Suspended-Sediment Loads and Yields in the North 

Santiam River Basin, Oregon, Water Years 1999–2004

Scientific Investigations Report 2007–5187

Prepared in cooperation with the City of Salem

U.S. Department of the Interior

U.S. Geological Survey
Cover: Photograph showing North Santiam River downstream of U.S. Geological 

Survey monitoring station, looking upstream from Blowout Road bridge. 

(Photograph taken by Heather Bragg, U.S. Geological Survey, October 21, 2003.)
Suspended-Sediment Loads and Yields in the 

North Santiam River Basin, Oregon, Water 

Years 1999–2004

By Heather M. Bragg, Steven Sobieszczyk, Mark A. Uhrich, and David R. Piatt

Prepared in cooperation with the City of Salem

Scientific Investigations Report 2007–5187

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

Bragg, H.M., Sobieszczyk, Steven., Uhrich, M.A., and Piatt, D.R., 2007, Suspended-sediment loads and yields in the 

North Santiam River basin, Oregon, water years 1999–2004: U.S. Geological Survey Scientific Investigations Report 

2007-5187, 26 p.
iii

Contents

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

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Methods and Data Analysis.........................................................................................................................3

Data Collection......................................................................................................................................3

Station Instrumentation ..............................................................................................................4

Changes to Turbidity Reporting .................................................................................................5

Suspended-Sediment Sampling................................................................................................5

Data Analysis.........................................................................................................................................7

Estimated Turbidity Values .........................................................................................................7

Regression Models for Estimating Suspended-Sediment Concentration 

from Turbidity ................................................................................................................11

Calculation of Suspended-Sediment Loads ..........................................................................15

Historic Streamflow............................................................................................................................15

Suspended-Sediment Loads......................................................................................................................20

Suspended-Sediment Yields ......................................................................................................................22

Summary and Conclusions.........................................................................................................................24

Future Studies...............................................................................................................................................25

Acknowledgments.......................................................................................................................................25

References Cited..........................................................................................................................................25
iv

Figures

Figure 1. Map showing location of study area and water-quality monitoring stations in 

the North Santiam River Basin, Oregon................................................... 2

Figure 2. Photograph showing a technician collecting a suspended-sediment sample 

using Equal-Width Increment method from the cableway at Breitenbush River 

above French Creek, near Detroit in the North Santiam River basin, Oregon, 

January 30, 2003 ........................................................................... 6

Figure 3. Graph showing recorded and estimated turbidity values at North Santiam 

River below Boulder Creek, near Detroit, North Santiam River Basin, Oregon, 

October 1, 2000 .............................................................................. 8

Figure 4. Photograph showing North Santiam River as seen from the cableway at 

North Santiam River below Boulder Creek, near Detroit, North Santiam River 

basin, Oregon, October 21, 2003 ......................................................... 9

Figure 5. Photograph showing first set (24 of 40 bottles total) of automatic pumped 

samples collected at North Santiam River below Boulder Creek, near Detroit, 

North Santiam River basin, Oregon, October 20-22, 2003 .............................. 10

Figure 6. Graph showing recorded and estimated turbidity values at North Santiam 

River below Boulder Creek, near Detroit, North Santiam River basin, Oregon, 

October 21, 2003 ........................................................................... 10

Figure 7. Photographs showing debris flow and a road failure (inset) in Blowout Creek 

subbasin in the North Santiam River basin, Oregon, December 17, 2001 ............ 12

Figure 8. Graph showing recorded and estimated turbidity values at Blowout Creek 

near Detroit, North Santiam River Basin, Oregon, December 17, 2001 ............... 13

Figure 9. Graphs showing regression models for estimating suspended-sediment 

concentration from instream turbidity for monitoring stations in the upper and 

lower basins in the North Santiam River basin, Oregon .............................. 14

Figure 10. Graphs showing annual mean streamflow at gaging stations in the North 

Santiam River basin, Oregon ............................................................... 16

Figure 11. Graphs showing peak streamflow at gaging stations in the North Santiam 

River basin, Oregon ........................................................................ 18

Figure 12. Graphs showing total annual and highest 3-day suspended-sediment load at 

monitoring stations in the North Santiam River basin, Oregon, water years 

1999–2004 .................................................................................... 21

Figure 13. Graphs showing suspended-sediment yield at monitoring stations in the 

North Santiam River basin, Oregon, water years 1999–2004 ........................... 23

Tables

Table 1. Streamflow-gaging and water-quality monitoring stations used to collect 

water-quality samples in the North Santiam River basin, Oregon..................... 3

Table 2. Schedule of water-quality and suspended-sediment sample collection in the 

North Santiam River basin, Oregon ...................................................... 4

Table 3. Regression models used for estimating suspended-sediment concentration 

from turbidity for monitoring stations in the North Santiam River basin, Oregon ... 13
Conversion Factors, Datums, and Abbreviations

Conversion Factors

Multiply By To obtain

acre-foot (acre-ft) 1233 cubic meter (m3

)

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

foot (ft) 0.3048 meter (m)

inch (in) 25.40 millimeter (mm)

mile (mi) 1.609 kilometer (km)

square mile (mi2

) 2.590 square kilometer (km2)

ton (short) 907.2 kilogram (kg)

ton per square mile (ton/mi2

) 0.3503 megagram per square kilometer (Mg/km2)

Datums

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

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

(NGVD 29). 

Altitude, as used in this report, refers to distance above the vertical datum.

Abbreviations

Abbreviation Meaning

FNU Formazin Nephelometric Unit

μm micrometer

mg/L milligram per liter

L liter

NTRU Nephelometric Turbidity Ratio Unit

NTU Nephelometric Turbidity Unit

EWI equal-width increment

LED light-emitting diode

Q streamflow

SSC suspended-sediment concentration

SSL suspended-sediment load

SSQ suspended-sediment discharge

SSY suspended-sediment yield

T turbidity

NWIS National Water Information System

USGS U.S. Geological Survey

YSI Yellow Springs Instruments

Water year is the 12-month period from October 1 through September 30 and is identified by the 

calendar year in which it ends. For example, the period October 1, 2003, through September 30, 

2004, is designated the 2004 water year.
vi

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Abstract

The North Santiam River provides drinking water to the 

residents and businesses of the city of Salem, Oregon, and 

many surrounding communities. Since 1998, water-quality 

data, including turbidity, were collected continuously at 

monitoring stations throughout the basin as part of the North 

Santiam River Basin Turbidity and Suspended Sediment 

Study. In addition, sediment samples have been collected 

over a range of turbidity and streamflow values. Regression 

models were developed between the instream turbidity and 

suspended-sediment concentration from the samples collected 

from each monitoring station. The models were then used to 

estimate the daily and annual suspended-sediment loads and 

yields. For water years 1999–2004, suspended-sediment loads 

and yields were estimated for each station. Annual suspendedsediment loads and yields were highest during water years 

1999 and 2000. A drought during water year 2001 resulted 

in the lowest suspended-sediment loads and yields for all 

monitoring stations. High-turbidity events that were unrelated 

or disproportional to increased streamflow occurred at several 

of the monitoring stations during the period of study. These 

events highlight the advantage of estimating suspendedsediment loads and yields from instream turbidity rather than 

from streamflow alone.

Introduction

The North Santiam River drains 778 mi2 of land from its 

headwaters in the Cascade Range to its confluence with the 

South Santiam River 12 mi south of Salem, Oregon (fig. 1). 

The altitude of the North Santiam River basin ranges from 

nearly 10,500 ft at the Mount Jefferson summit to 460 ft at the 

Willamette Valley floor. Like other Western Cascade rivers, 

the North Santiam River originates in the mountains as glacial 

runoff, snowmelt, and ground-water outflow. As the river runs 

its course, tributaries such as Boulder Creek, Rock Creek, and 

the Little North Santiam River flow into the mainstem.

The North Santiam River is regulated by two dams, both 

constructed in 1953 by the U.S. Army Corps of Engineers. 

Detroit Dam is the larger of the two and farther upstream, and 

has a drainage area of 437 mi2. Detroit Dam impounds Detroit 

Lake, providing flood control, pollution abatement, power 

generation, irrigation, and recreation. Water-surface altitudes 

on Detroit Lake vary by season and hydrologic conditions. 

The maximum pool altitude is 1,574 ft, full pool is 1,569 ft, 

and minimum conservation pool is 1,425 ft (U.S. Army Corps 

of Engineers, 1953). Storage capacity for Detroit Lake ranges 

from 455,000 acre-ft in the summer to 115,000 acre-ft in the 

winter. Big Cliff Dam is 3 mi downstream of Detroit Dam. 

The water-surface altitude of Big Cliff Lake ranges from 1,210 

to 1,180 ft as it regulates water releases from Detroit Dam.

The North Santiam River basin is prone to occasionally 

severe erosion resulting from steep slopes, a dense network 

of tributaries, and periods of intense rainfall. Notably, a storm 

front with unusually mild temperatures and humid air moved 

through the region during February 1996, resulting in 12 

–15 in. of rainfall in 4 days (Oregon Climate Service, 2005). 

The intense rainfall, coupled with rapidly melting snowpack, 

caused peak streamflows with recurrence intervals of 50–100 

years at many streamflow-gaging stations (Cooper, 2005). The 

flooding triggered Federal disaster declarations for all affected 

counties. Because the North Santiam River supplies drinking 

water for the city of Salem and neighboring communities, the 

turbid flood water caused numerous financial problems. The 

city of Salem’s Geren Island water-treatment facility closed 

for 8 days because of its inability to process the sediment-rich 

water. Costs for this closure and other storm-related problems 

totaled $1.1 million to the water utility (Hulse and others, 

2002).

The financial burden and environmental consequences of 

the 1996 flooding prompted the city of Salem to coordinate 

with State and Federal agencies, including the U.S. Geological 

Survey (USGS), to establish a water-quality monitoring 

network (fig. 1). The North Santiam River Turbidity and 

Suspended-Sediment Study was initiated in 1998 to investigate 

the sources and transport of sediment causing high turbidity. 

Suspended-Sediment Loads and Yields in the North 

Santiam River Basin, Oregon, Water Years 1999–2004

By Heather M. Bragg, Steven Sobieszczyk, Mark A. Uhrich, and David R. Piatt
or19-0143_Fig01

Stayton

DetroitLake

123°00' 122°45' 122°30' 122°15' 122°00' 121°45'

45°00'44°45'44°30'

Water-quality only monitoring site—See table 1

Boundary of subbasin

Rain gage

CASCADE RANGE Mount Jefferson

OlallieButte

ThreeFingeredJack

North Santiam River

Basin Extent

Mill City

Mehama

Detroit

MarionForks

River

Santiam

North

Little

North

Santiam

River

WILLAMETTE RIVER

VALLEY

Breitenbush River

Blowout Creek

North

Santiam

River

Rock

Creek

Bou dl er Creek

Big Cliff Dam

DetroitDam

North Santiam River study area

14178000

EXPLANATION

USGS streamflow-gaging station and No.—Water-quality  data were collected at these stations. See table 1

Base map modified from U.S. Geological Survey and other digital data sets (1:24,000). UTM projection, Zone 10,Horizontal datum: North American Datum of 1927 

4447281224500 1418300014182500

14181500

14179100

14179000

14180300

14182500

4447281224500

Boundary of North Santiam River basin

OREGON

Figure location

Salem

5 10 15 20 25 30 35 40

00

5 10 15 20 25

45 KILOMETERS

30 MILES

Figure 1. Location of study area and water-quality monitoring stations in the North Santiam River Basin, Oregon.

   Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
Uhrich and Bragg (2003) detailed the first 2 years of 

monitoring in the North Santiam River basin, from October 

1998 to September 2000. The report included streamflow and 

water-quality data for three monitoring stations in the upper 

basin (upstream of Detroit Dam) and established a technique 

for estimating suspended-sediment loads. Since September 

2000, five additional stations have been added to the 

monitoring network, including four stations in the lower basin 

(downstream of Detroit Dam). The ongoing water-quality 

monitoring and additional research are jointly funded by the 

city of Salem and the USGS.

Purpose and Scope

This report provides additional data to update and expand 

the analysis presented in the previous report (Uhrich and 

Bragg, 2003). The regression models relating turbidity and 

suspended-sediment concentration for the three existing upperbasin monitoring stations are refined by inclusion of additional 

data. Regression models for turbidity and suspended-sediment 

concentrations also have been established for four additional 

monitoring stations. Annual suspended-sediment loads and 

yields for water years 1999–2004, when both streamflow 

and turbidity data are available, are estimated for the seven 

monitoring stations. The streamflow data for several long-term 

gaging stations are analyzed to provide historical context for 

the high-flow and high-turbidity events. The highest turbidity 

events are then identified and discussed in relation to the 

annual suspended-sediment loads.

Methods and Data Analysis

Data Collection

At the time of the February 1996 flooding, the USGS 

managed four streamflow-gaging stations in the North 

Santiam River basin (North Santiam, Niagara, Little North, 

and Mehama; table 1). The gaging station at Breitenbush had 

been discontinued in 1987 but was reestablished in water 

year 1999 at the start of this study. Two additional monitoring 

stations (French and Blowout) were established in the upper 

basin, providing both streamflow and water-quality data for 

the study. Streamflow data were not collected at Geren Island. 

Standard USGS methods were applied to data collected at 

each gaging station to assure the quality of the streamflow 

record (U.S. Geological Survey, 2000–2005).

Table 1. Streamflow-gaging and water-quality monitoring stations in the North Santiam River basin, Oregon.

[Locations of streamflow-gaging stations are shown in figure 1. Abbreviations: mi2, square mile; N/A, not applicable]

USGS 

station No. Station name Station reference

Drainage 

basin area 

(mi2

)

Streamflow-gaging station

Period of 

record 

(water year)

Years of 

record

Upper basin stations

14178000 North Santiam River below 

Boulder Creek, near Detroit

North Santiam 216 1908–1909,

1929–2004

78

14179000 Breitenbush River above French 

Creek, near Detroit

Breitenbush 108 1933–1987,

1999–2004

61

14179100 French Creek near Detroit French 10 2002–2004 3

14180300 Blowout Creek near Detroit Blowout 26 1999–2004 6

Lower basin stations

14181500 North Santiam River at Niagara Niagara 453 1909–1920, 

1922, 

1939–2004

79

14182500 Little North Santiam River near 

Mehama

Little North 112 1932–2004 73

14183000 North Santiam River at Mehama Mehama 655 1905–07, 1911,

1921–2004

91

4447281224500 North Santiam River at Geren 

Island, near Stayton

Geren Island 688 N/A N/A

Methods and Data Analysis 
Table 2. Schedule of water-quality and suspended-sediment sample collection in the North Santiam River basin, Oregon.

[Station reference: Complete station names are shown in table 1. Abbreviations: EWI, equal-width increment. N/A, not applicable]

Station reference

Water-quality 

instrumentation 

installation dates

Samplecollection 

dates

Type and number of suspended-sediment samples

EWI Dip Total

Upper basin stations

North Santiam October 1998 October 1998–

September 2004

106 15 121

Breitenbush October 1998 October 1998–

September 2004

67 13 80

French June 2001 June 2001–

September 2004

24 10 34

Blowout October 1998 October 1998–

September 2004

106 12 118

Lower basin stations

Niagara April 2000 October 1998–

September 2004

52 12 64

Little North April 2000 October 1998–

September 2004

102 23 125

Mehama April 2000 October 1998–

September 2004

111 20 131

Geren Island March 2001 N/A N/A N/A N/A

All preliminary streamflow and water-quality data are 

available in near real time on the USGS North Santiam River 

study website (http://or.water.usgs.gov/santiam/). These data, 

as well as suspended-sediment analyses, are available through 

the USGS National Water Information System (NWIS) 

website (http://waterdata.usgs.gov/or/nwis).

The amount of precipitation within the North Santiam 

River basin varies locally on the basis of many factors, 

including geography and altitude. The amount of rain 

associated with each storm is given as the range of measured 

precipitation for several Oregon Climate Service (2005) rain 

gages in the basin. The Marion Forks gage is located the 

farthest east and at the highest altitude, the Detroit Dam gage 

is centrally located, and the Stayton gage is the farthest west 

and at the lowest altitude (fig. 1). Data from these three raingaging sites allow the magnitudes of the significant storms to 

be compared.

Station Instrumentation

Between 1998 and 2001, water-quality instruments were 

installed at eight stations, either in conjunction with existing 

streamflow-gaging stations or at new sites. In October 1998, 

three water-quality monitoring stations (North Santiam, 

Breitenbush, and Blowout) were established in the upper basin 

on the major tributaries of Detroit Lake. In April 2000, waterquality instruments were installed at existing streamflowgaging stations in the lower basin (Niagara, Little North, and 

Mehama). In June 2001, a water-quality and streamflowgaging station was established at French, and in March 2002, 

a water-quality-only monitoring site was established at Geren 

Island (table 2). Each of the eight water-quality monitoring 

stations included a Yellow Springs Instruments (YSI) 

multiparameter water-quality instrument. The instruments 

were outfitted with water temperature, specific conductance, 

pH, and turbidity sensors. Routine field checks, calibrations, 

   Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
and maintenance were performed on the YSI instruments. The 

results of these field checks and other USGS quality-assurance 

procedures sometimes indicated necessary corrections to the 

preliminary water-quality data (Wagner and others, 2006). 

All data parameters, including streamflow, were recorded 

semihourly (every 30 minutes) and uploaded six to eight times 

per day to the USGS database.

Changes to Turbidity Reporting

The variability of turbidity between sensors prompted 

the USGS to clarify the appropriate measurement unit 

corresponding to each type of turbidity sensor. Prior to 

October 1, 2004, most standard turbidity measurements in 

the United States, regardless of the sensor’s light source or 

detector geometry, were reported in Nephelometric Turbidity 

Units (NTU). The common unit of turbidity measurement 

in Europe was the Formazin Nephelometric Unit (FNU) as 

defined by method ISO 7027 (International Organization 

for Standardization, 1999). Beginning October 1, 2004, the 

USGS differentiated the turbidity measurements of different 

instruments on the basis of the wavelength of light used and 

the angle at which the light is emitted and detected (Anderson, 

2004). Turbidity sensors using a light-emitting diode (LED) 

with a wavelength of 840 ±60 nanometers, and the detector 

at an angle of 90 ±2.5 degrees to the incident light beam are 

now defined as measuring in Formazin Nephelometric Units. 

Sensors with tungsten lamps that detect scattered light at an 

angle of 90 ±30 degrees to the incident light beam measure 

in NTU (U.S. Environmental Protection Agency, 1999). Most 

turbidity units are not directly interchangeable; therefore, it 

is important to document which instrument and associated 

measurements are used when reporting or analyzing turbidity 

data.

The YSI Model 6026 turbidity sensor was consistently 

used to monitor instream turbidity during the North Santiam 

River study. This sensor measures turbidity with an LED at 90 

degrees. Prior to October 1, 2004, these data were reported in 

Nephelometric Turbidity Units. In accordance with the new 

USGS protocol, turbidity data from the same instrument are 

now reported in Formazin Nephelometric Units. All previously 

published turbidity data for the North Santiam study also were 

changed from Nephelometric Turbidity Units to Formazin 

Nephelometric Units in the USGS database. No conversion 

was needed between these data because the turbidity sensors 

and data analysis methods remained the same.

A Hach 2100N turbidimeter also consistently was 

used in the laboratory during the North Santiam study. 

Prior to October 1, 2004, these data also were reported 

in Nephelometric Turbidity Units. The Hach instrument 

measures turbidity with a tungsten light source and has 

multiple detectors. The angle between these multiple detectors 

determines the ratio used in calculating the final turbidity 

readings, reported in Nephelometric Turbidity Ratio Units 

(NTRU).

Suspended-Sediment Sampling

In addition to instream water-quality data, suspendedsediment samples were collected at each of the monitoring 

stations (excluding Geren Island) over a range of hydrologic 

conditions. Samples were collected by hand or by automatic 

sampler. All samples were analyzed at the USGS Cascades 

Volcano Observatory sediment laboratory in Vancouver, 

Washington. Standard processing included suspendedsediment concentrations (SSC), reported in milligrams per 

liter (mg/L), and the fraction of sample sediment smaller than 

sand-sized particles, reported in percent finer than 62 μm. If 

sufficient sediment was available from the sample, additional 

analysis was performed to determine complete grain-size 

distribution.

During the period of study, an average of nearly 100 

suspended-sediment samples was collected at each of the 

monitoring stations (table 2). The Equal Width Increment 

(EWI) method was used to collect most samples (fig. 2; 

Edwards and Glysson, 1999). Depth-integrated transits were 

made with the sampler at approximately 10 equal increments 

over the cross section. All water collected was composited 

into a single 3-liter (L) bottle for sample analysis. When 

streamflow conditions or safety concerns did not allow for 

EWI sampling, dip samples were collected. A weighted 1-L 

bottle was dipped at equal increments over the cross section, 

and the sample was composited into a single 3-L bottle.

In addition to the cross-sectional EWI and dip samples, 

single-point pumped samples were collected at three stations 

in the upper basin. A pumping sampler was installed at North 

Santiam in March 2003, and the samplers were installed 

at Breitenbush and Blowout in August 2004. The pumping 

samplers were positioned near the water-quality instruments 

and were programmed to collect samples on the basis of 

instream turbidity. When turbidity readings exceeded a 

programmed threshold value (20 FNU, for example), a 1-L 

sample was collected every 120 minutes. If turbidity surpassed 

a second and third threshold value (50 and 100 FNU, for 

example), samples were collected more frequently (every 60 

and 30 minutes, respectively). After turbidity peaked and the 

values decreased, samples were collected less frequently until 

turbidity decreased to the lowest threshold value. The turbidity 

threshold values were regularly adjusted according to the time 

of year and the expected magnitude of storms.

Methods and Data Analysis 
or19-0143_Fig02

Figure 2. A technician collecting a suspended-sediment sample using Equal-Width Increment method from the 

cableway at Breitenbush River above French Creek, near Detroit in the North Santiam River basin, Oregon, January 

30, 2003. (Streamflow = 4,960 cubic feet per second; turbidity = 130 Formazin Nephelometric Units).

 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
Data Analysis

One objective of collecting the continuous water-quality 

data and suspended-sediment samples was the estimation of 

suspended-sediment concentration (SSC) and calculation of 

the suspended-sediment loads (SSL) transported past each of 

the monitoring stations. Historically, streamflow data were 

used to estimate SSC. Uhrich and Bragg (2003) demonstrated 

that instream turbidity could be used as a better surrogate for 

SSC in the North Santiam River basin. Regression models for 

each monitoring station were developed to estimate SSC from 

instream turbidity. The regression equations were used with 

the continuous turbidity and streamflow records to calculate 

daily and annual SSL values.

Estimated Turbidity Values

Instream turbidity may be missing or deleted from 

the data record for many reasons. Erroneous values can be 

recorded as a result of environmental conditions, sensor 

malfunction, or power interruption. On several occasions 

throughout the period of water-quality record, turbidity 

exceeded the maximum range of a sensor, resulting in the 

flattening of the turbidity curve during peak values. For the 

purposes of calculating SSL at the North Santiam River basin 

monitoring stations, all missing and erroneous turbidity values 

were estimated.

Turbidity was estimated by direct interpolation for most 

of the missing and deleted values. The difference between 

the last recorded data value prior to the malfunction and 

the first recorded data value following the malfunction was 

equally distributed over the duration of the missing record. 

The turbidity values at adjacent monitoring stations were 

compared to these estimated values for the same period of 

record to discount the possibility of substantially higher or 

lower turbidity.

In several instances, the turbidity at a monitoring 

station exceeded the sensor maximum. Each YSI 6026 

turbidity sensor has a unique maximum value ranging from 

approximately 1,200 to 1,800 FNU. Turbidity data with more 

than two consecutive semi-hourly readings at the sensor 

maximum were assumed to be less than the actual instream 

value and were estimated. The estimation technique used for 

each of these events is discussed in the following sections.

North Santiam – October 1, 2000

On October 1, 2000, an event originating on the slopes 

of Mount Jefferson resulted in increased turbidity at North 

Santiam. The maximum value of the turbidity sensor was 

recorded for 21⁄2 hours (five semi-hourly readings). With no 

additional data available to estimate these erroneous values, a 

simple extrapolation was used (fig. 3).

Two linear extrapolations were applied to the turbidity 

data. The line formed by the two recorded turbidity readings 

prior to the maximum sensor value was extrapolated 

forward in time. The line formed by the two recorded 

turbidity readings following the maximum sensor value 

was extrapolated backward in time until these two lines 

crossed. The values along these two lines corresponding to 

the data logging times were used as the estimated turbidity 

readings. The maximum estimated turbidity value (nearest 

to the intersection of the two extrapolated lines) for this 

high-turbidity event was 3,520 FNU (fig. 3). On the basis of 

other short-duration, high-turbidity events at North Santiam, 

this approach provides a reasonable, but likely conservative, 

estimation of the peak turbidity.

Methods and Data Analysis 
or19-0143_Fig03

0

1,500

3,000

4,500

6,000

OCTOBER 1, 2000

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS

400

500

600

700

800

Instream turbidity

Extrapolation

Final estimated turbidity

Streamflow

3,520 FNU

STREAMFLOW, IN CUBIC FEET PER SECOND

09:00 12:00 15:00 18:00 21:00

Figure 3. Recorded and estimated turbidity values at North Santiam River below Boulder Creek, near Detroit, North 

Santiam River Basin, Oregon, October 1, 2000.

North Santiam – October 21, 2003

In October 2003, another event occurred in the upper 

North Santiam Basin that resulted in increased turbidity at 

North Santiam (fig. 4). The turbidity increased quickly and the 

sensor maximum was recorded for 41⁄2 hours (nine semi-hourly 

values). Unlike the previous example, additional data were 

available for estimating the peak turbidity during this event.

Forty-two samples were collected during October 20-22, 

2003 at North Santiam. The pumping sampler installed at 

the station was programmed to collect samples for turbidity 

greater than 20 FNU. Beginning October 20, 2003, at 23:00 

PDT, 40 pumped samples were collected during the next 

30 hours (fig. 5). Two EWI samples also were collected on 

October 21, 2003, following the turbidity peak. All samples 

were analyzed with the Hach 2100N turbidimeter in the 

laboratory. Each sample then had two associated turbidity 

values, measured in different units (one from the instream 

instrument, in Formazin Nephelometric Units, and one 

from the laboratory instrument, in Nephelometric Turbidity 

Ratio Units). A regression was developed between the two 

sets of turbidity data for 33 samples (the 9 pumped samples 

collected while the instream instrument recorded the sensor 

maximum were excluded). With the regression equation, the 

laboratory (NTRU) turbidity was used to estimate the instream 

(FNU) turbidity of the nine excluded pumped samples. These 

turbidity values were then used as the estimated instream 

values during the 41⁄2 hours that the turbidity at the monitoring 

station recorded the sensor maximum. With this method, the 

maximum estimated turbidity for this event was 5,550 FNU 

(fig. 6).

For comparison, the extrapolation method used for the 

October 2000 event at North Santiam also was attempted for 

the October 2003 event. The resulting maximum turbidity 

was 3,040 FNU (fig. 6). As expected, the extrapolation 

method underestimated peak turbidity values above the sensor 

maximum for this example. This conclusion is consistent with 

measured data during numerous high-turbidity events in the 

North Santiam River basin. Turbidity data typically have steep, 

increasing slopes on the rising arm of the data curve rather 

than the constant slopes used for the extrapolation method.

 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
Figure 4. North Santiam River as seen from the cableway at North Santiam River below Boulder Creek, near Detroit, 

North Santiam River basin, Oregon, October 21, 2003. (Streamflow = 395 cubic feet per second; turbidity = 563 Formazin 

Nephelometric Units).

or19-0143_Fig04

Methods and Data Analysis   
Figure 5. First set (24 of 40 bottles total) of automatic pumped samples collected at North Santiam River below Boulder Creek, near 

Detroit, North Santiam River basin, Oregon, October 20-22, 2003.

Figure 6. Recorded and estimated turbidity values at North Santiam River below Boulder Creek, near Detroit, North 

Santiam River basin, Oregon, October 21, 2003.

or19-0143_Fig05

0

2,000

4,000

6,000

OCTOBER 21, 2003

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS

200

300

400

500

STREAMFLOW, IN CUBIC FEET PER SECOND

3,040 FNU

5,550 FNU

03:00 06:00 09:00 12:00 15:00

Instream turbidity

Extrapolation

Final estimated turbidity

Streamflow

Pumped samples

10 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
Blowout – December 17, 2001

On December 17, 2001, debris flow and a road failure 

occurred in the Blowout Creek subbasin (fig. 7). At 09:30 PST, 

the instream turbidity at Blowout was 24 FNU. Thirty minutes 

later, the turbidity was 1,370 FNU, the maximum value for 

this sensor. The turbidity was at the sensor maximum for 21⁄2 

hours (5 semihourly values). With no additional data available 

to estimate the instream turbidity above the sensor maximum, 

a modified extrapolation was used.

The sediment that caused the high turbidity was entrained 

so quickly that the sensor reached the maximum value before 

a slope was defined on the rising arm of the turbidity curve. 

Rather than extrapolating two lines until they intersect, a 

single extrapolation line was used. The line formed by the 

two recorded turbidity readings following the maximum 

sensor value was extrapolated backward in time. The values 

along the line corresponding to the semi-hourly recorded data 

times were used as the estimated turbidity. The maximum 

estimated turbidity (the point corresponding to 10:30 PST) 

was 3,400 FNU (fig. 8). The rising arm of the turbidity 

curve was estimated with this maximum estimated turbidity 

and the turbidity reading immediately prior to the sensor 

reaching its maximum value. This extrapolation method likely 

underestimates the turbidity for such high-turbidity events yet 

provides a reasonable estimate.

Regression Models for Estimating SuspendedSediment Concentration from Turbidity

The water-quality data and suspended-sediment samples 

collected at each monitoring station provided the data needed 

to develop regression models between instream turbidity 

and SSC. A detailed description of the regression techniques 

was presented in the previous North Santiam Basin report by 

Uhrich and Bragg (2003). A summary of these techniques 

follows.

An instream turbidity value, in Formazin Nephelometric 

Units, associated with each suspended-sediment sample was 

produced by averaging two or three recorded values over 

the duration of the sample collection time. An SSC value, in 

milligrams per liter, was provided by the laboratory analysis 

of the sample. For all samples collected at a monitoring 

station, the paired turbidity and SSC data were compiled and 

transformed to base-10 logarithmic values. These log values 

were then used to calculate a linear least-squares regression 

model. The model was converted to the power equation form:

SSC turbidity = ×a ( )b

, (1)

where a and b were the coefficients obtained by the regression 

analysis. Transformation of the turbidity and SSC data to log 

values and back to original form introduced a bias into the 

regression model. The bias was corrected with a “smearing” 

estimator described by Helsel and Hirsch (1992). The bias 

correction factor was calculated as the mean of the residual 

errors from the regression. The final regression model, 

including the correction factor, had the form:

SSC turbidity turbidity = × × cf a ( ) = ×A ( ) b b

, (2)

where A was the product of the correction factor (cf) and 

the coefficient (a) determined by the regression analysis.

The final forms of the regression models for each 

monitoring station are shown in table 3. The regression models 

for the seven monitoring stations are plotted in figure 9. For 

each station, the solid line indicates the estimated SSC that 

is defined by sample turbidity values used in the regression 

models. The dashed portion of each line indicates the range 

of estimated SSC and instream turbidity values at which no 

suspended-sediment samples were collected.

The regression models for North Santiam, Breitenbush,

and Blowout differ from those used to calculate SSC for water 

years 1999 and 2000 in the previous report by Uhrich and 

Bragg (2003). Many additional samples were collected at these 

stations, including some with instream turbidity values greater 

than 100 FNU. Changes in the USGS rounding protocol 

for turbidity data also necessitated the exclusion of many 

samples with low turbidity values (less than 1 FNU) that had 

been included in the previous models. The removal of these 

samples from the analyses at North Santiam, Breitenbush, and 

Blowout resulted in slightly lower R2 values for the regression 

models at all three stations. However, the inclusion of more 

high-turbidity samples in the analyses improved the models 

for estimating SSC from high instream turbidity, when most 

sediment is transported.

Methods and Data Analysis 11
or19-0143_Fig07

A. Debris flow B. Road failure

Figure 7. Debris flow and a road failure (inset) in Blowout Creek subbasin in the North Santiam River basin, Oregon, December 17, 2001.

12 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
or19-0143_Fig08

0

1,500

3,000

4,500

6,000

DECEMBER 17, 2001

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS

400

600

800

1,200

1,000

STREAMFLOW, IN CUBIC FEET PER SECOND

3,400 FNU

06:00 09:00 12:00 15:00 18:00

Extrapolation

Final Estimated Turbidity

Streamflow

Instream Turbidity

Figure 8. Recorded and estimated turbidity values at Blowout Creek near Detroit, North Santiam River Basin, 

Oregon, December 17, 2001.

Table 3. Regression models used for estimating suspendedsediment concentration from turbidity for monitoring stations in 

the North Santiam River basin, Oregon.

[Station reference: Complete station names are shown in table 1. 

SSC, suspended-sediment concentration; T, turbidity]

Station reference Regression equation R 2

 value

North Santiam SSC = 1.75 × T 1.04 0.893

Breitenbush SSC = 1.80 × T 1.08 .915

French SSC = 1.25 × T 1.01 .824

Blowout SSC = 1.35 × T 1.18 .928

Niagara SSC = 1.49 × T 0.758 .760

Little North SSC = 1.78 × T 1.02 .915

Mehama SSC = 1.73 × T 0.916 .861

Methods and Data Analysis 13
or19-0143_Fig09

10

1

100

1,000

10,000

100,000

1 10 100 1,000 10,000

North Santiam Extrapolated

Breitenbush Extrapolated

French Extrapolated

Blowout Extrapolated

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS (FNU)

10

1

100

1,000

10,000

100,000

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER

1 10 100 1,000 10,000

Niagara Extrapolated

Little North Extrapolated

Mehama Extrapolated

A. Upper basin

B. Lower basin

Figure 9. Regression models for estimating suspended-sediment concentration from instream turbidity for monitoring 

stations in the upper and lower basins in the North Santiam River basin, Oregon.

14 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
Calculation of Suspended-Sediment Loads

Daily and annual suspended-sediment loads were 

calculated from the continuous turbidity and streamflow 

records. The regression model for each monitoring station 

was used to estimate suspended-sediment concentration from 

each semi-hourly turbidity value. The semi-hourly suspendedsediment discharge (SSQ) was calculated from the estimated 

SSC and the instantaneous streamflow (Q) using the following 

equation:

SSQ tons SSC mg/L ft /s 3 ( / min) ( ) ( ) 30 = × × Q c , (3)

where c = 0.0000562, converting the units to tons per 30 

minutes. The 48 semi-hourly SSQ values calculated per day 

were summed to estimate the daily SSL, in tons. The 365 (or 

366) daily SSL values per year were then summed to provide 

the annual SSL for each station for each water year.

Historic Streamflow

Streamflow data from several gaging stations in the 

North Santiam River basin were analyzed to provide historical 

context for the annual mean and maximum instantaneous 

streamflow for water years 1999–2004 (U.S. Geological 

Survey, 2000–2005). Five of the water-quality stations were 

installed at long-term USGS streamflow-gaging stations 

(North Santiam, Breitenbush, Niagara, Little North, and 

Mehama; fig. 1). The gaging stations at North Santiam and 

Breitenbush are located in the upper basin (upstream of Detroit 

Lake) where streamflow is not affected by operation of the 

two dams. Niagara and Mehama are both on the mainstem 

North Santiam River downstream of the dams. Mehama is 

located nearly 20 mi downstream of Big Cliff Dam with many 

tributaries (including that gaged at Little North) contributing to 

the streamflow. Niagara is located less than 1 mi downstream 

of Big Cliff Dam where streamflow is highly regulated and not 

responsive to natural flow conditions. Niagara therefore was 

not included in the historical streamflow analysis.

The streamflow extremes took place during the first 3 

years of the 6-year period of study. Annual mean streamflows 

were highest during water year 1999, when flows at North 

Santiam, Breitenbush, and Mehama were greater than the 

75th percentile (fig. 10). However, the storm producing the 

peak streamflows occurred in water year 2000. In November 

1999, peak flows were greater than the 75th percentile at North 

Santiam, Breitenbush, and Mehama for their respective periods 

of record and the peak flow at Little North was greater than the 

95th percentile (fig. 11). Streamflows were lowest during water 

year 2001, when the region experienced a severe drought. 

The 2001 annual mean streamflows for North Santiam, 

Breitenbush, Little North, and Mehama were less than the 5th

percentile (fig. 10). The peak flows for all four stations also 

were less than the 5th percentile (fig. 11).

Annual mean and peak streamflows during water years 

2002–04 were less extreme than those during water years 

1999–2001. Mean annual and peak streamflows generally fell 

between the 25th and 75th percentiles for all stations during 

water years 2002-04.

Methods and Data Analysis 15
or19-0143_Fig10a,b

800

1,200

1,600

2004

2003

2002

2001

2000

1999

Median

Median

2004

2003

2002

2001

2000

1999

A. North Santiam

B. Breitenbush

400

1,400

1,000

600

75th percentile

25th percentile

75th percentile

25th percentile

200

400

600

800

1,000

WATER YEAR

ANNUAL MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Figure 10. Annual mean streamflow at gaging stations in the North Santiam River basin, Oregon. Station reference is defined 

in table 1.

16  Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
or19-0143_Fig10c,d

400

200

600

800

1,200

2004

2003

2002

2001

2000

1999

Median

Median

2004

2003

2002

2001

2000

1999

C. Little North

D. Mehama

2,000

0

4,000

6,000

ANNUAL MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

1,000

WATER YEAR

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

75th percentile

25th percentile

75th percentile

25th percentile

1953

Detroit and Big Cliff

Dams constructed

Figure 10.—Continued.

Methods and Data Analysis 17
ORWSC19_0143_fig_11A_B

0

10.000

20,000

30,000

40,000

PEAK STREAMFLOW, IN CUBIC FEET PER SECOND

WATER YEAR

0

10.000

20,000

30,000

40,000

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

75th percentile

25th percentile

75th percentile

25th percentile

2001

2004

2003

2002

2000

Median

2001

2004

2003

2002 1999

2000

Median

1999

A. North Santiam

B. Breitenbush

Figure 11. Peak streamflow at gaging stations in the North Santiam River basin, Oregon. Station reference is defined in 

table 1.

18  Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
ORWSC19_0143_fig_11C_D

0

10,000

20,000

30,000

40,000

PEAK STREAMFLOW, IN CUBIC FEET PER SECOND

75th percentile

25th percentile

75th percentile

25th percentile

WATER YEAR

0

20.000

40,000

60,000

80,000

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Median

2001

2004

2003

2002

1999

2000

2001

2004

2003

2002

1999

2000

1953: Detroit and 

Big Cliff Dams 

constructed

Median

C. Little North

D. Mehama

Figure 11.—Continued.

Methods and Data Analysis 19
Suspended-Sediment Loads

The effects of the varied hydrologic conditions from year 

to year were reflected in the SSL estimates. On the basis of 

the streamflow analysis, annual SSL was highest during water 

years 1999 and 2000 and lowest during water year 2001 for 

most of the monitoring stations (fig. 12). In addition to the 

annual SSL, the highest consecutive 3-day SSL was calculated 

to demonstrate the effect of a single short-term event at each 

station for each water year.

SSL was calculated at the monitoring stations only when 

both turbidity and streamflow data were available. Therefore, 

SSL was not estimated for the lower-basin stations (Niagara, 

Little North, and Mehama) for water years 1999–2000 or for 

French for water years 1999–2001. Water-quality instruments 

had not yet been installed at these stations, and turbidity data 

were not available.

Water Year 1999

Total SSL was substantial during water year 1999. 

Blowout had its highest annual SSL and both North Santiam

and Breitenbush had their second highest SSL for the period of 

study. Annual mean streamflow data indicated that water year 

1999 was the highest annual streamflow year for water years 

1999–2004. The highest 3-day SSL occurred during December 

27–29, 1998, when the basin received 7–8 in. of rain (Oregon 

Climate Service, 2005). Peak streamflow during this storm 

was classified as a 2–5 year recurrence flood at several of the 

gaging stations (Cooper, 2005). The 14,100 tons of sediment 

transported past Blowout during the December storm were 

more than double the 3-day SSL at that station for any of the 

other water years (fig. 12).

Water Year 2000

SSL was highest during water year 2000 for the period 

of study at both North Santiam and Breitenbush. Although 

the annual streamflows were lower than in water year 1999, 

the maximum instantaneous flows were much higher at the 

three upper-basin gaging stations. Seven to 10 in. of rain 

fell in the basin during November 25-27, 1999, resulting in 

the largest precipitation-driven event for the period of study 

(Oregon Climate Service, 2005). The resulting 10–25-year 

recurrence interval flood produced the highest streamflow and 

SSL for the water year (fig. 12; Cooper, 2005). The 22,200 

tons at North Santiam was the highest 3-day SSL at the station 

for water years 1999–2004. The greatest SSL at any of the 

monitoring stations for the entire period of study occurred at 

Breitenbush during this storm. An estimated 69,800 tons of 

sediment was transported past the station in 3 days.

Water Year 2001

Water year 2001 was a severe drought year. The highest 

SSL and streamflow occurred at different times during the 

winter and spring in conjunction with storms producing less 

than 4 in. of rain over 3 days (Oregon Climate Service, 2005). 

Annual mean flows and the peak streamflows were less than 

the 5th percentile for the four gaging stations for which data 

was analyzed. The highest SSL recorded at Blowout was 

during December 22–24, 2000, and at Breitenbush during 

April 30–May 2, 2001. The highest SSL at North Santiam was 

not related to either of these storms. As discussed in section, 

“Data Analysis,” an event in the upper North Santiam River 

subbasin on October 1, 2000, caused extremely turbid water 

at the monitoring station. The resulting 1,700 tons of sediment 

was the highest 3-day SSL for any of the stations for the water 

year. SSL was first estimated at the lower-basin monitoring 

stations for water year 2001. The highest SSL at Niagara

occurred December 23–25, 2000 (following the highest SSL at 

Blowout). The highest SSL values at Little North and Mehama

were recorded during the storm on April 30–May 2, 2001. 

The annual SSL values for all six monitoring stations were the 

lowest for each during the 6 years of study (fig. 12).

Water Year 2002

A spring storm produced the highest SSL totals for water 

year 2002. The highest 3-day SSL for three of the upper-basin 

stations (North Santiam, Breitenbush, and French) occurred 

during April 13–15, 2002, when 2 to 3 in. of rain fell in 3 days 

(Oregon Climate Service, 2005). Little North and Mehama

also had their highest SSL during this storm. The annual SSL 

of 35,200 tons at Mehama was the highest for the period of 

study (fig. 12). The peak streamflows at the gaging stations 

were near average (between 25th and 75th percentile) for all 

stations during this storm. Blowout recorded increased SSL 

during the April storm, but its highest SSL occurred during 

December 17–19, 2001. As discussed in section, “Data 

Analysis,” debris flow and a road failure in the Blowout 

Creek subbasin produced increased turbidity and SSL at the 

station. The maximum SSL values at Niagara occurred during 

December 21–23, 2001, and April 14–16, 2002, in the days 

following high SSL values in the upper basin.

20 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
or19-0143_Fig12

Total annual

Highest 3-day

SuspendedSediment Load

Percent of total annual

SUSPENDED-SEDIMENT LOAD, IN TONS

North Santiam

Breitenbush

French

Blowout

Niagara

Little North

Mehama

North Santiam

Breitenbush

French

Blowout

Niagara

Little North

Mehama

0

10,000

20,000

30,000

40,000

0

10,000

20,000

30,000

40,000

0

10,000

20,000

30,000

40,000

15,400

40% 68% 68%

46% 23% 24% 4% 30% 13% 50% 55% 36%

85% 94% 81%

52% 6% 31% 22%

40% 63% 60% 25% 6% 44% 28% 29% 41% 52% 61% 9% 64% 42%

25,300

20,800

3,720

640 200

2,120 2,380

7,270

6,830 8,440

1,960 667

4,940

14,000

26,300

7,440

4,510

715 1,060

3,320

17,700

27,300

15,300 15,500

13,500

764

7,380

17,200

35,200

26,200

74,700

69,800

7,510

29% 41% 52% 61% 9% 64% 42%

A. WATER YEAR 1999 B. 2000

D. 2002

F. 2004

C. 2001

E. 2003

Figure 12. Total annual and highest 3-day suspended-sediment load at monitoring stations in the North Santiam River basin, 

Oregon, water years 1999–2004.

Suspended-Sediment Loads 21
Water Year 2003

During water year 2003, several storms produced 

increased SSL totals for the North Santiam monitoring 

stations. The highest SSL values for most of the upper-basin 

stations occurred January 30–February 1, 2003, during a 

storm that generated 5–7 in. of rain in 3 days (Oregon Climate 

Service, 2005). This storm also resulted in the highest 3-day 

SSL totals at Little North and Mehama (fig. 12). The peak 

streamflow analysis indicates that the storm was considered 

average for three of the four gaging stations. The JanuaryFebruary storm resulted in increased SSL at Blowout, but the 

highest SSL at the station occurred during March 21–23, 2003. 

Niagara had its highest SSL values following both the January 

and March storms.

Water Year 2004

Annual mean and maximum instantaneous streamflows 

for water year 2004 were below-average for most of the North 

Santiam River basin monitoring stations. As in October 2000 

(and discussed in section “Data Analysis”), the highest SSL at 

North Santiam resulted from an event originating high in the 

subbasin. For the other upper-basin stations, one of two storms 

produced the highest 3-day SSL. The first storm occurred 

December 13–15, 2003, with 4–5 in. of rain in 3 days (Oregon 

Climate Service, 2005). The highest 3-day SSL values at 

Breitenbush and Blowout were recorded during this storm. 

The next storm occurred during January 28–30, 2004, and 

generated 3–5 in. of rain in 3 days (Oregon Climate Service, 

2005). This storm produced the highest SSL at French. The 

three lower–basin stations also recorded their highest 3-day 

SSL in relation to the January storm.

Suspended-Sediment Yields

Suspended-sediment yields (SSY) were calculated by 

dividing the estimated annual suspended-sediment loads (SSL) 

by the area, in square miles, of each subbasin. Normalizing 

the annual SSL by the respective subbasin areas provides 

additional context for the events discussed in section, 

“Suspended-Sediment Loads.”

The peak storms of water years 1999 and 2000 

demonstrate the effect that a small subbasin, such as that 

upstream from Blowout (26 mi2), can have on sediment 

production in the North Santiam River basin. Although the 

highest SSL for water year 1999 was recorded at Breitenbush, 

the SSL at Blowout resulted in three times the sediment per 

unit area (fig. 13). The estimated 800 tons/mi2 was the highest 

SSY for any of the stations for any of the water years during 

the study. The Breitenbush River produced the highest SSY for 

water year 2000, with an annual SSL of 74,700 tons resulting 

in an SSY of 705 tons/mi2 (fig. 13). The highest SSY for water 

year 2002 was produced by the Blowout Creek subbasin. 

The road failure and debris flow upstream of the monitoring 

station resulted in relatively high SSY (520 tons/mi2) in a near 

average streamflow year (fig. 13). None of the monitoring 

stations in the North Santiam River basin recorded notably 

high SSY values during water years 2001, 2003, or 2004 

(fig. 13).

22 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
or19-0143_Fig13 SUSPENDED-SEDIMENT YIELD, IN TONS PER SQUARE MILE

North Santiam

Breitenbush

French

Blowout

Niagara

Little North

Mehama

North Santiam

Breitenbush

French

Blowout

Niagara

Little North

Mehama

0

400

200

600

800

1,000

0

400

200

600

800

1,000

0

400

200

600

800

1,000

A. WATER YEAR 1999 B. 2000

D. 2002

F. 2004

C. 2001

E. 2003

Figure 13. Suspended-sediment yield at monitoring stations in the North Santiam River basin, Oregon, water years 1999–2004.

Suspended-sediment Yields 23
Summary and Conclusions

Annual suspended-sediment loads (SSL) and suspendedsediment yields (SSY) were highest during the relatively high 

streamflow of water years 1999 and 2000. Three-day SSL 

and annual SSL totals were highest in the three upper-basin 

stations that were in operation during one of those years. 

Although water year 1999 was the higher annual streamflow 

year, water year 2000 was the higher sediment transport year. 

Comparisons among the lower-basin monitoring stations were 

less definitive because SSL totals were available for only four 

water years (2001–04) that had average to below-average 

streamflow.

North Santiam River below Boulder Creek, near Detroit

The highest SSL totals at North Santiam were not 

associated with the highest instream turbidity. SSL was 

highest at the North Santiam monitoring station during the 

November 1999 storm. The 3-day SSL was more than 22,000 

tons, greater than the annual SSL at the station for water years 

2000–04. This storm-related SSL also resulted in the highest 

percentage of total annual SSL (85 percent) at this station. For 

the remainder of the period of study, the subbasin upstream 

of North Santiam produced between 29 and 50 percent of its 

annual SSL during the respective highest 3-day SSL. In water 

years 2001 and 2004, the sediment responsible for the highest 

SSL events originated on the slopes of Mount Jefferson, likely 

from glacial events or slope failures. Because these very 

high turbidity events did not occur in association with high 

streamflow, the relative SSL totals were not as significant.

The total annual SSL calculated for water years 1999 and 

2000 were slightly lower than the SSL published for those 

years in a previous report from the study (Uhrich and Bragg, 

2003). The addition of more than 20 samples to the regression 

analysis resulted in a change to the model-estimated SSC 

from instream turbidity for North Santiam. Although the R2

value was slightly lower (0.89) than that of the previous model 

(0.91), the difference of the SSL estimates for both water years 

was less than 10 percent.

Breitenbush River above French Creek, near Detroit

SSL was highest at Breitenbush of all stations during the 

period of study. The 69,800 tons of sediment transported in 3 

days during the November 1999 storm represents more than 

twice the annual SSL totals at any of the monitoring stations 

for any of water years 1999–2004. The instream turbidity 

during this storm did not reach the sensor maximum but was 

higher and persisted longer than the turbidity at the other 

upper-basin stations. The sediment causing the high turbidity 

during this storm was believed to have originated in a small 

unnamed tributary of one main tributary of the Breitenbush 

River. Since this storm, the U.S. Forest Service has made 

efforts to reduce the amount of surface runoff in this area.

The annual SSL calculated for water years 1999 and 

2000 at Breitenbush was higher than the SSL published for 

those years in the previous report from this study (Uhrich and 

Bragg, 2003). The increase was greater during water year 

2000, when the annual SSL was nearly 50 percent greater 

than the previous estimate. The original regression analysis 

included many samples with instream turbidity less than 1 

Formazin Nephelometric Unit. More than 20 of these samples 

were excluded from the current analysis. Although many 

samples, including several high-turbidity samples, were added 

to the analysis, 10 fewer samples were used for the current 

model-estimated SSC from instream turbidity. The R2

 value 

of the current model (0.92) was slightly lower than that of the 

previously published model (0.95).

French Creek near Detroit

The total annual and highest 3-day SSL at French were 

nearly equal for water years 2002–04. The small subbasin (10 

mi2

) produced 765, 668, and 716 tons of sediment for water 

years 2002 through 2004, respectively. The highest 3-day SSL 

(400 tons) resulted from a small debris flow that entered the 

creek 0.5 mi upstream of the monitoring station during the 

storm on January 30–February 2, 2003.

Blowout Creek near Detroit

The Blowout Creek subbasin produced a significant SSL 

during storms in water years 1999–2000. The highest 3-day 

SSL was during the December 1998 storm. The turbidity 

during this event did not reach the sensor maximum (1,370 

FNU) but was greater than that of the other two upperbasin stations. A slope failure or encroachment by the many 

earthflows in the subbasin may have occurred during the 

storm, but the SSL could not be attributed to a specific area. 

This storm also produced the highest SSY for any of the 

stations during the period of study.

The sediment source related to the December 2001 storm 

at Blowout was easily identifiable. Less than 3 mi upstream of 

the monitoring station, debris flow and a road failure carved 

a swath through the forest and deposited nearly 5,000 tons 

of sediment into a tributary of Blowout Creek. As a result of 

either the size of the slope failure or its close proximity to 

the monitoring station, the turbidity far exceeded that of the 

December 1998 storm. However, the higher streamflow and 

longer duration of the 1998 storm produced the higher 3-day 

SSL at Blowout.

Like at Breitenbush, the total annual SSL calculated for 

water years 1999 and 2000 at Blowout were higher than the 

loads published in the previous report from this study (Uhrich 

and Bragg, 2003). The current SSL estimates for both water 

years were 35–40 percent greater than the previous estimates. 

Although several turbidity samples less than 1 Formazin 

Nephelometric Unit were excluded from the regression 

analysis, many more samples were collected at Blowout. 

Thirty more samples were included in the current analysis, 

including many with high turbidity.

24 Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
North Santiam River at Niagara

The highest SSL events in the upper North Santiam River 

basin had minimal effect on the annual SSL at Niagara. Only 

4–9 percent of the annual SSL was produced in any 3-day 

period during water years 2001–04. The monitoring station is 

located 3.5 miles downstream of Detroit Dam and 0.5 miles 

downstream of Big Cliff Dam. The two reservoirs function 

as traps for sediment transported in the upper basin, limiting 

sediment output downstream. Blowout Creek is the closest 

of the upper basin tributaries to Detroit Dam and therefore 

the most likely to transport sediment through the dam and 

downstream. In several instances, this effect could be noted 

when the highest SSL at Niagara closely followed the highest 

SSL events at Blowout.

Of the 64 suspended-sediment samples collected and 

used for the regression analysis at Niagara, 50 had instream 

turbidity less than 10 FNU. Any slight variability of SSC at 

low turbidity values can affect the regression model statistics. 

For Niagara, the R2

 value of the regression model was 0.76, 

the lowest of all monitoring stations.

Little North Santiam River near Mehama

The Little North Santiam River produced its highest SSL 

during the January 2004 storm. The 11,400 tons of sediment 

transported in 3 days represented 64 percent of the annual 

total SSL. Both the streamflow and turbidity at this station 

were greater than any of the other stations during this storm. 

The annual SSY values at Little North were the highest for 

all stations (126 and 99 tons per square mile, respectively) for 

water years 2003–04.

North Santiam River at Mehama

The turbidity and SSL at Mehama are heavily influenced 

by the Little North Santiam River. Mehama is located about 

0.5 mile downstream of the confluence of the Little North 

Santiam River with the mainstem North Santiam River. 

As expected, the highest 3-day SSL at Mehama also was 

during the January 2004 storm. The 11,400 tons of sediment 

transported during this storm comprised only 42 percent of 

the annual total SSL. However, annual total SSL at Mehama

was highest in water year 2002. The SSL of 35,200 tons was 

the second highest SSL for the period of study at any of the 

monitoring stations.

Future Studies

Future research will focus on fluvial sediment sources 

in the North Santiam River basin. Emphasis will be on 

identifying the geomorphic processes responsible for 

supplying sediment to the North Santiam River system. 

Information will be collected on where the events occurred, 

the amount of sediment derived, the mechanism that initiated 

the displacement of material, and how the increase in 

suspended-sediment affected water quality. When possible, 

photographic evidence of the effects of the events will be 

obtained.

Suspended-clay load regression models will be developed 

from fluvial samples and mixtures of water and soil collected 

from known sediment sources throughout the North Santiam 

River basin. More than 500 mixtures of varying concentrations 

will be analyzed from such sources as earth flows, debris 

flows, road cuts and failures, and glacial areas. The clay loads 

are synonymous with persistent turbidity, which has been 

problematic for the city of Salem water-treatment facility to 

treat and eliminate.

Acknowledgments

The authors thank the city of Salem for cooperative 

funding, and city of Salem employees Libby Barg, Jason 

Pulley, Tim Sherman, and Henry Wujcik for providing 

valuable technical expertise and field assistance. We also 

thank David Klug and Doug Shank of the U.S. Forest Service, 

Detroit and Sweet Home Ranger Districts, for their technical 

leadership and field assistance. Others within the U.S. 

Geological Survey who assisted in the collection of samples 

or who contributed their considerable technical skills included 

Amy Brooks, Joseph Rinella, Stewart Rounds, Annett 

Sullivan, and John Williams.

References Cited

Anderson, C.W., 2004, Turbidity (version 2): U.S. Geological 

Survey Techniques of Water-Resources Investigations, book 

9, chap. A6, section 6.7, accessed August 02, 2006, at http://

water.usgs.gov/owq/FieldManual/Chapter6/6.7_contents.

html

Cooper, R.M., 2005, Estimation of peak discharges for rural, 

unregulated streams in western Oregon: U.S. Geological 

Survey Scientific Investigations Report 2005–5116, 134 p.

Edwards, T.K., and Glysson, G.D., 1999, Field methods for 

measurement of fluvial sediment: Techniques of WaterResources Investigations of the U.S. Geological Survey, 

book 3, chap. C2, 89 p.

Helsel D.R., and Hirsh R.M., 1992, Statistical methods in 

water resources: New York, Elsevier, 522 p.

References Cited 25
Hulse, D., Grant G., Niemi, E., Branscomb, A., Diethelm, D., 

Ulrich, R., and Whitelaw, E., 2002, Muddy waters—How 

floods clarify evolving relationships among landscapes 

processes and resource management decision-making in 

municipal watersheds: Eugene, University of Oregon, 

Department of Landscape Architecture, U.S. Environmental 

Protection Agency / National Science Foundation Final 

Project Report GAD# R825822, 32 p.

International Organization for Standardization, 1999, 

Water quality— Determination of turbidity: International 

Organization for Standardization ISO 7027, 10 p.

Oregon Climate Service, 2005, Climate data, zone 4—Climate 

data archives/Daily precipitation/Detroit Dam: accessed 

August 1, 2006, at http://www.ocs.oregonstate.edu/index.

html

Uhrich, M.A., and Bragg, H.M., 2003, Monitoring instream 

turbidity to estimate continuous suspended-sediment 

sediment loads and clay-water volumes in the upper North 

Santiam River Basin, Oregon, 1998–2000: U.S. Geological 

Survey Water-Resources Investigations Report 03-4098, 

43 p.

U.S. Army Corps of Engineers, 1953, Water control manual 

for Detroit and Big Cliff Lakes, Oregon: Portland District 

Report, December 18, 1953.

U.S. Environmental Protection Agency, 1999, Guidance 

manual for compliance with the interim enhanced 

surface water treatment rule—Turbidity provisions: U.S. 

Environmental Protection Agency, Office of Water, EPA 

815-R-99-010 [variously paged].

U.S. Geological Survey, 2000, Water resources data for 

Oregon, Water year 1999: U.S. Geological Survey WaterData Report OR-99-1.

U.S. Geological Survey, 2001, Water resources data for 

Oregon, Water year 2000: U.S. Geological Survey WaterData Report OR-00-1.

U.S. Geological Survey, 2002, Water resources data for 

Oregon, Water year 2001: U.S. Geological Survey WaterData Report OR-01-1.

U.S. Geological Survey, 2003, Water resources data for 

Oregon, Water year 2002: U.S. Geological Survey WaterData Report OR-02-1.

U.S. Geological Survey, 2004, Water resources data for 

Oregon, Water year 2003: U.S. Geological Survey WaterData Report OR-03-1.

U.S. Geological Survey, 2005, Water resources data for 

Oregon, Water year 2004: U.S. Geological Survey WaterData Report OR-04-1.

Wagner, R.J., Boulger, R.W., Jr., Oblinger, C.J., and Smith, 

B.A., 2006, Guidelines and standard procedures for continuous water-quality monitors—Station operation, record 

computation, and data reporting: U.S. Geological Survey 

Techniques and Methods 1–D3, 51 p., 8 attachments, 

accessed April 10, 2006, at http://pubs.water.usgs.gov/

tm1d3

26  Suspended-Sediment Loads and Yields in the North Santiam River Basin, Oregon, Water Years 1999–2004
Manuscript approved for publication, September 4, 2007

Prepared by the USGS Publishing Network 

Bob Crist

Linda Rogers

Sharon Wahlstrom

Bobbie Jo Richey

For more information concerning the research in this report, contact the 

Oregon Water Science Center Director, 

U.S. Geological Survey, 92130 SW 5th Ave.

Portland, OR 97201

http://or.water.usgs.gov
Bragg and others— Suspended-Sediment Loads and Yields, North Santiam River Basin, Oregon, 1999–2004—Scientific Investigations Report 2007–5187