The controls on and evolution of channel morphology of the ... · The controls on and evolution of channel morphology of the Sacramento River: A case study of River Miles 201-185

The controls on and evolution of channel morphology of the SacramentoRiver: A case study of River Miles 201-185

Eric Larsen, Emily Anderson, Ellen Avery, Krishna DoleGeology Department

University of CaliforniaDavis, California

Report to the Nature Conservancy

Table of Contents

1.0 Introduction ..............................................................................

2.0 Background ..............................................................................

2.1 Geologic Setting ....................................................................................................... 1

2.2 Hydrologic Setting.................................................................................................... 8

2.3 Environmental Setting .............................................................................................. 9

2.4 Historic Changes in Channel Location ................................................................... 10

River Miles 201-198 (Zone 1) .................................................................................. 10

River Miles 198-193 (Zone 2) .................................................................................. 11

River Miles 193-189 (Zone 3) .................................................................................. 14

River Miles 189-185 (Zone 4) .................................................................................. 15

3.0 Methodology ..............................................................................

3.1 Historical Years of Record ..................................................................................... 18

3.2 Modeling of Future Meander Migration................................................................. 21

Hydraulic Modeling of Flow .................................................................................... 21

Model Calibration and Validation ............................................................................ 22

4.0 Results ...................................................................................

4.1 Historical Years of Record ..................................................................................... 25

Wavelength ............................................................................................................... 25

Sinuosity ................................................................................................................... 28

Area Reworked and Rate of Migration..................................................................... 32

4.2 Modeling of Future Meander Migration................................................................. 36

Wavelength (Distance Between Inflection Points) ................................................... 41

Sinuosity ................................................................................................................... 44

Area Reworked and Rate of Migration..................................................................... 47

5.0 References................................................................................

TNC, Sacramento River, California December 2002Chico Landing Study ReachMeander Migration Report

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The controls on and evolution of channel morphology ofthe Sacramento River: A case study of River Miles 201-185

1.0 Introduction

River morphology – as expressed in the planform shape, the cross-sectional shape, andlongitudinal profile – is the result of a complex interaction of the geologic setting,hydraulic factors, and environmental factors. As environmental managers areincreasingly interested in managing river morphology in new ways that may enhanceecological functions, an understanding of what controls channel shape is critical.Intelligent decisions about what areas to manage, and how to manage them, depend on anunderstanding of how the controlling factors affect channel morphology and function.

The Sacramento River is an example of a river where the channel morphology isdetermined by the interaction of geologic, hydraulic, and environmental factors. In thispaper we use a selected study reach of 16 river miles (RM) (26 kilometers) as a casestudy to describe how these factors may have influenced historical channelcharacteristics, and how these factors can be used to inform future river managementdecisions. We examine the relative influence of each of these factors on channelmorphology and meander migration pattern, and the interaction between them. Weexamine historical characteristics of the study reach, and predict future planform shapeand location of the study reach under different rip-rap management scenarios.

2.0 Background

2.1 Geologic Setting

The Sacramento River flows south through the Sacramento Valley over sedimentaryrocks and recent alluvium. The Sacramento Valley is 96 kilometers (km) wide and418 km long and is a structurally controlled basin between the Sierra Nevada Mountainsand the Coast Range (Harwood and Helley 1987). The total drainage area of the river is6.8x104 square kilometers (km2), more than half of the total drainage area of the SanFrancisco Bay (Porterfield 1980). The location of the study reach is shown in Figure 1.

The Sacramento Valley is located between the Sierra Nevada and the Coast Ranges ofCalifornia. There are four major tectonic units in the Sacramento River watershed(Figure 2). The Coast Range, located on the west side of the river, is divided into theGreat Valley sedimentary sequence on the east and the Franciscan formation on the west.The Klamath Mountains are an island arc terrane composed of marine sediments andgranitic plutons, and are to the north and northwest of the Sacramento River. The


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southern Cascades and northern Sierran rocks are located to the west, and are areas ofPliocene-Recent extrusive volcanic activity. The valley that the river flows directlythrough is comprised of Pliocene-Pleistocene alluvium and fluvial deposits. Thecomposition of sediments that are deposited into the Sacramento River

Figure 1. Location of the Sacramento River and the study reach.

from creeks is directly related to these tectonic units. For example, the bedload of PineCreek, which meets the Sacramento River at RM 196 and drains from the east, is 89%volcanic clasts (Robertson 1987).

The primary geologic units in the study reach are the Pleistocene-age fluvial (terrace)deposits of the Riverbank and Modesto Formations. These terrace deposits typicallyconsist of 1-3 meters (m) of dark gray to red fine sand and silt overlying 1.5 - 2 m ofpoorly sorted gravel (California Department of Water Resources [DWR] 1994). TheRiverbank Formation is light red in color and consists of gravel, sand, silt and clay.There is soil formation in this unit that displays a B-horizon and local hardpan (DWR1994). The Modesto formation is younger than the Riverbank formation, and containsthe youngest terrace with a pedogenic B-horizon (DWR 1994). This unit is usually lessthan 2.5 m thick and is composed of gravel, sand, silt and clay (DWR 1994). TheRiverbank and Modesto formations are generally erosion resistant, and when exposed onbends, these formations can inhibit bank erosion and lateral migration (Fischer 1994).Additionally, when these units are exposed on the downstream limb of a bend the


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downstream migration is limited. In the study reach, the west side of the river fromRM 194 is constrained by the Modesto formation.

There are paleochannel deposits located along the eastern margin of the SacramentoRiver from RM 226 (Thomes Creek) to RM 144 (Colusa) (Robertson 1987). Thepaleochannels are braided with multiple branches and islands, suggesting a higherbedload, a higher width-to-depth ratio, and higher discharges than the present day


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Figure 2. Northern California (Sacramento River watershed) with general structural regimes andtwo tectonic domains defined by Harwood and Helley (1987) within the Sacramento Valley region.

Sacramento River (Robertson 1987). Based on buried soils, the age of the channels isbetween 150,000 and 450,000 years, equivalent in age to the Riverbank formation(Robertson 1987). There is a thin layer of silt and clay over the paleochannels, which hasresulted in the paleochannels being mapped incorrectly as Modesto Formation in the past(Helley and Harwood 1985). The bedload of the paleochannels was significantly coarserthan that of the present day Sacramento River and consisted primarily of volcanic rocks,most likely from a Cascade Range source area (Robertson 1987). This could be due to aperiod of high volcanic activity in the Lassen area. These paleochannels are well-indurated and erosion resistant, and the western edge of the paleochannel is the easternedge of the historic meander belt of the present Sacramento River (Robertson 1987). Thestudy reach is bound on the eastern side by paleochannel deposits from RM 193 to RM185.


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The structural patterns of late Cenezoic deformation in the Sacramento Valley differsfrom the transpressional regime in the Coast Ranges to the west and the extensionaldeformation of the Basin and Range physiographic province to the east. The regionalstress field in the valley has a maximum horizontal component of stress oriented east-west (Harwood and Helley 1987). In the last 5.2 million years compressive deformationhas progressed northward so that structures in the northern valley are younger thanstructures in the south. Harwood and Helley (1987) divided the valley into structuraldomains, and the ones of interest to this study are the Corning and the Chico domains,which are labeled in Figure 2.

The Chico monocline is the dominant structure of the Chico domain (Figure 3). TheChico monocline and associated faults are the result of the uplift of the Sierra Nevada andfracturing along the major controlling fault (Harwood and Helley 1987). The Chicomonocline trends northwest and bounds the northeast side of the Sacramento Valleybetween Chico and Red Bluff. The basement rocks beneath the monocline show adisplacement of 350 m and there is evidence that the monocline is still active (Harwoodand Helley 1987).

West of the Chico domain is the Corning domain, with structures oriented northwest tonorth (Harwood and Helley 1987). The Willows fault and the Corning fault are withinthis domain, and they are close to parallel in orientation to the Chico monocline. TheWillows fault is an active northwest trending fault that crosses the Sacramento Rivernorth of Colusa, with uplift to the east (Harwood and Helley 1987). The faults describedabove dominate the structure of the northern Sacramento Valley, however, the course andbehavior of the Sacramento River is controlled by the smaller structures of the LosMolinos and Glenn synclines and the Corning Domes (Harwood and Helley 1987).

Once the Sacramento River flows down the Los Molinos and Glenn syncline axes, thechannel and floodplain of the river widens. For this particular study reach, RM 201-185,the river flows near the axis of the Glenn syncline. Upon entering the Glenn syncline atRM 205, the width of the channel and floodplain increases. The river is narrow fromRM 200 to RM 197 as it crosses the axis of the syncline. The channel and floodplainwidens again after RM 197, and the river parallels the axis of the Glenn syncline fromRM 197 to RM 193. The channel crosses the axis of the syncline at RM 191, and thengenerally flows along the axis of the syncline until RM 180.

There are two independent lines of evidence that supports the theory that these subsurfacestructures are still active: (1) a study of sediment deformation that shows recentmovement on these controlling structural features (Helley and Jaworowski 1985), and (2)a National Geodetic Survey line that crosses the Sacramento River and the GlennSyncline. Helley and Jaworowski (1985) studied the Red Bluff pediment (a gravel-covered erosion surface formed 450,000 years ago) and found that there was deformationof the erosional surface at the Corning Domes. They also mapped contours in the


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Modesto Formation (14,000-26,000 years old) that show depressions associated with theGlenn syncline.


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Figure 3. Structural map of the Sacramento Valley from Red Bluff to Colusa (from Harwood andHelley, 1982, after Fischer1994). The locations of flood relief structures and the National GeodeticSurvey lines are indicated.


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More recent evidence of active deformation in the Sacramento Valley can be shown bythe National Geodetic Survey (NGS) data (WET 1988). There is a line from Red Bluff toRoseville, California, that runs just to the east of the Sacramento River and crosses theGlenn Syncline. This line was surveyed in 1919 and in 1949, revealing subsidence to thesouth during this time interval. Additionally, there is a distinct disruption in the generaltrend where the survey line crosses the Glenn syncline, indicating a relative downwarpingacross the syncline (WET 1988).

2.2 Hydrologic Setting

The major man-made structures that have affected the Sacramento River’s hydrology inthe last 60 years are the Shasta Dam and flood control structures installed as part of thefederal flood control project of the Sacramento River. The hydrologic history of theSacramento River within the study reach can be quantitatively assessed by accessingUS Geological Survey (USGS) river gauge data. The USGS Hamilton City gauge(Number 11383800) is located at approximately RM 199, near the top of the study reach.Daily flows were recorded from 21 April 1945 through 30 September 1980. Figure 4shows a plot of annual peak flows.

Annual Peak Flow, 1945-1980Hamilton City Gauge, USGS No. 113838000

0.E+00

2.E+04

4.E+04

6.E+04

8.E+04

1.E+05

1.E+05

1.E+05

2.E+05

1945 1950 1955 1960 1965 1970 1975 1980

Water Year

Flow

(cfs

)

Figure 4. Peak annual flow, USGS gage no. 11383800, Hamilton City gage.

A return-interval analysis is performed for the study reach using Hamilton City gaugedata from the USGS website (http://waterdata.usgs.gov/nwis/discharge/?site_no=11383800).The two-year return flow is calculated to be 79,500 cubic feet per second (cfs)(Appendix A). Discharge of 80,000 cfs is used in the meander migration modeling.


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Three major effects on discharge since the construction of Shasta Dam include: 1) adecrease in the minimum flow and an increase in the number of very low flows, 2) anincreased occurrence of moderate flow throughout the year, particularly during thesummer and fall irrigation seasons, and 3) a reduction in the number and volume of highand very high flows throughout the year (Buer et al. 1987). Regulation of discharge byShasta Dam has increased summer flows from about 6200 cfs (for the years 1889-1944)up to 10,520 cfs (for the years 1945-1970) (Brice 1977). The maximum observed floodpeak at Red Bluff before regulation was 250,000 cfs; since 1946, the maximum observedhas been 140,000 cfs (Brice 1977). It has been observed that the period of 1946 to 1980has experienced a 25% reduction in bank erosion rates from that of the 1896 to 1946period (Brice 1977). This may be due to the reduction of high flows, which decreasesbank erosion, or to the reduction in frequency and magnitude of peak flows due to ShastaDam flow regulation (Buer et al. 1989).

The design discharge for the federal flood control project of the Sacramento River southof RM 174 is 160,000 cfs at the Moulton Weir (RM 185) (USACE 1988). The designflow used for engineering the levee system is 300,000 cfs. Due to this constraint, thereare three primary flood relief structures upstream of the levees at the followingapproximate locations (USACE 1988), which divert a total of 150,000 cfs upstream ofMoulton Weir.

1. RM 191 (M & T Bend), diverting 70,000 cfs2. RM 186.5 (3B’s, a natural overflow), diverting 35,000 cfs3. RM 179 (Goose Lake), diverting 45,000 cfs

Note that two of these structures are located within the study reach, capable of divertingup to 105,000 cfs.

2.3 Environmental Setting

Before European settlement in the early 1800s, there was a wide strip of riparian forestalong the Sacramento River (WET 1988). The first type of land converted to agriculturewas known as rimland, which is adjacent to the river and at a higher elevation than thetule (swamp and overflow lands) in the basins (Buer et al. 1989). By 1871, almost all ofthis area was privately owned and being converted to agriculture (Buer et al. 1989). Thefloodplains were also progressively converted from riparian forest and tule swamp toagriculture, primarily fruit and nut orchards (Katibah 1984). By 1989, 98% of theoriginal riparian forest was gone (Sacramento Handbook 2000).

Micheli et al. (2002) compared migration of the Sacramento River for 50 years beforeand after the completion of Shasta Dam, and found that despite flow regulation, bankmigration rates and erodibility increased approximately 50% as riparian floodplains wereprogressively converted to agriculture. Agricultural floodplains are 80-150% moreerodible than riparian forest floodplains (Micheli et al. 2002). Brice (1977) maintainsthat riparian vegetation promotes higher sinuosity because it can inhibit chute cutoffs,


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therefore clearing trees would result in a reduction of sinuosity and a change in channelform. There are cases where even a narrow fringe of riparian vegetation can deflect theflow of the river and prevent rapid bank erosion (Brice 1977). Also, riparian vegetationon the inside of the meander loop inhibits downstream migration of the meander loop andhelps prevent cutoffs (Brice 1977). Micheli et al. (2002) note that bank strength may beincreased by root reinforcements in riparian-rich areas. Channel roughness is higher forriparian forest border reaches than agriculture rich reaches (Micheli et al. 2002). Ifmeander migration mirrors the flow field, vegetation removal could cause greatermigration in the downstream versus the cross-stream direction and result in perhaps a lesssinuous channel pattern over time.

2.4 Historic Changes in Channel Location

The factors described above—geologic controls, hydrological changes and changes inland use—have a combined affect on the location of the present day Sacramento River.The largest influence on channel location and meander migration in the study reach hasbeen the progressive installation of riprap through time. Additionally, the amplitude ofbends within the study reach has decreased through time. The four separate parts of thestudy reach described below exhibit wide variation in meander migration rates, sinuosity,and type of vegetation on the banks.

We describe channel movement in the study reach of the Sacramento River from 1870 to1997, using banklines mapped by Greco, et al. (2002). Channel bank locations spanapproximately 100 years (1870-1997) and, depending on data availability, were mappedat intervals varying from one to 17 years. For years prior to aerial photography (1870,1887, 1904, 1920), channel bank locations were chosen to coincide with channel edgesindicated on USGS topographic maps (1:68,500). The USGS method for defining thesechannel banks is undocumented. Where aerial photography is available (1937 through1997), bank locations were mapped from air photos ranging in scale from 1:40,000 to1:6,000. The majority of photos were flown at a scale of 1:10,000 or smaller, allowing forhigh mapping precision. Banklines were mapped by tracing the contact between riverwater and adjacent dry land and these traces were then rectified in the Arc View/Arc InfoGIS environment. For a detailed description of mapping and rectification methods, seeGreco et al. (2002).

The study reach is divided into four main subreaches, or Zones: RM 201-198 (Zone 1),RM 198-193 (Zone 2), RM 193-189 (Zone 3), and RM 189-185 (Zone 4). Banklines areshown with the older years overlain by more recent years for all figures in this section.We describe the study reach starting upstream and moving downstream.

River Miles 201-198 (Zone 1)

Since 1904, this reach has been characterized by channel stability. The bend at RM 199narrowed between 1870 and 1887, and cutoff by 1904 (Figure 5A). The channelconfiguration after the cutoff establishes the river left bend at RM 198 that still exists


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today. The reach from RM 201-198 has been very straight with little or no shift of thechannel after the cutoff of the bend at RM 199 in 1904. The channel width has also beenrelatively constant since 1904 (Figure 5B). There is no obvious geological control on thechannel, and riprap was installed by 1978. However, this is the location of the axis of theGlenn Syncline (discussed in Section 2.1 Geologic Setting). The full effects of the GlennSyncline on the Sacramento River are not known, but evidence suggests that channellocation and shape is influenced by this subsurface structure. The apex of the bend atRM 198 migrated downstream until 1975, at which time rip-rap was installed along theouter bank (Figure 5B).

Figure 5. River miles 201-198. Historical river channel movement from (A) 1870-1904 and(B) 1904-1974.


The reach from RM 198-193 encompasses two large bends of interest—the bend near theconfluence of Pine Creek and the Jenny Lind Bend. The Pine Creek Bend has been quitemobile through time. In the reach that contained the Jenny Lind Bend, RM 196-193,there has been a decrease in the amplitude of the meander bends, but the wavelength hasremained relatively constant. The Pine Creek Bend (RM 199), becomes established aftera cutoff by 1904. The confluence of Pine Creek and the Sacramento River migrates eastbetween the late 1800s and 1904—this is as far east as the river channel ever moves(Figure 6A). Pine Creek Bend migrates downstream over the years. The main channel isabandoned and a secondary channel, or “cutoff channel”, is occupied by 1980(Figure 6C). The river essentially does not migrate again in this area. Between 1870 and1920, the Jenny Lind Bend maintained high sinuosity and migrated downstream. By 1937the Jenny Lind Bend experiences a cutoff (Figure 7B). This subreach of the riverexperiences small movement and sinuosity changes. Riprap was installed between 1974and 1980, limiting meander migration.


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Figure 6. Pine Creek Bend, RM 199-196. Historical channel movement from (A) 1904-1962, (B)1937-1974, and (C) 1952-1987.


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Figure 7. Jenny Lind Bend, RM 198-193. Historical channel movement from (A) 1870-1904, (B)1904-1937, (C) 1920-1952, (D) 1952-1974, (E) 1974-1980, (F) 1974-1987, and (G) 1974-1997.


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Figure 7 continued.


This area on the river (RM 193-189) is the least geologically constrained, and the rivermigrates freely in this location prior to the installation of riprap, exhibiting classicmeander bend forms. From 1870-1904 the bends in this area migrate downstream andconstrict (Figure 8A). There is no data for 1920, and by 1937 the bends are very differentin location and shape (Figure 8B). What is clear is there is an overall decrease in


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sinuosity caused by two cutoffs, one at RM 190 and another at RM 191.5 (Figure 8B).From 1937-1964, there is downstream migration of the bends, and by 1974 the channelhas migrated or cutoff into a new channel (Figure 8C). After 1974, the bends continuemigrate downstream, especially at RM 192 and RM 190 (Figure 8D). The bends areconstrained by riprap, but exact dates for the riprap installation are unknown. There is aflood control structure (M&T) at RM 190.7.

Figure 8. River Miles 193-189. Historical channel movement from (A) 1870-1904, (B) 1904-1952, (C)1952-1974, (D) and 1974-1997.

River Miles 189-185 (Zone 4)Over the time of historical record, this subreach (RM 189-185) has developed twodistinct and large bends. Monroeville Bend (RM 190-188) develops into a very highamplitude bend that been constrained in its current location by riprap. Kimmelshue Bend(RM 188-185.5) progressively develops into a single bend that then becomes a bilobatebend (compound bend consisting of more than one identifiable radius of curvature) whereone of the smaller bends cuts off. Monroeville bend is present during the earliest year forwhich we have data (1870), and by 1952 it has migrated downstream and rotated its


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orientation to very close to its current location (Figure 9A and 9B). By 1978 riprap wasinstalled, preventing what appears to be a potential cutoff, and the bend is essentiallystatic until 1987 (Figure 9E). In 1978, there was the development of a small side channelat approximately RM 190, and the river eventually occupies this side channel as the mainchannel in 1987 (Figure 9D and 9E).

Kimmelshue bend is established in 1904 (Figure 9A). In 1974, the bilobate character ofthis bend becomes very pronounced, with one lobe bounded by inflection points atRM 188-187, and the other from RM 187-186 (Figure 9C). By 1987 the downstreamlobe has cutoff (Figure 9D and 9E). This cutoff changed the orientation of thedownstream bends at RM 185-186. In this reach, there are private diversion structures atRM 188.5, 187, 185 (two) and 184. The primary use of the water from these smallpumps is for agricultural irrigation.


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Figure 9. Monroeville and Kimmelshue bends, RM 189-185. Historical channel movement from (A)1870-1904, (B) 1904-1952, (C) 1952-1974, (D) 1974-1980, (E) 1952-1987, and (F) 1952-1997.


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Figure 9 continued.

3.0 Methodology

3.1 Historical Years of Record

Changes of the four subreaches, or Zones, within the study reach were quantitativelyanalyzed using available historic data. Figure 10 shows the location of the Zones andindividual bends in 1904, the earliest year of record used in this analysis. We presentgraphical results for the evaluation of each zone for the following variables:

1. Distance between inflection points (wavelength)2. Sinuosity3. Area reworked and rate of bend migration

The 1870 and 1887 historic years of record are not included in the quantitative analysis,primarily because planform data for these years are unreliable. Planform data for theseyears of record originated from topographic maps that, when digitized and rectified,located the Sacramento River in an unlikely area. For the discussion in Section 2.4Historic Changes in Channel Location, these years were included; however the locationof the river was manipulated to agree with later years of record.

There are cases where structural elements of the river are referred to as bends, althoughthey may be almost straight in a given year. This was done because in other years theymay develop significant curvature, and accounting for the whole river as “bends”

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The controls on and evolution of channel morphology of the ... · The controls on and evolution of channel morphology of the Sacramento River: A case study of River Miles 201-185