tend to refer to the Eldorado 

Canyon flood as "a spectacular hydrologic event," Dick 

Mayne, Clark County Coroner, and other members of 

the local search-and-rescue squad call it "a catastrophe." Without its disastrous consequences, the flood 

probably would have gone generally unnoticed except 

by those who are interested in "spectacular hydrologic 

events." Everyone agrees that the loss of life and property damage was a regrettable tragedy; however, the 

tragedy has triggered renewed efforts by individuals 

and agencies to reduce the risks involved through better 

planning based in part on data obtained from the Eldorado Canyon flood. These data should help those concerned to reach an improved understanding and knowledge of the forces, power, and characteristics of natural 

processes. 

Losses resulting from the flood of September 14, 1974, 

at Eldorado Canyon are difficult to determine accurately. The complex array of physical losses and expenditures will ultimately be resolved; however, damages 

caused by the loss of life can never be accurately assessed or compensated. 

Almost all significant flood damage, with the exception of highway damage along Techatticup Wash, occurred within the Eldorado Canyon Resort area near 

the canyon mouth. At least nine people lost their lives 

and several others may still be missing. Known dead 

include four men, three women, and two children. The 

first three bodies were recovered from floating debris at 

the canyon mouth during the first three days of search 

operations. Five other victims were recovered between 

14 and 38 days after the flood. Their bodies were discovered floating in Lake Mohave as much as 2% miles north 

or south of the former boat landing. 

The restaurant was totally destroyed. Five trailer 

houses were totally destroyed, some have not been 

found, and a number of others were seriously damaged. 

Nine cabins near the base of the north canyon wall were 

destroyed, and 38 vehicles and 19 boat trailers were lost. 

Twenty-four boat-docking slips were obliterated and 23 

boats were lost. Figure 12 shows changes to the boat 

1 
2 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPI'EMBER 14, 1974 

docks, the general location of a number of other specific 

cultural features, and qualitatively describes the nature of the damage sustained. Several photographs of 

damage to structures and vehicles near the canyon 

mouth are shown in figure 1. Figure 16 shows an overall 

view of the heavily damaged trailer park area. When 

viewing the damage shown in figures 1 and 16, keep in 

mind that the vehicles and structures receiving the 

greatest damage are not visible because they were 

either totally demolished or buried in Lake Mohave. 

Therefore, the photographs give a somewhat conservative view of the effects of the flood. 

Flooding is no newcomer to Eldorado Canyon. Ample 

evidence of past flooding was known to local inhabitants 

(see section on "History"). Recent (1973) efforts by the 

National Park Service to revise and rearrange recreational and residential facilities at the site, reportedly to 

alleviate flood hazards, are a matter of public record. 

THE SETTING 

Eldorado Canyon is an arid, barren, rugged 22.9-mi 2 

area tributary to Lake Mohave on the Colorado River. It 

lies in the Sonoran Desert section of the Basin and 

Range physiographic province as defined by Fenneman 

(1931). The general location ofthe basin and its relation 

to surrounding cultural features is shown in figure 2. 

General basin character is shown in the frontispiece. 

The lower end of Eldorado Canyon is also pictured in 

figure 5. Figure 10, another aerial photograph, shows 

physical characteristics of the Eldorado Canyon terFIGURE 1.-Flood-damaged trailer, truck, and boats. 
THE SE'ITING 3 

36" 

0 5 10 20 MILES 

0 5 10 20 KILOMETRES 

~--------------------------------------------------------------._----~35° 11'4° 

FIGURE 2.-Location of area described in this report. 

minus as well as drainages to the north and south. 

Figure 3 shows the areal extent of the drainage basin, 

its topography, and the main cultural features, and 

delineates major tributary subareas that converge to 

form a single channel only a short distance above the 

canyon mouth. 

The topographic contours of figure 3 show the basin as 

hilly to mountainous in upstream areas. Near its 

mouth, the basin contains a series of east-west-alined, 

canyonlike, wide-bottomed arroyos incised into a moderately steep, eastward-sloping alluvial surface. 

Nelson, a village of only a few tens of permanent 

residents, is in the upstream, northwestern part of the 

drainage. Eldorado Canyon Resort, with a few permanent residents and a highly variable population of visitors, is at the downstream, eastern terminus of the 

basin. 

Eldorado Canyon Resort, within the Lake Mead N ational Recreation area, lies about 50 highway miles 

southeast of Las Vegas. Therefore, the area is a popular 

recreation attraction to many water sport enthusiasts, 

and the canyon-mouth cove provides a major boat land-
Y, 0 1 2 3 4 MILES 

.5 0 1 2 3 4 5 KILO M ETRES 

Slope-area measurement site ;:1 

Field estimates by slopeconveyance method 

FIGURE 3.-Eldorado Canyon basin showing major tributary subbasins, area-altitude distribution, and location of streamflow estimate sites. 

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THE SETTING 5 

ing site for Lake Mohave. Most of the facilities are on 

the main canyon floor, within an obvious flood plain. 

This subjects most residents, employees, and visitors to 

a high degree of risk during major floods. However, 

floods mainly occur during relatively short and infrequent periods of intense rainfall and runoff; the short 

periods of hazard contrast sharply with generally prolonged periods that are undeniably safe. 

HISTORY 

Eldorado Canyon was the site of some of the earliest 

settlements in what is now southern Nevada. It was first 

settled by early miners, prospectors, and mill operators 

in about 1861, and in 1867 Camp Eldorado was established at the canyon mouth on land now beneath the 

surface of Lake Mohave as an outpost of the U.S. Army 

(Casebier, 1970, p. 1 and 19). The canyon has since been 

the site of several mining booms and busts, accompanied by erratic fluctuations in population. During 

recent times, it has been popular mainly as a recreation 

area. 

Eldorado Canyon flooding is the most important aspect of the basin's history related to this report. Numerous floods are rumored to have occurred, but almost no 

known hydrologic data relating to these floods have 

been discovered. A search of available newspaper files 

for information on dates and details of flooding was 

beyond the practical scope ofthis investigation. Several 

persons recently interviewed generally recall floods in 

Eldorado Canyon as follows: Mr. G. F. Gatzke, National 

Park Service employee, and resident of the area since 

1947, recalls flooding in about 1952, 1959, 1960, 1970, 

and 1972 (rral commun., September 1974). Mr. M. Emry, longtime resident (oral commun., September 1974), 

recalls reports of a very large flood in 1904 that caused 

heavy damage to the ore milling works at the canyon 

mouth, and a major flood in 1960 that heavily damaged 

the concessionaire's store-restaurant he operated in the 

canyon mouth (a similar store-restaurant was completely destroyed by the Sept. 14, 197 4, flood). Photographs of flood damage provided by the National Park 

Service (written commun., October 1974) document a 

flood on November 6, 1960, with evidence of severe 

damage and extensive sediment deposits (13,000 yd3, 

according to one of the photograph captions). 

The scanty, incomplete, possibly inaccurate, and gene r a lly unverified reports listed above nonetheless 

categorize at least the canyon mouth area as one that 

has had a number of floods during the relatively short 

historical (about 70 years) period. A search of newspaper files would probably add more floods to those 

listed above. 

BASIN CH ARACTERISTICS 

SLOPE 

The Eldorado Canyon drainage slopes generally from 

west to east. Quantitative data on the area-altitude 

distribution are summarized in table 1. Both figure 3 

and table 1 show that about 70 percent of the basin's 

area is concentrated in the 2,000- to 4,000-ft altitude 

zone. 

TABLE I.-Approximate area-altitude distribution of Eldorado Canyon 

basin 

Altitude Percentage 

zone Area of total 

(ft) (mi 2 ) basin area 

4,000-4,898 2.7 11.8 

3,000-4,000 9.3 40.6 

2,000-3,000 7.0 30.6 

1,000-2,000 3.6 15.7 

647- 1,000 .3 1.3 

Total 22.9 100.0 

Slope data were compiled from U.S. Geological Survey 15-minute 1:62,500-scale Nelson and Mt. Perkins 

quadrangle maps. These data are plotted in figure 4. 

The figure shows that average basin slope and mean 

channel slopes of the three major tributaries are very 

similar, and are generally quite steep. The profiles show 

that all three tributaries have similar, generally uniform slopes throughout their lower 4 mi of reach. This 

uniformity of slope also continues upstream throughout 

most ofthe length ofEagle Wash and Eldorado Canyon; 

Techatticup Wash is noticeably irregular in slope and 

profile above the lower 4-mi reach. The generally continuous steep slopes, and lack of a pronounced profile 

concavity, are anomalous compared with most stream 

systems. All three tributary profiles generally adhere to 

a 300- to 400-ft/mi slope, or greater, throughout most of 

their length, including the terminal reach of Eldorado 

Canyon that carries their combined flow. These consistently steep channels, with only minimal flattening in 

the drainage terminus, are an efficient flushing system 

that produces rapid runoff. 

A view of overall topography including hillside 

slopes, minor tributaries relative to major channel 

slopes, and general landscape character in the lower 

part of the basin is shown in the frontispiece and in 

figure 5. GEOLOGY 

Geology of the drainage basin was mapped by 

Longwell (1963); his map, in condensed form, is also 

reproduced as part of the Clark County geologic map of 

Longwell, Pampeyan, Bowyer, and Roberts (1965). 

These publications indicate that geologic units in the 
6 

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~ 2000 

~ H 

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1000 

HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

Drainage divide, Copper-Eldorado Canyon, 

4,898 ft. above mean sea level 

Drainage divide, Eagle Wash, 

/about 4,200 ft. above mean sea level 

( Drainage divide, Techatticup Wash, 

', ~about 3,525 ft . above mean sea level 

......................... 

' -........... , 

-----.' ..... 

~400ft/mi 

Data from 1:62,500 U.S. Geological· Survey topographic maps 

DISTANCE, IN MILES 

Note: Average basin slope about 410 ft/mi, or 7.8% 

Main tributary average slopes: 

Techatticup Wash, about; 370 ft/mi 1 or 7.0% 

Eldorado Canyon, about 390 ft/mi, or 7.5% 

Eagle Wash, about 410 ft/mi, or 7.8% 

Total basin relief 1 about 4,250 ft. 

Mouth of Eagle Wash 

Mouth of Techatticup Wa;=:h 

10 

Topographic map lakeshore approximately 

630 ft. above mean 

sea level 

11 12 

FIGURE 4.-Longitudinal profiles of main drainage channels. 

FIGURE 5.-Eastward aerial view of lower Eldorado Canyon. Lake Mohave in background. 
THE STORM 7 

basin include extensive exposures of consolidated rocks 

in the highlands of Eldorado basin, and a much smaller 

area of consolidated, semiconsolidated, and unconsolidated alluvium in the lower part of the drainage. 

The consolidated rocks consist of Precambrian 

metamorphic and igneous rocks, some late Mesozoic and 

Tertiary igneous intrusive rocks, and a variety of Tertiary volcanic rocks. They are extensively deformed 

structurally, mainly by a system of north-southtrending faults. Consolidated-rock areas commonly 

consist of bare rock highland masses, or bedrock thinly 

mantled by soil or rock fragments derived from the 

underlying parent material. Steep slopes and lack of 

substantial vegetal cover render the thin soil and rockfragment mantle very susceptible to erosion, particularly by intense runoff such as that which occurred 

during the storm of September 14, 1974. 

Alluvium, as mapped by Longwell (1963, pl. 1), is 

exposed in only the lower 2 mi of the drainage basin. 

Much of this alluvium is consolidated to some degree 

and therefore is fairly resistant to erosion. However, 

unconsolidated alluvium also mantles all the main 

stream channels and many minor stream courses 

throughout most of their length. A thin mantle of unconsolidated alluvium also covers many upland areas. 

Therefore, a large volume of alluvium is concentrated 

along stream channels and on interfluvial slopes 

throughout the drainage where it is available for transport, depending on surface slope, vegetal cover, gravel 

armoring of the deposit surface, and intensity of the 

runoff. 

VEGETATION 

Vegetation is generally very sparse throughout the 

drainage basin. Plants include cholla and barrel cactus, 

creosote bush, some species of yucca, an occasional mesquite tree along arroyo floors, and other unidentified 

species, many of which probably belong to the atriplex 

genus. Greatest plant densities seem to occur in the 

highland areas of the basin (fig. 26), and lowest densities seem characteristic of the downstream areas (figs. 

22-25). General views of vegetation densities in lower 

basin areas are shown in figure 5 and the frontispiece. 

The general absence or scarcity of plants throughout 

the basin increases the speed and eroding ability of 

runoff. 

THE STORM 

The flood of September 14, 1974, in Eldorado Canyon 

was the direct result of an intense convective thunderstorm. A meteorological report of the storm is being 

prepared by the U.S. National Weather Service (Gerald 

Williams, written commun., October 1974). Therefore, 

this report will only briefly summarize known characteristics of the storm to set a stage of basic understanding for the following discussions of flooding and sediment transport. 

Several characteristics of the storm had a critically 

important bearing on the nature of the flooding and its 

resultant catastrophic damage. These characteristics 

include: (1) time of occurrence, (2) total quantity of 

precipitation, (3) precipitation intensity, (4) storm 

track, and (5) nature of storm activity at the mouth of 

Eldorado Canyon during the early period of flooding. 

Rainfall in the upper basin apparently began sometime around 1:00 p.m. (G. F. Gatzke, oral commun., 

September 1974), and the most intense rainfall at Nelson was around 1:45-2:00 p.m. (Thomas Jester, Nelson 

resident, oral commun., September 1974). Jester recalled a total storm duration of about 1¥2 hours at Nelson, 

which generally agrees with observations of A. R. 

Methvan, another Nelson resident. Methvan recorded 

1.9 in. of total storm precipitation (oral commun., September 1974). According to Jester, storm clouds came 

into the Nelson area from the south. T1-" clouds then 

apparently swung around near the north lh_ · ~s of the 

drainage divide when precipitation began, and subsequently passed over Nelson moving in a souL1eastward (downstream) direction during the period of intense precipitation. Several other observers also noted 

the general downbasin movement of the storm center. 

Both Jester and Meth van estimated the period of 

greatest precipitation intensity as less than half an 

hour. Eyewitness accounts near the canyon mouth indicate that greatest precipitation intensity spanned a 

quarter to half an hour. 

Several excerpts from a preliminary draft of the U.S. 

National Weather Service report (Gerald Williams, 

written commun., October 1974) further characterize 

the storm as follows: 

This flash flood was caused by record-breaking rainfall from an 

isolated thunderstorm cell that moved slowly down the drainage 

channel in a way that maximized flooding. * * * Duration of rainfall 

was short, generally less than one hour. Intensities were very highat least three inches per hour and as high as six inches per hour for% 

hour. 

The storm appears to have moved downstream at the rate of about 5 

to 10 miles per hour, coinciding with the movement of surface runoff. 

Highest rainfall intensities and quantities apparently occurred in middle to lower parts of the basin, 

rather than at the higher altitudes. On the basis of 

experience with other recent flash floods inN evada, this 

characteristic is not uncommon, and may be more normal than abnormal. If true, hazard zoning for flooding 

probably should not relate flood potential strictly to 

altitude or differences in altitude, in the generally accepted ((orographic influence" philosophy. 

Eyewitness accounts describing the arrival of the 

very destructive leading edge of the flood front all describe it as being accompanied by intense rainfall, 
8 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

thunder, and hail at the canyon mouth. The time of 

intense destructive flooding and precipitation at the 

canyon mouth is placed by most eyewitness accounts at 

about 2:30 p.m. 

Therefore, four storm characteristics were critical to 

flooding and damage. The storm and flooding occurred 

during the early afternoon on a Saturday, presumably 

at a time of moderate use and occupancy at the canyon 

mouth. The high precipitation intensity, combined with 

the basinwide nature of the storm, yielded large quantities of rainfall during a short period and maximized 

the flooding. The downstream pattern of storm movement caused intense rainfall and runoff to be superimposed on downstream flood waves, compounding the 

peak intensity of surface runoff. Finally, the intense 

rainfall and hail at the canyon mouth probably caused 

people to run for or remain under shelter rather than 

leave the canyon floor. 

RUNOFF 

FLOW RATES 

Peak flow rates are important to the process of understanding the hydrology of flash flooding, and to help 

categorize different flash floods according to magnitude 

and intensity. At Eldorado Canyon, the major damage 

to lives and property was caused by the leading edge of 

the flood runoff. Peak flow apparently followed, rather 

than coincided with, the initial surge of the flood. Therefore, peak flow estimates probably do not bear directly 

on damage and casualties. This is not always the case in 

general flooding or even in flash flooding, where peak 

flow can be a more important factor with regard to 

human losses. Peak flow rates are also important when 

establishing design criteria to cope with future floods. 

Peak flow rate is one of the few hydraulic parameters 

which generally can be computed or estimated with 

reasonable accuracy after the flood has passed. Therefore, we attempted to assess peak flow rates at Eldorado 

Canyon. 

The peak discharge was computed for the main channel just above the trailer parking area (fig. 15 and table 

2), using the standard U.S. Geological Survey indirect 

slope-area method (Dalrymple and Benson, 1967). This 

technique generally gives reasonable results when prevailing flow conditions are within the limitations for 

which the technique applies. Flow conditions in Eldorado Canyon may not have been ideal for proper application of the slope-area method; therefore, the peak 

flow computed may be considerably in error. Some factors that may have caused serious errors in the measurement include: (1) unsteady flow, (2) abnormally 

high sediment concentrations, causing high fluid viscosity, and (3) a cross-sectional flow area, at the time 

high-water lines were deposited, that differed from the 

area determined later at the time of the indirect measurement. These factors are generally influential to varying degrees in peak-flow measurements of most, or all, 

flash floods in the desert southwest. Nonetheless, the 

slope-area method is the best available technique. 

The slope-area method was applied to a situation 

where steady-state flow may not have been dominant;, 

however, because the state of flow was unknown, a 

steady-state condition was assumed. Very high sediment concentrations were apparently associated with 

the initial flood surge (see section titled ((Sediment 

Transport Characteristics"), but concentrations were 

probably much lower during later peak flows. In any 

event, high water lines, which provide the key basic 

data for slope-area determinations, were obviously 

created by flow much more dilute than a viscous 

mudflow. 

After considering the factors discussed above, the 

76,000 ft3/s computed is the best estimate available at 

present. The peak discharge plots close to a curve developed by Matthai (1969) for maximum discharges in 

relation to drainage areas in the United States (fig. 6). 

There are at least two indications the estimate may be 

too high. (1) The mean velocities calculated for the two 

downstream cross sections of the slope-area measurement were 34 and 39 ft/s. These exceed the known mean 

TABLE 2.-Summary of hydraulic data resulting from peak-flow estimates 

Estimated Measured Estimated Approximate Estimated 

Determination type peak cross-sectional mean tributary unit 

and location1 discharge area velocity area runoff 

(ft3/s) (ft2) (ft/s) (mi2 ) [tft3/s)/mi2] 

Slope-area method 

Eldorado Canyon 

below Eagle and {3,030 {25 Techatticup Washes 76,000 (

2 ) 2,230 ( 2 ) 34 22.8 3,300 

1,920 39 

Slope-conveyance method 

Eldorado Canyon 

above confluence with Eagle 

and Techatticup Washes 24,000 1,010 24 13.0 1,800 

Eagle Wash near mouth 25,000 807 31 4.5 5,600 

Techatticup Wash near mouth 11,000 421 26 3.2 3,400 

1Measurement sites shown in figure 3. 2Values for individual cross sections. 
RUNOFF 9 

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1L-~~~LL~~---L~-L~~ll---~-L~~~ 

1 10 100 1000 

DRAINAGE AREA, IN SQUARE MILES 

·FIGURE 6.-Maximum water discharges in relation to drainage areas 

in the United States. 

velocities, and most point velocities in natural channels 

except for some flood waves after dam failures. (2) At the 

time high water lines were created, an unknown quantity of sediment was passing through the slope-area 

reach as bedload. This bedload covered the channel floor 

to some unknown depth and thereby reduced the crosssectional area if minimal channel scour is assumed to 

have prevailed at that time. The possible error in crosssectional area would thereby have caused an indeterminate error in the peak flow estimate. 

Field estimates were made of peak flow rates in the 

lower reaches of the three major tributaries, above the 

slope-area site, using the slope-conveyance technique. 

This technique is less accurate than the slope-area 

method. Results of these estimates are also shown in 

table 2. If the slope-conveyance estimates are added 

together, and their sum is adjusted for assumed flow 

pickup between these measurement sites and the 

slope-area site, a peak flow estimate of 70,000 to 80,000 

ft3/s is indicated. This mathematical approach is justified only if the peak flows of the tributaries contributed to the main trunk system with the proper timing 

to allow direct summation. Such a situation would normally. be unlikely; however, the nature of this storm, 

with its downstream movement and the apparent occurrence of greatest rainfall intensities in the lower 

parts of the drainage basin, tend to favor a cumulative 

effect from the tributary peaks. 

Flow velocity can be estimated in the canyon constriction above the site of the destroyed restaurant (fig. 12), if 

the estimated 76,000-fP/s peak flow is assumed to have 

occurred at that location. The high-water profile and 

preflood topographic map suggest an average flow depth 

of about 20 ft within this cross section. For this depth, 

the cross-sectional flow area would have been about 

1,800 ft 2 . The resultant mean velocity would have been 

about 42 ft/s, similar to velocities in the slope-area reach 

(table 2). 

The flow rate and velocity of the damaging initial 

flood surge at Eldorado Canyon cannot be determined 

because later flow apparently erase,d high water lines of 

the initial surge. The character and effects of the initial 

surge are discussed in greater detail in following sections. 

FLOOD WAVE CHARACTERISTICS 

Specific details of the flood waves are of special interest because they caused most of the property damage 

and apparently were instrumel}tal in most of the 

deaths. Dramatic descriptions by eyewitnesses of the 

arrival of the initial flood wave are included in the 

section entitled ~~sediment Transport Characteristics." 

However, the intensity of local runoff near the canyon 

mouth was apparently impressive prior to the arrival of 

the first damaging flood pulse. Eyewitness John Gallifent observed heavy runoff from his south-facing trailer 

window. The trailer was parked along the north canyon 

wall in the area just downstream from the point where 

the highway access road descends to the canyon floor 

(fig. 12). Gallifent became alarmed when he noted abnormally large flows of water pouring into the canyon 

from numerous rills and small gullies along the south 

canyon wall. He concluded that such heavy flows from 

minor tributaries of minimal drainage area foretold 

even greater runoff from upstream. He had just enough 

time to escape afoot to higher ground. Lemuel 

Washington also observed local runoff on the canyon 

floor near the canyon mouth prior to arrival of the initial 

flood surge. He characterized it as na good stream*** 

like a small river." Mrs. Kirby L. Koop described the 

local runoff along the canyon floor as knee- to thighdeep before the first major wave arrived. 

Kirby L. }\oop watched the approach of the initial 

flood surge from near the icehouse area (fig. 12). He first 

saw it at a distance of about 100 yd. He recalled the dull 

thuds of cars caught up· in the surge striking the canyon 

walls. According to Koop, when the mass of debris and 

water arrived at the preflood shoreline of Lake Mohave, 

it possessed such momentum that it appeared to ~~hydroplane" over the lake surface as far as the boat dock 

gangway (a distance of 100 to 150ft, scaled from fig. 12). 

The mass then seemed to fall vertically into the lake. 

Lemuel Washington's recollection is somewhat different. His statement to theN ational Park Service says, 

~~***the wall of muck appeared to go under when it hit 

the water, causing a swell of water at the surface. Then I 
10 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

saw boats floating, bouncing, cracking, and saw a station wagon come to the surface and go back again." 

Both Washington and Koop described great turbulence as the flood flow entered the lake. Washington 

mentioned~~* * * the up-surge* * * coming back in full of 

debris." Koop's statement to the National Park Service 

described a truck in the flood flow ramming and breaking the boat dock. He said that the flood-surge turbulence then ~~* * * started to suck or pull the rest of the 

dock, boats, and all back into the oncoming water." 

Koop continued, H* * * a trailer* * * hit the lake, it was 

ground up. There were two boats trying to get out, one 

boat with four persons and one boat with one man in it. 

The force of the water pulled these boats back into the 

shore, pulled them stern first down and ground them 

up." Both accounts suggest a powerful destructive undertow near the lakeshore. 

The mouth of Eldorado Canyon during the flood is 

shown in figure 7A, as photographed by Kenneth E. 

Beales of Las Vegas, Nev., during late stages of the flood 

recession. The same general view, about 2 weeks later, 

during excavation and cleanup of flood sediment deposits (fig. 7B), provides perspective on the approximate 

depth of flow at the time of Beales' photograph. 

J. P, Monis and P. A. Glancy, U.S. Geological Survey, 

reconnoitered the east shore of Lake Mohave on Septem~r 19, 1974~ for evidence of wave action caused by 

the flood surges entering the lake. Figure 8 shows the 

best noted evidence of possible flood wave action, at the 

base of a large sand dune across Lake Mohave about half 

a mile east and slightly south of the Eldorado Canyon 

mouth. The dune and its location relative to Eldorado 

Canyon are shown in the upper right part of figure 15. 

The horizontal cut in the sand above the flood debris (fig. 

8), that was deposited before the lake was purposely 

drawn down to aid search-and-rescue operations, 

suggests a maximum wave height of about 1% ft. However, the horizontal cut may have originated from a 

higher preflood lake stand. In any event, no known 

evidence was observed of flood wave action greater than 

about 1% ft. 

Apparent response of the stage of Lake Mohave at 

Davis Dam, about 35 mi downstream from Eldorado 

Canyon (fig. 2), to the flood wave is shown in figure 9. 

The figure indicates that lake stage rose approximately 

0.45 ft shortly after 2:30p.m. the day of the flood. 

RUNOFF VOLUME 

Total storm runoff into Lake Mohave was roughly 

estimated by the U.S. Bureau of Reclamation as about 

2,000 acre-ft (G. B. Freeny, oral commun., 1974). This 

estimate was made on the basis of apparent change in 

contents of Lake Mohave caused by inflow and direct 

precipitation on the lake, and adjusted by preflood and 

postflood reservoir release trends. Aerial reconnai~­

sance of the general area adjacent to Eldorado Canyon 

basin affirmed that the major share of inflow to Lake 

Mohave probably came from Eldorado Canyon. The 

generally undisturbed character of channel-bottom 

vegetation shown in figure 10 supports the conclusion 

that there was no heavy runoff in areas adjacent to 

Eldorado Canyon. Therefore, the flow to the lake from 

Eldorado Canyon itself was estimated at about 2,000 

acre-ft. Figure 11 shows an estimated hydrograph of 

runoff to the lake from Eldorado Canyon. This hydrograph was constructed from the following data: (1) 

known zero flow before and after the flood, (2) an estimated peak flow rate of about 76,000 ft3/s, (3) an estimated total duration of flow as described by eyewitnesses, and (4) the general shape of hydrographs for recorded flash floods in the same general hydrologic are&. 

Runoff volume as determined from the hydrograph is 

also about 2,000 acre-ft. 

MEASURED STREAMBED AND HIGH-WATER PROFILES 

Figures 12, 13, and 14 show locations of flood boundaries, high-water profiles, streambed profiles, and :;1. 

qualitative assessment of damage to some cultural features in Eldorado Canyon. Figure 15 shows the general 

flood plain extent and characteristics just above the 

developed area. The average slope of the profiles in the 

measured reach (fig. 12) is 280 ft/mi. The left-ban~ 

profile through the trailer park area indicates a 2- to 4-ft 

depth of water above the canyon floor (figs. 14 and 16), 

whereas the right-bank profile in the same section is 

defined by one piece of debris found on the vertical wall 

about 16ft above the canyon floor. Assuming that this 

piece of debris actually represents the true water surface along the right bank, the difference in left- and 

right-bank elevations must be explained by the sloshing 

of water from bank to bank (figs. 12, 7A ), and by local 

pileup of water caused by cars and boat trailers in the 

parking area. Downstream from the trailer parking 

area (fig. 14), the left- and right-bank profiles become 

very erratic and indicate water pileup due to the contraction of the reach. The momentum of the flowing 

water forced the water up and over the projecting bedrock ridges. The profiles (fig. 14) show that the water 

surface along the left bank was as much as about 25 ft 

above the canyon floor where the flow was pushed up 

and over the projecting rock ridge. Figure 16 shows the 

contrast between trailers caught within the left-bank 

high water line (damaged) and those on slightly high~r 

ground (undamaged). 

FLOOD FREQUENCY AND MAGNITUDE 

No accurate definition of the recurrence interval fora 

flood peak of 76,000 ft3/s in Eldorado Canyon is possib~e 
RUNOFF 11 

FIGURE 7 .-Mouth of Eldorado Canyon. A , On September 14, 197 4, probably during the late recession of flooding (photograph by Kenneth 

E. Beales, Las Vegas, Nevada). B, On October 1 during excavation of flood sediment deposits. 
12 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

because of insufficient data. However, empirical 

methods being developed from data throughout southern Nevada (D. 0. Moore, oral commun., 1974, and 

Moore, 1974) were used to estimate 10- and 25-year 

flood magnitudes for Eldorado Canyon near the canyon 

mouth. The peak flow estimates for the 10- and 25-year 

flood are 80 and 200 ft3/s, respectively. The 80-ft3/s 

flood, assuming an asphalt channel bottom through the 

trailer parking area (fig. 16) with the surface configuration as surveyed on September 16, 1974 (approximate 

profile stationing 1400, fig. 12), would be about 0.5 ft 

deep with an approximate mean velocity of 6 ft/s. The 

200-fP/s flood would be about 0. 75 ft deep with an approximate mean velocity of 8 ft/s. 

The scanty data and estimates described above 

suggest that a flood magnitude of 76,000 ft3/s would 

apparently have a large but unknown recurrence interval. However, it should be emphasized that flood magnitude and frequency are founded on the theory of probability. This introduces a risk factor. Also, long term 

data for floods in ephemeral stream channels in Nevada 

are very scarce. Therefore, a frequency analysis of major 

floods is based on little factual experience. 

The magnitude of the September 14 flood gives no 

guarantee that another disastrous flood will not occur in 

the foreseeable future. Therefore, a reasonable course 

would be to assume such a flood can and may occur in 

any given year. 

SIMILAR FLOODS 

Areas in southern Nevada and nearby States known 

to have been subjected to high-intensity thunderstorms 

FIGURE 8.-Wave-cut bench (above debris line) along east shore of 

Lake Mohave, possibly caused by flood surges entering the lake. 

SEPTEMBER 14 _J 

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TIME, IN HOURS 

FIGURE 9.-Trace of Lake Mohave stage at Davis Dam, showing approximately 0.45-ft rise. Gage is about 35 mi downstream from 

mouth of Eldorado Canyon. Figure is reproduction of lake stage 

recorder sheet. 

similar to that which struck Eldorado Canyon include 

the following: 

1. An unnamed stream in the McCullough Range 

near Searchlight, Nev., in late August 1971. 

2. Bullhead City, Ariz., area in late summer 1971. 

3. Red Rock Wash near Las Vegas, Nev., on January 

27, 1969, and July 23, 1974. 

4. The McCullough Range between Henderson and 

Railroad Pass, Nev., in 1969 or 1970. 

5. Grapevine Canyon in Death Valley, Calif., on August 14, 1968. 

6. Black Canyon near Wickenburg, Ariz., on September 14, 1964. 

7. Picacho Wash near Imperial Dam, Calif., on September 14, 1974. 

Table 3 summarizes data for some floods in the western United States with peak flow rates per unit drainage area greater than that of Eldorado Canyon on September 14, 1974. 

TABLE 3.- Floods having peak flows per unit drainage area greater 

than that of Eldorado Canyon 

Drainage Peak Unit 

Location areas discharge runoff 

(mi 2 ) (ft3 /s) [(ft" )/mi2 ] 

Bronco Creek near W ikieuf:, Ariz. 20 73,500 3,700 

Meyers Creek near Mitche 1, Ore. 12.7 54,500 4,300 

Trujillo Arroyo near Hillsboro, N.Mex. Sout h Fork Pine Canyon Creek near 6.9 45,000 6,500 

Waterville, Wash. 5.4 25,000 4,600 

Little Pinto Cr eek tributary near Newcastle, Utah .30 2,630 8,800 

Lahontan Reservoir tributary No. 3 

near Silver Springs, Nev . .22 1,680 7,600 

Eldorado Canyon, Nev . 22.8 76,000 3,300 
FIGURE 10.-Vertical aerial photo of the terminal reach ofEldorado Canyon drainage and adjacent drainages on September 20, 1974. Photograph courtesy of Nevada 

Division of Highways. 

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14 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

SEDIMENT 

SEDIMENT DEPOSITS 

Fluvial sediment transport was an important aspect 

of the September 14 flood. The greatest immediate impact of sediment deposition was the practical problem it 

posed for search-and-rescue crews. Sediment deposits at 

the canyon mouth and in Lake Mohave blanketed several acres to thicknesses of up to 12 ft. Much of this 

sediment had to be removed during the search for victims and missing property. Also, excavation of the 

material prolonged and increased lake turbidity near 

the landing and thereby hampered underwater search 

by divers. The cost of removing sediment deposits was 

great, and probably accounted for the major part of the 

search -and-rescue expense. 

The sediment volume accounted for in known deposits 

is estimated to be 54,000 yd3 . Table 4 describes the 

location and distribution of the known sediment deposits; location of the depositional units is shown in 

figure 17. The estimate was made on the basis of postflood configuration of deposits and on some preflood topographic information. Estimates of deposits upstream 

from the preflood shoreline of Lake Mohave probably 

are reasonably accurate because detailed preflood topographic data were available. However, no recent 

preflood bathymetric data were available for the harbor 

or adjacent areas. Some general knowledge of preflood 

water depths is available from observations by the National Park Service staff and others. These sparse data 

are supplemented with estimates of the quantity of 

material actually excavated and removed, as well as 

evidence of depths to apparent preflood lake-bottom 

clays exposed during excavation. 

The 54,000-yd3 estimate does not account for an unknown silt-clay fraction of the total sediment load. This 

part of the load was probably dispersed widely throughout Lake Mohave because of its small particle size and 

inherent slowness of settling. Therefore, the 54,000-yd3 

deposit probably represents a lower limit of total sediment load. 

A reconnaissance characterization of the sediment 

deposit according to particle-size distribution was attempted (extensive sampling and analysis was beyond 

the scope of the study). Six samples of excavated material were arbitrarily collected on September 30, 1974, 

when the large mass of available excavated material 

probably was representative of most of the recoverable 

sediment. Samples were collected by P. A. Glancy (U.S. 

Geological Survey), and standard sieve analyses were 

made by the Materials Testing Laboratory, Nevada 

State Highway Department, Las Vegas. Results of the 

sieve analyses are listed in table 5, and figure 18 pictures the material sampled at each site. Samples were 

collected from piles of excavated sediment dumped upstream from the trailer park area. The piles are clearly 

visible upstream from the access highway in the aerial 

photograph of September 20 (fig. 10). Samples were 

carefully collected to typify the mass of material excavated, and are believed to be generally representative of 

that mass, within limitations imposed by the small 

number of samples that could be collected feasibly. 

On the basis of analytical results in table 5, the sediment excavated from the deposits can be characterized 

as follows: less than 1 percent boulders, about 60 to 80 

percent gravel, about 10 to 30 percent sand, and less 

than 3 percent silt and clay. As described above, the 

silt-clay fraction ofthe sampled deposits probably is less 

than that contained in the total sediment load of the 

flood. 

Seven additional samples were collected from drainage slopes and channel bottoms of Techatticup and 

TABLE 4.-Estimated nonorganic sediment deposits [Data rega rding areal distr ibution a nd e!5lima ted t hickn ess of deposits ma inly prov ided by T. R. Gess, National Park Service E ngineer (oral and writt en comm un., September and October 

1974). All quantities r ounded because of nature of est imates] 

Loca tion of deposits 

Upstream end of pa r k development to upstream edge of boat landing Upstream edge of boat landing 

to preftood shoreline Preflood shoreline to postflood 

shoreline 

Be low postflood la ke surface 

Subtotal 

Somewhere in La ke Mohave beyond · limits of known deposits 

Tota l (rounded) 

Map zone shown in fi gure 17 

2 

3 

4 

Not shown 

Approxima te area 

(acres) 

2.6 

.6 

1.1 

2.3 

6.6 

unknown 

> 6.6 

a Unit weight estima tes we re adopted from data of Hough (1957, p. 30-31). b Mainly mode rately compa cted gravel, sand, and small amounts of boulders and fines. c Loosely compacted sand with sma ll amounts of gravel a nd fines. 

Estimated average thickness 

(ft) 

4.5 

9 

5.5 

unknown 

Estimated volume 

(yd' ) 

13 ,000 

4,700 

16,000 

20,000 

54,000 

d1 6,000 

70,000 

Estimated unit 

weight of 

d(fb}tW)a 

c 100 

Estimated dry weight 

of sediment (tons) 

60,000 

27 ,000 

87,000 

17,000 

100,000 

d DiffCre nce bet we~~ crude estimate of total load transported (70,000 yd3 ) a nd estimate of 

generally known deposits (54,000 yd3 ) . 

e Proba bly very loosely compact ed silt a nd clay wit h some fine sand an d very small amounts of 

medi urn sand. 
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SEDIMENT 15 

80,000 I I I I I I 

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70,000 - -

- -

60,000 - -

- -

50,000 - -

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40,000 r- -

r- -

30,000 1-- -

r- -

20,000 1-- -

I- -

10,000 1--

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0 I I 

0 1 2 3 4 5 

FLOW DURATION, IN HOURS 

FIGURE H .-Estimated flood hydrograph for September 14, 1974, 

near mouth of Eldorado Canyon. 

Eagle Washes and Eldorado Canyon, 2 to 4 mi upstream. 

from Lake Mohave , in an attempt to characterize 

particle-size distribution of sediment subjected to erosion. These samples all exhibited generally similar 

grain-size distribution, averaging about 50 to 70 percent gravel, 25 to 40 percent sand, and 4 to 8 percent 

silt-clay. However, because they represent postflood 

conditions and are not a statistically significant sampling of the overall drainage basin, they may not accuTABLE 5.-Approximate particle-size distribution of sediment samples 

Size 

c I ass 

Small cobbles 

(> 64 mm ) 

Grave l (2-64 mm ) 

Sand <0.062-2 mm) 

Sill·clay (<0.062 m.m ) 

Approx· 

imate U.S. size of standard 

opening sieve (mm.) EG-1 

100 4 in 

75 3 in ----

50 2 in 100 

37.5 l'h in 95 

25 1 in 89 

19 % in 81 

12.5 1h in 71 

9.5 % in 63 

4.75 No.4 48 

2.00 No. 10 28 

1.18 No. 16 18 

0.425 No. 40 7 

0.300 No. 50 6 

0.150 No. 100 3 

0.075 No . 200 3 

Percent pa~ f:l ng seive, by weight 

Sample number 

EG-2 EG-3 EG-4 EG-5 EC-6 

100 ---- ---- 100 ---- 83 ---- 100 97 ----

79 100 96 72 ---- 75 99 92 64 100 

65 95 82 55 97 

58 91 73 46 91 

19 82 59 38 80 

43 73 51 32 72 

31 53 35 21 50 

18 33 20 12 27 

12 23 15 9 17 

4 12 8 5 6 

3 11 7 4 5 

2 8 5 3 3 

1 6 4 3 2 

rately represent sediment eroded, transported, and deposited by the flood. As with the flood deposits sampled, 

the silt-clay component of the upstream material may 

be underrepresented. 

However, the silt-clay fraction might be assumed to 

have made up less than one-fourth the total load, because sand was considerably less prevalent than gravel 

in the material recovered. Therefore, the total sediment 

load transported by the flood is roughly estimated at 

70,000 yd3 (purposely rounded to one significant figure) 

which allows a crude, but necessary, adjustment for the 

otherwise unaccounted fine-grained load component. 

Table 4 shows data for all known and assumed sediment 

deposits, except those for floating debris. The table also 

includes estimates of sediment weight for individual 

deposits. Total weight of all generally nonorganic sediment is estimated about 100,000 tons. 

Particle-size distribution, by weight, of the estimated 

sediment load (less organics) can be roughly approximated from the data of table 4, using some arbitrary 

assumptions, as follows: boulders, less than 1 percent; 

gravel, about 40 percent to 60 percent; sand, about 20 

percent to 40 percent; and silt-clay, about 10 to 25 percent. 

Large boulders, common constituents of many intensive floods in the southwestern United States, were generally absent in the September 14 flood deposits. An 

occasional boulder was noted during excavation or observed in piles of excavated material. Selected examples 

of the measured triaxial diameters, in feet, of· these 

observed boulders are as follows: 3 x 1.5 x 1.2; 3 x 1.5 x 1; 

2.8x 1.3x 1.5; 2x 1.5x0.5; 1.8x 1.1x0.9; and 1.5x 1 x0.8. 

Another large boulder unearthed in the deltaic material 

(5.4x3.7x3.2 ft) may well have been deposited by some 

previous runoff event. 

Figure 17 shows the approximate area of new land 

surface created in the harbor as a result of sediment 

deposition. New land surface was delineated on the 

basis of the preflood topography shown in the figure and 
16 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

postflood (Sept. 18 and 20, 1974) aerial photographs 

supplied by R. J. Gregory, Director, Nevada Civil Defense and Disaster Agency, and the Nevada Highway 

Department (fig. 10). Land surface was increased by 

about 1.1 acres, and the harbor shoreline was extended 

lakeward about 350 ft. 

The in-place character of sediment deposits at the 

canyon mouth was only rarely disclosed during excavation because most steep slopes created by digging 

.,, slumped almost immediately. Figure 19 pictures a rare 

near-vertical exposure of upper beds of material deposited along the right canyon wall near the shoreline of 

Lake Mohave. The photograph shows stratified sand 

and gravel probably deposited during the runoff recessiOn. 

Floating debris, mostly manmade artifacts and uprooted vegetation, temporarily covered a large area of 

harbor surface adjacent to the newly extended land surface. The extent of this debris is generally shown by 

figures 17 and 20. Most floating debris was restricted to 

about 1.1 acres of water-surface area by the afternoon of 

September 15 (fig. 20). A very rough estimate of floating 

debris is about 4 acre-ft, using the area shown in figures 

17 and 20 and assuming an average 3.to 4ft thickness of 

deposits (T. R. Gess, oral commun., 1974). 

Removal of the floating debris (fig. 20) required about 

a week's labor, but the efforts yielded the bodies ofthree 

flood victims (fig. 17). The pulverized debris and the 

nude bodies testify to the tremendous energy expended 

by the flood in the terminal reaches of Eldorado Canyon. 

SEDIMENT TRANSPORT CHARACTERISTICS 

The scarcity of boulders in deposits from the September 14 flood seems anomalous when field examination of upstream areas shows a large number of boulders 

on many hillslopes and in numerous small tributary 

channels. However, field reconnaissance shows that the 

boulders are characteristically scarce in the postflood 

HEAVILY DAMAGED TRAIL 

PARK1NG AND CABIN AR 

Base map furnished by the National Park Service 

FIGURE 12.-Flood boundaries, streambed 
SEDIMENT 17 

surface deposits of Eldorado Canyon and Eagle Wash, 

but Techatticup Wash contains a greater number of 

boulders scattered along its main channel. It is assumed 

preflood channel deposits were similar in particle-size 

distribution. Therefore, boulders observed on hillslopes 

and in small channels presumably were not subjected to 

streamflow intense enough, on or recently prior to September 14, to move them to the main channels where 

velocities on September 14 probably would have been 

adequate to have transported many of them long distances. As a result, the flows that collected in the three 

main drainage channels (Eagle and Techatticup 

Washes and Eldorado Canyon) transported only the 

available material, which was apparently dominated by 

gravel. 

Evidence of at least some large-boulder movement in 

Techatticup Wash is suggested in figure 21. The boulders shown mantling the channel floor are in the extreme west center of sec. 5, T. 26 S., R. 35 E., just 

upstream from the waterfall ofTechatticup Wash. They 

lie in a locally wide section ofthe wash, suggesting that 

they were deposited bee: use of rapidly decreasing flow 

velocities associated witu the channel expansion. Most 

of them were probably in motion during the September 

14 flood. 

An exceptionally large boulder that may well have 

moved some distance during the flood is shown in figure 

22; its dimensions are 6 x 4 x 2.5 ft. Figure 24 shows a 

boulder lodged under the front bumper of a car abandoned during the flood in the lower reaches of Eagle 

Wash. The boulder (dimensions 2 x 1.5 x 1 ft), overlying 

a live bush, obviously moved during the flood. 

The rough estimate (70,000 yd3 ) of the total nonorganic sediment deposited at or near the mouth of Eldor ado Canyon, plus the estimate of inflow to Lake 

Mohave from Eldorado Canyon, allow reasonable speculation on additional sediment-transport characteristics 

of the September 14 flood. The estimated dry weight of 

LOCATION OF VELOCITY AND CROSS-SECTIONAL 

200 400 

Profile stationing, in feet 

Outer limits of flood 

through profile section 

iot e : Profiles shown, at different scales, in fj_g -

ures 13 and 14. 

Sl ope area sile between s lations 86 and 642, 

200 400 600 800 FEET 

0 50 100 150 200 METRES 

profile line, and specific cultural features. 

DISCUSSED IN TEXT 

ICEHOUSE AREA 

(MODERATELY DAMAGED) 
18 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

sediment deposits is shown to be about 100,000 tons in 

table 4. Sediment deposits below the postflood lake surface are equivalent to about 12 acre-ft of solid rock on 

the basis of estimated volume and unit weight of the 

deposits. Pure water inflow, dismissing organic debris, 

wasabout 1,988 acre-ft (2,000 acre-ft total inflow minus 

12 acre-ft of rock) or about 2, 700,000 tons. Therefore, 

the overall water-sediment mixture delivered to the 

terminal reaches of Eldorado Canyon was waterdominated (about 3¥2 percent sediment, by weight). The 

mean sediment concentration for the total watersediment mixture, not counting organics, may have 

been about 36,000 mg/1 (milligrams per litre). Recognizing limitations on estimates of total streamflow and 

sediment, as well as unknown weight of organics, a 

mea,n total-sediment concentration of 30,000 to 40,000 

mg/1 seems reasonable. This statistic also indicates that 

sediment transport during the flood was important, but 

the material delivered to the canyon terminus was 

nonetheless a water-dominated mixture. The water-

................ _ 

''-· ............. ·--.... ...._ 

-·-·-. -....... ........... 

-·"· 

sediment composition probably varied greatly with 

time and location, and probably was rarely equal to the 

mean concentration. 

Several persons witnessed the flood flows in the vicinity of the boat landing at the canyon mouth. Lemuel 

Washington of Las Vegas, Nev., and Kirby L. Koop of 

Placentia, Calif., both describe the initial flood surge as 

being very heavily laden with sediment having a consistency generally equivalent to freshly mixed concrete 

(Washington) and not quite as viscous as freshly mixed 

concrete (Koop). Both witnesses describe the initial flow 

definitely as a vertical wall of water mixed with sediment and manmade artifacts. Unfortunately, both witnesses were observing the oncoming flood along a line of 

sight parallel to the direction of movement, which is a 

disadvantageous position from which to accurately 

judge whether the leading edge was near-vertical. It is 

certain, however, that the mixture arrived as a sudden 

onrush of streamflow carrying a very high concentration of sediment; that it had picked up a conspicuous 

L EFT BANK 

'· .......... ________ . .-...... 

0 

'·, 

·-·-·-·-.......... 

·-..... --... 

'-·-. (HIGH- WATER LINE 

-·-·" ·................. /'• 

·-./ '·-· ( STREAMBED 

PROFILE STATIONING, IN FEET 

200 400 600 soc 

......... ........ .......... 

·-·-·---·-·-............... _._ RIGHT BANK 

·-·---·-... .................. 

·-·-·-·-..., f HIGH-WATER LINE 

--·--·-·-·-·-·--·-.1 

Note: Map view of profile locations shown at 

different scale in figure 12 

1000 

FIGURE 13.-Profiles of peak discharge high water lines and streambed at slope-area site in Eldorado Canyon. 
SEDIMENT 19 

array of manmade artifacts from the upstream parking 

lots, trailer village, and campground facilities, and that 

it probably contained an appreciable amount of uprooted vegetation. Koop further describes the leading 

edge of the onrushing mixture as raining or spraying 

out gravel as large as several inches in diameter. He 

characterized the flow as dark brown in color, but indicated that the oncoming flow was not audible. Mrs. 

Koop, also an eyewitness with her husband, described 

the initial flow as so abrupt that at first she thought a 

dam must have burst somewhere upstream. Mr. Koop's 

impression of the oncoming mass of material was described in a statement to National Park Service personnel, as follows: 

When I got around the small nose which was behind the block-ice 

machine and started walking toward the coffee shop, I looked up for a 

second. I became disoriented because I thought the mountain had 

moved. Then I realized what we were seeing was a wall of water about 

20-25 feet high stacked with cars, trailers, etc., smash into the coffee 

shop, post office, and they exploded like there was dynamite inside. 

Figure 23 shows the location of high water lines just 

upstream from the coffee shop site, where the canyon 

narrows abruptly. Flow depths at this point, approximately where the oncoming surge of water was observed 

... 

"' 

~ ... 

740 

~ 720 

t. 

~ \, 

~ .......... ..._. 

-·--·- HIGH-WATER LINE ~·~·-·~. ) -........... __ 

by Koop, generally support his estimate of surge height. 

Lemuel Washington, in his statement to theN ational 

Park Service, described the approaching streamflow as 

follows: "It first looked like a dark heavy cloud of dust. 

Looked like a solid wall moving down. As it came down, 

every vehicle was pulled into this muck. I saw 4 to 6 

vehicles in the debris. The wall of muck appeared to go 

under the lake when it hit the water, causing a swell of 

water at the surface." Washington indicated that he 

first sighted the approaching flow when it was above the 

trailer court; at that point, it appeared as an approaching wall about 6 to 8 ft high. Koop apparently first 

observed the surge as it was entering, or had just entered, the canyon narrows immediately upstream from 

the coffee shop (restaurant). 

The foregoing accounts strongly imply that sediment 

concentration of the initial flood surge was considerably 

higher than the estimated mean concentration of 

30,000-40,000 mg/1. The statements generally characterize the onrush as a highly charged debris flow that 

may have had the general consistency of a mudflow. 

Koop (oral commun., 1974) described the initial "wave" 

as being followed by several wavelike surges, none of 

LEI-'T BANK 

WATER PILEUP CAUSED BY CONTRACTING z 

CHANNEL, FLOW OVER PROJECTING BED- S ROCK LEDGES, AND DIRECTION OF FLOW 3 

5 

~ ~ ~ "' 

~ 

-............ _____ _ -- __ ,........---· ................... 

< 700 -·-........... . _ __ .J·-· I ~ ;, 

,;; 

0 680 

~ ;;j 

660 

740 

"' 

~ 700 

~ ... 

;, 

i 680 

5 

~ 

660 

{ 

TRAILER HOMES 

-~' 

1200 1400 1600 

VERTICAL CLIFF 

(HIGH-WATER HARKS IMPOSSIBLE TO LOCATE) 

" 

'-DEBRIS ON VERTICAL WALL 

APPROXIMATE AREA OF CAR AND BOAT TRAILER PARKING 

PROFILE STATIONING, IN FEET 

1800 

_} 

2000 2200 

RIGHT BANK 

.r-cONCESS I~!~R~~ S HOME --. 

·,, 

" \ 

FIGURE 14.-Profiles of peak discharge high water lines and streambed, Eldorado Canyon Resort. 

~ 

2400 

I 
20 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

FIGURE 15.-Downstream (eastward) aerial photograph of Eldorado Canyon t erminus taken September 17, 1974. Boat storage area to right. 

Horizontal lines show approximate slope-area site. 

FIGURE 16.-Heavily damaged trailer park at Eldorado Canyon Resort. Afternoon, September 19, 1974. 

which he observed to noticeably recede before a subsequent surge further increased the flow depth. If correct, Koop's description may explain why no mudline 

marked passage of the initial surge. 

Neither the Koops nor Mr. Washington observed any 

movement of large boulders during the flood. 

The foregoing description of sediment transport 

characteristics of the initial flood surge suggests that 

the moving flood front tended to pick up debris from the 

stream channel during its flow downstream. This progressive debris pickup of the leading flow edge probably 

created a front laden with sediment that moved rapidly 

but slower than the water behind it. The result was the 

abrupt arrival of a tremendous mass of debris and 

water. This type of debris-laden flood front has been 

described to the authors by several eyewitnesses of 

other flash floods. Field evidence of numerous other 
SEDIMENT 21 

similar floods in Nevada also suggests this debris-laden 

front is a common characteristic of flash flooding in this 

environment. However, somewhat less common, in our 

experience, is the apparent increasing stage of more 

dilute streamflow following the initial debris-laden 

surge. This characteristic may be related to very intense 

flash flooding in a relatively large watershed having a 

complex major-tributary system wherein peak flows are 

more likely to occur sometime after the initial surge. 

This appears to have been the situation at Eldorado 

Canyon. 

In summary, throughout the terminal reaches of Eldorado Canyon below the junction of the three major 

washes, the sediment transport characteristics of the 

major floodflow appear to have been generally as follows: (1) the initial surge was highly charged with sediment, artifacts, and uprooted vegetation; (2) the initial 

surge was followed by several succeeding surges, some 

of which were of higher stage than the initial surge; (3) 

surges following the initial onrush probably had a generally lower sediment concentration than the initial 

surge. 

Dr. J. H. Sessums, Bishop, Calif., observed the flooding from quite a different vantage point, in Eagle Wash 

about 2 mi upstream from the trailer court (oral commun., 1974). Sessums was driving up Eagle Wash during the intense rain and hailstorm. His first encounter 

with floodflow in Eagle Wash came as his moving car 

met several small pulses of flow. These pulses cumulated and increased the overall depth to a degree that 

prompted him to abandon his car. He did not observe 

any initial "wall" of water in Eagle Wash, nor any 

debris-clogged initial flow surge. He described the 

runoff as turbid, but definitely not a mudflow. 

Flow surges continued and added to the stream stage 

until Sessums' car was swept downstream about a mile. 

It was subsequently deposited on the floor of the wash by 

the receding streamflow. Figure 24 pictures Sessums' 

car on the afternoon of September 20 at its final resting 

place. The boulder deposited in front of the car was 

discussed earlier (p. 16). The car paint was unscratched 

in spite of the fact the car was partly inundated by 

rapidly flowing turbulent water for a substantial period 

of time. The flow apparently did not abrade or damage 

the paint surface, nor were there any visible signs of 

damage by large moving rocks. This evidence suggests 

that sediment transport in Eagle Wash apparently was 

dominated by gravel-size bedload that passed beneath 

the painted surface of the auto. The apparent dominance of gravel-size sediment agrees with the particlesize data of table 5. Absence of any scouring ofthe paint 

surface by suspended sand remains somewhat mysterious to the authors. 

Sessums described his recollections of peak-flow conditions from his vantage point along Eagle Wash as a 

flow section 400 to 600 ft wide and about 4 to 6 ft deep. 

His description of the mobilization and transport of his 

car by the streamflow might provide useful evidence 

regarding the apparent absence of vehicles among the 

coarse-grained deposits at the mouth of Eldorado Canyon. He observed his car being initially mobilized by a 

surge of flow that at some critical depth caused the front 

of the auto to pitch upward like the prow of a boat and 

begin moving downstream. Thereafter, the car appeared to bob along in the flow like a cork, aided by 

buoyancy caused by air trapped inside the body. This 

buoyancy may also have prevented prolonged submergence with associated paint abrasion. If cars near 

the canyon mouth were likewise buoyed up by entrapped air, they would be less likely to settle with 

coarse-grained sediments and would more likely be 

found considerably farther lakeward, among the finergrained deposits. 

The fact that Sessums' car moved downstream only 1 

mi before being set down attests to the very short period 

of peak flow in Eagle Wash. 

EROSION 

Postflood air and ground reconnaissance of the drainage basin disclosed abundant evidence of fresh erosion 

of rills, small tributary channels, and main channels 

throughout most of the basin. Generally, drainage areas 

upstream from main-channel reaches that experienced 

heavy runoff are relatively devoid of intensive rillerosion scars. This relation between rill erosion and 

estimated peak flow rates in main channels generally 

agrees with apparent areal trends of total precipitation. 

All data suggest that precipitation, runoff, and erosion 

apparently were lowest in the headward parts of the 

basin. Intensities generally increased in a downstream 

direction and probably reached a maximum in the lower 

one-third of the basin. 

The most intense observed rill erosion was in a lower 

basin area (SEY4NW114 sec. 8, T. 26 S., R. 65 E.) shown in 

figure 25. In contrast, rill erosion is virtually absent in 

many parts of upstream areas such as that shown in 

figure 26, photographed approximately in the N¥2 sees. 

8 or 9, T. 26 S., R. 64 E. Figure 26 shows that a minor 

amo~nt of main-channel streamflow and erosion did 

occur at the site, in spite of the lack of flow evidence on 
Approximate locations of 

recovered objects: 

A - Bodies 

B - Park ranger's pickup 

C - Tops of vehicles located in 

underwater sediment deposits 

1 

Base map furnished by the National Park Service 

2 

[]ill 

~ 

E X P L A N A T I 0 N 

Sediment deposits above 

boat landing 

Sediment deposits on 

boat landing 

New land surface resulting 

from de·position 

Sediment deposits below 

postflood lake surface 

Floating debris on ·afternoon of September 15 

2 

Note: Flood sediment deposits extended 

l and surface about 350 feet 

beyond pr eflood shoreline a nd 

increased land surface by about 

1.1 acres. Area of floating 

debris also about 1.1 acres. 

Shoreline elevation data for 

Sept. 20, 1974 and Sept. 

14, 1974, rounded to nearest foot, 

furnished by G.B. Freeny, U.S. 

Bureau of Reclamation (oral 

commun., October 1974). 

Approximate shoreline on Sept. Approximate shoreline of 

Sept. 18-20, 1974, 

water-surface a ltitude 

±630 feet (see fig.lO). 

200 

1974 just before flood, water-surface 

altitude ±632 feet. 

0 200 400 600 FEET r ,,,,,,,., r r r r I 1 I 1 I I I I ------1 

50 0 50 100 150 METRES 

FIGURE 17.-Sediment deposits and locations ofprefiood and postfiood shorelines. 

tv 

tv 

::r: 

><: 

t::) 

::0 

0 

t-' 

0 

.Q 

><: 

0 

"rj 

trl 

t-' 

t::) 

0 

::0 

;J> 

t::) 

0 

0 

;J> 

z 

><: 

0 

z 

z 

trl 

:< 

"rj 

t-' 

0 

0 

t::) 

0 

"rj 

en 

trl 

~ trl 

~ 

to 

trl 

::0 

..... 

• >~>­

..... 

<!:> 

..., 

>!>-
SEDIMENT 23 

FIGURE lB.-Excavated sediments quantitatively described in table 5. 
24 HYDROLOGY OF ELDORADO CANYON, NEV. , FLOOD OF SEPTEMBER 14, 1974 

FIGURE 19.-Stratified sediment deposited at the mouth of Eldorado 

Canyon. Note alternating layers of mixed particle sizes with only a 

general impression of coarsest sediment in lowest strata. 

the adjacent hill. Figure 5, an aerial view oflower basin 

terrain, shows distinctive rill-erosion scars. Intensive 

rill erosion is also clearly visible in figure 24, a photograph taken in NE14 sec. 9, T. 26 S., R. 65 E., lower Eagle 

Wash. Large amounts of sediment derived by rill erosion were delivered to main channels and transported 

further. 

Much of the sediment transported by the September 

14 flood, particularly the coarser grained fraction, probably was derived by erosion from within the larger 

stream channels. Evidence of local vertical scour, generally less than 1 ft in depth, was common. Deeper scour 

may have occurred in some places, followed by later 

redeposition. Figures 15, 22, and 24 show traces of 

rooted vegetation within high-intensity flow reaches. 

This evidence precludes any overall deep scouring. 

Severe lateral scour did occur in some places along 

major channels. Figure 27 shows examples of highway 

damage caused by this type of erosion. 

Although the flood of September 14 is believed to have 

been the most severe in Eldorado Canyon during h istoric times, field reconnaissance disclosed some evidence of even more intensive erosion locally in at least 

one drainage tributary. Figure 28 shows a severe erosion scar on the steep southwest-facing slope of a hill in 

about SW14SW14 sec. 1, T. 26 S., R. 64 E., tributary to 

Techatticup Wash. The deeply furrowed channel is laterally bounded by windrow-shaped ridges of sizeable 

boulders that indicate very intense runoff and erosion. 

Vegetation growing within the furrowed channel and 

among the deposits indicate this feature substantially 

predates the September 14 flood. It does, however, show 

that other violent runoff events have occurred during 

the past within the drainage. The hillslope in the 

background of figure 28, across the highway, shows 

additional severe rill erosion of the September 14 flood. 

ESTIMATED LANDSCAPE DENUDATION 

The estimate of total sediment deposited during the 

flood can be used to describe the effects of the flood in 

terms of overall landscape denudation. If the 100,000-

ton estimate of deposits (table 4) is converted to a solidrock equivalent and prorated uniformly over the 22.9-

mi2 drainage basin, a mean basin denudation rate of 

about 0.002 ft is indicated for the flood. However, if the 

majority of eroded material was derived by mainchannel erosion of temporarily stored alluvium, prorating the sediment over the total basin would not be 

meaningful. Another approach, assuming dominant 

main-channel supply of detritus, would be to prorate the 

total sediment volume uniformly over the total length of 

mainstem channel. The sediment deposits above the 

postflood shoreline are about 34,000 yd3 . The sub-lakesurface deposits (36,000 yd3 ) can be reduced to a landsurface volume equivalent of 25,000 yd3 by ratios of 

their unit weights. The resultant volume of equivalent 

main-channel deposits is about 60,000 yd3 . Dividing 

that volume by the sum ofmain-channellengths (25 mi) 

derived from figure 4 (Eldorado Canyon, 10.8 mi; Eagle 

Wash, 7.4 mi; and Techatticup Wash, 6. 7 mi), the uniform channel-denudation rate would be about 2,400 

yd3/mi. Further, assuming the average channel width to 

be 100 ft, uniform vertical scour needed to supply the 

sediment from the main-channel system would require 

about 0.12 ft of average downcutting. Obviously, none of 

the above statistical manipulations satisfy the true erosion picture; however, they may provide a crude reference for regional comparison with other runoff events. 

ACKNOWLEDGMENTS 

The U.S. Geological Survey gratefully acknowledges 

major financial assistance from the U.S. National Park 
ACKNOWLEDGMENTS 25 

FIGURE 20.-Floating debris at the mouth of Eldorado Canyon. Photograph on afternoon of September 15, about 24 hours after flood and 

before any significant cleanup of debris. 

FIGURE 21.-Downstream view of boulder deposits that probably 

moved on September 14 in Techatticup Wash. 

FIGURE 22.-Large boulder that probably moved during flood in lower 

reaches of Eldorado Canyon. 
26 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

FIGURE 23.-Position of high water line at canyon narrows just upstream from former restaurant. Note people standing on high water 

line for scale. 

Service in the investigation and the preparation of this 

report. 

The authors would like to express their appreciation 

to many people who provided help and information during this investigation. T. R. Gess, Engineer, U.S. National Park Service, was particularly helpful. Many 

others in the Park Service at Lake Mead National Recreational Area also provided assistance, including: 

William J. Briggle, Park Superintendent, Gary E. Bunney, Assistant Superintendent, Frank J. Deckert, Gene 

F. Gatzke, David E. Hoover, David J . McLean, James L. 

Monheiser, Richard Rundell, and J.D. Vanderford. AsFIGURE 24.-An automobile at rest in lower Eagle Wash after about a 

1-mile transit in flood. 

sistance and information was also provided by Richard 

Mayne, Clark County Coroner; Dr. Gerald Williams 

and Reid Garner of the U.S. National Weather Service; 

James Pomeroy and staff of the Materials and Testing 

Laboratory, Nevada Highway Department, Las Vegas; 

several members of the Nevada Highway Department 

in Carson City who furnished aerial photographs and 

gravel sample bags; R. J. Gregory, Director, Nevada 

Civil Defense and Disaster Agency; A. R. Methvan, 

Thomas Jester, and Murl Emry, Nelson residents; KenFIGURE 25.-Evidence of intense rill erosion in unnamed tributary to 

lower Eldorado Canyon. 
REFERENCES CITED 27 

FIGURE 27.-Highway damage in Techatticup Wash caused mainly by lateral channel scour. 

neth E. Beales, for permission to publish his photograph 

of flood flow; and John Gallifent, Lemuel Washington, 

Mr. and Mrs. Kirby L. Koop, and Dr. J. H. Sessums, 

eyewitnesses to the flood . 

The authors apologize for anyone who helped but was 

inadvertently omitted from the foregoing list. Without 

the help of all, many details and interpretations in this 

report would have been impossible. 

REFERENCES CITED 

Casebier, D. G., 1970, Camp El Dorado, Ariwna Territory: Tempe, 

Arizona Historical Foundation, Arizona Mon. No. 2, 103 p. 

Dalrymple, Tate, and Benson, M. A., 1967, Measurement of peak 

discharge by the slope-area method: U.S. Geol. Survey 

Techniques Water-Resources Inv., Book 3, ch. A2, 12 p. 

FIGURE 26.-Evidence of minor channel flow and only minimal rill 

erosion in Copper Canyon. 

Fenneman, N. M., 1931, Physiography ofWestern United States: New 

York and London, McGraw-Hill Book C.1mpany, Inc., 534 ",J. 

Hough, D. K., 1957, Basic soils engineering: New York, The Ronald 

Press Company, 513 p. 

Hoyt, W. G., and Langbein, W. B., 1955, Floods: Princeton Univ. 

Press, 469 p. 

Longwell, C. R. , 1963, Reconnaissance geology between Lake Mead 

and Davis Dam, Arizona-Nevada: U.S. Geol. Survey Prof. Paper 

374-E, p. E7-E51. 

FIGURE 28.- Windrows of boulders bordering a pre-September 14, 

1974 erosion scar. 
28 HYDROLOGY OF ELDORADO CANYON, NEV., FLOOD OF SEPTEMBER 14, 1974 

Longwell, C. R., Pampeyan, E. H., Bowyer, Ben, and Roberts, R. J., 

1965, Geology and mineral deposits of Clark County, Nevada: 

Nevada Bur. Mines Bull. 62, 218 p. 

Matthai, H. F., 1969, Floods of June 1965 in South Platte River basin, 

Colorado: U.S. Geol. Survey Water-Supply Paper 1850-B, p. 

B1-B64. 

Moore, D. 0 ., 1974, Estimating flood discharges in Nevada using 

channel-geometry measurements: Carson City, Nevada Highway 

Dept. Hydrologic Rept. 1, 43 p. 

*U.S. GOVERNMENT PRINTING OFFICE: 1975-0-689-910/82