U.S. Department of the Interior

U.S. Geological Survey

Channel and Hillslope Processes

Revisited in the Arroyo de los Frijoles

Watershed near Santa Fe, New Mexico

Professional Paper 1704
Cover. Upper left photo: Stagger Reach, Arroyo de los Frijoles, May 11, 1993, view looking downstream; Upper right photo: Big 

Sweat Dam, June 17, 1993; Lower right photo: Main Project Reach, Arroyo de los Frijoles, March 10, 1998, view looking downstream to 

abandoned streamflow-gaging station on right bank; Lower left photo: Mouth of Green Rock Gulch in Slopewash Tributary of Arroyo de 

los Frijoles, May 11, 1993, view looking downstream; Center photo: Arroyo de los Frijoles at Buckman Road, September 27, 1997, view 

looking upstream. (Photographs by Allen C. Gellis, U.S. Geological Survey)
Channel and Hillslope Processes 

Revisited in the Arroyo de los Frijoles 

Watershed near Santa Fe, New Mexico

By Allen C. Gellis, William W. Emmett, and Luna B. Leopold

U.S. Geological Survey Professional Paper 1704

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

U.S. Geological Survey, Reston, Virginia: 2005

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Gellis, A.C., Emmett, W.W., and Leopold, L.B., 2005, Channel and hillslope processes revisited in the Arroyo de los 

Frijoles watershed near Santa Fe, New Mexico: U.S. Geological Survey, Professional Paper 1704, 53 p.

Library of Congress Cataloging-in-Publication Data

Gellis, Allen C. 

Channel and hillslope processes revisited in the Arroyo de los Frijoles watershed near Santa Fe, New Mexico/

by Allen C. Gellis, William W. Emmett, and Luna B. Leopold. 

p. cm.—(U.S. Geological Survey professional paper ; 1704)

Includes bibliographic references.

1. Erosion—New Mexico—Frijoles, Arroyo de los, Watershed (Santa Fe County). 

2. Arroyos—New Mexico—Frijoles, Arroyo de los, Watershed (Santa Fe County). 

I. Emmett, William W. II. Leopold, Luna Beregere, 1915. III. Channel and hillslope processes revisited in the 

Arroyo de los Frijoles watershed near Santa Fe, New Mexico. IV. Series: U.S. Geological Survey professional paper ; 

1704.

QE571.G33 2005

551.3‘02‘0978956—dc22 2005044247

IISBN 0-607-98419-8
iii

Contents

Abstract ................................................................................................... 1

Introduction ................................................................................................ 2

Background .......................................................................................... 2

Study Area .......................................................................................... 6

Methods ............................................................................................. 6

Rainfall Data ................................................................................. 6

Channel Cross-Sectional Surveys ......................................................... 11

Channel-Bed Scour and Fill .................................................................. 11

Deposition Behind Dams and Base-Level Experiments ................................. 12

Hillslope-Erosion Plots ........................................................................ 12

Land Use ....................................................................................... 13

Rainfall Trends ....................................................................................... 13

Channel and Hillslope Processes ..................................................................... 15

Channel Cross-Sectional Resurveys ............................................................ 15

Changes in Cross-Sectional Area ......................................................... 15

Changes in Thalweg Elevation ............................................................... 23

Changes in Gunshot Arroyo .................................................................. 30

Channel-Bed Scour and Fill ........................................................................ 30

Deposition Behind Dams and Base-Level Experiments ............................................. 34

Deposition Behind Dams ........................................................................... 34

Base-Level Experiments ........................................................................... 37

Hillslope-Erosion Plots .............................................................................. 41

Changes in Land Use .............................................................................. 44

Summary ............................................................................................. 45

Acknowledgments ................................................................................. 47

References ................................................................................................ 48

Appendix 1. Summary of difference in elevations in closing the 1993 and 1997 resurveys 

to the original surveys ........................................................................... 51
iv

Figures

1A. Location of watersheds and location names used in this report ........................ 3

1B. Approximate location of watersheds and cross sections surveyed in watersheds in 

1993 to 1997 .................................................................................... 4

1C. Coyote C. Arroyo and Morning Walk Wash watersheds showing cross sections and 

erosion pins .................................................................................... 5

1D. Big Sweat Dam and Little Sweat Dam near Gunshot Arroyo showing topography ... 7

1E. Schematic showing erosion pin plot on hillslope adjacent to Slopewash Tributary 8

2. Rainfall recorded at the Santa Fe rain gage: (A) average annual rainfall intensity, 

1853–1961; (B) average annual rainfall intensity, 1853–1993; (C) annual number of days 

of summer rainfall for low-intensity rainfall ................................................ 9

3. Main Project reach, Arroyo de los Frijoles. (A) Looking downstream to streamflowgaging station, August 10, 1960; (B) Looking downstream to streamflow-gaging 

station, March 1988. ........................................................................... 10

4. Survey cross sections in Arroyo de los Frijoles watershed, Coyote C. Arroyo, 

Gunshot Arroyo, and Morning Walk Wash. .............................................16–20

5. Change in (A) percent cross-sectional area and (B) thalweg elevation. ............... 27

6. Aggradation and degradation of 35 cross sections resurveyed in 1997 compared 

with Leopold and others’ (1966) original survey from 1958 to 1964 at (A) main channel 

Arroyo de los Frijoles, and (B) Main Project reach in Arroyo de los Frijoles ......... 28

7. Channel elevation changes for the main channel Arroyo de los Frijoles at the 

cross sections resurveyed in 1993 and 1997 compared with Leopold and others’ 

(1966) original 1958–64 surveys. ............................................................ 29

8. Adjacent cross sections in the main channel Arroyo de los Frijoles showing 

similar channel changes in aggradation or degradation of the thalweg elevation 

from Leopold and others’ (1966) survey to resurvey conducted in 1993 and 1997 ... 29

9. Change in thalweg elevation compared with (A) distance downstream from 

watershed divide for all 1993 and 1997 resurveyed cross sections, and (B) widthto-depth ratios for 32 cross sections with full cross-sectional surveys. ............... 30

10. Change in thalweg elevation between the Leopold and others’ (1966) original 

1961 survey and the 1993 resurvey of channel cross sections in Coyote C. Arroyo. 30

11. Gunshot Arroyo (A) resurvey of longitudinal profile, 1988, (B) from station 0 to 

200 meters and from station 200 to 350 meters, and (C) channel changes at 

station 417 bottom of headcut and station 417 top of headcut ........................... 31

12. Scour-chain measurements of (A) scour, 1964–68; (B) fill, 1964–68; (C) scour, 

1993; and (D) fill, 1993. ........................................................................ 32

13. Depth of scour as a function of discharge at scour-chain sections. .................. 34

14. Scour and fill from 1993 resurveys of scour chains at (A) main channel Arroyo 

de los Frijoles, and (B) Main Project reach in Arroyo de los Frijoles plotted with 

net change in thalweg from 1993 and 1997 resurveys. .................................... 35

15. Thickness map of sediment deposited at reservoir on Coyote C. Arroyo. ............ 36

16. (A) View looking downstream toward Big Sweat Dam shortly after its construction 

in 1960. (B) Little Sweat Dam, 1960. (C) View looking downstream toward Big Sweat 

Dam, 1998. .................................................................................... 38
v

 17A-B. Successive channel-bed profiles of (A) Entire length of channel upstream from 

Big Sweat Dam. (B) Profiles of the channel within 35 meters of Big Sweat Dam 

showing locations of resurveyed channel cross sections .............................. 39

17C-D. (C) Entire length of channel upstream from Little Sweat Dam. (D) Profiles of the 

channel within 30 meters of Little Sweat Dam showing locations of resurveyed 

channel cross sections . ..................................................................... 40

18. Planform diagram of 1960 and 1993 thalweg locations upstream from 

Big Sweat Dam ................................................................................. 42

19. Hillside containing pin and washer lines in an erosion plot on Slopewash Tributary 43

20. Roads in Arroyo de los Frijoles (A) in 1952–53 and (B) in 1987. ........................... 45

21. Road crossings over the main channel Arroyo de los Frijoles. (A) Buckman Road 

6,662 meters downstream from the Slopewash Tributary watershed divide. 

(B) Unnamed road crossing with culvert 2,700 meters downstream from 

Slopewash Tributary ........................................................................... 46

Tables

1. Rainfall summaries for selected time periods in Arroyo de los Frijoles, 

Coyote C. Arroyo, Gunshot Arroyo, and Morning Walk Wash ........................... 14

2. Average rainfall frequency of low-, moderate-, and high-intensity rainfall, 

Santa Fe, New Mexico. ..................................................................... 14

3. Characteristics of resurveyed cross sections between original survey and 

resurvey in 1993–97 ........................................................................... 21

4. Summary of resurveyed channel characteristics in 1993 and 1997 in relation 

to Leopold and others’ (1966) original channel surveys in Arroyo de los Frijoles, 

Coyote C. Arroyo, Gunshot Arroyo, and Morning Walk Wash ........................... 23

5. Elevation of thalweg at 63 cross sections from 1958 to 1997 in the main 

channel Arroyo de los Frijoles ............................................................... 24

6. Average changes and channel length-weighted changes in thalweg elevations 

for the main channel Arroyo de los Frijoles ................................................ 26

7. (A) Deposition rates in the sediment pool behind the earthen dam at 

Coyote C. Arroyo, 1961–93. (B) Sedimentation rates for selected time periods 

at Coyote C. Arroyo. ........................................................................... 37

8. Selected summary of sediment yields in New Mexico streams ........................ 37

9. Weighted slopes of channel upstream from Big Sweat Dam and Little Sweat 

Dam near Santa Fe, New Mexico ............................................................ 41

10. Summary of erosion-pin measurements at hillslope-erosion plots at 

Coyote C. Arroyo and Slopewash Tributary. ................................................ 42

11. Surface-erosion and denudation rates reported from studies conducted in 

the Southwest ................................................................................. 44
vi

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 35.31 cubic foot (ft3) 

square meter (m2) 10.76 square foot (ft2) 

Flow rate

cubic meter per second (m3/s) 35.31 cubic feet per second (ft3/s)

Mass

pounds (lb) 3.7324 × 10-4 metric tons

metric tons 2.205 × 10+3 pounds

kilogram (kg) 2.2046 pound avoirdupois (lb)

Density

kilogram per cubic meter (kg/m3) 0.06243 pound per cubic foot (lb/ft3) 

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Conversion Factors and Datums
Abstract

Detailed documentation of geomorphic changes in the 

landscape of more than a few years is rarely possible. Channel 

cross sections, channel profiles, sediment deposition behind 

dams, and hillslope-erosion plots, originally benchmarked 

within several watersheds outside Santa Fe, New Mexico, 

in the 1950’s and 1960’s, for a 1966 report that documented 

processes and rates of arid-region sediment production and 

deposition, were resurveyed in the mid-1990’s. Many of 

the original study sites were relocated and surveyed in the 

mid-1990’s to determine subsequent channel and hillslope 

changes and to determine whether trends of channel and 

hillslope aggradation and degradation that were evident in 

the 1950’s and 1960’s have continued. In general, the net 

change in channel geometry has been small over the last 

30–40 years. The average change in cross-sectional area of 32 

resurveyed cross sections was erosion of 0.27 square meter, 

which equates to a 4-percent increase in cross-sectional area. 

The average net change in thalweg elevation for 51 resurveyed 

cross sections was degradation of 0.04 meter. Unpublished 

data (1964–68) from the scour chains showed that 371 chains 

had an average scour of 0.14 ± 0.14 meter and that 372 chains 

showed an average fill of 0.13 + 0.11 meter. Scour, found 

in the original study (1958–64) to be proportional to the 

square root of discharge, was confirmed with the addition of 

unpublished data (1964–68). The observed channel changes 

have no consistent trend, compared either to results observed 

in the original 1966 study or to distance from the watershed 

divide. The conclusion drawn in the original study was that 

most channels were aggrading; the resurvey showed that 

aggradation did not continue.

An increase in housing and population in the Arroyo de 

los Frijoles watershed since the 1950’s has led to more roads. 

Channel degradation is most noticeable at road crossings. 

The greatest degradation of the main channel Arroyo de los 

Frijoles, 1.53 meters, and the greatest aggradation, 0.38 meter, 

occur downstream and upstream, respectively, from a culvert 

in a dirt road. 

Periods of high average annual rainfall intensity reported 

for Santa Fe for 1853–80 immediately preceded late 19th century arroyo incision, and another period of high-intensity rainfall began in 1967. This may indicate that climatic factors are 

again favorable for arroyo incision in this part of New Mexico; 

data from this resurvey, however, do not provide evidence of a 

renewed cycle of erosion.

At a 1930’s Civilian Conservation Corps-constructed dam 

on Coyote C. Arroyo, the measured sediment yield from 1966 

to 1993 was 139 metric tonnes per square kilometer per year. 

Sediment yields have decreased through time because of either 

a decrease in the trap efficiency of the reservoir over time or 

a decrease in sediment delivery to the reservoir because of 

upstream channel storage. The effects of base-level rise on the 

channel profile were documented in 1993 through resurveys of 

sediment deposits behind two small dams, Big Sweat Dam and 

Little Sweat Dam. Both dams, built in 1960, showed sediment 

deposition that extends 20 and 9.3 meters upstream, respectively, and the 1993 sediment gradient was nearly the same 

as the unaffected channel upstream. Big Sweat Dam showed 

fluctuations in channel gradient within 5.3 meters of the dam, 

which may be a result of local scour following complete filling 

of the dam, scour from increased sinuosity, or differences in 

the location of surveying stations over time. The sinuosity of 

the channel has increased over time, presumably from a reduction in slope. Channel gradients 0 to 11.0 meters upstream 

from Little Sweat Dam have remained constant at about 0.028 

from 1964 to 1993.

Measurement of erosion or hillslope-erosion plots show 

that average values of surface erosion range from 0.019 to 

0.096 centimeters per year and are within values reported for 

regional erosion and denudation studies. Sediment yield from 

the Slopewash Tributary erosion plot was 307 metric tonnes 

per square kilometer per year. 

The reproducibility and accuracy of the resurveys from 

the 1950’s to the 1990’s attest to the concepts used to quantify 

geomorphic features established in the Vigil Network. With 

relatively simple techniques, more than 30 years of geomorphic change were observed in this study.

Channel and Hillslope Processes Revisited in the Arroyo 

de los Frijoles Watershed near Santa Fe, New Mexico

By Allen C. Gellis, William W. Emmett, and Luna B. Leopold
Introduction

Observing, quantifying, and understanding geologic processes in the modern record is a major occupation of process 

geomorphologists. The opportunity to describe geomorphic 

changes in detail is often not possible, however, because of a 

lack of reliable and precise historical data. Recognition of that 

lack of detailed data for hydrologic and geomorphic studies 

led to the establishment of a network of reference sites known 

as the Vigil Network (Leopold, 1962; Emmett and Hadley, 

1968; Osterkamp and others, 1991). A principal objective of 

the Vigil Network is to preserve data on geomorphic processes 

for future generations. Geomorphic data collected at Vigil 

Network sites include observations of deposition behind dams, 

hillslope processes (mass movements, soil creep, and sheetwash erosion), vegetation, and fluvial processes (bank retreat, 

channel scour, and aggradation). Simple techniques are used to 

measure geomorphic processes: surveys, erosion pins, painted 

rocks, vegetation transects, and scour chains. A requisite of the 

Vigil Network is permanent survey benchmarks and monuments (Emmett, 1965).

Leopold and others (1966) described hillslope and channel processes and rates for four small watersheds near Santa 

Fe. Their interpretations of geomorphic processes were based 

on observations derived from surveyed channel cross sections, 

scour-chain measurements, erosion pins, and reservoir surveys. 

Their work is an example of a study at a Vigil Network site.

This report presents the results of a study that compares 

channel and hillslope measurements with the original study 

of Leopold and others (1966). The Leopold and others (1966) 

report was in inch-pound units and for this report was converted to metric units. Long-term rates of erosion, sediment 

yield, and the effects of base-level changes on channel profiles 

in a semiarid environment also are discussed. The causes for 

any observed changes are investigated, and conclusions on 

geomorphic change are compared with those in the original 

study. Data were collected in portions of four watersheds 

through 1968 but were never published and are presented in 

this report. These include longitudinal measurements of the 

channel behind Big Sweat and Little Sweat Dams, scour-chain 

measurements, and erosion-pin measurements. In addition, 

rainfall between 1958 and 1993 is described and implications 

of the trends are discussed in relation to channel changes.

Background

Arroyo changes in the American Southwest have been 

the focus of several investigations. These investigations have 

examined channel processes such as channel incision and 

aggradation and environmental variables that may affect 

channels (Bryan, 1928a; Cooke and Reeves, 1976; Gellis and 

others, 1991; Bull, 1997; Elliott and others, 1999). The word 

“arroyo” generally refers to a steep-sided channel entrenched 

into alluvium. Many alluvial valleys that contained either 

discontinuous or unincised channels became incised throughout the Southwest, generally between 1880 and 1920, creating arroyos. The causes of arroyo incision have been a topic 

of considerable debate. Arroyo incision has been attributed 

to climate change (Leopold, 1951; Balling and Wells, 1990), 

land use (Thornwaite and others, 1942; Cooke and Reeves, 

1976), dam failures (Love, 1997), or a natural cyclicity of 

arroyo incision that may be related to intrinsic thresholds of 

valley slope (Schumm and Hadley, 1957; Patton and Schumm, 

1975). Many arroyos that incised between 1880 and 1920 were 

reported as aggrading in the mid- and late-20th century (Leopold, 1976; Gellis, 1998; Elliott and others, 1999).

Although there was considerable discussion on the causes 

of arroyo formation during the first half of the 20th century, 

few actual measurements of channel and hillslope erosion 

were made. The study by Leopold and others (1966) in four 

watersheds near Santa Fe—Arroyo de los Frijoles (9.71 km2), 

Coyote C. Arroyo (0.16 km2), Morning Walk Wash (0.03 km2), 

and Gunshot Arroyo (0.09 km2) (fig. 1A–C)—provided quantitative data for examining the rates of channel and hillslope 

erosion and deposition and sought to explain causes for any 

observed change. Leopold and others (1966) quantified erosion rates by analyzing processes and rates of channel changes 

and by constructing a sediment budget for part of the Arroyo 

de los Frijoles watershed. The rates determined were supplemented with concurrent measurements of streamflow, rainfall, 

channel scour, hillslope erosion, mass movement, rock movement, vegetation, channel cross-sectional geometry, bed-material grain size, and sediment deposition behind dams. Channel 

scour was measured using chains, and hillslope erosion was 

measured using erosion pins. Channel and reservoir sections, 

scour chains, erosion plots, and mass-movement lines were 

monumented with steel bars.

The 1966 study reported measurements made from 1958 

to 1964. Analysis of the measurements indicated that channels 

in most reaches in the Arroyo de los Frijoles watershed were 

aggrading. The sediment budget for Arroyo de los Frijoles 

indicated sheetwash as the largest source of sediment accounting for aggradation. The average rate of aggradation for all 

channels was 0.015 m/yr (Leopold and others, 1966, p. 239). 

At this rate, the channel would completely fill to the level of 

the highest terrace in 100 to 200 years. At scour chains, most 

sections showed scour and subsequent fill. The average scour 

depth was observed to be proportional to the square root of 

discharge per unit width of channel. No downstream trends in 

channel change or bed scour were evident.

Hillslope and channel erosion rates were compared to 

the amount of sediment accumulation behind an earthen dam 

about 1-m high on Coyote C. Arroyo, constructed in 1937 by 

the Civilian Conservation Corps (Leopold and others, 1966). 

In 1962–64, the reservoir was topographically mapped with 

a planetable to determine the amount of fill since established 

surveys in 1961. The drainage area of the dam is 0.155 km2. 

During 1961–64, 59.0 m3/yr of sediment was deposited (Leopold and others, 1966, p. 235), which was less than 5 percent of 

basinwide eroded sediment.

2 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Figure 1A. Location of watersheds and location names used in this report. (Modified from Leopold and others, 1966.)

Introduction 3

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4 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 1C. Coyote C. Arroyo and Morning Walk Wash watersheds showing cross sections and 

erosion pins. See figure 1A for location within study area. (Modified from Leopold and others, 

1966—Continued.)

Introduction 5

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To determine how base-level rise affects the channel 

longitudinal profile, two small concrete dams, Big Sweat 

Dam and Little Sweat Dam (fig. 1D), were constructed in 

1960, each on an ephemeral channel draining into Arroyo de 

los Frijoles (Leopold and Bull, 1979). By 1962, the sediment 

wedge in Big Sweat Dam had reached 15.2 m upstream and 

by 1964 had reached 24.4 m. In 4 years the gradient decreased 

27 percent, from 0.045 m in 1960, before the dam was built, to 

0.033 m in 1964 (Leopold and Bull, 1979, p. 189). After 1964, 

the gradient remained constant, and the maximum distance 

upstream from the dam that sediment was deposited was 

33.5 m or 15 percent of the distance along the channel from 

the dam to the watershed divide.

To measure the rate of hillslope erosion, a grid system of 

erosion pins was installed in 1959 on the slopes of Slopewash 

Tributary (Leopold and others, 1966, p. 220–222) (fig. 1E). 

The erosion pins were measured from 1959 to 1964 and 

showed deposition of 0.12 cm/yr and erosion of 0.36 cm/yr 

or a net surface lowering of 0.24 cm/yr (Leopold and others, 

1966, p. 222).

Another important conclusion of the 1966 study, based 

on earlier work by Leopold (1951), involved rainfall intensity 

in Santa Fe from 1853 to 1961 (fig. 2). From 1856 to 1870, 

annual rainfall was similar to long-term averages but fell 

on fewer days per year, thus rainfall intensity was higher 

(fig. 2A,B). Rainfall intensity was higher during a period when 

rains of low intensity (0.25 to 12.4 mm) were low (fig. 2C,D). 

Leopold and others (1966) hypothesized that vegetation would 

be depleted during this period because of the low amounts 

of low-intensity rainfall. Intense rainfall in combination with 

depleted vegetation led to arroyo incision. Periods of arroyo 

incision or channel erosion for the Rio Puerco in New Mexico 

were reported from about 1885 to 1890 (Bryan, 1928b) and 

for arroyos on the Zuni Reservation in about 1905 (Balling 

and Wells, 1990). Therefore, if rainfall recorded in Santa Fe is 

valid for a wider area, arroyo incision reported in these areas 

of New Mexico occurred shortly after the climate change 

identified by Leopold (1951).

Streamflow was recorded from 1958 to 1968 at three 

streamflow-gaging stations in the main channel Arroyo de los 

Frijoles: North Frijoles reach, Locust Tree reach, and Main 

Project reach (figs. 1 and 3) (Leopold and others, 1966). 

For the Main Project reach (fig. 1A,B), flows were recorded 

38 times between 1958 and 1968. The highest peak flow 

recorded was 86.6 m3/s on September 13, 1958 (Leopold and 

others, 1966, p. 203), and 86.6 m3/s on August 1–2, 1966 (U.S. 

Geological Survey, unpublished data). All flows were recorded 

between May and October, and 63 percent occurred in July 

and August. Rainfall during the summer months near Santa 

Fe can be intense and is localized. Discharge increased in the 

downstream direction only 5 of the 38 times. Concentrations 

in eight samples of suspended sediment collected from 1958 to 

1962 ranged from 28,300 to 126,000 ppm (parts per million). 

Median grain size of the suspended sediment was silt and clay 

and ranged from 0.004 to 0.016 mm (U.S. Geological Survey, 

unpublished data).

In this report the following terms will be used to describe 

changes in the channel bed, hillslope, and behind impoundments. Deposition is the addition of sediment at one particular 

location on the channel bed, hillslope, or behind an impoundment. Aggradation is an increase in the channel thalweg 

elevation over time by sediment deposition and degradation is 

a lowering of the channel thalweg elevation over time by sediment removal. Aggradation and degradation are terms used to 

describe channel changes for the entire cross section. Scour 

is the lowering of the channel bed elevation at one specific 

location in the cross section and fill is an increase in the channel bed at one specific location. For the entire channel cross 

section, erosion is the removal of sediment which increases 

cross-sectional area and deposition is the addition of sediment which decreases cross-sectional area. Incision is used 

to describe channel degradation over a broader length of the 

channel. On hillslopes, erosion refers to removal of sediment 

and a lowering of ground elevation and deposition is the addition of sediment.

Study Area

The study area is located northwest of the city of Santa 

Fe (fig. 1A). Bedrock in the study area is composed of the 

Tesuque and Ancha Formations of the upper part of the 

Santa Fe Group of Tertiary age and unconsolidated gravel, 

sand, and silt also of Tertiary age (Miller and others, 1963). 

Ephemeral channels in the area reflect the underlying geology and have sand-sized bed material (median size ranging 

from 0.50 mm for Coyote C. Arroyo to 0.78 mm for Arroyo 

de los Frijoles in its upper reaches) (Leopold and others, 

1966, p. 204). The climate is semiarid with an average annual 

rainfall of 361 mm from 1853 to 1993. Vegetation in the area 

is open piñon-juniper woodland with sparse grass and exposed 

soil in many areas.

Methods

Rainfall Data

Annual and monthly rainfall data for 1868–1993 were 

obtained from National Weather Service records and for 

1853–67 were obtained from the New Mexico Office of the 

State Engineer (State of New Mexico, 1956). Daily rainfall 

was obtained only for 1868 to 1995. If records for 1 year had 

more than 15 days of missing rainfall, that year was not used. 

The average intensity and frequency of rainfall, in varying size 

classes for 1853–67, were obtained from Leopold and others 

(1966, figs. 171–173, p. 241–242).

6 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Figure 1D. Big Sweat Dam and Little Sweat Dam near Gunshot Arroyo showing topography. (Modified from Miller and 

Leopold, 1961—Continued.)

Introduction 7

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Figure 1E. Schematic showing erosion pin plot on hillslope adjacent to Slopewash Tributary. (Modified from Leopold and 

others, 1961—Continued.)

8 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 2. Rainfall recorded at the Santa Fe rain gage: (A) average annual rainfall intensity, 1853–1961 (Leopold and others, 

1966); (B) average annual rainfall intensity, 1853–1993; (C) annual number of days of summer rainfall for low-intensity rainfall 

(0.25–12.4 mm), 1883–1993; (D) number of days of non-summer rainfall for low-intensity rainfall of 0.25–12.4 mm, 1883–1993; 

(E) Five-year moving average of rainfall intensity; and (F) average annual rainfall intensity shown with average rainfall intensity for three time periods: 1853–1869, 1870–1964, and 1965–93.

Introduction 9

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Figure 3. Main Project reach, Arroyo de los Frijoles. (A) Looking downstream to streamflow-gaging station, 

August 10, 1960; (B) Looking downstream to streamflow-gaging station, March 1988.

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10 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
at these cross sections could be quantified only as the difference between the thalweg elevation in 1993 and the scourchain elevation in the original survey.

The Arroyo de los Frijoles channel was originally surveyed during 1958–59. At cross section CS-45 (cross section 

17 in fig. 1A), the original elevation of the thalweg could not 

be located, so an elevation from a survey conducted in 1960 

was used as the original elevation instead. The longitudinal 

profile of Gunshot Arroyo (fig. 1) was resurveyed in 1998 and 

compared with the original 1962 survey.

A positive change in cross-sectional area indicates erosion (degradation). Channel cross-sectional area can increase 

by a deepening of the thalweg and(or) widening of the channel 

cross section. Because channel cross sections are not evenly 

spaced, an alternative to averaging cross-sectional area 

changes for each channel was weighting each measurement to 

channel length. Changes in cross-sectional area are expressed 

as a percentage by dividing the original cross-sectional area 

by the resurveyed cross-sectional area and multiplying by 100. 

A weighted change in cross-sectional area was computed for 

the entire length of each channel by multiplying the change in 

cross-sectional area by the channel length-weighted distance, 

then summing the values. The channel length-weighted 

distance is the length of a reach, representative of the measurement, divided by the entire channel length. A channel reach 

is defined as the sum of one-half the distance to the nearest 

upstream cross section plus one-half the distance to the nearest 

downstream cross section. Using a channel-weighted distance 

to represent cross-sectional area changes of the channel length 

assumes that each cross section is representative of a longer 

segment. Because of the small drainage areas of Morning 

Walk Wash and Gunshot Arroyo, a weighted change in crosssectional area was not computed and an average was used.

The location of each cross section was obtained from 

Leopold and others’ (1966) project file notes that indicated 

the taped distance of each cross section from the divide 

at Slopewash Tributary. Because the location of the cross 

sections was measured with a tape, there may be some error 

in the exact location of cross sections displayed in figures and 

tables in this report.

Channel-Bed Scour and Fill

In the original study, channel-bed scour and fill associated with several individual flow events were measured by 

repeat surveys of scour chains. Scour chains were placed in 

63 cross sections in the main channel Arroyo de los Frijoles. 

Scour and fill measurements were not made in Coyote C. 

Arroyo, Morning Walk Wash, or Gunshot Arroyo. For the 

scour and fill measurements, at least one of the locations 

was the thalweg or lowest part of the channel cross section. 

At some reaches more than one scour chain was placed in 

the channel cross section, resulting in a total of 90 chains. 

Although the results of the 1958–64 scour-chain measurements were published in Leopold and others (1966), measurements continued through 1968 (USGS unpublished data) 

Channel Cross-Sectional Surveys

In the original study (Leopold and others, 1966), 63 channel cross sections were monumented from 1958 to 1960 in the 

main channel Arroyo de los Frijoles watershed. Six additional 

cross sections were monumented in Coyote C. Arroyo in 1961, 

5 in Morning Walk Wash in 1961, and 5 in Gunshot Arroyo in 

1962, for a total of 79 cross sections.

All cross sections were originally monumented with steel 

bars on the left and right banks. All cross sections in Coyote 

C. Arroyo, Morning Walk Wash, and Gunshot Arroyo were 

surveyed to measure changes in channel geometry of the 

entire cross section. Eighteen of the 63 cross sections in the 

main channel Arroyo de los Frijoles were surveyed to measure 

changes in channel geometry of the entire cross section and 

to measure scour and fill in the channel. Scour chains were 

installed at the remaining 45 cross sections in Arroyo de los 

Frijoles that were not monumented for cross-sectional surveys, 

and elevations of the channel bed were measured only at 

the scour-chain locations. To provide useful information for 

future surveys, all 1993 and 1997 surveys were full crosssectional surveys.

For the 1993 and 1997 resurveys, a survey level was 

used, and the distance the tape was stretched from steel bar to 

steel bar was the same as in the original survey. If the original 

left- and right-bank steel bars were found, the accuracy of the 

elevations in the resurvey was determined by comparing the 

difference in elevations of the left- and right-bank steel bars in 

the original survey to the difference in elevations of the leftand right-bank steel bars in the resurvey. In the original survey, 

all cross-sectional elevations were tied into the same datum. 

If one of the original steel bars could not be found in 1993 

and 1997, the remaining steel bar was tied into the closest 

upstream or downstream cross-sectional steel bar. If elevation 

control could not be determined, the accuracy of the resurvey 

was assessed on the basis of comparisons of surfaces in the 

cross section that might not change over time, such as the 

highest surface on which the steel bars are located. Techniques 

used to survey the channel cross sections are similar to those 

in Gellis (1998).

Channel width is the horizontal distance between the 

tops of the vertical banks that define the left and right sides 

of the channel. Channel depth was measured by averaging the 

heights of the two channel banks to the lowest elevation in the 

channel or thalweg.

In the 1993 and 1997 resurveys, changes in thalweg 

elevation and cross-sectional area were compared with those 

from the original surveys. Data from the original study were 

obtained from plots of cross sections of the channel and from 

original data sheets listing the thalweg elevations. A channel 

was categorized as aggrading if the elevation in the thalweg 

increased over time. In the original study at least one of the 

scour chains was installed in the thalweg of the channel cross 

section. Because the thalweg may have migrated since the 

original study, scour chains located in 1993 were not always 

located at the thalweg. Therefore, aggradation or degradation 

Introduction 11
and are interpreted in this report. Seventy-nine chains were 

surveyed from 1964 to 1968 and some chains were surveyed 

as many as nine times, resulting in 372 measurements of scour 

and fill. The procedures used by Leopold and others (1966) 

were used in this study.

Depth of scour and fill in many of the cross sections was 

measured by vertically installing one or more 1.22-m chains, 

12.7 mm thick, in a hole dug in the channel bed with the top 

link at or slightly above the bed surface. After a flow, the chain 

would lie horizontally at some depth below the bed surface if 

scour and fill occurred. Maximum depth of scour was measured from the elevation of the channel bed of the preceding 

survey to the elevation of the bend in the current scour chain. 

Fill was measured by the bend in the chain relative to the 

channel bed. The chains were reset after each measurement. 

Changes in bed elevation at the chain location were quantified from 1958 to 1968. At selected times from 1958 to 1962, 

changes in the entire cross section were examined.

For the 1993 resurvey, some of the original scour chains 

were found in many of the cross sections. The maximum scour 

since the last time the chains had been measured (from 1964 

to 1968) was quantified by subtracting the elevation of the 

bend in the chain from the elevation of the channel bed in the 

original survey.

Deposition Behind Dams and Base-Level 

Experiments

The dam on Coyote C. Arroyo (fig. 1A), constructed 

by the Civilian Conservation Corps in 1937, was used in the 

original study to quantify sediment yield over time. Sediment 

yields measured in Coyote C. Arroyo were thought to represent conditions for a wider area (Leopold and others, 1966). 

Cross sections across the sediment pool were monumented 

with steel bars in 1961. Seven steel pins were monumented 

to resurvey sediment deposition (Leopold and others, 1966, 

fig. 170). The steel bars in 1993 were resurveyed using the 

same procedures used in the channel cross sections. Connecting all steel bars defined the outside boundary of the sediment 

pool. The steel bars were placed to quantify most of the sediment deposition, but some sediment was deposited outside the 

polygon and is not included in the volume calculations. Cores 

of sediment were collected to define the density of sediment. 

Volumes of sediment deposited between 1961 and 1993 were 

calculated using a computer software package. Easting, northing, and elevation data for the 1961 and 1993 cross sections 

are gridded in the software package. The grids for both years 

are the same size, and volume calculations are made for each 

grid cell. The total volume of deposited sediment is a solid 

defined by the upper and lower surfaces. 

To investigate the effect of base-level rise on the channel profile, Big Sweat Dam and Little Sweat Dam were 

constructed in 1960 on ephemeral tributaries to Arroyo de los 

Frijoles (fig. 1A,B,D) (Miller and Leopold, 1961; Leopold and 

Bull, 1979). The dams were constructed of cement blocks to a 

height of 0.61 m. Big Sweat Dam and Little Sweat Dam drain 

0.015 and 0.0034 km2, respectively (Leopold and Bull, 1979). 

Sixteen cross sections were originally surveyed in 1960 for 

Big Sweat and Little Sweat Dams. The longitudinal profile for 

these dams and all 16 cross sections were resurveyed in 1993 

and compared with previous surveys of all 16 cross sections 

in 1964, 1968, and 1974 for Big Sweat Dam and in 1962 and 

1964 for Little Sweat Dam. Weighted slopes along the profile 

were computed for each survey by multiplying the slope by 

the reach length-weighted distance, then summing.

Hillslope-Erosion Plots

In 1959, a 232-m2 erosion plot was established on a 

hillslope adjacent to Slopewash Tributary (fig. 1A,D). The plot 

consisted of a grid of 61 pins spaced 1.524 m apart, resulting 

in an area of 2.322 m2 for each square in the grid. Hillslope 

sediment erosion and deposition were measured in the original 

study at two sites: one site in the Coyote C. Arroyo watershed, the other on Slopewash Tributary (fig. 1). In Coyote 

C. Arroyo, three lines with a total of 65 erosion pins were 

installed in 1961 and measured at selected times through 1968 

(fig. 1C). The erosion pins in lines AB and BC were spaced 

1.52 m apart and in line ED were spaced 3.05 m apart. In 

Slopewash Tributary, a 232-m2 erosion plot of 61 erosion pins 

spaced on 1.52-m centers and arranged in a 9 by 9 grid was 

installed in 1959 and measured at selected times through 1967 

(fig. 1E). Each row in the grid contained either four or nine 

erosion pins spaced 1.52 m apart.

Each erosion pin was a 25.4-cm-long nail with a washer 

driven flush to the ground. The amount of sediment overlying the washer is deposition. The distance from the bottom of 

the nail to the top of the washer is erosion. The net change in 

ground surface is the difference between the two. If a large 

amount of sediment was deposited on top of the washer, the 

washer would be reset to ground surface. 

The measurements in 1993 were made in accordance 

with Leopold and others (1966). For washers that were not 

reset, the total change in ground surface since installation 

corresponds to the differences quantified by the 1993 measurements. For washers that were reset, the amount of deposition 

and erosion that had been measured earlier was added to the 

1993 measurements to quantify the total change in ground 

surface. A benchmark or steel bar was driven into the ground 

near the erosion-pin sites and used to determine if the pins 

moved over time by soil action or wetting and drying. During the 1993 measurements at Slopewash Tributary, the top 

of the pin heads was surveyed to the benchmark to determine 

whether they had moved over time. At Coyote C. Arroyo, the 

benchmark appeared disturbed; therefore, the tops of the pins 

were not surveyed to the benchmark. In the original study at 

Coyote C. Arroyo, the tops of the pins were surveyed to the 

benchmark only in 1962. If a pin moved, it could be moved 

back to its original position, and the amount of deposition and 

erosion could be computed.

12 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Land Use

Changes in roads in the Arroyo de los Frijoles watershed from 1952–53 to 1987 were determined from 1952–53 

1:19,800-scale and 1987 1:24,000-scale aerial photographs. 

Housing development in the watershed since 1952 was determined from USGS 1:24,000-scale topographic maps.

Rainfall Trends

This section describes rainfall trends for the National 

Weather Service rain gage at Santa Fe. Average annual rainfall 

data for the study area using this rain gage are listed in table 1. 

Because channel cross sections were originally surveyed at 

different times, average rainfall totals are listed for the resurvey periods, 1951–93, 1958–93, and 1960–93. Rainfall during 

various time periods in the 1990's are within 5 percent of the 

long-term record.

Leopold (1951), Cooke (1974), and Balling and Wells 

(1990) suggested that periods of generally low annual rainfall punctuated by intense summer storm activity may trigger 

arroyo incision. Following the presentation of rainfall analysis 

by Leopold (1951), the data were subdivided into six time 

periods consisting of 20- to 30-year intervals (table 2). The 

average number of days per year of daily rainfall totals was 

divided into three classes: low intensity (0.25 to 12.4 mm), 

medium intensity (greater than 12.4 to 25.4 mm), and high 

intensity (greater than 25.4 mm). Rainfall was analyzed by 

calendar year.

To determine whether average annual rainfall from 1853 

to 1993 changed significantly, the slope of the regression line 

was tested to determine if it was significantly less than or 

greater than zero (Kachigan, 1986; Helsel and Hirsch, 1992). 

The null hypothesis (Ho) is that the regression line has no 

slope. The alternative hypothesis is that the regression line has 

a significant slope. The test statistic, T, is defined as

t (1) b – β

Sb = = ----------- –0.89

where

b = slope of the regression line = -0.183

ß = slope being tested = 0

Sb (2) Sy.x 

xi ( ) – x

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and

Sy.x (3) yi yi

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n 2 – ----------------------

i 1 =

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Sy.x = standard error of estimate,

xi = year,

x = mean of all years,

yi = rainfall,

yi = estimated value of rainfall from the regression

 equation,

yi = 713.47 – 0.183xi,

n = number of observations.

Ho is rejected if

With n–2 degrees of freedom and a significance probability 

level of 2.5 percent, t

critical – 1.98. Because t does not exceed 

t

critical, the null hypothesis is accepted that the slope of the 

regression is not significantly different from zero. Thus, average annual rainfall at Santa Fe has no significant trend from 

1853 to 1993.

No trend was observed in average annual rainfall; the 

intensity of rainfall in the six time periods did change, however (table 2). As previously concluded by Leopold and others 

(1966), the 1853–80 time period, which immediately preceded 

arroyo formation in many watersheds, was characterized by 

less frequent low-intensity storms and more frequent highintensity storms. The data also show a continuous increase in 

the number of low-intensity storms from 1881 through 1930 

and a decrease in the number of high-intensity storms after 

1880. Since about 1930, the frequency of low-intensity storms 

has again decreased, and since 1950, the frequency of highintensity storms has increased (table 2). 

Leopold and others (1966) suggested another way to 

estimate rainfall intensity: calculating average annual rainfall intensity by dividing annual rainfall by the total number 

of days having rainfall in that year (fig. 2A). For a constant 

annual precipitation, higher values of average annual rainfall 

intensity would indicate that annual rainfall occurred on fewer 

days, presumably with a greater intensity that could have 

resulted in accelerated erosion. A continuation of their analysis 

of average annual rainfall intensity through 1993, when most 

of the channels were resurveyed, is shown in figure 2B. Differences in rainfall-intensity values shown in figures 2A,B may 

be attributed to minor differences in analytical procedures or 

minor changes in historical precipitation records. 

Five-year moving averages of rainfall intensity indicate 

that the data can be partitioned into three time periods: 

1853 to 1869 (average rainfall = 6.1 mm/day), 1870 to 1964 

(4.2 mm/day), and 1965 to 1993 (5.5 mm/day) (fig. 2E,F). 

A T-test was used to determine whether rainfall intensity 

changed significantly from one time period to the next (Swan 

and Sandilands, 1995). The null hypothesis (Ho) indicates that 

mean rainfall intensity between the groups has no difference. 

The alternative hypothesis is that average rainfall intensity 

changed from one time period to the next. The test statistic, 

T, is defined as

t tcritical >

Introduction 13
Table 2. Average rainfall frequency of low-, moderate-, and high-intensity rainfall, Santa Fe, New Mexico.

[mm, millimeters]

Time 

period

Average lowintensity rainfall 

(days with rainfall 

0.25 to 12.4 mm)

Average moderateintensity rainfall 

(days with rainfall ranging 

from greater than 

12.7 to 25.4 mm)

Average highintensity rainfall 

(days with rainfall 

greater than 25.4 mm)

Average 

annual rainfall 

(mm)

1853–80 68.1 4.6 2.1 345

1881–1910 82.2 5.5 1.1 360

1911–30 83.0 5.4 1.2 364

1931–50 76.6 4.8 1.1 357

1951–70 63.5 5.3 1.4 350

1971–93 58.6 5.2 1.6 355

Table 1. Rainfall summaries for selected time periods in Arroyo de los Frijoles, Coyote C. Arroyo, Gunshot Arroyo, and Morning 

Walk Wash.

[Rainfall in millimeters; data from National Weather Service rain gage at Santa Fe, New Mexico]

Description Time period

Average annual 

rainfall, mm 

(missing years: 

1862, 1864, 1866–67, 

1883–84, 1941–44, 

1948, 1950)

Average summer 

rainfall, mm 

(July to September) 

(missing years: 

1862, 1864, 1866–67, 

1883–84, 1941, 1948)

Average non-summer 

rainfall, mm 

(October to June) 

(missing years: 

1862, 1864, 1866–67, 

1883–84, 1941–42, 1944)

Period of record 1853–1995 361 161 200

Initial surveys to resurvey 

in 1993

1951–93 353 157 195

Initial surveys to resurvey 

in 1993

1958–93 363 159 206

Initial surveys to resurvey 

in 1993

1960–93 364 160 205

Scour chains 1964–68 388 201 185

Scour chains 1964–93 363 160 203

Scour chains 1966–93 358 158 202

Scour chains 1968–93 359 155 204

Early sediment surveys at 

dam at Coyote C. Arroyo

1961–64 340 176 187

Resurvey period at dam at 

Coyote C. Arroyo

1961–93 361 161 202

14 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
where

X = mean of the time period,

S = variance,

and

n = number of observations.

At a significance level of 5 percent, the T-test result for 

the difference in means from 1853 to 1869 and from 1870 

to 1964 is 5.60, which is greater than the p-value of 1.660; 

therefore, the decrease in rainfall intensity between 1853 and 

1869 and between 1870 and 1964 is significant. At a significance level of 5 percent, the T-test result for the difference in 

means between 1870 and 1964 and 1965–93 is 6.80, which 

is greater than the p-value of 1.661; therefore, the increase in 

rainfall intensity from 1870 to 1964 and from 1965 to 1993 is 

significant. Rainfall intensities in the 1853–69 period, which 

immediately preceded arroyo incision, are significantly higher 

than from 1870 to 1964. Another period of rainfall intensity 

beginning in 1965 is also significantly higher than the preceding rainfall.

Low-intensity rainfall, which supports vegetation growth, 

decreased significantly after 1940 in the number of days for 

both summer and non-summer rainfall (fig. 2C,D). T-tests 

performed on low-intensity rainfall data show a significant 

decrease after 1940. If rainfall intensity is a triggering mechanism for arroyo cutting, then rainfall since 1967 may indicate 

that climatic factors are again favorable for arroyo incision in 

this part of New Mexico.

Channel and Hillslope Processes

Channel Cross-Sectional Resurveys

In 1993 and 1997, 51 of the original 79 cross sections 

were located and resurveyed in the four watersheds (fig. 1B). 

Thirty-five of the 51 cross sections are located in the main 

channel Arroyo de los Frijoles watershed; 16 of these 35 cross 

sections are where Leopold and others (1966) made full crosssectional surveys (table 3, fig. 4), and 19 are cross sections 

where only one original channel elevation was investigated—

the elevation at the scour chain. Sixteen cross sections in 

Coyote C. Arroyo, Gunshot Arroyo, and Morning Walk Wash 

(table 3, fig. 4) are where original full cross-sectional surveys 

were made, and these cross sections were resurveyed in 1993.

In the upper section of Morning Walk Wash, three 

channels were surveyed in 1993 between the left-bank and 

right-bank steel bars and in the lower section, two channels 

were surveyed between the left-bank and right-bank steel bars 

(fig. 4BB,CC). For the purpose of discussion, each channel is 

considered a separate cross section. The total number of full 

cross sections surveyed in the four watersheds was 32. 

Elevation accuracy was determined for 41 of the 51 resurveyed cross sections (appendix 1). The three cross sections in 

the Morning Walk Wash upper section were tied into the same 

datum as the two cross sections in the Morning Walk Wash 

lower section (fig. 4BB,CC). Information was insufficient to 

assess elevation control (appendix 1) in seven cross sections. 

Cross sections 1, 5, 22, and 25 (figs. 1 and 4A,D,J,L) indicate 

that using one intact steel bar was sufficient. For cross sections 

8 (LW-16), 9 (LW-17), and 16 (CS-40) (fig. 1), interpretations 

on channel change were based on one steel bar; however, there 

may be some error in these interpretations.

Of the 41 cross sections assessed for elevation control, 

8 cross sections (20 percent) had no measurable differences in 

elevation, 23 (56 percent) had differences ranging from greater 

than 0 to 1 cm, 6 (15 percent) had differences in elevation 

ranging from greater than 1 to 2 cm, and 4 (10 percent) had 

differences in elevation ranging from greater than 2 to 3 cm 

(appendix 1). The average difference in elevation for all 41 

cross sections was 0.8 + 0.8 cm, which is within the normal 

surveying error of 1.5 cm (Kissam, 1978).

The channels in the four watersheds are not deep, narrow 

trenches typical of many arroyos in the Southwest presumably 

because the bed material is composed of sand with little silt 

and clay. The resurveyed cross sections represent a variety of 

channel sizes, ranging in width from less than 2 to about 60 m 

and ranging in depth from about 0.2 to 3.0 m (fig. 4; table 4). 

The original surveyed widths and depths are not much different from those in the resurveys (tables 3 and 4). 

Changes in Cross-Sectional Area

Of the 32 full cross sections resurveyed in the four 

watersheds, 20 cross sections (62 percent) increased in 

cross-sectional area and 12 (38 percent) decreased in area 

(table 3). The average change in cross-sectional area was 

erosion of 0.27 m2 (table 4) or 4 percent of the original 

channel area, a relatively small value. For the 20 cross 

sections that eroded, the average increase in cross-sectional 

area was 2.20 m2 or 22 percent of the original cross-sectional 

area, with a standard deviation of 3.63 m2. For cross sections 

that deposited sediment, the average decrease in crosssectional area was 2.93 m2

 or 26 percent of the original area, 

with a standard deviation of 2.49 m2. The average erosion 

of 2.20 m2 and deposition of 2.93 m2 are so small that the 

changes in cross-sectional areas are considered insignificant.

The average change in cross-sectional area of all cross 

sections in Arroyo de los Frijoles was erosion of 1.81 m2

(10 percent of its channel area), in Morning Walk Wash was 

0.57 m2 (19 percent of its channel area), and in Gunshot 

Arroyo was 0.73 m2 (17 percent of its channel area) (table 4). 

Coyote C. Arroyo had an average decrease in cross-sectional 

area resulting from sediment deposition of 4.45 m2 or 34 percent of its channel area (fig. 5A). The weighted change in 

cross-sectional area for Arroyo de los Frijoles was erosion of 

4.87 m2 (table 4) over a distance of 9,191 m of channel length, 

which corresponds to a volume of 44,760 m3. For Coyote C. 

Channel and Hillslope Processes 15

T , (4) X A X B –

S

2

(1 n A n B ⁄ + )

= -------------------------------------------------
Figure 4. Survey cross sections in Arroyo de los Frijoles watershed (A to P), Coyote C. Arroyo (Q to V), Gunshot Arroyo 

(W to AA), and Morning Walk Wash (BB to CC). Location of cross sections in figure 1B.

16 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 4. Survey cross sections in Arroyo de los Frijoles watershed (A to P), Coyote C. Arroyo (Q to V), Gunshot Arroyo 

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Channel and Hillslope Processes 17

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Figure 4. Survey cross sections in Arroyo de los Frijoles watershed (A to P), Coyote C. Arroyo (Q to V), Gunshot Arroyo 

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18 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 4. Survey cross sections in Arroyo de los Frijoles watershed (A to P), Coyote C. Arroyo (Q to V), Gunshot Arroyo 

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Channel and Hillslope Processes 19

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20 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Table 3. Characteristics of resurveyed cross sections between original survey and resurvey in 1993–97.—Continued

[m, meter; m/m, meters per meter; m2, square meter. A positive value in thalweg elevation indicates aggradation; a negative value means the 

cross section has eroded and increased in area. Only cross sections with original full cross-sectional surveys have a width and depth listed, 

--, no data]

Cross-section 

number and name 

(figure 1)

Date of surveys

Taped 

distance 

from 

divide 

(m)

Original 

width 

(m)

Original 

depth 

(m)

Widthto-depth 

ratio 

(m/m)

Change in 

thalweg 

elevation 

(m)

Change in 

crosssectional 

area 

(m2)

Percent 

change 

in crosssectional 

area

Arroyo de los Frijoles

SWT-CS1 8/1958–6/1993 203 3.5 0.87 4.1 -0.03 0.42 21

SWT-CS2 8/1958–6/1993 284 1.8 0.28 6.2 -0.14 0.11 41

SWT-CS3 8/1958–6/1993 305 7.2 0.35 20.6 -0.18 0.41 22

LW-Chain 4 8/1959–5/1993 563 -- -- -- 0.22 -- --

NFA-Upper 8/1958–6/1993 819 11.0 0.26 42.6 0.16 -0.63 -9

NFA-Lower 8/1958–6/1993 912 3.7 0.23 16.0 0.25 -1.09 -58

Chain section 15 8/1959–5/1993 1,642 -- -- -- -0.16 -- --

LW-16 8/1959–5/1993 1,970 -- -- -- 0.09 -- --

LW-17 8/1959–5/1993 2,278 -- -- -- 0.38 -- --

LW-18 8/1959–5/1993 2,552 -- -- -- 0.19 -- --

LW-19 8/1959–5/1993 2,721 -- -- -- -0.36 -- --

LTR 20-24 8/1958–6/1993 2,906 13.1 0.61 21.5 -1.53 8.14 59

LTR 30-33 8/1958–6/1993 2,955 13.4 1.05 12.8 -1.34 11.39 85

LW-35 8/1959–5/1993 3,557 -- -- -- -0.35 -- --

LW-37 8/1959–5/1993 4,115 -- -- -- -0.25 -- --

CS-40 8/1959–5/1993 5,006 -- -- -- -0.09 -- --

CS-45 8/1960–6/1993 6,732 -- -- -- 0.08 -- --

CH49 8/1960–6/1993 7,376 -- -- -- -0.19 -- --

Frijoles range 1 8/1958–9/1997 7,417 42.4 1.43 29.7 -0.02 0.85 2

CH51 8/1960–5/1993 7,437 -- -- -- -0.19 -- --

MPR 52-59 7/1958–5/1993 7,452 49.4 1.99 24.8 -0.04 2.39 3

Frijoles range 3 8/1958–9/1997 7,482 30.5 1.18 25.9 -0.22 0.23 1

CH61 11/1958–5/1993 7,504 -- -- -- -0.60 -- --

Frijoles range 4 8/1958–9/1997 7,515 25.0 0.37 68.3 0.05 -1.07 -3

Frijoles range 5 8/1958–9/1997 7,547 31.1 0.70 44.2 0.03 0.03 0

Frijoles range 6 8/1958–9/1997 7,580 30.3 1.17 25.8 0.08 -1.56 -5

LW-64 11/1958–6/1993 7,596 -- -- -- 0.10 -- --

Frijoles range 7 8/1958–9/1997 7,612 27.7 0.73 37.8 0.11 -0.37 -1

LW-75 8/1959–5/1993 7,751 -- -- -- -0.52 -- --

LW-76 11/1958–5/1993 7,782 -- -- -- -0.02 -- --

LW-77 11/1958–5/1993 7,812 -- -- -- -0.08 -- --

LW-79 8/1959–5/1993 7,873 -- -- -- 0.15 -- --

LW-82 1958–6/1993 8,687 -- -- -- -0.02 -- --

HMR-83 8/1958–6/1993 8,902 57.0 2.06 27.7 -0.11 12.24 10

SPR 84-88 11/1958–6/1993 9,394 17.1 0.93 18.4 0.27 -2.49 -14

Channel and Hillslope Processes 21
Table 3. Characteristics of resurveyed cross sections between original survey and resurvey in 1993–97.—Continued

[m, meter; m/m, meters per meter; m2, square meter. A positive value in thalweg elevation indicates aggradation; a negative value means the 

cross section has eroded and increased in area. Only cross sections with original full cross-sectional surveys have a width and depth listed, 

--, no data]

Cross-section 

number and name 

(figure 1)

Date of surveys

Taped 

distance 

from 

divide 

(m)

Original 

width 

(m)

Original 

depth 

(m)

Widthto-depth 

ratio 

(m/m)

Change in 

thalweg 

elevation 

(m)

Change in 

crosssectional 

area 

(m2)

Percent 

change 

in crosssectional 

area

Coyote C. Arroyo, Gunshot Arroyo, and Morning Walk Wash

ACC-6 7/1961–5/1993 674 7.2 1.38 5.2 -0.12 0.95 13

ACC-5 7/1961–5/1993 803 8.0 1.23 6.6 0.27 -0.76 -11

ACC-4 7/1961–5/1993 892 9.4 1.48 6.4 0.44 -1.97 -20

ACC-3 7/1961–5/1993 1,009 13.1 1.67 7.9 0.80 -6.65 -37

ACC-2 7/1961–5/1993 1,045 8.8 0.98 9.0 0.91 -5.83 -52

ACC-1 7/1961–5/1993 1,100 14.9 0.89 16.8 0.98 -12.46 -96

Gunshot Arroyo 

Station 468

7/1962–6/1993 208 3.9 0.90 4.3 -0.20 0.73 21

Gunshot Arroyo Station 

417 top of headcut

7/1962–6/1993 223 2.7 0.76 3.6 -0.13 0.59 16

Gunshot Arroyo Station 

417 bottom of headcut

7/1962–6/1993 223 2.7 1.17 2.3 -0.03 0.90 22

Gunshot Arroyo 

Station 230

7/1962–6/1993 280 7.7 1.17 6.6 0.05 0.17 3

Gunshot Arroyo 

Station 25

7/1962–6/1993 343 5.2 0.91 5.7 -0.13 1.24 21

Morning Walk WashUpper Section North7/1961–6/1993 165 7.6 1.09 7.0 -0.08 0.60 28

Morning Walk WashUpper Third Gully7/1961–6/1993 183 6.1 1.02 6.0 -0.03 0.79 20

Morning Walk WashUpper Section South7/1961–6/1993 210 5.2 0.70 7.4 -0.16 0.51 10

Morning Walk WashLower North7/1961–6/1993 213 13.1 0.58 22.6 0.04 -0.30 -5

Morning Walk WashLower South7/1961–6/1993 265 5.8 0.48 12.0 -0.22 1.23 33

22 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Table 4. Summary of resurveyed channel characteristics in 1993 and 1997 in relation to Leopold and others’ (1966) original channel 

surveys in Arroyo de los Frijoles, Coyote C. Arroyo, Gunshot Arroyo, and Morning Walk Wash.

[m2, square meter; --, no data]

Watershed 

(figure 1)

Drainage area 

(square 

kilometers)

Number of 

cross sections 

resurveyed for 

cross-sectional 

area

Range of 

width 

(meters)

Range of 

depth

(meters)

Number of cross sections 

in cross-sectional area

Decreasing Increasing 

Main Channel Arroyo 

de los Frijoles

9.71 16 1.2 to 60 0.19 to 3.0 6 10

Arroyo Coyote C. 0.16 6 7.2 to 14.9 0.85 to 1.5 5 1

Morning Walk Wash 0.03 5 5.2 to 13.4 0.48 to 1.1 1 4

Gunshot Arroyo 0.09 5 2.7 to 7.7 0.68 to 1.2 0 5

Total 32 1.2 to 60 0.19 to 3.0 12 20

Average change 

in cross-sectional 

area (m2) (positive 

numbers indicate 

erosion)

Number of cross 

sections resurveyed in 1993 and 

1997 for changes 

in thalweg 

elevation

Number of cross 

sections that 

aggraded

Number of 

cross sections that 

degraded

Average change 

in channel elevation (meters) 

(positive numbers indicate 

aggradation)

Weighted 

change in 

cross-sectional 

area (m2) (positive numbers 

indicate 

degradation)

Percent change 

in cross-sectional 

area (positive 

numbers indicate 

degradation)

1.81 35 13 22 -0.13 4.87 10

-4.45 6 5 1 0.55 -3.15 -34

0.57 5 2 3 -0.09 -- 17

0.73 5 1 4 -0.09 -- 17

0.27 51 20 31 -0.04 -- 4

Arroyo, the weighted change in cross-sectional area was 

deposition of 3.15 m2 (table 4) over a distance of 427 m of 

channel length, which corresponds to a volume of 1,345 m3

or 420 m3 per year. Using a dry density of sediment of 

1,180 kg/m3 for Coyote C. Arroyo yields a net deposition 

of 49.6 metric tonnes/yr. 

Changes in Thalweg Elevation

Of the 32 full cross sections resurveyed in the four 

watersheds, 18 (56 percent) degraded or showed a decrease in 

thalweg elevation and 14 (44 percent) aggraded (table 3). The 

average change in thalweg elevation was about -0.01 m. In 

general, as channels aggrade, cross-sectional areas decrease. 

However, at two locations (Gunshot Arroyo Station 230, 

and Frijoles Range 5) the cross sections both aggraded and 

increased in cross-sectional area. Therefore, as these channels aggraded they also widened and showed a net increase in 

cross-sectional area.

Resurveys of the 51 cross sections in channels that had 

a survey at only one station in the channel, combined with 

the surveys for full cross-sectional surveys, indicate that 31 

(61 percent), had degraded (table 4). The average change in all 

51 cross sections was degradation of 0.04 m or 1.14 mm/yr. 

The average decrease in elevation of the 31 degrading cross 

sections was 0.25 m with a standard deviation of 0.34 m. 

The average increase in elevation of the 20 aggrading cross 

sections was 0.28 m with a standard deviation of 0.28 m. The 

largest degradation recorded was 1.53 m in Arroyo de los Frijoles at cross section LTR 20-24 (table 3). The largest measured aggradation was 0.98 m in Coyote C. Arroyo at cross 

section ACC-1 (table 3).

Comparison of the 1993 resurveys with the original 

surveys for Gunshot Arroyo and Morning Walk Wash showed 

that each had an average channel degradation of 0.09 m 

(table 4). Coyote C. Arroyo showed an average aggradation 

of 0.55 m (table 4). 

The main channel Arroyo de los Frijoles was the focus of 

many resurveys in the original study. Thalweg elevations were 

obtained from previous surveys conducted in 1958–60, 1962, 

1964, 1966, and 1968 (U.S. Geological Survey, unpublished 

data). Thalweg elevations were resurveyed in 1993 and 1997 

(table 5). Average changes in thalweg elevation and channel 

length-weighted change for Arroyo de los Frijoles from 

surveys in 1962, 1964, 1966, and 1993 and 1997, compared 

with the original thalweg survey in 1958–60, are listed in 

table 6. Arroyo de los Frijoles showed an average degradation 

of 0.13 m (table 4; fig. 5B). The channel length-weighted 

change in thalweg elevation from the original survey to 

1993 and 1997 was -0.12 m for the main channel Arroyo de 

los Frijoles (table 6). Comparison of the resurveys showed 

aggradation from the original survey (performed from 1958 

Channel and Hillslope Processes 23
Table 5. Elevation of thalweg at 63 cross sections from 1958 to 1997 in the main channel Arroyo de los Frijoles.—Continued

[-- indicates the channel elevation was not surveyed. Elevations are in meters (m) above sea level unless noted with ‘ * ‘, which indicates arbitrary elevation]

Cross-sectionnumber or letter 

and name

Scourchain 

number

Taped distance from 

divide at 

Slopewash 

Tributary 

(m)

Date of 

original 

thalweg 

elevation

Thalweg elevation from

 1958–60 

surveys 

(m)

1962 

resurveys 

(m)

1964 

resurveys 

(m)

1966 

resurveys 

(m)

1968 

resurveys

(m)

1993 and 

1997 

resurveys

(m)

SWT-CS1 1 203 11/1958 2,201.24 2,201.34 2,201.28 2,201.24 -- 2,201.21

SWT-CS2 2 284 11/1958 2,197.74 2,197.76 2,197.80 2,197.72 -- 2,197.61

SWT-CS3 3 305 11/1958 2,197.12 2,197.16 2,197.15 2,197.10 -- 2,196.94

LW-Chain 4 4 563 8/1959 2,189.97 2,190.05 2,190.00 2,190.08 -- 2,190.18

NFA-Upper 6–9 819 11/1958 2,183.75 2,183.65 2,183.75 2,183.76 2,183.75 2,183.91

NFA-Lower 10–13 912 11/1958 2,181.79 2,181.88 2,181.91 2,181.83 2,181.85 2,182.04

LW-14 14 1,321 8/1959 2,170.65 2,170.69 2,170.54 2,170.48 -- --

Chain section 15 15 1,642 8/1959 2,167.21 2,167.21 2,167.19 2,167.07 -- 2,167.05

LW-16 16 1,970 8/1959 2,161.36 2,161.44 2,161.57 2,161.31 -- 2,161.45

LW-17 17 2,278 8/1959 2,155.28 2,155.35 2,155.37 2,155.18 -- 2,155.66

LW-18 18 2,552 8/1959 2,151.29 2,150.70 2,150.91 2,150.12 -- 2,151.48

LW-19 19 2,721 8/1959 2,148.00 2,148.13 2,148.14 -- -- 2,147.64

LTR 20-24 20–24 2,906 11/1958 2,144.73 2,144.82 2,144.87 2,144.51 2,144.65 2,143.20

LTR 25-29 25–29 2,926 8/1958 2,144.38 2,144.56 2,144.62 2,144.15 2,144.35 --

LTR 30-33 30–33 2,955 11/1959 2,143.97 2,144.21 2,144.18 2,143.87 2,143.98 2,142.62

LW-34 34 3,103 8/1959 2,141.95 2,141.96 2,141.92 2,141.81 -- --

LW-35 35 3,557 8/1959 2,134.05 2,133.94 2,133.87 2,134.02 -- 2,133.69

LW-36 36 3,840 8/1959 2,129.30 2,129.35 2,129.22 2,129.26 -- --

LW-37 37 4,115 8/1959 2,124.26 2,124.48 2,124.48 -- -- 2,124.01

LW-38 38 4,402 8/1959 2,119.30 2,119.41 2,119.34 2,119.34 -- --

LW-39 39 4,605 8/1959 2,114.25 2,114.42 2,114.33 2,114.32 -- --

CS-40 40 5,006 8/1959 2,109.75 2,109.79 2,109.73 2,109.87 -- 2,109.66

LW-41 41 5,038 8/1959 2,105.16 2,104.85 2,104.81 2,104.50 -- --

LW-42 42 5,955 8/1959 2,099.86 2,099.97 2,099.74 2,099.90 -- --

LW-43 43 6,046 8/1959 2,095.70 2,095.50 2,095.60 2,095.70 -- --

CS-45 45 6,732 8/1960 2,085.27 2,085.30 2,085.30 2,085.24 -- 2,085.15

LW-46 46 7,046 8/1959 2,079.80 2,079.89 2,080.03 2,079.89 -- --

LW-47 47 7,315 11/1958 2,075.42 2,075.54 2,075.59 2,075.45 -- --

LW-48 48 7,346 11/1958 2,074.96 2,074.99 2,075.00 2,075.05 -- --

CH-49 49 7,376 11/1958 2,074.40 2,074.33 2,074.42 2,074.46 -- 2,074.22

LW-50 50 7,407 11/1958 2,073.81 2,073.81 2,073.80 2,073.68 -- --

Frijoles range 1 7,417 8/1958 42.06 * -- -- -- -- 42.04

CH-51 51 7,437 0.01 2,073.39 2,073.41 2,073.37 2,073.31 -- 2,073.20

MPR 52-59 52–59 7,452 7/1958 2,073.21 2,073.20 2,073.12 2,073.13 2,073.20 2,073.17

LW-60 60 7,474 11/1958 2,072.88 2,072.98 2,073.02 2,073.01 -- --

24 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Table 5. Elevation of thalweg at 63 cross sections from 1958 to 1997 in the main channel Arroyo de los Frijoles.—Continued

[-- indicates the channel elevation was not surveyed. Elevations are in meters (m) above sea level unless noted with ‘ * ‘, which indicates arbitrary elevation]

Cross-sectionnumber or letter 

and name

Scourchain 

number

Taped distance from 

divide at 

Slopewash 

Tributary 

(m)

Date of 

original 

thalweg 

elevation

Thalweg elevation from

 1958–60 

surveys 

(m)

1962 

resurveys 

(m)

1964 

resurveys 

(m)

1966 

resurveys 

(m)

1968 

resurveys

(m)

1993 and 

1997 

resurveys

(m)

CH-61 61 7,504 11/1958 2,072.92 2,072.45 2,072.47 2,072.57 -- 2,072.31

Frijoles range 4 7,515 8/1958 40.11 * -- -- -- -- 40.16

LW-62 62 7,535 11/1958 2,071.82 2,071.80 2,071.86 2,071.93 -- --

Frijoles range 5 7,547 8/1958 39.65 * -- -- -- -- 39.69

LW-63 63 7,565 11/1958 2,071.20 2,071.29 2,071.33 2,071.28 -- --

Frijoles range 6 7,580 8/1958 39.08 * -- -- -- -- 39.16

LW-64 64 7,596 11/1958 2,070.62 2,070.69 2,070.83 2,070.78 -- 2,070.72

Frijoles range 7 7,612 8/1958 38.55 * -- -- -- -- 38.66

LW-65 65 7,626 11/1958 2,070.29 2,070.33 2,070.35 2,070.39 -- --

LW-66 66 7,657 11/1958 2,069.98 2,069.84 2,069.92 2,069.93 -- --

MPR 67-72 67–72 7,678 7/1958 2,069.18 2,069.38 2,069.41 2,069.42 2,069.42 --

LW-73 73 7,690 1958 2,069.60 2,069.29 2,069.33 2,069.35 -- --

LW-74 74 7,721 1958 2,069.17 2,068.78 2,068.92 2,068.92 -- --

LW-75 75 7,751 1958 2,068.72 2,068.22 2,068.42 2,068.49 -- 2,068.21

LW-76 76 7,782 11/1958 2,067.81 2,067.65 2,067.82 2,067.90 -- 2,067.79

LW-77 77 7,812 11/1958 2,067.08 2,067.20 2,067.20 2,067.18 -- 2,067.00

LW-78 78 7,843 11/1958 2,066.50 2,066.67 2,066.59 2,066.53 -- --

LW-79 79 7,873 1958 2,066.14 2,066.22 2,066.23 2,066.21 -- 2,066.29

LW-80 80 8,086 1958 2,062.75 2,062.76 -- -- -- --

LW-81 81 8,377 1958 2,058.01 2,057.88 2,057.90 -- -- --

LW-82 82 8,687 1958 2,052.71 2,052.70 2,052.68 -- -- 2,052.68

HMR-83 83 8,902 9/1958 2,049.32 2,049.42 2,049.29 -- -- 2,049.21

SPR 84-88 84–88 9,394 11/1958 2,040.49 2,040.68 2,040.57 -- -- 2,040.75

SPR 89 89 9,510 1958 2,038.90 2,039.13 2,038.96 -- -- --

SPR 90 90 9,754 1958 2,035.82 2,036.24 2,036.36 -- -- --

Channel and Hillslope Processes 25
Table 6. Average changes and channel length-weighted changes in thalweg elevations for the main 

channel Arroyo de los Frijoles

[(Leopold and others, 1966)]

Time period

 Average change 

in thalweg 

elevation 

(meters)1

 Channel lengthweighted change in 

thalweg elevation 

(meters)1

Length of 

channel used 

in weighting 

(meters)

Number of 

cross 

sections

1962 to original survey 0.01 0.02 9,551 55

1964 to original survey 0.02 0.00 9,551 54

1966 to original survey -0.06 -0.11 7,670 46

1993 and 1997 to original survey -0.13 -0.12 9,191 35

1

Negative value indicates degradation; positive value indicates aggradation.

to 1960) to 1962 and 1964. Degradation occurred from the 

original survey to 1966 and from the original survey to 1993 

and 1997 (table 6).

Full cross-sectional surveys made in 1993 and 1997 compared with the original surveys showed little change. In cross 

sections in which only 1 station in the channel was surveyed 

in the original study (n = 19), 13 showed slight degradation of 

about 0.01 m/yr. Because the entire data set essentially showed 

no change, the resurvey did not establish a clear progressive 

trend in aggradation or degradation.

General trends in channel changes reported for 1958–64 

(Leopold and others, 1966) did not continue through the next 

35–39 years (figs. 6 and 7). For the main channel Arroyo de 

los Frijoles, the newer surveys indicate slight degradation, 

whereas the 1958–64 study showed a consistent trend in 

aggradation (tables 4 and 6). The average aggradation from 

1958 to 1964 was 0.012 m/yr (Leopold and others, 1966, 

p. 219). Twenty-nine of the 35 resurveyed cross sections in the 

main channel Arroyo de los Frijoles were used in a comparison of channel aggradation and degradation with the original 

surveys (1958–64) (fig. 7). Channel changes for 1958–64 

were not published for six of the resurveyed cross sections 

(19, 22, 24, 25, 26, and 28). Thirteen (45 percent) cross sections showed the same trend as in the original study. Six cross 

sections that were aggrading in the original survey continued 

to aggrade by the 1993 and 1997 resurveys, and seven cross 

sections that were degrading in the original survey continued 

to degrade by the 1993 and 1997 resurveys (fig. 7).

Along the main channel Arroyo de los Frijoles, changes 

in channel elevation periodically alternate from aggradation to 

degradation (fig. 8). The changes in channel elevation during 

1993–97 compared with those during the original survey show 

several adjacent cross sections with the same trend in channel-elevation change over time (fig. 8). The alternating trend 

in channel-elevation change over time may reflect the sandy 

nature of the channel, the localized nature of streamflow and 

scour in an ephemeral channel, and human disturbance. 

All 35 surveyed full cross sections show no relation 

between aggradation and degradation either to distance from 

the watershed divide or to width-to-depth ratio (fig. 9). Miller 

and Leopold (1961), in an unpublished preliminary report 

on channel changes in Arroyo de los Frijoles from 1958 to 

1960, reported similar observations that upstream areas are 

not characterized by degradation and downstream areas are 

not characterized by aggradation. In arroyos investigated on 

Zuni Reservation, New Mexico, an increase in channel erosion 

and an increase in cross-sectional area were observed with a 

decrease in width-to-depth ratios (Gellis, 1998). 

Coyote C. Arroyo (fig. 1) showed both aggradation and 

degradation between the original survey and the 1993 resurvey, part of which may be related to the movement of a large 

headcut (fig. 10). In 1961, four headcuts were identified in the 

Coyote C. Arroyo channel. The largest headcut, 523 m from 

the watershed divide, was studied in detail between 1961 and 

1964. In 1993 the headcut had moved approximately 22 m 

upstream or 0.69 m per year. In Coyote C. Arroyo, cross sections that are farther away from the headcut have aggraded 

the most (fig. 10). This trend in aggradation may be due to the 

base-level effect of the dam or to the movement of a headcut.

Arroyo channels deepen by the upstream migration of 

a headcut (Gellis, 1998). Channel-top width-to-depth ratios 

are typically lower in reaches immediately downstream from 

a headcut than upstream because of the increased depth. For 

example, in Oaklimeter Creek, an incised channel in Mississippi, top width-to-depth ratios generally were 4.7 in the 

channel reach upstream from the headcut and 3.8 in the 

channel reach immediately downstream (Schumm and others, 

1984). Top width-to-depth ratios ranged from 2.29 to 3.63 

downstream from headcuts in the three watersheds on the 

Zuni Reservation, New Mexico (Gellis, 1998). Immediately 

upstream from the headcut, the channel had not deepened and 

its top width-to-depth ratios were higher, ranging from 3.96 to 

8.21. As the headcut advances upstream, the channel aggrades 

downstream. For gullies in Israel, Seginer (1966) found a 

positive correlation between the distance from the headcut 

and the downstream gully cross-sectional area. In Coyote 

C. Arroyo, a similar process was observed that aggradation 

occurred in reaches furthest from the headcut.

26 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Figure 5. Change in (A) percent cross-sectional area and (B) thalweg 

elevation.

Channel and Hillslope Processes 27

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Figure 6. Aggradation and degradation of 35 cross sections resurveyed in 1997 compared with Leopold and others’ (1966) 

original survey from 1958 to 1964 at (A) main channel Arroyo de los Frijoles, and (B) Main Project reach in Arroyo de los Frijoles. Location of reaches in figure 1.

28 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 7. Channel elevation changes for the main channel Arroyo de los Frijoles 

at the cross sections resurveyed in 1993 and 1997 compared with Leopold and 

others’ (1966) original 1958–64 surveys.

Figure 8. Adjacent cross sections in the main channel Arroyo de los Frijoles 

showing similar channel changes in aggradation or degradation of the thalweg elevation from Leopold and others’ (1966) survey to resurvey conducted 

in 1993 and 1997. Cross section numbers in parentheses. Location of cross 

sections shown in figure 1.

Channel and Hillslope Processes 29

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If arroyo incision is related to increases in precipitation intensity (Leopold, 1951; Leopold and others, 1966), 

then Santa Fe precipitation records indicate that climatic 

factors may be favorable for arroyo incision in this part of 

New Mexico. The 1993–98 channel resurveys showed little 

change in channel-bed elevation between 1993 and the 1950’s, 

indicating that channels have not yet responded to a higher 

frequency of intense rainfall. Furthermore, recent data for 

other arroyo watersheds in New Mexico indicate that arroyos 

are aggrading. Results of resurveys between 1992 and 1994 

for 85 channel cross sections in three subbasins of the Rio 

Nutria watershed on Zuni Reservation indicate that 72 percent 

of cross sections aggraded (Gellis, 1998). Replicate arroyo 

surveys of the Rio Puerco in two reaches indicate aggradation 

of 2.55 and 0.7 m, from 1936 to 1995 and from 1977 to 1994, 

respectively (Elliott and others, 1999).

Changes in Gunshot Arroyo

The longitudinal profile of Gunshot Arroyo (fig. 11A,B) 

was originally surveyed in 1962 and resurveyed in 1998. 

The profile shows little change between 1962 and 1998 

(fig. 11A,B): for the entire profile (350 m), the average 

change in channel elevation was degradation of 0.08 m 

or 2.22 mm/yr. Maximum degradation of the channel 

was 0.58 m, 250 m upstream from the mouth (fig. 11C). 

Maximum aggradation was 0.35 m, 327 m upstream from 

the mouth. Two cross sections at station 417 were surveyed 

immediately downstream and upstream from a headcut about 

127 m upstream from the mouth (fig. 11A). The headcut is 

in bedrock of the Santa Fe Group of Tertiary age. The 1998 

resurvey indicated that the headcut had eroded very little. 

In 1962 the headcut depth was 0.41 m; in 1998 the depth 

was 0.33 m. Resurveys in 1993 indicated widening of the 

channel at station 417 and an increase in cross-sectional area 

of 0.90 m2 (22 percent) and 0.59 m2 (16 percent) at station 

468 downstream and station 417 upstream from the headcut, 

respectively (fig. 4; fig. 11C; table 3).

Channel-Bed Scour and Fill

Measurement of channel scour and fill that continued 

after the Leopold and others (1966) study are presented 

here (fig. 12). Between 1964 and 1968, 371 measurements 

of scour and 32 measurements of fill were made. One 

measurement of scour was missed on June 10, 1965, but a 

measurement of fill was recorded. Scour is measured as the 

difference between the elevation of the bend in the scour 

chain and the previous surveyed channel-bed elevation. 

Figure 10. Change in thalweg elevation between the Leopold and 

others’ (1966) original 1961 survey and the 1993 resurvey of channel 

cross sections in Coyote C. Arroyo.

Figure 9. Change in thalweg elevation compared with (A) 

distance downstream from watershed divide for all 1993 and 1997 

resurveyed cross sections, and (B) width-to-depth ratios for 32 

cross sections with full cross-sectional surveys.

30 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico ��������������������������������������

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Figure 11. Gunshot Arroyo (A) resurvey of longitudinal profile, 1988, (B) from station 0 to 200 meters and from station 

200 to 350 meters, and (C) channel changes at station 417 bottom of headcut and station 417 top of headcut. The longitudinal profile does not extend to the watershed divide.

Channel and Hillslope Processes 31

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Figure 12. Scour-chain measurements of (A) scour, 1964–68, (B) fill, 1964–68, (C) scour, 1993, and (D) fill, 1993.

32 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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If scour occurred, the difference in elevation should be 

positive. Twenty-seven of the 371 measurements of scour 

had values between -0.003 and -0.09 m. Twenty-two scour 

chains measured from -0.003 to -0.091 m were considered 

within survey error and given a value of zero. The remaining 

five measurements (-0.03, -0.04, -0.04, -0.05, -0.09) were 

considered in error and were not used.

The average scour from the 366 measurements was 

0.14 ± 0.14 m. About 50 percent of the scour measurements 

were 0.10 m or less; 11 percent were greater than 0.35 m 

(fig. 12A). The greatest scour (0.87 m) was measured 

June 7, 1965, at cross section LW-18 (fig. 1). 

From 1964 to 1968, 372 fill measurements were 

recorded using scour chains. One fill measurement from 

1964 to 1968 showed the top of the scour chain to be 0.08 m 

higher than the current bed elevation. This measurement was 

given a value of zero. The average fill at all 33 chains was 

0.13 m ± 0.11 m. About 47 percent of the fill measured from 

1964 to 1968 was less 0.10 m or less (fig. 12B), and about 

11 percent of the fill was greater than 0.25 m. The greatest 

fill (0.72 m) was recorded June 10, 1965, at cross section 

MPR 67-72.

Fifty-four discharge measurements were made from 

1964 to 1968 at three crest-stage stations in the main channel Arroyo de los Frijoles: North Frijoles reach, Locust Tree 

reach, and Main Project reach (figs. 1 and 3). Peak-discharge 

measurements were reported for each chain survey at cross 

sections near the streamflow-gaging stations NFA-Upper, 

NFA-Lower, LTR 20-24, LTR 30-33, MPR 52-59, and MPR 

67-72. These cross sections all contain more than one scour 

chain, and a mean depth of scour was calculated for these 

three cross sections by averaging the values of scour from 

all chains in a cross section. A plot of mean values of scour 

compared to peak discharge for these unpublished data 

(54 measurements) combined with data from Leopold and 

others (1966, fig. 159, p. 222) (83 measurements) indicates 

results similar to the original study; the average depth of 

scour is directly proportional to the square root of discharge 

per unit width of channel (fig. 13).

In 1993, 33 of the original scour chains were located 

in 20 cross sections in the Arroyo de los Frijoles watershed. 

Prior to 1993, 3 of the 33 chains were measured in 1964, 

14 were measured in 1966, and 16 were measured in 1968. 

With the exception of cross section 3 at Slopewash Tributary 

SWT-CS3, all cross sections showed scour. Scour ranged 

from 0 to 0.52 m; average scour of all 33 chains was 0.24 ± 

0.13 m (fig. 12C). Fifty-four percent of the scour ranged 

from 0 to 0.25 m (fig. 12C), and 15 percent of the scour 

measured was 0.10 m or less, a smaller percentage than 

measured from 1964 to 1968 (fig. 12A–C). Twelve percent 

of the scour was greater than 0.4 m. The greatest scour 

(0.52 m) was measured at cross section LW-15.

Fill measured atop the chains in Arroyo de los Frijoles 

in 1993 ranged from 0.08 to 0.54 m (fig. 12D); average 

deposition was 0.29 ± 0.12 m. Thirty-three percent of 

the fill measured was less than 0.25 m, and 15 percent 

of the fill was greater than 0.4 m. The greatest fill (0.54 m) 

was measured at cross section LW-15. The apparent higher 

frequency of scour and fill in the intermediate ranges (0.10 

to 0.40 m) from 1968 to 1993 (fig. 12C–D) may reflect the 

longer time period between measurements and a higher 

probability of more frequent and higher flow events to 

mobilize sediment in the bed. The higher percentage of lower 

values measured from 1964 to 1968 is expected because 

attempts were made to measure the chains immediately after 

each runoff event, regardless of the magnitude.

The 1993 scour measurements were recorded relative to 

the last surveyed elevation of the channel. Because the last 

measurements were made from 1964 to 1968, runoff events 

prior to 1993 may have raised or lowered the channel bed. The 

channel elevation immediately prior to the event that caused 

scour and fill and the chain measurement in 1993 may have 

been higher or lower than the 1964–68 channel elevation. 

Thus, the 1993 measurements may be in error. The elevation 

of the channel has not changed significantly since 1964. If the 

elevations are assumed to have remained relatively stable since 

1964–68, then the scour and fill measurements may represent 

the largest runoff event since 1964. 

Scour and fill for 1968–93 in relation to distance along 

the main channel Arroyo de los Frijoles are shown in figure 14. Also shown in figure 14 are overall thalweg net 

changes along the channel. Scour and fill were averaged for 

four cross sections containing more than one scour chain. No 

longitudinal trend in scour and fill or in net changes in the 

channel thalweg was apparent. The maximum scour (0.52 m) 

and maximum fill (0.54 m) (fig. 14A) occur at the same cross 

section (LW-15), 1,642 m downstream from the watershed 

divide at Slopewash Tributary. In 1993, the scour chain was 

not located in the cross section (LTR 20-24) that showed the 

greatest amount of thalweg degradation (1.53 m), located 

immediately downstream from a culvert 2,906 m from the 

watershed divide at Slopewash Tributary. Extreme scour may 

have removed the scour chain at this location.

Using data from flume experiments and field studies of steep, sand-bed ephemeral channels, which included 

data for Arroyo de los Frijoles, Foley (1978) concluded that 

scour occurs locally at all flows and that streambed elevation 

changes little over a longer reach. Scour and fill may alternate 

locally at several locations during a flood. The scour and fill 

were observed to be from bed-form migrations of antidunes, 

whereas the streams had flow in the upper flow regime (Foley, 

1978). The average depth of maximum scour for a cross section was not considered a good indicator of maximum flow 

conditions, and data from this study on channel scour between 

the 1950’s and 1993 may support this idea. Changes in the 

overall elevation of the main channel Arroyo de los Frijoles 

are minor, whereas local changes in channel-bed elevation can 

be greater.

Leopold and others (1966) observed that rainfall 

events are so intense and localized that only a part of the 

watershed is affected by runoff. For example, the highest 

daily rainfall recorded at Santa Fe for 1858–1993 was 92 mm 

Channel and Hillslope Processes 33
ing in 689 metric tonnes of sediment or 21.5 metric tonnes/yr. 

The average annual sediment yield for 1961–93 is 139 metric 

tonnes/km2/yr. Earlier surveys of sediment deposition from 

1961 to 1963 indicated that the deposition rate was higher in 

that period than in 1961–93 (table 7) (Leopold and others, 

1966). In 32 years, deposition decreased nearly an order of 

magnitude, from 172 to 21.5 metric tonnes/yr (table 7). Average annual rainfall did not change from 1961 to 1993 (table 1); 

therefore, changes in depositional rates are not likely due to 

changes in rainfall and runoff. Instead, deposition may be due 

to changes in the trap efficiency of the structure, which would 

decrease over time (Vanoni, 1977), and(or) to a decrease in 

sediment delivery because of upstream channel storage.

Sediment yields reported for Coyote C. Arroyo and for 

the Slopewash Tributary erosion plot are in the range of average sediment yields reported for New Mexico (table 8). The 

sediment-yield values in table 8 were obtained from suspended-sediment data that did not include bedload. If bedload 

data were included, the sediment-yield values in table 8 would 

be higher. 

on August 1, 1968, when flow was still being measured in 

Arroyo de los Frijoles. No streamflow was recorded at the 

gages. Only twice in the original study period was an increase 

in discharge observed in the downstream direction. High 

streamflow in parts of the watershed may have scoured the 

channels, and sediment may have been deposited in areas of 

infiltration.

Deposition Behind Dams and BaseLevel Experiments

Deposition Behind Dams

A resurvey of the sediment pool behind the earthen dam 

in Coyote C. Arroyo (fig. 1C and fig. 15) showed that 584 m3

of sediment was deposited between 1961 and 1993 (table 7). 

The density of sediment behind the dam is 1,180 kg/m3, resultFigure 13. Depth of scour as a function of discharge at scour-chain sections. Each point represents an 

average scour across the channel bed based on 4–10 chains per cross section. Location of reaches shown in 

figure 1.

34 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 14. Scour and fill from 1993 resurveys of scour chains at (A) main channel 

Arroyo de los Frijoles, and (B) Main Project reach in Arroyo de los Frijoles plotted with 

net change in thalweg from 1993 and 1997 resurveys. Location of reaches in figure 1.

Deposition Behind Dams and Base-Level Experiments 35

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Figure 15. Thickness map of sediment deposited at reservoir on Coyote C. Arroyo. Location of reservoir shown in figure 1C.

36 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Base-Level Experiments

By analyzing deposition behind Big Sweat Dam, Leopold 

and Bull (1979) determined that the longitudinal profile of the 

channel had changed 15.2 m upstream 2 years after construction and 24.4 m upstream after 4 years. Photographs showing 

Big Sweat Dam in 1960 shortly after construction and in 1998 

illustrating deposition behind the dam are shown in figure 16. 

From 1960 to 1964, channel slope decreased from 0.045 to 

0.033 (27 percent) (Leopold and Bull, 1979, p. 189). From 

1964 to 1974, the effect of increased base level did not extend 

beyond 30.5 m upstream, and channel slope remained at 0.033 

(Leopold and Bull, 1979, p. 189).

In 1993, Big Sweat and Little Sweat Dams were still 

intact (figs. 16, 17). Changes in the profile of deposition 

behind the dam are reported for the same cross sections as 

in the original survey. Deposition behind Big Sweat Dam 

extended about 20 m upstream to cross section O (fig. 17A,B). 

Weighted slopes of the channel from 0 to 9.1 m above the 

dam remained constant (within 0.04 m/m) from 1968 to 1993 

(table 9A). Reaches less than 5.3 m above the dam, however, 

had varying slopes from 1960 to 1993 (table 9A). The overall 

elevation of the sediment surface behind Big Sweat Dam was 

lower in 1993 than in 1968 and 1974 (fig. 17A,B). The lower 

elevation may be due to the sediment pool behind the dam filling in, which has led subsequently to local scour.

Table 7. (A) Deposition rates in the sediment pool behind the earthen dam at Coyote C. 

Arroyo, 1961–93. (B) Sedimentation rates for selected time periods at Coyote C. Arroyo.

[km2, square kilometer; m3, cubic meter]

(A)

Drainage area 

(km2)

Total sediment deposition 

(m3)

Sediment yield 

(tonnes/ km2/year)

0.155 584 139

(B)

Selected time period

1961–62 1961–63 1961–64 1961–93

Metric tonnes per year 172 98.1 69.5 21.5

Table 8. Selected summary of sediment yields in New Mexico streams.

[km2/yr, square kilometers per year; USGS, U.S. Geological Survey]

Location Period of

observation

Drainage area 

(km2)

Average annual 

sediment yield 

(metric tonnes/km2/yr)

Reference

Rio Puerco above Arroyo Chico 1949–55; 1958–95 1,088 732 USGS New Mexico Water-Data Reports

Arroyo Chico near Guadalupe 1949–55; 1979–86 3,600 487 USGS New Mexico Water-Data Reports

Rio San Jose at Correo 1949–55 6.760 71.6 USGS New Mexico Water-Data Reports

Rio Puerco at Bernardo 1948–96 19,036 212 USGS New Mexico Water-Data Reports

Rio Santa Cruz at Santa Cruz Reservoir 1929–41 238 354 Brown, 1945

Gallinas River at Storrie Reservoir near 

Las Vegas

1918–40 386 144 Brown, 1945

Jemez Creek at San Ysidro 1936–41 2,212 254 Brown, 1945

Rio (Arroyo) Salado at San Ysidro 1937–40 324 257 Brown, 1945

Rio Grande at San Marcial1 1948–73 64,128 104 USGS New Mexico Water-Data Reports

Coyote C. Arroyo 1961–93 0.155 110 Current study

Big Sweat Dam 1960–93 0.015 21.4 Current study

Little Sweat Dam 1960–93 0.0034 31.6 Current study

1

Measurements before closure of Cochiti Reservoir.

Deposition Behind Dams and Base-Level Experiments 37
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Figure 16. (A) View looking downstream toward Big Sweat Dam shortly after its construction in 1960. (B) Little Sweat 

Dam, 1960. (C) View looking downstream toward Big Sweat Dam, 1998. Location of dams shown in figure 1B.

38 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Figure 17. Successive channel-bed profiles of: (A) Entire length of channel upstream from 

Big Sweat Dam. (B) Profiles of the channel within 35 meters of the dam showing locations of 

resurveyed channel cross sections.

weighted slope decreased 0.026 m/m (53 percent) (table 9B). 

Channel-weighted slope from 0 to 11.0 m upstream from the 

dam ranged from 0.029 in 1964 to 0.027 in 1993. The interpretation of changes in Little Sweat Dam is similar to Leopold 

and Bull’s (1979) interpreted changes in Big Sweat Dam; the 

channel-weighted slope remained about constant from 1960 

to 1964 from about 9 to 23 m above the dam. The elevation of 

the sediment surface has changed little since 1964.

The 1993 resurveys and earlier surveys of Big Sweat 

Dam differ in the interpretation of channel gradients. The 

Data collected for Little Sweat Dam have not been previously published. Surveys conducted in 1962, 1964, and 1993 

are shown in figure 17. Two years after construction, the channel-bed profile had been affected by deposition about 9.3 m 

upstream from the dam (fig. 17). From 1964 to 1993, little 

deposition extended to 9.3 m upstream from the dam 

(fig. 17C,D). Channel gradients 0 to 11 m upstream have 

remained constant at about 0.028 from 1964 to 1993. By 1962, 

the channel gradient had decreased 0.011 m/m (17 percent) 

11.0 m upstream from the dam. From 1962 to 1964, the 

Deposition Behind Dams and Base-Level Experiments 39

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Figure 17. (C) Entire length of channel upstream from Little Sweat Dam. (D) Profiles of the channel within 30 meters of the dam showing locations of resurveyed 

channel cross sections.

40 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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disparity between Leopold and Bull’s (1979) determination of 

deposition to 30.5 m upstream and the value of 20 m reported 

here is due to a general lowering of the profile from 1964 to 

1993 (fig. 17). Although the trap efficiency of the dam was 

not calculated, the sediment wedge in 1993 was at the top of 

the dam; therefore, some sediment was transported downstream. The reaches close to the dam, within 5.3 m, indicate 

fluctuations in channel gradient through the period of record 

(table 9). Local steepening of the slope in these reaches may 

possibly have led to minor incision and thus the lowering of 

the profile in figure 17. The sinuosity of the thalweg has also 

increased over time and may have caused some local scour 

(fig. 18). Differences in locations through time used to survey 

the channel profile may also cause some error in duplication of 

the channel profile.

The changes in the profile of sediment deposited behind 

Big Sweat Dam were reported as the thalweg elevation of each 

cross section upstream from the dam. The stationing of each 

cross section was a straight-line distance up the middle of the 

channel. A plot of the thalweg location on each cross section 

shows an increase in sinuosity from 1960 to 1993 (fig. 18). 

Therefore, figure 17 is not a longitudinal profile of the channel 

over time because the stationing was not along the thalweg, 

but is rather a change in thalweg elevation at cross-sectional 

locations. Because of the reduced slope associated with the 

increased length of the thalweg, the profile in figure 17 would 

show a decrease in elevation over time if it were a longitudinal profile. The increase in sinuosity may have resulted in the 

reduction in channel gradient over time. As channel gradient 

decreases, sinuosity increases (Schumm, 1977). Many of the 

increases in sinuosity were observed in flumes or controlled 

experiments (Schumm and Khan, 1972). The same changes 

were observed at the scale of Big Sweat Dam. 

Hillslope-Erosion Plots

All 65 pins in Coyote C. Arroyo were located and measured in 1993, but the tops of the pins were surveyed only 

once, in 1962. Surveys of the tops of the pins in 1961 showed 

elevation differences as large as 2.8 cm, averaging 0.1 cm with 

a standard deviation of ± 0.7 cm (U.S. Geological Survey, 

Table 9. Weighted slopes of channel upstream from Big Sweat Dam and Little Sweat Dam near 

Santa Fe, New Mexico.

[--, no data]

(A) Big Sweat Dam

Weighted slopes, in meters per meter

Reach upstream 

from dam, in meters 

(figure 1)

1960 

(original) 1964 1968 1974 1993

0 to 5.3 0.069 0.043 0.038 -- 0.027

0 to 9.1 0.062 0.044 0.041 -- 0.044

0 to 18.3 0.051 0.039 0.036 0.037 0.035

0 to 25.9 0.048 0.035 0.034 0.036 0.036

0 to 33.5 0.042 0.045 0.033 0.033 0.034

33.5 to 67.0 0.045 0.044 0.045 -- 0.045

67.0 to 91.4 -- 0.077 0.042 -- 0.044

67 to 100.6 0.052 0.059 0.053 --

(B) Little Sweat Dam

Weighted slopes, in meters per meter

Reach upstream 

from dam, 

in meters 

(figure 1)

1960 

(original) 1962 1964 1993

0 to 7.6 0.058 0.049 0.028 0.028

0 to 11.0 0.066 0.055 0.029 0.027

11.0 to 22.9 0.047 0.024 0.028 0.034

11.0 to 61.0 -- -- -- 0.093

Deposition Behind Dams and Base-Level Experiments 41
unpublished data). Although this difference in pin elevations 

for 1 year is minimal, the changes in pin elevations after 

30 years may be substantial if the direction of change in nail 

elevations is consistent over time.

Without level surveys to periodically check the elevations 

of short pins, factors such as soil heave and wetting and drying 

of the soil may result in erroneous readings. Therefore, the 

results presented in this report should be viewed with caution. Average deposition for the three erosion-pin lines ranged 

from 1.45 to 2.56 cm, and average erosion ranged from 2.64 

to 4.54 cm (table 10). The average change in ground surface 

showed erosion for all three lines (table 10). 

In 1993, 25 of the 61 pins were located, surveyed, and 

measured in Slopewash Tributary (fig. 19). Surveys of the 

top of the pins in 1993 indicated that most pins had changed 

in elevation and, therefore, that soil heave may have moved 

the pins. The maximum increase in pin-head elevation from 

soil heave from 1959 to 1993 was 1.31 cm, and the maximum 

decrease in elevation was 0.61 cm. The average change in the 

tops of all pin heads was a decrease in elevation of 0.02 cm. 

Erosion is measured from the bottom of the pin head to the 

top of the washer, and differences in pin-head elevation over 

time alter the erosion measurement. To correct for changes in 

pin-head elevation, the difference in elevation from the 1959 

survey to the 1993 survey was either added to or subtracted 

from the measured erosion, depending on whether the pinhead elevation had increased or decreased over time. Deposition is the depth of sediment above the washer, and the washer 

was assumed to be unaffected by changes in the top of the pin.

Measurements at the Slopewash Tributary erosion plot 

indicate that average erosion at the 25 pins was 2.64 cm. The 

spacing of the pins was 1.524 m, and the total area was 

2.322 m2 for each square in the grid. Only 25 pins were 

recovered, resulting in a total area of about 58 m2 for the erosion measurements. The total volume of eroded soil for the 

entire grid was estimated by averaging the change in ground 

surface for all pins and multiplying by 58 m2. The total volume of eroded material from 1959 to 1993 was 0.377 m3

 or 

0.011 m3/yr. By using a dry density of 1,603 kg/m3, the total Figure 18. Planform diagram of 1960 and 1993 thalweg 

locations upstream from Big Sweat Dam. See photographs in figure 16.

Table 10. Summary of erosion-pin measurements at hillslope-erosion plots at Coyote C. Arroyo and 

Slopewash Tributary.

[cm/yr, centimeters per year]

Site Original 

date

Average 

erosion 

(cm)

Average 

deposition 

(cm)

Average change 

in land surface 

(cm)

Average change 

in surface erosion

(cm/yr)

Coyote C. Arroyo, line BA 1961–93 -4.54 1.45 -3.09 -0.096

Coyote C. Arroyo, line BC 1961–93 -4.52 2.13 -2.39 -0.075

Coyote C. Arroyo, line ED 1961–93 -4.43 2.56 -1.87 -0.058

Slopewash Tributary, plot A 1959–93 -2.64 1.99 -0.65 -0.019

42 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico

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Figure 19. Hillside containing pin and washer lines in an erosion plot on Slopewash Tributary. 

Location of tributary shown in figure 1.

Deposition Behind Dams and Base-Level Experiments 43

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in the watershed; the 1993 maps (1:24,000 scale) show 52 

houses. The number of houses may now (2001) be greater 

because of housing construction observed during the 1993 

and 1997 resurveys.

The population of Santa Fe County in 1950 was 38,153 

(U.S. Department of Commerce, 1952) and in 1990 was 

98,928 (U.S. Department of Commerce, 1990), a 159-percent 

increase. In 1950, the population of Santa Fe was 27,998 

(U.S. Department of Commerce, 1952) and in 1990 was 

55,859 (U.S. Department of Commerce, 1990), nearly a 

100-percent increase.

Road changes from 1952 to 1987 in the Arroyo de los 

Frijoles watershed, determined from aerial photographs 

(1:19,800 scale) taken in 1952–53 and aerial photographs 

(1:24,000 scale) taken in 1987 indicate an increase in total 

road length (fig. 20). Total road length in the watershed in 

1952 was 11,980 m and in 1987 was 27,790 m, a 132-percent 

increase. With an increase in population, an increase in roads 

is expected. On the basis of field work in the area from 1993 

to 1998, most roads appear to have been built for access to 

housing subdivisions.

Road crossings are affecting degradation and aggradation 

of the main channel Arroyo de los Frijoles (fig. 21). The 

change in channel elevation over the resurvey period clearly 

mass of sediment eroded was about 604 kg or 17.8 kg/yr. This 

value divided by the 58-m2 area of the erosion plot results in 

an annual sediment yield of about 307 metric tonnes/km2/yr at 

the Slopewash Tributary plot.

The average values of surface erosion reported here are 

within those of surface erosion and denudation rates reported 

for the Southwest, which range from 0.005 to 7.3 mm/yr 

(table 11). The erosion rates from this study are generally 

higher than the denudation rates reported at a geologic time 

scale (greater than 1 million years) (table 11) and may be due 

to differences in measurements over different time scales. On 

a geologic time scale, periods of erosion may be interrupted 

by periods of stability. A high surface-erosion rate (7.3 mm) 

(table 11) followed the 1977 La Mesa fire in the Jemez Mountains, New Mexico (fig. 1) (White and Wells, 1979).

Changes in Land Use

The Main Project reach in Arroyo de los Frijoles (fig. 1) 

is only 6.5 km from the downtown plaza in Santa Fe. Because 

of its proximity to Santa Fe, the study area has become 

increasingly residential since the Leopold and others’ (1966) 

study. The 1952 and 1953 USGS topographic maps (1:24,000 

scale) for the Arroyo de los Frijoles watershed show one house 

Table 11. Surface-erosion and denudation rates reported from studies conducted in the Southwest.

[mm/yr, millimeters per year; Ma, million years]

Location Time period 

analyzed

Erosion/

denudation rate 

(mm/yr)

Geology Method of analysis Reference

Jemez Mountains, New Mexico 1.14 Ma 0.005 to 0.011 Rhyolitic volcanic rocks Cosmogenic 

nuclides

Albrecht and 

others, 1993

Jemez Mountains, New Mexico 10/1977 to 11/1978 0.8 to 7.3 Rhyolitic volcanic rocks Erosion pins White and 

Wells, 1979

Western Espa–ola Basin, 

New Mexico

1.1 Ma 0.1 Weakly lithified sandstone Hypsometric Dethier and 

others, 1988

Western Espa–ola Basin, 

New Mexico

1.1 Ma 0.07 Indurated tuff/boulder 

gravel

Hypsometric Dethier and 

others, 1988

Western Espa–ola Basin, 

New Mexico

1.1 Ma 0.04 Indurated tuff/basalt Hypsometric Dethier and 

others, 1988

Red River Basin, Texas 3 Ma 0.47 Poorly consolidated shale, 

siltstone, and sandstone

Hypsometric Gustavson and 

others, 1981

Red River Basin, Texas 10/1978 to 9/1979 0.13 to 1.27 Poorly consolidated shale, 

siltstone, and sandstone

Suspended-sediment analysisGustavson and 

others, 1981

Four reservoirs in the Rolling 

Plains area, Texas

9 to 33 years 0.61 to 2.97 Poorly consolidated shale, 

siltstone, and sandstone

Reservoir sedimentation ratesGustavson and 

others, 1981

Rio Puerco Basin, New Mexico 10,000 years 0.1 Sandstone Cosmogenic 

nuclides

Clapp and 

others, 1997

Arroyo de los Frijoles watershed, 

Santa Fe, New Mexico

1961–93 0.19 to 0.96 Unconsolidated gravel, 

sand, and silt 

Erosion pins Current study

44 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
was largest where human effects are noticeable on the main 

channel Arroyo de los Frijoles (fig. 21). The effect of road 

crossings can be observed in the channel cross-sectional 

resurveys. The greatest degradation of the main channel 

Arroyo de los Frijoles, 1.53 m, and the greatest aggradation, 

0.38 m, are downstream and upstream, respectively, from a 

culvert in a dirt road (fig. 21). Five of the resurveyed cross 

sections were located downstream from this culvert (fig. 21). 

Field inspection of eight of the nine roads crossing the main 

channel Arroyo de los Frijoles indicated that four of the roads 

had a noticeable effect of either degradation or aggradation on 

the channel.

Figure 20. Roads in Arroyo de los Frijoles (A) in 1952–53 and (B) 

in 1987.

Summary

Detailed documentation of geomorphic changes in the 

landscape of more than a few years is rarely possible. The 

Vigil Network was established for such a purpose. In the 

1950’s and 1960’s, channel cross sections, sediment deposition behind dams, and hillslope-erosion plots in several small 

watersheds near Santa Fe, New Mexico, were monumented 

using concepts established in the Vigil Network to measure 

erosion and deposition. These geomorphic features were resurveyed in the 1990’s and provided the opportunity to assess 

Summary 45

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Figure 21. Road crossings over the main channel Arroyo de los Frijoles. (A) Buckman Road 6,662 meters downstream from the Slopewash Tributary watershed divide. (B) Unnamed road crossing with culvert 2,700 meters 

downstream from Slopewash Tributary. This crossing contained the cross section with highest aggradation 

upstream and downstream from the culvert.

46 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
more than 30 years of geomorphic change. In addition to the 

resurveys in the 1990’s, data are presented that were collected 

in the original study on channel scour but never published.

In 1993 and 1997, 51 of the original 79 cross sections 

were located and resurveyed, from which 32 cross sections 

were used to measure changes in cross-sectional area and 

19 cross sections were used to measure changes in thalweg 

elevation for the cross sections. The cross sections were 

originally monumented with steel bars. Elevation of the steel 

bars had not changed much over 30 years, averaging 0.8 cm 

for the 41 cross sections, within the normal surveying error of 

1.5 cm. A comprehensive study of Arroyo de los Frijoles in 

1966 concluded that the main channel Arroyo de los Frijoles 

was aggrading. Results from mid-1990’s resurveys of many 

of the same locations show that this trend did not continue. 

The average change in cross-sectional area for 32 resurveyed 

cross sections was erosion of 0.27 m2 or a 4-percent increase 

in cross-sectional area. The average net change in thalweg 

elevation for 51 resurveyed cross sections was degradation of 

0.04 m. Aggradation and degradation of the channel appear 

to vary through the watershed where several adjoining cross 

sections have the same trend in net thalweg elevation changes 

over time. Infiltration in the channel bed allows sites of deposition, and sites of heavy localized rainfall and tributary runoff 

may cause local scour. A 1978 study that used data from flume 

studies and field data from Arroyo de los Frijoles concluded 

that scour occurs locally at all flows and may be due to bedform migration of antidunes. 

Unpublished data (1964–68) for the scour chains showed 

that 371 chains had an average scour of 0.14 ± 0.14 m. About 

50 percent of the scour measurements were less than 0.10 m, 

and 10 percent were greater than 0.32 m. Fill measured at 372 

chains shows an average of 0.13 ± 0.11 m. Forty-seven percent 

of the fill was less than 0.10 m, and 11 percent was greater 

than 0.25 m. Scour, found in the original study (1958–64) to 

be proportional to the square root of discharge, was confirmed 

with the addition of the 1964–68 unpublished data. In 1993, 

33 of the original scour chains were located in 20 cross sections in the Arroyo de los Frijoles watershed. In the 25–29 

years since the scour chains were last read, scour ranged from 

0 to 0.52 m and averaged 0.24 ± 0.13 m. Deposition atop the 

scour chains ranged from 0.08 to 0.54 m and averaged 0.29 ± 

0.12 m. Observed changes in scour and fill have no consistent 

trend related to distance from the watershed divide. 

Arroyo de los Frijoles is 6.5 km from Santa Fe, and an 

increase in housing and population has led to an increase in 

roads between 1952–53 and 1987. Channel degradation is 

more noticeable at road crossings. The greatest degradation 

of the main channel Arroyo de los Frijoles, 1.53 m, and the 

greatest aggradation, 0.38 m, occur downstream and upstream, 

respectively, from a culvert in a dirt road. 

Average annual rainfall intensities were high in the 1853–

80 period that immediately preceded late 19th century arroyo 

incision and another period of high-intensity rainfall beginning 

in 1967. On the basis of a previous method used to interpret 

average annual rainfall intensity, rainfall since 1967 may 

indicate that climatic factors are again favorable for arroyo 

incision in this part of New Mexico. However, data from the 

channel surveys for this study do not support evidence for a 

renewed cycle of erosion.

For a 1930’s Civilian Conservation Corps-constructed 

earthen dam on Coyote C. Arroyo, sediment yield measured 

from 1966 to 1993 was 139 metric tonnes/km2/yr. Sediment 

yields have decreased over time from a decrease in the trap 

efficiency of the reservoir during the measurement period 

and(or) from a decrease in sediment delivery due to upstream 

channel storage. The effects of base-level rise on the channel 

profile behind two small dams, Big Sweat and Little Sweat, 

built in 1960, were documented through resurveys in 1993. 

The resurveys showed that deposition extended 20 and 9.3 m 

upstream, respectively, and that the final sediment gradient is 

nearly the same as the unaffected channel upstream. Big Sweat 

Dam showed fluctuations in channel gradient within 5.3 m of 

the dam, which may be due to local scour following complete 

filling of the dam, scour due to increased sinuosity, or differences in surveying stations over time. The sinuosity of the 

channel has increased over time, presumably from a reduction 

in slope. Channel gradients 0 to 11.0 m upstream from Little 

Sweat Dam have remained constant at about 0.028 from 1964 

to 1993. 

Hillslope erosion was measured in the original study at a 

site in the Coyote C. Arroyo watershed and a site in Slopewash 

Tributary: three lines with a total of 65 erosion pins in Coyote 

C. Arroyo and a total of 61 erosion pins in Slopewash Tributary. All 65 erosion pins in Coyote C. Arroyo were located and 

measured in 1993. Average deposition ranged from 1.45 to 

2.56 cm. Also in 1993, 25 of the 61 pins at Slopewash Tributary were located, surveyed, and measured. Most of the pins 

had changed in elevation. The maximum increase in pin-head 

elevation from soil heave was 1.31 cm, and the maximum 

decrease in elevation was 0.61 cm. Average erosion was 

2.64 cm, and average deposition was 1.99 cm. The sediment 

yield from this plot was 307 metric tonnes/km2/yr.

Acknowledgments

We would like to thank U.S. Geological Survey New 

Mexico District personnel for their help in putting this report 

together. We especially want to thank Phil Bowman and 

Harriet Allen for their editorial expertise and continued 

patience in helping to get this manuscript published. A variety 

of people helped in the surveying and data collection, including Scott Aby; Janelle Loving; Peter Sparks, who assisted in 

the original fieldwork; Jeff Mann; and Scott Englert.

For their review, comments, and suggestions, we thank 

Jim O’Connor and Anne Marie Matherne.

Acknowledgments 47
Foley, M.G., 1978, Scour and fill in steep, sand-bed ephemeral 

streams: Geological Society of America Bulletin, v. 89, 

p. 559–570.

Gellis, A.C., 1998, Characterization and evaluation of channel 

and hillslope erosion on the Zuni Indian Reservation, New 

Mexico, 1992–95: U.S. Geological Survey Water-Resources 

Investigations Report 97-4281, 51 p.

Gellis, A.C., Hereford, R., Schumm, S.A., and Hayes, B.R., 

1991, Channel evolution and hydrologic variations in the 

Colorado River Basin—Factors influencing sediment and 

salt loads: Journal of Hydrology, v. 124, p. 317–344.

Gustavson, T.C., Finley, R.J., and Baumgardner, R.W., Jr., 

1981, Retreat of the Caprock Escarpment and denudation 

of the Rolling Plains in the Texas Panhandle: Bulletin of 

the Association of Engineering Geologists, v. 18, no. 4, 

p. 413–422.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: Amsterdam, Elsevier Science, Studies in 

Environmental Science 49, 529 p.

Kachigan, S.K., 1986, Statistical analysis: New York, Radius 

Press, 589 p.

Kissam, P., 1978, Surveying for civil engineers: McGraw-Hill, 

799 p.

Leopold, L.B., 1951, Rainfall frequency, an aspect of climatic 

variation: Transactions of the American Geophysical Union, 

v. 32, no. 3, p. 347–357.

Leopold, L.B., 1962, The Vigil Network: Bulletin of the International Association for Hydrological Sciences, v. 7, no. 2, 

p. 5–9.

Leopold, L.B., 1976, Reversal of erosion cycle and climate 

change: Quaternary Research, v. 6, p. 557–562.

Leopold, L.B., and Bull, W.B., 1979, Base level, aggradation, 

and grade: Proceedings of the American Philosophical Society, v. 123, p. 168–202. 

Leopold, L.B., Emmett, W.W., and Myrick, R.M., 1966, Channel and hillslope processes in a semiarid area, New Mexico: 

U.S. Geological Survey Professional Paper 352-G, 243 p.

Love, D.W., 1997, Implications for models of arroyo entrenchment: Archaeological Society of New Mexico, v. 23, 

p. 63–84.

Miller, J.P., and Leopold, L.B., 1961, Erosion and sediment 

transport in Arroyo de Frijoles, New Mexico: Unpublished 

draft report, May 1961, 23 p.

Miller, J.P., Montgomery, A., and Sutherland, P.K., 1963, 

Geology of part of the Southern Sangre de Cristo Mountains, New Mexico: Socorro, New Mexico Institute of Mining and Technology Memoir 11, 106 p.

References

Albrecht, A., Herzog, G.F., Klein, J., Dezfouly-Arjomandy, 

B., and Goff, F., 1993, Quaternary erosion and cosmicray-exposure history derived from 10Be and 26Al produced 

in situ—An example from Pajarito Plateau, Valles caldera 

region: Geology, v. 21, p. 551–554.

Balling, R.C., and Wells, S.G., 1990, Historical rainfall patterns and arroyo activity within the Zuni River drainage 

basin, New Mexico: Annals of the American Geographers, 

v. 80, p. 603–617. 

Brown, C.B., 1945, Rates of sediment production in Southwestern United States: U.S. Department of Agriculture, Soil 

Conservation Service, SCS-TP-58, 40 p.

Bryan, K., 1928a, Change in plant association by change in 

ground-water level: Ecology, v. 9, p. 474–478. 

Bryan, K., 1928b, Historic evidence of changes in the channel of the Rio Puerco, a tributary of the Rio Grande, New 

Mexico: Journal of Geology, v. 36, p. 265–282. 

Bull, W.B., 1997, Discontinuous ephemeral streams: Geomorphology, v. 19, p. 227–276.

Clapp, E.M., Bierman, P.R., and Caffee, M., 1997, Rates of 

erosion determined using in situ produced cosmogenic 

isotopes in a small arroyo basin, northwestern New Mexico: 

Geological Society of America Abstracts with Programs, 

1997 Annual Meeting, Salt Lake City, p. A-371–A-372.

Cooke, R.U., 1974, Arroyos and environmental change in the 

American Southwest: Oxford, Clarendon Press, 213 p.

Cooke, R.U., and Reeves, R.W., 1976, Arroyos and environmental change in the American Southwest: Oxford, Clarendon Press, Oxford Research Studies in Geography.

Dethier, D.P., Harrington, C.D., and Aldrich, M.J., 1988, Late 

Cenozoic rates of erosion in the western Española Basin, 

New Mexico—Evidence from geologic dating of erosion 

surfaces: Geological Society of America Bulletin, v. 100, 

p. 928–937.

Elliott, J.G., Gellis, A.C., and Aby, S.B., 1999, Evolution of 

arroyos—Incised channels of the Southwestern United 

States, in Thorne, C., ed., Incised channels, p. 153–185.

Emmett, W.W., 1965, The Vigil Network—Methods of measurement and a sampling of data collected, in Symposium 

of Budapest, International Association for Hydrological 

Sciences Publication no. 66, p. 89–106.

Emmett, W.W., and Hadley, R.F., 1968, The Vigil Network–

Preservation and access of data: U.S. Geological Survey 

Circular 460-C, 21 p.

48 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Osterkamp, W.R., Emmett, W.W., and Leopold, L.B., 1991, 

The Vigil Network—A means of observing landscape 

change in drainage basins: Hydrological Sciences Journal, 

v. 36, no. 4, p. 331–344.

Patton, P.C., and Schumm, S.A., 1975, Gully erosion, northwestern Colorado—A threshold phenomenon: Geology, 

v. 3, p. 88–90.

Schumm, S.A., 1977, The fluvial system: John Wiley and 

Sons, 338 p.

Schumm, S.A., and Hadley, R.F., 1957, Arroyos and the semiarid cycle of erosion: American Journal of Science, v. 25, 

p. 161–174.

Schumm, S.A., Harvey, M.D., and Watson, C.C., 1984, Incised 

channels: Littleton, Colo., Littleton Press, 200 p.

Schumm, S.A., and Khan, H.R., 1972, Experimental study of 

channel patterns: Geological Society of American Bulletin, 

v. 83, p. 1755–1770.

Seginer, I., 1966, Gully development and sediment yield: Journal of Hydrology, v. 4, p. 236–253.

State of New Mexico, 1956, Climatological summary, New 

Mexico, precipitation 1849–1954: New Mexico State Engineer Office Technical Report 6, p. 334–335.

Swan, A.R.H., and Sandilands, M., 1995, Introduction to 

geological data analysis: Blackwell Science Ltd., Oxford, 

England, 446 p.

Thornwaite, C.W., Sharpe, C.F.S., and Dosch, E.F., 1942, 

Climate and accelerated erosion in the arid and semiarid 

southwest, with special reference to the Polacca Wash drainage basin, Arizona: U.S. Department of Agriculture Technical Bulletin 808, 134 p.

U.S. Department of Commerce, 1952, Census of the population—1950: U.S. Department of Commerce, v. II, Characteristics of the population, New Mexico, p. 31–6.

U.S. Department of Commerce, 1990, 1990—Census of the 

population: U.S. Department of Commerce, General population characteristics, New Mexico, p. 2.

Vanoni, V.A., 1977, Sedimentation engineering: American 

Society of Engineers Manuals and Reports on Engineering 

Practice, no. 54, 745 p.

White, W.D., and Wells, S.G., 1979, Forest-fire devegetation 

and drainage basin adjustments in mountainous terrain, in

Rhodes, D.D., and Williams, G.P., eds., Adjustments of the 

fluvial system: Proceedings of the Tenth Annual Geomorphology Symposia Series, Binghamton, N.Y., p. 199–223.

References 49

Appendix 1

Appendix 1 51
Appendix 1. Summary of difference in elevations in closing the 1993 and 1997 resurveys to 

the original surveys.—Continued

[cm, centimeter; --, difference in elevation could not be determined or no remarks]

Cross-section 

label 

(locations in 

figure 1B)

Cross-section name

Difference 

in elevation 

(cm)

Remarks

1 SWT-CS-1 Left-bank pin missing

2 SWT-CS-2 3 --

3 SWT-CS-3 0 --

4 LW-Chain 4 0 --

5 NFA-Upper Right-bank elevation not 

shown in original survey

6 NFA-Lower 2 --

7 Chain Section 15 1 --

8 LW-16 Right-bank pin was moved

9 LW-17 Right-bank elevation not 

shown in original survey

10 LW-18 1 --

11 LW-19 1 --

12 LTR 20-24 0 --

13 LTR 30-33 1 --

14 LW-35 1 --

15 LW-37 1 --

16 CS-40 Left-bank pin found on ground

17 CS-45 1 --

18 CH49 0 --

19 Frijoles Range 1 1 --

20 CH51 2 --

21 MPR 52-59 1 --

22 Frijoles Range 3 Right-bank pin missing

23 CH61 2 --

24 Frijoles Range 4 1 --

25 Frijoles Range 5 Right-bank pin missing

26 Frijoles Range 6 0 --

27 LW-64 1 --

28 Frijoles Range 7 1 --

29 LW-75 0 --

30 LW-76 1 --

31 LW-77 1 --

32 LW-79 1 --

33 LW-82 0 --

34 HMR-83 0 --

35 SPR 84-88 1 --

52 Channel and Hillslope Processes Revisited in the Arroyo de los Frijoles Watershed near Santa Fe, New Mexico
Appendix 1. Summary of difference in elevations in closing the 1993 and 1997 resurveys to 

the original surveys.—Continued

[cm, centimeter; --, difference in elevation could not be determined or no remarks]

Cross-section 

label 

(locations in 

figure 1B)

Cross-section name

Difference 

in elevation 

(cm)

Remarks

36 ACC-6 1 --

37 ACC-5 0 --

38 ACC-4 1 --

39 ACC-3 2 --

40 ACC-2 0 --

41 ACC-1 0 --

42 Gunshot Arroyo Station 468 3 --

43 Gunshot Arroyo Station 417 

top of headcut

0 --

44 Gunshot Arroyo Station 417 

bottom of headcut

0 --

45 Gunshot Arroyo Station 230 0 --

46 Gunshot Arroyo Station 25 0 --

47 Morning Walk Wash Upper 0 --

48 Morning Walk Wash Lower --

Appendix 1 53
Prepared by the New Mexico and New Hampshire-Vermont Water 

Science Center’s Publications Units—

For more information concerning the research in this report, contact:

Linda S. Weiss, Director

U.S. Geological Survey

New Mexico Water Science Center

5338 Montgomery Blvd., NE Suite 400

Albuquerque, NM 87109

or visit our Web site at:

http://nm.water.usgs.gov
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