Suspended-Sediment Budget for the North Santiam River 

Basin, Oregon, Water Years 2005–08

Scientific Investigations Report 2010–5038

Prepared in cooperation with the City of Salem

U.S. Department of the Interior

U.S. Geological Survey
Front cover photograph: Upper North Santiam River on November 6, 2006, after a debris 

flow on Mount Jefferson caused increased turbidity in the river.

(Photograph by Heather Bragg, USGS)

Front cover photograph (inset): Scientist collecting a sediment sample at the USGS 

monitoring station on the upper North Santiam River on November 6, 2006.

(Photograph by David Piatt, USGS)

Back cover photograph: Photograph showing the Little North Santiam River on 

November 7, 2006, during high streamflow and turbidity conditions.

(Photograph by Heather Bragg, USGS)
Suspended-Sediment Budget for the 

North Santiam River Basin, Oregon, 

Water Years 2005–08

By Heather M. Bragg and Mark A. Uhrich

Prepared in cooperation with the City of Salem

Scientific Investigations Report 2010–5038

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, 

natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Bragg, H.M., and Uhrich, M.A., 2010, Suspended-sediment budget for the North Santiam River basin, Oregon, water 

years 2005–08: U.S. Geological Survey Scientific Investigations Report 2010–5038, 26 p.
iii

Contents

Significant Findings .......................................................................................................................................1

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

Background and Previous Investigations.........................................................................................1

Purpose and Scope ..............................................................................................................................4

Methods and Data Analysis.........................................................................................................................4

Data Collection......................................................................................................................................4

Station Instrumentation ..............................................................................................................5

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

Quality Assurance.................................................................................................................................5

Cross-Sectional Samples ...........................................................................................................5

Point Samples...............................................................................................................................6

Serial Correlation.........................................................................................................................7

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

Regression Models......................................................................................................................7

North Santiam Regression Models..................................................................................8

Updated Regression Models ............................................................................................9

Error Analysis ...............................................................................................................................9

Estimation of Missing or Erroneous Values.............................................................................9

Missing Turbidity Values....................................................................................................9

North Santiam Suspended-Sediment Concentration .................................................10

Computations of Suspended-Sediment Load........................................................................10

Computations of Suspended-Sediment Budget ...................................................................11

Historic Streamflow ...........................................................................................................................12

Suspended-Sediment Loads......................................................................................................................13

Suspended-Sediment Budget....................................................................................................................16

Summary and Conclusions.........................................................................................................................18

Acknowledgments.......................................................................................................................................18

References Cited..........................................................................................................................................18

Appendix A. Regression Models for Relation of Turbidity and Suspended-Sediment 

Concentration in the North Santiam River Basin......................................................................21

Appendix B. Computation of Suspended-Sediment Concentration at North Santiam, 

November 6–7, 2006.......................................................................................................................23
iv

Tables

Table 1. Streamflow-gaging and water-quality monitoring stations, North Santiam 

River basin, Oregon ........................................................................ 3

Table 2. Water-quality parameters measured at monitoring stations, North Santiam 

River basin, Oregon ........................................................................ 5

Table 3. Comparison of suspended-sediment concentrations of single-point and 

cross-sectional samples, North Santiam River basin, Oregon ........................ 6

Table 4. Regression models for the relation of turbidity and suspended-sediment 

concentration, North Santiam River basin, Oregon, water year 2008 ............... 7

Table 5. Suspended-sediment budget computations, upper and lower North 

Santiam River basin, Oregon, water years 2005–08 .................................... 16

Table 6. Sediment trap efficiency values for Detroit Lake and Big Cliff Reservoir, 

North Santiam River basin, Oregon, water years 2005–08.............................. 17

Figures

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

North Santiam River basin, Oregon ...................................................... 2

Figure 2. Photograph showing Mount Jefferson and the Milk Creek debris flow deposits

of November 6, 2006, North Santiam River basin, Oregon .............................. 4

Figure 3. Graph showing correlation of replicate cross-sectional suspended-sediment

samples, North Santiam River basin, Oregon, water years 1999–2008 ............... 6

Figure 4. Graph showing regression models for the relation of turbidity and

suspended-sediment concentration at North Santiam, North Santiam River

basin, Oregon, water years 1999–2004 ................................................... 8

Figure 5. Graph showing suspended-sediment concentration, streamflow, and sample

collection at North Santiam, North Santiam River basin, Oregon, November

5–7, 2006 .................................................................................... 10

Figure 6. Schematic drawing showing sources of suspended sediment used for budget

calculations, North Santiam River basin, Oregon, water years 2005–08 ............ 11

Figure 7. Graph showing annual mean streamflow at two streamflow-gaging stations,

North Santiam and Little North, North Santiam River basin, Oregon, water

years 1999–2008.............................................................................. 12

Figure 8. Graph showing annual peak streamflow at two streamflow-gaging stations,

North Santiam and Little North, North Santiam River basin, Oregon, water

years 1999–2008.............................................................................. 13

Figure 9. Graphs showing suspended-sediment loads for seven monitoring stations,

North Santiam River basin, Oregon, water years 2005–08.............................. 14

Figure 10. Graph showing total monthly suspended-sediment budget, North Santiam

River basin, Oregon, water years 2005–08................................................ 17
v

Conversion Factors, Datums, and Abbreviations and 

Acronyms

Conversion Factors

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow Rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3s)

Mass

ton, short (2,000 lb) 0.9072 megagram (Mg) 

ton per day per square mile [(ton/d)/mi2] 0.3503 megagram per day per square 

kilometer [(Mg/d)/km2]

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

 ̊F=(1.8× ̊C)+32.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 ̊C).

Suspended-sediment concentrations are reported in milligrams per liter (mg/L). Sediment loads 

are reported in tons.

Water year is the 12-month period from October 1 through September 30 of the following 

calendar year. The water year is designated by the calendar year in which it ends. For example, 

water year 2008 is the period from October 1, 2007, through September 30, 2008.

Datums

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

(NGVD 29).

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

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

Abbreviations and Acronyms

Abbreviation/

acronym

Definition

EWI equal-width-increment

FNU Formazin Nephelometric Unit

MSPE model standard percent error

N number of samples

NWIS USGS National Water Information System

Q streamflow

R2 coefficient of determination

RM river mile

RMSE root mean squared error

SSC suspended-sediment concentration

SSQ suspended-sediment discharge

SSL suspended-sediment load

T turbidity

USGS U. S. Geological Survey

Conversion Factors, Datums, and Abbreviations and 

Acronyms—Continued
Significant Findings

An analysis of sediment transport in the North Santiam 

River basin during water years 2005–08 indicated that: 

• Two-thirds of sediment input to Detroit Lake originated 

in the upper North Santiam River subbasin.

• Two-thirds of the sediment transported past Geren 

Island originated in the Little North Santiam River 

subbasin.

• The highest annual suspended-sediment load at any of 

the monitoring stations was the result of a debris flow 

on November 6, 2006, on Mount Jefferson.

• About 86 percent of the total sediment input to Detroit 

Lake was trapped in the lake, whereas 14 percent was 

transported farther downstream.

• More than 80 percent of the sediment transport in the 

basin was in November, December, and January.

• The variance in the annual suspended-sediment loads 

was better explained by the magnitude of the annual 

peak streamflow than by the annual mean streamflow.

Introduction

The North Santiam River (fig. 1) is the primary source 

of drinking water for more than 177,000 people in Salem, 

Oregon, and those in surrounding communities. The U.S. 

Geological Survey (USGS), in cooperation with the City of 

Salem, has monitored water quality in the North Santiam 

River basin since October 1998 (table 1). Streamflow and 

water-quality data are recorded, transmitted, and available in 

real time on the USGS National Water Information System 

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

provides advance warning of any suspended-sediment surges 

that may require a change of operations at the City of Salem’s 

water treatment facility. The data also are used to compute the 

annual sediment loads at each of the monitoring stations and 

the suspended-sediment budget throughout the basin.

The North Santiam River basin encompasses 778 mi2 on 

the western slopes of the Cascade Range. The basin elevation 

ranges from 10,497 ft at the summit of Mount Jefferson to 

217 ft on the Willamette Valley floor. The City of Salem’s 

drinking water intake is located at the Geren Island water 

treatment facility near Stayton, Oregon (fig. 1). Two U.S. 

Army Corps of Engineers dams (Big Cliff Dam at about river 

mile (RM) 58 and Detroit Dam at about RM 61) regulate 

the flow of the river. Big Cliff Dam primarily is operated as 

run-of-river to reregulate the flow from Detroit Dam. The two 

dams effectively divide the North Santiam River drainage 

into an “upper” basin (upstream of Detroit Dam) and a 

“lower” basin (downstream of Big Cliff Dam and additional 

unregulated tributaries). 

Background and Previous Investigations

In February 1996, a week of heavy rainfall and melting 

snowpack resulted in some of the most severe flooding in 

the history of northwestern Oregon. The North Santiam 

River streamflow-gaging stations crested at 50- to 100‐year 

interval flood events (Cooper, 2005). The increased 

suspended‐sediment load during the flooding caused the City 

of Salem to temporarily shut down the intakes to the water 

treatment facility. In the following weeks, the fluvial sediment 

from the lower basin largely flushed out as the streamflows 

receded, but much of the fine-grained sediment from the 

upper basin was still suspended in Detroit Lake. Because the 

lake water was gradually released downstream, the turbidity 

in the lower North Santiam River basin remained elevated 

for months. The City of Salem was forced to implement 

emergency procedures to remove the sediment from the 

river water and maintain the supply of drinking water to the 

community. Since 1996, improvements at the water treatment 

facility enable it to handle highly turbid water for extended 

periods of time.

Suspended-Sediment Budget for the North Santiam River 

Basin, Oregon, Water Years 2005–08

By Heather M. Bragg and Mark A. Uhrich
2

Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

tac10-0465_fig01

Stayton

14180300

14179000

14178000

DetroitLake

Big CliffReservoir

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

45°00'44°45'44°30'

 

C

A

S

C

A

D

E 

 

RA

NG

E 

MountJefferson

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 Detroit

Dam

Big Cliff Dam

North Santiam River study area

NORTHSANTIAM

EXPLANATION

USGS streamflow-gaging station—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 

Water-quality only monitoring station—See table 1

Boundary of North Santiam River basin

Boundary of subbasin

GEREN ISLAND MEHAMA

LITTLENORTH

ROCK

NIAGARA BREITENBUSH

BLOWOUT

NIAGARA

GEREN ISLAND

4447281224500

14183000

14182500

14181750

14181500

OREGON

Figure location

Salem

5 10 15 20 25 30

00

5 10 15 20

KILOMETERS

MILES

Milk

Pamelia

Creek

Creek

Figure 1. Location of study area and water-quality monitoring stations, North Santiam River basin, Oregon.
Introduction 3

In an effort to understand the sources and transport of 

sediment in the basin, the City of Salem initiated the North 

Santiam River Turbidity and Suspended-Sediment Study in 

cooperation with the USGS. As part of the study, a continuous 

real-time instream monitoring network was established in 

1998. Originally, three stations were installed in the upper 

basin. During water year 2008, the network consisted of seven 

stations monitoring instream water quality and streamflow, 

and one station (Geren Island) monitoring water quality 

only (table 1). The monitoring network provides an advance 

warning system for high turbidity and helps to improve the 

understanding of sediment transport throughout the basin.

Several USGS publications have documented the North 

Santiam River turbidity and suspended-sediment study. 

Uhrich and Bragg (2003) documented the first 2 water years 

of the monitoring program. The report included a detailed 

description of the geology, land use, climate, and hydrology 

of the North Santiam River basin, and also documented the 

methods of data collection and analysis at the three upperbasin monitoring stations (North Santiam, Breitenbush, and 

Blowout). Bragg and others (2007) updated the data analysis 

and reported the suspended-sediment loads for water years 

1999–2004 at the three original stations, one additional 

upper‐basin station (which is no longer in operation), and three 

lower-basin stations (Niagara, Little North, and Mehama). 

Sobieszczyk and others (2007) documented the major turbidity 

events and sediment sources associated with the highest 

suspended-sediment loads during water years 1999–2004. In 

addition, Sobieszczyk and others (2008) described a debris 

flow that occurred in the Milk Creek and Pamelia Creek 

drainage on the western slope of Mount Jefferson (figs. 1

and 2). The fluvial portion of the debris flow emptied into 

the upper North Santiam River, resulting in the highest 

turbidity and suspended-sediment concentration values at any 

monitoring station for the entire period of study (water years 

1999–2008). 

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

[Locations of streamflow-gaging stations used for water-quality monitoring are shown in figure 1. Abbreviations: USGS, U.S. Geological Survey; mi2, square 

miles; na, not applicable]

USGS station No. Station name Station reference

Drainage 

basin area 

(mi2

)

Streamflow record

Period of record 

(water year) Years of record

Upper basin stations (upstream of Detroit Dam)

14178000 North Santiam River below Boulder 

Creek, near Detroit

North Santiam 216 1908–1909, 

1929–2008

82

14179000 Breitenbush River above French 

Creek, near Detroit

Breitenbush 108 1933–1987, 

1999–2008

65

14180300 Blowout Creek near Detroit Blowout 26.0 1999–2008 10

Lower basin stations (downstream of Big Cliff Dam)

14181500 North Santiam River at Niagara Niagara 453 1909–1920, 1922,

1930–2008

83

14181750 Rock Creek near Mill City Rock 14.8 2006–2008 3

14182500 Little North Santiam River near 

Mehama

Little North 112 1932–2008 77

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

1921–2008

95

4447281224500 North Santiam River at Geren Island, 

near Stayton

Geren Island 688 na na
4 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

Purpose and Scope

This report presents a summary of the 

suspended‐sediment budget in the North Santiam River 

basin for water years 2005–08 with the purpose of identifying 

major sediment source areas that may affect water quality 

at the City of Salem’s water treatment facility. The annual 

suspended‐sediment loads are computed at seven monitoring 

stations and the historic streamflow is examined at two 

monitoring stations. The analysis methods involve updating 

the regression models annually for each station and estimating 

the suspended-sediment load related to the debris flow on 

Mount Jefferson. The sediment budget computations include 

the inputs to Detroit Lake, output from Big Cliff Reservoir, 

and additional contributions from the largest lower-basin 

tributaries. The combined sediment-trap efficiency of the 

lakes is calculated, and the seasonal transport of sediment is 

examined.

Methods and Data Analysis

Data Collection

Eight water-quality monitoring stations were in operation 

in the North Santiam River basin during water year 2008. 

Streamflow data were collected at seven of these monitoring 

stations. (The City of Salem’s water treatment facility intake, 

located at Geren Island, is monitored for water quality only.) 

All preliminary data are available in near real-time on the 

project website (U.S. Geological Survey, 2009a). Published 

data are available through the USGS National Water 

Information System (NWIS) website (U.S. Geological Survey, 

2009b).

Figure 2. Mount Jefferson and the Milk Creek debris flow deposits of November 6, 2006, North Santiam River 

basin, Oregon.
Methods and Data Analysis 5

Station Instrumentation

Water-quality data were collected in accordance with 

the maintenance and calibration protocols described by 

Wagner and others (2006) for water temperature, specific 

conductance, pH, turbidity, and dissolved oxygen (table 2). 

All water‐quality monitoring stations were equipped with a 

YSI 6920 multi-parameter instrument. Turbidity was measured 

by a YSI 6026 sensor in Formazin Nephelometric Units 

(FNU) (Anderson, 2005). Each of these sensors has a different 

maximum turbidity value, ranging from 1,200 to 1,800 FNU. 

All parameters were recorded at 30-minute intervals by a 

data‐logger and uploaded every 3 to 4 hours to the USGS 

database. 

Suspended-Sediment Sampling

Suspended-sediment samples collected at the monitoring 

stations provided the data necessary to relate the optical 

property of turbidity to the concentration of sediment in 

the river. Suspended-sediment samples were collected at 

each monitoring station using standard USGS methods 

(Edwards and Glysson, 1999). All samples were analyzed for 

suspended‐sediment concentration (SSC) in milligrams per 

liter. In addition, many samples were analyzed for percent 

of silt and clay and reported in percent finer than 62 μm in 

diameter.

The equal-width-increment (EWI) method was used 

to collect most cross-sectional, depth-integrated samples 

(Edwards and Glysson, 1999). Automatic pumping samplers 

were installed at the three stations in the upper basin. These 

samplers were programmed to collect single-point samples 

from a location near the in-situ water-quality instrument 

when the instream turbidity reached a specific threshold value 

(usually 20, 50, or 100 FNU). Point samples were collected 

at regular intervals until the turbidity was less than that same 

threshold value.

Quality Assurance

Cross-Sectional Samples

During the period of the North Santiam River basin 

study (water years 1999–2008), more than 100 replicate 

cross‐sectional samples were collected at the seven stations 

to assess the precision of the sampling methods and of the 

laboratory results. An ordinary least-squares linear regression 

analysis was completed between the SSC values of pairs of 

concurrent samples (fig. 3). The result was a highly correlative 

(R2 = 0.98) and close to 1:1 relation (slope=1.07) over a wide 

range of SSC values (1–400 mg/L).

Table 2. Water-quality parameters measured at monitoring stations, North Santiam River basin, Oregon.

[Station reference: Complete station names are shown in table 1 and locations are shown in figure 1. Water-quality parameter: X, parameter measured. 

Abbreviation: na, not applicable]

Station reference Instrument 

installation date

Water-quality parameter Period of record

for suspendedsediment sampling

(water years)

Water 

temperature

Specific 

conductance pH Turbidity Dissolved oxygen

Upper basin stations (upstream of Detroit Dam)

North Santiam October 1998 X X X X 1999–2008

Breitenbush October 1998 X X X X 1999–2008

Blowout October 1998 X X X X 1999–2008

Lower basin stations (downstream of Big Cliff Dam)

Niagara April 2000 X X X X 1999–2008

Rock September 2005 X X X X 2006–2008

Little North April 2000 X X X X 1999–2008

Mehama April 2000 X X X X 1999–2008

Geren Island March 2001 X X X X X na
6 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

Point Samples

The automatic samplers at the three upper-basin stations 

were activated regularly before and after collection of EWI 

samples to assess the representativeness of single‐point 

SSC to cross-sectional SSC. The SSC values of each pair 

of point samples were interpolated to the mean time of the 

corresponding EWI sample. An ordinary least-squares linear 

regression analysis was performed on the data from each 

monitoring station (table 3). The results show good correlation 

between the automatic point samples and the cross‐sectional 

EWI samples at North Santiam and Breitenbush over 

the entire range of sample SSC values (10–14,500 and 

2–660 mg/L, respectively). Results from Blowout also show 

good correlation, except at high SSC (greater than 400 mg/L) 

and high streamflow (greater than 2,500 ft3/s). As a result, 

any point samples collected at Blowout when either of these 

conditions was exceeded were not included in further data 

analysis.

tac10-0465_fig03

0.1 

1 

10 

100 

1,000 

0.1 1 10 100 1,000 

REPLICATE SAMPLE SUSPENDED-SEDIMENT 

CONCENTRATION, IN MILLIGRAMS PER LITER 

PRIMARY SAMPLE SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER 

Sample pairs 

Simple linear regression 

1:1 reference line

Figure 3. Correlation of replicate cross-sectional suspended-sediment samples, North Santiam River basin, Oregon, 

water years 1999–2008.

Table 3. Comparison of suspended-sediment concentrations of 

single-point and cross-sectional samples, North Santiam River 

basin, Oregon.

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

locations are shown in figure 1. R2, coefficient of determination; N, number 

of samples. Abbreviations: ft3/s, cubic feet per second; mg/L, milligrams per 

liter]

Station reference Slope R2 N

North Santiam 1.04 0.999 15

Breitenbush 1.06 1.00 4

Blowout 0.819 0.962 10

Blowout1 1.06 0.999 7

1

Streamflow (Q) < 2,500 ft3/s and suspended-sediment concentration (SSC) 

< 400 mg/L.
Methods and Data Analysis 7

Serial Correlation

The point samples at the three upper-basin stations were 

shown to be acceptably representative of their respective 

cross sections, but the large number of these samples and 

the timing of their collection likely would introduce serial 

correlation biases into the regression analyses. The vast 

majority of the more than 550 point samples collected by the 

automatic samplers during water years 2004–08 were caused 

by high‐turbidity conditions. Once an automatic sampler 

was activated, samples were collected until the instream 

turbidity was less than the threshold value. As a result, 

as many as 24 samples could be collected during a single 

storm. In order to minimize the potential bias, one to three 

point samples (depending on the duration of the event) were 

selected randomly from any single storm or sampling event for 

inclusion in the model calibration datasets.

Data Analysis

Regression models were developed between sample 

suspended-sediment concentration (SSC) and turbidity (T) 

as a means of estimating continuous SSC using continuous 

turbidity data. The estimated SSC and streamflow (Q) were 

then used to compute annual suspended-sediment loads (SSL) 

at each of the monitoring stations for water years 2005–08. 

Uhrich and Bragg (2003) and Bragg and others (2007) 

previously reported the methods for this analysis. 

Regression Models

Regression models were developed between turbidity 

and SSC for each of the monitoring stations. Turbidity data 

for the analyses were provided by the instream water-quality 

monitors. The 30-minute turbidity values, in FNU, recorded 

during the time of sample collection were averaged to produce 

a single turbidity value associated with each sample. The SSC 

values, in milligrams per liter, were provided by laboratory 

analysis of each sample (Guy, 1969). The pairs of turbidity 

and SSC data for each sample were used as the calibration 

dataset for the regression model. 

The turbidity and SSC values were transformed to 

base‐10 logarithmic values to improve the normal distribution 

of the dataset prior to ordinary least-squares linear regression 

analysis. The form of the regression model equation is:

10 10 log (SSC) log (T) ,

where

SSC is suspended-sediment concentration;

T is turbidity;and

and are the slope and y-intercept coefficients,

respectively, obtained by the regression

analysis.

a b

a b

= + (1)

The logarithmic transformation and subsequent conversion 

back to original form introduced a known bias, which was 

negated with a correction factor (Helsel and Hirsch, 2002). 

The predicted SSC value resulting from the model equation 

was multiplied by the bias-correction factor to obtain the 

corrected SSC value (table 4).

Table 4. Regression models for the relation of turbidity and suspended-sediment concentration, North Santiam River basin, Oregon, 

water year 2008.

[Station reference: Complete station names are shown in table 1 and locations are shown in figure 1. N, number of samples; R2, coefficient of determination; 

MSPE, model standard percent error; SSC, suspended-sediment concentration; T, turbidity]

Station reference Regression model equation Bias-correction 

factor N R2 Upper 

MSPE

Lower 

MSPE

North Santiam 

(Precipitation-driven)

log10 SSC = 1.12 log10 T + 0.224 1.12 151 0.95 60.0 37.5

North Santiam

(Meltwater-driven)

log10 SSC = 0.898 log10 T + 0.0772 1.03 40 0.95 28.8 22.4

Breitenbush log10 SSC = 1.06 log10 T + 0.215 1.09 119 0.96 50.7 33.6

Blowout log10 SSC = 1.09 log10 T + 0.140 1.10 169 0.95 54.7 35.3

Niagara log10 SSC = 0.727 log10 T + 0.163 1.10 78 0.84 54.1 35.1

Rock log10 SSC = 1.05 log10 T + 0.243 1.06 27 0.94 45.3 31.2

Little North log10 SSC = 1.02 log10 T + 0.209 1.12 131 0.92 60.9 37.8

Mehama log10 SSC = 0.931 log10 T + 0.164 1.15 137 0.87 73.2 42.2
8 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

North Santiam Regression Models

The operation of the automatic sampler at the North

Santiam station revealed a process of sediment transport that 

had not been addressed in previous analyses. Two instances of 

high turbidity (greater than the turbidity sensor limit of about 

1,600 FNU) with no corresponding increase in streamflow 

were investigated by Sobieszczyk and others (2007). The 

sediment causing the high turbidity was associated with 

meltwater from the glaciers and snowfields in the Milk Creek 

and Pamelia Creek subbasins, located high on the slopes of 

Mount Jefferson (fig. 1). Analysis of the samples collected 

during these events revealed a relation between instream 

turbidity and SSC that was different from that normally 

measured during typical storm events, necessitating the 

revision of the previously published regression model (Bragg 

and others, 2007).

The previous model included samples collected at North

Santiam during water years 1999–2004. For the revised 

analysis, all suspended-sediment samples collected during 

those years were categorized on the basis of the conditions 

during which they were collected. Typically occurring in 

0.1 

1 

10 

100 

1,000 

10,000 

0.1 1 10 100 1,000 10,000 

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER 

INSTREAM TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS

Previously published model (Bragg and others, 2007) 

Samples 

Revised model (precipitation-driven) 

Samples 

Revised model (meltwater-driven) 

Samples 

Figure 4. Regression models for the relation of turbidity and suspended-sediment concentration at North Santiam, 

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

late summer or early fall, glacial outwash events resulted 

when warm air temperatures rapidly melted glacial ice and 

snowfields, transporting newly exposed sediment downstream. 

These events were identified at the monitoring station by 

a sharp increase in turbidity but little or no increase in 

streamflow. The summer melting of snow and ice at high 

elevations also caused small-magnitude diurnal cycles 

of streamflow and turbidity at North Santiam. Samples 

collected during either of these conditions were classified as 

“meltwater‐driven.” During the fall and winter rainy season, 

increases in instream turbidity usually were accompanied by a 

proportional increase in streamflow. Samples collected during 

these conditions were classified as “precipitation-driven.” 

The two newly classified sample sets were used to develop 

two new regressions to replace the single previous regression 

(fig. 4). The new regression models were not used to revise 

previous suspended-sediment load computations, but only to 

establish benchmark models for future analysis. Both revised 

North Santiam regression models were updated for each 

subsequent water year as described below. 
Methods and Data Analysis 9

Updated Regression Models

As water-quality data collection continued at all 

monitoring stations, the regression models required updating 

and verification. The regression models reported in Bragg 

and others (2007) were developed with suspended-sediment 

samples collected through water year 2004. Beginning in 

water year 2005, a newly established method for annually 

updating the regression models involved adding samples 

collected during each subsequent water year to the model 

calibration dataset (Rasmussen and others, 2009). The 

regression analysis at each monitoring station was repeated 

with the complete dataset to determine whether the 

coefficients (a and b, eq. 1) of the new equation had changed 

significantly from the equation used the previous water year. If 

no significant difference was detected between the two model 

equations, the regression model incorporating the newly 

collected samples was used to calculate the continuous SSC 

record for that water year. If the coefficients were significantly 

different, a new regression model could be established 

with either the samples collected after the date of a known 

change in sediment source or the samples collected during 

the new water year. The water year 2008 regression models 

(table 4) include samples collected during the entire period 

of suspended-sediment sampling for each station (table 2). A 

table of annually updated regression models for all stations for 

all water years (1999–2008) is available in appendix A. 

The North Santiam regression models for 

precipitation‐driven events demonstrated a significant 

change from water year 2006 to 2007 (appendix A). An 

analysis of the covariance between the two models indicated 

a significant difference in the slope (a; which increased) and 

the y-intercept (b; which decreased). This shift likely was a 

result of the inclusion of samples collected in the days and 

weeks following the November 2006 debris flow on Mount 

Jefferson. These samples reflected the documented change 

in available sediment in the upper elevations of the basin, 

which persisted through the water year. The water year 2007 

model that incorporated the new samples was therefore used 

to calculate the precipitation-driven portions of the continuous 

SSC record for North Santiam. The water year 2008 

precipitation-driven model shifted slightly in the opposite 

direction (the slope decreased and the y-intercept increased), 

indicating that the effect of the additional sediment source 

may have been largely temporary.

Error Analysis

Several of the summary statistics recommended by 

Rasmussen and others (2009) were computed to evaluate the 

regression models (table 4). The coefficient of determination 

(R2) indicates the part of the variance explained by the 

regression. The root mean squared error (RMSE) of the 

regression was calculated in log-10 units and converted to 

the upper and lower model standard percent errors (MSPE). 

These percentages indicate the variance between the predicted 

and measured values and can be used to compare regression 

models. For example, lower magnitude MSPE values indicate 

less uncertainty in the predicted values. These statistics were 

considered when evaluating SSL computations and comparing 

SSL values between monitoring stations.

Regression models for water year 2008 for stations in 

the upper North Santiam River basin indicated high R2 values 

and acceptable MSPE values. The regression models for the 

two lower-basin stations subject to streamflow regulation 

by the dams showed the most uncertainty. The R2 value was 

lower at Niagara, but the MSPE range was comparable to 

the upper‐basin stations. The MSPE range was greatest at 

Mehama, indicating the highest uncertainty in predicted SSC 

values. The greater uncertainty was attributed to the varied 

turbidity bias in the cross-section at Mehama resulting from 

the regulated streamflow from Big Cliff Dam and from the 

confluence of the Little North Santiam River less than 1 mile 

upstream of the station.

Estimation of Missing or Erroneous Values

Missing Turbidity Values

A complete SSC record, in 30-minute time increments, 

was needed to compute annual SSL. When turbidity values 

used to calculate SSC were missing from the record, values 

were estimated by several methods. Using the simplest 

method, the 30-minute values were estimated by interpolating 

between the recorded values immediately before and after 

the missing period. This method worked well for short time 

periods when streamflow conditions were steady or when 

turbidity consistently was increasing or decreasing. For longer 

periods or during changing streamflow conditions, turbidity 

was estimated by comparing values at adjacent monitoring 

stations. This method worked best when two stations had long 

periods of record that demonstrated a well-defined correlation 

between turbidity values.

The turbidity at Rock was estimated for several periods of 

missing or erroneous data. Correlation with Little North data 

was used to complete the turbidity record for December 15, 

2006–January 5, 2007, which included a moderate storm 

event. Interpolation was used to complete the Rock turbidity 

record during the low-streamflow periods of January 26–

March 5, 2008, and May 18–27, 2008. The other stations 

in the monitoring network had few instances of missing 

30-minute turbidity values and were estimated by simple 

interpolation. The estimated turbidity values were used to 

calculate SSC at each respective monitoring station. 
10 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

North Santiam Suspended-Sediment Concentration

During one major sediment transport event, the 

continuous SSC record was computed more directly from 

samples, rather than from estimated turbidity. The debris 

flow that occurred in the Pamelia and Milk Creek subbasin 

on Mount Jefferson resulted in extremely elevated turbidity 

and SSC at North Santiam on November 6–7, 2006. When 

the recorded turbidity values remained constant at 1,600 FNU 

on November 6 during 0200–0730 and 0930–1600, the 

instream turbidity was known to be equal to or greater than 

that value. During these periods, more than a dozen point and 

EWI samples were collected (fig. 5). On November 6 during 

0800–0900, several turbidity values were recorded that were 

less than the sensor maximum value. The meltwater-driven 

regression model was used to estimate SSC during these times 

because no samples were collected. Using a combination of 

sample SSC, turbidity-estimated SSC, and interpolation, the 

continuous SSC record was completed for this unusual event. 

The estimated 30-minute SSC computations for North Santiam

on November 6–7, 2006, are available in appendix B. 

0 

2,000 

4,000 

6,000 

8,000 

10,000 

0 

0:00 12:00 0:00 12:00 0:00 12:00 0:00 

5,000 

10,000 

15,000 

20,000 

25,000 

5 6 7 

STREAMFLOW, IN CUBIC FEET PER SECOND 

SUSPENDED-SEDIMENT CONCENTRATION, IN MILLIGRAMS PER LITER 

Suspended-sediment concentration 

Samples 

Streamflow

NOVEMBER, 2006

Figure 5. Suspended-sediment concentration, streamflow, and sample collection at North Santiam, North 

Santiam River basin, Oregon, November 5–7, 2006.

Computations of Suspended-Sediment Load

Estimated 30-minute SSC (in mg/L) and corresponding 

streamflow (Q) values, in cubic feet per second (ft3/s), were 

used to calculate the suspended-sediment discharge (SSQ; 

equation 2), in tons per 30 minutes:

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

where

c equals 0.0000562 to convert the units to tons 

per 30 minutes.

= × × (2)

The daily SSL is computed by summing the 48 estimated SSQ 

values per day. The annual SSL is calculated by summing the 

365 (or 366) daily SSL values.
Methods and Data Analysis 11

North Santiam Breitenbush Blowout

Rock

Little North

Niagara

Suspended-sediment input

to Detroit Lake

Suspended-sediment output

from Big Cliff Reservoir 

Suspended-sediment load

of North Santiam River at

Geren Island 

Figure 6. Sources of suspended sediment used for budget calculations, North 

Santiam River basin, Oregon, water years 2005–08.

Prediction intervals were calculated for each of the 

regression models in order to provide error estimates for the 

annual SSL values. For each estimated 30-minute SSC value, 

the upper and lower predictions were calculated at 90 percent 

confidence. High and low annual SSL totals were calculated 

as described above from the continuous upper and lower SSC 

prediction records.

Computations of Suspended-Sediment Budget

Annual SSL totals were used to summarize the 

suspended-sediment budget in the North Santiam River basin 

for water years 2005–08 (fig. 6). The SSL from the three 

stations in the upper basin (North Santiam, Breitenbush, and 

Blowout) were summed to compute the sediment input to 

Detroit Lake. The SSL at Niagara represented the sediment 

output from Detroit Lake and Big Cliff Reservoir. The total 

SSL flowing past Geren Island was defined as the sum of 

Niagara, Rock (if data were available), and Little North. 

Although the SSL was estimated at Mehama for all water 

years, it was not used in the sediment budget because of the 

high uncertainty of the regression models.

The relative percent contribution of each monitoring 

station to each step of the suspended-sediment budget was 

computed for each water year. In addition, the relative percent 

contribution of each monitoring station was computed for 

the total 4-year suspended-sediment budget of water years 

2005–08. 
12 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

0 

300 

600 

900 

1,200 

1,500 

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 

ANNUAL MEAN STREAMFLOW, IN CUBIC FEET PER SECOND 

WATER YEAR 

North Santiam 

Little North 

Median

(period of record) 

Median

(period of record) 

Figure 7. Annual mean streamflow at two streamflow-gaging stations, North Santiam (14178000) and 

Little North (14182500), North Santiam River basin, Oregon, water years 1999–2008.

The total suspended-sediment budget for water years 

2005–08 also was analyzed by month to examine and quantify 

the season for peak sediment transport. The monthly sums for 

each step of the budget (input to Detroit Lake, output from Big 

Cliff Reservoir, and flow past Geren Island) were expressed as 

a percentage of the total 4-year sediment budget.

The difference between the sediment input to Detroit 

Lake and the sediment output from Big Cliff Reservoir (as 

measured at Niagara) was used to estimate the combined trap 

efficiency of the reservoirs (eq. 3).

i 0 i

i

0

Trap efficiency = (SSL SSL )/SSL ,

where

SSL is total suspended-sediment load input to 

Detroit Lake; and

SSL is total suspended-sediment load output from

Big Cliff Reservoir.

− (3)

About 27 percent of the water volume measured at 

Niagara during water years 2005–08 was not accounted 

for by the streamflow measured at the three upper-basin 

monitoring stations. Reservoir storage changes, groundwater 

input, and unmonitored tributaries could account for the water 

volume difference. Because the trap efficiency calculation 

did not account for the sediment input associated with any 

unmeasured streamflow entering Detroit Lake, there likely 

was a negative bias on the estimates. The actual annual trap 

efficiencies of Detroit Lake and Big Cliff Reservoir likely 

were higher than the calculated values.

Historic Streamflow 

Streamflow data from two of the monitoring stations 

in the North Santiam River basin were analyzed to provide 

context for the suspended-sediment load and budget 

computations. Annual streamflow is highest at North Santiam

in the upper basin and, for unregulated streams, at Little North

in the lower basin. Annual mean streamflow for water years 

during the period of the North Santiam River study (water 

years 1999–2008) are shown in figure 7. The median value for 

each dataset was calculated from the annual mean streamflow 

values for the entire period of record at each station (table 1). 

The peak instantaneous streamflow values for the water years 

during the period of the study are shown in figure 8. The 

median value for each dataset was calculated from the annual 

peak streamflow values for the entire period of record at each 

station (table 1).
Suspended-Sediment Loads 13

Suspended-Sediment Loads

Annual SSL totals were computed for water years 

2005–08 for each monitoring station for which streamflow and 

turbidity data were available (fig. 9). The error bars indicate 

the 90 percent prediction interval estimates for each annual 

SSL value.

For the low annual mean and peak streamflow in water 

year 2005, the SSL values were the lowest for the 4 years 

analyzed. In water year 2006, SSL at Breitenbush and 

Blowout was the highest of the 4 water years. SSL at North 

Santiam also was high in water year 2006, but was highest 

in water year 2007 because of the Mount Jefferson debris 

flow and subsequent storm event. SSL was highest during 

water year 2007 for all lower basin stations for the 4 water 

years. The streamflow conditions during water year 2008 

resulted in lower SSL values than might be expected for an 

above-average mean flow year. The lack of significant peak 

streamflows resulted in SSL totals at all seven monitoring 

stations that were only slightly higher than those during the 

much lower streamflow in water year 2005. tac10-0465_fig08

6,000 

12,000 

18,000 

24,000 

30,000 

PEAK INSTANTANEOUS STREAMFLOW, IN CUBIC FEET PER SECOND 

North Santiam 

Little North 

Median

(period of record) 

Median

(period of record) 

0 

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 

WATER YEAR 

Figure 8. Annual peak streamflow at two streamflow-gaging stations, North Santiam (14178000) and Little 

North (14182500), North Santiam River basin, Oregon, water years 1999–2008.

Streamflow throughout the basin was less than normal 

for water year 2005, as demonstrated by the annual mean and 

peak flows at North Santiam and Little North. Streamflow 

for water year 2006 was slightly less than normal for 

Little North but greater than normal for North Santiam. In 

January 2006, the recurrence interval for peak streamflow 

at North Santiam was 5–10 years. Recurrence interval for 

peak streamflow at Little North during the same storm 

was less than 2 years. Water year 2007 included a storm in 

November 2006 that resulted in a peak streamflow with a 

2–5 year recurrence interval at North Santiam and with a 

5–10 year recurrence interval at Little North. During that year, 

the annual mean streamflow for North Santiam and Little

North was approximately normal. Annual mean streamflow 

of the 4 years analyzed was highest in water year 2008, yet 

recurrence intervals for peak flows were less than 2 years. 

This was a result of the above-average, late-melting snowpack 

in the Cascade Range, which caused increased flows at all 

seven stations beginning in May 2008 and continuing into the 

summer. 
14 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

Figure 9. Suspended-sediment loads for seven monitoring stations, North Santiam River basin, Oregon, 

water years 2005–08. Error bar indicates 90-percent prediction interval estimate for each annual SSL 

value.

tac10-0465_fig09ab

3,100 2,640 1,620 966 

9,750 12,900 

0 

40,000 

80,000 

120,000 

160,000 

200,000 

North Santiam Breitenbush Blowout Niagara Rock Little North Mehama 

North Santiam Breitenbush Blowout Niagara Rock Little North Mehama 

STATION REFERENCE 

STATION REFERENCE 

WATER YEAR 2005 

[No data] 

52,600 

23,800 

10,200 11,800 

4,640 

23,000 

47,000 

0 

40,000 

80,000 

120,000 

160,000 

200,000 

ANNUAL SUSPENDED-SEDIMENT LOAD, IN TONS 

WATER YEAR 2006 
Suspended-Sediment Loads 15

tac10-0465_fig09cd

0 

40,000 

80,000 

120,000 

160,000 

200,000 

40,000 

80,000 

120,000 

160,000 

200,000 

0 

90,200 

23,400 

5,320 

13,800 12,300 

63,400 

80,400 

WATER YEAR 2007 

ANNUAL SUSPENDED-SEDIMENT LOAD, IN TONS 

13,400 

7,870 3,730 7,830 

1,520 

10,600 

25,800 

WATER YEAR 2008 

North Santiam Breitenbush Blowout Niagara Rock Little North Mehama 

North Santiam Breitenbush Blowout Niagara Rock Little North Mehama 

STATION REFERENCE 

STATION REFERENCE 

Figure 9.—Continued.
16 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

suspended-sediment input to Detroit Lake into the late 

spring. The lake level was kept below full pool elevation by 

increasing the outflow from Detroit Dam throughout May 

and June 2008. This movement of water through the lake 

prevented the suspended sediment from settling and resulted 

in a trap efficiency value lower than the other 3 water years. 

The increased streamflow and SSL at Niagara in the spring 

and summer of water year 2008 also resulted in the highest 

proportion (39 percent) of the lower basin suspended-sediment 

budget for water years 2005–08 at that station. SSL inputs to 

the lake were higher during water years 2006 and 2007, but 

the suspended sediment had more time to settle, resulting in 

lower percentage contributions at Niagara to the lower basin 

sediment budget.

The monthly suspended-sediment budget results are 

presented in figure 10. Late fall and early winter were the 

dominant seasons for sediment transport during water years 

2005–08. About 90 percent of the sediment input to Detroit 

Lake and 80 percent of the sediment output from Big Cliff 

Reservoir was in November, December, and January during 

the 4 years. November and December were the highest 

months for input to the lake, while January was the highest 

for output. This demonstrates the capacity of Detroit Lake to 

store suspended sediment and delay its release downstream. 

During these same months, 87 percent of the total SSL was 

transported past the City of Salem’s Geren Island water 

treatment facility.

Suspended-Sediment Budget

The results of the annual suspended-sediment budget 

computations are presented in table 5. During water years 

2005–08, the upper North Santiam River was the largest 

contributor of suspended sediment to Detroit Lake. The 

4-year SSL total at North Santiam was dominated by sediment 

transported during the Mount Jefferson debris flow and the 

subsequent storm in water year 2007. The Breitenbush River 

was the second largest sediment contributor in the upper basin 

followed by Blowout Creek.

The Little North Santiam River was the largest 

contributor of suspended sediment to the North Santiam River 

at Geren Island for water years 2005–08. The highest SSL and 

second-highest annual percentage at Little North were related 

to the peak winter storms during water year 2007. (The highest 

annual proportion for Little North was artificially inflated 

because of the lack of data for Rock in water year 2005.) The 

output from Detroit Lake (Niagara) was the second largest 

sediment contributor in the lower basin followed by Rock 

Creek.

The computed trap efficiencies of Detroit Lake (table 6) 

were consistent during water years 2005–07, despite the 

variation in annual mean streamflow. In water year 2008, 

the record snowpack in the Cascade Range (more than 

200 percent of the 30-year average; Natural Resources 

Conservation Service, 2009) increased the streamflow and 

Table 5. Suspended-sediment budget computations, upper and lower North Santiam River basin, Oregon, water years 2005–08.

[Station reference: Complete station names are shown in table 1 and locations are shown in figure 1. Annual SSL is the estimated suspended-sediment load at 

the monitoring station. Percentage of total is the portion of the total SSL contribution to Detroit Lake from the basin upstream of the monitoring station. SSL, 

suspended-sediment load. na, not applicable]

Station 

reference

Water year Total 

2005 2006 2007 2008 2005–08

Annual SSL 

(tons)

Percentage 

of total

Annual SSL 

(tons)

Percentage 

of total

Annual SSL 

(tons)

Percentage 

of total

Annual SSL 

(tons)

Percentage 

of total

Annual SSL 

(tons)

Percentage 

of total

Suspended-sediment contribution to Detroit Lake

North Santiam 3,100 42 52,600 61 90,200 76 13,400 54 159,300 67

Breitenbush 2,640 36 23,800 27 23,400 20 7,870 31 57,710 24

Blowout 1,620 22 10,200 12 5,320 4 3,730 15 20,870 9

Annual SSL for 

Detroit Lake 

(tons)

7,360 86,600 118,920 25,000 237,880

Suspended-sediment contribution for North Santiam River at Geren Island

Niagara 970 9 11,800 30 13,800 15 7,830 39 34,400 22

Rock na na 4,640 12 12,300 14 1,520 8 18,460 12

Little North 9,750 91 23,000 58 63,400 71 10,600 53 106,750 67

Annual SSL for 

North Santiam 

River at Geren 

Island (tons)

10,720 39,440 89,500 19,950 159,610
Suspended-Sediment Budget 17

0 

10 

20 

30 

40 

50 

OCTOBER 

NOVEMBER 

DECEMBER 

JANUARY 

FEBRUARY 

MARCH 

APRIL 

MAY 

JUNE 

JULY 

AUGUST 

SEPTEMBER 

PERCENT OF TOTAL SEDIMENT BUDGET, WATER YEARS 2005–08 

Suspended-sediment input to Detroit Lake 

Suspended-sediment output from Big Cliff Reservoir 

Suspended sediment for North Santiam River at Geren Island 

Figure 10. Total monthly suspended-sediment budget, North Santiam River basin, Oregon, water years 2005–08.

Table 6. Sediment trap efficiency values for Detroit Lake and Big 

Cliff Reservoir, North Santiam River basin, Oregon, water years 

2005–08. 

Water year Total 

2005–08 2005 2006 2007 2008

Input to Detroit 

Lake (tons)

7,360 86,600 118,920 25,000 237,880

Output from Big 

Cliff Reservoir 

(tons)

970 11,800 13,800 7,830 34,400

Reservoir trap 

efficiency 

(percent)

87 86 88 69 86
18 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

Summary and Conclusions

In cooperation with the City of Salem, the U.S. 

Geological Survey investigated the sources and transport 

of sediment in the North Santiam River basin during water 

years 2005–08. Seven monitoring stations were in operation 

throughout the basin, providing continuous streamflow and 

instream turbidity data. Newly collected cross-sectional and 

point samples were added to previously published analyses 

in order to verify and update the regression models relating 

turbidity and suspended-sediment concentration. These 

models were used to estimate continuous suspended-sediment 

concentration records and annual suspended-sediment loads at 

each of the monitoring stations. 

The upper North Santiam River was determined to 

have a sediment source that required a separate regression 

model for estimating suspended-sediment concentration. 

During the summer and early fall, the melting glaciers and 

snowfields on Mount Jefferson transported sediment from 

high on the exposed mountain slopes, resulting in a distinct 

suspended‐sediment concentration for any given turbidity. The 

two regression models for the upper North Santiam monitoring 

station produced better suspended-sediment concentration 

estimates than the previously published single regression 

model.

During water years 2005–08, the basin was exposed to a 

variety of environmental conditions, producing a wide range 

of suspended-sediment transport results. The low annual 

streamflow and lack of major storms during water year 2005 

demonstrated how little sediment could be transported through 

the basin. A major storm during January 2006 produced 

the highest peak streamflows in the upper basin during the 

4 years, resulting in the highest suspended-sediment loads 

at two of the three upper-basin stations. The upper North 

Santiam River had its highest sediment load following the 

debris flow on Mount Jefferson during November 2006 (water 

year 2007). This event and the subsequent storm contributed 

to the largest annual suspended-sediment load computed for 

any of the monitoring stations, as well as the largest annual 

suspended‐sediment load to pass through Detroit Lake 

and Big Cliff Reservoir during the period of study. Peak 

streamflows in the lower basin were highest in association 

with the same storm of water year 2007, producing the highest 

suspended‐sediment loads at all lower-basin stations. The 

annual mean streamflows in water year 2008 were the highest 

for the 4 years, but the peak streamflows were only slightly 

higher than during water year 2005. The suspended-sediment 

loads across the basin were similarly low during water year 

2008. This indicated that suspended-sediment loads correlate 

better to peak streamflows, not mean streamflows, in the North 

Santiam River basin.

Water years 2005–08 presented examples of a wide 

range of sediment transport conditions in the North Santiam 

River basin. The 4-year total sediment budget provides a more 

balanced assessment. The upper basin tributaries contributed 

nearly 240,000 tons of sediment to Detroit Lake during the 

4 years. However, only 14 percent of that sediment load was 

transported through the lake into the lower basin. Nearly 

160,000 tons of sediment were transported by the North 

Santiam River as computed at Geren Island during the 4 years. 

Despite the massive debris flow in the upper basin, it was 

precipitation-driven, high-flow events in the lower basin that 

contributed the greatest sediment loads to the source water for 

the City of Salem’s water treatment facility. 

Acknowledgments

The authors would like to acknowledge the City of Salem 

and thank them for the cooperative funding that made this 

study possible. In addition, we thank the USGS personnel, 

including Amy Brooks, David Piatt, and Steven Sobieszczyk, 

that provided support in creating this product. Lastly, we 

would like to acknowledge the reviewers whose comments 

and suggestions greatly improved this report. 

References Cited

Anderson, C.W., 2005, Turbidity (version 2.1): U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6, section 6.7.

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, 1999–2004: 

U.S. Geological Survey Scientific Investigations Report 

2007‐5187, 26 p.

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: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. C2, 89 p. 

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p. 
References Cited 19

Helsel, D.R., and Hirsh R.M., 2002, Statistical methods in 

water resources: U.S. Geological Survey Techniques and 

Methods, book 4, chap. A3, 523 p.

Natural Resources Conservation Service, [2009], Oregon 

SNOTEL website, accessed August 17, 2009, at http://www.

wcc.nrcs.usda.gov/snotel/Oregon/oregon.html.

Rasmussen, P.P., Gray, J.R., Glysson, G.D., and Ziegler, 

A.C., 2009 Guidelines and procedures for computing 

time-series suspended-sediment concentrations and loads 

from in-stream turbidity-sensor and streamflow data: U.S. 

Geological Survey Techniques and Methods, book 3, 

chap. C4, 53 p.

Sobieszczyk, Steven, Uhrich, M.A., and Bragg, H.M., 2007, 

Major turbidity events in the North Santiam River Basin, 

Oregon, 1999–2004: U.S. Geological Survey WaterResources Investigations Report 07-5178, 50 p.

Sobieszczyk, Steven, Uhrich, M.A., Piatt, D.R., and Bragg, 

H.M., 2008, Analysis of geomorphic and hydrologic 

characteristics of Mount Jefferson debris flow, Oregon, 

November 6, 2006: U.S. Geological Survey WaterResources Investigations Report 2008-5204, 18 p.

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

turbidity to estimate continuous suspended-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. Geological Survey, 2009a, North Santiam River basin 

turbidity and suspended-sediment study: Water-quality 

monitoring network website, accessed November 4, 2009, 

at http://or.water.usgs.gov/santiam/index.html.

U.S. Geological Survey, 2009b, USGS water data for Oregon: 

National Water Information System website, accessed 

November 4, 2009, at http://waterdata.usgs.gov/or/nwis.

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 January 26, 2010, at http://pubs.

water.usgs.go0v/tm1d3.
20 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

This page intentionally left blank.
Appendix A 21

Station reference Regression model equation

Bias 

correction 

factor

N R2 Upper 

MSPE

Lower 

MSPE

Water years 1999–2004

North Santiam log10 SSC = 1.04 log10 T + 0.188 1.13 121 0.89 68.0 40.5

Breitenbush log10 SSC = 1.08 log10 T + 0.183 1.18 80 0.92 71.3 41.6

French log10 SSC = 1.01 log10 T - 0.0127 1.28 34 0.82 105 51.3

Blowout log10 SSC = 1.18 log10 T + 0.0683 1.16 118 0.93 62.3 38.4

Niagara log10 SSC = 0.758 log10 T + 0.123 1.12 64 0.76 63.2 38.7

Little North log10 SSC = 1.02 log10 T + 0.193 1.14 125 0.92 66.3 39.8

Mehama log10 SSC = 0.916 log10 T + 0.170 1.17 131 0.86 78.6 44.0

Water year 2004 (Revised)

North Santiam (Precipitation-driven) log10 SSC = 1.07 log10 T + 0.243 1.12 116 0.91 60.2 37.6

North Santiam (Meltwater-driven) log10 SSC = 0.907 log10 T + 0.0651 1.04 32 0.95 31.0 23.6

Water year 2005

North Santiam (Precipitation-driven) log10 SSC = 1.08 log10 T + 0.240 1.11 122 0.92 58.8 37.0

North Santiam (Meltwater-driven) log10 SSC = 0.908 log10 T + 0.0690 1.03 35 0.95 30.0 23.1

Breitenbush log10 SSC = 1.03 log10 T + 0.220 1.08 92 0.96 48.8 32.8

Blowout log10 SSC = 1.08 log10 T + 0.150 1.12 127 0.93 58.4 36.9

Niagara log10 SSC = 0.718 log10 T + 0.156 1.11 62 0.79 59.3 37.2

Little North log10 SSC = 1.03 log10 T + 0.196 1.12 123 0.91 61.9 38.2

Mehama log10 SSC = 0.931 log10 T + 0.146 1.14 127 0.87 71.4 41.6

Water year 2006

North Santiam (Precipitation-driven) log10 SSC = 1.10 log10 T + 0.233 1.10 136 0.94 56.8 36.2

North Santiam (Meltwater-driven) log10 SSC = 0.908 log10 T + 0.0690 1.03 35 0.95 30.0 23.1

Breitenbush log10 SSC = 1.05 log10 T + 0.218 1.09 103 0.96 50.3 33.4

Blowout log10 SSC = 1.08 log10 T + 0.143 1.11 150 0.94 56.0 35.9

Niagara log10 SSC = 0.729 log10 T + 0.153 1.10 73 0.83 53.8 35.0

Rock log10 SSC = 1.05 log10 T + 0.241 1.06 20 0.94 48.2 32.5

Little North log10 SSC = 1.03 log10 T + 0.195 1.12 126 0.92 61.1 37.9

Mehama log10 SSC = 0.937 log10 T + 0.152 1.15 133 0.87 72.5 42.0

Table A1. Regression model equations used at each monitoring station, North Santiam River basin, Oregon, water years 1999–2008.

[Station reference: Complete station names are shown in table 1 and locations are shown in figure 1. N, number of samples; R2, coefficient of determination; 

MSPE, model standard percent error; SSC, suspended-sediment concentration; T, turbidity]

Appendix A. Regression Models for Relation of Turbidity and SuspendedSediment Concentration in the North Santiam River Basin

As explained in section “Data Analysis”, the regression models required annual updating and verification. Bragg and 

others (2007) developed a single model for each monitoring station with samples collected during water years 1999–2004 to 

estimate suspended-sediment concentration from turbidity for those 5 years. The newly published method for updating the 

regression models (Rasmussen and others, 2009) involved adding the samples collected during each subsequent water year to 

the model calibration dataset and repeating the regression analysis with the new dataset. If the new model showed no significant 

change from the old model, the new model was used to estimate the continuous SSC record for the most recent water year. The 

regression models used at each monitoring station for each water year that suspended-sediment loads were computed are shown 

in table A1.
22 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

Station reference Regression model equation

Bias 

correction 

factor

N R2 Upper 

MSPE

Lower 

MSPE

Water year 2007

North Santiam (Precipitation-driven) log10 SSC = 1.12 log10 T + 0.222 1.12 148 0.94 60.6 37.7

North Santiam (Meltwater-driven) log10 SSC = 0.898 log10 T + 0.0772 1.03 40 0.95 28.8 22.4

Breitenbush log10 SSC = 1.07 log10 T + 0.213 1.09 115 0.96 50.0 33.3

Blowout log10 SSC = 1.09 log10 T + 0.138 1.10 165 0.95 54.4 35.2

Niagara log10 SSC = 0.737 log10 T + 0.150 1.10 76 0.84 53.7 35.0

Rock log10 SSC = 1.05 log10 T + 0.241 1.06 25 0.95 43.8 30.5

Little North log10 SSC = 1.03 log10 T + 0.196 1.12 129 0.92 60.3 37.6

Mehama log10 SSC = 0.943 log10 T + 0.148 1.14 136 0.88 71.8 41.8

Water year 2008

North Santiam (Precipitation-driven) log10 SSC = 1.12 log10 T + 0.224 1.12 151 0.95 60.0 37.5

North Santiam (Meltwater-driven) log10 SSC = 0.898 log10 T + 0.0772 1.03 40 0.95 28.8 22.4

Breitenbush log10 SSC = 1.06 log10 T + 0.215 1.09 119 0.96 50.7 33.6

Blowout log10 SSC = 1.09 log10 T + 0.140 1.10 169 0.95 54.7 35.3

Niagara log10 SSC = 0.727 log10 T + 0.163 1.10 78 0.84 54.1 35.1

Rock log10 SSC = 1.05 log10 T + 0.243 1.06 27 0.94 45.3 31.2

Little North log10 SSC = 1.02 log10 T + 0.209 1.12 131 0.92 60.9 37.8

Mehama log10 SSC = 0.931 log10 T + 0.164 1.15 137 0.87 73.2 42.2

Table A1. Regression models used at each monitoring station in the study, North Santiam River basin, Oregon.—Continued

[Station reference: Complete station names are shown in table 1 and locations are shown in figure 1. N, number of samples; R2, coefficient of determination; 

MSPE, model standard percent error; SSC, suspended-sediment concentration; T, turbidity]
Appendix B 23

Date

and Time

Streamflow

(ft3

/s)

Turbidity

(FNU)

SSC

(mg/L)

Method of SSC 

estimation or computation

SSQ

(tons/30min)

11/6/2006 0:00 1,650 23 31 Point sample 2.9

11/6/2006 0:30 1,630 27 24 Meltwater-driven regression 2.2

11/6/2006 1:00 1,610 92 71 Meltwater-driven regression 6.5

11/6/2006 1:30 1,640 940 575 Meltwater-driven regression 53

11/6/2006 2:00 1,600 4,970 2,510 Point sample 225.7

11/6/2006 2:30 1,580 5,980 3,000 Point sample 266.4

11/6/2006 3:00 1,570 5,630 3,080 Point sample 271.8

11/6/2006 3:30 1,550 5,220 2,860 Interpolation 249.1

11/6/2006 4:00 1,550 4,820 2,640 Interpolation 230

11/6/2006 4:30 1,550 4,410 2,430 Interpolation 211.7

11/6/2006 5:00 1,540 4,000 2,210 Interpolation 191.3

11/6/2006 5:30 1,530 3,590 1,990 Interpolation 171.1

11/6/2006 6:00 1,510 3,180 1,780 Interpolation 151.1

11/6/2006 6:30 1,520 2,770 1,560 Interpolation 133.3

11/6/2006 7:00 1,520 2,370 1,340 Interpolation 114.5

11/6/2006 7:30 1,510 1,960 1,120 Interpolation 95

11/6/2006 8:00 1,510 1,550 901 Meltwater-driven regression 76.5

11/6/2006 8:30 1,530 1,500 875 Meltwater-driven regression 75.2

11/6/2006 9:00 1,490 1,570 912 Meltwater-driven regression 76.3

11/6/2006 9:30 1,510 8,160 4,850 Interpolation 411.6

11/6/2006 10:00 1,490 14,700 8,790 Interpolation 736.1

11/6/2006 10:30 1,470 21,300 12,700 Interpolation 1,049.2

11/6/2006 11:00 1,490 27,900 16,700 Interpolation 1,398.4

11/6/2006 11:30 1,480 34,500 20,600 Point sample, Extrapolation 1,713.4

11/6/2006 12:00 1,470 26,500 17,800 Point sample 1,470.5

11/6/2006 12:30 1,430 21,800 15,500 EWI Sample 1,245.7

11/6/2006 13:00 1,400 18,200 14,200 Point sample 1,117.3

11/6/2006 13:30 1,360 13,700 10,900 Interpolation 833.1

11/6/2006 14:00 1,350 9,160 7,640 Point sample 579.6

11/6/2006 14:30 1,320 6,920 6,140 Interpolation 455.5

11/6/2006 15:00 1,300 4,680 4,640 Point sample 339

Table B1. Computations of suspended-sediment concentration at North Santiam (14178000), North Santiam River basin, 

Oregon, November 6-7, 2006.

[Station reference: Complete station name is in table 1 and location is in figure 1. SSC, suspended-sediment concentration; SSQ, suspended-sediment 

discharge; ft3/s, cubic foot per second; FNU, Formazin Nephelometric Unit; mg/L, milligrams per liter; min, minute]

Appendix B. Computation of Suspended-Sediment Concentration at North 

Santiam, November 6–7, 2006

The Mount Jefferson debris flow resulted in extremely elevated turbidity and suspended-sediment concentration (SSC) 

at North Santiam on November 6–7, 2006. When the recorded turbidity remained constant at the upper limit of the sensor 

range (about 1,600 FNU), the samples collected at the monitoring station provided the SSC data needed to estimate the 

suspended‐sediment load. The continuous SSC record was completed during these 2 days using a combination of sample SSC, 

turbidity-estimated SSC, and interpolation.
24 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

Date

and Time

Streamflow

(ft3

/s)

Turbidity

(FNU)

SSC

(mg/L)

Method of SSC 

estimation or computation

SSQ

(tons/30min)

11/6/2006 15:30 1,290 3,300 3,570 EWI Sample 258.8

11/6/2006 16:00 1,270 2,750 3,320 Point sample 237

11/6/2006 16:30 1,260 1,570 3,080 Interpolation 218.1

11/6/2006 17:00 1,250 730 2,840 Interpolation 199.5

11/6/2006 17:30 1,240 1,320 2,600 Interpolation 181.2

11/6/2006 18:00 1,230 1,090 2,360 Point sample 163.1

11/6/2006 18:30 1,240 1,040 2,270 Interpolation 158.2

11/6/2006 19:00 1,240 890 2,180 Interpolation 151.9

11/6/2006 19:30 1,250 890 2,080 Interpolation 146.1

11/6/2006 20:00 1,270 730 1,990 Point sample 142

11/6/2006 20:30 1,280 740 1,920 Interpolation 138.1

11/6/2006 21:00 1,300 650 1,840 Interpolation 134.4

11/6/2006 21:30 1,340 650 1,760 Interpolation 132.5

11/6/2006 22:00 1,390 580 1,690 Point sample 132

11/6/2006 22:30 1,460 580 1,860 Interpolation 152.6

11/6/2006 23:00 1,520 680 2,040 Interpolation 174.3

11/6/2006 23:30 1,570 760 2,220 Interpolation 195.9

11/7/2006 0:00 1,640 710 2,390 Point sample 220.3

11/7/2006 0:30 1,680 800 2,750 Interpolation 259.6

11/7/2006 1:00 1,750 910 3,100 Interpolation 304.9

11/7/2006 1:30 1,830 1,240 3,460 Interpolation 355.8

11/7/2006 2:00 1,960 1,530 3,820 Point sample 420.8

11/7/2006 2:30 2,100 1,290 3,980 Interpolation 469.7

11/7/2006 3:00 2,280 1,080 4,140 Point sample 530.5

11/7/2006 3:30 2,550 1,560 4,540 Interpolation 650.6

11/7/2006 4:00 2,790 1,170 4,940 Point sample 774.6

11/7/2006 4:30 3,000 1,610 5,530 Interpolation 932.4

11/7/2006 5:00 3,150 3,190 6,120 Point sample 1,083.4

11/7/2006 5:30 3,280 1,620 5,180 Interpolation 954.9

11/7/2006 6:00 3,400 1,380 4,250 Point sample 812.1

11/7/2006 6:30 3,570 1,210 4,120 Interpolation 826.6

11/7/2006 7:00 3,780 1,110 4,000 Point sample 849.7

11/7/2006 7:30 3,930 980 3,820 Interpolation 843.7

11/7/2006 8:00 4,180 890 3,630 Point sample 852.7

11/7/2006 8:30 4,350 1,080 3,460 EWI Sample 845.9

11/7/2006 9:00 4,590 1,400 3,520 Point sample 908

11/7/2006 9:30 4,860 920 3,881 Precipitation-driven regression 1,060.1

11/7/2006 10:00 5,090 880 3,693 Precipitation-driven regression 1,056.3

Table B1. Computations of suspended-sediment concentration at North Santiam (14178000), North Santiam River basin, 

Oregon, November 6-7, 2006.—Continued

[Station reference: Complete station name is in table 1 and location is in figure 1. SSC, suspended-sediment concentration; SSQ, suspended-sediment 

discharge; ft3/s, cubic foot per second; FNU, Formazin Nephelometric Unit; mg/L, milligrams per liter; min, minute]
Appendix B 25

Date

and Time

Streamflow

(ft3

/s)

Turbidity

(FNU)

SSC

(mg/L)

Method of SSC 

estimation or computation

SSQ

(tons/30min)

11/7/2006 10:30 5,310 910 3,834 Precipitation-driven regression 1,144.1

11/7/2006 11:00 5,570 1,100 4,741 Precipitation-driven regression 1,484.1

11/7/2006 11:30 5,850 1,410 6,261 Precipitation-driven regression 2,058.4

11/7/2006 12:00 6,040 1,540 6,911 Precipitation-driven regression 2,345.9

11/7/2006 12:30 6,300 1,150 4,983 Precipitation-driven regression 1,764.3

11/7/2006 13:00 6,450 1,070 4,596 Precipitation-driven regression 1,666.2

11/7/2006 13:30 6,590 990 4,213 Precipitation-driven regression 1,560.4

11/7/2006 14:00 6,720 910 3,834 Precipitation-driven regression 1,447.9

11/7/2006 14:30 6,800 880 3,693 Precipitation-driven regression 1,411.2

11/7/2006 15:00 6,870 940 3,976 Precipitation-driven regression 1,535

11/7/2006 15:30 6,820 760 3,133 Precipitation-driven regression 1,201

11/7/2006 16:00 6,770 690 2,812 Precipitation-driven regression 1,069.9

11/7/2006 16:30 6,670 640 2,585 Precipitation-driven regression 968.9

11/7/2006 17:00 6,620 600 2,405 Precipitation-driven regression 894.6

11/7/2006 17:30 6,520 510 2,004 Precipitation-driven regression 734.5

11/7/2006 18:00 6,450 420 1,613 Precipitation-driven regression 584.6

11/7/2006 18:30 6,350 360 1,357 Precipitation-driven regression 484.3

11/7/2006 19:00 6,300 370 1,399 Precipitation-driven regression 495.4

11/7/2006 19:30 6,300 380 1,442 Precipitation-driven regression 510.4

11/7/2006 20:00 6,200 310 1,148 Precipitation-driven regression 399.9

11/7/2006 20:30 6,080 340 1,273 Precipitation-driven regression 434.9

11/7/2006 21:00 5,970 340 1,273 Precipitation-driven regression 427.1

11/7/2006 21:30 5,900 300 1,106 Precipitation-driven regression 366.8

11/7/2006 22:00 5,730 290 1,065 Precipitation-driven regression 343

11/7/2006 22:30 5,600 280 1,024 Precipitation-driven regression 322.3

11/7/2006 23:00 5,480 300 1,106 Precipitation-driven regression 340.7

11/7/2006 23:30 5,370 290 1,065 Precipitation-driven regression 321.4

11/8/2006 0:00 5,240 220 782 Precipitation-driven regression 230.2

Table B1. Computations of suspended-sediment concentration at North Santiam (14178000), North Santiam River basin, 

Oregon, November 6-7, 2006.—Continued

[Station reference: Complete station name is in table 1 and location is in figure 1. SSC, suspended-sediment concentration; SSQ, suspended-sediment 

discharge; ft3/s, cubic foot per second; FNU, Formazin Nephelometric Unit; mg/L, milligrams per liter; min, minute]
26 Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08

This page intentionally left blank.
Publishing support provided by the U.S. Geological Survey

Publishing Network, Tacoma Publishing Service Center

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

 Director, Oregon Water Science Center

U.S. Geological Survey

2130 SW 5th Avenue

Portland, Oregon 97201

http://or.water.usgs.gov
Bragg and others— Suspended-Sediment Budget for the North Santiam River Basin, Oregon, Water Years 2005–08—Scientific Investigations Report 2010–5038