U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2014–5223

Prepared in cooperation with the University of Oregon and the U.S. Fish and Wildlife Service

Geomorphology and Flood-Plain Vegetation of the 

Sprague and Lower Sycan Rivers, Klamath Basin, Oregon
Cover: Council Butte valley segment looking upstream from near flood-plain 

kilometer 59.2, Sprague River Basin, Oregon. Photograph taken by J.E. O’Connor, 

U.S. Geological Survey, September 16, 2006.
Geomorphology and Flood-Plain 

Vegetation of the Sprague and Lower 

Sycan Rivers, Klamath Basin, Oregon

By Jim E. O’Connor, Patricia F. McDowell, Pollyanna Lind, 

Christine G. Rasmussen, and Mackenzie K. Keith

Prepared in cooperation with the University of Oregon and the

U.S. Fish and Wildlife Service

Scientific Investigations Report 2014–5223

U.S. Department of the Interior

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

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director 

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation:

O’Connor, J.E., McDowell, P.F., Lind, Pollyanna, Rasmussen, C.G., and Keith, M.K., 2015, Geomorphology and floodplain vegetation of the Sprague and lower Sycan Rivers, Klamath Basin, Oregon: U.S. Geological Survey Scientific 

Investigations Report 2014–5223, 122 p., 1 pl., http://dx.doi.org/10.3133/sir20145223.

ISSN 2328-0328 (online)
iii

Contents

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

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

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

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

Units of Measurement and Key Locations .......................................................................................4

Sprague River Basin......................................................................................................................................4

Geography and Geology ......................................................................................................................4

Climate and Hydrology.........................................................................................................................6

Vegetation ..............................................................................................................................................8

Historical Human Influences and Land Use.....................................................................................8

Study Area, Methods, and Data Sources ..................................................................................................9

Study Area..............................................................................................................................................9

Geomorphic Mapping...........................................................................................................................9

Stratigraphic Studies ...........................................................................................................................9

Historical Observations and Photographs......................................................................................11

Nineteenth-Century Cadastral Surveys ..........................................................................................11

Aerial Photographs.............................................................................................................................11

Lidar Topography ................................................................................................................................14

Survey of Effects of 2006 High Flows...............................................................................................14

Mapping and GIS Analysis Framework...........................................................................................14

Geomorphic Mapping and Geologic History...........................................................................................15

Geomorphic Units ...............................................................................................................................15

Undifferentiated Bedrock.........................................................................................................15

Landslide Deposits.....................................................................................................................15

Colluvial Slopes..........................................................................................................................15

Abandoned Fans ........................................................................................................................15

Active Tributary Fans.................................................................................................................16

Terraces.......................................................................................................................................16

Sycan Flood Deposits................................................................................................................16

Active Tributary Flood Plain .....................................................................................................26

Main-Stem Valley Fill.................................................................................................................26

Pond and Wetland Deposits.....................................................................................................26

Active Springs and Spring Deposits.......................................................................................26

Geomorphic Flood Plain............................................................................................................26

Synopsis of Quaternary Geologic History and Sprague River Geomorphology.......................30

Valley Segments...........................................................................................................................................32

Chiloquin Canyon ................................................................................................................................32

Braymill.................................................................................................................................................36

Kamkaun Spring..................................................................................................................................36

S′Ocholis Canyon................................................................................................................................37

Buttes of the Gods ..............................................................................................................................38

Council Butte .......................................................................................................................................38
iv

Contents—Continued

Valley Segments—Continued

Beatty-Sycan.......................................................................................................................................39

Beatty Gap............................................................................................................................................40

Upper Valley.........................................................................................................................................42

South Fork ............................................................................................................................................42

North Fork.............................................................................................................................................43

Lower Sycan........................................................................................................................................44

Coyote Bucket .....................................................................................................................................45

Channel and Flood-Plain Conditions and Processes.............................................................................45

Historical Modification.......................................................................................................................46

Early Observations of Flood-Plain and Channel Conditions ...............................................46

Ditches, Dams, Levees, Field Leveling, and Roads ..............................................................47

Channel Rehabilitation and Remeandering...........................................................................49

Channel Planform—Spatial and Temporal Trends........................................................................49

Channel Pattern .........................................................................................................................49

Channel Width............................................................................................................................50

Analysis of Channel Width from General Land Office Surveys.................................50

Analysis of Channel Width from Aerial Photographs .................................................56

Bars .........................................................................................................................................56

Channel Migration ..............................................................................................................................56

Observations from Stratigraphy and Morphology................................................................58

Centerline Analysis....................................................................................................................59

Channel Cutoffs and Avulsions................................................................................................59

Channel Incision..................................................................................................................................62

Stratigraphic Analysis...............................................................................................................62

Channel Centerline Altitude Changes ....................................................................................64

Effects of the 2006 High Flows..........................................................................................................66

Distribution and Character of Flood Deposits.......................................................................66

Measured Sediment Transport................................................................................................70

Channel and Flood-Plain Processes................................................................................................73

Channel Processes....................................................................................................................73

Sediment Transport ..........................................................................................................73

Bar Building .......................................................................................................................74

Bank Erosion......................................................................................................................75

Incision ...............................................................................................................................76

Channel Substrate ............................................................................................................76

Flood-Plain Processes ..............................................................................................................77

Meander Growth...............................................................................................................77

Cutoff and Avulsion Processes.......................................................................................78

Flood-Plain Building ........................................................................................................79

Geologic Controls and Legacy.................................................................................................80

Human Influences......................................................................................................................80

Channel and Flood-Plain Manipulation.........................................................................80
v

Contents—Continued

Channel and Flood-Plain Conditions and Processes—Continued

Channel and Flood-Plain Processes—Continued

Human Influences—Continued

Grazing Management.......................................................................................................82

Other Historical Activities ...............................................................................................82

Summary of Physical Flood-Plain and Channel Conditions, Processes, and Trends..............83

Flood-Plain and Riparian Vegetation ........................................................................................................86

Overview of Current Flood-Plain Vegetation..................................................................................86

Historical Flood-Plain Vegetation Conditions.................................................................................87

Vegetation Conditions Inferred from GLO Surveys and Notes...........................................87

Historical Notes from Botanist William E. Lawrence .........................................................87

Aerial Photograph Analysis ..............................................................................................................89

Vegetation Mapping and Analysis ..........................................................................................89

Spatial Distribution of Vegetation in Year 2000 .....................................................................90

Vegetation Trends, 1940–2000..................................................................................................90

Vegetation Transitions...............................................................................................................95

Major Vegetation Changes and Their Causes ...............................................................................99

Transitions Among Water, Bare, and Herbaceous Cover Classes ....................................99

Short Woody Vegetation.........................................................................................................101

Tall Woody Vegetation ............................................................................................................101

Summary of Flood-Plain and Near-Channel Vegetation Conditions.........................................102

Implications for Restoration and Monitoring ........................................................................................102

Status and Trends .............................................................................................................................102

Spatial and Temporal Scales ..........................................................................................................107

Key Process Regimes.......................................................................................................................108

Restoration Objectives.....................................................................................................................109

Monitoring Approaches...................................................................................................................110

Summary and Significant Findings .........................................................................................................110

Acknowledgments.....................................................................................................................................113

References Cited........................................................................................................................................113

Appendixes .................................................................................................................................................121

Appendix A. Locations of Stratigraphic Analysis, Sprague River Study Area, Oregon.......121

Appendix B. Radiocarbon Analyses, Sprague River Study Area, Oregon .............................121

Appendix C. Volcanic Glass Compositions of Tephra, Sprague River Study Area, 

Oregon ..................................................................................................................................121

Appendix D. Cesium-137 Content, Sprague River Study Area, Oregon..................................121

Appendix E. Geomorphic Map Units, Sprague River Study Area, Oregon.............................121

Appendix F. Comparison of General Land Office Section-Line Measurements of River 

Width with Width from 2000 Aerial Photographs, Sprague River Study Area, 

Oregon...................................................................................................................................121

Appendix G. Survey Sites of Effects of 2006 High Flows, Sprague River Study Area, 

Oregon...................................................................................................................................121

Appendix H. Vegetation Transitions in the Geomorphic Flood Plain and Near-Channel 

Areas for 1940–1968 and 1968–2000, Sprague River Study Area, Oregon .................121
vi

Plate

1. Geomorphic surfaces of the Sprague and Lower Sycan Rivers, Oregon.

Figures

1. Map showing valley segments in the study area, selected locations, and 

streamflow-gaging stations, Sprague River Basin, south-central Oregon.........................3

2. Graphs showing annual peak discharge for streamflow-gaging stations at 

Sprague River near Chiloquin, station 11501000; Sycan River below Snake Creek 

near Beatty, station 11499100; and Sprague River near Beatty, station 11497500, 

Sprague River Basin, Oregon .....................................................................................................7

3. Graph showing mean daily discharge for selected streamflow-gaging stations,

Sprague River Basin, Oregon .....................................................................................................8

4. Stratigraphic sections showing Late Quaternary exposures at flood-plain kilometer

(FK) 55.0, FK 79.4, FK 87.6, and Sycan flood-plain kilometer 2.5, Sprague River study

area, Oregon................................................................................................................................17

5. Stratigraphic sections of Sycan River flood-plain kilometers (SYFK) 0.02 and 0.1;

SYFK 1.6 and 1.7; SYFK 3.5; SYFK 6.8 and 7.3; and SYFK 10.1, 10.3, and 10.6, Sprague

River study area, Oregon...........................................................................................................18

6. Graph showing flood-plain and terrace surface profiles estimated from

stratigraphic sections and observations along lower Sycan River, Sprague River

study area, Oregon .....................................................................................................................23

7. Photographs showing pumiceous sand deposits of the Sycan flood about 7,700

calendar years before present at exposed site 7/2/05-1, Sycan River flood-plain

kilometer (SYFK) 10.1 (July 2, 2005); and site 9/12/06-2, SYFK 6.1 (June 20, 2006),

lower Sycan River valley segment, Sprague River study area, Oregon ...........................23

8. Stratigraphic sections of flood-plain kilometer (FK) 26.3, FK 82.4, FK 87.7, and FK 98.5, 

along main-stem and South Fork Sprague River geomorphic flood plain, Oregon .........24

9. Stratigraphic sections of North Fork Sprague River flood-plain kilometer (NFFK) 0.7,

and NFFK 1.2, along North Fork Sprague River geomorphic flood plain, Oregon............25

10. Photograph showing Mazama fallout tephra and Sycan flood deposits exposed at

site 7/24/07-2/3, Sycan River flood-plain kilometer (SYFK) 0.02, Sprague River study

area, Oregon................................................................................................................................26

11. Stratigraphic diagram and photograph showing late Holocene inset flood-plain

deposits at the right-bank exposure at North Fork Sprague River flood-plain

kilometer (NFFK) 0.7, and left-bank exposure at NFFK 0.9, along North Fork Sprague

River, Oregon ...............................................................................................................................27

12. Cross sections and map showing former paleochannel locations and augering

transects between flood-plain kilometers (FK) 48.2 and 49.0, Buttes of the Gods

valley segment, Sprague River study area, Oregon..............................................................28

13. Map and graph showing former paleochannel locations and augering transects

between flood-plain kilometers (FK) 30.6 and 32.0, Kamkaun Spring valley segment,

Sprague River study area, Oregon...........................................................................................29

14. Diagram showing stratigraphic relation among flood-plain and terrace deposits in

Lower Sycan valley segment, Sycan River flood-plain kilometer 3.5, Sprague River

study area, Oregon .....................................................................................................................30

15. Photographs showing point bar deposits at survey site 6/23/06-5 with view

downstream of partly vegetated point bar mantled with coarse sand deposited

during 2006 high flows, and 30-centimeter-deep excavation into 2006 high flow

deposits showing bedded coarse sand composed mainly of pumice grains, Upper

Valley segment, Sprague River study area, Oregon .............................................................31
vii

Figures—Continued

16. Graph showing geomorphic units within 10 meters of primary channel edge for

channel location during 2000, Sprague River Basin, Oregon..............................................32

17. Graphs showing spatial trends in flood-plain altitude, flood-plain width, and

channel sinuosity , Sprague River Basin, Oregon.................................................................33

18. Graphs showing spatial trends in channel water-surface altitude, channel width,

and bar width, Sprague River Basin, Oregon.........................................................................34

19. Photographs showing Chiloquin Canyon valley segment with view downstream of

bridge crossing at flood-plain kilometer (FK) 8.8, and view upstream across pool

behind the decommissioned Chiloquin Dam at FK 1.3, Sprague River Basin, Oregon....35

20. Historical photographs associated with discontinued U.S. Geological Survey

(USGS) streamflow-gaging station 11502000 at flood-plain kilometer (FK) 0.7, with

view upstream from former wagon bridge crossing of the Sprague River at FK 0.7

(May 2 (?), 1918; view downstream from near USGS gaging station (May 6, 1918);

bridge visible in upper right of image); and view of USGS gage house on right bank

of Sprague River near Chiloquin, Oregon ...............................................................................35

21. Photograph showing Braymill valley segment looking southwest from near

flood-plain kilometer 14.5, Sprague River Basin, Oregon ....................................................36

22. Photograph showing Kamkaun Spring valley segment at flood-plain kilometer 26.8,

Sprague River Basin, Oregon ...................................................................................................36

23. Photograph showing filled cutoff channel at flood-plain kilometer 25.3, Kamkaun

Spring valley segment, Sprague River Basin, Oregon..........................................................37

24. Photograph showing S’Ocholis Canyon valley segment at flood-plain kilometer 34.1,

Sprague River Basin, Oregon ...................................................................................................37

25. Photograph showing Buttes of the Gods valley segment looking upstream from

flood-plain kilometer 49.2, Sprague River Basin, Oregon ....................................................38

26. Photograph showing Council Butte valley segment looking upstream from near

flood-plain kilometer 59.2, Sprague River Basin, Oregon ....................................................39

27. Photograph showing Beatty-Sycan valley segment looking northwest (upstream)

from flood-plain kilometer 78.5, Sprague River Basin, Oregon...........................................39

28. Photograph showing Beatty Gap valley segment looking west (downstream) from

flood-plain kilometer 85.2, Sprague River Basin, Oregon ....................................................41

29. Photographs showing approximately matched locations at flood-plain kilometer

81.4 near the downstream end of the Beatty Gap valley segment, Sprague River

Basin, Oregon..............................................................................................................................41

30. Photograph showing Upper Valley segment looking downstream from flood-plain

kilometer 88.5, Sprague River Basin, Oregon.........................................................................42

31. Photographs showing South Fork valley segment looking downstream from Ivory

Pine Road bridge crossing at flood-plain kilometer (FK) 94.3 (March 9, 2004); and

upstream from diversion at FK 98.6 (June 20, 2007), Sprague River Basin, Oregon........42

32. Graph showing approximate water-surface profiles from 1-meter spacing lidar data

along 2004 channel centerlines, North Fork and South Fork Sprague Rivers, Oregon...43

33. Photograph showing Lower Sycan valley segment looking downstream from Sycan

River flood-plain kilometer 10.7, Sprague River Basin, Oregon..........................................44

34. Photograph showing Sycan River flowing on Tertiary lacustrine sediment at Sycan

River flood-plain kilometer 1.2 in the Lower Sycan valley segment, Sprague River

Basin, Oregon..............................................................................................................................44

35. Photograph showing Coyote Bucket valley segment of the Sycan River looking 

downstream from near Sycan River flood-plain kilometer 13.2, Sprague River Basin, 

Oregon ..........................................................................................................................................45
viii

Figures—Continued

36. Graphs showing extent of cultural features in the flood plain, including irrigation

and drainage ditches; levees and dikes; roads; and total area covered by ditches,

levees, roads, dams, diversions, and structures, as mapped from 1940, 1968, and

2000 aerial photographs, summed by valley segment, Sprague River Basin, Oregon....48

37. Map showing flood-plain topography smoothed by field leveling between

flood-plain kilometers 91.0 and 93.0, Upper Valley segment, just downstream of

confluence of South Fork and North Fork Sprague Rivers, Sprague River Basin,

Oregon ..........................................................................................................................................49

38. Graphs showing summary plan-view channel and flood-plain characteristics,

including channel slope, channel sinuosity, primary channel area, secondary

channel area, backwater area, and bar area, as mapped from 1940, 1968, and 2000

aerial photographs, summed by valley segment, Sprague River Basin, Oregon............51

39. Graphs showing spatial trends in channel and bar features, as mapped from aerial

photographs taken in 2000, Sprague River Basin, Oregon ..................................................52

40. Vertical aerial photographs showing examples of meander cutoffs, avulsions, and

anabranches, including neck cutoff and avulsion between flood-plain kilometers

(FKs) 25.0 and 26.0, Kamkaun Spring valley segment; meander cutoffs formed along

levees between FKs 64.0 and 65.0; and anabranches spanning many meander loops

between FKs 74.0 and 77.0, Sprague River Basin, Oregon ..................................................53

41. Graphs showing General Land Office (GLO) surveyed (chiefly in 1866) widths

compared with measured widths from aerial photographs taken in 2000 for 62 GLO

surveyed widths and at the same location as determined from aerial photographs;

and relation between GLO and widths in 2000 by valley segment, Sprague River

Basin, Oregon .............................................................................................................................55

42. Graphs showing spatial trends in channel width, as mapped from aerial

photographs taken in 1940, 1968, and 2000, Sprague River Basin, Oregon.......................57

43. Boxplot showing wetted channel width measurements summarized by valley

segment, Sprague River Basin, Oregon..................................................................................58

44. Graphs showing spatial trends in lateral channel migration rate determined from

channel centerline positions, as mapped from General Land Office (GLO) maps and

aerial photographs from 1940, 1968, 1975, 2000, and 2005, Sprague River Basin,

Oregon ..........................................................................................................................................60

45. Boxplot showing channel migration rate measurements summarized by valley

segment, Sprague River Basin, Oregon..................................................................................61

46. Graphs showing migration rate correlations and confidence intervals along valley

segment summarized variables, Sprague River Basin, Oregon..........................................62

47. Map showing locations and timing of avulsions and cutoffs evident from map and

aerial photograph analysis, Sprague River Basin, Oregon..................................................63

48. Diagram showing flood-plain transect, illustrating the approach for assessing

vertical channel movement from intercepts between channel centerline positions

and 2005 lidar topography, Sprague River study area, Oregon...........................................64

49. Graphs showing spatial trends in channel-centerline altitude differences, as

mapped from 2004 (lidar) in conjunction with sequential channel centerline

positions, as mapped from General Land Office (GLO) maps and aerial photographs

taken in 1940, 1968, 1975, 2000, and 2005, Sprague River study area, Oregon..................64

50. Graph showing mean daily discharge during water year 2006 for select

streamflow-gaging stations, Sprague River Basin, Oregon................................................66
ix

Figures—Continued

51. Map showing sites assessed in the summer of 2006 for water year 2006 sediment

deposition and flood altitude, Sprague River Basin, Oregon ..............................................67

52. Graphs showing summary observations of 2006 survey of deposits and inundation

levels of water year 2006 floods, including longitudinal trends of deposits and

inundation evidence; and summary plots of 2006 flood deposit texture and altitude,

grouped by bar and flood-plain settings, main-stem Sprague River, Oregon ..................68

53. Photographs showing examples of sediment deposition resulting from the 2006

high flows, including overbank deposition of 4.5 centimeters of silt and sand on low

flood-plain surface, Council Butte valley segment; and deposition of 33 centimeters

of sand on point bar, Beatty Gap valley segment, main-stem Sprague River, Oregon ...69

54. Photograph showing Kamkaun Spring valley segment, looking north, main-stem

Sprague River, Oregon, during high flow in water year 2006 ..............................................69

55. Graphs showing discharge and suspended sediment transport between 

December 20, 2005 and January 7, 2006 period of high flows for seven locations 

in the Sprague River Basin, Oregon ........................................................................................71

56. Graphs showing longitudinal trends in discharge and suspended sediment

transport for 6 days of observations and at near-peak discharge.....................................72

57. Photographs showing examples of bank erosion with down-dropped blocks of

flood-plain deposits, including left-bank erosion in S’Ocholis Canyon valley

segment, and right-bank erosion in Kamkaun Spring valley segment, main-stem

Sprague River, Oregon...............................................................................................................75

58. Map showing channels, possibly caused by ice jams, formed on Sprague River

flood plain, Oregon .....................................................................................................................79

59. Graph showing avulsions and cutoffs, summarized by valley segment, Sprague

River Basin, Oregon....................................................................................................................81

60. Graphs showing summary trends of major flood-plain and channel attributes,

summarized by valley segment, Sprague River Basin, Oregon ..........................................84

61. Graphs showing extent of mapped cover types in the geomorphic flood plain,

summarized by valley segment, Sprague Valley Basin, Oregon.........................................92

62. Graphs showing extent of mapped cover types in the near-channel area,

summarized by valley segment, Sprague Valley Basin, Oregon.........................................94

63. Graphs showing percentage of valley segment area in which cover type changed

in entire geomorphic flood plain, and near-channel area, Sprague River Basin,

Oregon, during 1940–1968 and 1968–2000 analysis periods ................................................96

64. Graphs showing cover-type transitions for geomorphic flood plain, summarized by

valley segment, during 1940–1968, and 1968–2000, Sprague River Basin, Oregon..........97

65. Graphs showing cover-type transitions for the 40-meter-wide, near-channel zone

centered about 1940 channel centerline, summarized by valley segment, during

1940–1968, and 1968–2000, Sprague River Basin, Oregon ...................................................98

66. Graphs showing summary of seral stage trends in entire geomorphic flood plain,

and near-channel area, Sprague River Basin, Oregon, during 1940–1968 and

1968–2000 ...................................................................................................................................100

67. Photograph showing trampled sand-and-gravel point bar looking upstream near

Sycan River flood-plain kilometer 0.1 along Sycan River, Oregon ...................................100
x

Tables

1. Locations of notable features in the Sprague River study area, Oregon............................5

2. General valley segment characteristics, Sprague River Basin, Oregon...........................10

3. Early (1865–92) General Land Office surveys in the Sprague River study area, 

Oregon ..........................................................................................................................................12

4. Primary data sources for maps and aerial photographs of the Sprague River study

area, Oregon................................................................................................................................13

5. Features mapped from the 1940, 1968, and 2000 aerial photography in the

geomorphic flood plain, Sprague River study area, Oregon ...............................................14

6. Mapped built features in the Sprague River geomorphic flood plain, Oregon ................40

7. Channel width measurements from General Land Office section-line and meander

surveys, Sprague River Basin, Oregon ...................................................................................54

8. Avulsion and cutoff frequency, Sprague River Basin, Oregon............................................61

9. Vegetation notes from General Land Office surveys, by valley segment, Sprague

River Basin, Oregon....................................................................................................................88

10. Mapped cover types .................................................................................................................89

11. Cover types in valley segments of the geomorphic flood plain, Sprague Valley

Basin, Oregon..............................................................................................................................91

12. Cover types in valley segments of the near-channel area, Sprague Valley Basin,

Oregon ..........................................................................................................................................93

13. General valley segment trends and conditions, with implications for restoration,

Sprague River Basin, Oregon .................................................................................................103
xi

Conversion Factors and Datums

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

mile (mi) 1.609 kilometer (km)

Area

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd) 

kilometer (km) 0.6214 mile (mi)

Area

hectare (ha) 2.471 acre

hectare (ha) 0.003861 square mile (mi2) 

square kilometer (km2) 247.1 acre

square meter (m2) 10.76 square foot (ft2) 

square kilometer (km2) 0.3861 square mile (mi2)

Volume

cubic kilometer (km3) 0.2399 cubic mile (mi3) 

cubic meter (m3) 35.31 cubic foot (ft3)

cubic meter (m3) 0.0008107 acre-foot (acre-ft) 

Flow rate

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

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

Radioactivity

becquerel per liter (Bq/L) 27.027 picocurie per liter (pCi/L) 

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

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

Geomorphology and Flood-Plain Vegetation of the 

Sprague and Lower Sycan Rivers, Klamath Basin, Oregon 

By Jim E. O’Connor1, Patricia F. McDowell2, Pollyanna Lind2, Christine G. Rasmussen2, and Mackenzie K. Keith1

1

U.S. Geological Survey.

2

Department of Geography, University of Oregon

Abstract

This study provides information on channel and 

flood‐plain processes and historical trends to guide effective 

restoration and monitoring strategies for the Sprague River 

Basin, a primary tributary (via the lower Williamson River) 

of Upper Klamath Lake, Oregon. The study area covered 

the lower, alluvial segments of the Sprague River system, 

including the lower parts of the Sycan River, North Fork 

Sprague River, South Fork Sprague River, and the entire 

main‐stem Sprague River between the confluence of the North 

Fork Sprague and the South Fork Sprague Rivers and its 

confluence with the Williamson River at Chiloquin, Oregon. 

The study included mapping and stratigraphic analysis of 

flood-plain deposits and flanking features; evaluation of 

historical records, maps and photographs; mapping and 

analysis of flood-plain and channel characteristics (including 

morphologic and vegetation conditions); and a 2006 survey of 

depositional features left by high flows during the winter and 

spring of 2005–06.

Analyses focused on the channel and flood plain 

within an area defined as the “geomorphic flood plain,” an 

area encompassing active fluvial and riparian processes. 

The geomorphic flood plain was subdivided into 13 valley 

segments of distinct fluvial environments on the basis of 

valley form and major tributary junctions: nine segments 

span the 136.1 kilometers of main-stem Sprague River, two 

segments for the lower Sycan River, and one segment for 

each part of the South Fork Sprague and North Fork Sprague 

Rivers within the study area. Segment characteristics range 

from steep and narrow canyons to low-gradient reaches with 

expansive flood plains. The wide flood-plain valley segments 

are broadly similar; most contain a sinuous, low-gradient 

channel that migrates slowly across the valley bottom. The 

narrow valley segments include the steep, boulder-andcobble-bed reaches at downstream and upstream ends of the 

study area as well as other confined valley segments that have 

similar gradients and substrates as adjacent unconfined valley 

segments, but much lower sinuosities. Although the geologic 

setting of the expansive South Fork valley segment resulted in 

historical conditions of sinuous and poorly defined channels 

and wet meadows, flanking levees now narrowly confine the 

channelized South Fork Sprague River for much of its length.

Stratigraphic analyses show that before the Mazama 

eruption of 7,700 calendar years before present, wetlands 

and low flood plains flanked the main rivers of the study 

area. The eruption, however, covered much of the northern 

basin with sand- and granule-size pumice clasts, transforming 

channels by increasing bed-material transport and promoting 

bar formation and channel migration, particularly for the 

Sycan and North Fork Sprague Rivers, and for the Sprague 

River downstream of the Sycan River confluence. The South 

Fork Sprague River, which had much less Mazama pumice 

deposited in its watershed, remained a wet-meadow fluvial 

system until historical channelization and diking.

The analysis of historical maps and aerial photographs 

covering the geomorphic flood plain show changes in 

sinuosity, migration rates, and vegetation conditions since the 

1800s. Most quantitative information is for the period between 

1940 and 2000. The decrease in sinuosity since 1940 for nearly 

all the unconfined reaches resulted partly from decreased 

migration rates, but mostly from several cutoffs and avulsions 

formed between 1940 and 1975. The river shortening and 

steepening possibly resulted from (1) flood‐plain confinement 

by levees, dikes, roads, and railroads leading to deeper and 

faster overbank flow, thereby promoting erosion of new 

flood‐plain channels; and (2) flood‐plain disturbances such 

as trails, ditches, and vegetation manipulation or eradication 

that locally concentrated overbank flow and decreased surface 

resistance to channel erosion. 

The most evident vegetation change has been the loss 

of short woody vegetation adjacent to the river channels: 

only one-half the near-channel area covered by short woody 

vegetation in 1940 was similarly covered in 2000. Woody 

vegetation removal in the 1950s and 1960s and continuing 

grazing and trampling by livestock probably are the main 

reasons for the decrease in short woody vegetation from 

the dense riparian corridors of willows (Salix sp.) and other 

riparian shrubs noted in the early 20th century. 
2 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

The alluvial corridor of the South Fork Sprague River, 

compared to other Sprague River Basin rivers, has been 

the most substantially transformed since first historical 

observations. The present channel is incised, straightened, and 

separated from the rarely inundated flood plain by levees. 

Despite these effects of human disturbances, many of 

the fundamental physical processes forming the Sprague 

River fluvial systems over the last several thousand years 

still function. In particular, flows are unregulated, sediment 

transport processes are active, and overbank flooding allows 

for floodplain deposition and erosion. Therefore, restoration 

of many of the native physical conditions and processes is 

possible without substantial physical manipulation of current 

conditions for much of the Sprague River study area. An 

exception is the South Fork Sprague River, where historical 

trends are not likely to reverse until it attains a more natural 

channel and flood-plain geometry and the channel aggrades to 

the extent that overbank flow becomes common.

Introduction

The Sprague River Basin encompasses 4,167 square 

kilometers (km2) of south-central Oregon and is a principle 

tributary (via the Williamson River) of Upper Klamath Lake 

(fig. 1). The main-stem Sprague River, as well as the lower 

reaches of the North Fork Sprague River, the South Fork 

Sprague River, and the Sycan River meander through broad 

alluvial valleys and have historically supported agriculture and 

livestock grazing. National and regional interest in restoring 

Klamath Basin ecosystem conditions and processes has 

motivated several restoration strategies and projects in the 

Sprague River Basin to improve aquatic, riparian, and upland 

habitat conditions, particularly for endangered fish species 

(National Research Council, 2004). The goal of this study 

was to help management and regulatory agencies evaluate 

restoration proposals and to guide effective restoration and 

monitoring strategies for the Sprague River and its primary 

tributaries by summarizing the overall geomorphic setting 

and historical and current channel and flood-plain processes 

and conditions. The study was jointly conducted by the 

U.S. Geological Survey (USGS) and University of Oregon, 

in cooperation with the U.S. Fish and Wildlife Service 

Klamath Basin Ecosystem Restoration Office and the Hatfield 

Restoration Program.

Background

The Sprague and Sycan Rivers are like many rivers in the 

western United States for which issues of fish habitat, water 

quality, climate change, and land use changes have motivated 

new efforts to manage rivers and flood plains for many 

purposes. These efforts commonly aim to restore river systems 

where aquatic and riparian habitats have been degraded by 

historical land use activities, which in the Sprague River Basin 

include timber harvest, agriculture, and livestock grazing. 

A key issue for the Sprague River Basin is that it provides 

spawning and rearing habitat for two fish species listed 

under the Endangered Species Act: the Lost River (Deltistes 

luxatus) and shortnose (Chasmistes brevirostris) suckers. 

Additionally, the importance of the Sprague River and its 

tributaries in maintaining and protecting valued fish species 

is heightened by the removal in 2008 of Chiloquin Dam on 

the Sprague River 1.3 km upstream of its confluence with the 

Williamson River, and the possibility of changing or removing 

lower Klamath River dams, thus allowing reintroduction of 

anadromous salmonid species that once ranged into the basin 

(Hamilton and others, 2005). 

Water withdrawals, increased stream temperature, high 

nutrient levels, riparian livestock grazing, and channelization 

likely have affected aquatic habitat in the Sprague River 

(Boyd and others, 2002; National Research Council, 2004). 

These factors have motivated several restoration activities 

in the Sprague River Basin, including many channel and 

flood‐plain engineering projects, riparian management 

programs, and upland and flood-plain vegetation treatment 

programs (U.S. Department of Agriculture, 2009; NewFields 

River Basin Services and Kondolf, G. M., 2012). Such 

projects, however, are most likely to be successful if designed, 

implemented, and monitored with an understanding of the 

geomorphic context and recent history of the local landscape 

(Thorne and others, 1997; Kondolf and Piegay, 2003).

Purpose and Scope

The objective of this study of the Sprague River Basin 

was to provide an understanding of recent changes to the 

fluvial systems of the basin, including important physical 

processes, river and flood-plain geomorphic conditions, 

and flood-plain and near-channel vegetation. The primary 

focus of this analysis was the 136.1 kilometers (km) of the 

main-stem Sprague River, the lower 15.6 km of the North 

Fork Sprague River, the lower 14.8 km of the South Fork 

Sprague River, and the lower 30.1 km of the Sycan River. 

Collectively, this part of the river network encompasses most 

of the low-gradient reaches historically subject to agriculture 

and livestock grazing, as well as more recent channel 

restoration activities. Analyses and findings were supported 

by (1) mapping and measurement of channel and flood-plain 

features, including vegetation, from historical maps and 

aerial photographs, and from high resolution Light Detection 

and Ranging (lidar) topographic data acquired in 2004; 

(2) stratigraphic measurements and analyses of flood-plain 

deposits; (3) surveys of the effects of 2006 high flows, and 

(4) geomorphic mapping based on soils, sedimentology, and 

topography.
Introduction 3

tac14-0898_fig 01

97

97

62

140

140

140

LAKE COUNTY

KLAMATH COUNTY

Rock Creek

Spring Creek

Copperfield Creek

Trout Creek

Brown 

Creek

Sprague River

Williamson River

North Fork

Sprague River

South Fork

Sprague River

Williamson River

UPPER

KLAMATH

LAKE

Sycan

Marsh

N Fk

Ditch

Snake Cr

Sycan River

Kamkaun

Spring

Medicine

Springs

McCready

Springs

Lalo

Springs

Whitehorse

Springs

Brown

Spring

Paradise Cr

Fishhole Creek

Blue Cr

Fivemile Creek

Meryl Creek

Whisky Cr

Deming Cr Fritz Cr

11501000

11499100

11499100

11497500

Coyote

Bucket

Yainax

Butte

Sprague River

Picnic Area

Drews Rd

bridge

Saddle

Mountain

Medicine

Rock

Cave

Medicine

Mountain

Ferguson

Mountain

Ivory Pine

Road bridge

Teddy

Powers

Meadows

Godowa 

Springs

Rd bridge

FORMER SITE OF

CHILOQUIN DAM

Bly

Sprague River

Beatty

Chiloquin

Braymill

Council

Butte Beatty Gap

Sycan Canyon

Bly Mounta ni

Flood-plain kilometer

Streamflow-gaging

station

Dam

Channel centerline, 2000

Lower Sycan

Coyote Bucket

North Fork

South Fork

Chiloquin Canyon

Braymill

Kamkaun Spring

S’Ocholis Canyon

Buttes of the Gods

Council Butte

Beatty-Sycan

Beatty Gap

Upper Valley

Valley segment

EXPLANATION

Photograph site

121°45’ 121°30’ 121°15’ 121°

42°45’

42°30’

42°15’

0 5 10 20 KILOMETERS

0 5 10 20 MILES

Base map modified from U.S. Geological Survey digital data, 10-meter resolution.

Projection: UTM, Zone 10N, Datum: North American Datum of 1983 (NAD 83)

CALIFORNIA

OREGON

Klamath River Basin

Klamath River Basin

Sprague

River Basin

Map detail

85

5

0

5 10

0

95

90

85

80 75 65 70 60

55 50

45

40 35

30

25

20

10

105

100

10

5

0

15

15

20

Figure 1. Valley segments in the study area, selected locations, and streamflow-gaging stations, Sprague River Basin, southcentral Oregon.
4 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

This report describes all aspects of the study. Following 

short sections on background hydrology, physiography, and 

history of the Sprague River Basin, the overall methods and 

data sources underlying the analyses are briefly described. A 

section describing geomorphic surfaces and geologic history 

provides the basic physical framework of the study area, 

which is further elaborated in descriptions of the 13 individual 

valley segments that compose the study area. These 

descriptions are followed by the major substantive sections of 

the report: descriptions and analysis of physical flood‐plain 

conditions and processes, and flood-plain and near‐channel 

vegetation. For each of these substantive sections, the general 

progression is a description of the analyses (including 

methods) and observations, followed by more interpretative 

discussions of processes and conditions. Key findings are 

summarized at the end of both of these sections, which support 

a final section on implications for restoration and monitoring.

Units of Measurement and Key Locations

Analyses and results are in metric units. Conversions 

to English units are listed in the conversion table. Locations 

along the main-stem and South Fork Sprague River channel 

are referenced to river kilometers (RK) measured from the 

Sprague River mouth along the channel centerline mapped 

from 2000 aerial photographs. Similarly, Sycan River 

kilometers (SYRK) and North Fork Sprague River kilometers 

(NFRK) are measured from their confluences with the Sprague 

River along the 2000 channel centerline. To avoid ambiguity 

owing to channel shifting, especially for the historical 

analyses, most locations are referenced to flood-plain 

kilometers (FK; Sycan River flood-plain kilometer, SYFK; 

North Fork Sprague River flood-plain kilometer, NFFK) from 

centerlines bisecting the late Holocene flood plains for the 

Sprague River and its major tributaries (fig. 1). In 2000, the 

length of the channel of the main-stem Sprague River and its 

upstream continuation as the South Fork Sprague River was 

150.9 km within a 106.2-km-long flood plain. Similarly, the 

Sycan River within its lower alluvial reach flowed for 16.1 km 

along an 11.3 km flood plain, and the North Fork Sprague 

River meanders for 15.6 km within a 9.8-km-long flood plain.

Prominent landmarks and key locations along the 

Sprague and South Fork Sprague Rivers (table 1) include 

the former location of Chiloquin Dam (RK 1.3, FK 1.3), 

USGS streamflow-gaging station 11501000 (RK 8.8, FK 8.3), 

Braymill (RK 13.3, FK 12.6), Kamkaun Spring (RK 37.0, 

FK 30.2), the town of Sprague River (RK 79.9, FK 58.1), 

Council Butte (RK 93.2, FK 66.4), Sycan River confluence 

with Sprague River (RK 111.8, FK 76.8), Beatty (RK 113.6, 

FK 78.2), Oregon Water Resources Department (OWRD) 

streamflow-gaging station 11497500 at Beatty Gap (RK 119.5, 

FK 81.4), North Fork Sprague River confluence with Sprague 

River (RK 135.8, FK 93.2), and Bly (RK 137.3, FK 94.3). 

Just outside the study area is the Sprague River Picnic 

Area on Highway 140 (about RK 152.3, about FK 107.6). 

On the Sycan River, the Drews Road Bridge and OWRD 

streamflow‐gaging station 11499100 are at SYRK 5.2 

(SYFK 2.2), just downstream of the Snake Creek confluence 

(SYRK 5.4, SYFK 2.4). The Fivemile Creek confluence with 

the North Fork Sprague River is at NFRK 4.3 (NFFK 1.7).

Sprague River Basin

The Sprague River (fig. 1) drains 4,167 km2 of 

south-central Oregon before joining the Williamson River 

17 km upstream of the Williamson River confluence with 

Upper Klamath Lake. The Sprague River contributes about 

55 percent of the mean annual flow of the Williamson River 

at their confluence. The Sprague River begins at FK 93.2 

(RK 136.1) with the confluence of the North Fork Sprague 

River (drainage area 759 km2) and South Fork Sprague River 

(drainage area 534 km2). From there, the Sprague River 

flows through alternating wide valleys and canyon reaches 

and joins the Williamson River at the town of Chiloquin. 

Primary tributaries to the Sprague River are the Sycan River at 

FK 76.8 (drainage area 1,447 km2) and Trout Creek at FK 48.0 

(drainage area 71 km2). About one-half of the basin, including 

much of the headwaters and uplands, is within the Winema 

and Fremont National Forests. About 46 percent of the basin 

is privately owned, including much of the Sprague River 

flood plain and the lower reaches of the North Fork Sprague 

River, South Fork Sprague River, and Sycan River. In 1988, a 

95-km reach of the Sycan River was designated as a Wild and 

Scenic River to a point 20 km upstream of its Sprague River 

confluence. Furthermore, the Gearhart Mountain Wilderness 

Area (not shown in fig. 1; east of location map) includes parts 

of the South Fork (24 km2) and North Fork (44 km2) Sprague 

River headwaters. The Sprague River Basin is within Klamath 

and Lake Counties. Primary towns within the basin are 

Chiloquin, Sprague River, Beatty, and Bly.

Geography and Geology

Within the northernmost extent of the Basin and Range 

physiographic province (Fenneman, 1931), the Sprague 

River Basin spans many uplifted ranges and volcanic centers 

separated by fault-bounded valleys. The basin margin includes 

Gearhart Mountain (2,549 m) west of Winter Rim (not shown 

in fig. 1; east of location map), which separates the Sprague 

River Basin from the closed Summer Lake basin to the 

northeast (east of area shown in fig. 1), and Yamsey Mountain 

(2,498 m) to the north (north of area shown in fig. 1), dividing 

the Sprague River Basin from the upper Williamson River. The 

southern basin margin is formed by lower ranges separating 

the Sprague River Basin from those of the Lost River and 

Goose Lake (not shown in fig. 1; part of the Sacramento 

River Basin). High points along the southern basin margin 

include Saddle Mountain (2,085 m), Bly Mountain (1,789 m), 
Sprague River Basin 5

Table 1. Locations of notable features in the Sprague River study area, Oregon.

[Abbreviations: USGS, U.S. Geological Survey; OWRD, Oregon Water Resources Department; SYRK, 

Sycan river kilometer; SYFK, Sycan flood-plain kilometer; NFRK, North Fork Sprague river kilometer; 

NFFK, North Fork Sprague flood-plain kilometer]

Location

River

kilometer 

(2000)

Flood-plain 

kilometer

Sprague and South Fork Sprague Rivers

Sprague River confluence with Williamson River 0.0 0.0

Former site of Chiloquin Dam 1.3 1.3

USGS streamflow-gaging station 11501000 8.8 8.3

Chiloquin Ridge Road 9.4 8.8

Braymill 13.3 12.6

Sprague River Road bridge 16.4 15.5

Whitehorse Springs 24.8 22.0

Lalo Springs 29.9 25.5

McCready Ranch, former site of USGS streamflow-gaging 

station 11501000

34.4 28.6

Kamkaun Springs 37.0 30.2

McCready Spring 39.8 32.1

Sprague River Road bridge, S’Ocholis Canyon 44.4 34.3

Lone Pine, Saddle Mountain Pit Road bridge 52.0 40.7

Trout Creek confluence 59.8 48.0

The town of Sprague River, Sprague River Road Bridge 79.9 58.1

Council Butte 93.2 66.4

Sycan River confluence with Sprague River 111.8 76.8

Beatty, Godowa Springs Road bridge 113.6 78.2

OWRD streamflow-gaging station 11497500, Beatty Gap 119.5 81.4

Railroad bridge, entrance to Beatty Gap 118.8 80.9

North Fork Sprague River confluence with Sprague River 136.1 93.2

Bly, Ivory Pine Road bridge 137.3 94.3

Fish Hole Creek confluence 143.0 100.1

Campbell Road bridge 144.8 101.5

Sprague River picnic area1 152.3 107.6

Sycan and North Fork Sprague Rivers

Drews Road bridge; OWRD streamflow-gaging station 

11499100

SYRK 5.2 SYFK 2.2

Snake Creek confluence with Sycan River SYRK 5.4 SYFK 2.4

Fivemile Creek confluence with North Fork Sprague River NFRK 4.3 NFFK 1.7

1

Sprague River picnic area is outside the study area, locations are approximate.

Yainax Butte (2,201 m), and Fishhole Mountain (2,154 m; east 

of area shown in fig. 1). The alluvial bottomlands flanking the 

Sprague River range from the 1,268-m-altitude confluence 

with the Williamson River to about 1,350 m in the broad 

valley upstream of the North and South Fork Sprague River 

confluence. The mean altitude of the basin is 1,600 m (Risley 

and others, 2008).

The Sprague River Basin is underlain by late Tertiary 

and Quaternary volcanic and sedimentary strata locally offset 

by north- to northwest-trending normal faults (Sherrod and 

Pickthorn, 1992; Jenks, 2007). The uplands are underlain 

chiefly by upper Miocene and Pliocene basalt and basaltic 

andesite lava flows issued from local vents and shield 

volcanoes, locally overlying older and more siliceous lava 

flows and domes. One of the younger basalt flows, the Basalt 

of Knot Tableland, flowed down the paleo Sycan River 

valley, partly filling and blocking the Sprague River Valley 

3.0±0.9 million years ago (Ma; Sherrod and Pickthorn, 1992). 

Some of the prominent buttes within the Sprague River Valley, 

particularly near the town of Sprague River, are tuff cones 

formed by volcanic centers venting through lakes and wet 

lake sediment.
6 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

The broad alluvial valleys of the Sprague River are 

excavated chiefly into weakly consolidated Miocene and 

Pliocene diatomites, mudstones, sandstones, conglomerates, 

and tuffs deposited in lake basins and broad valleys bounded 

by block-faulted uplifts or lava flows. Incision of the modern 

valleys probably began with integration of the Sprague River 

drainage with a Cascade-Range-bisecting Klamath River in 

the late Pliocene (Sherrod and Pickthorn, 1992). The present 

river winds westward through the fault-bounded uplifts and 

down-dropped basins, resulting in alternating narrow canyon 

and wide valley segments, before joining the Williamson 

River in the fault-bounded basin containing Upper Klamath 

Lake and the lower Williamson River.

The Sprague River Basin was affected greatly by the 

eruption of Mount Mazama that formed Crater Lake caldera 

about 7,700 calendar years before present (cal yr BP; Bacon, 

1983; Bacon and Lanphere, 1990; Zdanowicz and others, 

1999). The climactic eruption ejected 50 cubic kilometers 

(km3) of dense rock equivalent, forming a widespread fallout 

tephra covering more than 1,000,000 km2 of western North 

America (Sarna-Wojcicki and Davis, 1991). Fallout tephra 

thicknesses exceed 1 meter (m) in the northwestern part 

of the Sprague River Basin (Sherrod and Pickthorn, 1992) 

but decrease to less than 1 centimeter (cm) in the southern 

and eastern parts of the basin. In addition to hydrologic and 

vegetative effects (Newberry, 1857; Minckley and others, 

2007; Cummings and Conaway, 2009), remobilization of 

the silt-to-granule-size pumice changed the character of the 

Sprague and Sycan Rivers and flood plains.

Climate and Hydrology

The Sprague River Basin is a high, semi-arid basin in 

the rain shadow of the southern Cascade Range. Mean annual 

precipitation ranges from less than 40 cm in the valley floors 

to 120 cm at the high-altitude basin margins (PRISM Climate 

Group, 2012). Average precipitation for 1971–2000 in the 

basin was 54 cm (Risley and others, 2008). Most precipitation 

falls between October and March, with about 30 percent 

of the precipitation falling as snow in the valleys and more 

than 50 percent falling as snow in the uplands (Connelly and 

Lyons, 2007; Rabe and Calonje, 2009).

Streamflow has been measured systematically by 

the USGS in the Sprague River Basin since 1912, with 

long-standing gaging stations operated by the USGS or 

Oregon Water Resources Department (OWRD) on the 

Sprague River near its confluence with the Williamson River 

(Sprague River near Chiloquin, 11501000), on the Sycan 

River near its confluence with the Sprague River (Sycan River 

below Snake Creek, 11499100), and on the Sprague River 

upstream of its confluence with the Sycan River (Sprague 

River near Beatty, 11497500). Isolated measurements were 

made at some locations early as 1904 (USGS Oregon Water 

Science Center, Portland, Oregon, measurement station 

records for station 11497500). At the most downstream 

gaging station near Chiloquin (which has a contributing area 

of 4,053 km2, 97 percent of the total basin area), annual flow 

for 1921–2008 varied greatly but averaged 16.4 cubic meters 

per second (m3/s) (fig. 2). For 1971–2000, the average flow 

was 18.0 m3/s, equivalent to 13.8 cm of annual runoff from 

the basin and accounting for 25 percent of the average basin 

precipitation for that period. The average flow of 8.6 m3/s 

measured on the Sprague River near Beatty (11497500; 

1954–2009 available record) and 4.2 m3/s measured on the 

Sycan River downstream of Snake Creek (11499100; 

1974–2010 available record) account for about 80 percent 

of the total flow near Chiloquin.

Flows typically are greatest between December and 

June, representing seasonality in precipitation and snowmelt 

(fig. 3). Peak discharges affecting the lower river originate 

partly from snowmelt, with the largest peaks resulting from 

regional rain-on-snow events such as those in 1964, 1982, and 

1987. These mainly occur between December and February. 

The 422 m3/s flow of December 26, 1964, measured at the 

gaging station near Chiloquin (11501000) is the largest known 

flow (fig. 2). Spring snowmelt peaks typically are smaller, 

but can be of longer duration, and generally occur during the 

March–June period of overall higher flows (fig. 3).

Analyses of regional temperature, precipitation, and 

Sprague River annual runoff (at the station near Chiloquin, 

11501000) show no statistically significant temporal trends 

for records starting in the early 1900s and extending through 

1996 (Risley and Laenan, 1999). However, their analysis 

revealed changes in precipitation-runoff relations, particularly 

decreased runoff in relation to precipitation between 1930 

and 1950, increased runoff between 1950 and 1980, and then 

stable or decreased runoff between 1980 and 1996. Because 

these changes did not relate to temporal trends in any assessed 

climate variables, Risley and Laenan (1999) suggested that 

land-use changes possibly affected basin hydrology, although 

they did not identify specific causes or activities.

Springs and spring complexes locally influence flow 

(Gannett and others, 2007), water temperature (Watershed 

Sciences, Inc., 2000), and flood-plain geomorphology and 

habitat conditions in the basin. Spring discharge accounts 

for more than 60 percent of the annual Sprague River flow 

near Chiloquin (Gannett and others, 2007). In particular, 

large spring complexes on or adjacent to the Sprague River 

flood plain in the reach between FK 22 and FK 32 (including 

Kamkaun Spring) and east of Beatty (FK 80 to FK 90) 

contribute about 31 percent of the annual flow (Gannett 

and others, 2007). Possibly because of modulated water 

temperatures and stable channel substrate conditions, these 

spring areas are abundantly used by fish, including redband 

trout (Oncorhynchus mykiss), sculpin (Cottidae), and suckers 

(Catostomidae; Ellsworth and others, 2007). Probably for 

similar reasons as well as access to fish, spring areas also 

have been areas of long-standing cultural occupations and 

use (Spier, 1930; Cressman and others, 1956; Jenkins and 

Connolly, 2007).
Sprague River Basin 7

tac14-0898_fig 02 Peak discharge, in cubic meters per second

Water year

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

0

50

100

150

200

0

5

10

15

20

Sprague River near Beatty, Oregon

Streamflow-gaging station:: 11497500, 1954–2009

Drainage area: 1,370 square kilometers

Mean annual flow: 8.6 cubic meters per second 

Mean annual flow, in cubic meters per second

0

100

200

300

400

500

0

10

20

30

40

50

Sprague River near Chiloquin, Oregon

Streamflow-gaging station: 11501000, 1921–2008

Drainage area: 4,053 square kilometers

Mean annual flow: 16.4 cubic meters per second 

A

0

50

100

150

200

0

5

10

15

20

Sycan River below Snake Creek near Beatty, Oregon

Streamflow-gaging station:: 11499100, 1974–2007

Drainage area: 1,434 square kilometers

Mean annual flow: 4.2 cubic meters per second 

no data

B

C

Peak annual discharge 

Mean annual flow 

Mean flow for period of record

EXPLANATION

Figure 2. Annual peak discharge for streamflow-gaging stations at (A) Sprague River near Chiloquin, station 

11501000; (B) Sycan River below Snake Creek near Beatty, station 11499100; and (C) Sprague River near Beatty, station 

11497500, Sprague River Basin, Oregon.
8 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 03

0

20

40

Sprague River near

Chiloquin (1922–2008) Sycan River near Beatty

(1973–2008)

Oct. Nov. Dec. Jan. Feb. Mar. Apr.

Month

Discharge, in cubic meters per second

May June July Aug. Sept.

Sprague River near

Beatty (1954–2008)

Figure 3. Mean daily discharge for selected streamflow-gaging stations, Sprague River Basin, Oregon.

Vegetation

As summarized by Connelly and Lyons (2007) and 

Rabe and Colonje (2009), the uplands of the Sprague 

River Basin are vegetated largely by mixed conifer forests 

dominated by ponderosa (Pinus ponderosa) and lodgepole 

pine (Pinus contorta). At lower and warmer altitudes, the 

conifer forests transition to sagebrush (Artemisia L.) steppe 

or sagebrush-juniper (Juniperus L.) woodlands. Valley 

bottoms and riparian corridors are vegetated with riparian 

shrublands, grassland meadows, wetland vegetation, and, in 

many locations, irrigated pasture grasses and hay. In some 

reaches, nonnative stands of reed canarygrass (Phalaris 

arundinacea) have colonized riparian areas. Detailed 

discussion of flood‐plain and riparian vegetation and historical 

vegetation trends follows in the section, “Flood-Plain and 

Riparian Vegetation.”

Historical Human Influences and Land Use

The Sprague River Basin has a long history of human 

use and settlement, starting with hunting, gathering, fishing, 

and habitation by Klamath, Modoc, and Yahooskin Native 

Americans. The high country of the basin was used for 

hunting and gathering during the summer, but the lower 

Sprague River Valley, particularly areas near the large 

spring complexes between FK 22.0 and FK 32.0, were 

important winter settlement sites since before the Mazama 

eruptions of 7,700 cal yr BP (Cressman and others, 1956). 

European exploration and settlement began with 1826 forays 

by fur trappers of the Hudson’s Bay Company (Helfrich, 

1974). The Klamath Indian Reservation was established 

in 1864, encompassing much of the Sprague River Basin 

west of the confluence of the North and South Forks of the 

Sprague River, and leading to the 1869 establishment of the 

Yainax sub-agency near the present town of Sprague River. 

Allotments to tribal members in conjunction with The General 

Allotment (Dawes) Act of 1887 resulted in private ownership 

of much of the valley bottoms within the reservation boundary. 

In 1954, the Klamath Tribes were “terminated,” with 

much of their unallocated land base becoming the Winema 

National Forest.

The main land uses in the basin have been livestock 

grazing and timber harvest, which began in the late 19th 

century and have continued at varying intensities to the 

present. Livestock was an economic mainstay for residents 

of the Sprague River Basin in the late 19th and early 20th 

centuries, resulting in widespread overgrazing by 1907 

(Connelly and Lyons, 2007, p. 2–5). Livestock was supported 

partly by irrigated hay and forage production in the valley 

bottoms, leading to digging of diversion ditches and temporary 

dams along the Sprague River starting as early as 1890 

(Helfrich, 1974).

The timber industry lagged slightly behind the livestock 

industry, awaiting the linkage of the Southern Pacific Railroad 

between California and Chiloquin in 1911, and then the 

completion of the Oregon, California, and Eastern (OC&E) 

Railroad from Chiloquin to Bly in 1928 (Helfrich, 1974). 

This railroad network aided harvest of the massive stands 

of ponderosa pine in the uplands of the Sprague River and 

surrounding basins. During the first half of the 20th century, 

many mills operated along the Sprague River from Bly to 

Chiloquin, with logs and lumber transported by rail and river. 

Timber production in the basin has declined significantly since 

the 1950s, with all mills closed since then and the railroad 

grade converted to the OC&E Trail operated by Oregon 

State Parks.

Presently, agriculture, livestock raising, and timber 

management remain as the primary land uses within the 

Sprague River Basin, although at decreased intensities. Forest 

management now focuses more on improving forest health. 

Agriculture is concentrated within the wide alluvial basins 

and is almost all pasture and hay fields, supporting ongoing 

livestock operations.
Study Area, Methods, and Data Sources 9

Study Area, Methods, and 

Data Sources

Analyses were based on integrated consideration of 

geologic and geomorphic setting, historical observations, 

and current conditions and processes. The approach was 

multifaceted, relying on mapping and stratigraphic analysis 

of flood-plain deposits and flanking features; evaluation of 

historical records and observations; systematic mapping and 

analysis of flood-plain and channel characteristics (including 

morphologic and vegetation conditions) from historical 

surveys, maps, and aerial photographs; and a 2006 survey 

of depositional features left by early 2006 high flows. This 

section provides a synopsis of the study area and analysis 

framework, including general methods and source data.

Descriptions of the specific methods and analyses are provided 

in subsequent sections that detail the geomorphic mapping and 

valley segment delineation, physical channel and flood-plain 

processes, and flood-plain and riparian vegetation.

Study Area

This study focused on the lower, alluvial segments of 

the Sprague River system, including the lower parts of the 

Sycan River, North Fork Sprague River, South Fork Sprague 

River, and the entire 136.1 km of the Sprague River between 

the confluence of the North and South Forks and the Sprague 

River confluence with the Williamson River at Chiloquin 

(fig. 1). Analysis of the Sycan River focused on the lowermost 

11.3 km downstream of its emergence from the Sycan Canyon 

near Coyote Bucket.

Analyses concentrated on the channel and flood plain 

within an area mapped and defined as the “geomorphic flood 

plain” of the main-stem Sprague River and the lower alluvial 

portions of the three major tributaries. As described in more 

detail in the section, “Geomorphic History”, the geomorphic 

flood plain (pl. 1) was mapped on the basis of topography and 

existing soils information (Cahoon, 1985), supported by field 

and stratigraphic observations.

For many analyses, results and inferences were stratified 

by 13 valley segments subdivided from the geomorphic flood 

plain on the basis of valley form and major tributary junctions 

(table 2; fig. 1). These segments included nine encompassing 

the 136.1 km of main-stem Sprague River, two for the lower 

Sycan River, and one segment each for the South Fork 

Sprague and North Fork Sprague Rivers within the study area. 

Segment lengths (as measured along flood-plain centerline) 

ranged from 3.6 to 18.8 km.

Geomorphic Mapping

Geomorphic mapping establishes the basic context 

for understanding modern channel conditions by defining 

major elements of late Cenozoic geologic history shaping the 

geomorphology of the study area and outlining the geomorphic 

flood plain, which is the spatial domain for assessing 

channel change and vegetation conditions in the flood plain. 

Additionally, the process of defining and mapping valley-bottom 

landforms substantially aids in identifying key flood-plain and 

channel processes (for example, Coffman and others, 2011, 

Simenstad and others, 2011). The mapping domain broadly 

corresponds with the extent of lidar topography acquired in 

November 2004 (Watershed Sciences, Inc., 2005) and includes 

the main-stem Sycan, Sprague, and North Fork Rivers within the 

broad alluvial valleys. The mapping encompasses the main flood 

plains and contiguous alluvial and colluvial landforms (pl. 1). 

The geomorphic mapping was based on aerial photographs, the 

2004 lidar data, U.S. Geological Survey 7.5-minute topographic 

maps, existing soil mapping (Cahoon, 1985), reconnaissance 

field observations, and stratigraphic sections, primarily along 

bank exposures but supplemented by augering. Linework was 

digitized at scales ranging from 1:5,000 to 1:10,000, using the 

2004 lidar data as a base.

Stratigraphic Studies

Along with the geomorphic mapping, stratigraphic 

studies revealed conditions and processes prior to 20th-century 

historical records. Stratigraphic sections measured at cut 

banks along the main-stem Sprague River and all major 

tributaries (appendix A) enabled documentation of depositional 

environments and changes in channel and flood-plain materials, 

mainly for the last 10,000 years. Additionally, augering transects 

provided information on the distribution of specific deposits, 

such as those from the Sycan flood of about 7,500 years ago 

(Lind, 2009), as well as documentation of the altitude and age 

of paleochannel positions for the last 3,500 years. Stratigraphic 

measurements and descriptions at streamside exposures and 

from the augering transects included characterization of major 

depositional units, their sedimentary structures and textures, 

the nature of contacts between units, pedogenic alteration and 

bioturbation, and interpretation of the depositional environment. 

Deposit chronology was by radiocarbon dating of detrital and 

in-place organic materials (appendix B). Additionally, three 

samples of volcanic materials were submitted for identification 

(appendix C). At some sites, analysis of Cesium-137 content 

allowed determination of deposits emplaced after widespread 

above-ground nuclear testing in the 1950s (appendix D).
10 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon Table 2. General valley segment characteristics, Sprague River Basin, Oregon.

[Segment length: Segment length measured along flood-plain centerline. Abbreviations: km, kilometer; m, meter; NFFK, North Fork Sprague River flood-plain kilometer; SYFK, Sycan River flood-plain kilometer]

Valley

segment

Flood-plain 

kilometer

Valley 

form

Segment

length

(km)

Mean 

flood-plain 

width

(m)

Sinuosity 

(2000)

Channel 

length 

(2000)

(m)

Mean 

channel 

width 

(2000)

(m)

Channel

slope

(2000)

Channel

pattern

Woody vegetation 

types

Chiloquin Canyon 0 to 11.4 Confined, steep 11.4 100 1.06 12,100 37.8 0.00195 Straight Ponderosa prevalent with many

shrubs, local aspen and cottonwood.

Braymill 11.4 to 17.2 Confined 5.8 110 1.07 6,200 36.0 0.00024 Straight Ponderosa prevalent with many

shrubs, local aspen and cottonwood.

Kamkaun Spring 32.4 to 17.2 Unconfined 15.2 500 1.59 24,200 33.8 0.00015 Meandering;

some confinement by levees

Shrubs-including some tree formwillow.

S’Ocholis Canyon 32.4 to 48.2 Confined 15.8 170 1.12 17,700 27.7 0.00027 Straight Ponderosa, shrubs, local aspen.

Buttes of the Gods 48.2 to 58.0 Unconfined 9.8 870 2.01 19,700 35.8 0.00019 Meandering; 

some confinement by levees

Few shrubs. No trees.

Council Butte 58.0 to 76.8 Unconfined, 

low gradient

18.8 840 1.70 32,000 35.0 0.00015 Meandering; 

some confinement by levees

Few shrubs. No trees.

Beatty-Sycan 76.8 to 81.0 Unconfined 4.2 910 1.68 7,300 29.4 0.00021 Meandering Few shrubs. No trees.

Beatty Gap 81.0 to 89.6 Partly confined 8.6 240 1.39 12,000 17.3 0.00024 Meandering Many shrubs, some aspen and

ponderosa. 

Upper Valley 89.6 to 93.2 Unconfined 3.6 1,280 1.37 4,900 17.8 0.00033 Meandering; channelized

in some sections

Few shrubs. No trees. 

South Fork 93.2 to 106.3 Unconfined 13.1 1,650 1.17 14,800 10.5 0.00100 Channelized, straight;

meandering in upper part 

Few shrubs. No trees.

North Fork NFFK 0 to 9.8 Partly confined 9.8 530 1.39 13,7001a 11.0 0.001241b Meandering Few shrubs. No trees. 

Lower Sycan SYFK 0 to 10.6 Partly confined 10.6 220 1.38 14,6001c 16.9 0.000351d Meandering Many shrubs. Some ponderosa at

uppermost extent.

Coyote Bucket SYFK 10.6 to 24 Confined, steep 13.4 60 1.04 14,000 12.3 0.017942 Straight Many shrubs and pondersosa.

1Value is for within distinct flood-plain segment; total including part of river in Sprague River flood plain is 15,600a; 0.001156b; 16,100c; 0.00029d

.

2Slope value is for flood-plain kilometers 10.6 to 15.2.
Study Area, Methods, and Data Sources 11

Historical Observations and Photographs

Early written accounts of channel and flood-plain 

conditions are sparse because the Sprague River Basin was not 

near major exploration and transportation routes. Aside from 

the General Land Office (GLO) surveys, the earliest accounts 

documenting channel and flood-plain conditions are from 

the early 1900s. These accounts include a land classification 

and timber survey of the Klamath Quadrangle (Leiberg, 

1903; includes the study area west of FK 91.8), a preliminary 

report on water resources for the Klamath Indian Reservation 

(Henshaw, 1912), and field notes of botanist W.E. Lawrence 

summarizing observations in July 1922 and July 1934 

(W.E. Lawrence, Oregon State University Herbarium, 

Corvallis, Oregon, unpublished field journals).

Early USGS records of streamflow measurement and 

related activities document channel and flow conditions 

as well as anecdotally describe diversions and log-driving 

activities on the Sprague River. In particular, station notes 

and photographs provided evidence of channel conditions 

dating back to 1904 for USGS streamflow measurement 

sites on the South Fork Sprague River near Bly, North Fork 

Sprague River near Bly, Fivemile Creek near Bly, Sprague 

River near Beatty, Sycan River near Beatty, and Sprague River 

near Chiloquin (streamflow-gaging station records available 

at U.S. Geological Survey, Oregon Water Science Center, 

Portland, Oregon). The most extensive accounts are for the 

period between 1912 and 1930.

Evidence for decreased beaver (Castor canadensis), 

otter (Lutrinae Bonaparte), and muskrat (Ondatra zibethicus) 

populations also is recorded in some of the streamflow-gaging 

station records (U.S. Geological Survey, Oregon Water 

Science Center, Portland, Oregon) as well as in 1939–43 

correspondence archived from Klamath Agency files (Larry 

Dunsmoor, Klamath Indian Nation, written commun., 2006). 

U.S. Army Corp of Engineers and related Klamath County 

memoranda from the 1960s through the 1990s document 

levee construction and damage (Klamath County, written 

commun., 2008).

Nineteenth-Century Cadastral Surveys

The first systematic surveys in the Sprague River Basin 

were the cadastral surveys by the U.S. General Land Office 

(GLO; succeeded by the Bureau of Land Management). 

The study area was surveyed in several different contracts 

spanning 1865–92 (table 3). Township boundaries and 

subdivisions for most of the main-stem Sprague River were 

surveyed between 1866 and 1872. However, subdivisions for 

parts of the Braymill, Coyote Bucket, and Chiloquin Canyon 

segments were first surveyed in 1892.

The GLO surveys entailed laying out townships of 

36 sections, each of which was one square mile. The exterior 

boundaries of the townships and interior section lines 

(subdivisions) were established by surveying along lines 

running north-south and east-west. Where these lines cross 

rivers, the location (relative to monumented section corners) 

and width of the river were recorded in the accompanying 

GLO field notes. Although the resulting township maps show 

continuous channels, the river was surveyed only at the section 

and township boundary lines, with the course between lines 

estimated by the cartographer. Later, for some townships, 

riverbank lines were surveyed (termed “meandering”). This 

was done for parts of three townships within the Sprague 

River study area between 1871 and 1872 (35S 7E, 36S 11E, 

and 36S 12E; table 3). These meander surveys provided more 

complete information on the channel path between section 

lines; however, because these surveys typically followed 

the edge of the bank rather than the edge of the water, it is 

unclear whether they closely delimited the wetted channel. 

Consequently, width analyses based on the GLO surveys 

chiefly are based on the widths determined from the boundary 

and section line surveys as recorded in the GLO field notes, 

although the meander surveys were digitized from the maps 

and used for some channel planform analyses.

Aerial Photographs

The earliest aerial photographs available for the Sprague 

River system were acquired in 1940–41 (described hereafter 

as “the 1940 photographs”). These photographs, as well as 

aerial photographs from 1968 and 2000, served as the primary 

basis for mapping river and flood-plain conditions for different 

times during the 20th century (table 4). For the 1940 and 

1968 aerial photographs, contact print photographs were 

scanned, rectified, georeferenced, and mosaicked following 

the methods of Hughes and others (2006), to create digital 

imagery with resolution of 1-m pixels. The 2000 imagery was 

available as digital orthophotograph quadrangles from the 

U.S. Geological Survey. The 1940 aerial photographs cover 

most but not all of the study area, extending to FK 95.2 on 

the South Fork Sprague River, NFFK 5.8 on the North Fork 

Sprague River, and SYFK 13.6 on the Sycan River. Therefore, 

for some analyses, parts of these upstream areas are not 

included. Secondary photographic sources included 1975 

USGS orthoimagery and 2005 digital orthophotographs from 

the U.S. Dept. of Agriculture (table 4).
12 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Table 3. Early (1865–92) General Land Office surveys in the Sprague River study area, Oregon.

[Township and range: S, south; E, east. Abbreviations: FK, flood-plain kilometer; NFFK, North Fork Sprague River flood-plain kilometer SYFK, Sycan 

River flood-plain kilometer; NA, not applicable]

Township Range Valley

segment

Flood-plain

kilometer

First 

surveyed

Subdivision survey

date(s) Meander survey

35S 7E Chiloquin Canyon 0 to 6.9 1871 11-04-1871 to 07-19-1872 Right bank from FK 9 to 0 

(in section 3) meandered 

11-04-1871 to 07-19-1872

34S 7E Chiloquin Canyon 6.9 to 11.2 1871 109-07-1871 NA

34S 8E Chiloquin Canyon;

Braymill; Kamkaun

Spring

11.2 to 25.4; 

30.1 to 30.6

1869 11-13 to 11-25-1892 NA

34S 9E Kamkaun Spring,

S’Ocholis Canyon

25.4 to 30.1; 

30.6 to 33.2

1869 07-31 to 08-18-1869 NA

35S 9E S’Ocholis Canyon,

Buttes of the Gods

33.2 to 49.4 1866 Completed 10-10-1866 NA

35S 10E Buttes of the Gods 49.4 to 50.2; 

52.8 to 54.0

1866 Completed 10-03-1866 NA

36S 10E Buttes of the Gods;

Council Butte

50.2 to 52.8; 

54.0 to 61.4

1866 Completed 10-16-1866 NA

36S 11E Council Butte 61.4 to 71.6 1866 Completed 10-08-1866 Left bank meandered 

07-27-1872 to 08-08-1872

36S 12E Council Butte, 

Beatty-Sycan, 

Beatty Gap,

Lower Sycan

71.6 to 81.9; 

SYFK 0 to 2.2

1866 Completed 10-27-1866 Left bank meandered 

08-09-1872 to 08-15-1872 

36S 13E Beatty Gap, 

Upper Valley

81.9 to 92.6 1865 Completed 08-30-1865 NA

36S 14E Upper Valley, South

Fork, North Fork

92.6 to 104.0;

NFFK 0 to 4.2 and

5.4 to 9.8

1866 Completed 09-05-1866 NA

37S 15E South Fork 104.0 to 106.3 1866 Completed 09-22-1866 NA

35S 14E North Fork NFFK 4.2 to 5.4 1866 Completed 09-01-1866 NA

35S 12E Lower Sycan, 

Coyote Bucket

SYFK 2.2 to 24 1866 Completed 09-19-1866 NA

1

Contract date, plat approved 11-06-1872.
Study Area, Methods, and Data Sources 13

Table 4. Primary data sources for maps and aerial photographs of the Sprague River study area, Oregon.[Abbreviations: BLM, Bureau of Land Management; CNO, California, Nevada, and Klamath River Basin, Oregon; USDA, U.S. Department of Agriculture; USGS, U.S. Geological Survey; m, meter; lidar, light detecting and ranging; FK, flood-plain kilometer for the mainstem Sprague and South Fork Sprague River; NFFK, North Fork Sprague River flood-plain kilometer; SYFK, Sycan River flood-plain kilometer; UO, University of Oregon]

Title Original scale Map and photograph date(s) Primary use Description Source

General Land Office(GLO) surveys

1:31,680 1866 to 1892 Channel position and width,

historical vegetationconditions

Earliest surveys conducted between 1866 and 1892 with full coverage ofthe study area; meander surveys conducted in 1872 show bank positionbetween FKs 0 and 9.0 and between FKs 61.4 and 81.9; map plats showchannel position and surrounding lands; notes provide limited details onchannel features, soil, and vegetation

Bureau of LandManagement (2011)

Land Classificationand Densityof StandingTimber, KlamathQuadrangle

1:250,000 1885 Historical vegetation

conditions

Reconnaissance timber classification survey conducted prior to 1900 onthe 1885–1887 Klamath Quadrangle topographic base. Map shows landclassification and density of standing timber. Covers study area west ofFK 103.6

Leiberg (1903)

USDA aerialphotographs

1:20,000 July 29, 1940 to

October 6, 1941

Flood-plain cover mapping,channel position andgeometry

120 black and white aerial photographs covering FKs 0–95.2 on the main-stem Sprague and South Fork Sprague Rivers, NFFKs 0–5.8 onthe North Fork Sprague River, and SYFKs 0–13.6 on the SycanRiver; project CNO USDA 8542; scanned and georectified by USGS/UO

NationalArchives

USDA aerialphotographs

1:20,000 May 2 to

September 1968

Flood-plain cover mapping,channel position andgeometry

39 black and white aerial photographs; full coverage of study area;

project USDA Klamath #ASCS 8-68-DC, scanned and georectified by USGS/UO

Universityof OregonLibrary

Klamath County soil survey 

1:20,000 1975 Geomorphic mapping,

channel centerline

Klamath County Soil Survey based on 1975 USGS Orthoimagery Cahoon (1985)

USGS digitalorthophotographquadrangles

1-m resolution July 22 to 

August 13, 2000

Flood-plain cover mapping,channel position andgeometry

Black and white orthorectified aerial photography; full coverage of study area

U.S. GeologicalSurvey (2012)

Lidar 1-m resolution 2004 Geomorphic mapping, 

channel centerline position

High-resolution topographic survey converted to digital elevation model;full coverage of study area

WatershedSciences, Inc.(2005)

USDA digitalorthophotographs

0.5-m resolution 2005 Channel centerline position Color orthorectified aerial photography; full coverage of study area U.S. Department

of Agriculture(2012)
14 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Lidar Topography

A lidar dataset covering most of the flood plain of the 

main-stem Sprague River, North Fork Sprague River, South 

Fork Sprague River, and lower Sycan River provided highresolution topography data. This lidar also was the basis 

for the geomorphic mapping. The lidar data were collected 

in November 2004 and represent normal autumn low-flow 

conditions (Watershed Sciences, Inc., 2005). The absolute 

vertical accuracy of the lidar point data is 0.052 m deviation 

root mean square error, 0.051-m standard deviation, 0.032-m 

median (50th percentile) absolute deviation, and 0.1057-m 

95th percentile absolute deviation. We worked with a 

gridded altitude dataset with 1-m spacing developed from the 

point data.

Survey of Effects of 2006 High Flows

High flows in winter and spring of water year (WY) 2006 

(October 1, 2005–September 30, 2006) aided investigation of 

depositional patterns associated with geomorphically effective 

flows. Between June 23 and July 15, 2006, deposit thickness, 

texture, and altitude were measured at 71 locations along the 

main-stem Sprague River, from FK 93.2 just downstream of 

the confluence of the North and South Forks of the Sprague 

River, to FK 17.2 at the upstream end of the Braymill 

segment. These measurements documented the distribution 

and texture of flood deposits, as well as their distribution and 

characteristics relative to flood-plain landforms.

Mapping and GIS Analysis Framework

Geomorphic features, vegetation classes, and cultural 

(built) features within the geomorphic flood plain were 

mapped from the rectified and mosaicked aerial photographic 

sets (table 5). All features for most of the study area were 

mapped from the 1940, 1968, and 2000 aerial photographs. 

The 1940 aerial photographs, however, did not completely 

cover the upstream parts of the South Fork Sprague River 

(upstream of FK 95.2), North Fork Sprague River (upstream 

of NFFK 5.8), and Sycan River (upstream of SYFK 13.6). 

Supplemental maps of channel the centerline position were 

obtained from 1975 USGS imagery forming the basis of 

a 1977 soil survey (Cahoon, 1985), the 2004 lidar data, 

and 2005 USGS digital orthophotographs (table 4). These 

flood‐plain features were digitized on screen at scale of 

1:2,000, although finer-resolution inspection and field 

checking were required for identification and confirmation of 

some mapping classes and boundaries.

The water surface and any exposed bars were mapped, as 

visible on each aerial photograph. The Sprague River channel 

has well defined, steep banks, and there is no evident active 

channel extending beyond the water and bar surfaces in most 

locations. Exposed bars are rare and add only a small area to 

the overall channel area. Therefore, in analyzing channel width 

and area, the extent of water was used to represent the channel.

All map data were compiled into a geodatabase for 

analysis (U.S. Geological Survey, 2013). Aside from the 

broadscale geomorphic surface mapping, the analysis domain 

was restricted to the geomorphic flood plains of the Sprague 

River, and the Sycan, North Fork Sprague, and South Fork 

Sprague Rivers within the study area. Spatial and temporal 

metrics of channel and flood-plain characteristics were assessed 

by segment and more continuously by adopting measurement 

frameworks based on channel and flood-plain centerlines, 

following the approach of O’Connor and others (2003c).

Table 5. Features mapped from the 1940, 1968, and 2000 aerial 

photography in the geomorphic flood plain, Sprague River study 

area, Oregon.

[For each of the Physical Flood Plain and Cover Class themes, mapped 

features cover the entire geomorphic flood plain with no overlap. For the 

Anthropogenic theme, features were mapped only where present. Sprague 

River basin GIS data are available at http://water.usgs.gov/GIS/metadata/

usgswrd/XML/sprague_river_oregon_geomorphology.xml]

Theme Feature class Mapped features

Physical flood

plain

Water Primary channel

Secondary channel

Backwater (alcove)

Pond

Spring

Spring channel

Tributary channel

Built pond

Irrigation water

Other water feature

Bar Flood plain-attached bar

Island-attached bar

Mid-channel bar

Other bar

Flood plain Island

Other flood-plain surface

Cover class Vegetation Tall woody

Short woody

Herbaceous

Bare

Water From physical flood plain mapping

Anthropogenic Built features Levee

Road

Railroad

Bridge

Building

Irrigation channel

Dams and diversion structures

Other built features
Geomorphic Mapping and Geologic History 15

A flood-plain centerline frame of reference, which was 

static for the entire analysis period, simplified comparison 

among different years and was used to evaluate overall 

flood‐plain characteristics and channel migration rates. 

Channel centerlines were mapped for each source dataset 

and were the basis for determining channel migration rates as 

well as providing a frame of reference for measuring channel 

characteristics such as width, bar frequency, and near-channel 

riparian conditions. For both the flood-plain and channel 

centerline reference frames, intersection points were created 

along the centerline at 200-m spacing. At each intersection 

point, transects perpendicular to the centerline were defined, 

and measurements were extracted from points along the 

transect line or, for some attributes, from flood-plain polygons 

within the area defined by adjacent transect lines and the 

geomorphic flood-plain boundary. These flood-plain polygons 

were used to assess areas of sand and gravel bars, water 

surface, vegetation types, and other flood-plain attributes. The 

flood-plain transects extended to the limits of the geomorphic 

flood plain. The channel transects extended 50 m in each 

direction from the channel centerline. To simplify analysis, the 

flood-plain centerline was smoothed in highly sinuous valley 

sections so that the resulting transects did not cross each other. 

No such smoothing was conducted for the channel centerlines.

Geomorphic Mapping and 

Geologic History

The geologic and geomorphic history creates the physical 

template for modern fluvial and ecologic processes. For the 

Sprague River study area, the Tertiary and Quaternary history 

of volcanic activity, basin-and-range faulting, and river 

integration and incision has established the overall geometry 

of the basin and produced alternating canyon and wide-valley 

reaches. Quaternary downcutting and lateral migration have 

left terraces and abandoned alluvial fans bounding the active 

flood plain, particularly in the broad alluvial valleys (pl. 1). 

Additionally, the flood plain and adjacent landforms have been 

affected by specific events during the late Holocene (such as 

the Mazama eruption and the ensuing delivery of substantial 

sand-size pumiceous sediment to the Sprague and Sycan 

Rivers), as well as more continuous flood-plain and channel 

processes, such as channel migration and avulsion, and 

flood‐plain accretion and erosion. 

Geomorphic Units

The area of mapping (pl. 1) was composed of the broad 

alluvial basins and contiguous fluvial and colluvial landforms 

flanking the Sprague River and the lower parts of the North 

Fork Sprague River, South Fork Sprague River, and the 

Sycan River. Within this area, which closely corresponds 

to the extent of the lidar coverage, 12 fundamental map 

units were defined (pl. 1; appendix E), representing present 

and past geomorphic environments and events. These 

landforms—including bedrock (undifferentiated), active 

and inactive alluvial fans, colluvial slopes, alluvial terraces, 

spring complexes, tributary and main-channel flood plains, 

and valley-fill surfaces—are mapped without specific regard 

to their constituent deposits, which distinguishes this map 

from typical geological maps. This is especially the case 

for the terraces and inactive alluvial fans, where alluvial 

processes have eroded older geologic units, primarily Tertiary 

lacustrine sediment, leaving landforms with thin and locally 

discontinuous caps of alluvial gravel.

Undifferentiated Bedrock

Irregular, typically hummocky or steep topography, 

underlain by Tertiary lacustrine sediment or volcanic rocks 

was mapped as undifferentiated bedrock. This map unit was 

defined only where completely surrounded by mapped alluvial 

or colluvial surfaces.

Landslide Deposits

Arcuate scarps bounding steep, hummocky topography 

indicate landslide masses. A few landslides are evident in the 

Chiloquin Canyon segment and in the Coyote Bucket segment 

of the Sycan Canyon. The Sycan Canyon landslides likely 

blocked the channel, resulting in the affected stream reaches 

traversing accumulations of large blocks of volcanic rock 

fallen from the canyon rim.

Colluvial Slopes

Steep but smooth slopes of as much as about 35 degrees, 

underlain by unconsolidated regolith, are formed by 

gravitational and alluvial transport processes such as 

rockfall, avalanching, biogenic (caused by living organisms) 

disturbance, and sheet-wash transport. Colluvial slopes 

typically head at steep bedrock outcrops, which are the source 

of material, and transition downslope to alluvial transport 

surfaces. Colluvium locally is an important source of coarse 

(gravel-size) material for the Sprague and Sycan Rivers, 

especially in canyon segments, where much of the flood 

plain is bordered by colluvium or bedrock. The distinction of 

colluvial slopes and active tributary fans is locally arbitrary, 

but tributary fans typically have slopes of less than 10 degrees.

Abandoned Fans

Incised, shallowly sloping (less than 10 degrees) alluvial 

transport surfaces descend toward the Sprague River Valley, 

especially along the southern valley margin between the towns 
16 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

of Sprague River and Bly. Locally, abandoned fan surfaces 

are labeled 1 through 4 on plate 1 on the basis of increasing 

degree of incision (and presumably age). The older surfaces 

only have isolated remnants of original transport surfaces 

composed of fluvial gravel, and are separated from younger 

(and lower) fan and tributary surfaces by slopes formed in 

the underlying Tertiary lacustrine sediment. Some abandoned 

fan surfaces, such as those south of the Sprague River Valley 

near Bly, are formed partly of pumiceous pyroclastic flow 

deposits derived from Tertiary volcanic centers to the south 

(Sherrod and Pickthorn, 1992). Near the Sprague and Sycan 

Rivers, tributary fan deposits locally are interbedded with 

main-stem fluvial channel and overbank deposits (for example, 

section 6/28/08-1; fig. 4). Primary soil taxonomic classes on 

abandoned fan surfaces include Haploxerolls, Argixerolls, and 

Durixerolls, denoting minor-to-significant accumulations of 

clays, silica, and carbonate. The ages of these surfaces likely 

range from Pliocene (but probably post-dating the 3.0±0.9 Ma 

Basalt of Knot Tableland) to perhaps as recent as early 

Holocene. Where the capping gravel is intact, the abandoned 

fans largely are stable features that contribute little sediment 

directly to the modern fluvial system. The sequence of 

abandoned alluvial fan surfaces indicate overall Tertiary and 

Quaternary incision of the Sprague River Valley, probably in 

conjunction with integration and incision of the Sprague River 

through fault-uplifted canyon segments downstream.

Active Tributary Fans

Shallowly sloping (less than 10 degrees) alluvial 

transport surfaces grade to modern main-stem and tributary 

flood plains, commonly with a singular or composite 

fan-shaped down-gradient termini. These are active alluvial 

transport surfaces heading from confined tributaries, colluvial 

slopes, and bedrock, formed where flow routes expand onto 

flat terraces, flood plains, and other flat bottomland surfaces. 

These surfaces commonly are gradational with colluvial 

slopes and valley bottomlands, but with intermediate slopes. 

Soils on active fan surfaces are Haploxerolls, Cryorthents, 

Cryofluvents, Cryoborolls, and Cryaquepts taxonomic classes, 

all of which only have incipient horizon development in the 

form of translocated and accumulated carbonates and silica 

consistent with late Pleistocene to Holocene ages. Many active 

fans have surfaces post-dating the 7,700 cal yr BP Mazama 

eruption. Active fans episodically provide sediment to the 

main-stem rivers and flood plains.

Terraces

Planar alluvial surfaces as much as 50 m higher than the 

active flood plain flank the Sprague River near its confluence 

with the Williamson River. Similarly, terraces at several 

altitudes of as much as 20 m higher than the active flood plain 

border the Sprague River downstream of the town of Sprague 

River (pl. 1). Upstream, isolated low terraces flank the Sprague 

River near Beatty Gap and along the lower Sycan River. The 

terrace surfaces are underlain by fluvial gravel, sand, and silt, 

and generally are stable features upon which Haploxeroll soils 

have formed, characterized by cambic B horizons and some 

carbonate accumulation (U.S. Department of Agriculture, 

1975). Terrace risers locally expose Tertiary lacustrine 

sediment or other bedrock units, indicating that at least some 

of the terraces are strath surfaces cut into the soft Tertiary 

sediment (for example, section 6/28/05-1; fig. 4). The positions 

and degree of soil development are consistent with ages of 

late Tertiary through Quaternary. All these terraces apparently 

pre-date the 7,700 cal yr BP Mazama eruption, judging from 

the presence of Mazama fallout tephra in the upper parts 

of their soil profiles (Cahoon, 1985). Like the abandoned 

alluvial fans, the terraces owe to episodic filling and incision 

during Quaternary downcutting of the Sprague River. Some 

of this downcutting may have resulted from base-level fall 

associated with integration of the upper Klamath River Basin 

(Sherrod and Pickthorn, 1992), but some terrace sequences 

may represent more local tectonic blockages associated with 

the north-northwest trending basin-and-range faulting affecting 

the downstream Sprague River Valley segments or regional 

aggradation during periods of enhanced sediment production in 

the basin.

Sycan Flood Deposits

A prominent planar surface extends south discontinuously 

from the Sycan Canyon, encompassing 5.1 km2 of the Sycan 

River valley bottom and its confluence with the Sprague 

River. This surface stands 3 m higher than the active flood 

plain at the downstream end of Sycan Canyon and descends 

to modern flood-plain level near the Sycan River confluence 

with the Sprague River (figs. 5, 6). The surface is underlain 

by as much as 3.35 m of bedded sand and gravel composed 

almost entirely of Mazama pumice (fig. 7). The deposits are 

finer and thinner downstream, where they are overlain by 

alternating beds of silty fine sand and sand. At their apex near 

the downstream end of the Sycan Canyon, these deposits 

grade to surfaces mantled with 1-m-diameter rounded basalt 

boulders, apparently originating from the canyon rim and walls 

and transported downstream. The soil capping these surfaces 

is classified mainly as an Ashy Typic Cryopsamment, denoting 

poorly developed soils formed in ash-rich and sandy parent 

materials. The pumiceous sand and gravel overlie organic-rich 

silt and clay deposits, locally peaty, and commonly containing, 

within 3–5 cm of its top, a 0.5-to-2.5-cm-thick layer of silt-and 

sand-size Mazama tephra (figs. 5, 8–10). This fallout tephra 

(fig. 10), its age constrained by radiocarbon dates here (fig. 5; 

appendix B) and in other areas (Hallett and others, 1997; 

Zdanowicz and others, 1999; Bacon and Lanphere, 2006), 

resulted from the Mazama eruption of about 7,700 cal yr BP.
Geomorphic Mapping and Geologic History 17tac14-0898_fig04

1,3121,3111,3101,3091,3081,307

1,3181,3171,3161,3151,3141,313

1,3181,3171,3161,3151,314

1,3191,3181,3171,316

Altitude, in meters above North American Vertical Datum of 1988

claysiltvf m vc sand

gravel

A. 6/28/05-1; FK 55.0 B. 9/13/07-3; FK 79.4 C. 9/13/06-2; FK 87.6

claysiltvf m vc sand

gravel

D. 6/28/08-1; SYFK 2.5

claysiltvf m vc sand

gravel

claysiltvf m vc sand

gravel Well sorted

and beddedsilt and sand

Pumiceoussilty sand, granules at base

Bioturbatedsilt

Angular gravel Angular gravel

Poorly sorted Poorly sorted muddy gravel muddy gravelPoorly sorted Poorly sorted muddy gravel muddy gravel

Round pebble Round pebble gravel; locally gravel; locally cemented, well cemented, well sorted

Pumiceous 

Round pebble gravel; locally cemented

Pumiceous;locally indurated; convoluted bedding

Diatomaceous;thickness variable

Railroad grade

Round pebble gravel

Finely bedded; indurated and jointed

Saturated;abundantequisetum roots; subtlesubhorizontalbedding

Common matrixsupported granules

Abundant pisoliths, mottled

Sparse pumice grains

Angular

Commonpumice grains

basaltclasts

Soil formedin overbankdepositsBioturbated overbankdepositsChanneland bardepositsTertiary lacustrinesediment

Quaternary alluvial fandeposits,locally cementedwith pedogenic silicaTertiary lacustrinesedimentTertiary pyroclastic flow deposits

Soil formed inbioturbed overbankdeposits; pumice likely airfall workedinto deposits; basalt clasts likely human placedWet meadow and lowflood-plain overbank deposits

Road fillSycan River overbank deposits (Sycan Flood?)Tributary fan fluvial and debrisflow depositsSycan River overbank depositsSycan River channel and bardeposits (Pleistocene?)

Dominant material Primary sedimentary structures Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sandGravel

Planar laminationTrough cross bedding

Horizontal graded bedsMassive

CracksBurrowsRootsRiver level at time  of description

EXPLANATION

Abbreviations: sand—vf, very-fine; m, medium; vc, very coarse 

Figure 4. Stratigraphic sections showing Late Quaternary exposures at (A) flood-plain kilometer (FK) 55.0, (B) FK 79.4, (C) FK 87.6, and (D) Sycan flood-plain kilometer 2.5, 

Sprague River study area, Oregon.
18 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

We infer that the Sycan flood deposits resulted from a 

large, pumice-laden flood down the Sycan River within a few 

decades or centuries of the 7,700 cal yr BP eruption. This 

flood and its origins and effects are described more fully in 

Lind (2009). The close proximity of the base of the deposits 

to unweathered Mazama fallout tephra (fig. 10) indicates 

deposition shortly after the eruption. The lack of stratigraphic 

breaks or other evidence of deposition hiatus within the thick 

pumiceous sand indicates deposition during a single event. 

The sedimentary structures (general upward fining of sediment 

textures in individual sections, as well the downstream fining 

and flat planar surface) also indicate fluvial deposition during 

a single event. Toward the Sycan River confluence with the 

Sprague River, where the flood deposits are closest to river 

level, the sedimentary structures are overlain by bedded silt 

and sand deposited by subsequent floods.

Although no mappable Sycan flood deposits are evident 

downstream of the Sycan River confluence with the Sprague 

River, the sediment-laden flow almost certainly continued 

downstream, probably with substantial effects to channel 

plan form and geometry. A 1948 excavation at Medicine 

Rock Cave, flanking the Sprague River near FK 11.0 between 

Braymill and Chiloquin, revealed as much as 50 cm of 

fluvially transported pumiceous sand and silt attributable to 

a short-lived episode of deposition shortly after the Mazama 

eruption (Cressman and others, 1956, p. 398–400). This 

distinct deposit, interbedded within a sequence of Sprague 

River fluvial deposits, rock from roof-fall, and occupation 

detritus, almost certainly is from the Sycan flood, and is 

evidence that the flow was one of the largest late Holocene 

floods on the main-stem Sprague River.

A plausible source for such a flood was the temporary 

impoundment of a lake in the Sycan Marsh area, possibly by 

dunes of Mazama pumice blocking the Sycan River channel 

near the marsh outlet (Lind, 2009). The Sycan flood probably 

had a mechanism, timing, and perhaps magnitude similar to 

that of a flood descending the Williamson River from Klamath 

Marsh after breach of a Mazama pyroclastic flow deposit that 

blocked the marsh outlet (Conaway, 2000; Cummings and 

Conaway, 2009).

The Sycan flood deposits are coarse, loose, and erode 

readily from disturbed sites, particularly along tall banks 

flanking the modern channel or flood plain (fig. 7). In eroding 

areas, the Sycan flood deposits provide substantial sand-size 

material to the lower Sycan River.

1,315

1,314

1,313

1,312

1,311

Mazama fallout tephra

Pumiceous

Pumiceous and

and lithic gravel

Pumiceous 

and lithic

gravel

7,630; 7,620 cal yr BP 

(6/24/08-1; split sample)

2,240 cal yr BP 

(7/24/07-1(9a))

2006 flood deposits

2006 flotsam

Cesium present

7/24/07-2/3; SYFK 0.02 7/24/07-1; SYFK 0.1

Sod

Vertically

accreting 

overbank

Vertically

accreting 

overbank

Wetland and

low flood plain

Vertically

accreting 

overbank

Sycan 

flood

Wetland 

Mazama eruption

Channel 

bed-material

Vertically

accreting 

wetland

and low

flood plain

Channel 

and bar

Laterally accreting

channel and bar

claysiltvf m vc sand gravel

claysiltvf m vc sand gravel

A

Dominant material

Primary sedimentary structures

Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Organic

Planar lamination

Massive

Horizontal graded beds

Cracks

Burrows

Roots

River level at time of 

 description

Radiocarbon sample location, 

 median age, and sample 

 number (appendix B)

EXPLANATION

2,240 cal yr BP 

(7/24/07-1(9a))

Abbreviations: sand—vf, very-fine; 

m, medium; vc, very coarse. 

cal yr BP, calendar years before 

present

Altitude, in meters above North American Vertical Datum of 1988

Figure 5. Stratigraphic sections of (A) Sycan River flood-plain kilometers (SYFK) 0.02 and 

0.1; (B) SYFK 1.6 and 1.7; (C) SYFK 3.5; (D) SYFK 6.8 and 7.3; and (E) SYFK 10.1, 10.3, and 10.6, 

Sprague River study area, Oregon.
Geomorphic Mapping and Geologic History 19

tac14-0898_fig 05b

B

Vertically

accreting 

overbank

Sycan 

flood

Vertically

accreting 

overbank

Vertically accreting

wetland and

low flood plain

Vertically accreting

wetland and

low flood plain

Vertically accreting

channel and bar

Channel and bar

Charcoal-rich

burned horizon

Well-sorted

and pumiceous

Lithic gravel

5,920 cal yr BP 

(6/22/07-5(1))

1,350 cal yr BP 

(6/22/07-4(6))

1,350 cal yr BP 

(6/22/07-4(6))

Pumiceous

Pumiceous

Peat layers

and abundant

detrital wood

Abundant

detrital 

charcoal

Sod

Sod

1,317

1,316

1,315

1,314

1,313

1,312

claysiltvf m vc

sand gravel

claysiltvf m vc

sand gravel

6/22/07-5; SYFK 1.6 6/22/07-4; SYFK 1.7 Dominant material

Primary sedimentary structures

Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Planar lamination

Trough cross bedding

Massive

Horizontal graded beds

Cracks

Burrows

Roots

River level at time of 

 description

Radiocarbon sample location, 

 median age, and sample 

 number (appendix B)

EXPLANATION

Altitude, in meters above North American Vertical Datum of 1988

Abbreviations: sand—vf, very-fine; 

m, medium; vc, very coarse. 

cal yr BP, calendar years before 

present

Figure 5.—Continued
20 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 05c

Dominant material

Primary sedimentary structures

Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Organic

Planar lamination

Massive

Horizontal graded beds

Cracks

Burrows

Roots

River level at time of 

 description

Radiocarbon sample location, 

 median age, and sample 

 number (appendix B)

EXPLANATION

C

Vertically

accreting 

overbank

Laterally 

accreting

bars and

flotsam

Vertically accreting

wetland and

low flood plain

Obliquely accreting

channel and bar

Sycan flood,

possibly reworked

Wetland 

Mazama eruption

Vertically accreting

wetland and

low flood plain

Vertically

accreting 

overbank

Obliquely

accreting 

bar and flood plain

Vertically

accreting 

overbank

Channel 

6/25/07-2; SYFK 3.5

Poorly exposed

Pumiceous

Pumiceous

Mazama fallout 

tephra

1,970 cal yr BP 

(6/25/07-1(3))

1,970 cal yr BP 

(6/25/07-1(3))

Pumiceous

Pumiceous

Pumiceous

Abundant

detrital 

wood

Indurated

lithic gravel

Sod

5,510 cal yr BP 

(6/25/07-2(1))

6/25/07-1; SYFK 3.5

claysiltvf m vc

sand gravel

claysiltvf m vc

sand gravel

1,317

1,316

1,315

1,314

1,313

1,312

Altitude, in meters above North American Vertical Datum of 1988

Abbreviations: sand—vf, very-fine; 

m, medium; vc, very coarse. 

cal yr BP, calendar years before 

present

Figure 5.—Continued
Geomorphic Mapping and Geologic History 21tac14-0898_fig05d

Altitude, in meters above North American Vertical Datum of 1988 Vertically accreting overbank Vertically accreting overbank, punctuated by flood plain fires

Channel and bar

Post-watershed-firebar depositionVertically accretingchannel and bar

Sod formed inSycan flood andeolian siltSycan flood,bioturbated andpossibly reworkedSycan floodMazama eruptionVertically accretingwetland andlow flood plain

Channel gravel

Charcoal-richburned horizon

1,310 cal yr BP (9/12/06-2(3))

1,620 cal yr BP (9/12/06-1(a))

1,620 cal yr BP (9/12/06-1(a))

530 cal yr BP (9/12/06-3(3))

Charcoal-richburned horizon

Covered

Charcoal-richburned horizons

2006 flood deposit

Sod

Sod

Abundant pumice grains

Abundant charcoal

Well-sorted andpumiceous;strongly oxidizedat base

Pumiceous

PumiceousPumiceousPumiceous

Pumiceous

Lithic gravelwith detrital woodinterbeds

1,3201,3191,3181,3171,3161,3151,314

claysiltvf m vc sand

gravel

claysiltvf m vc sand

gravel

claysiltvf m vc sand

gravel

9/12/06-3; SYFK 6.8

9/12/06-2; SYFK 6.8

9/12/06-1; SYFK 7.3

Abbreviations: sand—vf, very-fine; m, medium; vc, very coarse. cal yr BP, calendar years before present

Dominant material

Primary sedimentary structures

Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sandGravel

Planar laminationTrough cross beddingHorizontal graded bedsMassive

CracksBurrowsRoots

Radiocarbon sample location, median age, and sample number (appendix B)River level at time of description

EXPLANATION

D

Figure 5.—Continued
22 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 05e

E

1,323

1,322

1,321

1,320

1,319

1,318

1,317

1,316

1,315

Sycan flood,

bioturbated and

possibly 

reworked

Sycan flood,

with pause in

flow allowing

silt deposition

Mazama 

eruption

Vertically 

accreting

wetland and

low flood plain

Sod formed in

Sycan flood and

eolian silt

Sycan flood,

with pause

in flow 

allowing silt

deposition

Mazama 

eruption

Vertically 

accreting

wetland

and low

flood plain Vertically

accreting 

overbank

Vertically and 

obliquely 

accreting bar

Channel

gravel

Organic

flotsam

Silt-sized 

glass shards

Silt-sized

glass shards

Pumice grains

in silt and 

organic matrix

Covered

Abundant 

pumice grains

Pumiceous

Pumiceous

Pumiceous

Pumiceous

Pumiceous

Pumiceous

Lithic gravel Detrital wood

600 cal yr BP 

(7/1/05-2)

600 cal yr BP 

(7/1/05-2)

11,640 cal yr BP 

(7/1/05-1)

Dispersed 

charcoal

(Saturated)

7/2/05-1; SYFK 10.1 7/1/05-2; SYFK 10.3

7/1/05-1; SYFK 10.6 (auger)

claysiltvf m vc

sand gravel

claysiltvf m vc

sand gravel

claysiltvf m vc

sand gravel

Cesium

present

Altitude, in meters above North American Vertical Datum of 1988

Dominant material Primary sedimentary structures

Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Gravel

Organic

Planar lamination

Trough cross bedding

Massive

Horizontal graded beds

Cracks

Burrows

Roots

River or groundwater level 

 at time of description

Radiocarbon sample location, 

 median age, and sample 

 number (appendix B)

EXPLANATION

600 cal yr BP 

(7/1/05-2)

Abbreviations: sand—vf, very-fine; 

m, medium; vc, very coarse. 

cal yr BP, calendar years before 

present

Figure 5.—Continued
Geomorphic Mapping and Geologic History 23

tac14-0898_fig 06

Sycan River flood-plain kilometer

-2 0 2 4 6 8 10 12

Altitude, in meters above North American Vertical Datum of 1988

1,312

1,314

1,316

1,318

1,320

1,322

1,324

7/1/05-1

7/1/05-2

7/2/05-1

9/12/06-2/3

6/25/07-1/2

6/22/07-56/28/07-1

7/24/07-1

7/24/07-2

6/22/07-4

9/12/06-1

7/24/07-1

About 7,700 calendar years before present (cal yr BP)

 flood-plain surface (prior to Sycan flood)

About 7,600 cal yr BP Sycan flood terrace

Post 2,200 cal yr BP flood plain

Post 600 cal yr BP flood plain (actively accumulating)

Water surface, from 2004 lidar

Station identification No.

EXPLANATION

Figure 6. Flood-plain and terrace surface profiles estimated from stratigraphic sections and observations along 

lower Sycan River, Sprague River study area, Oregon. Modified from Lind (2009).

A B

Sycan flood deposits

Sycan flood deposits

Figure 7. Pumiceous sand deposits of the Sycan flood about 7,700 calendar years before present at (A) exposed site 7/2/05-1, Sycan 

River flood-plain kilometer (SYFK) 10.1 (July 2, 2005); and (B) site 9/12/06-2, SYFK 6.1 (June 20, 2006), lower Sycan River valley segment, 

Sprague River study area, Oregon. Photographs taken by J.E. O’Connor, U.S. Geological Survey.
24 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 08

claysiltvf m vc

sand gravel

1,297

1,296

1,295

1,298

claysiltvf m vc sand gravel

claysiltvf m vc sand gravel

clay

siltvf m vc sand gravel

1,321

1,320

1,319

1,318

1,317

1,316

1,315

1,314

Vertically

accreting 

overbank

Point bar

or channel

Vertically

accreting 

overbank

Point bar

or channel

Vertically

accreting 

overbank

Vertically

accreting 

wetland

peats and 

clay+silt

Vertically

accreting 

wetland

peats and 

clay+silt

Point bar

or channel

Channel

sand

Vertically

accreting 

overbank

Point bar 

or channel 

860 cal yr BP

(6/28/07-2(3))

2,690 cal yr BP

 (9/13/06-3(1))

2,690 cal yr BP

 (9/13/06-3(1))

120 cal yr BP 

(9/13/06-1(2))

Abundant charcoal

2006 flood deposit

2006 flood deposit

Diatomaceous

Pumiceous

Auger Probe

Pumiceous

Pumiceous

Pumiceous

Pumiceous

A. 6/28/07-2

FK 26.3

B. 9/13/06-3

FK 82.4

C. 9/13/06-1

FK 87.7

D. 6/23/07-1

FK 98.5

Sod

Mazama 

airfall 

tephra

Dominant material

Primary sedimentary structures

Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Gravel

Organic

Planar lamination

Trough cross bedding

Massive

Horizontal graded beds

Inclined graded beds

Cracks

Burrows

Roots

River level at time of description

Radiocarbon sample location, 

 median age, and sample 

 number (appendix B)

Outsized rock clasts

EXPLANATION

Altitude, in meters above North American Vertical Datum of 1988

Abbreviations: sand—vf, very-fine; 

m, medium; vc, very coarse. 

cal yr BP, calendar years before 

present

Figure 8. Stratigraphic sections of (A) flood-plain kilometer (FK) 26.3, (B) FK 82.4, (C) FK 87.7, and (D) FK 98.5, along main-stem and 

South Fork Sprague River geomorphic flood plain, Oregon.
Geomorphic Mapping and Geologic History 25

tac14-0898_fig 09

Vertically

accreting 

overbank

Oblique 

flood-plain

accretion

Vertically

accreting 

overbank

Obliquely accreting

channel bar

Lacustrine or

wetland

Vertically

accreting 

wetland

peats and 

clay+silt

Vertically

accreting 

overbank

Channel and bar

Unconformity

Vertically

accreting 

wetland

peats and 

clay+silt

2006 flood deposit

Charcoal rich

Detrital wood Pumiceous

Pumiceous

Pumiceous

Cesium present

Pumiceous

2006 flood deposit 2006 flood deposit

Abundant

detrital 

wood and 

charcoal

Abundant

sedge stems

Peat

Peat

Diatomaceous

4,330 cal yr BP

 (6/26/07-3b(1))

4,330 cal yr BP

 (6/26/07-3b(1))

4,710 cal yr BP

 (9/14/07-1(9))

3,490 cal yr BP

 (9/14/07-1(2)) 300 cal yr BP (6/26/07-3a(2))

approximate stratigraphic position

Cesium present

claysiltvf m vc

sand gravel

claysiltvf m vc

sand

claysilt

gravel

vf m vc

sand gravel

1,320

1,319

1,318

1,317

1,323

1,322

1,321

1,320

1,319

Section a Section b

A. 6/26/07-3; NFFK 0.7

A

B. 9/14/07-1; NFFK 1.2

B

Altitude, in meters above North American Vertical Datum of 1988

Dominant material Primary sedimentary structures Secondary structures

Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Gravel

Organic

Planar lamination

Trough cross bedding

Massive

Horizontal graded beds

Inclined graded beds

Cracks

Burrows

Roots

River level at time of description

Radiocarbon sample location, 

 median age, and sample 

 number (appendix B)

EXPLANATION

Abbreviations: sand—vf, very-fine; 

m, medium; vc, very coarse. 

cal yr BP, calendar years before 

present

Figure 9. Stratigraphic sections of (A) North Fork Sprague River flood-plain kilometer (NFFK) 0.7, and (B) NFFK 1.2, along 

North Fork Sprague River geomorphic flood plain, Oregon.
26 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 10

Low flood plain or wetland sediment

Mazama fallout tephra

Ash-rich low flood plain 

or wetland sediment

Pumice granules of Sycan flood deposits

Figure 10. Mazama fallout tephra and Sycan flood deposits 

exposed at site 7/24/07-2/3, Sycan River flood-plain kilometer 

(SYFK) 0.02, Sprague River study area, Oregon. Photograph taken 

by J.E. O’Connor, U.S. Geological Survey, September 12, 2007.

Active Tributary Flood Plain

Tributary channels and flanking surfaces grade to modern 

main-stem channels and flood plains, forming narrow and 

elongate surfaces extending into the uplands where channels 

become increasingly confined. In some areas, especially near 

Kamkaun Spring, the tributary valleys have very low, nearly 

horizontal gradients, whereas in many locations, tributary 

valley flood plains have gradients of as much as 5 degrees. 

The distinction between tributary fans and colluvium locally 

is indistinct, but primarily is made on the basis of plan-view 

morphology and slope. Primary soils on tributary flood 

plains are Inceptisols and Mollisols, which typically form in 

late Pleistocene or Holocene deposits (U.S. Department of 

Agriculture, 1975).

Main-Stem Valley Fill

Low-gradient planar surfaces totaling 28 km2 occupy 

broad basins flanking the main Sprague River flood plain, 

particularly downstream of the town of Sprague River. 

Additionally, this map unit includes narrow bottomlands 

flanking the post-Mazama zone of channel migration 

(the geomorphic flood plain) between Sprague River and 

Beatty Gap. These surfaces generally have soils mapped as 

Inceptisols or Mollisols formed partly by cumulic deposition 

of silt and clay during overbank flooding. Many of the 

surfaces were historically flooded during periods of high 

water, but showed no evidence of hosting major channels. 

Many of the surfaces now are diked and drained. Some of 

the broad valley bottoms marginal to the main river course 

appear to be sites of long-term sediment accumulation as a 

consequence of overall Sprague River Valley aggradation, 

perhaps in conjunction with block faulting along the northnorthwest trending faults transecting the lower part of the 

Sprague River Valley. In places, this map unit may correspond 

with low terraces mapped upstream of the town of Sprague 

River. The valley-fill map unit represents areas of Holocene 

deposition during main‐stem overbank flooding as well as 

from local runoff during seasonal high water.

Pond and Wetland Deposits

Several small closed depressions host seasonal-toperennial waterbodies. In plate 1, these waterbodies are 

distinguished only outside the geomorphic flood plains, 

although all waterbodies are mapped for each aerial 

photographic set. Most of these waterbodies shown on 

plate 1 are within areas of valley fill or occupy depressions 

within abandoned alluvial fans. Nearly all waterbodies are 

used for water storage, with dikes or small dams augmenting 

storage capacity.

Active Springs and Spring Deposits

Springs and related features such as ponds, wetlands, 

and channels are common within the study area. Most of 

these features are within or contiguous with the geomorphic 

flood plain or flanking terraces. Spring outlets with flowing 

water have sandy-to-gravel substrates, whereas surrounding 

saturated areas are composed mainly of peat deposits. Most 

spring complexes are connected to the Sprague and Sycan 

Rivers by sand-bed spring channels.

Geomorphic Flood Plain

The channels and active flood plains (encompassing 

78 km2 along the North Fork Sprague, South Fork Sprague, 

main-stem Sprague, and Sycan Rivers) are included in a 

single map unit identified as the Geomorphic Flood Plain. 
Geomorphic Mapping and Geologic History 27

This map unit is the domain of the detailed mapping analysis 

of constructed features, historical channel change, and 

vegetation. It encompasses the area of channels, abandoned 

channels, and scroll-bar topography evident from the 2004 

lidar data. The presence of topographic features indicative of 

channelized flow distinguishes the Geomorphic Flood Plain 

from the Valley Fill unit. Soils typically are poorly drained and 

volcanic-ash-rich Mollisols dominated by the Klamath-OntkoDilman series (Cahoon, 1985). Stratigraphy exposed on 

eroding streambanks and from augering (figs. 5, 8, 9, 11–14) 

show that these flood-plain deposits almost everywhere 

formed after the 7,700 cal yr BP Mazama eruption. In places, 

particularly along the lower Sycan River (Lind, 2009) and the 

North Fork Sprague River, stratigraphic relations show two or 

three episodes of flood-plain erosion and rebuilding over the 

last 6,000 years (figs. 5, 6, 9, 11, 14). As described in more 

detail in subsequent sections, the geomorphic flood plain has 

formed in the last 7,700 years from a combination of channel 

migration, channel avulsion, and lateral and vertical accretion 

of bedload and suspended-load deposits. The geomorphic 

flood plain is mapped on the basis of morphology, soils, and 

stratigraphy, and does not necessarily correspond to a specific 

height above the channel or areas subject to flooding at a 

specific frequency.

About 4,000 cal yr BP sand

Diatomaceous peat

B. NFFK 0.9

Inset, less than 

300-year-old 

flood plain

Section a Section b

300 cal yr BP

 (6/26/07-3a(2))

300 cal yr BP

 (6/26/07-3a(2))

4,330 cal yr BP

 (6/26/07-3b(1))

A. 6/26/07-3; NFFK 0.7

0 5 10 15 20

North Fork Sprague River

1,320

1,319

1,318

Distance from arbitrary datum, in meters

Dominant material Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Gravel

Organic

Primary sedimentary

 structures

Planar lamination

Trough cross bedding

Massive

Horizontal graded beds

River level at time

 of description

EXPLANATION

Radiocarbon 

sample location, 

median age, and 

sample No. 

(appendix B)

Altitude, in meters above North American 

Vertical Datum of 1988

Abbreviation: cal yr BP, 

calendar years before 

present

Figure 11. Late Holocene inset flood-plain deposits at the (A) right-bank exposure at North Fork Sprague River flood-plain 

kilometer (NFFK) 0.7, and (B) left-bank exposure at NFFK 0.9, along North Fork Sprague River, Oregon. Photograph taken by 

J.E. O’Connor, U.S. Geological Survey, September 14, 2007.
28 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig12

0 200 METERS 100

0 600 FEET 300

N 9/22/05-1

9/22/05-2

9/22/05-3

9/22/05-4

September 17, 2006

River Transect 

FK 48.2

FK 48.4

FK 48.6

FK 48.8

FK 49.0

Geomorphic flood-plain boundary

Scroll Bars

1940 Channel

Base map modified from National Agriculture Imagery Programaerial imagery, about 0.5-m resolution, and Watershed Sciences digital data, about1-m resolution. Projection: UTM, Zone 10N, North American Datum of 1983 (NAD 83)

-5 0 5 10 15 20 25 30

1,3071,3061,3051,3041,3031,302

?

?

3,620 cal yr BP (SW-14-01) 3,810 cal yr BP (SW-14-02)

9/22/05-1

0 5 10 15 20 25 30

? ?

1,330 cal yr BP 

(SW-14-04)

1,470 cal yr BP 

(SW-14-05)

9/22/05-2

1,320 cal yr BP 

?

0 5 10 15 20

(SW-14-07)

4,940 cal yr BP (SW-14-08)

1,260 cal yr BP (9/18/06-1(14))

1,260 cal yr BP (9/18/06-1(14))

9/22/05-3

? ?

9/22/05-4, 1940 Channel

0 5 10 15 20 25 30 0 5 10 15 20 25

1,3071,3061,3051,3041,3031,302

2006 Channel

Distance from paleochannel/channel left bank, in meters 

Altitude, in meters above North 

American Vertical Datum of 1988

Clay, silt, fine sand, organic materials (overbank and vertical accretion deposits)Medium to coarse sand, typically pumiceous (point bar and lateral accretion deposits)Gravelly coarse sand and sandy gravel (channel facies)Tertiary lacustrine sediment

Radiocarbon sample location, median age, and sample number (appendix B)

Paleochannel 

Auger transect

EXPLANATION

Base of auger probeUncertain

Direction of flow

?

Abbreviation: cal yr BP, calendar years before present

Figure 12. Former paleochannel locations and augering transects between flood-plain kilometers (FK) 48.2 and 49.0, Buttes of the Gods valley segment, Sprague River study 

area, Oregon. Auger transect 4 crossed the location of the channel as shown in the 1940 aerial photographs. Scroll bars indicate the downstream translation of the 1940 meander loop prior to cutoff.
Geomorphic Mapping and Geologic History 29tac14-0898_fig 13

1,300

1,299

1,298

1,297

1,296

Altitude, in meters above North American Vertical Datum of 19889/15/06-1a

9/20/06-3 9/20/06-4

9/15/06-2 9/15/06-3

Stream crossing

(thalweg)

9/20/06-7

Stream crossing

(thalweg)

Tertiary

lacustrine

sediment

Tertiary lacustrine sediment

Discharge = 5.7 m3/s

Discharge = 6.8 m3/s

9/20/06-1

Altitude interpolated

9/20/06-6

Stream crossing

(thalweg)

Discharge 6.8 m3/s ?

650 cal yr BP (9/20/06-3(4))

1,490 cal yr BP (9/20/06-3(3))

0 250 500 METERS 125

0 750 1,500 FEET 325

Base map modified from National Agriculture Imagery Programaerial imagery, ~0.5-m resolution, and Watershed Sciences digitaldata, ~1-m resolution. Projection: UTM, Zone 10N, Datum: North American Datum of 1983 (NAD 83)

?

Abbreviations: cal yr BP, calendar years before present; m3/s, cubic meters per second.

1,490 cal

yr BP

(9/20/06-3(3))

Clay, silt, fine sand, organic materials (overbank and vertical accretion deposits)Medium to coarse sand, typically pumiceous (point bar and lateral accretion deposits)Gravelly coarse sand and sandy gravel (channel facies)Tertiary lacustrine sediment

Radiocarbon sample location, median age, and sample number (appendix B)

Paleochannel 

Auger transect

EXPLANATION

UncertainDirection of flow

N

Geomorphic flood-plain boundary

FK 30.8

FK 31.0

FK 31.2

FK 31.4

FK 31.6

FK 31.8

FK 32.0

FK 30.6

9/20/06-4

9/20/06-6

9/20/06-3 9/20/06-1

9/20/06-7

9/15/06-1a

9/15/06-2

9/15/06-3

Figure 13. Former paleochannel locations and augering transects between flood-plain kilometers (FK) 30.6 and 32.0, Kamkaun Spring valley segment, Sprague River study area, 

Oregon.
30 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 14

Dominant material Other

Clay and silt

Very-fine to fine sand

Medium to coarse sand

Gravel

Organic

River level at time of description

Radiocarbon sample location, 

median age, and 

sample number (appendix B)

EXPLANATION

1,970 cal yr BP 

(6/25/07-1(3))

cal yr BP Calendar years before present

1,970 cal yr BP 

(6/25/07-1(3))

5,510 cal yr BP 

(6/25/07-2(1))

Irrigated

pasture

Sage, rabbitbrush, and grass

Chokecherry, 

thistle and sage

Willow and 

sedges

Flood chute

Poorly exposed wetland and low

flood-plain deposits

Sycan flood

Obliquely deposited 

beds dipping as much as

20 degrees

2006

gravel 

bar

2006 overbank deposits

Inset, recently

formed flood plain,

probably less

than 600 

years old

Channel and

bar gravel

Channel bottom etched into alternating silt,

clay and pumiceous sand, locally mantled by

lithic pebble gravel

Vertically accreted overbank deposits,

rarely inundated. Formed within last 2,000 years 

Sycan flood 

terrace mantled

by flood-plain

deposits

2006 stage

6/25/07-1

6/25/07-2

1,317

1,316

1,315

1,314

1,313

1,312

Altitude, in meters above North American Vertical Datum of 1988

*Section is not horizontally scaled

Figure 14. Stratigraphic relation among flood-plain and terrace deposits in Lower Sycan valley segment, Sycan River 

flood-plain kilometer 3.5, Sprague River study area, Oregon. Stratigraphy represents exposure along approximately 

300 meters of right channel margin; horizontal axis is not to scale. Sections 6/25/07-1 and 6/25/07-2 are shown in more 

detail in figure 5.

Synopsis of Quaternary Geologic History and 

Sprague River Geomorphology

This mapping and previous geologic studies support 

general inferences regarding the Quaternary geologic history 

of processes and events that have shaped the Sprague River 

and its major tributaries. During the Miocene and Pliocene, 

river networks developing in this area periodically were 

blocked by lava flows and faulting, creating a landscape of 

lakes and rivers. The present Sprague River downstream 

of Beatty Gap developed after the 3.0±0.9 Ma eruption 

of the Basalt of Knot Tableland. Since then, widespread 

lacustrine sedimentation ended and the Sprague River became 

integrated into the Klamath River drainage. This integration 

caused the Sprague River and its major tributaries to incise, 

locally leaving terraces and abandoned and incised alluvial 

fans (Sherrod and Pickthorn, 1992). This regional incision 

probably has not been temporally continuous or spatially 

even, but interrupted by changes in sediment influx and 

transport capacity owing to changes in climate, hillslope 

sediment production, and volcanic sediment influxes. 

This regional incision also has been interrupted by local 

uplift and subsidence associated with block faulting along 

north-northwest to north-northeast trending faults transecting 

the Sprague River course.

Quaternary faulting probably has been a major factor 

affecting the lower 60 km of Sprague River channel, which 

winds across the trends of several fault zones mapped by 

Sherrod and Pickthorn (1992). The prominent steepening of 

the Sprague River at FK 11.4 may owe to uplift and westward 

tilting along two up-to-the-west north-trending normal faults 

at FKs 13.0 and 14.5 in conjunction with subsidence to the 

west of the graben containing Upper Klamath Lake. Tectonic 

blockage associated with these structures between FKs 13.0 

and 14.5 also is consistent with the expansive valley fill 

deposits near Kamkaun Spring and upstream.

Although there is no absolute age information on the 

lowest terraces and abandoned alluvial fans flanking the 

main-stem rivers, their slightly elevated surfaces of as much 

as 2 m higher than the main-stem geomorphic flood plain, 

gravel composition, and capping soils indicate an episode of 

late Pleistocene valley aggradation. Such aggradation would 

be consistent with that found for many valleys in the Western 

United States during and after the last glacial episode of 

20–30 thousand years ago, such as the Willamette Valley of 

western Oregon (O’Connor and others, 2001).

Subsequent to the formation of these terrace surfaces, 

probably during the late Pleistocene, the Sprague River 

and its major tributaries incised as much as 2 m (figs. 4, 8, 

9) in conjunction with forming Holocene flood plains and 
Geomorphic Mapping and Geologic History 31

valley fill. The broad distribution of valley-fill deposits, the 

locally wide geomorphic flood plain, and the wide tributary 

flood plains and fans, however, are all evidence of little or 

no net river incision during the Holocene. The position of 

the 7,700 cal yr BP Mazama tephra in bank exposures and 

auger holes indicates little widespread incision since the 

eruption, although local reaches of the lower Sycan River and 

North Fork Sprague River have had flood-plain erosion 

and deposition episodes over the last 6,000 years (figs. 5, 

9, 11–14).

The 7,700 cal yr BP Mazama eruption greatly affected 

the Sprague River fluvial system. Besides many indirect 

effects on basin hydrology and vegetation from as much as 

1 m of tephra deposition, the large input of sand-size tephra 

to the basin substantially affected flood-plain and channel 

processes and their morphology. The watershed of the Sycan 

River was affected most, being closest to Mount Mazama 

and accumulating the thickest tephra fall. The Sycan flood 

deposited as much as 3.3 m of pumiceous sand during a single 

flood within a few decades or centuries after the eruption, 

forming a broad fan originally encompassing an area of about 

17 km2 with a total sediment volume of 14 million m3 (Lind, 

2009). The Sycan River has incised into the Sycan flood 

deposits (pl. 1) and reestablished a flood plain (figs. 6 and 14), 

but the sandy deposits remains a source of sand-size sediment 

for the Sycan and Sprague Rivers (fig. 7). The large volumes 

of sand-size sediment in the Sycan River transformed the river 

from one with fine-grained cohesive banks and flood plains, 

presumably narrow with slow migration rates, before the 

Mazama eruption (fig. 5), to a more dynamic channel after the 

eruption, laterally migrating in conjunction with formation of 

pumice-rich sandy point bars. Ensuing episodes of flood-plain 

erosion and deposition resulted from changes in local and 

basin-wide sediment supply (Lind, 2009).

The North Fork and South Fork Sprague Rivers also were 

affected by the Mazama fallout tephra. Stratigraphic exposures 

on both forks (figs. 8 and 9) show evidence of organicrich wetland soils capped by pumice-rich, cross-bedded 

sands, which indicates a transformation of wet meadows 

to dynamic sand-bed channels. The stratigraphic exposure 

along the South Fork Sprague River at FK 98.5 (fig. 8) shows 

subsequent transformation back to a wetland environment 

before 20th-century diking and incision. The exposures 

along the North Fork Sprague River (fig. 9) also show 

substantial pumiceous sand deposition in point bars followed 

by transformation to a low-energy wetland environment and 

production of peaty wetland soils.

No exposures along the main-stem Sprague River show 

the character of the channel and flood plain immediately 

prior to the Mazama eruption. Nevertheless, flood-plain 

morphology as well as augering and exposures of late 

Holocene stratigraphy (figs. 8, 12, 13), indicates episodes of 

pumiceous-sand point bar formation associated with lateral 

channel migration and a post-Mazama flood plain much 

sandier than the muddy overbank deposits exposed on low 

Pleistocene terrace deposits (fig. 4). Active point bar deposits 

along the main-stem Sprague River remain largely composed 

of Mazama pumice grains (fig. 15).

A

B

Figure 15. Point bar deposits at survey site 6/23/06-5 with (A) view downstream of partly vegetated point bar mantled 

with coarse sand deposited during 2006 high flows, and (B) 30-centimeter-deep excavation into 2006 high flow deposits 

showing bedded coarse sand composed mainly of pumice grains, Upper Valley segment, Sprague River study area, 

Oregon. Photographs taken by J.E. O’Connor, U.S. Geological Survey, June 23, 2006. Descriptions of survey sites are 

provided in appendix G.
32 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Since the major influx of Mazama tephra following 

the 7,700 cal yr BP eruption and before historical cultural 

modifications to the channels and flood plains, the Sprague 

River and the major tributaries probably were slowly reverting 

to pre-eruption sediment transport and flood-plain building 

conditions, although the large volume of Mazama tephra 

still contributes to abundant sand transport. Evidence from 

stratigraphic exposures and augering transects indicates that 

channels and flood plains had stable altitudes or were slowly 

aggrading as a consequence of channel migration, avulsion, 

flood-plain deposition, and peat accumulation. In conjunction 

with aggrading main-stem flood plains, active geomorphic 

surfaces graded to the flood plain—including flanking 

bottomlands, active tributary fans and flood plains, and 

colluvial slopes—probably also have widened and aggraded 

during the last several thousand years.

Valley Segments

The overall geomorphology of the Sprague River Basin 

and associated valley and flood-plain characteristics provides 

a basis for dividing the main-stem Sprague River corridor 

into nine valley segments. Additionally, the reaches of the 

North Fork Sprague River and South Fork Sprague River 

within the study area each constitute defined valley segments. 

The lower 24 km of the Sycan River has been divided into 

two segments—the steep and confined Coyote Bucket valley 

segment where the river cuts through the Basalt of Knot 

Tableland, and the less confined Lower Sycan valley segment 

downstream to its convergence with the Sprague River 

flood plain.

Distinguishing valley segments provides an analysis 

framework for evaluating conditions and processes relative to 

overarching controls such as slope, confinement, history, and 

materials. If defined valley segments correspond with process 

regimes, segment-specific understanding can enable more 

efficient and targeted management for ecological objectives.

The main criteria for defining valley segments are 

valley confinement, major confluences, and channel slope. 

Current channel and flood-plain morphologic conditions, as 

summarized in the following accounts of individual segments 

(table 2; figs. 16–18), were assessed primarily from mapping 

based on year 2000 aerial photographs and the 2004 lidar data.

Chiloquin Canyon

The Chiloquin Canyon valley segment (fig. 19) extends 

from near the historical Braymill mill to the confluence of 

the Sprague and Williamson Rivers. The town of Chiloquin 

occupies a terrace, of either Sprague or Williamson River 

origin, north of the Sprague River flood plain. The upstream 

end of the valley segment is marked by the substantial 

slope change at FK 11.4, 1.2 km downstream of Braymill at 

FK 12.6 (fig. 17). Most of this segment is tightly confined 

by upfaulted volcanic rocks (fig. 16), resulting in a narrow 

flood plain (mean width 99 m) containing a steep (slope 

0.00195) boulder- and cobble-bed channel (fig. 19). Many 

terrace levels, as high as 45 m, locally flank the flood plain. 

This reach is the steepest of all the main-stem Sprague River 

Valley segments, probably representing local tectonic uplift 

and tilting. The low-flow channel averages 37.8 m in width, 

occupying about 40 percent of the geomorphic flood plain 

(table 2; fig. 18). Channel sinuosity is low at 1.06, as measured 

relative to the flood plain centerline. The flood plain has a 

mixed vegetation cover of herbaceous vegetation, shrubs, and 

ponderosa pine with local cottonwood (Populus sp.) and aspen 

(Populus tremuloides).

tac14-0898_fig 16

Water

Abandoned fans

Tributary flood plains 

 and fans

Colluvium and landslide

Main valley fill

Sycan flood terrace

Terraces

Bedrock

Flood plain

Mapping unit

EXPLANATION

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

Channel length, in meters

Valley segment Council Butte Beatty-Sycan

South Fork

Chiloquin Canyon

Braymill

Kamkaun Spring

S’Ocholis Canyon

Buttes of the Gods

Beatty Gap

Upper Valley

North Fork

Lower Sycan

Figure 16. Geomorphic units within 10 meters of 

primary channel edge for channel location during 2000, 

Sprague River Basin, Oregon.
Valley Segments 33 tac14-0898_fig 17

Altitude, in meters abvoe North 

American Vertical Datum of 1988 Flood-plain width, in meters Sinuosity, 5-kilometer running mean1.6 1.5 1.4 1.3 1.2 1.1

1.0

1,4201,4001,3801,3601,3401,3201,300

0

800600400200

1,2001,000

1.51.41.31.21.11.0

0

800600400200

1,3401,3351,3301,3251,3201,3151,2001,000

1,3401,3201,3001,2801,260

0

500

2,5002,0001,5001,000

3.02.52.01.51.0

0 10 20 0 5 10 0 10 20 30 40 50 60 70 80 90 100 110

Sycan River

flood-plain kilometer

North Fork Sprague River

flood-plain kilometer

Sprague River and South Fork Sprague River flood-plain kilometer

Channel altitude

Chiloquin

90th-percentile flood-plain altitude

Canyon

Braymill Kamkaun

Spring

S’Ocholis 

Canyon

Council Butte

Beatty

Gap

Upper 

Valley

Lower

Sycan

Coyote

Bucket

South

Fork

North

Fork

BeattySycan Buttes of the

Gods

Figure 17. Spatial trends in flood-plain altitude (from 2004 lidar data), flood-plain width, and channel sinuosity (calculated as a 5-kilometer running mean from aerial 

photographs taken in 2000), Sprague River Basin, Oregon.
34 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 18

Sprague River and South Fork Sprague River river kilometer North Fork Sprague

River river kilometer

Sycan River

river kilometer

Chiloquin

Canyon

Braymill Kamkaun

Spring

S’Ocholis 

Canyon

Council Butte Beatty

Gap

Upper 

Valley

South

Fork

BeattySycan Buttes of the

Gods

LowerSycan

Coyote

Bucket

Channel altitude, in meters above Nofth 

American Vertical Datum of 1988 Channel width, in meters Exposed bar width, in meters

0

40

30

2010

0 10 20

0

40302010

0 10 20 30

0

80604020

1,4201,4001,3801,3601,3401,3201,300

50

30

25201510

1,3401,3351,3301,3251,320

1,315

0

40302010

0 20 40 60 80 100 120 140 160

0

80604020

100

1,3401,3201,3001,2801,260

Figure 18. Spatial trends in channel water-surface altitude, channel width, and bar width, Sprague River Basin, Oregon. Width measurements are transects spaced 

200 meters apart along the centerline of the 2000 primary channel as mapped from aerial photographs. Altitude is minimum transect altitude from 2004 lidar grid, which is affected locally by processing artifacts, particularly in the lower North Fork valley segment.
Valley Segments 35

A part of this valley segment is flanked by County 

Highway 858, which locally encroaches onto the flood plain 

between FK 9.5 and 11.4. The channel also was affected by 

Chiloquin Dam at FK 1.3 (fig. 19B), a water supply diversion 

structure constructed in 1914 and removed in August 2008. A 

bridge formerly spanned the flood plain and channel at FK 0.7. 

This valley segment contains USGS streamflow-gaging station 

11501000 (Sprague River near Chiloquin, Oregon), at FK 8.3, 

which has been at this location since 1931, continuously 

operated with a previous location upstream at FK 28.6 since 

1921. An earlier gaging station at about FK 0.7 near the town 

of Chiloquin (fig. 20) had continuous records for the period 

1912–1919, with occasional measurements through 1925 

(USGS Oregon Water Science Center, Portland, Oregon, 

measurement station records for station 11502000, Sprague 

River at Chiloquin, Oregon).

tac14-0898_fig 19

A

B

Figure 19. Chiloquin Canyon valley segment with (A) view 

downstream of bridge crossing at flood-plain kilometer (FK) 8.8

(July 14, 2005), and (B) view upstream across pool behind the 

decommissioned Chiloquin Dam at FK 1.3 (April 3, 2006), Sprague 

River Basin, Oregon. Photographs taken by J.E. O’Connor, U.S. 

Geological Survey.

tac14-0898_fig 20

A

C

B

Figure 20. Historical photographs associated with discontinued 

U.S. Geological Survey (USGS) streamflow-gaging station 

11502000 at flood-plain kilometer (FK) 0.7, with (A) view upstream 

from former wagon bridge crossing of the Sprague River at 

FK 0.7 (May 2 (?), 1918; date not specifically noted, but indicated 

by accompanying notes); (B) view downstream from near 

USGS gaging station (May 6, 1918); bridge visible in upper right 

of image); and (C) view of USGS gage house on right bank of 

Sprague River near Chiloquin, Oregon.
36 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Near the upstream end of the Chiloquin Canyon valley 

segment, Medicine Rock Cave (Archeological site 35KL8; 

near FK 10.9) was noted by Spier (1930, p. 14) near the 

location of the site of the Klamath “First Sucker Ceremony” 

celebrating the annual spring migration of this fish. As noted 

in section, “Sycan Flood Deposits,” this site contained 

evidence of fluvial deposition soon after the Mazama eruption 

(Cressman and others, 1956) that we attribute to the Sycan 

flood. Substantial sucker spawning has been observed in 

recent years between FKs 0 and 1.2 at the lower end of this 

valley segment (Ellsworth and others, 2007).

Braymill

The Braymill valley segment also is a narrow canyon 

segment (fig. 21), but is distinguished from the Chiloquin 

Canyon valley segment by its much flatter gradient—0.00024 

compared to the eight-times-steeper slope of the Chiloquin 

Canyon valley segment (fig. 17, table 2). The Braymill 

valley segment extends 5.8 km from the valley contraction at 

FK 17.2 to the slope inflection at the head of the Chiloquin 

Canyon segment at FK 11.4. Within this reach, the flood 

plain averages 110 m in width and is flanked by bedrock, 

colluvial slopes, narrow flood-plain surfaces, and terraces 

rising 10 m higher than the channel (fig. 16). As with the 

Chiloquin Canyon valley segment, sinuosity is low (1.07) and 

the low-flow channel occupies about one-third of the total 

flood-plain width. Vegetation within the geomorphic flood 

plain also is similar to that of the Chiloquin Canyon segment: 

predominantly herbaceous grasses and forbs, shrubs, and 

ponderosa pine.

The Braymill valley segment is flanked and traversed 

by County Highway 858 and the Williamson River 

Road. County Highway 858 crosses the Sprague River at 

FK 15.5. Outbuildings and mill ponds associated with the 

decommissioned Braymill mill occupy the flood plain between 

FKs 12.5 and 12.6.

Kamkaun Spring

The Kamkaun Spring valley segment (fig. 22) extends 

15.2 km from FK 32.4 at the downstream end of the S’Ocholis 

Canyon valley segment to the head of the Braymill valley 

segment at FK 17.2. This is a sinuous (1.59), low-gradient 

(slope 0.00015) reach with broad flood plains (fig. 17, table 2). 

The channel typically is some distance from valley margins 

(fig. 16). This segment locally is referred to as the “Nine Mile 

reach.” The flood-plain and flanking main-stem valley fill 

are bounded by bedrock uplands and terraces as much as 7 m 

higher than the geomorphic flood plain. The average width of 

the geomorphic flood plain is 500 m (fig. 17), but this area of 

active channel migration for the last several thousand years 

is flanked by broad valleys and basins (chiefly mapped as 

main-stem valley fill; plate 1) that also are inundated during 

the largest floods. The Sprague River meanders through the 

flood plain (which in turn is sinuous) and has left several 

oxbow ponds and abandoned channels. The average channel 

width is about 33.8 m (table 2; fig. 18), and the channel mostly 

flows on sand and gravel, but also in places flows on indurated 

clay and silt locally scoured into several-meter-deep holes 

and chutes. Former fords and irrigation diversions are marked 

by placed rock and coarse gravel accumulations spanning 

the channel. Flood-plain vegetation is composed chiefly of 

herbaceous grasses and forbs, with abundant shrubs and local 

tree-form willows (Salix sp.).

Figure 21. Braymill valley segment looking southwest from 

near flood-plain kilometer 14.5, Sprague River Basin, Oregon. 

Photograph taken by J.E. O’Connor, U.S. Geological Survey, 

July 14, 2005.

Figure 22. Kamkaun Spring valley segment at flood-plain 

kilometer 26.8, Sprague River Basin, Oregon. Photograph taken 

by J.E. O’Connor, U.S. Geological Survey, June 25, 2006.
Valley Segments 37

Several large spring complexes supplement river 

flow in this reach, including those at FKs 32.1 (McCready 

Springs), 30.2 (Kamkaun Spring), 25.5 (Lalo Springs), and 

at Whitehorse Springs, which enters the flood plain from the 

north at FK 22.0. Together, these springs add 1.95 m3/s of flow 

to the Sprague River (Gannett and others, 2007), accounting 

for 12 percent of the annual flow. These spring complexes 

and associated pools and channels that carry flow from the 

springs to the river create diverse aquatic habitats that may be 

important for sucker spawning and rearing, as indicated by 

concentrated adult sucker movement in this reach (Ellsworth 

and others, 2007).

These spring complexes provide a reliable water source 

and inhibit the Sprague River from freezing over, which, 

along with the wide flood plains, have led to a long history of 

settlement in this reach. Archeological sites on terraces and 

hillslopes flanking the flood plain in this reach possibly date 

back to more than 8,000 years ago (Spier, 1930; Cressman and 

others, 1956; Butler and others, 2010). Early homesteaders 

began cattle ranching here at about the time Frank McCready 

settled in 1915 on the peninsula of the terrace jutting into the 

flood plain between FKs 31.9 and 28.7 (Greg Harris, Frank 

McCready’s grandson and present landowner, oral commun., 

September 13, 2007). To enable cattle ranching and flood-plain 

irrigation, diversion dams and ditches were emplaced within 

this reach by the mid-1920s (USGS Oregon Water Science 

Center, Portland, Oregon, measurement station records for 

station 11501000). Construction of the OC&E railroad to Bly 

and concurrent logging also proceeded through this reach in 

the 1920s, with the railroad grade effectively diking parts of 

the flood plain. More systematic levee construction and willow 

eradication began during 1953–54, when the U.S. Army Corps 

of Engineers constructed levees and dikes by excavating 

directly from the channel (Greg Harris, oral commun., 2007). 

More recent channel and flood-plain modifications in this 

segment include filling of meander cutoffs and associated bank 

stabilization, and local levee breaching (fig. 23).

S′Ocholis Canyon

The S’Ocholis Canyon valley segment (fig. 24) 

encompasses 15.8 km of confined canyon and narrow valley 

between the much wider Buttes of the Gods and Kamkaun 

Spring valley segments. Its upstream boundary (FK 48.2) is 

close to the confluence of Trout Creek and the Sprague River 

at FK 48.0. The geomorphic flood plain averages 170 m wide 

and is everywhere less than 500 m wide (table 2; fig. 17). 

The flood plain is flanked mostly by steep bedrock and 

colluvium-mantled hillslopes, low terraces of as much as 5 m 

higher than the active flood plain, and tributary flood plains 

and fans (fig. 16). The flood plain is slightly wider between 

FKs 39.4 and 43.2, where it is confined by low terraces and 

where a large area of main-stem valley fill is contiguous to the 

geomorphic flood plain between FKs 42.3 and 42.6.

tac14-0898_fig 23

Flow

Flow

Plugged cutoff

Figure 23. Filled cutoff channel at flood-plain kilometer 25.3, 

Kamkaun Spring valley segment, Sprague River Basin, Oregon. 

The upstream outside bend of rechannelized meander bend 

(right part of photograph) is protected with rock-anchored 

wood. Photograph taken by J.E. O’Connor, U.S. Geological 

Survey, June 22, 2006.

Figure 24. S’Ocholis Canyon valley segment at flood-plain 

kilometer 34.1, Sprague River Basin, Oregon. Photograph taken 

by J.E. O’Connor, U.S. Geological Survey, July 15, 2006.

Within this valley segment, the channel averages 27.7 m 

in width, has a sinuosity of 1.12, and has a slope of 0.00027—

substantially less sinuous and slightly narrower and steeper 

than the alluvial segments upstream and downstream (table 2, 

fig. 18). The channel bed is composed primarily of sand and 

gravel, locally colonized by dense aquatic growth during 

summer low-flow periods. The flood plain is vegetated with 

herbaceous vegetation and shrubs (including locally thick 

willow patches, particularly in wide reaches), with some 

ponderosa pine and sparse aspen patches.
38 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Human disturbance has had few effects on this reach. A 

rock accumulation associated with an old channel crossing 

forms a low-flow riffle at FK 35.8. Bridges presently span the 

channel at FKs 34.3 and 40.7. County Highway 858 flanks the 

channel and flood plain between FKs 34.3 and 42.3, passing 

through the Lone Pine community on a low terrace north of 

the Sprague River at about FK 40.5. Unpaved forest tracks 

parallel the channel in the confined canyon reaches. Most of 

the flood plain in this valley segment is not actively cultivated, 

but is locally grazed.

Buttes of the Gods

The Buttes of the Gods valley segment (fig. 25) extends 

9.8 km from the town of Sprague River at FK 58.0 to the 

head of the S’Ocholis Canyon segment near the Trout Creek 

confluence at FK 48.2. The upstream segment boundary 

is defined by the valley constriction and change in slope 

(figs. 17, 18) where abandoned fan surfaces sloping from the 

south encroach against the downstream end of the Basalt of 

Knot Tableland and underlying Tertiary lacustrine sediment. 

The expansive flood plain of this valley segment is bound 

by terraces, alluvial fans, and pediments, many of which are 

abandoned and incised (pl. 1). The 2000 channel is within 

10 m of the valley margin for less than 10 percent of its length 

(fig. 16). The highest terraces are as much as 8 m higher than 

the present channel. Large areas of main-stem valley fill, 

possibly inundated at high flows, occupy valleys marginal to 

the geomorphic flood plain. Locally, colluvium descends to 

flood-plain and terrace surfaces from isolated volcanic buttes 

and the broad mesa underlain by the Basalt of Knot Tableland 

north of the Sprague River.

The geomorphic flood plain averages 870 m wide, with 

the channel averaging 35.8 m wide (figs. 17, 18). Channel 

slope for this valley segment is 0.00019, less than that of the 

S’Ocholis Canyon valley segment downstream, but distinctly 

steeper than the upstream Council Butte valley segment. 

Channel sinuosity is 2.01, greatest of all the valley segments 

(table 2). The channel substrate is composed of patchy sand 

and gravel over indurated silt and clay. Ledges of this silt and 

clay locally form small drops at low flow. The induration and 

extensive jointing within the clay and silt indicate that this 

sediment is Tertiary lacustrine sediment rather than Quaternary 

fluvial sediment.

The flood plain for the Buttes of the Gods valley segment 

has very few large trees and just a few, isolated willow 

patches, mainly at the downstream end of the reach between 

FKs 48.2 and 49.7. The flood plain is mostly covered with 

herbaceous vegetation, including irrigated pasture grasses. 

Riparian vegetation mainly is composed of sedges, rushes, and 

riparian grasses. Although few roads and structures occupy the 

flood plain, this valley segment has been extensively modified 

by levees, irrigation ditches, and, historically, diversion 

structures and impoundments associated with flood‐plain 

tac14-0898_fig 25

Figure 25. Buttes of the Gods valley segment looking upstream 

from flood-plain kilometer 49.2, Sprague River Basin, Oregon. 

Photograph taken by J.E. O’Connor, U.S. Geological Survey, 

June 28, 2005.

irrigation as well as lumber mill activities in the town of 

Sprague River. No bridges cross the Sprague River and no 

paved roads are within the geomorphic flood plain of the 

Buttes of the Gods valley segment.

Council Butte

The Council Butte valley segment is another wide 

valley segment (fig. 26) that, together with the Buttes of the 

Gods segment, encompasses most of the area known as the 

Sprague River Valley. The Council Butte segment stretches 

18.8 km from the Sycan River confluence at FK 76.8 to the 

valley constriction and distinct channel-slope increase at 

FK 58.0, coinciding with the town of Sprague River and the 

crossing of the Sprague River by the Sprague River Road. 

The geomorphic flood plain averages 840 m in width, but 

narrows substantially near Council Butte (at FK 66.4) and near 

the downstream end of the valley segment where it locally is 

less than 100 m wide (fig. 17).

For much of its length, the 70-m-high mesa underlain 

by the Basalt of Knot Tableland and southward-descending 

colluvial slopes and tributary fans border the north side of 

the flood plain. The geomorphic flood plain is bounded on 

the south by main-stem valley fill, low terraces, active and 

abandoned alluvial fans, and locally by colluvial slopes and 

bedrock associated with Council Butte and other bedrock 

uplands. Incised fans emanating from Bly Mountain and 

surrounding uplands encroach upon the flood plain at the 

west end of the valley segment, narrowing the flood plain. 

The upstream end of this segment abuts the Sycan River flood 

plain as well as pumice-rich deposits of the Sycan flood.

The channel within the Council Butte valley segment 

averages 35.0 m in width, is sinuous (1.70), and has a gradient 

of 0.00015, which, along with the similarly low-gradient 

Kamkaun Spring valley segment, is the flattest in the study 
Valley Segments 39

tac14-0898_fig 26

Figure 26. Council Butte valley segment looking upstream from 

near flood-plain kilometer 59.2, Sprague River Basin, Oregon. 

Photograph taken by J.E. O’Connor, U.S. Geological Survey, 

September 16, 2006.

area (table 2; figs. 17, 18). The channel substrate varies 

from mainly sand with sparse gravel near the Sycan River 

confluence with the Sprague River to patchy sand over mud 

and clay at the downstream end of the reach. Except for a 

rocky ford that spans the channel at FK 76.3, there is little 

gravel in the channel or banks. At low flow, velocity is slow 

and the channel is rimmed by dense sedge-rush communities, 

and locally by several large wapato (Sagittaria cuneata) 

colonies. The flood plain is treeless, has very few shrubs, and 

is vegetated mainly by pasture grass that is irrigated in places. 

Levees, dikes, and dry flood-plain patches are vegetated with 

sagebrush and grass.

The Council Butte valley segment has been modified 

extensively by ditches, levees, bank protection, and farm road 

construction. The total length of such features in 2000 was 

76.3 km, most of which were constructed during 1940–68 

(table 6). The railroad grade, constructed in the 1920s, locally 

encroaches onto the southern edge of the geomorphic flood 

plain and flanking main-stem valley fill. Since the 1990s, 

as part of channel restoration efforts, meander cutoffs and 

secondary channels have been plugged and armored with rock 

and large wood near FKs 61.4 and 76.2.

Beatty-Sycan

The Beatty-Sycan valley segment (fig. 27) is a short reach 

extending 4.2 km from the downstream end of Beatty Gap 

at FK 81.0 to the Sycan River confluence with the Sprague 

River at FK 76.8. Like the two downstream segments, this 

is a wide and unconfined reach containing a sinuous (1.68) 

Sprague River. This segment constitutes the upper part of the 

Sprague River Valley. The geomorphic flood plain averages 

910 m wide (table 2, fig. 17) and is mostly bounded by 

main-stem valley fill that probably is inundated during large 

floods, as well as active and incised tributary fans and flood 

plains. The valley of Brown Creek enters from the south at 

FK 80.7, adjacent to the large spring complex known locally 

as Medicine Springs, which contributes about 0.4 m3/s of 

flow to the Sprague River (Gannett and others, 2007). In total, 

springs in the upper part of this valley segment add about 

1.6 m3/s of flow to the Sprague River (Gannett and others, 

2007), thereby augmenting the annual flow by 18 percent from 

that measured just upstream at Beatty Gap (streamflow gaging 

station 11497500).

In this valley segment, the channel chiefly is flanked 

by flood-plain deposits, averages 29.4 m in width, and 

has a slope of 0.00021 (table 2; figs. 18, 16). The channel 

substrate mostly is sand but locally is muddy. During the 

June 26, 2006 canoe reconnaissance of this reach, abundant 

freshwater mussels were noted in the channel bed near FK 

79.2 (which subsequently has been filled and relocated as a 

part of channel-restoration activities). The channel margin 

mostly is vegetated with sedges, rushes, and some grasses. 

Willow clumps have grown on a few point bars and along the 

edges of former channel routes. Otherwise, the flood plain is 

vegetated with pasture grass, with dry parts hosting sagebrush 

and xeric grasses.

As with most of the other wide valley segments, the 

Beatty-Sycan valley segment has been modified by ditches 

and levees, although the density of such features, particularly 

levees, is less in this reach than the other wide valley 

segments. Godawa Springs Road crosses the Sprague River 

and the flood plain at FK 78.0. The flood plain is flanked and 

crossed at FK 80.9 by the OC&E railroad grade, and crossed 

by the Woods Line branch at FK 80.6, where the trestle 

bridge effectively traps most wood from upstream. Channel 

restoration projects during 2006–08 filled three channel cutoffs 

and excavated a new channel near FK 78.8–79.4.

tac14-0898_fig 27

Figure 27. Beatty-Sycan valley segment looking northwest 

(upstream) from flood-plain kilometer 78.5, Sprague River Basin, 

Oregon. Photograph taken by J.E. O’Connor, U.S. Geological 

Survey, June 26, 2006.
40 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Table 6. Mapped built features in the Sprague River geomorphic flood plain, Oregon.

[Abbreviations: km, kilometer; ha, hectare]

Valley

segment

Ditches

(km)

Dikes and 

levees

(km)

Roads

(km)

1940 1968 2000 1940 1968 2000 1940 1968 2000

Chiloquin Canyon 1.0 1.0 0.0 0.3 0.0 0.6 2.5 0.4 0.7

Braymill 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.2 0.2

Kamkaun Spring 1.7 30.5 31.6 0.1 4.1 9.0 0.0 0.7 2.1

S’Ocholis Canyon 0.0 10.0 1.2 0.0 0.5 0.2 2.2 1.8 2.9

Buttes of the Gods 2.8 16.7 34.7 1.9 13.1 16.9 0.1 1.4 0.9

Council Butte 0.3 31.5 42.7 0.0 19.0 25.6 1.9 3.0 8.0

Beatty-Sycan 0.0 5.8 12.2 0.0 0.0 0.6 3.1 4.0 2.8

Beatty Gap 0.0 0.0 0.0 0.0 0.0 0.0 1.0 1.1 1.9

Upper Valley 1.2 24.3 23.5 0.0 8.1 8.1 0.0 0.3 0.3

South Fork 11.1 126.3 123.7 10.0 58.8 81.1 11.2 8.6 7.2

North Fork 13.9 21.7 22.7 10.0 5.6 8.9 11.8 3.2 3.8

Lower Sycan 0.0 4.7 2.3 0.0 0.0 0.5 0.9 2.0 1.3

Study Area 111.9 272.3 294.6 12.2 109.3 151.5 114.9 26.8 32.0

Valley

segment

Dams and 

diversion 

structures

(number)

Buildings and 

structures

(number)

Total 

built area

(ha)

1940 1968 2000 1940 1968 2000 1940 1968 2000

Chiloquin Canyon 1 1 1 1 4 1 2.1 1.0 0.7

Braymill 0 0 0 3 3 3 0.4 0.3 0.3

Kamkaun Spring 0 0 2 0 0 1 0.3 7.1 11.0

S’Ocholis Canyon 0 0 0 0 0 0 1.1 1.9 1.7

Buttes of the Gods 10 13 19 3 1 3 2.2 13.9 18.2

Council Butte 1 11 11 5 0 1 1.5 26.5 36.0

Beatty-Sycan 0 0 0 0 3 5 2.6 4.3 4.5

Beatty Gap 0 0 0 0 0 0 0.8 0.7 1.1

Upper Valley 0 0 0 0 0 0 0.1 11.5 11.3

South Fork 10 110 69 10 1 0 19.8 81.1 101.3

North Fork 10 17 17 15 2 4 132.0 8.9 12.8

Lower Sycan 0 1 25 0 0 1 1.0 2.5 2.0

Study Area 112 153 144 117 14 19 1162.8 159.7 200.9

1

Aerial photograph coverage incomplete.

Beatty Gap

The Beatty Gap segment encompasses the canyon 

between FKs 89.6 and 81.0 where the Sprague River flows 

between Ferguson and Medicine Mountains. The geomorphic 

flood plain is narrow, averaging 240 m wide (table 2, 

fig. 17), and is flanked by bedrock, colluvial slopes, small 

tributary fans and terraces of as much as 5 m higher than the 

modern channel. The channel in this segment averages only 

17.3 m in width, about 60 percent the width of downstream 

Beatty-Sycan valley segment, and has a slightly steeper slope 

of 0.00024 compared to the Beatty-Sycan valley segment 

(table 2). Unlike the other canyon segments where sinuosity is 

less than 1.1, the Sprague River meanders through Beatty Gap 

with a sinuosity of 1.39. The channel substrate mainly is sand, 

but locally contains gravel and cobbles, particularly where 

the channel is close to bedrock or colluvial slopes. In places, 

sand and gravel are thin or patchy on a clay bed. Locally, 

live freshwater mussels inhabited the channel bed during the 

June 2006 survey.

The flood plain has abundant shrub and tree cover, 

including willow, aspen, currant (Ribes L.), and rose (Rosa L.; 

fig. 28). Slightly higher and more xeric flood-plain surfaces 

are vegetated with sagebrush, rabbitbrush (Chrysothamnus 

Nutt.), and grasses. The channel margin and flanking point 

bars are vegetated with grasses, sedges, rushes, and common 

reed canarygrass. Wood accumulations, including some large 

ponderosa pine boles originating on adjacent hillslopes, locally 

flank and span the channel.
Valley Segments 41

tac14-0898_fig 28

Figure 28. Beatty Gap valley segment looking west 

(downstream) from flood-plain kilometer 85.2, Sprague River 

Basin, Oregon. Photograph taken by J.E. O’Connor, U.S. 

Geological Survey, June 26, 2006.

Flow has been measured in the Beatty Gap valley 

segment episodically since about 1904, but more continuously 

since 1912 by the USGS and then the OWRD (figs. 2, 3; 

USGS Oregon Water Science Center, Portland, Oregon, 

streamflow-gaging station records). Records from these 

stations and additional measurements and observations show 

that several springs supplement flow through Beatty Gap. 

Gannett and others (2007) reported 0.73 m3/s of spring inflow 

between the long-term Beatty Gap gaging station at FK 81.4 

and near the 1912 gaging station at FK 84.2. However, 

additional springs upstream, including significant inflow at 

FK 85.0 and just upstream of the upstream segment boundary 

at FK 89.6, may contribute a similar volume, thereby 

accounting for nearly all the gain in flow estimated by Gannett 

and others (2007) for the upper Sprague River. The spring 

flow in this reach, as well as the spring flow at Medicine 

Springs near the downstream end of this valley segment, may 

have attracted early Native American settlement dating back 

8,000 years (Jenkins and Connelly, 2007)—settlement that 

was sustained partly by Chinook and steelhead salmon (Butler 

and others, 2010). Spring flow in this reach also may be partly 

responsible for the present high levels of adult sucker activity 

(Ellsworth and others, 2007).

The Beatty Gap valley segment has few diversions, 

ditches, and levees. It is crossed by a private bridge at FK 89.3 

and a concrete bridge along the OC&E railroad grade at 

FK 87.7. Historically, a wagon road and later a highway 

crossing spanned the river at FK 81.5 (fig. 29). State Highway 

140 traverses the southern edge of the flood plain, and the 

occidentalis), and transmission towers. Source of figure 29A: 

Bureau of Reclamation, Klamath Waters Digital Library; http://

digitallib.oit.edu/cdm/singleitem/collection/kwl/id/522/rec/5, 

accessed February 11, 2012). Figure 29B taken by J.E. O’Connor, 

U.S. Geological Survey.

railroad grade and a private road flank parts of the northern 

flood-plain boundary. For most of the reach, however, these 

roadways do not significantly encroach upon the geomorphic 

flood plain, except for the upstream and downstream ends, 

where the railroad grade crosses and traverses the flood plain.

tac14-0898_fig 29

B

A

Figure 29. Approximately matched locations at flood-plain 

kilometer 81.4 near the downstream end of the Beatty Gap valley 

segment, Sprague River Basin, Oregon. (A) Former Beatty Bridge, 

photograph probably taken May 21, 1904, during establishment 

of streamflow-gaging station near present site of Oregon Water 

Resources Department station 11497500. (B) Photograph taken 

close to the same location on June 29, 2007, showing increase 

of riparian willow (Salix sp.), hillslope juniper (Juniperus 
42 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Upper Valley

The Upper Valley segment (fig. 30) extends 3.6 km from 

the confluence of the North Fork and South Fork Sprague 

Rivers at FK 93.2 to the entrance of Beatty Gap at FK 89.6. 

This is a wide valley segment, with the flood plain averaging 

1,280 m wide. The geomorphic flood plain mainly is flanked 

by active tributary fans, colluvial slopes, and low terrace 

deposits. The channel winds through the flood plain with an 

average width of 17.8 m and a sinuosity of 1.37, and rarely 

encroaches the valley margins (table 2; figs. 16, 18). Channel 

slope for the Upper Valley segment (0.00033) is higher than 

for any main-stem Sprague River valley segment except for 

Chiloquin Canyon. The channel substrate chiefly is sand with 

local gravel accumulations. In places, the sand and gravel are 

patchy on top of indurated silt and clay. Many live freshwater 

mussels were colonizing the channel bed during the June 23, 

2006, canoe reconnaissance.

Willow clumps locally flank the present channel as well 

as swales marking former channel locations, particularly 

between FKs 89.6 and 91.0. Otherwise, the channel corridor 

is vegetated with rushes, sedges, and reed canarygrass. The 

flood plain mainly is vegetated with pasture grasses, sage, 

and rabbitbrush.

Levees bound the channel on the north from FKs 89.7 to 

92.3, and on the south from FKs 92.3 to 93.2. The flood plain 

also has many ditches and diversions and is locally leveled. 

The railroad grade flanks the southern margin of the channel, 

but mostly is outside the geomorphic flood plain.

Figure 30. Upper Valley segment looking downstream from 

flood-plain kilometer 88.5, Sprague River Basin, Oregon. 

Photograph taken by J.E. O’Connor, U.S. Geological Survey, 

June 23, 2006.

South Fork

The South Fork valley segment (fig. 31) spans 13.1 km 

from FK 106.3, 5.7 km east-southeast of Bly, to FK 93.2, 

at the confluence of the South Fork Sprague River with the 

North Fork Sprague River. This segment encompasses the 

broad alluvial valley from where the river leaves the uplands 

dividing the Sprague River Basin from those basins to the 

east. The geomorphic flood plain is flanked by active and 

A

B

Figure 31. South Fork valley segment looking (A) downstream 

from Ivory Pine Road bridge crossing at flood-plain kilometer 

(FK) 94.3 (March 9, 2004); and (B) upstream from diversion at FK 98.6 

(June 20, 2007), Sprague River Basin, Oregon. Photographs taken by 

J.E. O’Connor, U.S. Geological Survey.
Valley Segments 43

abandoned tributary fans, tributary flood plains, and colluvial 

slopes, and by bedrock in upstream stretches. Fishhole Creek 

and Paradise Creek enter the flood plain from the south, 

and Deming Creek enters the flood plain from the north. 

Within this segment, the geomorphic flood plain is as wide 

as 2,500 m and averages 1,650 m in width, the widest of 

any valley segment in the study area (table 2; fig. 17). The 

channel only is locally close to the valley margin (fig. 16). 

The South Fork Sprague River is part of the geomorphically 

continuous east-west trending valley of the Sprague River; 

therefore, longitudinal plots in this report showing channel and 

flood-plain measurements join the main-stem and South Fork 

Sprague River measurements.

Average channel width for the South Fork valley segment 

is 10.5 m, the narrowest of the study area, and the segment 

has a sinuosity of 1.17, the lowest of any of the unconfined 

valley segments (table 2). The channel substrate has not been 

systematically evaluated, but at the upstream end of the reach 

it is cobbly sand and gravel. Downstream in the alluvial basin, 

substrate chiefly is indurated silt and clay with patchy sand 

and gravel. Channel slope averages 0.00100 for the entire 

segment, but decreases from 0.003 at the upstream end of the 

reach to about 0.0003 at the downstream end. The channel is 

interrupted by diversions at FKs 100.0 and 101.4, which both 

create 2-m steps in the longitudinal profile (fig. 32).

The flood plain of this valley segment has been the most 

modified of all segments in the study area. More than 200 km 

of ditches and levees constrain and divert the channel and 

overbank flow. Between FKs 93.2 and 101.6, the channel has 

levees on both sides, everywhere less than 100 m apart. The 

channel itself has been straightened, particularly between 

FKs 97.0 and 101.0 (fig. 31B). In these reaches, levee material 

likely was excavated from the channel. Much of the area of the 

geomorphic flood plain outside the leveed-channel area has 

been leveled and is lined with irrigation ditches. Two paved 

roads, Ivory Pines Road at FK 94.3 and Campbell Road at 

FK 101.4, as well as the railroad grade at FK 104.2, cross the 

flood plain and South Fork Sprague River. A private farm road 

bridges the river at FK 98.6.

The USGS measured streamflow on the South Fork 

Sprague River at the upstream end of the valley segment 

(near FK 106.2) during 1925–26 (USGS Oregon Water 

Science Center, Portland, Oregon, measurement records for 

station 11495500). More recently, Oregon Department of 

Water Resources has monitored flow near FK 98.6 (South 

Fork Sprague River downstream of Fishhole Creek near Bly; 

11495600). Mean annual flow for WY 2010 (the only recent 

complete year of flow measurements) was 1.22 m3/s.

North Fork

A single segment encompasses the alluvial portion of the 

North Fork Sprague River downstream from its emergence 

from the forested southwestern slopes of Gearhart Mountain. 

tac14-0898_fig 32

South Fork Sprague River

North Fork Sprague River

EXPLANATION

0 2 4 6 8 10 12 14 16

1,315

1,320

1,325

1,330

1,335

1,340

Distance, in kilometers from North Fork and

South Fork Sprague River confluence

Altitude, in meters above North American Vertical Datum of 1988

Diversion at

NFFK 1.1 

Diversion at

FK 100.0

Campbell Road

Bridge FK 101.4

Diversion at

NFFK 9.0

Ivory Pine Road

Bridge NFFK 5.2

Confluence at FK 93.1

Fishhole Creek

Figure 32. Approximate water-surface profiles 

from 1-meter spacing lidar data along 2004 channel 

centerlines, North Fork and South Fork Sprague Rivers, 

Oregon. Some of the high-frequency variability is from 

processing artifacts, but major discontinuities and 

slope changes represent actual channel conditions. 

FK, flood-plain kilometer; NFFK, north Fork Sprague 

River flood-plain kilometer. Locally, the channel 

margins are vegetated with sedges, rushes, and reed 

canarygrass. The flood plain is vegetated with grass 

(much of it irrigated), with dry parts growing sagebrush, 

rabbitbrush, and upland grasses. A few willows line 

the channel in the upstream part of the valley segment 

between FKs 104.0 and 106.3.

This valley segment includes 9.8 km of North Fork Sprague 

River flood plain outside the main-stem and South Fork Sprague 

River flood plain (thereby excluding the lower 1.9 km of the 

lower North Fork Sprague River channel). The North Fork 

Sprague River is joined by Meryl Creek at North Fork Sprague 

River flood-plain kilometer (NFFK) 4.8 and by Fivemile Creek 

at NFFK 1.7. The flood-plain width ranges from 90 m to nearly 

1,200 m (average 530 m), and is flanked by bedrock, colluvial 

slopes, and active tributary fans and flood plains.

The North Fork Sprague River winds through the North 

Fork valley segment with a sinuosity of 1.39 and an average 

width of 11 m (table 2). Channel slope averages 0.00124, but it 

declines from 0.004 at the upstream end of the valley segment 

to 0.0004 near the South Fork Sprague River confluence. 
44 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

The channel substrate for the North Fork valley segment 

was not systematically investigated, but at NFFK 5.2, near 

the crossing of Ivory Pine Road, the channel has a cobblegravel bed, with some of the rock apparently placed to inhibit 

erosion. Farther downstream, at NFFK 3.7, the channel 

substrate is sand and gravel formed into pool-riffle sequences, 

and at NFFK 0.7, near the Campbell Road crossing, the bed 

is indurated silt and clay with patches of sand. A 1-m-high 

rock and timber diversion structure crosses the channel at 

NFFK 1.1 (fig. 32).

Low surfaces and bars near the channel are vegetated 

with rushes and sedges. Flood plains are vegetated with 

sagebrush, rabbitbrush, and grass. Some higher flood-plain 

surfaces are more than 3 m higher than the low-flow water 

surface and are densely vegetated with sagebrush and 

rabbitbrush (fig. 11). Sparse mature willows flank the channel 

near NFFK 2.1 and between NFFK 3.8 and 5.1.

For periods between 1917 and 1925, the USGS 

maintained a streamflow-gaging station at the upstream end 

of the reach near NFFK 9.4, but records are not sufficient 

to determine average annual flow (USGS Oregon Water 

Science Center, Portland, Oregon, measurement records for 

station 11496500, North Fork Sprague River near Bly). From 

various records, Gannett and others (2007) reported a total 

groundwater discharge to the North Fork Sprague River of 

2.6 m3/s, of which about 0.93 m3/s are contributed by springfed Meryl and Fivemile Creeks.

The North Fork valley segment also has many levees, 

diversions, and road crossings. Since at least 1904, as much 

as 0.7 m3/s of flow has been diverted from the North Fork 

Sprague River upstream of the study area to the South Fork 

valley segment by the Sprague River Irrigation Company 

(Kent, 1905; USGS Oregon Water Science Center, Portland, 

Oregon, measurement records for station 11496000). At least 

two local diversions also support nearby flood-plain irrigation 

(fig. 32). The channel is flanked locally by 8.9 km of levees, 

many of which protect areas of leveled and irrigated flood 

plain. Roads and bridges cross the flood plain and channel at 

NFFK 0.7, 3.7, and 5.4.

Lower Sycan

The Lower Sycan valley segment (fig. 33) encompasses 

the Sycan River valley bottom from near where it leaves 

Sycan Canyon to the Sycan River confluence with the Sprague 

River. This valley segment is 10.6 km long (table 2), not 

including the 0.75-km-long traverse across the Sprague River 

flood plain at the confluence of the Sycan and Sprague Rivers. 

Flood-plain width generally increases downstream, from 

less than 200 m near the downstream end of Sycan Canyon, 

to more than 1,000 m as the Sycan River flood plain joins 

the Sprague River flood plain. The Sycan River flood plain 

is adjacent to Sycan flood deposits for much of its length, 

but is locally also flanked by bedrock, active and abandoned 

tributary fan deposits, terraces, colluvial slopes, and spring 

deposits (figs. 7, 16). Snake Creek joins the Sycan River at 

Sycan River flood-plain kilometer (SYFK) 2.4.

The Sycan River channel averages 16.9 m wide, has a 

sinuosity of 1.38, and is flanked by abundant bars, mainly 

composed of sand (table 2; figs. 17, 18, 33). Channel substrate 

ranges from mostly gravel at the upstream end of the reach to 

sand and gravel patches partly covering indurated silt and clay, 

probably Tertiary lacustrine sediment, at the lower end of the 

reach (fig. 34).

Figure 33. Lower Sycan valley segment looking downstream 

from Sycan River flood-plain kilometer 10.7, Sprague River Basin, 

Oregon. Photograph taken by J.E. O’Connor, U.S. Geological 

Survey, June 30, 2005.

Figure 34. Sycan River flowing on Tertiary lacustrine sediment 

at Sycan River flood-plain kilometer 1.2 in the Lower Sycan valley 

segment, Sprague River Basin, Oregon. Photograph taken by J.E. 

O’Connor, U.S. Geological Survey, June 22, 2007.
Channel and Flood-Plain Conditions and Processes 45

Channel margins and low flood-plain surfaces are locally 

vegetated with sedges and rushes, with abundant shrub cover 

(including willow, rose, and currant) along former channel 

paths (fig. 33) and taller stream banks. Higher flood-plain 

surfaces mainly are vegetated with sagebrush, rabbitbrush, and 

upland grasses.

Springs contribute flow by way of Snake Creek at SYFK 

2.4, Brown Spring at SYFK 3.7, and many unnamed springs 

between SYFK 6.6 and 11.2. Total spring flow in this reach is 

about 0.14 m3/s, contributing about 24 percent of the groundwater discharge (and total base flow) to the Sycan River 

downstream of Sycan Marsh (Gannett and others, 2007). 

Streamflow has been measured discontinuously on the Sycan 

River within this reach since 1912 (USGS Oregon Water 

Science Center, Portland, Oregon, measurement records for 

station 11499000, Sycan River near Beatty). For the OWRD 

streamflow-gaging station 11499100 at the Drews Road 

crossing at SYFK 2.2, mean annual flow for 1973–2010 was 

4.22 m3/s (fig. 2).

The Lower Sycan valley segment has few ditches, levees, 

and roads on the active main-stem flood plain, totaling only 

4.1 km (table 6). Spring diversions provide for water storage 

and irrigation. A few small areas of the flood plain have been 

leveled. The flood plain is crossed by Drews Road, which 

crosses the Sycan River at SYFK 2.2. The Sycan River 

channel abuts Godowa Springs Road at SYFK 0.3, where rip 

rap protects the road alignment from channel migration.

Coyote Bucket

The Coyote Bucket valley segment (fig. 35) includes 

13.4 km of the Sycan River corridor through the lower and 

steepest part of the Sycan Canyon, from the downstream end 

of Teddy Powers Meadows at SYFK 24.0 to the downstream 

end of the canyon at SYFK 10.6. Because aerial photography 

and lidar coverage is limited to downstream of SYFK 15.4, 

mapping and analysis is complete only for the lower part 

of this valley segment. For the entire segment length, mean 

flood-plain width is 60 m (table 2); the narrowest of any 

segment in the study area, and is almost everywhere confined 

by bedrock or colluvium. The lower part of the segment, 

from near the confluence of Blue Creek at SYFK 13.4 to the 

downstream end of the canyon at SYFK 10.6, is narrowest 

and steepest, corresponding to where the river cuts through 

the Basalt of Knot Tableland. Two small rockfall landslides 

encroach upon the channel in this reach.

For the lowermost 4.6 km of this reach (the part within 

lidar coverage), average channel slope is 0.01794, nearly 

10 times steeper than the average channel slope of any other 

study reach (table 2). The channel bed is formed mostly 

of basalt boulders that have fallen from the canyon edges. 

The channel is confined largely by this coarse material, and 

sinuosity is a low 1.04. Four-wheel-drive tracks approach and 

parallel the river in a few locations, but otherwise this reach is 

unaffected by ditches, diversions, and levees.

tac14-0898_fig 35

Figure 35. Coyote Bucket valley segment of the Sycan River 

looking downstream from near Sycan River flood-plain kilometer 

13.2, Sprague River Basin, Oregon. Photograph taken by 

J.E. O’Connor, U.S. Geological Survey, June 24, 2006.

Channel and Flood-Plain 

Conditions and Processes

This section outlines key morphologic attributes of 

the Sprague River channel and flood plain, and how these 

attributes have changed at time scales encompassing the last 

century to the last several thousand years. These morphologic 

characteristics relate, in turn, to past and present processes of 

channel and flood-plain formation.

Historical data used in mapping and quantitative analysis 

of channel and flood-plain conditions mainly were from the 

cadastral surveys, aerial photographs, and lidar (table 4). 

Sediment transport measurements and a survey of effects 

of the 2006 high flow provide evidence of key processes 

presently affecting channels and flood plains. The augering 

transects and analysis of stratigraphic exposures (appendix C) 

provides information on flood-plain stratigraphy and channel 

position and processes over the last several thousand years, 

pre-dating substantial human flood-plain and channel 

alteration. Methods for analysis build upon previous studies 

of rivers in the Pacific Northwest, including the Queets and 

Quinault Rivers of western Washington (O’Connor and others, 

2003c), the Deschutes River of central Oregon (O’Connor and 

others, 2003a), the Umatilla River of eastern Oregon (Hughes 

and others, 2006), and the Umpqua River of western Oregon 

(Wallick and others, 2011).
46 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Historical Modification

Much of the analysis of status and trends for the channels 

and flood plains of the Sprague and lower Sycan Rivers stems 

from maps, photographs, and observations from the 1860s 

through 2010 (table 4). This period, however, coincides with 

the main period of human manipulation of the channel and 

flood plain for purposes such as agriculture, water supply and 

delivery, transportation infrastructure, flood protection, and 

channel and flood-plain habitat restoration. Therefore, analyses 

and observations are affected partly by these human-caused 

changes to the system, prompting this description of the major 

historical changes.

Early Observations of Flood-Plain and 

Channel Conditions

The earliest systematic descriptions of the study area 

were recorded in the maps and notes from General Land 

Office cadastral surveys (table 3). The maps and notes 

provide information on channel width and position as well 

as vegetation. Summary observations from the field notes 

accompanying GLO surveys have been transcribed onto 

modern USGS topographic quadrangles by the Oregon 

Institute of Technology and Shaw Historical Libraries (2011). 

These observations, spanning 1866–1892, typically describe 

the geomorphic flood plain of the wider valley segments as 

“land-level; soil-1st rate.” Many of these wider flood plain 

areas also are described as “prairie.” Unique among the 

wide flood-plain segments was the observation of extensive 

wetlands and marshes in the Upper Valley during the 

September 1866 survey of T36S-R14E. Here, several section 

corners between FK 96.9 and FK 94.3, just upstream of the 

North Fork confluence, were described in surveyor notes as 

“swampy.” Wetlands also were shown on the corresponding 

plat map for parts of sections 16, 17, 20, 21, 22, 27, and 28. 

The GLO descriptions for the confined segments mainly 

note the rocky and forested terrains flanking the narrow 

flood plains.

These early GLO descriptions are in accord with 

subsequent maps and observations. A USGS land classification 

and timber survey encompassing the Klamath Quadrangle 

includes the study area downstream of FK 92 (Leiberg, 

1903), showing most of the Sprague Valley as “non-forested 

as marshes, meadows and agricultural lands,” and, near 

the town of Sprague River, “bottom lands, mostly grass 

covered, bordering Sprague River...” (p. 416). Similarly, a 

preliminary report on water resources for the Klamath Indian 

Reservation (Henshaw, 1912) and the field notes of botanist 

W.E. Lawrence summarizing observations in July 1922 

and July 1934 (W.E. Lawrence, Oregon State University 

Herbarium, Corvallis, Oregon, unpublished field journals), 

show extensive and untimbered bottomlands flanking the 

Sprague River.

Early USGS records of streamflow measurements and 

related activities also provide information on channel and 

flow conditions and document the effects of diversions and 

log-driving activities on the Sprague River (U.S. Geological 

Survey, Oregon Water Science Center, Portland, Oregon, 

streamflow-gaging station records). In particular, channel 

conditions dating back to 1904, with extensive accounts for 

the period between 1912 and 1930, are contained in station 

notes and photographs for USGS streamflow measurement 

sites on the South Fork Sprague River near Bly, North Fork 

Sprague River near Bly, Fivemile Creek near Bly, Sprague 

River near Beatty, Sycan River near Beatty, and Sprague 

River near Chiloquin. Observations for the 1920s along 

the South Fork Sprague River (station 11495500) included 

accounts of “hardpacked gravel” substrate and that “willows 

may affect extremely high water.” Likewise, for the North 

Fork Sprague River (station 11496500), station notes for 

May 18, 1925 report the “Channel very crooked near gage; 

no well [de]fined control...Willows on banks, left bank 

low...” Similarly at Fivemile Creek (station 11497000), “A 

crooked channel lined with a thick growth of alders was not 

conducive to a stable stage-discharge relationship for the site 

used 11 September 1917, to 11 May 1919...The pumice sand 

composition of the soil also contributed to constantly shifting 

conditions.” 

In the Beatty Gap area, 1912 reconnaissance notes by 

H. Kimble record that “The Sprague River from its forks near 

the eastern Indian Reservation line [near FK 93.0] westward 

to mouth of Sycan R. flows in a very deep channel and at 

very sluggish velocity and has many stagnant bychannels” 

(USGS Oregon Water Science Center, Portland, Oregon, 

streamflow-gaging station records; station 11497500, 

Sprague River near Beatty). Several early 20th-century 

accounts indicate mobile channel conditions and sand and 

gravel substrate for the Sycan River (Station IDs 11499000, 

11499100), as well as measurements affected by thick 

late-summer aquatic growth.

For the Sprague River within the Kamkaun Spring reach, 

station records for streamflow-gaging station 11501000, 

located at FK 28.6 between July 1920 and September 30, 

1931, note that “Current sluggish everywhere; right bank well 

defined and high, left bank rather low, and some willows; 

bottom of hard pan overlain with pumice sand, probably 

shifting very slowly” (U.S. Geological Survey, Oregon Water 

Science Center, Portland, Oregon, streamflow-gaging station 

records). Additionally, records for this location summarize 

some of the alterations to the Sprague River associated with 

early European settlement that ultimately forced relocation of 

the station. These include construction of the OC&E Railroad, 

the 1926 construction of a diversion dam 2 km downstream 

at FK 27.2, upstream diversion dams affecting flow as early 

as 1920, sudden flow fluctuations caused by operation of 

upstream regulating dams, and frequent log drives (fig. 20) 

that apparently led to many log jams (USGS measurement 

station records for station 11501000).
Channel and Flood-Plain Conditions and Processes 47

Evidence for changing beaver, otter, and muskrat 

population was noted by some of the early streamflow 

measurement station records as well as a 1943 wildlife 

resource report on the Klamath Reservation by A.W. Moore 

(unpub. wildlife resource report by 1943, U.S. Fish and 

Wildlife Service, in Klamath Indian Agency records, National 

Archives, written commun. from Larry Dunsmoor, The 

Klamath Tribe, 2006). Moore reported:

Otter at present are practically extinct on the 

Reservation although some are occasionally reported 

from the lower Williamson River. Reports are that at 

one time this animal was common to all of the area.” 

and “The muskrat is a relatively recent addition to 

the Reservations fauna. Introduction was through 

the establishment of a muskrat farm on Crooked 

[C]reek, a few miles north of the Agency.

Regarding beaver, Moore reported:

Evidences are that at one time the Reservation was 

abundantly supplied with this animal. A thorough 

reconnaissance along the Sprague river from the 

Modoc Point diversion dam [Chiloquin Dam; 

FK 1.3] to the island, in Section 26 R. 8 E. Twp. 

34 S., a distance of about 9 miles [near FK 21.8], 

showed 32 old colony sites with their canals 

extending, in places, 100 yards from the river’s 

banks. At present but three beaver were along this 

area. One was a solitary migrant, while at Braymill, 

a pair had established themselves and seven 

slides existed.

In sum, these early observations indicate pre-Europeansettlement flood plains that typically were grass-covered in 

the wider valley segments but forested in the narrow valley 

segments. The South Fork valley segment was swampy, 

even in September, an observation consistent with the 

organic-rich soils evident in the stratigraphy at the section 

described at FK 98.5 (fig. 8). The Sprague River locally was 

multichanneled and composed of sand and gravel substrate 

thinly or patchily covering indurated silt and clay. Channels 

were at least locally flanked by willow and colonized by 

beaver and otter. The Sycan River within the Lower Sycan 

valley segment was sandy and mobile.

Ditches, Dams, Levees, Field Leveling, and Roads

Digging of diversion ditches and temporary dams along 

the Sprague River started as early as 1890, soon after first 

European settlement (Helfrich, 1974). By 1904, 37 km of 

ditches were irrigating parts of the South Fork, North Fork, 

and Upper Valley segments (Kent, 1905). By 1920, 37.6 km2

of valley bottom were irrigated in the Sprague River Basin, 

mainly by ditches within the wider flood-plain parts of the 

study area (La Rue, 1922). Additionally, the 1916 construction 

of Chiloquin Dam at FK 1.3 enabled water diversion from the 

Sprague River to the Modoc Irrigation District.

Extensive ditch and dike networks control flow within 

wider flood-plain segments, particularly in the South Fork 

valley segment (table 6; fig. 36). By 1968, the South Fork 

valley segment had more than 120 km of ditches and nearly 

60 km of levees partitioning, draining, and diverting flow 

along the 13.1 km length of flood plain. By 2000, total levee 

length exceeded 80 km. No other valley segment has the 

same density of flow manipulation structures, but all the 

unconfined reaches have substantial lengths of ditches and 

levees. The length of ditches and levees has increased in most 

valley segments for most time periods, but most construction 

was between 1940 and 1968, a result of a U.S. Army Corps 

of Engineers channelization program in the 1950s (Rabe 

and Calonje, 2009, p. 2–7). Since 1968, the length of levees 

generally has increased, whereas total ditch length has 

remained the same.

Associated with the locally extensive ditch network are 

many small dams and diversions. Most of these structures 

are in the South Fork valley segment, where 110 structures 

were evident in 1968 aerial photographs (table 6). The North 

Fork, Lower Sycan, Council Butte and Buttes of the Gods 

valley segments all had at least 10 diversion structures in 

2000. Several low dams were built across the Sprague River 

between 1916 and 1926 to facilitate water diversions and mill 

and log transport operations (USGS Oregon Water Science 

Center, Portland, Oregon, measurement station records for 

station 11501000). Remnants of these structures, chiefly 

pilings and dumped rock, are still visible at many former 

diversion locations along the river. With the 2008 removal of 

Chiloquin Dam, no structures currently span the main-stem 

Sprague River.

As with the length of dikes and levees, the total road 

length and developed area within the flood plain has increased 

in all segments between 1940 and 2000, with the exception of 

the Chiloquin Canyon and Beatty-Sycan segments (fig. 36). 

The increase in road length noted from aerial photograph 

mapping is in addition to earlier wagon and automobile roads, 

and railroads constructed in conjunction with first settlement 

and expanded timber harvest in the early 1900s. In particular, 

the raised bed of the railroad alignment locally limits 

flood‐plain inundation.

Although not systematically measured or mapped, 

another evident flood-plain modification is leveling or 

smoothing (fig. 37). Such smoothing and leveling, facilitated 

in recent years by global-positioning-system-controlled 

land leveling systems, aims to improve efficiency of flood 

irrigation—the most common irrigation practice in the 

Sprague River Basin (U.S. Department of Agriculture, 

2009). Leveled fields within the Sprague River geomorphic 

flood plain appear as areas of obscured channel and scrollbar topography, and typically are associated with dense and 

regular networks of irrigation ditches. Leveled areas are most 

common in the Upper Valley and South Fork valley segments, 

although it is likely that all unconfined segments have areas of 

field leveling.
48 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 36 Length of ditches, in kilometers

A

Length of levees, in kilometers

B

C

Length of roads, in kilometers

Built area (ditches, levees, roads, bridges,

dams, diversions, structures), in hectares

D

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

1940

1968

2000

Year

EXPLANATION

Incomplete aerial

photograph coverage

0

20

40

60

80

100

0

20

40

60

80

100

120

0

20

40

60

80

100

120

140

0

2

4

6

8

10

Figure 36. Extent of cultural features in the flood plain, including (A) irrigation and drainage ditches; 

(B) levees and dikes; (C) roads; and (D) total area covered by ditches, levees, roads, dams, diversions, and 

structures, as mapped from 1940, 1968, and 2000 aerial photographs, summed by valley segment, Sprague 

River Basin, Oregon.
Channel and Flood-Plain Conditions and Processes 49

tac14-0898_fig 37

FK 91.0

FK 92.0

FK 93.0

Sprague

River

South Fork

Sprague River

North Fork

Sprague River

Sprague

River

South Fork

Sprague River

North Fork

Sprague River

Not leveled

Leveled

0 0.1 0.2 0.3 0.4 MILES

0 0.1 0.2 0.3 0.4 KILOMETERS

121°8' 121°7'45" 121°7'30" 121°7'15" 121°7' 121°6'45" 121°6'30"

42°26'45"

42°26'30"

42°26'15"

Flood-plain kilometer transects

Geomorphic flood-plain boundary

EXPLANATION Base from National Agriculture Imagery Program aerial photography ,

0.5-meter resolution, and Watershed Sciences digital data, 1-meter

resolution. Universal Transverse Mercator Projection, Zone 10

North American Datum of 1983 (NAD 83)

Figure 37. Flood-plain topography smoothed by field leveling between flood-plain kilometers 91.0 and 93.0, Upper Valley 

segment, just downstream of confluence of South Fork and North Fork Sprague Rivers, Sprague River Basin, Oregon.

Channel Rehabilitation and Remeandering

Since the 1990s, several channel restoration and 

rehabilitation projects have involved channel and flood-plain 

manipulation. These projects aim to improve aquatic and 

flood plain habitat conditions, and include activities such as 

riparian fencing, bank stabilization (with vegetation plantings 

and placement of rock and large wood), levee breaching, 

and channel manipulation. These activities generally date 

from the early 1990s, and most have been coordinated with 

the U.S. Fish and Wildlife Service. The most physically 

manipulative of these activities have been the channel plugs 

and remeandering, whereby the channel course is altered or 

moved by filling and excavating. In many cases, the channel 

is placed back in locations occupied prior to recent avulsions. 

In some instances, the new channel course is protected by rock 

and anchored logs placed along banks (fig. 23). At least five 

such projects were completed within the study area between 

2004 and 2010, including sites in the Kamkaun Spring, 

Council Butte, Beatty-Sycan, North Fork, and Sycan valley 

segments (Sue Mattenberger, U.S. Fish and Wildlife Service, 

written commun., 2011).

Channel Planform—Spatial and 

Temporal Trends

Broadscale attributes of flood-plain and channel planform 

that are important geomorphically and ecologically include 

channel pattern, channel sinuosity, channel width, and the 

number and type of secondary channels. Important finer-scale 

attributes include bank morphology, bar area, bar frequency, 

and habitat measures such as pool frequency. The analyses 

in this study provide quantitative assessments of temporal 

changes for several of these channel and flood-plain attributes, 

drawing mainly from the historical maps and photographs.

Channel Pattern

Channel pattern characteristics such as sinuosity and 

frequency of secondary channels and backwater areas are 

important ecologically because they increase in-stream habitat 

complexity at all flow stages and provide refugia for fish and 

other aquatic organisms during high-flow stages (National 

Research Council 1992, 1996; Gregory and Bisson, 1997). 
50 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Planform channel pattern varies from straight in confined 

reaches to highly sinuous in some of the unconfined valley 

segments (fig. 17). For the Kamkaun Spring, Buttes of the 

Gods, Council Butte, Beatty-Sycan, Beatty Gap, North Fork, 

and Lower Sycan valley segments, sinuosity approaches or 

exceeds 1.4. For the Chiloquin Canyon, Braymill, S’Ocholis 

Canyon, Coyote Bucket, and South Fork valley segments, 

sinuosity is less than 1.2 (fig. 38). The South Fork valley 

is unconfined, but the low sinuosity here owes to channel 

straightening and confinement by levees (fig. 31B), which, 

in turn, has resulted in a channel slope more than twice that 

of the adjacent downstream Upper Valley segment. For all 

unconfined reaches, sinuosity has decreased between 1940 and 

2000 (fig. 38).

Within most of the study area, low flow is confined 

to a single channel. In total, secondary channels in which 

flow is conveyed during base-flow conditions occur along 

about 25 percent of the flood plain of the main-stem Sprague 

River and South Fork Sprague River (fig. 39). Few or no 

secondary channels convey flow in the Lower Sycan and 

North Fork valley segments. Most secondary channels are in 

the unconfined reaches, particularly the Kamkaun Spring and 

Council Butte valley segments, which have the lowest overall 

channel slopes.

The types of secondary channels present in the Sprague 

system include (1) short channels at the scale of a single 

meander, where a chute has developed across the meander 

core or neck but both chute and meander are still open and 

flowing; and (2) anabranches that are longer than a single 

meander (fig. 40). Such anabranches are distinct from channel 

braids in that they are separated from the main channel by 

vegetated and stable flood-plain surfaces rather than active 

bars. The degree of anabranching varies among segments in 

the Sprague River Basin, but they are particularly distinctive 

in the upper part of Council Butte valley segment and just 

downstream of the Sycan River confluence where they attain 

lengths of as much as 2.8 km and have been stable since 1940 

(fig. 40C). The stability of these anabranches is consistent with 

the overall absence of temporal trends in the area of secondary 

channels between 1940 and 2000 (fig. 38).

Backwater areas, defined as side channels connected to 

the primary channel but without through-flow at low flow 

(sometimes termed blind channels), occupy about one-half 

of the total area of secondary channels (fig. 39). Their 

spatial distribution follows that of secondary channels, with 

90 percent of the total backwater area in the unconfined 

Kamkaun Spring, Buttes of the Gods, and Council Butte 

valley segments. For these three valley segments, the total area 

of backwater has decreased by 32 percent between 1940 and 

2000, although backwater area has increased since 1968 in the 

Council Butte valley segment (fig. 38).

Channel Width

Channel width is an ecologically important attribute 

affecting in-channel hydraulic conditions, flow conveyance, 

and stream temperature (by affecting exposure to solar 

radiation). Channel width may change through time by many 

causes, including human disturbance, land-use, and changes in 

hydrologic regime (Wolman, 1967; Hammer, 1972; Kauffman 

and Krueger, 1984; Simon, 1989; Trimble and Mendel, 1995; 

Simon and Rinaldi, 2006). Therefore, changes in stream width 

are commonly evaluated in fluvial assessments. Assessments 

of the upper and lower Sprague River Basin conducted by 

the Klamath Basin Environmental Foundation proposed that 

there has been historical stream incision and widening in some 

streams within the Sprague River basin, but that the extent 

of this disturbance is unknown (Connelly and Lyons, 2007; 

Rabe and Calonje, 2009). Similar observations and inferences 

throughout the Upper Klamath Basin have led to the regional 

management goal to decrease channel widths (Boyd and 

others, 2002).

Within the Sprague River study area, historical changes 

in channel width were assessed in two ways: (1) comparison 

of measurements during the GLO cadastral surveys of the 

late 1800s with channel width as measured from the aerial 

photographs from 2000, and (2) measurement of changes since 

1940 on the basis of channel mapping in this study from the 

sequential aerial photographs.

Analysis of Channel Width from General Land 

Office Surveys

The original GLO surveys in the Sprague River Basin 

date from 1865 to 1892 (table 3), corresponding to first 

European settlement but predating significant disturbance of 

the valley bottom and channel system. These surveys aimed 

to facilitate land parceling and distribution; consequently, 

information regarding the channel was incidental to these 

goals. Nevertheless, the notes and maps recorded by the 

surveyors as they measured the township grids and surveyed 

bank lines provide information on channel conditions and 

geometry. In general, channel width was noted in two 

ways: (1) for all surveys of the township boundaries and 

its subdivisions (1-mi square sections), surveyors indicated 

locations along section lines where they crossed water and 

the width (in the direction of the surveyed line) of the water 

body; (2) for the 1871–72 meander surveys within parts of 

the Chiloquin Canyon, Council Buttes, and Beatty-Sycan 

valley segments, bank lines were surveyed to better document 

river location and available acreage for homesteading and 

cultivation. The bank lines of these meander surveys were 

marked by posts or stones at intersections with section lines.
Channel and Flood-Plain Conditions and Processes 51

tac14-0898_fig 38

0.0

0.0005

0.0010

0.0015

0.0020

0.5

1.0

1.5

2.0

2.5

0

200

400

600

800

1,000

1,200

1,400

0

100

200

300

400

0

50

100

150

200

0

50

100

150

200

250

Channel slope, in 

meters per meter

Channel sinuosity, 

in meters per meter

Primary channel area,

in hectares

Secondary channel 

area, in hectares Bar area, in hectares

Backwater area,

in hectares

1940

1968

Year

EXPLANATION

Incomplete aerial 

photograph coverage

2000

A

B

C

D

E

F

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

Figure 38. Summary plan-view channel and flood-plain characteristics, including (A) channel slope, 

(B) channel sinuosity, (C) primary channel area, (D) secondary channel area, (E) backwater area, and 

(F) bar area, as mapped from 1940, 1968, and 2000 aerial photographs, summed by valley segment, 

Sprague River Basin, Oregon.
52 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig39

Chiloquin

Canyon

Braymill Kamkaun

Spring

S’Ocholis 

Canyon

Council Butte Beatty

Gap

Upper 

Valley

LowerSycan

Coyote

Bucket

South

Fork

North

Fork

BeattySycan Buttes of the

Gods

Sprague River and South Fork Sprague River flood-plain kilometer North Fork Sprague

River flood-plain kilometer

Sycan River

flood-plain kilometer

Channel area, in square meters

per meter length of flood plain 

Secondary channel

area, in square

meters per meter

length of flood plain 

Backwater channel

area, in square

meters per meter

length of flood plain 

Bar area, in square

meters per meter

length of flood plain 

0 10 20 30 40 50 60 70 80 90 100 110 0 10 20 0 10

0

50

200150100

0

50

100

0

50

100

0

50

100

Figure 39. Spatial trends in channel and bar features, as mapped from aerial photographs taken in 2000, Sprague River Basin, Oregon. Measurements are 

summarized and normalized by 200-meter spacing of flood-plain transects.
Channel and Flood-Plain Conditions and Processes 53

tac14-0898_fig 40

0 0.2 0.4 KILOMETERS

0 0.2 0.4 MILES

FK 74.0

FK 76.0

FK 75.0

FK 77.0

Sprague River 

Sycan 

River

C

Anabranch

channels

0 100 200 METERS

0 300 600 FEET

FK 65.0

FK 64.0

Spr a gue River

B

Meander cutoffs

along levee

0 100 200 METERS

0 200 400 FEET

FK 26.0

FK 25.0

Sprague

River

Sprague

River

A

Neck cutoff

Flood-plain kilometer transects

Geomorphic flood-plain boundary

EXPLANATION

Direction of flow

Base map modified from national Agriculture 

Imagery Program aerial photography, 

0.5-meter resolution. Projection: UTM, Zone 

10N, Horizontal datum: North American 

Datum of 1983 (NAD 83)

Figure 40. Examples of meander cutoffs, avulsions, and 

anabranches, including (A) neck cutoff and avulsion between 

flood-plain kilometers (FKs) 25.0 and 26.0, Kamkaun Spring valley 

segment (the neck cutoff at FK 25.3 was filled in 2005–06, as 

shown in figure 23); (B) meander cutoffs formed along levees 

between FKs 64.0 and 65.0; and (C) anabranches spanning many 

meander loops between FKs 74.0 and 77.0, Sprague River Basin, 

Oregon.

In analyzing the river-width observations from the 

GLO surveys, an important uncertainty is the nature of the 

measured width—was it actual water width at the time of 

survey, or bank-to-bank width (similar to bankfull or active 

channel width)? In many situations, meander surveys can 

provide continuous channel-width information (for example, 

O’Connor and others, 2003c), but for the Sprague River, 

meander surveys were done for a limited section of the river, 

and only one bank was surveyed, so no actual measurements 

of river width can be obtained for these meander surveys 

except for where they were monumented at section-line 

intersections. The observations along section lines are more 

difficult to extract, requiring access to the surveyor notes, 

but may provide better information on actual channel width 

(Knox, 1977). The 1855 manual to GLO surveyors instructed 

surveyors to measure the widths of water features on the 

section lines, including “all creeks, rivers and smaller streams 

of water which the line crosses,” with no mention of banks 

(White, 1983, p. 17), although practices varied from surveyor 

to surveyor and across time (Collins and others, 2003).

To clarify the distinction between the widths indicated 

by the meander surveys and those from the surveys along 

the section lines, we assessed the GLO surveys for three 

townships within the Council Butte segment, T36S R10E, 

T36S R11E, and T36S R12E. The section lines for these 

townships were surveyed in 1866, at which time river width 

was measured along each section line as the surveyor crossed 

it. In July and August 1872, another surveyor returned to 

these townships to survey subdivisions of some sections (into 

20-acre lots) and to conduct a meander survey. Although 

only the south bank line was surveyed during this meander 

survey, surveyed monuments of both banks were placed 

at the intersections of the section lines, allowing direct 

comparison with the channel width as noted in the 1866 

survey. This comparison shows that for 13 of the 17 section 

lines intersected by the meander survey, channel width noted 

in the 1866 section-line survey was less than the 1872 width 

from the meander survey, ranging from 22 to 94 percent 

(median value 67 percent) of the 1872 width (table 7). Of 

the four 1872 measurements showing a narrower channel 

width, two appear erroneous because the noted measurements 

do not close properly along the length of the section line 

(resulting in a negative calculated 1872 channel width). The 

other two measurements indicating a channel narrower by 

10–15 m in 1872 also may represent survey error or possibly 

channel change in the 6 years between surveys. In sum, this 

comparison indicates narrower measurements associated with 

the section line crossings of 1866 relative to the meander 

surveys of 1872, consistent with the inference that the 

meander surveys are of bank edges whereas the section line 

surveys denote actual water edges, as has been assumed in 

previous studies (Williams, 1971; Wallick and others, 2006).
54 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Table 7. Channel width measurements from General Land Office section-line and meander surveys, Sprague River Basin, Oregon.

[Chains, units for the General Land Office measurements were Gunter’s chain, where 1 chain equals 20.1168 meters. Abbreviations: m, meter; T, Township; S, 

South; R, Range; E, East]

Township 

and range

Sections

separated by 

surveyed line

1872 distance 

between 

meander posts

(chains)

1866 sectionline river width 

(chains)

Difference 

between 1872 

and 1866 width 

measurements 

(chains)

Difference

between 1872 

and 1866 width 

measurements

(m)

Channel 

morphology 

T36S R10E 10, 11 2.25 2.00 0.25 5.03 Straight section

T36S R10E 11, 12 2.50 3.00 -0.50 -10.06 Straight section

T36S R10, 11E 7, 12 1.50 1.00 0.50 10.06 Bend

T36S R11E 7, 8 0.50 1.25 -0.75 -15.09 Straight section

T36S R11E 8, 9 -1.00 1.00 -2.00 -40.23 Slight bend

T36S R11E 9, 10 -1.50 3.00 -4.50 -90.53 Bend

T36S R11E 10, 11 3.75 2.50 1.25 25.15 Bend

T36S R11E 11, 12 1.50 1.25 0.25 5.03 Bend

T36S R11, 12E 7, 12 1.80 1.50 0.30 6.04 Bend

T36S R12E 7, 8 1.75 1.40 0.35 7.04 Slight bend

T36S R12E 17, 8 7.60 2.00 5.60 112.65 Straight section

T36S R12E 17, 16 3.50 2.00 1.50 30.18 Bend

T36S R12E 16, 15 3.50 2.50 1.00 20.12 Bend

T36S R12E 15, 10 3.75 1.50 2.25 45.26 Bend

T36S R12E 10, 11 4.50 1.00 3.50 70.41 Straight section

T36S R12E 11, 14 2.80 0.90 1.90 38.22 Bend

T36S R12E 13, 14 4.50 4.25 0.25 5.03 Bend

Assuming that the section line surveys report 

measurements of actual wetted width, we assessed 143 section 

line crossings in the study area from the surveyors’ notes, 

available from the Bureau of Land Management (2011). 

Because the section lines may cross the channel at various 

angles, the measured width was adjusted from available 

information on the channel orientation. For section lines 

where the river the survey notes indicate the channel crossing 

the section line perpendicularly, the GLO river width was 

not adjusted. However, for locations where the intersection 

between the channel and section line was not perpendicular, 

measurements of channel width along the section line were 

converted to width perpendicular to flow at the time of 

survey by multiplying the observed width by the sine of the 

angle between the direction of river flow and the surveyed 

section line. For most section lines, surveyors noted river 

flow direction only to the nearest cardinal or intercardinal 

direction, but for some sections it was recorded to the nearest 

degree. Additionally, for 16 section lines in the Council Butte 

and Beatty-Sycan valley segments, river flow directions were 

obtained from the plat maps showing 1872 meander surveys, 

assuming little change since the 1866 section-line survey.

Sixty of the 143 crossings were not fully analyzed 

because (1) they were highly oblique (greater than 60 degrees) 

to the channel direction, (2) they were at locations where 

comparison to modern channel widths would be challenging, 

such as at the apex of a meander bend or at a tributary 

confluence, or (3) no channel direction information was 

provided. Another 21 crossings were excluded because the 

GLO survey records of channel width and orientation were 

inconsistent with topography, indicating errors in the GLO 

survey notes.

Excluding the less reliable measurements, 62 late19th-century, channel-width measurements remained at 

known locations (appendix F). The spatial distribution of these 

measurements is uneven, ranging from only one observation 

along the combined length of the Chiloquin Canyon 

and Braymill valley segments, to 14 observations in the 

Council Butte valley segment. The resulting channel widths 

(perpendicular to flow) ranged from 6 to 58 m, with many of 

the widest sections in the Kamkaun Spring and Council Butte 

valley segments. The narrowest channel widths were in the 

South Fork, North Fork, and Coyote Bucket valley segments. 

These GLO width measurements can be compared to the 

channel width measurements from the 2000 aerial photographs 

at the same locations. At the six sites where the 2000 aerial 

photographs showed bars flanking the channel at the section 

line crossing, the width of the bar was included in the channel 

width. All measurements from the 2000 aerial photographs 

were perpendicular to flow direction. Similar to the GLO 

measurements, measured channel width in 2000 ranged from 

7 to 51 m.
Channel and Flood-Plain Conditions and Processes 55

Although the discharge at the time of the GLO surveys 

is unknown, the water widths in the GLO surveys and 2000 

photographs likely are comparable because all widths were 

measured at relatively low flow. The 2000 aerial imagery was 

taken between late July and mid-August (table 4). The GLO 

surveys were between July and November, the five lowest 

flow months of the year based on long-term average discharge 

at Chiloquin (fig. 3).

Whereas different discharges associated with the surveys 

and measurements may introduce a small but unknown bias, 

more significant are transcription and survey errors that affect 

some of the observations, as apparent from the clear miscues 

noted in comparing the 1872 meander survey and 1866 GLO 

section-line surveys. An even more likely pervasive error 

results from adjusting the GLO measured channel widths to 

channel width perpendicular to flow direction. For locations 

where the angle of intersection was within 25 degrees of 

perpendicular, likely errors in the adjusted width are small—

less than 10 percent. However, a plus-or-minus 25-degree 

uncertainty about a 45 degree intersection angle results in a 

plus-or-minus 30-percent uncertainty in the resulting adjusted 

width. For lower incidence angles, the resulting uncertainty is 

even greater.

The resulting 62 comparisons between channel width 

surveyed by the GLO between 1865 and 1892 (most were 

surveyed between 1865 and 1869) and those measured at 

the same location from 2000 aerial photographs show a 

wide range of change (appendix F; fig. 41). Although there 

are substantial discrepancies at some sites—in places the 

channel in 2000 is as much as four times as wide as it was 

at the GLO survey and in others it is less than one-half of its 

previous width—some overall trends are evident. In general, 

channels that were wide during the GLO surveys became 

narrower, and channels that were narrow became wider. The 

trend of the measurements crosses the 1-to-1 line between 

channel widths of 20 and 30 m (fig. 41A), indicating that this 

width range generally separates the channels that widened 

from those that narrowed. Overall, the median value of the 

ratio between the 2000 width and the GLO width is 0.96, 

indicating slight overall narrowing of the measurement sites, 

but the difference is small relative to the variance and the 

measurement uncertainty.

Stratifying the observations by valley segments reveals 

trends within specific reaches (fig. 41B). The Kamkaun Spring 

and North Fork valley segments apparently have narrowed 

between the GLO surveys and year 2000, as possibly has the 

Beatty Gap valley segment with three of its four measurements 

showing narrowing. By contrast, four of the five comparisons 

in the South Fork valley segment indicate widening. Overall 

widening trends also are possible in the Council Butte, 

Beatty-Sycan and Coyote Bucket valley segments, although 

data are either few or the differences are small.

tac14-0898_fig 41 Ratio of width on 2000 aerial photographs to GLO width 

1

2

4

6

0.2

0.4

0.6

Narrowed Widened

B

Valley segment

Width of active channel on 2000 aerial photographs, in meters

Width of channel from GLO survey notes, in meters

0 10 20 30 40 50 60

0

10

20

30

40

50

60

Narrowed

1:1

Widened

Regression and 95-percent

confidence limits

A

Braymill

Kamkaun Spring

S’Ocholis Canyon

Buttes of the Gods

Council Butte

Beatty-Sycan

Beatty Gap

Upper Valley

South Fork

North Fork

Lower Sycan

Coyote Bucket

All reaches

EXPLANATION

Valley segment

50th percentile

75th percentile

95th percentile

25th percentile

5th percentile

Figure 41. General Land Office (GLO) surveyed (chiefly in 1866) 

widths compared with measured widths from aerial photographs 

taken in 2000 for (A) 62 GLO surveyed widths and at the same 

location as determined from aerial photographs (table 7); and 

(B) relation between GLO and widths in 2000 by valley segment, 

Sprague River Basin, Oregon.
56 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Analysis of Channel Width from Aerial Photographs

Observations of channel width derived from historical 

aerial photographs are more systematic but cover a shorter 

period than those derived from GLO surveys. For this 

analysis, channel widths for each of the 1940, 1968, 

and 2000 photographic sets were measured on transects 

spaced 200 m apart along the channel centerline. For these 

measurements, the wetted width orthogonal to the channel 

centerline was considered the channel width. Because the 

channel centerline shifted between years, transect locations are 

not identical for each period. However, the large number of 

observations—for example, 932 width measurements within 

the study area from the 1968 aerial photographs—permits 

observation of general trends in channel width both spatially 

and temporally (figs. 42, 43).

Overall, the median primary channel width for 

682 measurements along the main-stem Sprague River in 

2000 was 30.3 m. For the North Fork Sprague River, the 

median channel width (for 79 measurements) was 10.0 m; 

for the South Fork Sprague River (74 measurements), the 

median channel width was 9.3 m; and for the Sycan River 

along both the Lower Sycan and Coyote Bucket segments 

(152 measurements), the median channel width was 14.1 m. 

For all time periods, the channel generally is widest in the 

unconfined segments, particularly the Buttes of the Gods, 

Council Butte (where width locally exceeds 100 m), and 

Beatty-Sycan segments. The channel also is wide in parts 

of the Kamkaun Spring segment as well as in the lower part 

of the Chiloquin Canyon segment near the Sprague River 

confluence with the Williamson River and where the channel 

was impounded by Chiloquin Dam at FK 1.3.

The channel generally was widest in the 1968 aerial 

photographs, when the median width of the main-stem 

Sprague River was 32.4 m compared to 29.9 m in 1940 and 

30.3 in 2000. This was the case for most individual valley 

segments as well (fig. 43); of the valley segments with 

complete aerial photograph coverage for all three years, only 

the Braymill and Council Butte valley segments had wider 

channels in either 1940 or 2000. For six segments (Kamkaun 

Spring, S’Ocholis Canyon, Buttes of the Gods, Beatty-Sycan, 

Beatty Gap, and Upper Valley), widening was substantial—as 

much as 60 percent of the 1940 width in the case of Upper 

Valley. Between 1968 and 2000, most segments narrowed to 

widths similar to those measured from the 1940 photographs. 

For some valley segments, such as Lower Sycan and BeattySycan, narrowing decreased median channel width by as much 

as 20 percent. The Council Butte valley segment is unique 

in having an apparent systematic decreasing trend in median 

width between 1940 and 2000 (fig. 43). The South Fork valley 

segment shows a similar trend, but the 1940 aerial photograph 

coverage is incomplete for this segment. The variance in 

channel width has decreased since 1940 for several valley 

segments, particularly upstream of S’Ocholis Canyon (fig. 43).

Bars

Bars are significant fluvial features because they are 

indicative of bedload transport and contribute to physical 

habitat complexity. Active sand and gravel bars are relatively 

sparse for much of the Sprague River and its major tributaries 

(fig. 39). Total bar area in the study area at the time of the 

2000 aerial photographs was about 330,000 m2 (33.0 hectares 

[ha]), less than 10 percent of the corresponding primary 

channel area. Bars are distributed more broadly than 

secondary and backwater channels, with a few bars flanking 

the channel in all valley segments (fig. 18). Bars generally 

are more common and larger in the unconfined reaches than 

in confined reaches, although the confined Beatty Gap and 

S’Ocholis Canyon valley segments have abundant bars. Bars 

are sparse in the narrowly confined Chiloquin Canyon and 

Braymill valley segments.

Bars are locally abundant where the North Fork Sprague 

River and Sycan River leave steeper and more confined 

segments. For the North Fork Sprague River, this corresponds 

to the upper end of the study reach where the North Fork 

emerges from Fremont National Forest. For the Sycan River, 

bars are most abundant where the river leaves the steep 

and confined Coyote Bucket valley segment (figs. 18, 39). 

Similarly, many of the few small bars in the South Fork valley 

segment are at the upstream end of the study area, where 

the river emerges from the foothills east of Bly. Bars also 

are concentrated near the Sycan River confluence with the 

Sprague River within the Council Butte and Beatty-Sycan 

valley segments.

In nearly all valley segments, bar area was greater in 

2000 than it was in 1940, with the total area (excluding the 

North Fork and South Fork valley segments for which the 

1940 photographs are incomplete) increasing from 18 to 

29 ha (fig. 38). It is not clear, however, that this is a longterm trend because the area of bars was much larger in 

1968 (when bar area totaled 67 ha) than in 2000. This large 

1968 total almost certainly owes to enhanced sediment 

transport and bar formation and expansion during the 422 m3/s 

flow of December 26, 1964, the largest flood since at least 

1920 (fig. 2).

Channel Migration

Closely related to processes affecting channel planform 

are those that control the rates and styles of lateral channel 

migration. For the Sprague River study area, the stratigraphic 

analyses and the analyses of sequential photographs together 

document the relative importance of processes such as lateral 

migration, meander cutoffs, and avulsions in controlling the 

overall channel pattern and rates of evolution.
Channel and Flood-Plain Conditions and Processes 57tac14-0898_fig42 Sycan River river kilometer Lower Sycan Coyote Bucket 0 20 30 10 Sprague River and South Fork Sprague River river kilometer North Fork Sprague River river kilometer

Primary channel width, in meters

Chiloquin

Canyon

Braymill Kamkaun

Spring

S’Ocholis 

Canyon

Council Butte Beatty

Gap

Upper 

Valley

South

Fork

BeattySycan Buttes of the Gods North Fork

0 2010

0

80604020

100

0

80604020

100

0

80604020

100

0 20 40 60 80 100 120 140 160

Minimum

values

Valley segment boundary

EXPLANATION

194019682000

Figure 42. Spatial trends in channel width, as mapped from aerial photographs taken in 1940, 1968, and 2000, Sprague River Basin, Oregon. Measurements were 

made at transects perpendicular to channel centerline 200 meters apart. The position and length of the channel centerlines vary for each time period, so width measurements are not precisely comparable at specific locations.
58 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 43

* * *

Coyote 

Bucket

Channel width, in meters

0

10

20

30

40

50

60

70

80

90

100

110

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

50th percentile

75th percentile

95th percentile

25th percentile

5th percentile

Outliers

Outliers

1940

1968

2000

EXPLANATION

Year

Incomplete aerial

 photograph

 coverage

Figure 43. Wetted channel width measurements summarized by valley segment, Sprague River Basin, Oregon. 

Because of aerial photograph coverage limits, the 1940 measurements include only small parts of the South Fork, 

North Fork, and Coyote Bucket valley segments; no 1968 measurements are available for the Coyote Bucket valley 

segment. Channel widths are shown in figure 42.

Observations from Stratigraphy and Morphology

The stratigraphic exposures, augering transects, 

and surficial morphology indicate lateral bar growth and 

channel migration, followed in many instances by channel 

abandonment, presumably by meander cutoff or avulsion. 

Lateral flood-plain building is evident from the dipping 

beds visible in stratigraphic exposures along the North Fork 

Sprague River (figs. 9, 11) and Sycan River (fig. 14). The 

scroll-bar morphology locally evident on low and young 

flood‐plain surfaces (fig. 13) indicates lateral channel 

migration in conjunction with sandy point bar development, 

an observation consistent with point bar deposition during the 

2006 high flows (fig. 15).

Many of the meander bends, however, appear to have 

been abandoned rapidly, leaving distinct and isolated oxbows 

or swales. The stratigraphy of deposits filling these former 

channels shows abrupt transitions, with basal bedrock strath 

surfaces, gravel, and sand associated with active channel 

environments overlain by peat, silt, and clay (figs. 12, 13). 

At some sites, such as 9/22/05-4 at FK 48.7 (fig. 12), where 

the paleochannel is substantially filled with sand and gravel, 

meander cutoff or channel avulsion may have been promoted 

by point-bar growth blocking sharp bends. Prehistoric 

avulsions, particularly in the more densely timbered confined 

reaches, may have been triggered by log jams.

Channel migration only slowly works its way across 

the flood plain, as also is evident from the stratigraphic 

analyses. Some of the preserved paleochannels are nearly 

4,000 years old (fig. 12), and many flood-plain sections have 

been accumulating overbank deposits for several hundreds of 

years and, in places, thousands of years subsequent to the last 

channel occupancy (figs. 5, 8, 9).
Channel and Flood-Plain Conditions and Processes 59

Centerline Analysis

Rates of channel migration can be derived from 

the historical maps and photographs, although rates and 

mechanisms observed since the first maps of the 1860s and the 

photographs beginning with 1940 likely have been affected 

by land use and channel manipulation. Channel migration was 

measured in the manner of O’Connor and others (2003c), in 

which the channel centerline position for each time period was 

evaluated in reference to flood-plain transects spaced 200 m 

apart along the flood-plain centerline. The change in position 

of the intercept between successive channel centerlines and the 

flood-plain transects indicates the net lateral movement with 

respect to the flood-plain reference system. This net movement 

divided by the time period between mapped positions gives 

an average annual migration rate. Centerlines were mapped 

for the meandered sections of the GLO maps in the Council 

Butte and Beatty-Sycan valley segments, as well as from 

the 1940, 1968, 1975, 2000, and 2005 aerial photograph 

and map sources (table 4). Parts of the South Fork, North 

Fork, Lower Sycan, and Coyote Bucket valley segments are 

incompletely covered by the 1940 or 1975 photographs and 

maps; consequently, migration rates encompassing those time 

periods and segments are incomplete.

Calculated migration rates for various periods between 

about 1870 and 2005 mostly are less than 0.5 m/yr but are as 

much as 30 m/yr (figs. 44, 45). Migration rates vary spatially 

and temporally, with the overall greatest migration rates in the 

unconfined valley segments, particularly the Kamkaun Spring, 

Buttes of the Gods, and Council Butte valley segments. The 

unconfined South Fork valley segment is an exception, with 

low migration rates (particularly since 1975) similar to those 

measured for the Chiloquin, Braymill, and S’Ocholis Canyon 

valley segments.

Migration rates are spatially and temporally correlated; 

reaches of high and low mobility tend to extend for several 

kilometers and to persist for many measurement periods 

(fig. 44). Additionally, some reaches for some periods 

have exceptional migration rates exceeding 5 m/yr. These 

very high rates owe to the channel moving large distances 

laterally by translocation across the flood plain rather than 

by continuous migration from lateral bank erosion and 

point bar development. In most cases where migration rates 

exceeded 1 m/yr, avulsion or meander cutoff was responsible. 

The median migration rates, ranging from about 0.06 to 

0.3 m/yr for most segments (fig. 45), probably represent rates 

of continuous lateral shifting by bank erosion.

For most valley segments, the 1968–1975 period had the 

highest migration rates (fig. 45). However, this period appears 

unique within an overall declining trend of historical migration 

rates, with the 2000–2005 period having the lowest median 

migration rate for 10 of the 13 analyzed valley segments. This 

declining trend is evident particularly for the Council Butte 

and Beatty-Sycan valley segments, for which migration rates 

were calculated dating back to the 1870s GLO meander maps.

Channel migration rates on the Sprague River are 

slow in relation to many other alluvial rivers of western 

North America. Mean migration rates range between 0.16 

and 0.59 m/yr for all analyzed time periods on the mainstem Sprague River. By contrast, the gravel-bed rivers of 

the Olympic Peninsula have migration rates ranging from 

2.1±1.7 m/yr for the lower Elwha River (Draut and others, 

2011) to 8.8±4.1 m/yr for the Quinault River (O’Connor and 

others, 2003c). Nanson and Hickin (1986) reported average 

migration rates of 0.57–8.3 m/yr for 18 river reaches in 

western Canada, and Giardino and Lee (2011) document an 

average migration rate of 3.28 m/yr for the Brazos River, 

Texas, for an analysis period extending back to 1929.

Expressed in terms of channel width, most segments 

had median migration rates of less than 0.01 channel widths 

per year (fig. 46). Such rates place the Sprague River within 

Hooke’s (2003) class of stable meanders. These rates are 

also in the low end of the range of migration rates (0.0003 to 

0.23 channel widths per year ) for other low-gradient rivers 

like the Sprague River (Dietrich and others, 1999; Gilvear 

and others, 2000; Brooks, 2003; Micheli and others, 2004; 

Rodnight and others, 2005; Gautier and others, 2007).

Channel Cutoffs and Avulsions

The locally high channel migration rates evident for 

short reaches within the unconfined valley segments (fig. 44) 

resulted from meander cutoffs and channel avulsions. Such 

events result in rapid translocation of the primary channel, 

leaving secondary or backwater channels in their wake 

(fig. 40). Mapping changes in channel position from the 

historical aerial photographs and GLO maps (where the 

channel was meandered in 1872 within the Council Butte and 

Beatty-Sycan valley segments) show cutoffs and avulsions 

widely distributed throughout the Sprague and Sycan River 

system, but more common in the wider and unconfined valley 

segments (fig. 47). When normalized by length of channel 

available for comparison and time period, the periods between 

1940 and 1975 had the greatest frequency of avulsions, with 

rates more than twice those of any other time period (table 8). 

This finding is consistent with the locally very high lateral 

migration rates determined for those time periods from the 

flood-plain transect analysis of lateral migration (fig. 44) and 

probably represent effects of the 1964 flood or possibly human 

modifications of the channel and flood plain.
60 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 44

0 10 20 30 40 50 60 70 80 90 100 110 0 10 0 10 20

0

10

20

30

40

1

2

3

4

5

5

0

10

20

30

40

1

2

3

4

5

5

0

10

20

30

40

1

2

3

4

5

5

0

10

20

30

40

1

2

3

4

5

5

0

10

20

30

40

1

2

3

4

5

5

North

Fork

Lower

Sycan

Coyote

Bucket

Chiloquin

Canyon

Braymill Kamkaun

Spring

S’Ocholis 

Canyon

Council Butte Beatty

Gap

Upper 

Valley

Beatty- South Fork

Sycan

Buttes of 

the Gods

Sprague River and South Fork Sprague River flood-plain kilometer

Channel migration rate, in meters per year

North Fork

Sprague River

flood-plain

kilometer

Sycan River

flood-plain kilometer

About 1870 to 1940

1940 to 1968

1968 to 1975

1975 to 2000

2000 to 2005

Incomplete aerial photograph

 coverage

EXPLANATION

Valley segment

 boundary

Figure 44. Spatial trends in lateral channel migration rate determined from channel centerline positions, as mapped from General Land 

Office (GLO) maps and aerial photographs from 1940, 1968, 1975, 2000, and 2005, Sprague River Basin, Oregon. Channel movement was 

determined from sequential centerline intercepts with flood-plain transects spaced 200 meters apart. GLO to 1940 migration rates were 

determined only for parts of Council Butte and Beatty-Sycan valley segments where the channel was meandered. Observations from 

South Fork, North Fork, Lower Sycan, and Coyote Bucket valley segments were limited for some time periods by incomplete map and 

photographic coverage.
Channel and Flood-Plain Conditions and Processes 61

tac14-0898_fig 45 Channel migration rate, in meters per year

0.001

0.01

0.1

1

10

100

Coyote 

Bucket

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

50th percentile

75th percentile

95th percentile

25th percentile

5th percentile

Outliers

Outliers

About 1870-1940

1940-1968

1968-1975

1975-2000

2000-2005

EXPLANATION

Time period

Incomplete aerial

 photograph

 coverage

Figure 45. Channel migration rate measurements summarized by valley segment, Sprague River Basin, Oregon. 

Migration rates are in figure 44.

Table 8. Avulsion and cutoff frequency, Sprague River Basin, Oregon.

[Abbreviations: km/yr, kilometer per year; ~, approximately]

Period Total 

number

Neck 

cutoffs

Chute 

cutoffs

Indeterminate Avulsions

Frequency 

(number/

km/yr)

1~1870–1940 3 0 3 0 0 0.001 11940–1968 35 7 18 2 8 0.007

1968–1975 16 1 12 1 2 0.014

1975–2000 9 1 7 0 1 0.002

2000–2005 3 0 2 0 1 0.003

1

Incomplete aerial photograph coverage.
62 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 46

Valley segment bar area/valley segment primary channel area, 

in square meter per square meter

0 0.1 0.2 0.3 0.4 0.5 0

0.005

0.010

0.015

South Fork Sprague River measurement

(ignored for regression)

y = 0.0033 + 0.016x

r

2

 = 0.26

A

0 0.0005 0.0010 0.0015 0.0020

0

0.005

0.010

0.015

y = 0.0031 + 7.6x

r

2

 = 0.40

Chiloquin Canyon measurements

(ignored for regression)

South Fork Sprague River

measurement (ignored for 

regression)

B

Channel slope, in meters per meter

Valley segment median migration rate/valley segment median channel width, in meters per year per meter

1968 bar area; 1940-1968 migration rate

2000 bar area; 1968-2000 migration rate

EXPLANATION

r2, coefficient of determination

Figure 46. Migration rate correlations and confidence intervals 

along valley segment summarized variables, Sprague River Basin, 

Oregon. (A) Normalized bar area and migration rate (normalized 

by median channel width) and (B) channel slope and normalized 

migration rate.

Channel Incision

Although long-term channel incision or downcutting 

is the inevitable consequence of drainage systems eroding 

landscapes, short-term episodes of channel incision into 

flood plains can lead to many morphologic, ecologic, and 

water‐quality consequences to the fluvial system (Williams 

and Wolman, 1984; Schumm, 1999; Simon and Rinaldi, 2006; 

Shields and others, 2010; Cluer and Thorne, 2013). Such 

short-term incision can be triggered by land-use changes, 

changes in hydrologic regime, and channelization, among 

other causes. Once incision begins in alluvial channel systems, 

it typically propagates upstream and leads to an enduring 

sequence of channel evolution involving downcutting and 

widening before establishment of a new flood-plain inset 

within the original flood-plain surface (Simon and Hupp, 

1986; Cluer and Thorne, 2013). In certain environments, 

recovery to pre-incision states requires decades or centuries 

(Beechie and others, 2008), while in others a compound cross 

section composed of a narrow flood plain laterally constrained 

by paired terraces may persist for similar lengths of time. 

Therefore, preventing or reversing channel incision is a 

common goal of watershed and channel restoration (Palmer 

and others, 2005; MacWilliams and others, 2010). Incision 

has been a concern in the Sprague River Basin (Connelly and 

Lyons, 2007; Rabe and Calonje, 2009).

Stratigraphic Analysis

The stratigraphic records and augering transects provide 

a century-to-millennial scale perspective on historical channel 

incision. Along the main-stem Sprague River and lower Sycan 

River, the stratigraphic sections recording older stratigraphy 

locally show pre-Mazama fluvial gravel as much as 2 m 

higher than the present channel bed (fig. 4), indicating channel 

and flood-plain formation higher than present levels prior to 

7,700 cal yr BP. Subsequent incision may represent overall 

valley excavation, but more likely the higher channels and 

flood plains (now terraces) of the late Pleistocene and early 

Holocene represent higher sediment loads and flow regimes, 

similar to conditions in the Willamette Valley (O’Connor 

and others, 2001) and the Oregon Coast Range (Personius 

and others, 1993) where greater sediment (owing to more 

intense physical weathering) and water fluxes during colder 

Pleistocene climates resulted in regional aggradation.
Channel and Flood-Plain Conditions and Processes 63

tac14-0898_fig 47

Base map modified from Watershed Sciences digital data, 1-meter resolution, and U.S. Geological Survey 

digital data, 10-meter resolution Projection: UTM, Zone 10N, Datum: North American Datum of 1983 (NAD 83)

N

121°50' 121°40' 121°30' 121°20' 121°10' 121°

42°

30'

42°

20'

Sprague River

Sycan River

North Fork Sprague River

South Fork Sprague River

0 5 10 KILOMETERS

0 5 10 MILES

EXPLANATION

GLO to 1940

Time period

1940 to 1968

1968 to 1975

1975 to 2000

2000 to 2004

Channel centerline, 2000

GLO, General Land Office 

survey

Figure 47. Locations and timing of avulsions and cutoffs evident from map and aerial photograph analysis, Sprague River Basin, 

Oregon.

However, subsequent to the Mazama eruption of about 

7,700 years ago, the stratigraphic exposures and augering 

indicate little or no overall channel incision for most of 

the Sprague River study area. The base of paleochannels 

(abandoned as much as 3,800 cal yr BP) probed during the 

augering transects near FK 31 and 48 are as much as 1 m 

lower than the present channel to 0.2 m higher, indicating 

little net incision and perhaps even aggradation of the valley 

bottom in the Kamkaun Spring and Buttes of the Gods 

valley segments during the late Holocene (figs. 12, 13). 

Similarly, the bank exposures of post-Mazama flood-plain 

stratigraphy along the main-stem Sprague River, North 

Fork Sprague River, and Sycan River show channel gravels 

nowhere more than 40 cm above the present base-flow water 

surface (figs. 5, 8, 9). Modern (2006) coarse sand and gravel 

deposition to similar or higher levels on point bars during 

high flows also indicate that the present channel is not incised 

(fig. 14). Similar to the auger probes, several sections show 

channel deposits of the last 1,000–2,000 years as much as 

50 cm below the present channel bottom, also indicating late 

Holocene channel aggradation.

Stratigraphic exposures along the North Fork Sprague 

River and the Sycan River indicate episodes of flood-plain 

erosion and construction possibly resulting from different 

hydrologic and sediment regimes. Along the North Fork 

Sprague River, an actively aggrading flood plain less than 

300 cal yr BP is inset into an older flood plain as much as 

4,700 cal yr BP (figs. 9, 11). The older flood-plain deposits 

along the North Fork Sprague River are distinctive because 

of a 0.5-m-thick peat and diatomaceous horizon, indicating 

a significant period of wet flood-plain conditions with little 

sediment transport sometime after 4,330 cal yr BP (fig. 9).

Similarly, the Sycan River is flanked by low floodplain surfaces that began accumulating overbank deposits 

as recently as 600 cal yr BP (fig. 5). In some locations, this 

younger flood plain is inset against taller and older flood-plain 

deposits that began accumulating soon after the approximately 

7,700 cal yr BP Sycan flood (Lind, 2009). For the Sycan 

River and North Fork Sprague River, however, there is no 

evidence of substantial and persistent changes in channel 

altitude associated with these multiple episodes of flood-plain 

formation and erosion.

Channel incision is evident, however, in the stratigraphy 

exposed at the single investigated site along the South Fork 

Sprague River (fig. 8). Here, the base of post-Mazama channel 

and bar deposits is about 50 cm above the present thalweg. 

The top of a 60-cm thick diatomaceous peat layer, probably 

actively accumulating deposits at the time of the first GLO 

surveys (judging from surveyor descriptions of a swampy 

flood plain during their September 1866 traverse), was more 

than 1.6 m above the water surface at the time of description 

in 2007.
64 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Channel Centerline Altitude Changes

Trends in channel incision are more challenging to 

document quantitatively from historical sources such as aerial 

photographs than are planform changes. In some instances, 

repeat longitudinal topographic and cross section surveys 

can indicate spatial and temporal trends in channel incision 

(for example, Wallick and others, 2010, 2011). However, for 

the Sprague River study area, no such surveys are known. 

Therefore, to evaluate possible channel altitude changes 

across time, we have used the channel centerline mapping in 

conjunction with the lidar topography to estimate changes in 

channel altitude across time within the study area (fig. 48).

This analysis entailed determining altitudes from the 

2004 lidar at intercepts between the flood-plain transects, 

spaced 200 m apart, for the length of the study area, and 

channel centerlines, as mapped from each of the historical 

map and aerial photograph sources (figs. 48, 49). No analysis 

is possible at the many such intercepts where lidar altitudes 

are missing because of specular reflection during the 2004 

acquisition, mainly in the Kamkaun Spring valley segment. 

Furthermore, for locations where the channel has not moved 

during the analysis period, the location of the intercept 

remains the same, thus, the altitude obtained from the 2004 

lidar also remains constant, and trends cannot be determined. 

However, for locations where the channel had shifted and 

lidar altitude is available, the difference in altitude can be 

determined between the channel intercept of the first location 

and that of subsequent channel positions. This difference owes 

to the combined consequences of (1) actual channel altitude 

changes, (2) differential rates of overbank aggradation and 

paleochannel filling within abandoned channel traces, and 

(3) errors in the lidar altitude data. Resolution of these errors is 

possible only where thalweg gravel altitudes can be surveyed 

precisely for many channel centerlines at a single transect, as 

has been done with the augering transects for the prehistoric 

paleochannels (figs. 12, 13).

Because such surveys of channel deposits have not 

been conducted for the 1940–2005 centerlines, evaluation 

is approximate and emphasizes overall spatial and temporal 

trends rather than changes at specific transects. Local 

differences of less than about 1 m in channel altitudes between 

time periods could relate to lidar altitude errors as well as 

paleochannel filling or lateral flood-plain accretion rather than 

changes in actual channel altitude, especially for the more 

recent and shorter time periods after 1968. Larger changes 

owing to deposition are plausible for the 1870–1940 period. 

Coherent patterns over several kilometers, and particularly 

over many time periods, however, likely indicate systematic 

changes in channel altitude across time.

From this perspective, the strongest evidence for 

persistent channel incision is within the South Fork and Upper 

Valley segments (fig. 49). Observations for the South Fork 

are incomplete because of limited aerial photograph coverage 

for some periods, but channel lowering is apparent for much 

of the Sprague River above FK 90.0, perhaps extending 

tac14-0898_fig 48

2

1

0

Altitude, in meters from arbitrary datum

2004 lidar topography

2005 2000 1975 1968 1940

Centerline positions

1940-1968

1968-1975

1975-2000

2000-2005

2004 Channel Paleochannels

Figure 48. Flood-plain transect, illustrating the approach for 

assessing vertical channel movement from intercepts between 

channel centerline positions and 2005 lidar topography, 

Sprague River study area, Oregon.

downstream to FK 86.0 in the Beatty Gap valley segment. 

For the 1940–1968 period, apparent incision exceeded 1 m 

in many locations within these three valley segments, with 

lowering also possibly evident in the Council Butte valley 

segment during this time period. After 1968, however, changes 

in channel centerline altitude show no systematic changes 

along the main-stem Sprague River.

Incision in the North Fork Sprague River valley segment 

is difficult to assess because of limited aerial photograph 

coverage. Nevertheless, local incision, or more likely, lateral 

migration with rapid bar and flood-plain building, may 

be indicated by as much as a 1.3-m difference in present 

centerline altitudes between NFFK 2.0 and 4.0 for 2000 and 

2005 channel locations (fig. 49). The Sycan River shows little 

spatial or temporal systematic patterns in channel altitude 

changes, except for the downstream part of the Coyote 

Bucket valley segment, which likely represents bar and 

flood-plain building.

Figure 49. (On opposite page) Spatial trends in channelcenterline altitude differences, as mapped from 2004 (lidar) 

in conjunction with sequential channel centerline positions, 

as mapped from General Land Office (GLO) maps and aerial 

photographs taken in 1940, 1968, 1975, 2000, and 2005, Sprague 

River study area, Oregon. Measurements at flood-plain transects 

are spaced 200 meters apart. GLO-to-1940 channel-altitude 

differences were determined only for parts of Council Butte and 

Beatty-Sycan valley segments where channel was meandered. 

Observations from South Fork, North Fork, Lower Sycan, and 

Coyote Bucket valley segments are limited for some time periods 

by incomplete map and photographic coverage.
Channel and Flood-Plain Conditions and Processes 65

tac14-0898_fig 49

About 1870 to 1940

1940 to 1968

1968 to 1975

1975 to 2000

2000 to 2005

1940 to 2005

No data

-2.0

-1.0

0

1.0

2.0

0 10 20

Sycan River

flood-plain

kilometer

Lower

Sycan

Coyote

Bucket

2.5

-2.0

-1.0

0

1.0

2.0

0 10 20 30 40 50 60 70 80 90 100 110

Sprague River and South Fork Sprague River flood-plain kilometer

Channel altitude change, in meters

No data

North

Fork

0 10

North Fork Sprague

River flood-plain kilometer

-2.0

-1.0

0

1.0

2.0

-3.5 -6.1

-2.0

-1.0

0

1.0

2.0

Chiloquin

Canyon

Braymill Kamkaun

Spring

S’Ocholis 

Canyon

Council Butte Beatty

Gap

Upper 

Valley

South

Fork

BeattySycanButtes of 

the Gods

-2.0

-1.0

0

1.0

2.0

-2.0

-1.0

0

1.0

2.0

EXPLANATION

Valley segment

 boundary
66 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Results of this centerline analysis are consistent with 

the stratigraphic records: There is no evidence of substantial 

incision throughout most of the Sprague River corridor. The 

main areas of likely historical incision are in the South Fork 

valley segment, and possibly in parts of the Upper Valley and 

Beatty Gap valley segments, although this incision mostly 

pre-dates 1975.

Effects of the 2006 High Flows

High flows in 2006 (fig. 50) provided an opportunity to 

investigate channel and flood-plain processes associated with 

the greatest flooding since WY 1999 (since WY 1996 on the 

Sycan River and on the Sprague River near Beatty Gap; fig. 2). 

In WY 2006, mean daily discharge exceeded 80 m3/s on the 

Sprague River near Chiloquin (streamflow-gaging station 

11501000) for many days in December and January from 

rain and snowmelt, with the largest discharge of 101.7 m3/s 

on January 5, 2006. Earlier during this period of high flow, 

peak flow exceeded 86 m3/s on January 1, 2006 at the Sprague 

River streamflow-gaging station (station 11497500) near 

Beatty Gap. During the following spring, regional snowmelt 

raised flows in April and May 2006, resulting in two peaks 

of about 90 m3/s near Chiloquin. The Sycan River also had 

its greatest flow of the year during this late April and early 

May snowmelt flow, peaking at 67 m3/s on May 1, 2006. The 

combined effects of the December–January and April–May 

runoff episodes were two peaks on the main-stem Sprague 

River, both exceeding 90 m3/s, but the first of shorter duration 

compared to the longer spring runoff to which the Sycan River 

also contributed significantly (fig. 50).

Distribution and Character of Flood Deposits

Between June 23 and July 15, 2006, the effects of these 

large flows were surveyed by mapping and measuring deposit 

characteristics along most of the main-stem Sprague River. 

At each of 70 measurement sites (fig. 51), spaced an average 

of 1.7 km apart, we measured deposit thickness, texture, and 

altitude relative to the low-flow water surface, and, where 

possible, surveyed the altitude of the highest evidence of flow 

from WY 2006 (fig. 52; appendix G).

The goal of these surveys was to sample sites of evident 

deposition at about 1-km intervals along the river corridor. 

Sparse deposits in some reaches necessitated longer distance 

intervals, as did time constraints imposed by far-spaced river 

access locations. Therefore, distance intervals between sample 

locations are not even, with larger gaps between sites mainly 

in the Council Butte, Buttes of the Gods, and S’Ocholis 

Canyon valley segments. Each depositional site was classified 

as either a bar or flood-plain deposit (appendix G).

tac14-0898_fig 50

Water year 2006

Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept.

Mean daily discharge, in cubic meters per second

0

20

40

60

80

100

Sprague River near Chiloquin, 11501000

Sprague River near Beatty, 11497500 

Sycan River below Snake Creek, 11499100

Mean daily

discharge

(in cubic meters per second)

EXPLANATION

Mean peak

discharge*

Streamflow-gaging station

42.9 m3/s

45.1 m3

/s

77.9 m3

/s

*Mean peak annual discharge for period of record:

Sprague River near Chiloquin = 77.9 m3

/s (1921–2011 with gaps)

Sprague River near Beatty = 45.1 m3

/s (1914–1991 with gaps)

Sycan River below Snake Creek = 42.9 m3

/s (1974–2007)

Figure 50. Mean daily discharge during water year 2006 for 

select streamflow-gaging stations, Sprague River Basin, Oregon.

At each sampling site, we excavated through the 

2006 flood deposits to the preexisting surface, apparent at 

all sites by buried vegetation (fig. 53). At some locations, 

we could infer separate deposits resulting from the two 

high‐flow episodes on the basis of stratigraphic breaks or 

more definitively by young vegetation that had germinated 

in the intervening period between the early January peak 

and the April and May high flows. However, distinguishing 

the deposits from the specific high flows generally was not 

possible, so the total thickness and texture of the deposit was 

measured and summarized for analysis. Texture was fieldcategorized into broad grain-size classes ranging from gravel 

to silt-clay.
Channel and Flood-Plain Conditions and Processes 67

tac14-0898_fig 51

Base map modified from Watershed Sciences digital data, 1-meter resolution, and U.S. Geological Survey 

digital data, 10-meter resolution Projection: UTM, Zone 10N, Datum: North American Datum of 1983 (NAD 83)

N Synoptic sites

Channel centerline, 2005

121°50' 121°40' 121°30' 121°20' 121°10' 121°

42°

30'

42°

20'

Sprague River

Sycan River

North Fork Sprague River

South Fork Sprague River

0 5 10 KILOMETERS

0 5 10 MILES

EXPLANATION

Figure 51. Sites assessed in the summer of 2006 for water year 2006 sediment deposition and flood altitude, Sprague River Basin, 

Oregon.

The top of the excavated sequence at each site was 

surveyed relative to the Sprague River water surface by hand 

level and stadia. Additionally, the highest preserved evidence 

of 2006 flow stage was surveyed, commonly consisting 

of flotsam or detritus entangled in vegetation and fencing. 

In locations of low flood plains, this evidence provides a 

minimum local estimate of the maximum 2006 flood stage. 

During the course of mapping, the Sprague River flow varied 

from 8.7 m3/s to 12.7 m3/s. Therefore, all surveyed altitudes 

were adjusted to a reference discharge of 11.5 m3/s (which 

slightly exceeds the median daily flow of 9.7 m3/s) on the 

basis of the stage-discharge rating for USGS streamflow 

gaging-station 11501000, Sprague River near Chiloquin, 

Oregon, at FK 8.3. This resulted in altitude adjustments 

ranging between -0.22 and 0.08 m (appendix G).

Maximum flood stages along the main-stem Sprague 

River were highest in the confined valley segments, such as 

Beatty Gap and S’Ocholis Canyon, and downstream in the 

Kamkaun Spring valley segment (figs. 52, 54). In several 

reaches, maximum flood stage was more than 2 m higher than 

the altitude of the 11.5 m3/s reference discharge. The lowest 

flood stages were in the wide and low-gradient Council Butte 

and Buttes of the Gods valley segments, where maximum 

2006 flood stages were 1.2–1.5 m above the reference altitude. 

Even in these reaches, however, maximum flood stages 

inundated large areas of the flood plain.

Deposit distribution and characteristics varied among 

the valley segments (fig. 52). The thickest, coarsest, and some 

of the highest deposits are in the Beatty Gap valley segment, 

where coarse sand was deposited as high as 1.85 m above the 

reference discharge altitude. By contrast, no flood deposits 

were observed more than 1 m above the reference discharge 

altitude in the Beatty-Sycan, Council Butte, or Buttes of 

the Gods valley segments. Coarse sand and gravel typically 

was deposited within 1 m of the reference discharge stage. 

Finer sand, silt, and clay were the dominant constituents of 

higher deposits.

The thickest and coarsest deposits were on bars, whereas 

finer and thinner deposits typified flood-plain depositional 

sites (figs. 52 and 53). For example, the median 2006 

deposit thickness on bars was 21 cm, whereas the median 

accumulation on flood plains was about 4 cm. All bar deposits 

were sand and gravel. By contrast, more than 60 percent 

of the flood-plain sites accumulated fine sand, silt, or clay, 

typically at altitudes higher than bar sites. Where stratigraphy 

was evident, inclined bedding indicated that most of the bars 

formed by lateral accretion, contrasting with horizontally 

bedded vertical accretion on flood plains. This pattern is 

consistent with the long-term stratigraphic records, especially 

those on the North Fork Sprague River and Sycan River where 

stratigraphic relations indicate laterally accreted coarse sand 

transitioning up into vertically accreting finer sand and silt 

(figs. 11, 14).
68 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 52

Deposit thickness, in centimeters

0

20

40

60

80

100

120

Bar Flood plain Bar Flood plain

2006 deposit altitude 2006 deposit thickness

Deposit altitude, in meters above reference altitude

-0.5

0.0

0.5

1.0

1.5

2.0

0

20

40

60

80

100

120

A

B

Deposit altitude, in meters above reference altitude

Distance along 2005 centerline, in kilometers

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Reference water altitude, Q = 11.5 m3/s

Approximate maximum 2006 flood stage

Kamkaun

Springs

S’Ocholis 

Braymill Canyon Council Butte

Beatty

Gap

Upper 

Valley

BeattySycanButtes of

the Gods

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

Discharge (Q) 

= 101.7 m3

/s

Q = 86.1 m3/s

m3/s, cubic meter per second

Surveyed evidence of maximum 2006 flood stage

(in many locations, a minimum indicator)

Depositional Setting

Texture

Overbank flood plain deposit, generally vertically accreted

Channel-margin bar deposit, generally laterally accreted

Clay and silt

Silt and fine sand

Sand

Coarse sand and gravel

50th percentile

75th percentile

95th percentile

25th percentile

5th percentile

EXPLANATION

Figure 52. Summary observations of 2006 survey of deposits and inundation levels of water year 2006 floods, including 

(A) longitudinal trends of deposits and inundation evidence (with peak flow values from Sprague River near Chiloquin 

[streamflow-gaging station 11501000] and Sprague River near Beatty [streamflow-gaging station 11497500]; peak flow 

at both sites was on January 1, 2006); and (B) summary plots of 2006 flood deposit texture and altitude, grouped by bar 

and flood-plain settings, main-stem Sprague River, Oregon. No observations were made in the Chiloquin Canyon valley 

segment. All altitudes are adjusted to the stage associated with 11.5-cubic-meters-per-second discharge (Q) at U.S. 

Geological Survey streamflow-gaging station 11501000.
Channel and Flood-Plain Conditions and Processes 69

tac14-0898_fig 53

A

2006 deposition

B

2006 deposition

Figure 53. Examples of sediment deposition resulting from 

the 2006 high flows, including (A) overbank deposition of 

4.5 centimeters of silt and sand on low flood-plain surface, Council 

Butte valley segment (survey site 6/28/06-8); and (B) deposition of 

33 centimeters of sand on point bar, Beatty Gap valley segment

(survey site 6/26/06-1), main-stem Sprague River, Oregon. 

Photographs taken by J.E. O’Connor, U.S. Geological Survey; 

(A) June 28, 2006; (B) June 26, 2006.

FK 31

FK 32

Direction

of flow

FK 29

FK 30

FK 33

Figure 54. Kamkaun Spring 

valley segment, looking north, 

main-stem Sprague River, Oregon, 

during high flow in water year 

2006. Photograph courtesy of Greg 

Koonce, Inter-Fluve Inc., May 16, 

2006 (used with permission).
70 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Nearly all the sand and gravel particles, particularly 

in the coarse sand-to-granule range of 1–4 mm, were lightcolored pumice grains (fig. 53B). This observation also is 

consistent with the stratigraphic records from the length of 

the study reach, which show nearly all coarse sand deposits 

that post-date the Mazama eruption dominantly composed of 

pumiceous materials.

Measured Sediment Transport

In a sediment study commissioned by The Klamath 

Tribes, Graham Matthews and Associates (2007) measured 

streamflow and sediment transport at 14 sites in the Sprague 

River Basin between February 2004 and January 2006. 

Included in this measurement period is the high flow 

resulting from the winter storm of late December 2005 and 

early January 2006 (fig. 50). During these elevated flows, 

Graham Matthews and Associates (2007) report four to eight 

suspended sediment measurements from each of seven sites 

along the main-stem Sprague River, Sycan River, South Fork 

Sprague River, and North Fork Sprague River (fig. 55). Five of 

these sites are within the study area; the other two are on the 

North Fork and South Fork Sprague Rivers less than 5.5 km 

upstream of the alluvial part of the river corridors within the 

study area.

Flow at all sites peaked on December 31, 2005, except 

for the main-stem Sprague River site at Godawa Springs 

Road, which peaked the next day on January 1, 2006, and the 

Sycan River site at SYFK 2.3, which peaked a week earlier 

on December 23, 2005 (Graham Matthews and Associates, 

2007). Sediment concentration measurements were made at 

discharges ranging from 2.61 m3/s (with a suspended-sediment 

flux of 0.0055 kilogram per second [kg/s]) on the North 

Fork Sprague River at Road 3411 (5.5 km upstream of the 

study area) to 74.2 m3/s (with suspended-sediment load of 

38.8 kg/s) on the Sprague River at Godawa Springs Road 

(FK 78.2) (Graham Matthews and Associates, 2007). This 

74.2 m3/s measurement at the most downstream site was 

very close to the peak flow of 75.4 m3/s on January 1, 2006. 

Additionally, this measurement site had the highest measured 

sediment concentration of 523 milligrams per liter (mg/L). 

They also made measurements at discharges within 95 percent 

of the peak discharge on December 31, 2005 for the North 

Fork Sprague River at NFFK 0.7, South Fork Sprague River 

at Picnic Area (1.5 km upstream of where the South Fork 

Sprague River enters the study area, equivalent to FK 107.6), 

South Fork Sprague River upstream of Fishhole Creek (FK 

100.1), and South Fork Sprague River at Ivory Pine Road 

(FK 94.3).

In addition to high sediment concentrations near the time 

of peak discharge, all sites had high sediment concentrations 

and mass flux early during the measurement period. Later 

measurements at all sites showed substantial decreases in 

concentrations and flux during the course of the flood (fig. 55). 

This hysteresis (changing sediment concentration relative 

to streamflow during a period of high flow) is most evident 

for the upstream and tributary sites, where sediment fluxes 

decrease by a factor of 10 or more relative to discharge on 

the North Fork Sprague River at Road 3411, South Fork 

Sprague River at Picnic Area, and Sycan River at Drews 

Road. Hysteresis is present but to a lesser degree on the other 

downstream sites, particularly the main-stem Sprague River 

at Godawa Springs Road, where sediment concentration 

decreased by a factor of five during the flood.

Such hysteresis commonly owes to sediment depletion 

during the period of high flow. Sediment depletion may be 

more rapid in smaller streams and during initial wet-season 

flows (Williams, 1986; Smith and Dragovich, 2009). The 

pronounced peak in sediment fluxes and concentrations 

associated with peak flows in the Sprague River indicates 

entrainment from additional sediment sources at high flows 

(likely bank and channel materials), as well as from floodplain diversion channels (Michael Hughes, Oregon Institute of 

Technology, written commun., 2013).

The spatial evolution of sediment concentrations also 

clarifies sediment sources, especially along the South Fork and 

main-stem Sprague Rivers. Four sites had closely coincident 

measurements, including measurements at very close to peak 

discharge (fig. 56; Graham Matthews and Associates, 2007). 

These measurements show suspended sediment concentration 

markedly increasing between the South Fork Sprague River 

at Picnic Area (FK about 107.6) and the next downstream 

site above Fishhole Creek (FK 100.1). At peak discharge 

and for the three measurements leading up to the peak flow, 

sediment concentration increased in this 6.5-km-long reach 

by factors ranging from 1.4 to 4.8, despite the drainage area 

increasing only by a factor of 1.2. For the December 21, 23, 

30 and 31 measurements, sediment concentrations diminished 

downstream of the measurement site upstream of Fishhole 

Creek. Together, these measurements indicate significant 

sediment entrainment in the South Fork valley segment 

above FK 100.1. Because tributaries are few in this reach, 

channel and bank erosion was probably a source of some 

of this suspended sediment. Additional sources of sediment 

in this reach likely include eroding bank crevasses or cuts, 

which facilitate sediment transport from flood-plain surfaces 

and irrigation channels into the South Fork Sprague River 

(Michael Hughes, Oregon Institute of Technology, written 

commun., 2013).

Entrainment patterns apparently changed at or soon 

after peak flow. On January 1, 2006, sediment concentrations 

and total flux increased downstream, culminating with 

a sediment concentration of 523 mg/L (and a suspended 

load flux of 38.8 kg/s) on the Sprague River at Godawa 

Springs Road (FK 78.2). This pattern also was indicated by the 

January 6, 2006 measurements, although at much lesser levels. 
Channel and Flood-Plain Conditions and Processes 71

tac14-0898_fig 55

Sycan River at Drews Road

(drainage area 1,445 km2

; SYFK 2.3)

December 2005 January 2006

0.01

0.1

1

10

100

North Fork Sprague River below Five Mile Creek

(drainage area 536 km2

; NFFK 0.7)

Discharge, in cubic meters per second

0.01

0.1

1

10

100

North Fork Sprague River at Road 3411

(drainage area 187 km2

)

<0.01

0.01

0.1

1

10

100

Sprague River at Godawa Springs Road

(drainage area 1,473 km2

; FK 78.2)

December 2005 January 2006

0.01

0.1

1

10

100

South Fork Sprague River at Ivory Pine Road

(drainage area 753 km2 ; FK 94.3)

0.01

0.1

1

10

100

South Fork Sprague River above 

Fishhole Creek

(drainage area 344 km2

; FK 101.5)

Suspended sediment flux, in kilograms per second

0.01

0.1

1

10

100

South Fork Sprague River at Picnic Area

(drainage area 280 km2

; about FK 107.9)

0.01

0.1

1

10

100

0.01

0.1

1

10

100

20 24 28 1 5 8 20 24 28 1 5 8

Discharge, outline indicates

measurement near peak discharge 

Sediment flux, outline indicates 

measurement near peak discharge

EXPLANATION

Stream network relations

Abbreviations: km2, square kilometer; 

NFFK, North Fork Sprague River flood-plain kilometer; 

SYFK, Sycan River flood-plain kilometer; 

FK, flood-plain kilometer

Figure 55. Discharge and suspended sediment transport between December 20, 2005 and 

January 7, 2006 period of high flows for seven locations in the Sprague River Basin, Oregon. Data 

source: Graham Mathews and Associates (2007).
72 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 56

0

20

40

60

80

0

100

200

300

400

A. December 21, 2005

17031603

1742

1408

0

20

40

60

0

100

200

300

B. December 23, 20051433

1433

1401

1542

1653

0

20

40

60

0

100

200

300

C. December 30, 2005 1720

141014421258

0

20

60

80

100

0

100

200

300

400

500

D. December 31, 2005 1512

172817091633

40

Flood-plain kilometer

75 80 85 90 95 100 105 110

0

20

40

0

100

200

F. January 6, 2006

1724161514491318

0

20

40

60

80

100

120

0

100

200

300

400

500

600

E. January 1, 2006

194518451608

North Fork Sprague River

Fishhole Creek

0

20

40

60

80

100

120

0

100

200

300

400

500

600

G. Near peak discharge

December 31, 2005; 1633

December 31, 2005; 1709

December 31, 2005; 1728

Jan. 1, 2006; 1945

 North Fork 

Sprague River

Fishhole Creek

Suspended sediment flux, in kilograms

per second

Discharge, in cubic meters per second;

75 80 85 90 95 100 105 110

Flood-plain kilometer

Suspended sediment concentration,

 in milligrams per liter

Discharge 

Suspended-sediment concentration 

Suspended-sediment flux 

Hour of day

EXPLANATION

Discharge, in cubic meters per second;

Suspended sediment flux, in kilograms per second

Suspended sediment concentration, in milligrams per liter

Figure 56. Longitudinal trends in discharge and suspended 

sediment transport for 6 days of observations (A–F) and at nearpeak discharge (G). Graphs were developed from data reported 

in Graham Mathews and Associates (2007).
Channel and Flood-Plain Conditions and Processes 73

The downstream increase in sediment concentration and load 

must result from sediment derived from sources downstream 

of the North Fork Sprague River confluence with the 

main-stem Sprague River because the January 1, 2006, North 

Fork suspended-sediment load at NFFK 0.07 together with 

the load at South Fork Sprague River at Ivory Pine Road 

(FK 94.3, 0.9 km upstream of the North Fork Sprague River 

confluence) do not come close to accounting for the load 

measured downstream at nearly the same time on the Sprague 

River at Godawa Springs Road. This sediment input most 

likely resulted from channel and bank erosion or tributary 

inputs in the Upper Valley or Beatty Gap valley segments.

Channel and Flood-Plain Processes

The geomorphic mapping and historical observations, in 

combination with the observations and trends evident from the 

map and photograph analyses and synoptic survey, provide a 

basis for interpretation of channel and flood-plain processes. 

Additionally, these observations can support inferences as to 

how geologic conditions and human alterations have affected 

these processes.

Channel Processes

Channel processes are influenced broadly by basin‐scale 

conditions of flow and sediment supply (in particular 

bed material) and, at the segment scale, channel slope. 

Therefore, attributes such as channel width, flow, and slope 

are strongly correlated. However, specific local morphologic 

characteristics and associated physical habitat conditions 

relate to local interactions among sediment transport, bed 

and bank materials, depositional processes, and lateral and 

vertical erosion.

Sediment Transport

Bed-material and suspended sediment transport are 

important channel-forming processes in the Sprague River 

Basin. Transport and deposition of bed material composed 

of sand and gravel builds bars; therefore, they are factors in 

building new flood-plain surfaces as well as in promoting 

lateral channel migration, including cutoffs and channel 

avulsions. The suspended load of very fine sand, silt, and clay 

is the dominant sediment accumulating on established flood 

plains deposits, therefore influencing bank erosion processes 

and riparian vegetation. 

Measurements of suspended sediment load during 

2004–2006 by Graham Mathews and Associates (2007) 

show that the South Fork Sprague River contributes about 

60 percent of the total suspended sediment load to the Sprague 

River, with the North Fork Sprague River (27 percent) and 

Sycan River (13 percent) contributing markedly less. The 

overall measurement program of Graham Mathews and 

Associates, as well as the measurements made during the 

December 31, 2005 and January 1, 2006 high flows, show that 

much of the suspended sediment originates in the North Fork 

and South Fork valley segments (figs. 55, 56). This sediment 

possibly is the result of lateral channel erosion, bed incision, 

or tributary input. The historical evidence of possible incision 

in the North Fork and South Fork valley segments suggests 

that bed incision, either within the two forks themselves or 

possibly by incising tributaries and irrigation ditches graded 

to the rivers, probably is an important factor in the increased 

suspended sediment loads. This sediment may result in part 

directly from bed erosion, but probably more significantly 

from enhanced channel widening within incising reaches.

Some of the suspended sediment load is deposited on 

flood-plain surfaces, resulting in the vertical accretion evident 

in all of the stratigraphic sections of post-Mazama flood 

plains in the study area (figs. 5, 8, 9). Downstream of the 

confluence of the North Fork and South Fork Sprague Rivers, 

the sequence of high flows in WY 2006 deposited as much 

as 20 cm of sediment (median thickness 4 cm), presumably 

composed of suspended sediment load onto flood-plain 

surfaces as high as 1.5 m higher than the low-flow water 

surface. This deposition might be an important factor in the 

overall sediment budget. Suspended sediment load estimates 

by Graham Mathews and Associates (2007) indicate that the 

load passing the measurement site near the basin outlet near 

Chiloquin was only 63 percent of the combined load delivered 

by the North Fork and South Fork Sprague Rivers, and the 

Sycan River between November 2, 2005 and January 6, 2006. 

This indicates substantial net deposition along the main-stem 

Sprague River, probably on floodplains. The presence of 

cesium-137 (Cs137) in the near-surface floodplain stratigraphy 

(as much as 20 cm below the land surface; appendix D) 

also indicates significant post-1950 deposition on many 

flood-plain surfaces.

Flood-plain deposition requires flood-plain inundation. 

During the 2006 flood, much of the flood plain was inundated 

along the main-stem Sprague River as well as along at least 

the lower North Fork Sprague River (figs. 9, 52, 54). However, 

if the frequency or extent of flood-plain inundation is 

decreased by channel incision, levee construction, or reduced 

formation of low flood-plain surfaces (mainly from channel 

migration), downstream sediment loads may increase because 

of the combined effects of less overbank deposition and 

greater in-channel flow velocities accelerating bank erosion 

and increasing transport capacity.

Bed-material transport is evident by the bars along the 

length of the study reach (figs. 15, 18, 39), but little is known 

about actual transport rates. Graham Mathews and Associates 

(2007) measured bedload 14 times among 5 locations during 

WYs 2004 and 2005. From six measurements of the Sycan 

River at Drews Road (SYFK 2.2), Graham Mathews and 

Associates estimated that bedload constituted about 30 percent 

of the total sediment load, a value similar to the 35 percent 

estimated from five measurements on the South Fork Sprague 

River picnic area just upstream of the study area at FK 107.6. 
74 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Both of these sites are steeper than most of the study 

area, and bed-material transport rates likely are lower and 

constitute a smaller fraction of the total sediment load in the 

lower-gradient main-stem valley segments than at these sites.

The reaches of greatest bed-material transport are those 

where both transport capacity (chiefly a function of channel 

slope and flow depth) and bed-material supply are high. 

These conditions can be inferred in part from the spatial and 

temporal distribution of bars. Bars are more abundant where 

the South Fork and North Fork Sprague Rivers emerge onto 

the alluvial valleys from the uplands surrounding the study 

area into the South Fork and North Fork valley segments. 

However, the greatest frequency and area of bars is near 

the confluence of the Sprague River with the Sycan River 

in the Beatty-Sycan and Council Butte valley segments 

(figs. 18, 39), pointing to the Sycan River as a key source 

of bed material (Hughes and others, 2009). Bars also are 

abundant in the Buttes of the Gods segment. The scarcity of 

bars in the Chiloquin Canyon and Braymill segments is the 

consequence of the greater slope and confinement of these 

reaches, which results in most bed-material sediment delivered 

from the low‐gradient and unconfined reaches upstream being 

transported efficiently through these segments.

The relatively high volume of bed material associated 

with the Lower Sycan valley segment compared to the North 

Fork and, even more so, the South Fork valley segments 

(figs. 18, 39) owes to the much greater sand supply in the 

Sycan River. The much thicker accumulation of Mazama 

pumice in the Sycan River watershed compared to the other 

watersheds (Sherrod and Pickthorn, 1992), in conjunction 

with locally eroding banks of Sycan flood deposits (fig. 7), 

provides abundant sand-size pumiceous material to the Sycan 

River. The North Fork Sprague River and South Fork Sprague 

River drainages were blanketed with respectively thinner 

accumulations of Mazama tephra—particularly sand-size 

accumulations. Therefore, these drainages have had less 

bed‐material transport during the late Holocene. As a result, 

bar frequency is less upstream of the Sprague River confluence 

with the Sycan River, and bars are very sparse upstream on the 

South Fork Sprague River. During late Holocene and historical 

periods of wetland soil formation, evident in the stratigraphy 

of both the North Fork (fig. 9) and South Fork (fig. 8) Sprague 

River segments, there likely was little bed-material transport 

in these valley segments.

The much greater bar frequency mapped from the 

1968 aerial photographs compared to the 1940 and 2000 

aerial photographs indicates the importance of large flows 

in transporting bed material. In this case, the December 26, 

1964, flood almost certainly is responsible for significant 

bed-material transport and resulting bar formation and 

expansion, similar to but to a greater degree than the 

depositional patterns documented by the survey of effects 

of the 2006 high flows. The relatively greater importance of 

high flows in transporting bedload is consistent with the few 

measurements by Graham Mathews and Associates (2007) and 

the observations from more systematic bed-material transport 

measurements and modeling studies for other western Oregon 

rivers (Wallick and others, 2010, 2011).

Overall bed-material transport rates likely are low 

in the Sprague River. The absence of continuous sand 

and gravel bed-material cover of the channel bottom 

(all valley segments have significant reaches of channel 

bottom composed of consolidated silt and clay) indicates 

that bed-material supply is exceeded by transport capacity 

at decadal to century time scales, despite low transport 

capacities in most reaches because of low channel gradients. 

Bed-material supply is limited in the Sprague River Basin 

because, like in the Deschutes River Basin to the north, the 

basin geology of mainly volcanic rocks does not produce 

substantial bed material (O’Connor, and others, 2003b). Given 

the composition of modern and late Holocene bed-material 

deposits, pumiceous sand from the 7,700 cal yr BP Mazama 

eruption, derived either from upstream parts of the basin or 

from the reworking of flood-plain deposits, continues to be a 

major source of bed material. The low supply and transport 

rates partly explain the overall scarcity of bars as well as the 

low channel migration rates of the main-stem Sprague River.

Bar Building

In addition to providing an index to bed-material 

transport rates, bar deposition affects channel and flood-plain 

morphology by promoting channel migration and by providing 

a foundation for young and low flood-plain surfaces. Bare 

bars also provide germination sites for riparian vegetation, 

particularly rushes, sedges, and riparian grasses. Most of the 

bed material forming bars is pumiceous sand, mainly derived 

from the Sycan River Basin but also, to a lesser degree, from 

the North Fork and South Fork Sprague Rivers. An unknown 

but probably sizeable fraction of modern bar material is 

from the reworking of older (but post-Mazama) flood-plain 

deposits, including the Sycan flood deposits, by lateral erosion 

and channel migration.

Where visible in stratigraphic sections and during the 

2006 survey, dipping beds of sandy material indicate that 

bars grow laterally. In most situations, bar growth is in the 

form of point bars, but also locally as mid-channel islands 

and accumulations in flow separation zones formed by 

woody debris accumulations, natural and artificial channel 

obstructions, and channel bifurcations. Stratigraphic sections 

along the Sycan River and North Fork Sprague River (figs. 11, 

14) show that these point bars gradually evolve into floodplain surfaces, with bedding indicating a transition from lateral 

to vertical accretion.

Bars are a factor promoting bank erosion and lateral 

migration. Bars deposited on the inside of channel bends and 

in mid-channel force flow to the outside of bends and channel 

margins, enhancing bank erosion and lateral migration. 

Bars are sparse in the Sprague River study area compared to 

many alluvial rivers; nevertheless, their frequency correlates 
Channel and Flood-Plain Conditions and Processes 75

with migration rates (fig. 46A). This finding also is consistent 

with the evident transformation recorded by the stratigraphy 

of the fluvial system at the time of the Mazama eruption from 

one of low-energy and possibly locally unchanneled floodplains and wetlands to a connected fluvial system consisting of 

channels migrating across the flood plain.

Bank Erosion

In conjunction with bar building and channel migration, 

bank erosion is a ubiquitous process in the Sprague 

River study area. Judging from the sediment transport 

measurements, bank and channel erosion, especially in 

the Upper Valley and South Fork valley segments, is a 

significant contributor to suspended sediment loads. Bank 

erosion is a complex process (Simon and others, 1999) 

involving fluvial processes of direct entrainment and 

undercutting, gravity-caused mass movements and raveling, 

and disturbances such as trampling by animals (including 

livestock) and effects of debris, waves, and vehicular traffic. 

The relative effectiveness of different processes is affected by 

the nature of the bank materials, bank and channel geometry, 

flow conditions and vegetation (Florsheim and others, 2008).

Bank erosion is most evident in the study area in the 

form of vertical banks, commonly flanked at their base with 

down‐dropped blocks of flood-plain sediment (fig. 57). 

Although approaches are available for quantitatively assessing 

bank erosion, especially for low-energy and fine-grained 

fluvial systems such as the Sprague River (Simon and others, 

1999; Pollen-Bankhead and Simon, 2008), our observations 

were qualitative, drawn from inspections of banks during the 

course of stratigraphic analyses and the survey of the effects of 

the WY 2006 high flows.

Banks in the Sprague River study area are mostly formed 

in young, fine-grained flood-plain deposits, particularly in the 

unconfined reaches. For example, the Kamkaun Spring, Buttes 

of the Gods, Council Butte, Beatty-Sycan, Upper Valley, 

South Fork, and North Fork valley segments all have more 

than 80 percent of their year 2000 channels wholly contained 

within the geomorphic flood plain (fig. 16), which mostly 

post-dates the Mazama eruption of 7,700 cal yr BP. The case 

for the Lower Sycan valley segment would be similar except 

that the channel is within 10 m of the Sycan flood deposits for 

23 percent of its length.

The different bank materials apparently correlate with 

different mechanisms and consequences of bank erosion. The 

young flood-plain deposits—with their typical stratigraphy of 

unconsolidated pumiceous sand overlain by more cohesive 

very-fine sand, silt, and clay locally strengthened by dense 

root networks—are subject to undercutting, especially on 

the outside of bends where boundary shear stress is greatest 

(Dietrich and others, 1979). In many cases, such undercutting 

during WY 2006 promoted down dropping of cohesive 

blocks of overlying flood plain, resulting in stepped bank 

forms. These fallen blocks, which appear to have moved by 

toppling and slip failure, provide substrate for colonization by 

tac14-0898_fig 57

A

B

Figure 57. Examples of bank erosion with down-dropped 

blocks of flood-plain deposits, including (A) left-bank erosion 

in S’Ocholis Canyon valley segment (June 29, 2005), and (B) 

right-bank erosion in Kamkaun Spring valley segment (June 25, 

2006), main-stem Sprague River, Oregon. Photographs taken by 

J.E. O’Connor, U.S. Geological Survey.

saturation-tolerant species (fig. 57A). The Sycan River flood 

plain, with its more prevalent pumiceous sands and overall 

greater channel slopes than other valley segments, appears to 

be especially susceptible to bank erosion. Young flood-plain 

deposits in the South Fork valley segment do not have thick 

pumiceous sands at the base of their stratigraphic sections, 

perhaps inhibiting bank erosion by undercutting and mass 

wasting, although the sediment transport analyses indicate that 

this segment is a major contributor of suspended sediment.
76 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Bank erosion where the channel impinges on older 

surfaces is less common because contact between the active 

channel and older surfaces is rare in most reaches (fig. 16). In 

the few locations where the present channel is eroding edges 

of pre-Mazama terraces and fans, erosion rates appear to be 

slow with less undercutting because of the more consolidated 

character of sand and gravel at the base of these stratigraphic 

sections compared to the pumiceous sand at the base of the 

late Holocene flood-plain deposits. Tall raw banks formed in 

older materials locally extend along the channel for distances 

exceeding tens of meters. These banks appear to erode slowly, 

with freeze-thaw, desiccation, and biogenic disturbance 

possibly being the main processes loosening bank materials, 

thereby facilitating fluvial entrainment and helping to maintain 

unvegetated faces.

The Sycan River has a distinctive situation that locally 

promotes bank erosion. Within the Lower Sycan valley 

segment, the channel abuts the Sycan flood deposits along 

about 23 percent of its length (fig. 16). Here, the bank 

stratigraphy is composed of coarse and granular pumiceous 

sand overlying compact silt and clay, with the contact between 

the strata as much as 2.5 m above the low-flow water surface 

(figs. 5, 7). Whereas the pre-Mazama fine-grained flood-plain 

deposits resist erosion, the loose pumiceous sands above are 

exceptionally erodible, especially where vegetative cover is 

disturbed. Erosion is enhanced by water seepage concentrated 

at the basal contact of the granular sand and the underlying 

and less permeable silt and clay. This seepage locally conveys 

the overlying sand to the channel edge. In places, this seepage 

appears augmented by irrigation of the Sycan flood deposits.

Although bank erosion can increase sediment loads, 

cause property and infrastructure loss, and perhaps locally 

adversely affect aquatic and riparian habitat conditions, 

bank erosion also is a key process for maintaining channel 

migration and other key ecologic processes (Florsheim and 

others, 2008). Bank erosion probably is a significant source of 

bed material for the Sprague River and North Fork Sprague 

River, particularly by providing a supply of the pumiceous 

sand, which is an important bar-building material. Locally, 

bank erosion also creates diverse bank and channel-margin 

conditions, especially where blocks of flood-plain sediment 

have down-dropped to low-water levels. Together these 

features create variable hydraulic environments and provide 

many of the low, near-channel surfaces for colonization by 

aquatic and riparian flora (Hughes and Leeseberg, 2009).

Incision

The common cut banks in the Sprague River study area 

are cited as an indicator of recent channel incision (Connelly 

and Lyons, 2007; Rabe and Colonje, 2009). However, 

evidence of historical channel lowering primarily is restricted 

to the upstream parts of the study area, including the South 

Fork, and possibly parts of the North Fork, Upper Valley, and 

Beatty Gap valley segments. No local observations document 

the processes and specific timing, but in these locations, 

incision probably has proceeded by upstream migration 

of knickpoints, as is commonly the case for channels with 

fine‐grained or cohesive beds (Simon and Rinaldi, 2006). Like 

many incised streams (Cooke and Reeves, 1976; Schumm, 

1999), some of these knickpoints may have been initiated 

by diversion or diking leading to flow concentration, or 

by clearing or removal of wood accumulations, including 

beaver dams. For the South Fork Sprague River, particularly 

for the straightened section with levees between FK 97.0 

and 101.1, channel incision probably was partly caused 

by direct excavation of materials from the channel for 

levee construction. In-channel excavation, documented 

by historical observations in the Kamkaun Spring valley 

segment (Greg Harris, oral commun., September 13, 2007), 

may be a factor in other local areas of possible historical 

channel incision in the Upper Valley and Council Butte 

valley segments.

The irregular channel profile along the South Fork 

Sprague River upstream of the diversion structure at the 

Campbell Road Bridge at FK 101.4 (fig. 32) may represent 

active channel erosion. Migrating knickpoints in this upper 

part of the South Fork valley segment would be consistent 

with the higher suspended sediment loads derived from 

this reach during the 2006 high flow (fig. 56). Enhanced 

sediment loads could result from direct sediment introduction 

to the flow either as the knickpoint erodes or from incision 

of diversion channels and bank crevasses connected to the 

lowering channel.

Channel incision can be mitigated locally by gradecontrol structures as well as natural processes such as beaver 

activity and in-channel wood accumulation. The existing 

diversions on the South Fork Sprague River at FKs 100.0 

and 101.5, as well as the shorter structure on the North Fork 

Sprague River at NFFK 1.1 and the in-channel rock placement 

at NFFK 5.2, are all currently protecting upstream reaches 

from incision (fig. 32). Judging from overall profile trends, 

removal of these structures, either planned or by flood, without 

mitigating grade protection measures, likely would trigger 

incision extending perhaps several kilometers upstream.

Channel Substrate

Channel substrate varies across the study area, ranging 

from coarse boulder material in the steep and confined 

Chiloquin Canyon and Coyote Bucket valley segments to 

indurated silt and clay where the channel is flowing directly 

on older Tertiary lacustrine sediment. Additionally, most 

valley segments have patchy to nearly continuous sand and 

gravel on the channel bottom and margins. Placed rock marks 

some fords and former bridge crossings, as well as channel 

restoration and bank protection sites.
Channel and Flood-Plain Conditions and Processes 77

The coarse cobble and boulder substrate in the Chiloquin 

Canyon and Coyote Bucket valley segments and other 

locations where the channel impinges on or is near bedrock 

probably is rarely mobilized. Stable rock accumulations 

locally may promote erosion and deposition of other substrate 

materials by changing local hydraulic conditions. Placed rock, 

however, may be susceptible to displacement in locations of 

bank erosion or channel incision.

Indurated silt and clay substrate is common in several 

valley segments. During the 2006 synoptic survey, we noted 

extensive reaches of this substrate in the Buttes of the Gods 

and the Kamkaun Spring valley segments. Indurated silt and 

clay substrate also is common in the lower part of the Lower 

Sycan valley segment (fig. 34), and was the main substrate 

visible at road crossings of the South Fork Sprague River in 

the South Fork valley segment. Impenetrable silt and clay 

marked the bottom of most augering attempts in the Buttes 

of the Gods and Kamkaun Spring valley segments (figs. 12, 

13). In the Lower Sycan, Buttes of the Gods, and Kamkaun 

Spring valley segments, this indurated substrate is inferred to 

be Tertiary lacustrine sediment on the basis of the pervasive 

jointing, similar to that in roadcut exposures in the area. 

However, in some places (particularly in the Upper Valley 

and South Fork valley segments), the indurated silt and clay 

substrates may be late Quaternary low-energy flood-plain and 

wetland deposits.

The silt and clay substrate erodes into forms commonly 

associated with soft bedrock channels (Richardson and 

Carling, 2005), including flutes, furrows, and potholes. Some 

furrows, particularly in recent meander cutoffs, have low-flow 

water depths exceeding 2 m. These erosional features seem to 

be stratigraphically and structurally controlled, with plucking 

and erosion taking advantage of horizontal weaknesses 

associated with softer strata and vertical zones of weakness 

caused by joints. At low flow in the Buttes of the Gods valley 

segment, several small and short water-surface drops result 

from spill over ledges formed of resistant beds.

This hard substrate probably inhibits channel incision 

in several of the valley segments where it forms much of the 

channel bottom. Where incision has occurred or is ongoing, 

as is probably the case for the South Fork valley segment, 

the resistant silt and clay form persistent and slow-migrating 

knickpoints or short reaches of high channel slope.

In most valley segments, patchy-to-continuous sand and 

gravel (and in places, soft mud) locally cover the indurated 

silt and clay substrates. This sediment represents current 

bed-material supply and transport conditions. These materials 

generally are loose, and the sand-size component is dominated 

by pumice grains. Gravel, typically with a diameter of less 

than 2 cm, locally is common along the channel thalweg in 

several valley segments, and is mostly volcanic clasts. In 

the steeper upstream parts of the Lower Sycan, North Fork, 

and South Fork valley segments, gravel and cobble channel 

bottoms and marginal bars are more common, in places 

forming continuous alluvial channels extending for several 

kilometers. In some reaches, particularly in the Lower Sycan 

and North Fork valley segments, sand and gravel bed material 

is organized into pool and riffle sequences (fig. 33). However, 

the patchiness of alluvial cover in the Sprague River channel 

network indicates that overall bed-material supply does not 

match the transport capacity.

The augering transects, stratigraphic studies, and 

observations from the 2006 survey indicate that bed material 

locally accumulates in areas of reduced flow velocity during 

high flows, particularly downstream of obstructions, on the 

inside of channel bends, and in entrances of side channels. In 

addition to mid-channel and point bars, such deposition locally 

creates sandy bars at the entrance of side channels and can 

promote flow diversion into nascent meander cutoffs.

Spring channels, connecting springs to the main channel 

through the geomorphic flood plain, typically have well-sorted 

pumiceous sand bottoms. For these channels, it appears that 

spring flow is sufficient to mobilize silt and clay, leaving wellsorted sand. In situations where river channel migration or 

avulsions result in the formation of new spring channels, these 

new channels also will likely evolve, through time, to have 

well-sorted sandy beds under conditions of relatively constant 

spring discharge.

Maintaining an alluvial cover on the channel bottom 

depends partly on maintaining a supply of bed material. 

Over millennial time scales, as the supply of pumice sand 

diminishes from the upper parts of the basin, the importance 

of bank erosion and reworking of flood-plain accumulations 

of sand and gravel will grow as a source of sand and gravel 

channel substrate.

Flood-Plain Processes

The overall observations of historical and modern 

flood-plain conditions and trends, as well as inferences 

regarding important channel processes, provide a framework 

for understanding the major flood-plain forming processes. 

These processes include the mechanisms and consequences 

of lateral channel movement across the flood plain—in the 

Sprague River study area, meander growth counteracted by 

meander cutoff and channel avulsion—as well as the overbank 

depositional and erosional processes by which flood-plain 

surfaces are built, eroded, and modified.

Meander Growth

Meander growth strongly contributes to flood-plain 

morphology in the Sprague River study area. Meander 

enlargement provides opportunities for channel cutoffs and 

meander abandonment that result in the overall native floodplain morphology of abandoned channels (and associated 

ponded water and side-channel environments) and multi-level, 

flood-plain surfaces.
78 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

On the Sprague River, meander growth is by the tightly 

coupled processes of bar formation and lateral erosion. 

Judging from the presence of measureable migration rates 

and bar presence in all valley segments, these processes 

appear important to some degree for the entire study area. It is 

primarily the unconfined (either by valley margins or levees) 

segments, however, where meander loops can enlarge to 

promote high sinuosity (fig. 38).

Bar morphology also can indicate patterns of meander 

growth. In particular, the orientation of scroll bars—concentric 

ridges developed on a point bar surface through time as it 

evolves (Lobeck, 1939; Hickin 1974)—support interpretations 

of the direction and type of channel movement. Hooke (1997) 

identified five major types of bar movement: (1) downstream 

translation, (2) upstream translation, (3) expansion (growing 

toward the flood-plain margin), (4) rotation, and (5) 

development of a compound or double-headed meander. 

Scroll bars are more evident in the wide valley segments. The 

dominant types of meander movement indicated by scroll 

bars in the Kamkaun Spring, Buttes of the Gods, Council 

Butte, and Sycan-Beatty valley segments are downstream 

translation (fig. 12) and expansion (fig. 54), although some 

bars show evidence of upstream translation and development 

of compound meanders.

The slow rates of meander growth for the Sprague 

River and its major tributaries owe to the low overall bedmaterial transport rates and the low stream power. Channel 

confinement and slope are local factors also apparently 

exerting control on migration rates at the segment scale. The 

confined canyon segments and the South Fork valley segment 

confined by levees all have low migration rates compared to 

the unconfined valley segments (fig. 45). Channel slope is 

positively correlated to migration rates (fig. 46B), except for 

the steeper but closely confined Chiloquin Canyon segment, 

consistent with observations that stream power (which is 

directly proportional to slope) is correlated to bank erosion 

and channel migration (Nanson and Hickin, 1986; Richard and 

others, 2005).

Cutoff and Avulsion Processes

Cutoffs and avulsions counteract meander growth by 

isolating meander loops from the main channel. Cutoffs and 

channel avulsions typically reduce local sinuosity and increase 

local channel slope. They also leave a suite of backwater 

and side-channel environments, thereby providing important 

aquatic and riparian habitats. 

A cutoff is the breaching of a meander bend at or near its 

base. They typically form by one of two processes: (1) Neck 

cutoffs, which result from bank erosion, narrowing the 

neck until the channel breaches between the upstream and 

downstream meander limbs; and (2) Chute cutoffs, which 

result from new channels shortcutting between upstream and 

downstream meander bends, commonly without narrowing of 

the meander base (Thomas and Goudie, 2000) (figs. 40A, B). 

Prolonged meander growth inevitably leads to meander cutoff 

as the enlarging meanders intersect. Consequently, sinuosity 

commonly attains a stable level maintained dynamically by 

the concomitant processes of meander growth and cutoffs 

(Hooke, 2003). 

An avulsion refers to the sudden movement of the 

channel to a new location on the flood plain without 

substantially eroding or reforming the intervening flood-plain 

surface. Avulsions may result in anabranches that bypass 

several meander loops, forming new primary or secondary 

channels (fig. 40C). The new location may be a new channel 

incised into the flood plain or an older channel that is 

re-occupied. In some locations, chutes or neck cutoffs may 

involve secondary channels formed by avulsions (fig. 40A).

Avulsions and chute cutoffs require overbank flow. 

Lateral migration and resulting neck cutoffs may result 

from flows confined to the channel (Hooke, 1997). After a 

secondary channel forms, channel infilling and bar growth 

in the older channel may accelerate diversion of primary 

flow into the newly formed channel, transforming the older 

channel into low flood plain and backwater areas (fig. 12). In 

some cases, however, multiple channels may convey flow for 

several decades.

The main mechanism for meander abandonment in the 

Sprague River study area is chute cutoff, accounting for 42 of 

the 63 instances of observed meander abandonment for which 

the process could be determined (table 8). Only 12 avulsions 

were evident, but their effects are more significant than 

individual chute cutoffs because typically they result in 

abandonment of many meander loops. Only nine examples of 

neck cutoff were evident from the historical aerial photograph 

and map analysis. The relative rate of cutoff and avulsion 

processes is consistent with the overall geomorphic regime 

of frequent overbank flooding (which facilitates chute cutoffs 

and avulsions) and slow migration rates (which reduces the 

occurrence of neck cutoffs).

A process possibly promoting chute cutoffs in the 

Sprague River Basin is the formation of ice jams. Residents 

report that the Sprague River is subject to ice-flow jams that 

lead to backwater and overbank flow. Small incised channels 

on the flood-plain surface that drain from meander interiors to 

the main channel (fig. 58) may have been formed by overbank 

flow returning to the main channel during ice-jam floods. 

These may serve as pilot channels that initiate chute cutoffs, 

as has been observed for other rivers (Smith and Pearce, 2002; 

Prowse and Culp, 2003).

Chute cutoffs in the Sprague River Basin also may 

be promoted by channel and flood-plain modifications 

imposed by levees and railroad grades. This mechanism is 

evident in the Council Butte valley segment, where incipient 

chutes appear to be forming along levees (fig. 40B), where 

overbank flow depth (and erosive power) has been enhanced 

by confinement and where new channel formation may be 

taking advantage of areas of flood-plain excavation for levee 
Channel and Flood-Plain Conditions and Processes 79

tac14-0898_fig 58

FK 56.0

FK 56.6

FK 56.2

FK 56.4

FK 56.8

FK 55.8

FK 55.6

FK 55.4

FK 55.2

EXPLANATION

Flood-plain boundary

Year 2000 channel

Direction of flow

Flood-plain kilometer (FK)

0 150 300 METERS 75

0 500 1,000 FEET 250

Base map modified from Watershed

Sciences digital data, 1-meter resolution.

Projection: UTM 10N

Datum: North American Datum of 1983 (NAD 83)

N

Figure 58. Channels, possibly caused by ice jams, formed 

on Sprague River flood plain, Oregon. The narrow continuous 

channel spanning the meander bend eventually may enlarge, 

resulting in a meander cutoff.

construction. In general, flow confinement will increase the 

likelihood of cutoffs, as will ground-disturbing activities 

such as vehicle tracks or animal paths that disrupt flood-plain 

vegetative cover and thereby facilitate new channel formation.

Some avulsions may result from processes similar to 

those for chute cutoffs, but with the new channels bypassing 

many meander loops. In particular, the 12 avulsions since 

1940 appear to be of this type (fig. 40A). These avulsions 

generally are short, cutting off only two or three meander 

loops. Contrasting with these are the longer anabranches near 

the Sycan River confluence (fig. 40C). Long anabranches are 

typically associated with aggrading rivers, particularly those 

with high sediment loads (Slingerland and Smith, 2004). The 

long anabranches in the Council Butte near the Sycan River 

confluence have been stable since at least 1940 and partly 

may be relic features related to aggradation of the lower 

Sycan River and parts of the Sprague River after the Mazama 

eruption and the Sycan flood.

The 35 cutoffs and avulsions in the 1940–68 period 

exceed the 28 instances in the ensuing 37 years through 

2005. The significant overbank flow during the 1964 flood 

probably was a contributing factor to this period of significant 

channel change. The extensive levee building and diking in 

the 1940–1968 period may have accelerated or promoted 

cutoff formation.

At channel avulsions and meander cutoffs, the resulting 

abandoned channels typically become backwater or secondary 

channels, oxbow lakes, and wetland areas. These channels 

eventually fill with sediment and organic materials, depending 

on the nature of the connection with the primary channel. 

For isolated abandoned channels, the topographic channel 

form and resulting oxbow lakes or seasonally wet areas may 

persist for millennia before filling with overbank deposits. For 

connected abandoned channels, infilling may be much more 

rapid, as is the case for the 1940 channel at FK 48.2 (fig. 12).

Flood-Plain Building 

Together, all of these processes of channel movement 

and sediment erosion, deposition, and transport create the 

geomorphic flood plains of the study area with their diverse 

forms, including oxbows, scroll bars, overflow channels, 

and flood-plain surfaces of varied altitudes. In addition to 

providing sources of bedload and suspended sediment load for 

building downstream bars and flood-plain surfaces, channel 

migration provides new surfaces for flood-plain formation. 

In many areas of lateral migration, such surfaces typically 

begin as low-altitude bars formed of laterally and obliquely 

accreted bed material (fig. 15). In areas of more rapid channel 

migration and high bed-material supply, scroll bars may form 

in conjunction with lateral accretion. As the surfaces grow and 

become vegetated, vertical accretion becomes dominant. In 

most situations, rates of vertical growth gradually diminish as 

surfaces accumulate material and grow taller and as the active 

channel moves farther away. The highest flood-plain surfaces 

may accumulate sediment only during exceptional floods.

The pattern of flood-plain deposition can change if 

controlling factors vary. Most broadly, flood-plain deposition 

is affected by basin and climate factors that affect the 

frequency, magnitude, and duration of flooding. Channel 

migration, incision, and aggradation locally can change the 

frequency of overbank flooding and deposition. Local land 

use also can affect flood-plain deposition by changing the 

depth, velocity, and sediment concentration of overbank 

flows. A hint of such changes is provided by the stratigraphy 

of the geomorphic flood-plain, which in many cases shows 

coarser deposits near the top (figs. 8, 9), indicating higher 

velocity flows associated with overbank deposition. Plausible 

explanations for this given the current understanding 

of changing basin and flood-plain conditions include 

(1) confinement (and resulting acceleration) of flow by levees 

and embankments, and (2) decreased surface roughness (by 

smoothing and vegetation removal), which also increases local 

flow velocities.
80 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Geologic Controls and Legacy

As with many fluvial systems, geologic controls and past 

events strongly influence channel and flood plain processes 

in the Sprague River system. At the broad scale, the valley 

segments and their morphologies represent tectonics and 

volcanism of the last several million years. The widespread 

volcanic rocks and Tertiary lacustrine sediment in intervening 

basins result in relatively low quantities of sand-to-gravel size 

bed material available for fluvial transport, leading to a general 

condition of supply-limited fluvial systems flowing on or close 

to bedrock, even in the alluvial valleys of the study area. In 

places where channels flow directly on Tertiary lacustrine 

sediment, the potential for channel incision is limited. The 

North Fork, Upper Valley, and South Fork valley segments 

all appear to be within a basin of thicker alluvial fill than 

other valley segments, perhaps making these segments more 

susceptible to channel incision.

The valley bottoms in most valley segments are bounded 

partly by alluvial fans and terraces deposited during the 

Quaternary. Although these features locally confine the 

flood plain and form tall banks, they probably provide little 

sediment to the modern rivers.

The Mazama eruption of 7,700 cal yr BP probably has 

been the most important geologic event affecting modern 

flood-plain and channel conditions. Flood-plain stratigraphy 

and morphology, bar distribution, and the deposits of the 2006 

high flows all show the major role of pumiceous sand derived 

from that eruption in controlling channel migration and floodplain processes for the Sprague River and its major tributaries, 

mainly by enhancing bar deposition and channel movement. 

The historical condition of the South Fork Sprague River—

extensive wetlands flanking a poorly defined channel—

probably is similar to what much of the Sprague River was 

like before the eruption. Because the Sycan River was the 

most affected by the Mazama eruption, including the ensuing 

Sycan flood, this tributary responded most dynamically, with 

many episodes of flood-plain formation and erosion over the 

last several thousand years (Lind, 2009). Judging from the 

overall distribution of bars, the Sycan River, and, to a lesser 

extent, the North Fork Sprague River, continue to be major 

sources of bed material to the Sprague River fluvial system. 

The many anabranches in the Council Buttes valley segment 

downstream of the confluence of the Sprague River with 

the Sycan River (fig. 40C) also may represent bed-material 

deposition and resulting channel avulsions.

In the absence of additional disturbance or substantial 

change in basin conditions, the long-term trajectory of the 

Sprague River and its major tributaries would likely be 

reversion back to pre-Mazama characteristics as the supply 

of sandy bed material decreases. The active channel and bar 

environments may shift to low-energy wetland and low-floodplain fluvial systems. This long-term transition may not be 

gradual in either time or space, but depending on climate, 

hydrology, and sediment supply, may occur as back-and-forth 

transformations. The North Fork Sprague River apparently has 

alternated already between such conditions since the Mazama 

eruption, perhaps indicating future sequences on other parts of 

the fluvial system.

Human Influences

Overlaying geologic controls of flood-plain and channel 

processes and conditions is the locally strong influence of 

human manipulation. Alterations range from subtle, such as 

historical vegetation changes as discussed in more detail in the 

section, “Flood-Plain and Riparian Vegetation,” to substantial, 

such as channelization and confinement of the South Fork 

Sprague River. The types of human influences have changed 

over time, from flow diversion, beaver eradication, and log 

transport practices in the early 1900s, to levee construction 

and channelization in the mid-1900s, followed by more recent 

channel and flood-plain manipulation as part of restoration 

projects (NewFields River Basin Services and Kondolf, 2012). 

The various scales, intensities, and confounding effects of all 

these activities challenge direct attribution of specific human 

activities to specific consequences for the Sprague River 

study area, but general conclusions can be drawn from overall 

observed changes to flood-plain and channel conditions and 

known linkages among disturbance factors and channel and 

flood-plain processes.

Channel and Flood-Plain Manipulation

The most evident human manipulations with direct and 

continuing effects on channels and flood plains in the study 

area are channelization and flood-plain confinement. The 

South Fork valley segment in particular has been straightened 

and confined, directly causing the low sinuosity and high 

slope of this valley segment compared to other unconfined 

valley segments. Channelization was mostly prior to 1940 and 

perhaps mostly subsequent to 1925, given the May 18, 1925 

notes by USGS streamgager K.N. Phillips of a “very crooked” 

channel (USGS Oregon Water Science Center, Portland, 

Oregon, measurement station records for station 11495500). 

Confinement, channelization, and the consequent loss of 

sinuosity and increase in slope have almost certainly led to the 

transformation from a wet meadow fluvial system at the time 

of the GLO surveys to the locally straight and incised present 

channel. Incision likely began at the time of channelization 

but evidently has continued in the lower part of the South 

Fork valley segment through at least 1968. This incision 

likely contributed to local channel widening in this segment 

since the GLO surveys (fig. 41). The locus of present incision 

probably is upstream of Campbell Road Bridge (FK 101.5), 

given the greater suspended sediment concentrations in that 

reach (fig. 55) as well as the irregular channel profile (fig. 32). 

Diversion structures at FK 100.0 and 101.5 apparently 

have slowed incision for parts of the South Fork valley 

segment (fig. 32).
Channel and Flood-Plain Conditions and Processes 81

Although the South Fork Sprague River is the valley 

segment with most substantial channel realignment and 

confinement and most clear consequences, confinement has 

probably affected other unconfined valley segments in less 

obvious ways. In particular, the overall loss of sinuosity since 

1940 for most unconfined valley segments and decrease in 

channel migration rates are both consistent with the effects 

of confinement by roads, railroad grades, and levees. These 

effects are most evident for the Kamkaun Spring, Buttes of 

the Gods, and Council Buttes valley segments. Additionally, 

the flood-plain stratigraphy along the main-stem, South Fork, 

and North Fork Sprague Rivers shows coarsening toward the 

top, including sequences of post-1950 deposition as indicated 

by the presence of Cs137 (figs. 8, 9). This coarsening possibly 

represents higher-velocity overbank flow, possibly augmented 

by flood confinement. Similarly, the locally high incidence 

of avulsions and chute cutoffs in the 1940–68 period (fig. 59) 

may represent confinement creating deeper, faster, and more 

erosive overbank flow than during earlier times of unconfined 

flood-plain conditions.

Although not quantifiable from this analysis, levees, 

roads, ditches, and railroad embankments likely have 

substantially affected lateral connectivity (Poff and Ward, 

1990) within the Sprague River flood plain. Two factors 

contribute to this: (1) In the incised reaches (including the 

South Fork and possibly parts of the Upper Valley, Beatty 

Gap, and Council Butte segments), the frequency of floodplain inundation probably is reduced, although without 

detailed understanding of historical topographic conditions, 

documenting the magnitude of change is not possible. (2) The 

areal extent of seasonal flood inundation is reduced by levees 

and dikes, preventing sediment, water, and organic material 

transfers between flood plain and channel during floods. The 

thin but extensive overbank deposition during the 2006 high 

flows (fig. 52) as well as the young overbank deposits in the 

stratigraphic exposures of flood-plain deposits (fig. 8) confirms 

the importance of overbank flooding in flood-plain formation.

Dams and diversions have reduced longitudinal 

connectivity since the first diversion dams were constructed 

in the South Fork valley segment in the 1890s. The most 

significant such blockage was Chiloquin Dam at FK 1.3. 

Other small dams were constructed throughout the study area 

during the early and mid-1900s for log storage and transport, 

and water diversions. With the advent of pumping and the 

demise of the local timber industry, nearly all these structures 

have been removed. The only diversions presently affecting 

the channel profile are the 1-to-2-m-high structures diverting 

flow along the North Fork and South Fork Sprague Rivers 

(fig. 32). Although these structures affect low-flow conditions 

by diverting water from the channel into irrigation networks, 

the ecologic and geomorphic effects of these structures are 

uncertain except for their likely control on upstream migration 

of incision-related knickpoints.

Since the 1990s, efforts to restore channel and floodplain conditions have resulted in various channel alterations 

and realignments (NewFields River Basin Services and 

Kondolf, 2012). A primary objective has been to restore 

sinuosity by plugging meander cutoffs and avulsion channels 

and relocating the primary channel into historically occupied 

locations (fig. 23). Such efforts have focused on the Kamkaun 

Spring, Council Butte, and Beatty-Sycan valley segments, 

where meander cutoffs have been frequent over the last 

several decades (figs. 47, 59). When implemented and stable, 

these channel manipulations increase sinuosity and decrease 

local channel slope, but they typically include some form 

of bank hardening (commonly rock or anchored wood) that 

suppresses channel migration processes. Additionally, channel 

remeandering in itself typically does not address some of the 

local factors that may have contributed to increased rates of 

meander cutoffs, such as flood-plain confinement by levees 

and dikes.

0

2

4

6

8

Number of avulsions 

and cutoffs

About 1870–1940 

1940–1968 

1968–1975 

1975–2000 

2000–2005 

EXPLANATION

Time period

Incomplete aerial

 photograph coverage

Coyote 

Bucket

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

Figure 59. Avulsions and cutoffs, summarized by valley segment, Sprague River Basin, Oregon. General Land Office (about 

1870)-to-1940 avulsions only were determined for parts of Council Butte and Beatty–Sycan valley segments where the 

channel was meandered. Observations from South Fork, North Fork, Lower Sycan, and Coyote Bucket valley segments were 

limited for some periods by incomplete map and photographic coverage.
82 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Grazing Management

Livestock or wild ungulate grazing in riparian areas can 

lead to decreased streamside vegetation and bank trampling, 

both of which increase susceptibility to fluvial erosion. 

Overgrazing has been associated with channel widening, 

incision or aggradation depending on the particular stream 

characteristics, and loss or diminution of other processes 

related to aquatic habitat (Armour and others, 1991; Trimble 

and Mendel 1995; National Research Council, 2002). Grazing 

effects are evident at some locations along the Sprague and 

Sycan Rivers in the form of trampled banks and heavily 

browsed shrubs or grasses, although affected areas presently 

are limited in extent. Fencing and other methods to reduce 

livestock effects on the riparian zone have been adopted for 

some properties along the Sprague River. Effects of grazing 

on the channel banks and riparian zone likely were more 

extensive in the past, although no direct evidence is available 

for documenting changes in grazing intensity. Vegetation 

changes documented in the section, “Flood-Plain and Riparian 

Vegetation,” particularly a decrease in short woody shrubs 

between 1940 and 1968, are consistent with more intense 

grazing in the past.

Other Historical Activities

Besides the ongoing influences of channelization, 

diversions, levees, flood-plain confinement, and grazing 

practices, other historical activities also may contribute to 

present channel and flood-plain conditions in the study area. 

In particular, past timber practices and beaver eradication 

may have continuing effects on channel conditions, although 

the passage of several decades since these activities obscures 

evidence of their effects.

Timber harvest has likely decreased the volume of 

river-transported logs and large woody debris accumulations, 

especially in the confined valley segments where ponderosa 

pine colonizes the flood-plain and flanking surfaces. Although 

past and present wood flux is uncertain in the Sprague River 

system, it was (and is) likely small compared to forested 

flood plains. Nevertheless, in-channel wood provides a 

variety of channel structures and habitats (Gregory and 

others, 2003; Montgomery and others, 2003), and in supplylimited systems such as the Sprague River can promote 

deposition of bed material (Massong and Montgomery, 

2000). Decreased transport of large wood also possibly has 

affected flood-plain environments. Wood deposition on 

flood-plain surfaces can provide ecological functions—well 

documented for forested alluvial valleys (O’Connor and 

others, 2003c; Collins and others, 2012), but less understood 

in sparsely timbered environments such as the wide valley 

segments of the study area. Contrasting with a likely overall 

long-term decrease in large wood transport in the Sprague 

River fluvial system is the period of substantial fluvial wood 

transport during the first few decades of the 1900s, when the 

Sprague River was used for the storage and transport of saw 

logs (fig. 20). These operations resulted in substantial flow 

fluctuations (USGS Oregon Water Science Center, Portland, 

Oregon, measurement station records for station 11501000). 

Log transport during this time likely scoured banks of 

sediment and vegetation, possibly widening channels, but no 

quantitative measurements are available to document specific 

and persistent effects. Log drives and in-river storage probably 

diminished substantially after the 1928 completion of the 

OC&E railroad to Bly.

An even earlier activity, beaver eradication, also may 

have affected channel and flood-plain conditions in the study 

area. Several beaver lodges currently flank the channel in 

the study area, locally impounding flow in side channels 

and irrigation canals. However, beaver evidently were more 

common in the early 1900s in the Sprague River Basin, given 

A.W. Moore’s 1943 survey of 32 abandoned colony sites 

in the Chiloquin Canyon, Braymill, and Kamkaun Spring 

valley segments (unpub. wildlife resource report by A.W. 

Moore, 1943, U.S. Fish and Wildlife Service, in Klamath 

Indian Agency records, National Archives, written commun. 

from Larry Dunsmoor, The Klamath Tribe, 2006). Moore 

further concluded that “while the beaver population has been 

severely depleted, it is believed that where trapping of the 

animal stopped, a satisfactory population would build up in 

from seven to ten years.” Bailey (1936, p. 223) noted that 

“in 1914, L.J. Goldman reported them [beaver] on the west 

slope of the Yamsay Mountains, on the Sprague and Yamsay 

Rivers [upper Williamson], and in Klamath Marsh,” and that 

“in July 1927, there were still a few beavers in Sprague River 

and its branches north and east of Bly...” “[C]hannel in general 

very crooked, winding through beaver dam land...” noted 

USGS hydrologist K.N. Phillips in 1926 at the North Fork 

Sprague River measurement site, then located at Bailey Flat, 

a 2-km-long alluvial reach 3 km upstream of the upstream 

extent of the North Fork valley segment (USGS Oregon Water 

Science Center, Portland, Oregon, streamflow-gaging station 

records for station 11496500). As was the case throughout 

western North America (Jenkins and Busher, 1979), beaver 

populations were mostly eradicated by fur traders throughout 

Oregon by the mid-1850s (Bailey, 1936), although the timing 

of their demise in the Sprague River area is unknown.

The exact role of beaver on channel and flood-plain 

morphology in the Sprague River Basin also is uncertain. 

In many low-gradient montane basins of western North 

America, beaver can substantially affect channel morphology, 

in places creating extensive areas of wet meadows and 

promoting valley-bottom aggradation (Ives, 1942; Naiman 

and others, 1988; Kramer and others, 2012). In the Sprague 

River Basin, beaver dams likely played a role in the formation 

and maintenance of the historical wet meadow complexes 

historically occupying the South Fork valley segment as 

well as earlier episodes of wet meadows evident in the bank 

stratigraphy flanking the North Fork Sprague and Sycan 

Rivers (figs. 5, 9). Beaver-chewed stick fragments commonly 

were found within these exposures. Given these observations, 
Channel and Flood-Plain Conditions and Processes 83

local reductions in beaver population likely contributed to loss 

of wet-meadow environments in the South Fork Sprague and 

North Fork Sprague valley segments and possibly contributed 

to channel incision in the Upper Valley and Beatty Gap 

valley segments. 

Timber harvest and land use can affect flood-plain 

morphology indirectly by altering hydrologic regimes, which 

in turn affect channel and flood-plain processes. Timber 

harvest has increased peak streamflows at some locations 

in the Oregon Cascade Range (Jones and Grant, 1996, 

Beschta and others, 2000; Grant and others, 2008), and such 

changes to peak flows could have affected Sprague River 

stream channels, particularly between the 1920s and 1960s 

when harvest was most intense in the basin. However, the 

magnitudes of these changes are not known and their effects 

likely are to have been small compared to direct flood-plain 

and channel modifications. Low flows and total runoff were 

more likely affected than peak flows for the Sprague River 

study area, particularly by implementation of irrigation 

systems (U.S. Department of Agriculture, 2009). Some of the 

historical precipitation-runoff changes noted by Risley and 

Laenan (1999) may be a consequence of timber harvest and 

changing irrigation practices; such changes may affect riparian 

vegetation, but they probably have had little effect on physical 

channel and flood-plain processes.

Summary of Physical Flood-Plain and Channel 

Conditions, Processes, and Trends

Strong geologic controls have resulted in distinct valley 

segments within the alluvial portion of the Sprague River 

Basin, ranging from low-gradient reaches with expansive 

flood plains to steep and narrow canyon segments. The wide 

flood-plain valley segments are broadly similar; most contain a 

sinuous, low-gradient channel that migrates slowly across the 

valley bottom. The narrow valley segments include the steep, 

boulder-and-cobble-bed Chiloquin Canyon, at the downstream 

end of the study area, and the Coyote Bucket valley segment 

as the Sycan River leaves Sycan Canyon. The other confined 

valley segments—Braymill, S’Ocholis Canyon, and Beatty 

Gap—have similar gradients and substrates as adjacent 

unconfined valley segments, but much lower sinuosities. 

Although the geologic setting of the expansive South Fork 

valley segment resulted in historical conditions of sinuous and 

poorly defined channels and wet meadows, flanking levees 

now narrowly confine the channelized South Fork Sprague 

River for much of its length.

The fine-grained extrusive volcanic rocks and lacustrine 

sediment that constitute most of the Sprague River Basin 

produce little sand and gravel bed material. In the absence 

of substantial bed material prior to the Mazama eruption of 

7,700 cal yr BP, the main rivers of the study area apparently 

were flanked by wetlands and low flood plains, and migration 

rates probably were very low. The eruption, however, covered 

much of the northern basin with sand- and granule-size 

pumice clasts, transforming the fluvial system by increasing 

bed-material transport and promoting bar formation and 

channel migration, particularly for the Sycan River, North 

Fork Sprague River, and Sprague River downstream of its 

confluence with the Sycan River. The South Fork Sprague 

River, which had much less Mazama pumice deposited in its 

watershed, remained a low flood plain and wet meadow fluvial 

system until historical channelization and diking.

Despite the pumiceous sand input and the general 

low gradients of the main channels within the study area, 

the present overall bed-material sediment regime is supply 

limited, meaning the transport capacity exceeds the supply 

of bed material. This is evident by the discontinuous alluvial 

cover of the channel bottom, the sparse bars in and flanking 

the channel, and the overall slow channel migration rates 

for the Sprague River compared with many western North 

American rivers.

Despite slow channel migration rates, lateral channel 

movement is an important process for maintaining channel 

and flood-plain materials, form, and function. Movement is 

by continuous lateral migration associated with bar formation, 

lateral accretion, and bank erosion, as well as by translocations 

by avulsion and meander cutoffs. Lateral migration forms and 

expands meanders, increasing sinuosity. In unconfined valley 

segments, sinuosity values typically exceed 1.6 (fig. 60). The 

positive correlation between migration rates and bar area 

attests to the strong coupling between bed-material deposition 

and lateral channel movement.

Avulsions and meander cutoffs counter meander 

enlargement, including chute and neck cutoffs, which reduce 

sinuosity. Avulsions and chute cutoffs are much more common 

in the study area than neck cutoffs. Avulsions and chute 

cutoffs require overbank flow, whereas neck cutoffs do not. 

In some instances, ice jams may promote overbank flow 

and resulting cutoffs. The decrease in sinuosity since 1940 

for nearly all the unconfined valley segments (table 2) owes 

partly to decreased migration rates, but mostly to cutoffs 

and avulsions, mainly between 1940 and 1975 (fig. 60). The 

frequency of avulsions and meander cutoffs may have been 

enhanced historically by (1) flood-plain confinement by 

levees, dikes, roads, and railroads leading to deeper and faster 

overbank flow, thereby promoting erosion of new flood-plain 

channels; and (2) flood-plain disturbances such as trails, 

ditches, and vegetation manipulation or eradication, thereby 

locally concentrating overbank flow and more generally 

decreasing surface resistance to channel erosion.

For the most part, the Sprague River is not incised to the 

extent that floods fail to inundate the flood plain. The 2006 

flood left overbank deposits on flood-plain surfaces along the 

entirety of the main-stem Sprague, lower Sycan, and lower 

North Fork Sprague Rivers, consistent with the stratigraphic 

evidence of substantial flood-plain deposition and construction 

during the last several hundred years. The stratigraphy of 

exposed bank sections and along augering transects also 
84 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 60 Channel slope, in meters per meter

0.00001

0.0001

0.001

0.01

0.1

Sinuosity, in meters of channel 

per meter of flood plain

0.8

1.2

1.6

2.0

2.4

Median primary channel

width, in meters

0

10

20

30

40

Bar area, in square meters per

kilometer of channel

0

2,000

4,000

6,000

8,000

Median migration rate,

in meters per year

0

0.1

0.2

0.3

0.4

Frequency of avulsions

and cut-offs

0

2

4

6

8

Channel centerline altitude

change, in meters

-0.6

-0.4

-0.2

0

Coyote 

Bucket

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

About 1870

1940, 1870–1940

1968, 1940–1968

1975, 1968–1975

2000, 1975–2000

2005, 2000–2005

EXPLANATION

Incomplete aerial photograph coverage

Year, time period

Figure 60. Summary trends of major flood-plain and channel attributes, summarized by valley segment, Sprague 

River Basin, Oregon.
Channel and Flood-Plain Conditions and Processes 85

indicates little or no incision during the last 4,000 years within 

most of the study area, including the North Fork and Lower 

Sycan valley segments. As much as1.6 m of historical incision 

is evident in the upstream part of the study area, chiefly in the 

South Fork valley segment, but also possibly including parts 

of the Upper Valley and Beatty Gap valley segments. For the 

South Fork valley segment, incision (along with ditching and 

levee construction) has transformed areas of wet meadow at 

the time of the 1866 GLO surveys to rarely inundated flood 

plain. The locus of ongoing incision in the South Fork valley 

segment appears to be primarily upstream of FK 101.4.

The general absence of channel incision for much of 

the study area is consistent with little evidence of channel 

widening (fig. 60). Neither analyses using the GLO surveys 

(fig. 41) nor those of historical aerial photographs (fig. 43) 

substantiate overall widening or narrowing trends in channel 

width. Since the GLO surveys, wide channels have narrowed 

and narrow channels have widened. For measurements 

going back to the earliest aerial photographs of 1940, the 

channel generally was widest in the 1968 aerial photographs, 

probably representing channel widening during the high flow 

of December 1964. Between 1968 and 2000, most segments 

narrowed to widths very similar to those measured from 

the 1940 photographs. The Council Butte valley segment is 

unique in having a systematic narrowing trend for the entire 

time period. The variance in channel width has decreased 

since 1940 for several valley segments, particularly upstream 

of S’Ocholis Canyon (fig. 43).

All measurements, stratigraphic analyses, and other 

observations point to the important role of flooding in creating 

and maintaining channel and flood-plain conditions. Floods 

promote channel movement, including lateral migration and 

meander cutoffs, which together create a dynamic mosaic 

of channel and flood-plain landforms. Floods deposit water, 

sediment, and organic materials in the channel and overbank 

areas. Large floods, as in 1964, and moderate floods, as in 

2006, can have persistent effects including bank erosion, 

channel widening, bar building, and overbank flood-plain 

deposition, as well as creation of new channels from avulsions 

and cutoffs.

The Sycan River is unique because of the great influence 

of the 7,700 cal yr BP Mazama eruption on its catchment. 

The Sycan flood, shortly after the eruption, formed a 

surface underlain by loose and coarse pumiceous sand that 

now flanks the channel and younger flood plains. Where 

disturbed, this surface contributes substantial sand to the 

Sycan River. Subsequent to the flood, episodes of watershedscale, enhanced sediment supply resulted in construction 

of sandy flood plains flanking the channel, which continue 

to be susceptible to lateral erosion. This situation results in 

a Lower Sycan valley segment with abundant bars, wide 

channels, and high migration rates relative to other valley 

segments. Additionally, these local sediment sources make the 

Sycan River a major source of bed material for the Sprague 

River, as indicated by the high bar frequency and bar-area 

measurements in the Council Butte valley segment near the 

Sycan River confluence (fig. 60).

The Mazama eruption had much less effect on the South 

Fork Sprague River; consequently, the historical condition of 

its fluvial systems probably was much different from that of 

the Sycan River and, to a lesser extent, the North Fork Sprague 

River. At the time of the GLO surveys and for thousands of 

years earlier, the South Fork Sprague River probably was a 

poorly defined, stable (and locally multi‐thread) channel and 

wet-meadow complex fringed by willows. The expansive 

valley bottom likely was seasonally flooded and slowly 

aggrading, with peats and organic-rich marsh and low-energy 

fluvial deposits. Beavers likely had a strong role in controlling 

local flood-plain and channel conditions.

The South Fork valley segment has been the most 

transformed of all the valley segments since first historical 

observations. The present channel is incised, straightened, and 

separated from the flood plain by levees for much of the valley 

segment. Significant portions of the flood plain have been 

drained and leveled. In-channel structures currently divert flow 

into irrigation ditch networks. The South Fork valley segment 

also appears to be a major source of suspended sediment to the 

Sprague River fluvial system.

Since first European settlement in the 1860s, human 

actions locally have affected Sprague River channel and 

flood‐plain conditions. Early activities such as beaver 

trapping and timber harvest (and associated activities) almost 

certainly had consequences for channels and flood plains, 

although their persistent effects are unknown. Similarly, the 

consequences of late-19th- and early-20th-century diversions, 

dams, timber harvest, and saw-log transport are unclear. More 

evident are the contemporaneous and persistent effects of 

channelization and flood-plain confinement by levees, roads, 

and the former OC&E railroad alignment, mainly dating from 

the 1920s through the 1970s. Channelization before 1940 in 

particular has directly transformed the South Fork Sprague 

River between FKs 97.0 and 101.0. Less evident are the 

effects of levees, but flood-plain confinement probably has 

increased the frequency of avulsions and cutoffs, resulting 

in reduced sinuosity and overall greater channel slopes since 

1940. Riparian grazing and channel and bank trampling by 

cattle locally have affected bank and channel conditions, as 

have local accumulations of dumped rock at fords and former 

bridge crossings. Channel restoration and remeandering, 

chiefly since 2000, locally has resulted in the filling of chute 

cutoffs, avulsions, and the placement of the primary channel 

back in its historical positions. These restoration efforts, 

however, commonly are engineered with anchored materials to 

decrease future channel migration.
86 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Despite these broadscale and local effects of human 

disturbances, many of the fundamental processes that have 

shaped the Sprague River fluvial systems over the last 

several thousand years are still present to varying degrees. 

Most importantly, the overall bed-material transport regime 

(including sediment supply and water flow, which drives 

processes of bar building and channel migration), has not been 

affected substantially by upstream impoundments interrupting 

either flow or sediment. The absence of system-wide 

channel incision also is important; incision fundamentally 

alters channel and flood-plain processes (particularly lateral 

exchanges of water, sediment, and organic materials), and 

can limit restoration opportunities (Simon, 1989; Simon and 

Rinaldi, 2006; Cluer and Thorne, 2013). Incised areas of the 

fluvial system, particularly the South Fork valley segment, are 

in the upstream part of the study area, limiting the likelihood 

that geomorphic effects (aside from changes in flow and 

sediment transport) will migrate to other parts of the study 

area, since channel incision typically migrates upstream. 

These factors suggest that restoration of many of the historical 

physical conditions and processes is possible for much of 

the Sprague River study area without substantial physical 

manipulation of current conditions.

Flood-Plain and Riparian Vegetation

Vegetation interacts strongly with channels and flood 

plains. Patterns of vegetation within basins are controlled by 

geomorphic character and prevailing land uses, commonly 

varying locally and with time. Vegetation, in turn, can 

affect processes and rates of fluvial erosion and deposition. 

Flood-plain vegetation in western, semi-arid basins such as 

the Sprague River Basin chiefly owes to substrate conditions, 

moisture availability, and disturbances such as flooding 

(Bornette and Amoros, 1996; Hupp and Osterkamp, 1996; 

Bendix, 1997; Castelli and others, 2000; Amlin and Rood, 

2002; Chapin and others, 2002; Li and others, 2006; Bornette 

and others, 2008).

Processes controlling flood-plain vegetation differ 

spatially relative to the channel. Fluvial processes 

of inundation, scour, and burial disturb near-channel 

environments more frequently than distal ones (Hupp and 

Osterkamp, 1996; Cordes and others, 1997), but also provide 

more opportunities for establishment of typical riparian 

species (Karrenberg and others, 2002; Gurnell and others, 

2008). These natural processes involving vegetation can be 

altered substantially by land use. In the Sprague River Basin, 

such alterations include drainage, diking, and cultivation of 

expansive flood-plain areas; livestock grazing; local timber 

harvest in some valley segments; and extensive willow 

and riparian shrub removal as part of mid-20th-century 

channelization and flood mitigation efforts.

The analysis of flood-plain vegetation parallels the analysis 

for physical channel and flood-plain conditions by relying 

on historical observations and systematic mapping from the 

1940, 1968, and 2000 aerial photographs. These analyses are 

combined with available general understanding of riparian 

vegetation processes to infer mechanisms for evident trends 

and transitions in vegetation conditions since the first historical 

observations. Specifically evaluated are (1) the relations among 

general vegetation patterns and flood-plain geomorphology, 

(2) temporal variations in these patterns, and (3) the relation 

of these temporal and spatial patterns of vegetation conditions 

to geomorphic processes and land-use history. The analysis is 

broadscale, with limited evaluation of individual species. More 

information on the factors controlling distribution of vegetation 

types in the Sprague River Basin is provided by Rasmussen 

(2011).

Overview of Current Flood-Plain Vegetation

Vegetation conditions generally are controlled by the 

characteristics of the valley segments (table 2), indicating the 

important influence of channel gradient, sediment supply, floodplain width, and major tributaries. Narrow valleys generally 

have higher-energy streamflow and coarser channel and floodplain sediments than wide valley flood plains. Narrow valleys 

also have higher banks and more topographic shading than wide 

valley flood plains. Wide valleys have space for development of 

channel meanders and more flood-plain wetlands than narrow 

valleys. Spring complexes in the flood plain and adjacent 

surfaces are flanked by riparian and wetland vegetation. 

Additionally, distinct differences in typical land use among 

the valley segments lead to important differences in resulting 

vegetation conditions.

The very narrow Chiloquin Canyon, Braymill, and Coyote 

Bucket valley segments are vegetated largely with woody 

species, including willow and ponderosa pine. Small patches 

of quaking aspen are present locally, and, in the Chiloquin and 

Braymill segments, there are a few individual cottonwood. 

The slightly wider S’Ocholis Canyon and Beatty Gap valley 

segments have a mix of shrubs, herbaceous species, and some 

trees, with small patches of aspen in both segments. Vegetation 

in wide flood-plain segments mostly is herbaceous, but willows 

locally flank present and former channel edges. Generally, tall 

banks in confined valley segments commonly support dense 

shrub communities, whereas low stream banks with saturated 

soils, common in unconfined valley segments typically do not 

(Rasmussen, 2011). Although the geomorphic flood plain of the 

Lower Sycan valley segment is relatively narrow, it is flanked 

by the broad, dry, and rarely inundated Sycan flood deposits 

that are vegetated by upland grasses and shrubs. The invasive 

species, reed canarygrass, is present throughout the study area 

in near-channel areas of both wide and narrow valley segments, 

but is particularly common in the Chiloquin Canyon and 

Braymill valley segments.
Flood-Plain and Riparian Vegetation 87

Historical Flood-Plain Vegetation Conditions

Understanding historical vegetation conditions provides 

a basis for evaluating the relation of flood-plain vegetation 

to channel and flood-plain processes, as well as a means 

for evaluating changes since 1940 resulting from land-use 

conditions and changing process regimes. The main sources 

documenting early vegetation conditions in the study area 

are the maps and records of the GLO surveys and records of 

botanists travelling through the region.

Vegetation Conditions Inferred from 

GLO Surveys and Notes

As with channel conditions, the GLO surveys can provide 

some quantitative information on vegetation conditions. These 

surveys, conducted between 1866 and 1892 (table 3), include 

(1) plat maps showing generalized cover, with notations such 

as “forest,” “bottomland,” and “marshes;” (2) section line 

notes describing landscape conditions along surveyed section 

lines; and (3) “witness tree” descriptions documenting trees 

near surveyed section corners.

Observations recorded on the plat maps (table 9) indicate 

that the wide valley segments had sparse tree cover. By 

contrast, the narrow Chiloquin Canyon and Braymill valley 

segments were described as forested, and the S’Ocholis 

Canyon and Beatty Gap valley segments were a mix of 

herbaceous and timber cover types.

The GLO section-line notes documented general 

conditions along surveyed lines. Surveyors often noted 

transitions between forest and prairie with statements such 

as “leaving river bottom” or “entering timber.” Survey 

descriptions emphasized timber and grasslands (or prairies), 

in accordance with resources attractive to homesteaders. No 

section-line surveys specifically describe riparian vegetation, 

except for the Beatty Gap and Upper Valley segments, where 

large willows served as witness trees (table 9). Surveyors did 

not note aspen stands in Beatty Gap, S’Ocholis Canyon, or 

other narrow valley segments, although some aspen patches 

exist currently and were present in the 1940s.

Section corners and the midpoints of section lines 

were marked with charred posts, pits, or rock piles. Marker 

locations were related to as many as three nearby “witness 

trees.” The surveyor recorded the species and diameter of each 

witness tree, and its direction and distance from the marker. 

An absence of witness trees indicates a lack of nearby trees, 

thereby indicating non-forest cover (table 9). Smaller shrubs 

or willows likely were present, but are not mentioned. Pine 

trees were recorded on flood-plain surfaces only in Kamkaun 

Spring, S’Ocholis Canyon, and the Lower Sycan valley 

segments. Notes mention a single aspen witness tree in the 

Braymill valley segment. These conditions are consistent 

with the very general land classification of Leiberg (1903) 

encompassing most of the study area west of FK 91.8.

The broad vegetation characteristics noted during the 

GLO surveys currently persist: few trees in the unconfined 

valley segments, but more forested conditions, including pine 

and willow, in the narrower valley segments. The wide valley 

segments were most commonly described as “prairie” although 

swampy soils and wetland vegetation were noted for the South 

Fork valley segment.

Historical Notes from Botanist William E. Lawrence 

Historical observations from the late 1800s (Gatschet, 1890; 

Leiberg, 1903) are consistent with the inferences of general 

vegetation conditions noted in the GLO surveys. Slightly later 

but more specific information is provided by Oregon State 

University (then College) botanist William E. Lawrence, who 

travelled from Klamath Falls to Lakeview, Oregon, in 1922 and 

1934, both times describing vegetation in his field notebooks 

(W.E. Lawrence, Oregon State University Herbarium, Corvallis, 

Oregon, unpublished field journals). In each instance, his route 

provided views of the Beatty-Sycan, Beatty Gap, and South Fork 

Sprague valley segments as he closely followed the present route 

of Oregon State Highway 140 eastward. Observations by W.E. 

Lawrence include the following:

July 1, 1922

No trees are to be found in the Beattie flat. The kind of 

sage was not noted.

Ribes aureum [golden currant] grew very luxuriantly 

along the creek in Beattie valley. Salix [willow] was 

very abundant along the stream...

Salix, Ribes aureum, Amelanchier [serviceberry], 

Prunus demissa [chokecherry], Populus [most likely 

aspen, unlikely cottonwood], Urtica [nettle], Rosa sp. 

[wild rose] were seen abundantly along the Sprague 

River.

In brief it was Populus, etc. and Ribes aureum along 

the river. Kunzia tridentate [bitterbrush; Purshia 

tridentata] then Artemesia tridentat[a] [sagebrush] and 

a little Ribes cereum [wax currant] with yellow pine 

[ponderosa pine] farther up.

Hay farming characterizes the productive areas here.

July 3, 1922

The currants grow in quantity along the creek bottoms. 

This is Ribes aureum. It is along the Sprague River 

in quantity. It extends from above Bly at Sec. 10T 

37R 16 [upstream of the study area] down the river in 

abundance for 8 miles. It grows here in thick bodies. 

Below here it extends scattering with the willows down 

into the Reservation [west of the North Fork and South 

Fork Sprague Rivers confluence].
88 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Table 9. Vegetation notes from General Land Office surveys, by valley segment, Sprague River Basin, Oregon.

[No records obtained for Chiloquin Canyon, Braymill, and Coyote Bucket valley segments. Abbreviations: GLO, General Land Office; T, Township; S, South; 

R, Range; E, East; cm, centimeter; –, no data available]

Valley

segment

Observations recorded 

on plat maps

Flood plain notes from 

section line survey

Flood plain witness trees, as 

recorded in GLO notes Comments

Kamkaun Spring Lower Kamkaun drawn as 

non-forested in valley bottom, 

timber on uplands. T34S R8E

13 section boundary lines

surveyed; two noted as

“Prairie”; others no

description.

12 monumented corners, 

2 with pine witness trees, 

10 with no witness trees.

Mix of timber and prairie on

both uplands and flood plain.

Open river bottom interpreted

as prairie. 

S’Ocholis Canyon – 11 section boundary lines

surveyed; one noted as

“Prairie”; others no

description.

5 monumented corners, 

3 with pine witness trees, 

2 with no witness trees.

The one mention of prairie was

near the boundary with Buttes

of the Gods segment.

Buttes of the 

Gods

– 6 section boundary lines

surveyed; 1 noted as

“Prairie”; 5 as “No 

timber.”

15 monumented corners, 

none with witness trees.

–

Council Butte Described as ‘level prairie’ 

on northern one-third of plat

map of T35S R10E.

9 section boundary lines

surveyed, 1 noted as

“Prairie,” 7 as “No timber,”

and 1 as “Prairie and no

timber.”

22 monumented corners, 

none with witness trees.

Many mentions of “land

level,” but not vegetation type

on flood plain surface. 

Beatty-Sycan – 4 section boundary lines

surveyed, 2 noted as 

“No timber.”

5 monumented corners, 

none with witness trees.

–

Beatty Gap – 8 section boundary lines

surveyed, 4 noted as 

“No timber.”

5 monumented corners, 

1 with willow witness tree, 

4 with no witness trees.

2 willows used as witness

trees, 7.5 and 20 cm

diameters.

Upper Valley – 4 section boundary lines

surveyed, 1 noted as 

“No timber.”

5 monumented corners, 

1 with willow witness tree, 

4 with no witness trees.

2 willows used as witness

trees, both 10 cm diameter.

South Fork Area of wetland vegetation 

drawn on plat map. No 

timber on western end 

of segment. T36S R14E.

11 section boundary lines

surveyed, 4 noted as 

“No timber.”

26 monumented corners, 

none with witness trees.

Swampy soil mentioned on

two section lines.

North Fork – 9 section boundary lines

surveyed, 3 noted as 

“No timber.”

5 monumented corners, 

none with witness trees.

–

Lower Sycan – 8 section boundary lines

surveyed, 3 noted as

“Prairie.”

4 monumented corners, 

2 with pine witness trees, 

2 with no witness trees.

–
Flood-Plain and Riparian Vegetation 89

July 30, 1934

Sprague River junction [near Beatty]. There is an 

extensive natural meadow flat here which extends 

along the river bordered with Salix.

From here [probably in the Upper Valley segment] 

the Sprague River is seen to the left (north) with 

natural meadow pasture on bottom and bordered by 

willows. This widens out to the Bly area.

Bly...has certainly grown since 1922 when last I 

passed through. The saw mill has evidently brought 

about the change.

From these observations, it appears that at the time 

of Lawrence’s travels, much of the Sprague River corridor 

upstream of Beatty had a distinct riparian vegetation 

community, including locally thick growths of shrubby 

species, including willow, interspersed with grass meadows. 

Higher surfaces were vegetated with typical semi-arid shrubby 

species such as sagebrush and bitterbrush. However, consistent 

with the diking and diversions already in place, “productive 

areas” were cultivated for hay.

Aerial Photograph Analysis

An analysis of the vertical aerial photographs dating 

from 1940, 1968, and 2000 (table 4) provides a quantitative 

assessment of vegetation conditions for the period 1940–2000. 

This analysis was based on vegetation mapping in conjunction 

with the mapping of channel and cultural features (table 5). 

The mapping and analyses were conducted at two spatial 

scales: (1) at the broad scale of the entire flood plain; and 

(2) closer to the channel within a 40-m-wide swath centered 

about the primary channel centerline, referred to as “the 

near‐channel area.”

Vegetation Mapping and Analysis

The mapped vegetation classes are (1) water (2) bare, 

(3) herbaceous, (4) short woody, and (5) tall woody (table 10). 

The woody classes approximately match National Wetland 

Inventory protocols that divide Forested and Scrub-Shrub 

wetland types at the 6-m threshold (Cowardin and others, 

1979). As in the National Wetland Inventory method, trees 

less than 6-m-high are classified as “short woody.” Mapping 

was done for the entire geomorphic flood plain for each of 

the three sets of aerial photography, with all areas of the flood 

plain classified into one of the five vegetation classes for 

each set.

As for the channel and flood-plain geomorphic 

characteristics, the different sets of aerial photography 

introduced some challenges for consistent vegetation mapping. 

The 1940s set was made at different times over the summers 

of 2 years and covered a smaller area than in 1968 and 2000 

(table 4). All photographic sets used were black and white, 

although a high-resolution, true-color set from 2005 enabled 

the checking of type and position of vegetation stands. 

Vegetation types also were field verified in several places. 

The North Fork and South Fork valley segments had little 

coverage in the 1940s photographic set; consequently, results 

from these valley segments only are used for some analyses. 

Because of limited aerial photograph coverage, the Coyote 

Bucket segment of the Sycan River was not included in any 

vegetation analyses.

Mapping involved delineating patches of vegetation 

classes (except for herbaceous), typically at scales ranging 

from 1:1,000 to 1:2,000. The minimum patch size was 20 m2, 

or for the short woody and tall woody classes, areas that 

included five or more individual trees separated by less than 

20 m. Individual trees were not mapped.

Tall and short woody vegetation was mapped primarily 

on the basis of structure rather than tree species; however, 

many tall woody species were recognizable from the imagery. 

In particular, pines were very dark on the photos, sometimes 

nearly indistinguishable from the accompanying shadows. 

Quaking aspen had round crowns for individual trees; larger 

stands had a mottled texture, and tone typically was darker 

than that of the shorter and patchier willow and lighter than 

that of the adjacent pine. Parts of the 1968 photographic set 

were taken prior to leaf-out for the aspen trees, making crown 

identification locally difficult, although crown shadows were 

distinctive, even without leaves, making mapping possible in 

most cases. Short woody vegetation primarily was composed 

of young trees of the tall woody species, as well as willow and 

other shrubs typically found along channels.

After all woody vegetation was mapped, areas without 

any vegetation were delineated and classified as bare. Houses, 

roads, and bridges were classified as bare. Consistent with 

field conditions, all surfaces not mapped as water (from the 

physical flood-plain mapping), tall woody, short woody, 

or bare were assumed to be covered with herbaceous 

vegetation. This mapping process resulted in all areas within 

the geomorphic flood-plain boundary being assigned one 

(and only one) of five cover-type classifications: water, bare, 

herbaceous, short woody, or tall woody.

Table 10. Mapped cover types. 

[From Cowardin and others,1979]

Cover type Characteristic

Water Surface water

Bare Exposed soil, roads, and buildings with no vegetation

Herbaceous Grasses, sedges, rushes, non-woody vegetation

Short woody Woody stands less than 6 meters tall

Tall woody Woody stands greater than 6 meters tall
90 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Spatial Distribution of Vegetation in Year 2000

The vegetation patterns mapped from the year 2000 aerial 

photographs (table 11; fig. 61) allow for the examination of 

the relation between recent vegetation patterns and flood-plain 

width, and the differences in vegetation patterns between 

flood-plain and near-channel zones. Other potential controlling 

factors such as stream or valley gradient, soil type, or 

flood‐plain altitude, were not evaluated.

As expected, water (including all channels and backwater 

areas) covers a much greater percentage of the narrow flood 

plains than the wide flood plains, accounting for as much as 

40 percent for the confined valley segments, such as Chiloquin 

Canyon, but less than 20 percent for most of the unconfined 

valley segments, such as Kamkaun Spring (tables 2, 11).

The confined valley segments have a much higher 

proportion of woody vegetation than the unconfined valley 

segments (table 11). Chiloquin Canyon, Braymill, S’Ocholis 

Canyon, and Beatty Gap all have more than 25 percent of their 

flood-plain areas covered by woody vegetation, compared 

to less than 10 percent for the unconfined valley segments. 

The unconfined Council Butte valley segment has woody 

vegetation covering less than 0.1 percent of the flood-plain 

area. The Lower Sycan valley segment, although narrow with 

a mean flood-plain width of 220 m, has only 7 percent woody 

cover compared to the 32 percent woody cover for the slightly 

narrower Beatty Gap. Some of this difference results from the 

greater solar exposure (and probably drier conditions) of the 

Lower Sycan valley segment, which is oriented north-south 

and flanked by low terraces composed of coarse sandy soils, 

whereas the other narrow segments are within deeper and 

more shaded canyons. Part of the difference also probably 

owes to the substantial decline of woody cover in the Lower 

Sycan valley segment, which had 23 percent woody cover in 

the 1940 aerial photographs.

For all valley segments, most of the woody cover is short 

woody vegetation. Tall woody vegetation constitutes more 

than 15 percent of the cover only in the narrowly confined 

Chiloquin Canyon and Braymill valley segments. In all other 

segments, short woody vegetation cover exceeds tall woody 

vegetation by a factor of two or more (fig. 61, table 11). 

The Buttes of the God, Beatty-Sycan, and Upper Valley 

segments had no mappable tall woody vegetation in 2000. The 

expansive Council Butte valley segment had less than 0.5 ha 

of tall woody vegetation, mostly planted trees adjacent to 

homesteads.

Herbaceous cover dominates the flood plains of the 

wide and unconfined valley segments, which all have more 

than 75 percent herbaceous cover (over 90 percent in the 

Upper Valley and South Fork valley segments). Herbaceous 

vegetation covers more than 50 percent of the flood plain for 

all valley segments in the study area except for the confined 

Chiloquin Canyon and Braymill valley segments.

Near-channel areas within 20 m of the channel centerline 

had vegetation patterns in 2000 similar to the corresponding 

flood-plain patterns, but with some consistent differences 

(table 12; fig. 62): (1) bare ground is a larger component of 

surface cover in the near-channel zone than for the flood plain, 

mostly active bar surfaces and bare banks along the channel; 

(2) tall woody vegetation is less prevalent in the near-channel 

zone than on general flood-plain surfaces, likely owing to 

the intolerance of aspen and ponderosa pine to the greater 

frequency and extent of soil saturation near the channel, 

and (3) short woody vegetation occupies a slightly greater 

percentage of the near-channel zone than of the whole flood 

plain in most valley segments.

The slightly greater abundance of short woody shrubs 

(typically willow) in the near-channel area may represent 

higher availability of seeds and germination sites, as is the 

case for riparian areas in many semi-arid regions (Karrenberg 

and others, 2002). The greater percentage of short woody 

vegetation in the near-channel areas (compared to the overall 

flood plain) is most pronounced in the narrow confined valley 

segments (Chiloquin Canyon, Braymill, S’Ocholis Canyon, 

and Beatty Gap). This may be the result of the slightly higher 

flood plains (fig. 17) or lower migration rates (fig. 44) in these 

valley segments.

Vegetation Trends, 1940–2000

Trends in vegetation patterns are evident from the 

vegetation mapping based on the 1940, 1968, and 2000 aerial 

photographs (tables 11, 12; figs. 61, 62). For the geomorphic 

flood plain, study-area totals from 1940 to 2000 (excluding the 

North Fork, South Fork, and Coyote Bucket valley segments 

for which aerial photograph coverage is incomplete) show a 

gain of herbaceous cover (increasing from 78.2 to 81.5 percent 

of the analysis area) and loss of short woody cover (decreasing 

from 7.7 to 4.8 percent of the study area) (table 11). Other 

changes were less than 1 percent, including slight gains in 

tall woody vegetation and bare areas and a loss of watercovered area. Although the area is small with respect to the 

total flood‐plain area, the decrease in short woody vegetation 

between 1940 and 2000 represents a loss of 38 percent of its 

1940 area and is by far the largest relative change in any of the 

mapped cover types.

Most of the change in total flood-plain cover of short 

woody vegetation was during the 1940–1968 period, when 

138 ha were lost along the main-stem Sprague River and 

Lower Sycan valley segment (table 11). Subsequently, 

between 1968 and 2000, short woody vegetation cover 

decreased by an additional 6.6 ha. By contrast, herbaceous 

cover gained more area between 1968 and 2000, when its 

extent increased by 129 ha compared to an increase of only 

36.6 ha during 1940–1968. Tall woody vegetation cover 

increased by small areas during each analysis period. The 

areas covered by water and bare ground each increased 

between 1940 and 1968, and then decreased between 1968 and 

2000. The total net loss of water-covered area between 1940 

and 2000 was 48 ha.
Flood-Plain and Riparian Vegetation 91

Table 11. Cover types in valley segments of the geomorphic flood plain, Sprague Valley Basin, Oregon.

[Cover type classes modified from Cowardin and others (1979). Partial aerial photograph coverage for the South Fork and North Fork segments 

in 1940. Totals may not sum due to rounding. Abbreviation: ha, hectare]

Valley segment

cover type

Chiloquin 

Canyon Braymill KamkaunSpring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council

Butte

1940 Area (ha)

Water 47.7 21.6 98.0 54.9 103.4 200.4

Bare 2.4 0.3 5.8 2.8 13.6 7.9

Herbaceous 33.4 13.1 631.0 141.2 802.2 1,374.9

Short woody 18.6 17.8 80.5 65.1 9.1 12.2

Tall woody 10.6 8.7 2.0 13.5 0.0 0.6

1968 Area (ha)

Water 49.1 22.3 116.4 64.5 108.0 178.0

Bare 1.4 1.4 14.0 8.5 16.5 39.0

Herbaceous 33.7 12.8 622.4 140.0 799.5 1,375.9

Short woody 13.0 14.0 61.7 49.1 4.2 3.0

Tall woody 15.6 11.0 2.8 15.3 0.0 0.0

2000 Area (ha)

Water 46.5 22.6 111.9 50.6 91.5 156.6

Bare 0.8 0.4 12.9 4.3 7.5 14.5

Herbaceous 32.8 12.8 634.3 150.2 824.6 1,423.8

Short woody 16.0 14.4 55.7 50.0 4.6 1.1

Tall woody 16.7 11.4 2.5 22.4 0.0 0.0

Total analysis area 112.8 61.5 817.3 277.5 928.2 1,595.9

Valley segment

cover type

BeattySycanBeatty 

Gap

Upper

 Valley

South

Fork1

North

Fork2

Lower

Sycan

1940 Area (ha)

Water 41.2 22.7 10.7 4.6 11.1 27.8

Bare 4.1 2.7 1.2 0.8 2.5 4.0

Herbaceous 345.1 109.3 386.6 253.8 246.5 151.4

Short woody 14.7 69.4 48.9 0.4 31.7 53.8

Tall woody 0.0 9.8 0.0 0.0 0.0 1.2

1968 Area (ha)

Water 42.8 32.3 12.6 28.1 22.6 33.4

Bare 7.1 6.5 3.4 15.3 28.1 12.3

Herbaceous 344.0 114.8 414.0 2,122.4 451.7 167.7

Short woody 11.1 54.7 17.3 7.7 21.4 24.4

Tall woody 0.0 5.6 0.0 0.4 0.3 0.4

2000 Area (ha)

Water 34.1 25.2 11.9 23.2 20.7 29.5

Bare 5.1 3.3 1.5 9.4 5.3 7.6

Herbaceous 354.0 116.2 421.7 2,138.9 489.2 183.6

Short woody 11.9 63.0 12.1 1.9 8.5 17.1

Tall woody 0.0 6.1 0.0 0.5 0.5 0.5

Total analysis area 405.1 213.9 447.3 2,173.8 524.1 238.2

1

1940 coverage of South Fork totals 259.6 ha.

2

1940 area only 291.8 ha.
92 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 61

A. Water

0

60

120

180

240

B. Bare

0

10

20

30

40

C. Herbaceous

Area, in hectares

0

600

1,200

1,800

2,400

D. Short woody

0

30

60

90

120

E. Tall woody

0

6

12

18

24

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

1940

1968

2000

Year

EXPLANATION

Incomplete aerial

photograph coverage

Figure 61. Extent of mapped cover types in the geomorphic flood plain, summarized by valley segment, 

Sprague Valley Basin, Oregon.
Flood-Plain and Riparian Vegetation 93

Table 12. Cover types in valley segments of the near-channel area, Sprague Valley Basin, Oregon.

[Cover type classes are modified from Cowardin and others (1979). Partial aerial photograph coverage for the South Fork and North Fork 

segments in 1940. Totals may not sum due to rounding. Abbreviation: ha, hectare]

Valley segment

cover type

Chiloquin 

Canyon Braymill KamkaunSpring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council

Butte

1940 Area (ha)

Water 47.7 21.6 80.1 51.8 82.0 149.0

Bare 1.4 0.0 1.5 1.3 3.0 5.5

Herbaceous 12.5 4.3 68.9 26.6 75.6 119.0

Short woody 12.3 12.1 30.7 26.9 4.2 5.4

Tall woody 2.7 1.9 0.1 4.9 0.0 0.0

1968 Area (ha)

Water 49.1 22.1 84.6 56.3 81.5 130.9

Bare 1.1 0.3 6.1 5.0 9.1 18.2

Herbaceous 13.8 4.8 73.1 29.7 68.7 107.0

Short woody 9.4 10.3 16.0 20.8 0.8 0.3

Tall woody 4.0 2.7 0.5 4.9 0.0 0.0

2000 Area (ha)

Water 46.3 22.5 83.2 48.3 70.4 114.1

Bare 0.4 0.1 5.9 2.4 4.8 5.8

Herbaceous 13.6 5.3 75.0 31.5 71.8 115.0

Short woody 11.9 10.1 10.8 21.0 0.3 0.2

Tall woody 4.0 2.5 0.6 4.9 0.0 0.0

Total analysis area 76.7 40.0 181.4 111.5 164.7 278.9

Valley segment

cover type

BeattySycanBeatty 

Gap

Upper

 Valley

South

Fork1

North

Fork2

Lower

Sycan

1940 Area (ha)

Water 32.0 20.4 7.8 4.0 8.9 26.5

Bare 1.3 1.5 0.9 0.0 0.7 3.1

Herbaceous 31.6 19.5 17.0 9.6 18.4 24.5

Short woody 7.0 23.9 10.4 0.2 12.7 20.6

Tall woody 0.0 3.0 0.0 0.0 0.0 0.7

1968 Area (ha)

Water 27.3 23.8 11.3 21.0 14.6 26.3

Bare 2.4 4.3 2.0 5.8 8.9 9.9

Herbaceous 27.4 22.9 20.8 54.0 34.8 32.4

Short woody 3.3 16.1 3.2 1.0 9.0 6.7

Tall woody 0.0 2.0 0.0 0.0 0.1 0.0

2000 Area (ha)

Water 26.0 21.0 10.1 15.7 14.1 23.4

Bare 2.0 1.9 1.1 1.8 2.8 6.0

Herbaceous 29.2 25.7 22.9 58.7 48.6 39.3

Short woody 3.2 14.7 2.0 0.2 2.9 3.9

Tall woody 0.0 1.6 0.0 0.0 0.0 0.2

Total analysis area 71.9 68.2 36.1 82.2 67.3 75.4

1

1940 coverage of South Fork totals 259.6 ha.

2

1940 area only 291.8 ha.
94 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 62

* *

* *

* *

*

*

* *

A. Water

0

40

80

120

160

B. Bare

0

5

10

15

20

C. Herbaceous

Area, in hectares

0

1.5

3

4.5

6

D. Short woody

0

10

20

30

40

E. Tall woody

0

20

40

60

80

100

120

140

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

1940

1968

2000

Year

EXPLANATION

Incomplete aerial

photograph coverage

Figure 62. Extent of mapped cover types in the near-channel area, summarized by valley segment, 

Sprague Valley Basin, Oregon.
Flood-Plain and Riparian Vegetation 95

Most large changes in cover type were widespread 

(table 11, fig. 61). In particular, decreases in short woody 

cover occurred in all valley segments between 1940 and 1968 

(except for the South Fork valley segment, for which aerial 

photograph coverage in 1940 includes only 12 percent of the 

analysis area). Likewise, all valley segments except Chiloquin 

Canyon gained herbaceous cover during 1968–2000. Partly 

in conjunction with the gain in herbaceous cover, nearly 

all valley segments lost water and bare are areas during the 

1968–2000 period.

As a percentage of flood-plain area, the more confined 

valley segments of Chiloquin Canyon, Braymill, S’Ocholis 

Canyon, and Beatty Gap had similarly large losses of short 

woody cover, with each of these valley segments having 

reductions of between 5 and 7 percent of short woody cover 

between 1940 and 1968 (table 11). These decreases, however, 

were matched or exceeded by the 7 percent decrease in 

short woody vegetation in the Upper Valley segment and 

the 12 percent decrease in the Lower Sycan valley segment 

between 1940 and 1968. Both of these valley segments had 

substantial expansions of herbaceous cover during this same 

time period. Changes as a percentage of flood-plain area 

generally were smaller during the 1968–2000 period, with 

only two valley segments showing any cover-type change 

greater than 5 percent during the more recent analysis period 

compared to 6 of the 10 segments with such changes during 

the 1940–1968 period.

The temporal trends in the near-channel area for the 

main-stem Sprague River (excluding the North and South 

Forks) and Lower Sycan River were similar to trends for 

the entire flood plain, but with greater fluctuations in water, 

bare, and short woody cover types (table 12; fig. 62). The 

difference in water and bare cover types partly represents 

the higher water levels during acquisition of the 1968 aerial 

photographs and the bar growth during the December 26, 

1964 flooding. The loss of short woody vegetation, however, 

matches the long-term trend for the entire flood plain, although 

the relative magnitude is even greater for the near-channel 

area, where the total area decreased by nearly 50 percent, 

from 154 ha (14 percent of the near-channel area) in 1940 to 

87 ha (8 percent of the near-channel area) in 2000. Most of 

this decrease was during the 1940–1968 period, when 67 ha 

were lost. Documented loss of short woody vegetation would 

have been larger if the North Fork and South Fork valley 

segments were included in these tabulations; despite the 

incomplete aerial photographic coverage for 1940, declines in 

short woody vegetation cover are evident for those segments 

as well, particularly for 1968–2000 period of complete aerial 

photograph coverage.

Like the entire flood plain, all valley segments (except 

the South Fork) had a net loss of short woody cover in 

near-channel areas between 1940 and 2000. The greatest 

relative losses (exceeding 50 percent of the 1940 area) were 

in the Kamkaun Spring, Buttes of the Gods, Council Butte, 

Beatty-Sycan, Upper Valley, North Fork, and Lower Sycan 

valley segments (table 12, fig. 62). A similar reduction likely 

affected the South Fork valley segment except that the 1940 

photograph coverage is incomplete. Compared to most other 

valley segments, Beatty Gap had a smaller relative loss of short 

woody vegetation between 1940 and 2000, but this segment 

also had a nearly 50 percent loss in tall woody vegetation in the 

near-channel area during this time period.

Vegetation Transitions

Although temporal and spatial trends can hint at 

controlling processes, information on the site-specific changes 

of cover types supports more specific interpretations. A 

transition matrix analysis identifies all of the possible changes 

in land cover classes, allowing determination of transitions 

that are most prevalent during different time periods. Such 

transitions can be related to successional processes as well as 

human and natural disturbances. Transition matrix analysis 

has been used in landscape scale investigations of land use 

(Petit and others, 2001), grassland and woodland interactions 

(Hibbard and others, 2003), and dune and delta environments 

(Shanmugam and Barnsley, 2002; Biondini and Kandus, 2006).

This analysis evaluated the change in mapped cover type 

for each square meter of flood plain between 1940 and 1968 

(appendix table H1) and between 1968 and 2000 (appendix 

table H2). For each analysis period, cover changes were 

recorded as 1 of 21 transitions, accounting for the 20 possible 

transitions of one cover type to another plus that of “No 

Change.” As for the general cover-type characterization, the 

transition analysis also was conducted for the near-channel 

area composed of the 20 m extending laterally in each direction 

from the channel centerline (appendix tables H3, H4). For the 

near-channel transition analysis, the analysis area remained 

fixed about the 1940 centerline, except for where 1940 aerial 

photograph coverage was unavailable upstream of FK 95.2 on 

the South Fork valley segment and upstream of NFFK 5.8 on 

the North Fork valley segment. For the upstream parts of these 

valley segments, the transition analysis was restricted to the 

1968–2000 time period for the near-channel area flanking the 

1968 channel centerline.

For both time periods (1940–1968 and 1968–2000), more 

than 90 percent of the flood-plain surface within the analysis 

area did not change cover type (appendix tables H1, H2). 

Nevertheless, the confined segments were more dynamic, 

with about 20 percent or more of the flood plains in each of 

the Chiloquin Canyon, Braymill, S’Ocholis Canyon, Beatty 

Gap, and Lower Sycan valley segments changing cover classes 

during each of the analysis periods (fig. 63). Vegetation classes 

in the unconfined valley segments remained unchanged for 

about 90 percent of the flood-plain areas. The South Fork valley 

segment was the most static, with 98 percent of its flood plain 

remaining the same cover type for the 1968–2000 period.
96 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 63

0

5

10

15

20

25

30

A. Flood plain

0

10

20

30

40

50

B. Near channel

Area with change in vegetation cover class, in percent

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

1940–1968

1968–2000

Time period

EXPLANATION

Incomplete aerial

photograph coverage

Figure 63. Percentage of valley segment area in which cover type changed in (A) entire geomorphic flood plain, 

and (B) near-channel area, Sprague River Basin, Oregon, during 1940–1968 and 1968–2000 analysis periods.

The near-channel area was more dynamic than the flood 

plain as a whole, with 25 percent of the area changing cover 

class during the 1968–2000 period (27 percent between 1940 

and 1968) (appendix tables H3, H4; fig. 63). These higher 

near-channel rates explain the relatively high rates of total 

flood plain transitions in the confined reaches (fig. 63A), where 

the near-channel areas constitute a greater percentage of the 

flood-plain area. The most dynamic valley segments in terms 

of near-channel vegetation transition were the Lower Sycan 

and North Fork valley segments, where about 40 percent 

of the near-channel area changed cover classes during both 

analysis periods. The Upper Valley, Beatty Gap, and S’Ocholis 

Canyon valley segments also had more than 25 percent of the 

near-channel area-change cover types during both analysis 

periods. The valley segments with the most consistently stable 

near-channel vegetation cover class were the Buttes of the 

Gods, Chiloquin Canyon, and Braymill segments, for which 

less than 20 percent of near-channel area changed during the 

1968–2000 analysis period.

Examination of the individual transition categories also 

reveals trends (figs. 64, 65), clarifying changes evident from 

the overall change analysis. The greatest changes for both 

time periods (1940–1968 and 1968–2000) and for both the 

entire flood-plain and near-channel areas involved cover-type 

transitions between (1) short woody and herbaceous, (2) water 

and herbaceous, and (3) water and short woody. In particular, 

for the 1940–1968 period, nearly every segment showed 

substantial conversion from short woody to herbaceous 

and short woody to water. For the 1968–2000 period, these 

particular transitions were more balanced.
Flood-Plain and Riparian Vegetation 97

tac14-0898_fig 64

Chiloquin Canyon 

Braymill

Kamkaun Spring 

S’Ocholis Canyon 

Buttes of the Gods 

Council Butte 

Beatty-Sycan

Beatty Gap 

Upper Valley

South Fork 

North F ork

Lower Sycan

Valley segment

Incomplete aerial

photograph coverage

EXPLANATION

A. 1940–1968

Cover type transition, in percent

10 5 0 5 10

Water

to

Tall woody

Bare

to

Tall woody

Herbaceous

to

Tall woody

Short woody

to

Tall woody

Water

to

Short woody

Bare

to

Short woody

Herbaceous

to

Short woody 

Water

to

Herbaceous

Bare

to

Herbaceous

Water

to

Bare

Tall woody

to

Water

Tall woody

to

Bare

Tall woody

to

Herbaceous

Tall woody

to

Short woody

Short woody

to

Water

Short woody

to

Bare

Herbaceous

to

Water 

Herbaceous

to

Bare

Bare

to

Water

B. 1968–2000

10 5 0 5 10

Water

to

Tall woody

Bare

to

Tall woody

Herbaceous

to

Tall woody

Short woody

to

Tall woody

Water

to

Short woody

Bare

to

Short woody

Water

to

Herbaceous

Bare

to

Herbaceous

Water

to

Bare

Tall woody

to

Water

Tall woody

to

Bare

Tall woody

to

Herbaceous

Tall woody

to

Short woody

Short woody

to

Water

Short woody

to

Bare

Short woody

to

Herbaceous

Herbaceous

to

Water 

Herbaceous

to

Bare

Bare

to

Water

Short

woody

to

Herbaceous

Herbaceous

to

Short woody 

Figure 64. Cover-type transitions for geomorphic flood plain, summarized by valley segment, during (A) 1940–1968 (analysis 

area limited in South Fork and North Fork valley segments by incomplete 1940 aerial photograph coverage), and (B) 1968–2000, 

Sprague River Basin, Oregon. Transitions to the right of the vertical lines generally represent increasing seral stage and structural 

complexity.
98 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 65

Chiloquin Canyon 

Braymill

Kamkaun Spring 

S’Ocholis Canyon 

Buttes of the Gods 

Council Butte 

Beatty-Sycan

Beatty Gap 

Upper Valley

South Fork 

North F ork

Lower Sycan

Valley segment

Incomplete aerial

photograph coverage

EXPLANATION

A. 1940–1968

Cover type transition, in percent

20 10 0 10 20

Water

to

Tall woody

Bare

to

Tall woody

Herbaceous

to

Tall woody

Short woody

to

Tall woody

Water

to

Short woody

Bare

to

Short woody

Herbaceous

to

Short woody 

Water

to

Herbaceous

Bare

to

Herbaceous

Water

to

Bare

Tall woody

to

Water

Tall woody

to

Bare

Tall woody

to

Herbaceous

Tall woody

to

Short woody

Short woody

to

Water

Short woody

to

Bare

Herbaceous

to

Water 

Herbaceous

to

Bare

Bare

to

Water

B. 1968–2000

20 10 0 10 20

Water

to

Tall woody

Bare

to

Tall woody

Herbaceous

to

Tall woody

Short woody

to

Tall woody

Water

to

Short woody

Bare

to

Short woody

Water

to

Herbaceous

Bare

to

Herbaceous

Water

to

Bare

Tall woody

to

Water

Tall woody

to

Bare

Tall woody

to

Herbaceous

Tall woody

to

Short woody

Short woody

to

Water

Short woody

to

Bare

Short woody

to

Herbaceous

Herbaceous

to

Water 

Herbaceous

to

Bare

Bare

to

Water

Short

woody

to

Herbaceous

Herbaceous

to

Short woody 

Figure 65. Cover-type transitions for the 40-meter-wide, near-channel zone centered about 1940 channel centerline (1968 

centerline for South Fork and North Fork valley segments for 1968–2000), summarized by valley segment, during (A) 1940–1968, and 

(B) 1968–2000, Sprague River Basin, Oregon. Transitions to the right of the vertical lines generally represent increasing seral stage 

and structural complexity.
Flood-Plain and Riparian Vegetation 99

Other pronounced transitions include the widespread 

transition of bare to herbaceous and water to herbaceous in the 

1968–2000 period, again representing the lower water level 

shown in the 2000 aerial photographs and the greater area of 

bars in the 1968 photographs (figs. 64, 65). Also evident is 

the widespread conversion of the tall woody cover class to 

other cover types during the 1968–2000 period. This trend is 

apparent only for the flood plain as a whole and is not evident 

in the near-channel area, indicating that most of the loss of tall 

woody vegetation was in areas away from the channel.

These transitions can be viewed with respect to 

successional pathways and vegetative structural complexity. 

In the absence of disturbance, the expected successional 

progression is bare to herbaceous to short woody to tall 

woody. This progression also generally results in increasing 

structural complexity, involving increasing diversity of plant 

types, plant heights and habitat heterogeneity. Movement 

in the opposite direction typically requires some sort of 

disturbance. From this perspective, cover-type transitions 

to the right of the central vertical lines in figures 64 and 65

indicate increasing seral stage and structural complexity, 

whereas those to the left indicate decreasing seral stage and 

complexity, likely resulting from site disturbances or erosion. 

Therefore, the aerial photograph analysis generally shows 

decreasing seral stage for most possible transitions for the 

1940–1968 period for the flood-plain and the near-channel 

corridor, particularly for areas covered by short woody 

vegetation in 1940. For the 1968–2000 period, the analysis 

of the flood plain shows systematic decreasing seral stage 

associated with tall woody vegetation, but herbaceous growth 

in many areas that were either bare or underwater in 1968. 

Many valley segments also had conversions from herbaceous 

to short woody vegetation. Findings generally were similar 

for the 1968–2000 period in the near channel area, aside from 

little evidence for the decreasing tall woody cover class seen 

at the flood-plain scale.

Summarizing the transitions by increasing and decreasing 

seral stage for each valley segment shows that, for all valley 

segments, the relative area of decreasing seral stage was 

greater in the 1940–1968 period than in the 1968–2000 period 

for both the flood-plain and near-channel areas (fig. 66). 

However, 1940–1968 decreases generally were greater in the 

near-channel areas, particularly for the S’Ocholis Canyon, 

Beatty Gap, Upper Valley, and Lower Sycan valley segments. 

The Beatty Gap and Lower Sycan valley segments also had 

large net decreases in seral stage when considering the entire 

flood-plain area. Many of these segments with substantial 

1940–1968 decreases, however, had net increases in seral 

stage for the 1968–2000 period, especially the S’Ocholis 

Canyon, Beatty Gap, and Lower Sycan valley segments.

Major Vegetation Changes and Their Causes

These vegetation cover-type changes—in conjunction with 

understanding of successional processes, land-use, and channel 

and flood-plain dynamics—allow for the inference of the key 

factors controlling present vegetation patterns and recent trends 

in the Sprague River study area. Beyond this, Rasmussen (2011) 

provides more specific information on relations between channel, 

soil moisture, land-use, and riparian vegetation processes in the 

Sprague River study area.

Transitions Among Water, Bare, and Herbaceous 

Cover Classes

Variations and transitions among these cover classes owe 

chiefly to changes in channel pattern, inundation, and disturbance. 

Historical observations and the aerial photograph analyses show 

that the flood plains, especially for the unconfined segments, 

were vegetated mostly by herbaceous species (figs. 61, 62). 

Therefore, transitions involving herbaceous cover tend to occupy 

larger areas than for other cover types. Transitions between water 

and herbaceous cover types result primarily from (1) channel 

movement, either by lateral erosion or avulsion, into flood-plain 

areas covered by herbaceous vegetation; (2) inundation of areas 

covered by herbaceous vegetation; (3) excavation of ditches 

and storage ponds; and (4), in the other direction, emergence 

or colonization of herbaceous vegetation in areas formerly 

covered by water. All these processes probably were important 

in the analysis area. The total net reduction in water-covered 

area between 1940 and 2000, mainly resulting from decreased 

channel sinuosity, accounts for 29 percent of the increase in 

herbaceous area in the region during this period (appendix 

tables H1, H2). Furthermore, the lower water levels in the 2000 

aerial photographs compared to those of the 1968 photographs 

is the chief reason for the substantial transition of water cover 

to herbaceous cover between 1968 and 2000 (figs. 64 and 65), 

although the 1–6 percent of the near-channel area that changed 

from herbaceous cover to water cover during this time period 

likely represents channel migration.

Bare areas indicate recent disturbance. This is most evident 

in the substantial increase in bare area shown by the 1968 aerial 

photographs, particularly in the near-channel areas (figs. 61, 62). 

This is consistent with the increased bar area at this time (fig. 38) 

and almost certainly represents erosion and deposition during 

December 1964 flooding, primarily in areas formerly covered by 

herbaceous vegetation. Some bare areas, however, are created and 

maintained by livestock trampling, roads, and water access paths 

(fig. 67). The consistent reduction of bare area and conversion of 

bare cover to herbaceous cover in the Chiloquin Canyon valley 

segment likely represents less land disturbance resulting from 

mill closure.
100 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

tac14-0898_fig 66 Area seral stage transition, in percent

-20

-15

-10

-5

0

5

10

15

20

Increased seral stage Decreased seral stage Increased seral stage Decreased seral stage

-40

-30

-20

-10

0

10

20

30

A. Flood plain

B. Near channel

Chiloquin 

Canyon

Braymill Kamkaun 

Spring

S’Ocholis 

Canyon

Buttes of 

the Gods

Council 

Butte

BeattySycanBeatty 

Gap

Upper 

Valley

South 

Fork

North 

Fork

Lower 

Sycan

Valley segment

1940–1968

1968–2000

Time period

EXPLANATION

Incomplete aerial

photograph coverage

Figure 66. Summary of seral stage trends in (A) entire geomorphic flood plain, and (B) near-channel area, 

Sprague River Basin, Oregon, during 1940–1968 and 1968–2000.

Figure 67. Trampled sand-and-gravel point bar looking upstream 

near Sycan River flood-plain kilometer 0.1 along Sycan River, 

Oregon. Photograph taken by J.E. O’Connor, U.S. Geological 

Survey, September 12, 2007.
Flood-Plain and Riparian Vegetation 101

Short Woody Vegetation

Historical observations noted willow and currant 

along the channel throughout the study area, including 

small amounts in the unconfined valley segments otherwise 

vegetated mainly by herbaceous cover types. Short woody 

vegetation has decreased substantially since those historical 

observations, particularly in the Beatty-Sycan, Upper Valley, 

and South Fork valley segments where William E. Lawrence 

recorded conditions in the early 1900s. This trend has 

continued for several valley segments during the 1940–2000 

photograph analysis period when the area of short woody 

vegetation decreased by 38 percent in the flood plain and by 

50 percent in the near-channel area (appendix tables H1–H4). 

Most of these losses were in the 1940–1968 time period 

and involved transitions to herbaceous, water, and bare cover 

types (figs. 64, 65). For the Lower Sycan valley segment, these 

three transitions encompassed 20 percent of the near-channel 

area. These vegetation changes all represent decreases in seral 

stage, indicating active disturbance processes. Additionally, 

short woody vegetation in 1940 formed large patches, with 

no apparent preference for near-channel zones. Patches were 

much smaller and much more fragmented in 1968 than in 

1940. Subsequent to 1968, the area occupied by short woody 

cover continued to decrease, but by a much smaller fraction, 

and many valley segments gained more short woody cover 

from succession from water, bare, and herbaceous cover types 

than was lost by disturbance.

Many factors probably account for the decrease in short 

woody vegetation. Areas of transition from short woody 

cover to water and bare cover probably represent, at least in 

part, fluvial erosion of riparian shrubs from channel margins. 

However, as described for other montane environments 

(Schulz and Leininger, 1990; Green and Kauffman, 1995; 

Holland and others, 2005), livestock trampling and grazing 

also are likely factors in reducing the area of short woody 

vegetation, especially in the many areas where losses 

resulted from shrinking and fragmentation of short woody 

vegetation patches (instead of complete removal, which would 

result from mechanical conversion to pastureland). This 

transition from short woody cover to bare cover accounts for 

21–40 percent of the near-channel areas losing short woody 

cover between 1940 and 1968, with the largest losses in the 

confined Chiloquin Canyon, Braymill, and S’Ocholis Canyon 

valley segments. Some unknown part of this change owes 

to the higher water levels of 1968, but the 2–18 percent of 

the near-channel areas that transitioned from short woody 

cover to bare cover between 1940 and 1968 almost certainly 

resulted from fluvial erosion, except for isolated locations of 

human disturbance.

The transition from short woody cover to herbaceous 

cover was the most frequent transition associated with loss 

of short woody cover for all valley segments for both the 

1940–1968 and 1968–2000 time periods, and for both the 

near-channel area and entire flood plain. For near-channel 

areas, this transition accounted for 40–70 percent of the loss 

in each valley segment for 1940–1968 and 64–91 percent 

for 1968–2000. This transition was even a larger factor for 

the entire flood plain, accounting more than 90 percent of 

the short woody vegetation loss for several of the wider 

and unconfined valley segments. In near-channel areas, this 

transition can also be due to fluvial erosion and subsequent 

colonization of bare surfaces by herbaceous vegetation. But 

the widespread transition of short woody cover to herbaceous 

in flood-plain areas away from the near-channel zone indicates 

that fluvial erosion was likely not a major factor. More likely 

is that conversion to pasture and agriculture contributed to the 

loss of short woody vegetation on flood plains. Additionally, 

livestock grazing and mechanical removal (as was the case for 

willow removal along the Sprague River during the 1950s and 

1960s) can convert short woody cover to herbaceous (Schultz 

and Leininger 1990; Green and Kauffman 1995; Holland and 

others, 2005). Both of these activities have probably been 

significant contributors to the loss of short woody vegetation 

in the Sprague River Basin, particularly between 1940 

and 1968.

Other factors possibly contributing to the decrease in 

short woody cover are disease, insects, and predation by 

wildlife. After sustained high water in spring 2006, willow 

stands across much of the basin were infected with a rust 

fungus during the following growing season. Leaves yellowed 

and fell in mid-season, although they re-foliated normally the 

following spring. Predation by beaver and muskrat is prevalent 

throughout the study area, although it is greatest in patches 

in the near-channel zone. Isolated shrubs and small willow 

patches in the wide flood-plain segments can be decimated by 

beaver predation where activity is concentrated. Over time, 

these local pressures on shrub growth may become evident at 

the level mapped in this study, although their present effects 

are unknown.

Tall Woody Vegetation

Tall woody vegetation typically is sparser than all other 

cover types in the study area, and was not present in 2000 

for the Buttes of the Gods, Beatty-Sycan, and Upper Valley 

segments (table 11; fig. 61). However, in the Chiloquin 

Canyon, Braymill, and S’Ocholis Canyon segments, tall 

woody cover has increased by 32–66 percent between 

1940 and 2000. Most of the increase has been from water, 

herbaceous and short woody cover types, indicating general 

succession in these historically timbered flood-plain sections.

In the Beatty Gap valley segment, however, tall woody 

cover has decreased from 9.8 ha to 6.1 ha between 1940 and 

2000 (appendix H tables H1, H2; fig. 61). About 40 percent of 

the loss was from the near-channel area (fig. 62). A small part 

of the decline in tall woody cover resulted from tall woody 

cover areas transitioning to water (particularly between 1940 

and 1968), probably from fluvial erosion of timbered stands 

(fig. 28). However, 75 percent of the net decrease in tall 

woody vegetation resulted from transition to short woody 
102 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

cover types, particularly in the near-channel area between 

1940 and 1968 and for the broader flood plain between 1968 

and 2000. This transition possibly owes to dieback of aspen 

patches. Recent losses from the near-channel area may be 

from beaver, for which there was evidence of active felling 

during the 2006 synoptic survey.

Summary of Flood-Plain and Near-Channel 

Vegetation Conditions

Broadscale basin characteristics strongly influence 

the general spatial patterns of vegetation in the Sprague 

River flood plain. These patterns, as mapped from the 2000 

aerial photographs, are similar to those recorded by the 

first government surveys in the 1800s. Tall woody species 

prefer narrow, confined, and shaded flood plains; wide 

flood plains mostly are covered with herbaceous plants, 

but past and present channel areas locally are flanked by 

short woody vegetation. These predominant attributes have 

remained constant since the first historical observations, 

chiefly because the areas within the study area have remained 

generally pastoral without substantial urbanization, timber 

harvest (within the flood plain), or changes in flow and 

sediment regimes.

The assessment of the 1940–2000 aerial photographs, 

however, shows that at finer scales near-channel areas 

are more dynamic than the flood plain as a whole. About 

25 percent of the near-channel area changed cover class during 

each 28–32-yr analysis period, compared to only 10 percent 

for the flood plain. The greater vegetation dynamics of the 

near-channel area indicate the important roles of fluvial 

disturbance and succession in creating riparian vegetation 

communities, perhaps exacerbated by predation and 

concentrated grazing.

Despite the general stability of overall vegetation 

patterns, clear trends are evident among individual cover 

types. The most systematic and broadscale change has been 

the loss of short woody vegetation—only one-half of the nearchannel area covered by short woody vegetation in 1940 was 

similarly covered in 2000. The loss of short woody vegetation 

to less complex early seral stages was the major change among 

many indicating vegetation disturbance and loss of structural 

complexity. These changes were most prevalent prior to 1968. 

In the 1940–1968 period, the Kamkaun Spring, S’Ocholis 

Canyon, Beatty Gap, Upper Valley, and Lower Sycan valley 

segments generally showed the greatest decreases in seral 

stage. The North Fork and South Fork valley segments also 

likely lost short woody vegetation during this period, but 

quantitative information is not available prior to 1968. Since 

1968, overall vegetation trends are not as strong except for 

(1) continued loss of short woody cover in all valley segments 

upstream of the confluence of the Sycan and Sprague Rivers, 

(2) loss of bare area in nearly all valley segments, and 

(3) increase in tall woody vegetation in the Chiloquin Canyon 

and Braymill valley segments.

These changes have resulted from a combination of 

geomorphic processes and trends, vegetation succession, direct 

vegetation manipulation, and broadscale land-use. Transitions 

among the bare and water cover types chiefly are the result of 

decreased sinuosity, different water levels at the time of the 

aerial photographs, and the December 1964 flooding, which 

created many bare bar areas evident in the 1968 photographs. 

Vegetation succession locally has increased seral stage and 

habitat complexity, partly balancing the effects of disturbance 

processes, particularly since 1968. Woody vegetation removal 

in the 1950s and 1960s and continuing grazing and trampling 

by livestock probably are the main reasons for the decline 

of short woody vegetation from the dense riparian corridors 

of willows and other riparian shrubs noted in the early 

20th century.

Implications for Restoration and 

Monitoring

As is the case for other rivers (Jaquette and others, 2005; 

Wohl and others, 2005), understanding of historical conditions, 

trends, and channel and flood-plain processes can help in the 

design of effective restoration and monitoring strategies for 

improving ecological function of the Sprague River fluvial 

corridor. Consistent with the scale of the analyses in this study, 

this assessment focuses on broadscale conditions, controls, 

and approaches, recognizing that some key ecologic issues 

require attention at local scales and short time frames. This 

assessment also emphasizes physical conditions, following the 

premise that geologic, geomorphic, and hydrologic processes 

provide the basic physical framework in which ecologic 

systems operate.

Status and Trends

Knowledge of present conditions and historical trends can 

clarify restoration objectives, opportunities, and constraints 

for the Sprague River study area (table 13). Most importantly, 

most physical processes that have formed the present channel 

and flood plain still substantially operate at the basin scale. 

Essential flow and sediment transport conditions have not 

been significantly changed, although such processes are 

dynamic and controlled by basin-scale factors such as climate, 

sediment production, and possibly land use. Therefore, key 

processes of lateral and longitudinal connectivity remain 

active. This contrasts with many western rivers in which 

dams and diversions have affected basin-scale sediment 

and water fluxes, and where channel incision has limited 

interaction between channels and flood plains. Because these 

overall basin conditions have not been altered significantly, 

the historical conditions prior to extensive flood‐plain and 

channel modification provide a plausible reference frame for 

restoration objectives.
Implications for Restoration and Monitoring 103

Table 13. General valley segment trends and conditions, with implications for restoration, Sprague River Basin, Oregon

Chiloquin Canyon Braymill Kamkaun Spring

Major historical changes to flood plain and channel

Construction and removal of Chiloquin

Dam, historical timber harvest, grazing,

local road encroachment; local colonization

by reed canarygrass.

Development and removal of Braymill

mill facilities, historical timber harvest,

grazing, local road encroachment; decreased

channel migration; local colonization by

reed canarygrass.

Confinement by levees and railroad, local

channel remeandering; increased channel

width, bar area; decreased sinuosity and

channel migration rates; frequent avulsons

and cutoffs; vegetation removal, decreased

short woody vegetation; flood-plain

cultivation and grazing. 

Important process changes

Minimal, although sediment and woody

debris associated with 2008 Chiloqin Dam

removal locally may affect lower part of

segment.

Minimal Confinement of overbank flows; possibly

increased incidence of cutoffs and avulsions

associated with flood-plain modifications;

locally restricted channel migration by

levees and bank protection.

Restoration implications

Natural process regime largely intact;

most ecologic goals likely attained by

minimizing alterations to geomorphic flood

plain, allowing channel migration and

riparian vegetation succession; locally

dense stands of reed canarygrass may slow

natural regeneration of short woody

vegetation.

Similar as for Chiloquin Canyon segment. Natural process regime largely intact;

reducing overbank flow confinement by

levees, roads, and railroad embankments

would promote flood-plain deposition and

possibly reduce frequency of avulsions and

cutoffs; minimizing bank hardening and

promoting channel migration processes

likely would increase sinuosity and decrease

channel slope over decadal time scales;

protection of riparian areas from trampling

and excessive browsing likely would 

increase amount short woody vegetation;

channel slope and fluvial energy low, so

natural processes slow to modify channel

and flood plain conditions. 
104 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Table 13. General valley segment trends and conditions, with implications for restoration, Sprague River Basin, Oregon.—Continued

S'Ocholis Canyon Buttes of the Gods Council Butte

Major historical changes to flood plain and channel

Decreased channel migration rates; increased

tall woody vegetation, decreased short

woody vegetation.

Confinement by levees and railroad; 

vegetation removal and flood-plain

cultivation and grazing; increased channel

slope; decreased channel migration rates;

frequent avulsions and cutoffs; reduced short

woody riparian vegetation; local channel

remeandering.

Extensive confinement by levees, roads, and

railroad; vegetation removal, and flood‐plain

leveling; flood-plain and riparian cultivation

and grazing; increased channel slope;

decreased channel width, sinuosity, and

migration rates; local incision; reduced

short woody riparian vegetation; local

channel remeandering.

Important process changes

Minimal Confinement of overbank flows; possibly

increased incidence of cutoffs and avulsions

associated with flood-plain modifications;

locally restricted channel migration by levees

and bank protection.

Local historical incision may reduce

frequency and extent of overbank flows;

confinement of overbank flows; possibly

increased incidence of cutoffs and avulsions

associated with flood-plain modifications;

locally restricted channel migration by levees

and bank protection.

Restoration implications

Natural process regime largely intact;

most ecologic goals likely attained by

minimizing alterations to geomorphic flood

plain, allowing channel migration and

riparian vegetation succession; woody debris

derived from riparian vegetation in this

segment may be important for downstream

habitat and channel structure.

Similar to restoration implications for

Kamkaun Spring segment although low

banks in this reach do not favor

colonization of short woody vegetation.

Natural process regime largely intact;

reducing overbank flow confinement by

levees, roads, and railroad embankments

likely to promote flood-plain deposition

and possibly reduce likelihood of future

incision and frequency of avulsions and

cutoffs; minimizing bank hardening and

promoting channel-migration processes

likely would increase sinuosity and decrease

channel slope; protection of riparian areas

from trampling and excessive browsing

likely to increase locally amount short

woody vegetation although abundant low

banks mostly more favorable for riparian

herbaceous growth; channel slope and fluvial

energy exceptionally low, so natural

processes slow to modify channel and

flood‐plain conditions.
Implications for Restoration and Monitoring 105

Table 13. General valley segment trends and conditions, with implications for restoration, Sprague River Basin, Oregon.—Continued

Beatty-Sycan Beatty Gap Upper Valley

Major historical changes to flood plain and channel

Confinement by levees and railroad;

flood‐plain leveling, cultivation and grazing;

reduced riparian woody vegetation; local

channel remeandering.

Local incision, likely historical timber

harvest; increased channel slope and reduced

sinuosity; diminished woody vegetation.

Flood-plain ditches and levees confine

overbank flow; increased channel width;

reduced channel slope and sinuosity; local

incision; reduced riparian vegetation .

Important process changes

Local historical incision may reduce

frequency and extent of overbank flows;

confinement of overbank flows; possibly

increased incidence of cutoffs and avulsions

associated with flood-plain modifications;

locally restricted channel migration by levees

and bank protection.

Local historical incision may reduce

frequency and extent of overbank flows;

confinement of overbank flows; possibly

increased incidence of cutoffs and avulsions

associated with flood-plain modifications;

local inhibition of channel migration by

levees; possible decreased abundance of

large in-channel wood.

Local historical incision may reduce

frequency and extent of overbank flows;

confinement of overbank flows; possibly

increased incidence of cutoffs and avulsions

associated with flood-plain modifications; 

locally restricted channel migration by levees

and bank protection; possible decreased

abundance of large in-channel wood.

Restoration implications

Similar to restoration implications for

Council Butte valley segment.

Natural process regime largely intact aside

from consequences of local incision; most

ecologic goals likely attained by minimizing

alterations to geomorphic flood plain,

protection from incision, and allowing

channel migration and riparian vegetation

succession; promoting short and tall woody

vegetation grown for this segment may have

broader consequences because of the role

of large wood generated in this segment for

downstream in-channel wood supply; more

energetic fluvial environment should result in

dynamic channel and flood-plain evolution. 

Similar to restoration implications for

Council Butte valley segment.
106 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Table 13. General valley segment trends and conditions, with implications for restoration, Sprague River Basin, Oregon.—Continued

South Fork North Fork Lower Sycan

Major historical changes to flood plain and channel

Transformed from peat-forming wetland

complex to incised and channelized flood

plain; extensive channel excavation and 

straightening (and loss of sinuosity),

incision, channel diversion structures;

decreased channel width and channel

migration rates; substantial incision;

vegetation removal and substantial woody

vegetation loss.

Flood-plain levees, ditches, leveling,

cultivation, and grazing; in-channel

diversions; possible local incision; reduced

short woody riparian vegetation.

Possible local channel incision, local bank

trampling, and road encroachment; some

flood-plain levees, cultivation, and grazing;

spring diversions; decreased short woody

vegetation.

Important process changes

Conversion from multi-channel wetland

to incised single channel; diminished

overbank flooding, channel migration;

increased sediment entrainment from channel

incision and flood-plain erosion; decreased

channel interaction with in-channel wood

and riparian vegetation.

Local historical incision and confinement

may reduce frequency and extent of

overbank flows; channel migration locally

restricted by levees and bank protection;

possible decreased abundance of large

in‐channel wood; longitudinal connectivity

reduced by in-channel diversion structures.

Local historical incision and confinement

may reduce frequency and extent of

overbank flows; locally restricted channel

migration by levees and bank protection;

disturbance of Sycan flood surfaces may

enhance bank erosion and sediment delivery

to channel.

Restoration implications

Significant historical transformation and

incision of this valley segment probably

requires active and substantial channel

and flood-plain modifications to attain

conditions similar to the low-energy wet

meadow environment of early historical

observations within decadal time frames;

interrelated goals to attain historical

conditions would include increasing

sinuosity and overbank flooding, reducing

flow confinement and bank hardening,

facilitating processes promoting channel and

flood-plain aggradation, increasing riparian

vegetation, maintaining high water tables,

and possibly promoting beaver colonization.

Natural process regime largely intact aside

from consequences of local incision and

diversion; most ecologic goals likely attained

by minimizing alterations to geomorphic

flood plain, protecting flood plains from

incision, and allowing channel migration and

riparian vegetation succession.

Similar to restoration implications for North

Fork, but with specific attention to protecting

sandy Sycan flood surfaces from vegetation

disturbance and enhanced erosion.

Coyote Bucket

Major historical changes to flood plain and channel

Minimal

Important process changes

Minimal

Restoration implications

Natural process regime largely intact
Implications for Restoration and Monitoring 107

Although most important physical processes still 

function, systematic trends in channel and flood-plain 

conditions indicate broadscale human influence. In particular, 

declining sinuosity, increased channel slope, decreased 

migration rates, local channel incision, and less short woody 

vegetation probably are the interrelated consequences of floodplain and channel alterations. Channel confinement by levees 

and other built features probably is the single most important 

factor contributing to these changes, but the direct and indirect 

consequences of other manipulations, such as local flow 

diversion and concentration, grazing, vegetation removal, 

and beaver eradication, also have been important, particularly 

at the valley segment scale. Channel and flood‐plain 

changes, including vegetation, were most evident for the 

period between 1940 and 1968, coinciding with increased 

use of heavy equipment for flood control and developing 

irrigation structures.

The slowing of many of these trends between 1968 

and 2000 indicates that reversal is possible and that some 

channel and flood-plain attributes are potentially restorable 

to near-pre-development conditions. This is particularly true 

downstream of the confluence of the North Fork and South 

Fork Sprague Rivers, where there has been little incision. For 

this broad area of the Sprague River study area, in which flood 

flows regularly inundate the flood plain, natural processes 

may be sufficient to reverse historical broadscale trends, 

particularly if alterations such as flood-plain confinement, 

bank trampling, and bank hardening are reversed.

Conditions are different in the eastern valley segments 

(table 13). Particularly for the South Fork valley segment, and 

to a lesser degree in the Upper Valley segment and possibly 

the North Fork valley segment, historical and ongoing 

channel incision and flood-plain erosion will inhibit reversal 

of historical trends and likely will continue to be a source of 

suspended sediment load to the river system. For the South 

Fork valley segment, incision likely will continue as long as 

the channel is fully constrained by levees and dikes and until 

knickzones and other erosional areas progress to locations 

where channel and flood-plain substrate resists continued 

downcutting and gully expansion. Current and historical trends 

are not likely to be reversed until a more natural channel and 

flood-plain geometry is attained and the channel aggrades to 

the extent that overbank flow becomes common.

Spatial and Temporal Scales

The mapping, stratigraphic investigations, and 

quantitative channel and flood-plain analyses provide context 

for restoration objectives and approaches to monitoring. Most 

broadly, the geomorphic flood plain is the domain of nearly 

all key hydrologic and geomorphic processes shaping the 

channel and flood plain. Some areas outside the geomorphic 

flood plain are inundated by flooding, particularly some 

areas of main-stem valley fill, but only the geomorphic 

flood plain has been subject to channel-forming processes 

for the last several thousand years. Therefore, the greatest 

likelihood of restoration to pre-development conditions would 

result from a strategy emphasizing natural processes for the 

entire geomorphic flood plain. Historically, most channel 

processes operated within narrow corridors; therefore, it 

may be possible to reverse historical changes in the channel 

by focusing on more limited areas adjacent to the present 

channel. Such a strategy, however, carries some risk, since 

avulsions and cutoffs, which create ecologically important 

flood-plain features, require access to areas outside the 

near-channel environment.

The valley segments also provide a spatial context 

for restoration and monitoring. Conditions, trends, and 

processes vary significantly among the segments (table 13), 

and restoration strategies are likely to be most successful 

if tailored to specific segments and the important processes 

and conditions within those segments. For example, the 

fundamental changes to the South Fork valley segment (such 

as the channel straightening and incision) make it unlikely to 

recover natural process regimes and morphologies without 

active manipulation (possibly including relocating the channel 

and increasing sinuosity), whereas other valley segments 

likely would achieve high levels of channel and flood-plain 

function by adoption of more passive strategies such as 

protection of the riparian corridor and levee breaching.

More broadly, the unconfined and confined segments 

have different vegetation characteristics, morphologies, and 

process regimes. Most of the decreases in sinuosity are in 

the unconfined valley segments (fig. 60), partly because of 

confinement of these segments locally by levees and railroad 

grades. All segments have lost short woody vegetation, 

but percentagewise, the losses have been greatest in the 

unconfined valley segments, particularly in near-channel 

areas (figs. 61, 62). The unconfined segments historically 

and presently had very little woody cover aside for the nowdiminished short-woody riparian species. By contrast, the 

confined segments along the main-stem Sprague River have 

more woody vegetation and are the primary sources of large 

wood to the entire river corridor. These trends and attributes 

could point to segment-specific restoration objectives for 

vegetation management.

An important aspect of the Sprague River study area is 

that geomorphic processes are slow. The low slopes, low bedmaterial supply and transport rates, and low stream powers 

all result in naturally slow rates of channel and flood-plain 

evolution. In particular, rates of channel migration, meander 

enlargement (increasing sinuosity), lateral and vertical 

flood‐plain building, and short woody vegetation recovery 

are likely to be slow processes under passive management 

scenarios. Therefore, restoration objectives dependent on 

natural processes may take longer to achieve than for more 

energetic and sediment-rich fluvial systems more typical in 

western North America.
108 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Sediment and flow regimes have changed naturally in the 

Sprague River study area over the last several thousand years. 

These natural dynamics have affected overall flood-plain 

morphology, and rates and processes of channel movement. 

At millennial time scales, the Sprague River fluvial system 

is still responding to the 7,700 cal yr BP eruption of Mount 

Mazama and the resulting loading of the basin with sand- and 

granule-size pumice. Over thousands of years, the effects 

of this sediment will diminish, and, in the absence of a 

similar large-scale disturbance, it is likely that the Sprague 

River fluvial system will revert to a more fine-grained wet 

meadow system as indicated by the character of pre-Mazama 

flood‐plain deposits. At these long time scales, the unconfined 

valley segments (and adjacent main-stem valley fills) are 

likely to continue to aggrade slowly from overbank flood-plain 

deposition and slow channel migration across the flood plain.

At shorter and more relevant time scales for restoration, 

natural flood plain and channel dynamics are likely to affect 

channel and flood-plain conditions. In particular, for the North 

Fork and Lower Sycan valley segments, stratigraphic records 

show many cycles of flood-plain erosion and deposition over 

the last 2000 years, including a current phase of flood-plain 

building over the last 300–600 years. These episodes of 

flood-plain formation and erosion, possibly in conjunction 

with minor channel incision and aggradation, likely represent 

changes in basin sediment and flow conditions, possibly 

resulting from climate variability (Lind, 2009). Additionally, 

the North Fork valley segment has apparently alternated 

between a channelized fluvial corridor and wet meadow fluvial 

system before attaining its current channel and flood‐plain 

morphology. These dynamics represent natural ranges of 

behavior and morphology, and could be incorporated into 

restoration objectives aiming for natural process regimes.

Key Process Regimes

Because natural variability and complexity are ubiquitous 

and incompletely understood for physical and ecologic 

processes and interactions involving rivers, restoration of 

processes may be more likely to achieve ecologically based 

rehabilitation goals than would restoration to predefined end 

points (Wohl and others, 2005; Palmer and others, 2005; 

Bernhardt and Palmer, 2011). For the Sprague River, we 

have identified three key and interrelated process regimes 

historically important to flood-plain and channel form and 

function: (1) channel migration (including avulsions and 

cutoffs), (2) overbank flooding, and (3) vegetation succession 

and disturbance. Maintaining these processes would likely 

result in long-term channel and flood-plain conditions 

consistent with regional ecologic objectives (National 

Research Council, 2004) for much of the study area.

Channel migration builds much of the near-channel 

environment, creates sinuosity, results in bar deposition and 

bank erosion, and creates much of the topography of the 

geomorphic flood plain. Channels abandoned by avulsions 

and cutoffs become side channels and wetlands. Channel 

migration creates suitable substrates and colonization areas 

for aquatic and near-channel flora and fauna. Specific habitat 

features include in-channel pools and riffles, channel‐flanking 

gravel patches and bars, young and low flood-plain surfaces, 

and eroding banks, where down-dropped blocks create 

local and variable habitat conditions. For the Sprague River 

and its major tributaries, channel migration likely is a 

self‐perpetuating process; lateral erosion provides sediment 

that builds bars and inner banks, which in turn steer currents 

against outer banks, promoting lateral erosion.

Sinuosity in the Sprague River study area results 

from the competing processes of meander enlargement 

by lateral channel migration, and channel shortening by 

avulsions and cutoffs that truncate or bypass meander 

loops. The decreased sinuosity since 1940 (fig. 60) resulted 

from avulsions and cutoffs forming at rates faster than 

compensating channel migration, perhaps as a consequence of 

channel confinement by levees, dikes, and other flood-plain 

disturbances. Migration rates also have slowed historically 

(fig. 60), perhaps owing to levee confinement and local bank 

protection. Recent restoration projects have aimed to restore 

sinuosity by plugging cutoffs and avulsion channels, and 

by placing channels back in former meander loops, locally 

buttressed by various forms of armoring (fig. 23). Instead 

of attempting to reverse specific cutoffs, however, a more 

sustainable long-term process-based approach would be to 

allow sinuosity to increase at broad scales by (1) allowing 

lateral channel migration in all practical locations; and 

(2) limiting disturbances promoting avulsions and cutoffs, 

such as confinement, ditches, and trails. Under such natural 

equilibrium conditions, cutoffs and avulsions will persist, 

forming side channels and flood-plain wetlands and thereby 

increasing habitat diversity, but continued lateral channel 

migration will maintain sinuosity.

Overbank flooding also is an important process in 

the Sprague River study area, and is a key component of 

hydrologic connectivity within the fluvial system (Kondolf 

and others, 2006). Overbank flooding deposits suspended 

sediment, augments flood-plain soils, incrementally builds 

flood-plain surfaces, and promotes lateral exchanges of 

nutrients, flora, and fauna (Jenkins and Boulton, 2003). 

Hydraulic consequences include attenuation of flood peaks 

and lowering of in-channel flow velocities during floods 

(possibly limiting channel widening and incision). Overbank 

flow is required for chutes and avulsions, the primary 

mechanisms by which meanders are cut off and abandoned, 

leading to side- and off-channel aquatic habitats.

For most of its length, the Sprague River has retained 

some lateral and longitudinal connectivity. Dams and 

diversions have been removed from the main-stem Sprague 

River, leaving only a few such structures in the South Fork 

and North Fork valley segments. Overbank flooding is still 

common, as evidenced by the extensive flood-plain inundation 

during the 2006 high flows, but has been limited in some 

reaches by levees, dikes, and railroad grades, and in the 

South Fork valley segment by channel incision. Because of 
Implications for Restoration and Monitoring 109

the general absence of significant incision for much of the 

study area, overbank flooding is still an effective process. 

This condition enhances the potential for restoration of lateral 

connectivity by passive management approaches, including 

strategic levee removal and breaching.

Vegetation succession and disturbance processes 

interact to create the mosaic of riparian and flood-plain 

vegetation. Vegetation is important in affecting bank stability 

and geometry, stream shading (and temperature), bank and 

flood-plain nutrient conditions, in-stream wood loading, and 

resistance of channel edges and flood-plain surfaces to erosion 

and channel formation. Although significant trends are evident 

in cover type in the study area (table 13; figs. 61–66), probably 

representing changes in types of intensity of disturbance, the 

basic vegetation types and distributions are similar to the 

early historical descriptions. Therefore, for most of the study 

area, the likelihood of attaining riparian vegetation patterns 

broadly similar to historical conditions is high if the rates 

and types of disturbance processes revert to more natural 

conditions, particularly for the more dynamic near-channel 

environments. The greater proportion of increasing seral 

stages in the 1968–2000 period compared to the 1940–1968 

period (fig. 64) indicates that vegetation can respond at 

decadal time scales to changes in human disturbance factors. 

Less evident is whether active vegetation management 

strategies such as planting are effective in restoring vegetation 

conditions. Such efforts are particularly challenging in 

dynamic near-channel environments, where channel migration, 

flooding, predation, erosion, and deposition can adversely 

affect planted vegetation, although low migration rates in 

some reaches may enhance survival. Many recent restoration 

projects have involved efforts to establish shrubs and trees, 

but these have been mostly unsuccessful, possibly because 

of high water tables (Rasmussen, 2011). As for other key 

flood-plain and channel processes, the main controlling factors 

such as sediment transport, channel migration, and regular 

flood-plain inundation still are present for most of the Sprague 

River study area. Therefore, intense manipulation or active 

vegetation management may not be necessary to achieve 

ecologically based vegetation objectives. An uncertain factor, 

however, is the presence of reed canarygrass, now extensive 

in several valley segments in the basin. This nonnative species 

likely will affect restoration efforts by decreasing potential for 

shrub germination and displacing native herbaceous species, 

particularly in areas of reduced grazing intensity.

For most of the study area, the processes identified as 

important for creating and maintaining ecologically beneficial 

channel and flood-plain conditions still function, although 

some at altered levels. Therefore, substantial flood-plain and 

channel manipulation is not required to meet most ecologically 

based objectives at the broad scales of the geomorphic 

flood plain and valley segments. Removal of levees and 

dikes, which locally have confined the channel, might be a 

widespread active management approach to enhance lateral 

connectivity and reduce incision potential.

For the South Fork valley segment, however, the key 

processes and conditions have been altered substantially by 

diversions, channelization, incision, levee construction, and 

vegetation manipulation and removal. Therefore, reversing 

the geomorphic and ecologic changes of the last 100 years is 

unlikely without substantial manipulation of the channel and 

flood plain. Even with alterations so that channel migration, 

overbank flooding, and vegetation secession can proceed, the 

naturally slow rates of these processes for the Sprague River 

likely will require decades or centuries for reestablishment 

of the conditions of the early 1900s in the South Fork valley 

segment: wet meadows interspersed with luxuriantly vegetated 

riparian corridors.

Restoration Objectives

The results of this study provide a means for establishing 

measurable broadscale objectives for important geomorphic 

and ecologic processes. This perspective is based on the 

premise that maintaining and enhancing the key process 

regimes will broadly enhance ecological conditions in the 

Sprague River Basin. Therefore, restoration objectives follow 

from the key process regimes identified here. This approach 

contrasts with objectives focused on site-specific channel and 

flood-plain conditions, although this might be appropriate for 

key habitats at special locations.

One objective could be to maintain, allow, or restore 

natural channel migration processes, including cutoffs and 

avulsions, which can be measured in terms of sinuosity, slope, 

width, migration rates, and bar area. Sinuosity integrates many 

of these factors, but channel migration rates are an index 

of channel dynamics, which also underlie many important 

channel and flood-plain attributes.

A second objective would focus on maintaining and 

enhancing frequency and extent of overbank flooding and 

lateral connectivity. In unincised and unconstrained valley 

segments, a logical objective would be to maintain the present 

frequency and extent of flooding. Where the channel is 

incised, an increase in the frequency and extent of flooding 

would indicate a tendency toward more natural conditions. 

In these areas, locally increasing channel and flood-plain 

altitudes indicate channel and flood-plain aggradation, 

consistent with overbank flooding and exchange of sediment 

and nutrients between the channel and flood plain. Similarly, a 

decreasing vertical difference between channel and flood‐plain 

altitude indicates more frequent inundation for a given flood 

regime. In sections where flooding has been limited by 

structures such as levees or railroad grades, decreasing the 

extent of the geomorphic flood plain separated from channel 

and flood-plain processes by levees, dikes, and other structures 

would lead to more natural conditions and increase the extent 

of flooding. Along these lines, dike and levee removal or 

breaching is one of the very few restoration activities requiring 

active flood-plain manipulation.
110 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

Broadscale vegetation objectives derived from this 

study could emphasize the distribution and extent of specific 

cover types, transitions among cover types, or more general 

successional or disturbance trends. Because historical and 

present vegetation conditions vary spatially, such objectives 

likely could be most usefully established if designed for 

individual valley segments and separately for near-channel and 

flood-plain areas. These smaller areas also would likely be the 

best candidates for objectives pertaining to individual species, 

as described more fully by Rasmussen (2011).

Whereas all of these types of objectives are relevant to 

important channel and flood-plain processes and conditions 

in the Sprague River study area, they may not directly 

signal trends in the overall regional objectives of restoring 

endangered fish species and improving water quality (Boyd 

and others, 2002; National Research Council, 2004; National 

Resource Conservation Service, 2009). Nevertheless, trends in 

these indicators almost certainly will relate to overall ecologic 

integrity in the basin, although such attributes may be difficult 

to characterize quantitatively.

Monitoring Approaches

Quantification of these objectives and their attainment 

could derive from the types of analyses described here that 

provide information on decadal-scale trends. Repeat mapping 

of plan-view channel morphology, channel migration rates, 

and vegetation conditions from new aerial photographs, using 

the protocols of this study, would allow for direct comparison 

and measurements of key features used to measure the 

success of restoration objectives or to document other changes 

following future disturbances, such as large floods (fig. 60).

New and repeated lidar acquisitions also would 

facilitate efficient broadscale monitoring, especially if the 

coverage and quality meet that of the 2004 lidar (Watershed 

Sciences, Inc., 2005). Topographic analyses of channel 

and flood-plain surfaces, when compared with previous 

lidar altitude data, would allow for monitoring channel and 

flood-plain aggradation and erosion, thereby effectively 

tracking connectivity between the channel and flood plain. 

Additionally, by enabling detection of changes in bar and 

flood-plain sediment volumes, valley-segment and basin‐scale 

sediment budgets could be determined if coupled with 

long-term sediment measurement programs (for example, 

Gran and others, 2009). Techniques also are being developed 

for quantitative characterization of vegetation types and 

density from lidar altitude data (Forzieri and others, 2010; 

Pflugmacher and others, 2011), which could enable more 

quantitative measurement of vegetation trends.

Consistent with all aspects of this study, these types of 

monitoring approaches are most applicable to broad temporal 

and spatial scales. Such broadscale monitoring is not likely 

to discern immediate effects of site-specific restoration 

activities, but should be able to document trends resulting 

from the cumulative effects of activities at the scale of 

valley segments or the entire study area. Similarly, because 

geomorphic processes are slow in the Sprague River Basin, 

such monitoring would be conducted most efficiently at 

decadal time scales, thereby allowing detection of trends and 

conditions as they respond to flood-plain management actions 

in reaction to a range of hydrologic and geomorphic events 

over several years. Additionally, monitoring of the effects of 

significant flows, such as the monitoring conducted in this 

analysis of the 2006 high flows, would enable continued 

assessment of the efficacy of key channel and flood-plain 

processes during geomorphically effective events.

Summary and Significant Findings

The Sprague River Basin encompasses 4,167 square 

kilometers of south-central Oregon and is a primary tributary 

(via the lower Williamson River) of Upper Klamath Lake. 

The main-stem Sprague River, as well as the lower reaches 

of the North Fork Sprague River, South Fork Sprague River, 

and the Sycan River, meander through broad alluvial valleys 

historically supporting agriculture and livestock grazing. 

National and regional interest in restoring Klamath Basin 

ecosystem conditions and processes has motivated several 

restoration strategies and projects in the Sprague River Basin 

to improve aquatic, riparian, and upland habitat conditions. 

This study—jointly conducted by the U.S. Geological Survey 

and University of Oregon, and in cooperation with the 

U.S. Fish and Wildlife Service Klamath Basin Ecosystem 

Restoration Office and the Hatfield Restoration Program—

provides basic information on channel and flood-plain 

processes and historical trends to help management and 

regulatory agencies evaluate restoration proposals and to guide 

effective restoration and monitoring strategies for the Sprague 

River and its primary tributaries.

The study area covered the lower, alluvial segments 

of the Sprague River system, including the lower parts of 

the Sycan River, North Fork Sprague River, South Fork 

Sprague River, and the entire main-stem Sprague River 

between the confluence of the North and South Forks and its 

confluence with the Williamson River at Chiloquin, Oregon. 

The study used many methods, including mapping and 

stratigraphic analysis of flood-plain deposits and flanking 

features; evaluation of historical records and observations; 

systematic mapping and analysis of flood-plain and channel 

characteristics (including morphologic and vegetation 

conditions) from historical surveys, maps, and aerial 

photographs; and a 2006 survey of depositional features left 

by early 2006 high flows.

Analyses focused primarily on the channel and flood 

plain within an area defined as the “geomorphic flood plain.” 

The geomorphic flood plain, covering 78 square kilometers, 

is the low-lying and relatively flat area flanking the main 

channels and affected by main-stem fluvial processes of 

erosion, deposition, channel migration, and flood inundation 
Summary and Significant Findings 111

during the Holocene epoch. The geomorphic flood plain 

was subdivided into 13 valley segments of distinct fluvial 

and biologic environments on the basis of valley form and 

major tributary junctions: nine segments that encompass the 

136.1 kilometers of main-stem Sprague River, two segments 

for the lower Sycan River, and one segment for each part of 

the South Fork Sprague and North Fork Sprague Rivers within 

the study area.

Segment characteristics range from low-gradient reaches 

with expansive flood plains to steep and narrow canyons. 

The wide flood-plain valley segments are broadly similar; 

most segments contain a sinuous, low-gradient channel that 

migrates slowly across the valley bottom. The narrow valley 

segments include the steep, boulder-and-cobble-bed reaches 

at downstream and upstream ends of the study area as well 

as other confined valley segments that have similar gradients 

and substrates as adjacent unconfined valley segments, but 

much lower sinuosities. Although the geologic setting of the 

expansive South Fork valley segment resulted in historical 

conditions of sinuous and poorly defined channels and 

wet meadows, flanking levees now narrowly confine the 

channelized South Fork Sprague River for much of its length.

The fine-grained extrusive volcanic rocks and lacustrine 

sediment that constitute most of the Sprague River Basin do 

not produce much sand and gravel bed material. In the absence 

of substantial bed material prior to the Mazama eruption of 

7,700 cal yr BP, the main rivers of the study area apparently 

were flanked by wetlands and low flood plains, and migration 

rates probably were low. The eruption, however, covered 

much of the northern basin with sand- and granule-size 

pumice clasts, transforming the fluvial system by increasing 

bed-material transport and promoting bar formation and 

channel migration, particularly for the Sycan and North Fork 

Sprague Rivers, and the Sprague River downstream of the 

Sycan River confluence. The South Fork Sprague River, which 

had much less Mazama pumice deposited in its watershed, 

remained a wet-meadow fluvial system until historical 

channelization and diking.

Despite the pumiceous sand input and the general 

low gradients of the main channels within the study area, 

the present overall bed-material sediment regime is supply 

limited, meaning the transport capacity exceeds the supply 

of bed material. This is evident by the discontinuous alluvial 

cover of the channel bottom, the sparse bars in and flanking 

the channel, and the overall slow channel migration rates 

compared to many western North American rivers.

Although channel migration rates are low, lateral 

channel movement is an important process for maintaining 

channel and flood-plain materials, form, and function. Lateral 

migration forms and expands meanders, which increases 

sinuosity. Countering meander enlargement are avulsions and 

meander cutoffs, including chute and neck cutoffs, which 

decrease sinuosity. The decrease in sinuosity since 1940 

for nearly all the unconfined reaches resulted partly from 

decreased migration rates, but mostly from several cutoffs and 

avulsions formed mainly between 1940 and 1975. The greater 

frequency of avulsions and meander cutoffs possibly resulted 

from (1) flood-plain confinement by levees, dikes, roads, and 

railroads leading to deeper and faster overbank flow, thereby 

promoting erosion of new flood-plain channels; and (2) 

flood-plain disturbances such as trails, ditches, and vegetation 

manipulation or eradication that locally concentrated overbank 

flow and decreased surface resistance to channel erosion. 

The Sprague River channel generally is not incised to the 

extent that floods fail to inundate the flood plain. The floods 

of 2006 left overbank deposits on flood-plain surfaces along 

the entirety of the main-stem Sprague, lower Sycan, and lower 

North Fork Sprague Rivers, consistent with the stratigraphic 

evidence of substantial flood-plain deposition and accretion 

during the last several hundred years. By contrast, as much as 

1.6 meters of historical incision is evident in the upstream part 

of the study area, chiefly in the South Fork valley segment, 

but possibly extending several kilometers downstream of the 

confluence of the North Fork Sprague River with the South 

Fork Sprague River.

A general absence of channel incision for much of 

the study area is consistent with little evidence of channel 

widening. Neither analyses using General Land Office surveys 

nor those of historical aerial photographs indicate overall 

widening or narrowing trends in channel width, although 

individual valley segments have had channels narrow 

or widen. 

The Sycan River is unique because of the great influence 

of the Mazama eruption on its catchment. The Sycan flood, 

shortly after the eruption, formed a broad deposit of loose 

and coarse pumiceous sand, now incised by the channel and 

younger flood plains. Episodes of watershed-scale enhanced 

sediment supply after the flood resulted in construction of 

sandy flood plains flanking the channel, which continue 

to be susceptible to lateral erosion. Because of the higher 

bed-material sediment supply, the Lower Sycan valley 

segment has abundant bars, wide channels, and high migration 

rates relative to other valley segments.

The South Fork Sprague River was affected little by the 

Mazama eruption; consequently, the historical condition of its 

fluvial systems probably was much different from that of the 

Sycan River and, to a lesser extent, the North Fork Sprague 

River. At the time of the General Land Office surveys in 

the 1860s and for thousands of years prior, the South Fork 

Sprague River probably was a poorly defined, stable (and 

locally multithreaded) channel and wet-meadow complex 

fringed by willows, seasonally flooding and slowly aggrading 

the expansive valley bottom by depositing sediment. 

Beaver likely contributed to wet-meadow flood plain and 

channel conditions. 

Human actions, however, locally have affected Sprague 

River channel and flood-plain conditions since the first 

European settlement in the 1860s. Most evident are the 
112 Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon

contemporaneous and persistent effects of channelization 

and flood-plain confinement by levees, roads, and the former 

Oregon, California, and Eastern Railroad alignment, dating 

mainly from the 1920s through the 1970s. Channelization 

before 1940 transformed the South Fork Sprague River into 

an incised channel of low sinuosity. Less evident are the 

effects of levees, but flood-plain confinement probably has 

increased the frequency of avulsions and cutoffs, resulting 

in reduced sinuosity and overall greater channel slopes since 

1940. Riparian grazing and channel and bank trampling by 

cattle locally have affected bank and channel conditions, 

as have local accumulations of dumped rock at fords and 

former bridge crossings. Channel remeandering, mostly 

since 2000, locally has resulted in the filling of chute cutoffs, 

avulsions, and the placement of the primary channel back in 

its historical positions.

The South Fork Sprague River, compared to other 

valley segments in the study area, has been the most clearly 

transformed since first historical observations. The present 

channel is incised, straightened, and separated from the flood 

plain by levees for much of its alluvial corridor. Significant 

parts of the flood plain have been drained and leveled. Many 

in-channel structures currently divert flow into irrigation 

channel networks. This valley segment also appears to be a 

major source of suspended sediment to the Sprague River 

fluvial system. 

Despite these broadscale and local effects of human 

disturbances, many of the fundamental physical processes 

that have shaped the Sprague River fluvial systems over the 

last several thousand years still function. Most importantly, 

upstream impoundments do not significantly interrupt flow 

or sediment. Consequently, overall bed-material transport 

conditions are similar to historical conditions, including 

sediment supply and water flow. Lateral connectivity is mostly 

also preserved because of the absence of system-wide channel 

incision, which can limit restoration opportunities. Areas of 

the fluvial system that have been incised, particularly the 

South Fork valley segment, are in the upstream part of the 

study area, limiting the likelihood that geomorphic effects 

(aside from changes in flow and sediment transport) will 

migrate to other parts of the study area. These factors suggest 

that restoration of many of the native physical conditions 

and processes is possible for much of the Sprague River 

study area without substantial physical manipulation of 

current conditions.

General spatial patterns of vegetation in the Sprague 

River flood plain are influenced by broadscale basin 

characteristics. Tall woody species prefer narrow, confined, 

and shaded flood plains. Wide flood plains mostly are 

covered with herbaceous plants, but past and present channel 

areas locally are flanked by short woody vegetation. These 

predominant attributes have persisted since the first historical 

observations in the 1800s, chiefly because the areas within the 

study area have remained mostly pastoral, without substantial 

urbanization, timber harvest (within the flood plain) or 

basin-scale changes in flow and sediment regimes. At finer 

scales, however, near-channel areas are more dynamic than 

the flood plain as a whole (representing the important roles 

of fluvial disturbance and succession in creating riparian 

vegetation communities), perhaps exacerbated by predation 

and concentrated grazing.

Some individual vegetation cover types, however, show 

clear trends. The most evident is the loss of short woody 

vegetation: only one-half the near-channel area covered by 

short woody vegetation in 1940 was covered similarly in 

2000. The loss of short woody vegetation to less-complex, 

early seral (successional) stages was the chief change among 

many indicating vegetation disturbance and loss of structural 

complexity, particularly before 1968. Since 1968, changes 

have been smaller and more evenly distributed between 

increasing and decreasing seral stages.

Vegetation changes have resulted from a combination of 

geomorphic processes and trends, vegetation succession, direct 

vegetation manipulation, and broadscale land use. Transitions 

among the bare and water cover types chiefly are the result 

of decreased sinuosity and large floods. Woody vegetation 

removal in the 1950s and 1960s and continuing grazing and 

trampling by livestock probably are the main reasons for the 

decrease in short woody vegetation from the locally dense 

riparian corridors of willows and other riparian shrubs noted 

in the early 20th century. Since 1968, vegetation succession 

locally has increased seral stage and habitat complexity, partly 

compensating for earlier losses.

The findings regarding physical processes, historical 

conditions, and vegetation patterns and changes have 

implications for restoration and monitoring of the Sprague 

River Basin. Most importantly, many physical processes and 

conditions responsible for channel and flood-plain formation 

still function. This contrasts with many western rivers, 

in which dams and diversions have substantially affected 

sediment and water fluxes, and where channel incision has 

limited interaction between channels and flood plains. Because 

overall basin conditions are not markedly altered in the 

Sprague River Basin, historical conditions provide a plausible 

reference frame for restoration objectives.

For the broad area of the Sprague River study area in 

which flood flows regularly inundate the flood plain, natural 

processes may be sufficient under proper conditions to reverse 

historical trends of decreasing sinuosity and loss of short 

woody vegetation cover. However, for the alluvial section 

of the South Fork Sprague River, historical and ongoing 

channel incision and flood-plain erosion will inhibit reversal 

of historical trends and likely will continue to be a source 

of suspended sediment load to the river system. For this 

reach, incision likely will continue as long as the channel is 

fully constrained by levees and dikes and until knickzones 

progress to locations where channel substrate resists continued 

downcutting. Although changes may slow in the South Fork 
References Cited 113

Sprague River valley segment under present conditions, 

historical trends are not likely to reverse until it attains a more 

natural channel and flood-plain geometry and the channel 

aggrades to the extent that overbank flow becomes common.

For most of the Sprague River flood plain, the greatest 

likelihood of restoration to pre-development conditions 

would result from a strategy emphasizing natural processes 

for the entire geomorphic flood plain. A less conservative 

strategy could reverse historical changes by focusing on 

a narrower region about the channel, where processes are 

most dynamic and the coupling between channel and flood 

plain is strongest. Such a strategy, however, has some risk 

because avulsions and cutoffs, which create ecologically 

important flood-plain features, extend to areas beyond the 

near-channel environment.

An important aspect of the Sprague River study area 

relative to restoration is that geomorphic processes are slow. 

The low slopes, low bed-material supply and transport rates, 

and low stream powers all result in naturally slow rates of 

channel and flood-plain evolution. In particular, rates of 

channel migration, meander enlargement, lateral and vertical 

flood-plain building, and short woody vegetation recovery are 

likely to require decades or longer under passive management 

scenarios. Therefore, restoration objectives dependent on 

natural processes may take more time to achieve in the 

Sprague River Basin than in more energetic and sediment-rich 

fluvial systems more typical in western North America.

The findings from this study indicate that the following 

activities can facilitate natural geomorphic and vegetation 

processes important to ecological conditions in the Sprague 

River Basin:

1. Maintain or restore natural channel migration 

processes, including channel avulsions and cutoffs. 

Sinuosity integrates many of these factors, but channel 

migration rates are an index of channel dynamics, 

which also underlie many important channel and floodplain attributes.

2. Maintain and enhance the frequency and extent of 

overbank flooding and lateral connectivity between 

channels and flood plains. In unincised and unconstrained 

valley segments, a logical objective would be to maintain 

the present frequency and extent of flooding. In sections 

where flooding has been limited by incision or structures 

such as levees or railroad grades, decreasing the extent 

of the geomorphic flood plain separated from channel 

and flood-plain processes by levees, dikes, and other 

structures would increase the frequency and extent of 

flooding and enhance flood-plain deposition.

3. Promote vegetation succession and disturbance processes 

conducive to reversing historical losses of short woody 

vegetation cover types. Additional vegetation objectives 

could focus on distribution and extent of specific cover 

types, transitions among cover types, or more general 

successional or disturbance trends. Because historical 

and present vegetation conditions vary spatially, such 

objectives likely could be established most effectively 

if they are designed for individual valley segments and 

separately for near-channel and flood-plain areas.

Monitoring the outcomes of these activities could 

rely on some of the methods used in this study. Repeat 

mapping of channel and flood-plain conditions from new 

aerial photographs would allow for direct comparison and 

measurements of plan-view channel morphology, channel 

migration rates, and vegetation conditions. Additionally, 

monitoring of the effects of significant flows, such as the 

analysis of the 2006 high flows, would enable continued 

assessment of key channel and flood-plain processes during 

geomorphically effective events. Such broadscale monitoring 

is not likely to discern immediate effects of site-specific 

restoration activities, but should be able to document trends 

resulting from the cumulative effects of activities at the scale 

of valley segments or the entire study area.

Acknowledgments

Sue Mattenberger of the U.S. Fish and Wildlife Service 

and Larry Dunsmoor of the Klamath Tribes facilitated this 

project. Graham Mathews and Associates shared information 

on their ongoing channel geomorphology and sediment 

transport analyses and assisted in acquisition of the 1940 

aerial photographs. Terry and Jessi Shields (and their family) 

provided significant logistical support for our field work. 

Access to field sites was provided graciously by many 

property owners, including Scott Phillips; Rod Kornnelson; 

John and Lil Kronenberger; Dean and Chloe Walker; Becky 

and Taylor Hyde; Ken and Dianne Busher; Jim Hadyn-Meyer; 

Jim Flinn; Greg Bulkley; Bob and Roberta Valladao; Ken 

Willard; Andrea, Clifford, and Mary Rabe; John and Barbara 

Fugatt; Mike Lelmorini; Dan and Kathy Ridgeway; Greg 

Harris; and Jim Wayne. We benefited from discussions and 

assistance from Larry Dunsmoor, Sue Mattenberger, Greg 

Harris, Michael Hughes, Faith Fitzpatrick, Paul Pedone, 

Marshall Gannett, Alex Bourdeau, and Dave Sherrod. 

Assistance with analysis and report preparation was provided 

by Keith Jackson, Tana Haluska, Joseph Mangano, and John 

Williams. Chris Carlson, Matt Derrick, Benn Hackett, John 

Lind, Jessica Phelps, and Jason Stuckey assisted in the field.

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Appendixes 121

Appendixes

Appendixes are Microsoft© Excel files and are available for download at http://pubs.usgs.gov/sir/2014/5223.

Appendix A. Locations of Stratigraphic Analysis, Sprague River Study Area, Oregon

Appendix B. Radiocarbon Analyses, Sprague River Study Area, Oregon

Appendix C. Volcanic Glass Compositions of Tephra, Sprague River Study Area, Oregon 

Appendix D. Cesium-137 Content, Sprague River Study Area, Oregon

Appendix E. Geomorphic Map Units, Sprague River Study Area, Oregon

Appendix F. Comparison of General Land Office Section-Line Measurements of River Width with

Width from 2000 Aerial Photographs, Sprague River Study Area, Oregon

Appendix G. Survey Sites of Effects of 2006 High Flows, Sprague River Study Area, Oregon

Appendix H. Vegetation Transitions in the Geomorphic Flood Plain and Near-Channel Areas for 

1940–1968 and 1968–2000, Sprague River Study Area, Oregon

Publishing support provided by the U.S. Geological Survey

 Science 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
O’Connor and others—Geomorphology and Flood-Plain Vegetation of the Sprague and Lower Sycan Rivers, Klamath Basin, Oregon—Scientific Investigations Report 2014–5223

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20145223