Analysis of Geomorphic and Hydrologic Characteristics of 

Mount Jefferson Debris Flow, Oregon, November 6, 2006

Scientific Investigations Report 2008–5204

Prepared in cooperation with the City of Salem, Oregon

U.S. Department of the Interior

U.S. Geological Survey
Front Cover: Photograph showing view of Mount Jefferson, Oregon, with the Milk 

Creek channel in forefront. Debris-flow deposit visible in light gray down center 

channel and into forest. (Photograph by Robert Ross, Linn Benton Community College, 

2007.)

Back cover: Photograph showing newly deposited material (light gray) in the Milk 

Creek drainage basin, Mount Jefferson debris flow, Oregon, November 6, 2006. 

(Photograph by Robert Ross, Linn Benton Community College, 2007.)
Analysis of Geomorphic and Hydrologic 

Characteristics of Mount Jefferson Debris 

Flow, Oregon, November 6, 2006

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

Prepared in cooperation with the City of Salem, Oregon

Scientific Investigations Report 2008–5204

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: 2008

For product and ordering information:

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS

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

natural hazards, and the environment:

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS

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:

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 Scientific 

Investigations Report 2008–5204, 18 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Description of Study Area ...................................................................................................................4

Mount Jefferson Debris Flow, November 6, 2006.....................................................................................4

Weather Conditions..............................................................................................................................4

First Detection .......................................................................................................................................6

Geomorphic and Hydrologic Characteristics............................................................................................9

Source Area...........................................................................................................................................9

Streamflow and Flooding...................................................................................................................10

Velocity .................................................................................................................................................11

Depositional Extent.............................................................................................................................12

Depositional Volume...........................................................................................................................16

Suspended-Sediment Load...............................................................................................................16

Summary and Conclusions.........................................................................................................................17

Acknowledgments.......................................................................................................................................17

References Cited..........................................................................................................................................17

Figures

Figure 1. Graph showing peak-event turbidity values at North Santiam water-quality

monitoring station, Oregon, water years 1999–2007 .................................... 2

Figure 2. Map showing location of Mount Jefferson and surrounding area, Oregon. ......... 3

Figure 3. Map showing location of the Milk Creek and Pamelia Creek drainage basins,

and Mount Jefferson debris-flow deposit, Oregon .................................... 5

Figure 4. Graph showing streamflow and measured and estimated turbidity from

samples collected at the North Santiam water-quality monitoring station,

Oregon, November 6, 2006.................................................................. 7

Figure 5. Photograph showing automatic pumping samples collected at North Santiam

water-quality monitoring station during the Mount Jefferson debris flow,

Oregon, November 6, 2006.................................................................. 8

Figure 6. Photograph showing streamflow from Pamelia Creek entering the North Santiam 

River, Oregon, November 6, 2006 ......................................................... 8

Figure 7. Photograph showing view of debris covered snowfield in the Milk Creek

channel, some of which collapsed and melted, supplying material for the

Mount Jefferson debris flow, Oregon, November 6, 2006 .............................. 9
iv

Tables

Table 1. Air temperature and precipitation data collected from meteorological

stations at Marion Forks and Santiam Junction near Mount Jefferson,

Oregon, November 1–8, 2006............................................................... 4

Table 2. Measurements of mud run-up heights on trees and calculations of indirect

debris-flow velocity for Mount Jefferson debris flow, Oregon, November 6,

2006 .......................................................................................... 6

Table 3. Estimated depositional volumes using cross-sectional transect

measurements along depositional extent of the Mount Jefferson debris flow,

Oregon, November 6, 2006.................................................................. 16

Figure 8. Photograph showing channel incision along Milk Creek, where debris flow

gained volume during the Mount Jefferson debris flow, Oregon, November 6,

2006. Note people for scale ............................................................... 10

Figure 9. Photograph showing mud run-up markings on trees created by flooding

associated with the Mount Jefferson debris flow, Oregon, November 6,

2006 .......................................................................................... 11

Figure 10. Photograph showing change in height of mud run-up markings created by

debris flow and flooding impacting tree during the Mount Jefferson debris flow, 

Oregon, November 6, 2006.................................................................. 12

Figure 11. Photograph showing tree damage caused by the Mount Jefferson debris

flow, Oregon, November 6, 2006 ......................................................... 13

Figure 12. Photograph showing downstream view of boulder-sized debris blocking the

divergence between Milk Creek and 2 percent Milk Creek,

Oregon. Note person for scale ............................................................ 13

Figure 13. Comparison of aerial photographs from 2005 and 2007 of

Mount Jefferson debris flow, Oregon, November 6, 2006 .............................. 14

Figure 14. Map showing depositional extent of the Mount Jefferson debris flow,

Oregon, November 6, 2006.................................................................. 15

Figures—Continued
v

Conversion Factors and Datums

Conversion Factors

Multiply By To obtain

centimeter (cm) 0.3940 inch (in.)

cubic feet per second (ft3/s) 0.02832 cubic meter per second (m3/s)

cubic meter (m3) 1.308 cubic yard (yd3)

kilometer (km) 0.6214 mile (m)

liter (L) 0.2642 gallon (gal)

meter (m) 3.281 foot (ft)

meter per second (m/s) 2.237 mile per hour (mph)

metric ton 1.102 Short ton [U.S.]

square kilometer (km2) 247.1 acre

square kilometer (km2) 0.3861 square mile (mi2)

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

°F=(1.8×°C)+32.

Datums

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

(NGVD 1929). 

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

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

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, 2006, through September 30, 

2007, is designated water year 2007.
vi

This page intentionally left blank
Analysis of Geomorphic and Hydrologic Characteristics of 

Mount Jefferson Debris Flow, Oregon, November 6, 2006

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

Abstract

On November 6, 2006, a rocky debris flow surged off the 

western slopes of Mount Jefferson into the drainage basins of 

Milk and Pamelia Creeks in Oregon. This debris flow was not 

a singular event, but rather a series of surges of both debris 

and flooding throughout the day. The event began during 

a severe storm that brought warm temperatures and heavy 

rainfall to the Pacific Northwest. Precipitation measurements 

near Mount Jefferson at Marion Forks and Santiam Junction 

showed that more than 16.1 centimeters of precipitation fell 

the week leading up to the event, including an additional 

20.1 centimeters falling during the 2 days afterward. The 

flooding associated with the debris flow sent an estimated 

15,500 to 21,000 metric tons, or 9,800 to 13,000 cubic meters, 

of suspended sediment downstream, increasing turbidity in 

the North Santiam River above Detroit Lake to an estimated 

35,000 to 55,000 Formazin Nephelometric Units. The debris 

flow started small as rock and ice calved off an upper valley 

snowfield, but added volume as it eroded weakly consolidated 

deposits from previous debris flows, pyroclastic flows, and 

glacial moraines. Mud run-up markings on trees indicated 

that the flood stage of this event reached depths of at least 

2.4 meters. Velocity calculations indicate that different surges 

of debris flow and flooding reached 3.9 meters per second. 

The debris flow reworked and deposited material ranging in 

size from sand to coarse boulders over a 0.1 square kilometer 

area, while flooding and scouring as much as 0.45 square 

kilometer. Based on cross-sectional transect measurements 

recreating pre-event topography and other field measurements, 

the total volume of the deposit ranged from 100,000 to 

240,000 cubic meters.

Introduction

Every year, winter storms cause tens to hundreds of 

debris flows in the Pacific Northwest (Beaulieu and Olmstead, 

1999; Hofmeister, 2000; National Park Service, 2007; Pirot 

and others, 2007; Burns and others, 2008; Scott Burns, 

Portland State University, oral commun., 2008). This number 

increases significantly during years of heavy rainfall and 

flooding, when thousands of debris flows may be observed. 

For example, during the floods of 1996 and 1997, more 

than 9,500 debris flows, or rapidly moving landslides, were 

mapped in Oregon alone (Hofmeister, 2000). Landslide 

activity in Oregon is so common that the Oregon Department 

of Forestry administers a debris flow warning system. This 

system issues warnings through the National Weather Service 

whenever conditions are deemed unsafe along or beneath 

certain steep hillsides, such as during heavy rainfall or after 

rapid snowmelt (Oregon Department of Geology and Mineral 

Industries, 2008). Although debris flows are dangerous, most 

are small, travel short distances, and occur in remote regions; 

however, sometimes they impact populated areas and damage 

infrastructure.

Although debris flows are common in Oregon and the 

Pacific Northwest, there is limited research investigating 

the relation between debris flows and downstream waterquality characteristics, such as turbidity. Where such research 

does exist, the discussion about turbidity usually focuses 

only on whether the debris flow influenced-streamflow 

is hyperconcentrated, not the effect the turbid water has 

downstream. Because of the adverse effects that turbidity 

can have on drinking-water operations, further investigation 

into the relation between landslides and turbidity is needed, 

especially in environments where debris flows occur 

proximate to reservoirs and other drinking-water sources. 

One such environment where landslide hazards coincide with 

hydrologic concerns is in the North Santiam River basin. 

After the flooding and landslide damage of 1996 and 1997, 

the U.S. Geological Survey (USGS) in cooperation with the 

City of Salem, established a continuous near real-time waterquality monitoring network in the basin (Uhrich and Bragg, 

2003). This network allows the USGS to monitor temperature, 

specific conductance, pH, turbidity, and streamflow at 

10 water-quality monitoring stations (U.S. Geological Survey, 

2008). Using this continuous, near real-time network, the 

USGS and others have detected several high turbidity events 

and traced them to various sources, including debris flows, 

earthflows, and road failures (Sobieszczyk and others, 2007).
2 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

The largest recorded high-turbidity event for the 

North Santiam River, through December 2007, occurred 

November 6, 2006 (fig. 1), at the North Santiam water-quality 

monitoring station (14178000; fig. 2). After tracing the turbid 

water to its source tributary, Pamelia Creek, the USGS and the 

U.S. Forest Service (USFS) concluded that the turbid water 

resulted from a debris flow that mobilized off the western 

slope of Mount Jefferson. Debris and sediment from this event 

were carried down Milk Creek into Pamelia Creek and finally 

to the North Santiam River and Detroit Lake. In addition to the 

suspended sediment transported downstream, a large volume 

of material was reworked and deposited in the drainage 

basins of Milk and Pamelia Creeks. Temporary storage of 

this recently deposited, highly erodible material likely will 

increase turbidity during future high streamflow events.

Purpose and Scope

This report describes the geomorphology of the Mount 

Jefferson debris flow that occurred on November 6, 2006, and 

its effect on the downstream turbidity and suspended-sediment 

load in the North Santiam River. This event represents one of 

the few examples where water-quality data, such as turbidity, 

directly relates to a known sediment source, such as a debris 

flow (Sobieszczyk and others, 2007). Data and measurements 

for this event were quantified by a combination of field survey 

data, precipitation data, water-quality data, remote sensing 

data, and aerial photography. Turbidity values referenced in 

this report were recorded as part of the USGS North Santiam 

River Basin Suspended-Sediment and Turbidity Study 

monitoring network (http://or.water.usgs.gov/santiam/).

Figure 1. Peak-event turbidity values at North Santiam water-quality monitoring station, Oregon, water years 1999–2007.

200 740

3,520

1,030 190

5,550

70 420

55,000

1999 2000 2001 2002 2003 2004 2005 2006 2007

WATER YEAR

Range of

turbidity

estimate

35,000

North Santiam Station (14178000)

0

10,000

20,000

30,000

40,000

50,000

60,000

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS (FNU)
Introduction 3

Figure 2. Location of Mount Jefferson and surrounding area, Oregon.

tac08-0256_fig. 02

"

US

20

US

20

SR

22

SR

22

122°10' 122°5' 122° 121°55' 121°50'

44°45'

44°40'

44°35'

44°30'

44°25'

Base map modified from U.S. Geological Survey digital data (1:24,000).

UTM projection, Zone 10

Horizontal datum: North American Datum of 1927

EXPLANATION

Meteorological station

Milk Creek 

Pamelia Creek 

Wilderness Area

Boundary of drainage basin

Water-quality monitoring station 

14178000

14178000

OREGON

Study Area

0 1 2 3 4 5 10 Kilometers

0 1 2 3 4 5 Miles

North Santiam River

Santiam Junction

Willamette

National

Forest

Detroit

Lake Mount

Jefferson

Pamelia

Lake

Milk Creek

MARION CO.

JEFFERSON CO.

Location of 

figure 3

Pamelia Creek

LINN CO.

Marion Forks
4 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Description of Study Area

Mount Jefferson with an altitude of 3,200 m is the second 

tallest Western Cascade volcano in Oregon. The mountain 

and its accompanying wilderness area are about 100 km east 

of Salem, Oregon. Similar to most volcanic environments, 

there are multiple hazards associated with the mountain that 

potentially endanger people and property. Beyond the remote 

hazard of a large explosive volcanic eruption (last occurring 

more than 35,000 years ago; Walder and others, 1999) or 

basaltic lava flows (last occurring more than 7,600 years 

ago; Walder and others, 1999), other more likely hazards 

include landslides and snow avalanches. Although stable 

bedrock limits deep-seated landslides, the steep slopes and 

unconsolidated glacial moraine and pyroclastic flow deposits 

are susceptible to rock falls and debris flows. For example, 

at least two debris flows have mobilized from the western 

slopes of Mount Jefferson down the Milk and Pamelia Creek 

drainage basins prior to 2006 (Sobieszczyk and others, 2007). 

There also are accounts of debris flow activity in the Milk 

Creek drainage basin in the 1990s (David Halemeier, U.S. 

Forest Service, oral commun., 2008).

 Milk and Pamelia Creek drainage basins are located 

on the western flank of Mount Jefferson, within the Mount 

Jefferson Wilderness Area (fig. 3). Pamelia Creek drains 

63 km2, conveying a large portion of the runoff from the 

western slope of Mount Jefferson. Milk Creek is within 

the Pamelia Creek drainage basin and drains 6.5 km2, with 

flows originating from remnants of the Milk Creek Glacier, 

high-altitude valley snowfields, and ground water. Although 

the upper drainage basins are above treeline, the western 

lower altitude portions are densely vegetated with western 

white pine, western hemlock, Douglas-fir, silver fir, and 

rhododendrons in the understory (U.S. Forest Service, 2007; 

David Halemeier, U.S. Forest Service, oral commun., 2008). 

Vehicle access within the drainage basins is limited, but a 

large part of the Mount Jefferson Wilderness Area is accessible 

by trail, such as the Pamelia Lake and Pacific Crest Trails.

Mount Jefferson Debris Flow, 

November 6, 2006

Weather Conditions

Early November 2006 was a warmer than normal period 

accompanied by a tropical storm which brought heavy 

precipitation (table 1). Air temperatures near Mount Jefferson 

increased quickly as the storm front moved across the Pacific 

Northwest. During the first week of November, maximum 

daily air temperatures increased 9.4°C, and minimum daily air 

temperatures increased 21.1°C. The warm front brought heavy 

precipitation to the region, peaking with a total of 12.8 cm on 

November 7. These weather conditions were characteristic 

of a “Pineapple Express,” where central Pacific tropical 

air streams over the Northwestern United States (National 

Oceanic and Atmospheric Administration, 2005). This storm 

was responsible for flooding and numerous landslides all over 

the region, such as those on Mount Rainier (National Park 

Service, 2007) and Mount Hood (Pirot and others, 2007). 

Similar conditions occurred in February 1996 and led to the 

worst flooding in more than 30 years for much of the Pacific 

Northwest.

Because the warm temperatures and rainfall occurred 

early in the winter, the mountain had minimal snowpack. 

A small amount of snow accumulated during November 1 

and 2, especially at higher altitudes; however, as the warm air 

temperatures caused the snow level to rise, rain fell directly 

onto higher altitude snowfields. This “rain-on-snow” situation 

augmented the heavy rainfall conditions from November 3 

through 6 by adding additional water to the hydrologic system.

Table 1. Air temperature and precipitation data collected from 

meteorological stations at Marion Forks and Santiam Junction 

near Mount Jefferson, Oregon, November 1–8, 2006.

[Temperature and precipitation data from Oregon Climate Service (2007). 

Shading indicates period of debris flow. Maximum values are in bold italics. 

Abbreviations: °C, degrees Celsius; cm, centimeter]

Date

Maximum daily 

air temperature 

(°C)

Minimum daily 

air temperature 

(°C)

Precipitation 

(cm)

11/01/2006 5.0 -11.1 0

11/02/2006 5.6 -1.7 0.2–0.3

11/03/2006 7.8 1.1 2.6–4.9

11/04/2006 8.3 5.6 3.4–3.5

11/05/2006 11.7 7.8 6.4–7.4

11/06/2006 14.4 10.0 2.0–3.2

11/07/2006 12.2 -1.1 6.1–12.8

11/08/2006 3.3 -1.1 5.7–7.3
Mount Jefferson Debris Flow, November 6, 2006 

5

tac08-0256_fig. 03 EXPLANATION

Pamelia CreekMilk CreekRoadsTrails

Debris-flow deposit

Wilderness Area

Milk Creek

Pamelia

Lake

MountJefferson

Pamelia Creek

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

P

a

c

i

f

i

c

C

rest

Trail

0 1 2 KILOMETERS0 1 2 MILES

Pamelia Lake Trail

Boundary of drainage basin

121°48' 121°49' 121°50' 121°51' 121°52' 121°53' 121°54'

44°

41'

44°

40'

44°

39'

Location figure14

Figure 3. Location of the Milk Creek and Pamelia Creek drainage basins, and Mount Jefferson debris-flow deposit, Oregon.
6 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Table 2. Measurements of mud run-up heights on trees and calculations of indirect debris-flow velocity for Mount Jefferson debris 

flow, Oregon, November 6, 2006.

[Indirect debris flow velocity: Velocity was determined by an equation proposed by Chow (1959). Shading indicates values used in indirect velocity equation. 

Altitude is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 1929). Abbreviations: m, meter; m/s, meter per second; –, no data]

Tree and index 

No. for mud runup measurements 

(see fig. 14)

Latitude 

(decimal 

degrees)

Longitude 

(decimal 

degrees)

Altitude

(m)

Flow 

depth 

(m)

Tree

diameter 

(m)

Change in height 

of mud run-up (m)

Indirect debrisflow velocity 

(m/s)

Geomorphic 

location

1 44.659 -121.872 1,094 0.2 0.5 0.0 0.0 valley floor

2 44.659 -121.872 1,092 0.1 0.3 0.1 1.2 valley floor

3 44.659 -121.871 1,091 0.5 0.6 0.1 1.3 valley floor

4 44.660 -121.866 1,124 0.2 0.0 0.1 1.3 valley floor

5 44.660 -121.871 1,092 0.4 0.4 0.2 1.7 valley floor

6 44.659 -121.872 1,092 0.5 0.6 0.2 1.7 valley floor

7 44.659 -121.868 1,108 1.2 0.0 0.2 1.7 confined channel

8 44.659 -121.870 1,074 0.9 0.8 0.2 1.7 confined channel

9 44.659 -121.871 1,096 1.1 0.6 0.2 2.1 valley floor

10 44.660 -121.869 1,102 0.6 0.4 0.3 2.4 valley floor

11 44.660 -121.868 1,113 1.2 0.3 0.3 2.4 valley floor

12 44.659 -121.871 1,092 0.6 0.6 0.3 2.4 valley floor

13 44.660 -121.864 1,138 1.4 1.1 0.3 2.4 confined channel

14 44.660 -121.866 1,131 2.4 0.8 0.6 3.5 confined channel

15 44.659 -121.879 – 1.5 0.9 0.6 3.5 valley floor

16 44.659 -121.877 – 1.7 0.6 0.6 3.5 valley floor

17 44.661 -121.865 1,138 1.8 1.1 0.7 3.7 confined channel

18 44.661 -121.865 1,178 1.8 0.6 0.7 3.7 confined channel

19 44.661 -121.861 1,170 2.4 0.5 0.8 3.9 confined channel

20 44.661 -121.862 1,180 2.4 0.5 0.8 3.9 confined channel

21 44.660 -121.865 1,138 2.4 0.8 0.8 3.9 confined channel

22 44.659 -121.869 1,106 1.1 0.9 0.8 3.9 valley floor

First Detection

During the storm, streamflow increased and became 

more turbid in most streams in the North Santiam River 

basin. Unlike other streams, however, the turbidity peaked 

on the North Santiam River at the North Santiam station 

on November 6, a full day before the peak rainfall and 

streamflow occurred elsewhere (table 2, fig. 4). The timing, 

magnitude, and location of the high turbidity event were 

immediately recognized as a possible debris flow or glacial 

outwash event, similar to major turbidity events from previous 

years (Sobieszczyk and others, 2007). Because turbidity was 

so high, it exceeded the maximum detection capability of the 

instream water-quality instrumentation; however, estimates 

from samples collected (fig. 5) during the event indicate that 

turbidity in the North Santiam River ranged from 35,000 to 

55,000 FNU (Heather Bragg, U.S. Geological Survey, written 

commun., 2008).
Mount Jefferson Debris Flow, November 6, 2006 7

08-0256_Figure 04

North Santiam Water-Quality Monitoring Station (14178000)

0

5 6 7 8

10,000

NOVEMBER 2006

20,000

30,000

40,000

50,000

60,000

70,000

TURBIDITY, IN FORMAZIN NEPHELOMETRIC UNITS (FNU)

80,000

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

STREAMFLOW, IN CUBIC FEET PER SECOND

8,000

55,000 FNU

35,000 FNU

Sample set A Sample set B

Sample

Turbidity (measured)

Turbidity (estimated)

Streamflow

Figure 4. Streamflow and measured and estimated turbidity from samples collected at the North Santiam waterquality monitoring station, Oregon, November 6, 2006. Sample sets A and B correspond to water-quality samples 

collected by automatic pumping sampler (see figure 5).

Turbidity values for this event were based on a series of 

samples collected by an ISCO automatic pumping sampler. 

The first set of 1-L sample bottles (sample set A) were filled 

during the start of the event and replaced with a second set 

of bottles (sample set B) that captured the latter part of the 

high turbidity (fig. 5). Laboratory measurements from these 

samples supplied a conservative turbidity value for the event, 

whereas the peak turbidity was estimated between the sets 

based on trends in other water-quality parameters, such as pH 

and conductivity, collected from the North Santiam monitoring 

station.

Tracing the source of turbid water in the North Santiam 

River was facilitated by the fact that the tributary Pamelia 

Creek, about 10 mi upstream of the monitoring station, 

was visibly turbid (fig. 6). USGS and USFS personnel 

investigating Pamelia Creek discovered that a debris flow had 

mobilized down the Milk Creek drainage basin, supplying 

debris and sediment to both Milk and Pamelia Creeks and 

beyond. Streamflow at Milk and Pamelia Creeks remained 

extremely turbid for 12 to 18 hours during the debris flow 

event-period on November 6.
8 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Figure 5. Automatic pumping samples collected at North Santiam water-quality monitoring station during the Mount Jefferson 

debris flow, Oregon, November 6, 2006. (Photograph by Heather Bragg, U.S. Geological Survey, 2007.) Gap between sample sets A 

and B occurred during bottle replacement.

Figure 6. Streamflow from Pamelia Creek entering the North Santiam River, Oregon, November 6, 

2006. (Photograph by David Klug, U.S. Forest Service, November 6, 2006.)
Geomorphic and Hydrologic Characteristics 9

Geomorphic and Hydrologic 

Characteristics

Source Area

Historic and prehistoric debris-flow deposits have been 

found on all Cascade Range volcanoes, where unconsolidated 

volcaniclastic and glacial moraine deposits are washed away 

from the steep slopes (Scott and others, 1995). These unstable 

volcaniclastic and glacial deposits can be mobilized by any 

number of causes including an increase in seasonal meltwater discharge or saturation by autumn or spring rainfall. 

Other less common mechanisms for Cascade debris flows 

include dam-break floods, volcanic eruptions, or possibly 

earthquakes; however, these are much more low-frequency, 

high-consequence type mechanisms. The debris flow on 

November 6, 2006, appeared to be caused by a combination 

of mechanisms. Although rainfall influenced the debris flow, 

noticeable changes in high altitude Milk Creek snowfields, as 

observed by USFS and USGS, indicated that the debris flow 

likely mobilized after the collapse of part of a talus-covered 

stagnant valley snowfield (fig. 7). This type of proglacial 

collapse and flooding occurred during previous times and 

at other Cascade volcanoes (for example, Scott and others, 

1995; Walder and others, 1999; O’Connor and others, 2001). 

Although the rainfall may not have initiated the debris flow, 

it did increase melting of surficial snow, amplified runoff, 

saturated sediments, and augmented subsnowfield streamflow. 

Snowfield calving and sediment unloading likely started 

relatively small, but continued to accumulate and erode more 

material as it progressed downstream (fig. 8). Because of the 

presence of older debris flow deposits in the area, much of the 

loose, previously deposited material was easily remobilized by 

this recent event.

Figure 7. View of debris covered snowfield in the Milk Creek channel, some of which collapsed and melted, supplying material for 

the Mount Jefferson debris flow, Oregon, November 6, 2006. (Photograph by William Myers, Oregon State University, 2007.)

Debris covered

snowfield

Debris covered

snowfield

Collapsed

snowfield

Collapsed

snowfield

Milk Creek Milk Creek
10 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Streamflow and Flooding

The fluvial component of the debris flow that formed 

down the Milk Creek drainage basin was characteristic of a 

hyperconcentrated flow, or mud slurry. However, streamflow 

from Pamelia Creek likely diluted much of the mud slurry 

prior to its entering the North Santiam River. Analyses of 

water samples collected at the North Santiam monitoring 

station correlated with estimates of streamflow from Milk 

and Pamelia Creeks indicate that 3 to 6 percent of the flow 

volume consisted of entrained sediments (Mark Uhrich, U.S. 

Geological Survey, written commun., 2008). Streamflow is 

considered to be hyperconcentrated when 5 percent of the 

flow volume consists of entrained sediments (Pierson, 2005). 

Evidence of mud run-up on trees (fig. 9) indicated that the 

flood stage of this flow reached depths of at least 2.4 m in the 

confined, high altitude channels (table 2). As the flow spread 

across the valley floor, tree markings displayed a reduction 

in stage height to 1 m or less. High flows associated with 

flooding remobilized boulders and debris along Milk and 

Pamelia Creeks, as well as deposited sand and silt across 

the forest floor. Flooding and high flows eroded portions 

of the initial debris-flow deposit and other older deposits, 

reworking much of the landscape. As velocities decreased, 

greater volumes of fine-grained sediment were deposited 

within distributary channels along the Milk and Pamelia Creek 

drainage basins. After the debris flow slowed and deposited 

its coarse material, the sediment-laden streamflow continued 

to the North Santiam River and Detroit Lake. This type of 

debris-flow-induced flood surge was consistent with previous 

events on other Cascade volcanoes (see, for example, Scott 

and others, 1995; Pierson, 2005; National Park Service, 2007).

Figure 8. Channel incision along Milk Creek, where debris flow gained volume during the Mount Jefferson debris flow, 

Oregon, November 6, 2006. Note people for scale. (Photograph by Mark Uhrich, U.S. Geological Survey, 2007.)
Geomorphic and Hydrologic Characteristics 11

Figure 9. Mud run-up markings on trees created by flooding associated with the Mount Jefferson debris flow, Oregon, 

November 6, 2006. (Photograph by Mark Uhrich, U.S. Geological Survey, 2007.)

Velocity

The Mount Jefferson debris flow in November 2006 was 

not a single flow event, but rather a series of at least three 

or more surges of debris and flooding (David Halemeier, 

U.S. Forest Service, written commun., 2008). Evidence 

of damming and redirection of flow, channel terracing, 

and deposition then scouring of material all support this 

hypothesis. Because this event comprised multiple flows, 

calculating one specific velocity was impossible. Instead, 

using field measurements of change in height of mud run-up 

on trees (fig. 10) and observations of material type, an indirect 

velocity equation (Jakob, 2005) was used to calculate a 

range of values for this event. For this study, mud run-up 

markings for 22 trees were measured at different locations in 

the depositional area (table 2). The deposit material type was 

initially coarse and boulder-sized before thinning to a mud 

slurry. Based on these observations, velocity was determined 

by an equation for “rocky”-type debris flows proposed by 

Chow (1959). The equation describes debris flow velocity 

in relation to the change in run-up height multiplied by a 

multiple of the gravitational constant (Chow, 1959, eq. 1). 

Two known limitations for this equation are (1) it only applies 

to impacted objects perpendicular to the flow direction, and 

(2) it assumes all kinetic energy was converted to potential 

energy (Jakob, 2005). Theoretical run-up equations, such as 

equation 1 in Chow (1959), also yield velocities as much as 

30 percent lower than large-scale flume experiments (Jakob, 

2005). However, given the data available, these velocity 

calculations offered tangible values for discussion and 

comparison.

v g h

v

g

= ( ) , . 2 0 5 Δ

where

is velocity,

is the gravitational mass acceleration constant

9.8 m/s , and

is the change in run-u

2

Δh p height, in meters.

(1)

Velocities calculated using this equation reached 3.9 m/s 

for the different surges of debris and flooding (table 2).
12 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Depositional Extent

The debris-flow depositional extent was determined 

based on field indicators, such as distal flow levees, log jams 

and boulder clusters, mud coatings on trees and boulders, 

organic debris accumulations, and tree scars (fig. 11; 

O’Connor and others, 2001; Pierson, 2005). Mapping the 

depositional extent of the Mount Jefferson debris flow in 

November 2006 was completed between July 2007 and 

July 2008. A Global Positioning System (GPS) handheld 

device was used to record coordinates for the outermost edge 

of the coarse debris flow boundary, and the coordinates were 

cross-referenced against aerial photography to verify accuracy.

The debris flow deposited a predominantly rocky debris 

fan, including large boulders greater than 0.4 m diameter, 

over a 0.1 km2 area in the drainage basins of Milk and 

Pamelia Creeks (fig. 12). The material dammed Milk Creek 

and redirected its flow south to a newly formed channel 

referred by the USFS as “2 percent Milk Creek.” Most of 

Figure 10. Change in height of mud run-up markings created by debris flow and flooding impacting tree (left to right) during the 

Mount Jefferson debris flow, Oregon, November 6, 2006. (Photograph by Mark Uhrich, U.S. Geological Survey, 2007.)

the coarse material from the debris flow in November 2006 

was deposited along 2 percent Milk Creek (fig. 13). As 

material was deposited, multiple dams and levees were 

formed, continuously altering the direction and velocity of the 

debris flow. Surges of debris and flooding further altered the 

landscape in the drainage basins of Milk and Pamelia Creeks 

by reworking and depositing fine to coarse-grained material 

along an additional 0.35 km2 area (fig. 14). High flows in 

Pamelia Creek also contributed to the damage caused by the 

debris flow. Increased streamflow and flooding during this 

period forced Pamelia Creek about 100 m south to an abandon 

section of its original channel. The combined 0.45-km2 area 

represented the depositional extent, including subsequent 

flooding and deposition of fine-grained material along a 

number of other channels. All coarse material settled out 

before the original confluence of Milk and Pamelia Creeks, 

leaving only the mud slurry to pass downstream into the North 

Santiam River.
Geomorphic and Hydrologic Characteristics 13

Figure 11. Tree damage caused by the Mount Jefferson debris flow, Oregon, November 6, 2006. (Photograph by Mark Uhrich, 

U.S. Geological Survey, 2007.) Diagram shows example of indicators of damage to vegetation during a debris flow (Pierson, 

2005).

2 Percent

Milk Creek

Milk Creek

Figure 12. Downstream view of boulder-sized debris blocking the divergence between Milk Creek (right) and 2 percent Milk Creek 

(left), Oregon. Note person for scale. (Photograph by Chris Ricker, Portland State University, 2007.)
14 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Figure 13. Comparison of aerial photographs from 2005 (top) and 2007 (bottom) of Mount Jefferson debris flow, Oregon, 

November 6, 2006. 2005 aerial photograph from Oregon State University (2008); 2007 aerial photograph by Robert Ross, 

Linn Benton Community College (2007). Note that the new deposit (light gray) extends from center-right toward bottom 

left along newly formed 2 percent Milk Creek.

tac08-0256__Fig13

Milk Creek

Milk Creek

2 percent

Milk Creek
Geomorphic and Hydrologic Characteristics 15

tac08-0256_fig14

121°51'30" 121°52' 121°52'30" 121°53'

44°40'

44°39'30"

0 0.5 Kilometers

0 0.5 Miles

EXPLANATION

Predominantly coarse debris-flow depositsPredominantly fine hyperconcentrated-flow depositsCoarse to fine flood deposits

Historic coarse debris-flow depositsPrehistoric glacial and debris-flow deposits

Cross-sectional transects

Tree mud run-up measurements 9

Stream

Dry Channel

G

6

8

7

4

2 1

5

22

21

19

18 17

16

15

14

20

12

10

11

13

9

A

B C D E F G

H

I

J

Creek

Milk Creek 2%

Creek

Milk

3

Pamelia

Pamelia Lake

Base map modified from U.S. Geological Survey digital data (1:24,000). Projection: UTM, Zone 10, North American Datum 1927.

Figure 14. Depositional extent of the Mount Jefferson debris flow, Oregon, November 6, 2006.
16 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

Depositional Volume

The depositional volume of the Mount Jefferson debris 

flow in November 2006 was estimated using cross-sectional 

transect measurements (table 3; fig. 14). For this study, crosssectional areas were surveyed using a laser distance meter 

and survey staff, and angles and leveling were obtained using 

a Brunton compass. Using 10 transects (table 3) surveyed 

along the length of the predominantly coarse debris deposit, 

deposit values were extrapolated between cross-sectional 

areas to produce a generalized volume. Because each transect 

consisted of deposit and scour, volume measurements were 

based on the net deposit (total deposit – scour = net deposit). 

Results indicated that at least 80,000 m3 of coarse material was 

freshly deposited during the November 2006 debris flow. Field 

measurements of fine-grained sediment deposits extrapolated 

over the debris-flow area indicate that the hyperconcentrated 

flow and floodwaters contributed an additional 20,000 to 

160,000 m3 of sediment, increasing the total depositional 

volume to 240,000 m3, not including the suspended sediment 

that was carried downstream. For comparison, nearly 100 

Olympic-sized swimming pools could have been filled with 

boulders, debris, and sediment from this debris-flow event.

Table 3. Estimated depositional volumes using cross-sectional transect measurements along depositional extent of the Mount 

Jefferson debris flow, Oregon, November 6, 2006.

[Location of cross-sectional transect profiles are shown in figure 14. Abbreviations: m, meter; m2, square meter; m3, cubic meter]

Transect 

index 

letter 

Mean height

(deposit)

(m)

Mean depth 

(scour) 

(m)

Net deposit 

(deposit – scour) 

(m)

Transect 

area 

(m2)

Transect depositional 

volume

(net deposit × area) 

(m3)

A 0.0 3.0 -3.0 2,000 -6,000

B 3.0 2.0 1.0 1,000 1,000

C 2.0 3.0 -1.0 2,000 -2,000

D 2.0 2.0 0.0 3,000 0

E 3.0 2.0 1.0 5,000 5,000

F 4.0 2.0 2.0 2,000 4,000

G 4.0 2.0 2.0 6,000 12,000

H 3.0 2.0 1.0 6,000 6,000

I 2.0 1.0 1.0 10,000 10,000

J 2.0 1.0 1.0 50,000 50,000

Coarse deposits 80,000

Fine deposits 20,000–160,000

Total 100,000–240,000

 

Suspended-Sediment Load

Although water quality was not monitored on Milk 

or Pamelia Creeks, automatic pumping samples collected 

at the North Santiam monitoring station were analyzed for 

turbidity and suspended-sediment concentrations. Using these 

samples, suspended-sediment load values were calculated 

for the debris flow and subsequent flooding. Estimates were 

based on techniques developed by Uhrich and Bragg (2003) 

and Bragg and others (2007). During the 24-hour period on 

November 6, 2006, about 15,500 to 21,000 metric tons of 

suspended sediment traveled downstream past the North 

Santiam monitoring station. If the dry weight per volume of 

the suspended sediment was assumed to be sand-sized or less, 

then the total volume for the suspended-sediment load portion 

of the debris flow was 9,800 to 13,000 m3. Even though other 

sources may have contributed minor amounts of sediment, 

most of the suspended-sediment load was attributed to the 

Mount Jefferson debris flow. This event was responsible for 

one of the largest single-day suspended-sediment loads of any 

major turbidity event in the North Santiam River basin since 

1998 (Sobieszczyk and others, 2007).
References Cited 17

Summary and Conclusions

Each winter, landslides mobilize from slopes throughout 

the Pacific Northwest. If winter storms produce above average 

rainfall, the threat for rapidly moving landslides increases 

substantially. As landslides enter streams, they greatly affect 

downstream water quality by causing large and sudden 

increases in turbidity. This study analyzes one such example 

where turbidity data exist for a known rapidly moving 

landslide, or debris flow.

On November 6, 2006, a rocky debris flow surged down 

the western flank of Mount Jefferson in the Oregon Cascades. 

Although coarse, boulder-sized material settled near the 

base of the mountain, high flows and flooding continued 

through parts of the drainage basins of Milk and Pamelia 

Creeks, sending a mud slurry into the North Santiam River. 

Investigation into the source of the event suggested that 

warmer than normal air temperatures and heavy precipitation 

caused a portion of a debris-covered, stagnant snowfield to 

collapse in the upper Milk Creek valley. As boulders, ice, and 

water flowed downslope, additional material was aggregated 

from previous debris flows, pyroclastic flows, and glacial 

moraine deposits. Mud run-up markings on trees indicated that 

the confined channel flood stage was greater than 2.4 meters 

deep, while flows outside the channel gradually thinned out 

atop the open valley floor. Fine-grained sediments entrained in 

floodwaters were transported through the North Santiam River 

into Detroit Lake. Future high flows will continue to erode 

the fine-grained material remaining on boulders, logs, and the 

valley floor. 

Velocity calculations for the debris-flow event suggest 

that the multiple waves of debris and water that surged 

throughout the day reached 3.9 meters per second. Analyses 

of water-quality samples collected during the event indicated 

that an estimated 9,800 to 13,000 cubic meters of fine-grained 

sediment was transported downstream to the North Santiam 

River. A follow-up investigation of the debris flow indicated 

that debris and flood deposits covered about 0.45 square 

kilometers, depositing between 100,000 and 240,000 cubic 

meters of material. The debris flow altered the landscape by 

diverting streamflow from its original channel south to a new 

channel that was carved into the forest floor. This debris flow 

supplied enough suspended sediment to increase turbidity 

values in the North Santiam River above Detroit Lake to an 

estimated 35,000 and 55,000 Formazin Nephelometric Units. 

These turbidity values rank among the highest recorded 

(or estimated) in the North Santiam River basin since the 

inception of the USGS North Santiam River Basin SuspendedSediment and Turbidity Study monitoring network in 1998.

Acknowledgments

The authors would like to thank the City of Salem for 

cooperative funding. In addition, we thank Carolyn Driedger, 

Kevin Schmidt, Jim O’Connor, Richard Iverson, Joseph 

Rinella, and John Williams of the U.S. Geological Survey 

for their comments and review. We also would like to thank 

Scott Burns, Bethany Jackson, and Chris Ricker of Portland 

State University for their help during the inception of this 

research. Lastly, we could not have completed this report 

without the help of Robert Ross of Linn Benton Community 

College, William Myer of Oregon State University, and David 

Halemeier and David Klug of the U.S. Forest Service. Their 

guidance and support were invaluable.

References Cited

Beaulieu, J.D., and Olmstead, D.L., 1999, Mitigating geologic 

hazards in Oregon—A technical reference manual: Oregon 

Department of Geology and Mineral Industries Special 

Paper 31, 60 p.

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.

Burns, Bill, Hinkle, Jason, and Hay, Stephen, 2008, The 

Woodson debris flow, Woodson, Oregon: Association of 

Environmental & Engineering Geologists News, v. 51, 

no. 1, p. 21–24.

Chow, V.T., 1959, Open channel hydraulics: New York, 

McGraw Hill, 680 p.

Hofmeister, R.J., 2000, Slope failures in Oregon, GIS 

inventory for three 1996/97 storm events: Oregon 

Department of Geology and Mineral Industries Special 

Paper 34, 20 p., 1 compact disc.

Jakob, Matthias, 2005, Debris-flow hazard analysis, Chapter 

17, in, Jakob, Matthias., and Hungr, Oldrich., eds., Debrisflow hazards and related phenomena: New York, SpringerPraxis Books in Geophysical Sciences, p. 411-443.

National Oceanic and Atmospheric Administration, 2005, 

NOAA catches a culprit behind western storms: accessed 

November 2007, at http://www.noaanews.noaa.gov/

stories2005/s2367.htm.
18 Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006

National Park Service, 2007, November 2006 Flooding: 

accessed July 2008, at http://www.nps.gov/mora/parknews/

november-2006-flooding.htm

O’Connor, J.E., Hardison, J.H., and Costa, J.E., 2001, Debris 

flows from failures of Neoglacial-age moraine dams in 

the Three Sisters and Mount Jefferson Wilderness Areas, 

Oregon: U.S. Geological Survey Professional Paper 1606, 

93 p., 2 pls.

Oregon Climate Service, 2007, Climate data: Zone 4/

Temperature: Daily/Santiam Junction and Zone 4/

Precipitation: Daily/Santiam Junction, Marion Forks 

Fish Hatchery, and Detroit Dam—Climate data archives: 

accessed November 2007, at http://www.ocs.oregonstate.

edu/index.html

Oregon Department of Geology and Mineral Industries, 2008, 

Debris flow warnings—Oregon’s debris flow warning 

system and how it works: accessed August 2008, at http://

www.oregongeology.com/sub/Landslide/debrisflow.htm

Oregon State University, 2008, Oregon imagery explorer: 

accessed June 2008, at http://oregonexplorer.info/imagery

Pierson, T.C., 2005, Distinguishing between debris flows 

and floods from field evidence in small watersheds: U.S. 

Geological Survey Fact Sheet 2004–3142, 4 p.

Pirot, Rachel, Burns, Scott, and Deroo, Thomas, 2007, 

Massive debris flow generation on Mount Hood, Oregon, 

November 2006: Geological Society of America, Abstracts 

with Programs, v. 39, no. 6, p. 363.

Scott, K.M., Vallance, J.W., and Pringle, P.T., 1995, 

Sedimentology, behavior, and hazards of debris flows 

at Mount Rainer, Washington: U.S. Geological Survey 

Professional Paper 1547, 56 p.

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

Major turbidity events in the North Santiam River Basin, 

Oregon, water years 1999–2004: U.S. Geological Survey 

Scientific Investigations Report 2007–5178, 50 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 WaterResources Investigations Report 03–4098, 43 p.

U.S. Forest Service, 2007, Mt. Jefferson Wilderness: accessed 

November 2007, at http://www.fs.fed.us/r6/willamette/

recreation/tripplanning/wilderness/mtjefferson.html

U.S. Geological Survey, 2008, North Santiam River Basin 

suspended-sediment and turbidity study—Near real-time 

data for sites in the North Santiam River Basin: accessed 

June 1998, at http://or.water.usgs.gov/santiam/datapage.html

Walder, J.S., Gardner, C.A., Conrey, R.M., Fisher, B.J., 

and Schilling, S.P., 1999, Volcano hazards in the Mount 

Jefferson region, Oregon: U.S. Geological Survey OpenFile Report 99–24, 14 p.
Manuscript approved for publication, October 22, 2008

Prepared by the USGS Publishing Network

Bill Gibbs 

Linda Rogers

Luis Menoyo

Sharon Wahlstrom

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 98402

http://or.water.usgs.gov
Sobieszczyk and others— Geomorphic and Hydrologic Characteristics of Mount Jefferson Debris Flow, Oregon, November 6, 2006—Scientific Investigations Report 2008–5204