NS_draft_Rest_Plan_2009.pdf

580 Vallombrosa Avenue Phone: (530) 894-5401 Chico, CA 95926 Fax: (530) 894-2970 info@riverpartners.org www.riverpartners.org

Prepared for:

California Department of Fish and Game and

Wildlife Conservation Board

Riparian Restoration Plan for the Nelson Slough Unit Feather River Wildlife Area Sutter County, California

January 28, 2009

Riparian Restoration Plan for Nelson Slough Unit January 28, 2009 River Partners Page i

TABLE OF CONTENTS

I. INTRODUCTION

A. Project Overview B. Cooperative Relationships C. Project Goals and Objectives D. Purpose of the Restoration Plan

II. SITE DESCRIPTION

A. Location B. Land-use History C. Soils D. Topography E. Hydrology F. Vegetation G. Wildlife

III. CONCEPTUAL SITE MODEL

A. Past Environmental Conditions B. Likely Successional Patterns without Restoration C. Comparison to Nearby Vegetation (Reference sites) D. Restoration Strategies for the Nelson Slough Unit E. Identification of Ecological Benefits and Targeted Wildlife Species

IV. PLANTING DESIGN

A. Design Considerations B. Rationale for Plant Communities C. Composition and Location of Plant Communities D. Planting Tiles and Baseline Data

V. ENHANCEMENT

VI. REGULATORY COMPLIANCE

A. CEQA

B. Reclamation Board Encroachment Permit C. VELB Memorandum of Understanding D. Cultural Resources E. Herbicide Permits

VII. FIELD IMPLEMENTATION

A. Cell Descriptions B. Row Orientation and Plant Spacing C. Site Preparation D. Irrigation System E. Plant Material Collection and Propagation F. Plant Installation G. Plant Maintenance

VIII. MONITORING AND REPORTING

A. Field Reports B. End of Season Monitoring C. Photo Points D. Avian Monitoring E. End of Season Reports and Final Report

IX. SAFETY ISSUES

A. Standard Field Procedures B. Flood and Fire Contingencies

X. PROJECT IMPLEMENTATION TIMELINE

XI. REFERENCES

River Partners Page ii

List of Tables Table 1. Summary of Project Goals, Objectives and Special Considerations for the Nelson

Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California Table 2. Neighboring Land Conservation Property to the Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Table 3. Summary of Typical Soil Conditions from the Soil Survey of Sutter County (USDA

1988) on Soils Found on the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, California

Table 4. Federal and State-listed Endangered, Threatened, and Candidate Species Occurring or Potentially Occurring at the Feather River Wildlife Area

Table 5. Summary of Neotropical Migrant Bird Habitat Requirements (RHJV 2004) Table 6. Key Plant Design Considerations of the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California Table 7. Summary of Overall Proposed Plant Species at the Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Table 8. Composition of Low Density Riparian Shrubland at Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Table 9. Composition of Medium Density Riparian Shrubland at Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Table 10. Composition of Great Valley Valley Oak Riparian Forest at Nelson Slough Unit

Restoration Project, Feather River Wildlife Area, Sutter County, California Table 11. Composition of Great Valley Mixed Riparian Forest at the Nelson Slough Unit

Restoration Project, Feather River Wildlife Area, Sutter County, California Table 12. Composition of Herbaceous Wildflower Meadow Association at the Nelson Slough

Unit Restoration Project, Feather River Wildlife Area, Sutter County, California Table 13. Species of Great Valley Riparian and Floodplain Meadow at the Nelson Slough Unit

Restoration Project, Feather River Wildlife Area, Sutter County, California Table 14. Species of Native Grassland Association at the Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Table 15. Herbaceous Understory Species in Row Centers and Hedgerows at the Nelson

Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California Table 16. Descriptions for Cells I & II at the Nelson Slough Unit Restoration Project, Feather

River Wildlife Area, Sutter County, California Table 17. Descriptions for Cells III & IV at the Nelson Slough Unit Restoration Project, Feather

River Wildlife Area, Sutter County, California Table 18. Standard Planting Materials and Times for Woody Species Table 19. Summary of Herbivore Control Methods at the Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Table 20. Timeline for the Scope of Work Tasks at the Nelson Slough Unit Restoration Project

– Cell II, Feather River Wildlife Area, Sutter County, California

List of Figures

Figure 1. Location Map, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 2. Project Boundary, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 3. 1949 Aerial Photograph, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 4. 1968 Aerial of Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

River Partners Page iii

Figure 5. 1975 Aerial of Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 6. 1987 Aerial of the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 7. Soils Map, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 8. Topography Map, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 9. Graph Depicting River Gage Height Near Nicolaus During the New Years Eve Storms of 2005-2006

Figure 10. Photos of Current Vegetation Conditions on the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

Figure 11. Habitat Value of Native Riparian Plants (RHJV 2000) Figure 12. Planting Associations and Enhancement Area, Nelson Slough Unit Restoration

Project, Feather River Wildlife Area, Sutter County, California Figure 13. Understory Design for Cell I, Nelson Slough Unit Restoration Project, Feather River

Wildlife Area, Sutter County, California Figure 14. Understory Design for Cells II & IV, Nelson Slough Unit Restoration Project, Feather

River Wildlife Area, Sutter County, California Figure 15. Understory Design for Cell III, Nelson Slough Unit Restoration Project, Feather River

Wildlife Area, Sutter County, California Figure 16. Planting Design Implementation for Herbaceous Meadow Species in

Shrubland/Grassland Transition Zone, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California

List of Appendices

Appendix I Official Soil Series Descriptions for Soils Occurring on the Nelson Slough Unit Appendix II Soil Pit Logs for the Nelson Slough Unit Appendix III Hydraulic Modeling Report for the Nelson Slough Unit Appendix IV Planting Association Tiles for the Nelson Slough Unit Appendix V VELB Memorandum of Understanding for the Nelson Slough Unit Appendix VI Hedgerow Design for the Nelson Slough Unit

Suggested citation:

River Partners. 2009. Riparian Restoration Plan for the Nelson Slough Unit. Feather River Wildlife Area, Sutter County, California. Colleen Martin. Chico, California.

River Partners Page 1

Acknowledgements

The following individuals contributed to this restoration plan:

Name Affiliation Dale Whitmore CA Department of Fish and Game Don Trieu MBK Engineers Jason Schwenkler Geographical Information Center Colleen Martin River Partners Helen Swagerty River Partners Ruben Reynoso River Partners Tom Griggs River Partners Nicholas Pacini River Partners Dave Neubert River Partners

River Partners Page 2

EXECUTIVE SUMMARY

The Nelson Slough Unit of the Feather River Wildlife Area was acquired by the California Department of Fish and Game in 1989. The parcel consists of 750 acres, of which about 30% is remnant and/or naturally regenerated riparian forest. The remainder of the property consists of abandoned agricultural lands that have failed to regenerate riparian forest after being retired from agriculture in the mid 1980’s.

In 2007, River Partners received funding from the Wildlife Conservation Board to create a restoration plan for the 750-acre Nelson Slough Unit and to restore and enhance approximately 250 acres of riparian habitat that will benefit a broad range of special status species, migratory birds, gallinaceous birds and anadromous fish; increase connectivity with existing riparian habitat; and implement control measures for invasive non-native plant species. The Nelson Slough Unit is split into four cells, which will be restored in intervals. Current funding covers the restoration of Cell II, which is the most degraded cell.

The Nelson Slough Unit is surrounded by thousands of acres of land conservation ownership, including property owned by California Department of Fish and Game, US Fish and Wildlife Service, Audubon Society and Three Rivers Improvement Levee Authority. Restoring this piece of property will link together over 3,500 acres of contiguous habitat along the Feather River capable of supporting a number of threatened and endangered species, including the western yellow-billed cuckoo, Swainson’s hawk and the valley elderberry longhorn beetle. In addition, the Nelson Slough Unit is adjacent to over 4,500 acres of conservation oriented properties located in the Sutter Bypass.

A detailed site evaluation examined soil texture, structure, stratification and depth to water table, as well as past land use and current conditions. Low Density Riparian Shrubland is the principal community to be planted on the Nelson Slough Unit.

Additionally, Great Valley Valley Oak Riparian Forest, Great Valley Mixed Riparian Forest, Native Grasslands and Herbaceous Wildflower Meadows will be planted.

Approximately 62,000 woody, native riparian plants will be planted on the property.

An herbaceous understory of mugwort (Artemisia douglasiana), gumplant (Grindelia camporum), telegraph weed (Heterotheca grandiflora), Spanish clover (Lotus purshianus) and native grass mix will be planted between all planting rows. Plugs of Santa Barbara sedge (Carex barbarae) will be planted at the base of valley oaks (Quercus lobata) and Fremont cottonwoods (Populus fremontii). Native herbaceous understory provides vital habitat for riparian wildlife and recent studies of riparian restoration in the Sacramento Valley have shown that natural recruitment in the understory is dominated by non-natives.

hpera Note Says low density riparian shrubland is the principal community to be planted. I would like to see grassland as the majority.

River Partners Page 3

Riparian Restoration Plan for the Nelson Slough Unit, Feather River Wildlife Area, Sutter County, California

I. INTRODUCTION

A. Project Overview In 2007, River Partners received funding from the Wildlife Conservation Board (WC- 7051 SC) to plan and initiate habitat restoration on the 750-acre Nelson Slough Unit of the Feather River Wildlife Area. The unit is split into four cells and will be restored in intervals. Cell II will be the first to be restored as it is the most degraded cell.

The Nelson Slough Unit is part of the Feather River Wildlife Area and is adjacent to over 3,500 acres of conservation oriented properties along the Feather River and 4,500 acres of conservation oriented properties along the Sutter Bypass. The Nelson Slough Unit has great potential to provide a diversity of habitats for a wide array of riparian dependant species. However, the majority of the site is currently fallow land that is dominated by invasive, non-native weed species. Without intervention, weeds will continue to competitively exclude native plant species from establishing on site, resulting in poor wildlife habitat.

This project will plant approximately 62,000 native riparian trees, shrubs and vines on flood-prone land owned and managed by California Department of Fish and Game (DFG). River Partners will actively restore riparian habitat on 520 of the 750 acres at the Nelson Slough Unit. Enhancement activities will occur within 230 acres of existing riparian forest. Planting for Cell II is scheduled to begin in spring 2009 with the goal of three years of maintenance.

B. Cooperative Relationships The project area is currently owned and managed by the California Department of Fish and Game. The levee on the northern border of the project area is maintained by Department of Water Resources - Maintenance Area 3 of Sutter County. During the planning of this project River Partners has worked closely with the aforementioned organizations.

C. Project Goals and Objectives The primary project goal is to rapidly establish and enhance approximately 750 acres of high quality native riparian habitat that will benefit a broad range of special status species. Table 1 presents the proposed goals, objectives and special considerations for the project.

River Partners Page 4

Table 1. Summary of Project Goals, Objectives and Special Considerations for the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

Project Goal

• Restore and enhance riparian habitat on 750 acres and increase the connectivity of new habitat to existing riparian habitat (decrease fragmentation) in the Feather River Wildlife Area and Sutter Bypass.

• Provide habitat for Federal and State-listed species including but not limited to Swainson’s hawk, western yellow-billed cuckoo, western red bat, Chinook salmon, steelhead trout, valley elderberry longhorn beetle, and benefit other wildlife species, with particular emphasis on neo-tropical and gallinaceous birds.

Project Objectives

• Implement project using an adaptive management approach.

• Provide specific habitat features for targeted wildlife species.

• Establish self-sustaining native plant communities within a three-year period.

• Use hydraulic analyses to develop a restoration design consistent with floodway management goals.

• Develop a restoration design to meet management objectives.

• Plant approximately 62,000 native trees, shrubs, and vines; incorporate a dense herbaceous understory planting; and establish perennial grasslands.

• Minimize need for replanting by “overplanting” the site and anticipating some mortality.

• Monitor project performance.

• Build a partnership with Federal, State and local community groups.

Site Specific Conditions

• Coordinate restoration efforts with DFG Feather River Wildlife Area management to maximize habitat benefit for public use and cost savings.

• Coordinate restoration design and implementation timing with DWR and Sutter County to complement their future levee improvement work at the Nelson Slough Unit and the surrounding reach of the Feather River and Sutter Bypass.

• Aggressively control existing patches of non-native invasive species.

D. Purpose of the Restoration Plan This restoration plan includes all four phases of this project. The purpose of the restoration plan is to:

• Identify project goals, objectives, management hypotheses and potential implementation challenges,

• Summarize the site land-use history, soils, hydrology, vegetation and wildlife,

• Outline our current understanding of the physical and biological factors that influence site ecology (a conceptual site model),

• Describe the plant design and the rationale for its selection,

• Describe the implementation process including field preparation, planting methods, irrigation design and schedule and methods of weed control,

• Outline project monitoring, and

• Provide a timeline for project tasks.

River Partners Page 5

II. SITE DESCRIPTION

A. Location The Nelson Slough Unit is located in Sutter County, California approximately 17 miles south of Yuba City (Figure 1). The Highway 99 Bridge passes over the site and the Feather River, running north/south through Cell I. The town of Nicolaus is located across the river from Nelson Slough on the east side of Highway 99. To the west of Nelson Slough is the Sutter Bypass, which is a floodwater bypass for when the Sacramento River is at flood stage.

The project area (750 acres) occupies river floodplain on the right bank of the Feather River between River Mile 7.5 and 10.5R (Figure 2). Limited remnant riparian habitat occurs along the northeastern and southwestern portion of the site, as well as along the south levee bank. The Feather River lies along the southern border of the restoration site. Private agricultural lands surround the northern boundary and are separated from the project area by a levee. No change to the surrounding private property will occur as a result of this project. The northeastern edge of the property abuts the Bobelaine Audubon Ecological Preserve. Surrounding the site are thousands of acres of land conservation ownership, as shown in Table 2.

Table 2. Neighboring Land Conservation Property to the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

Property Feather River

River Mile Management Area Star Bend Unit 19 FRWA- DFG 50 acres O'Connor Lakes Unit 17-19 FRWA- DFG 296 acres Lake of the Woods Unit 12.5-18 FRWA- DFG 639 acres Bear River Levee Setback Project 12.5* TRLIA 695 acres Bobelaine Wildlife Sanctuary 11-14 Audubon Society 436 acres Abbott Lake Unit 20-22 FRWA- DFG 439 acres Sutter Bypass SBWA- DFG 3,204 acres Sutter National Wildlife Refuge USFWS 2,600 acres

*River Mile for Bear River

B. Land-use History Prior to the arrival of Europeans, Native Americans of the Valley Nisenan populations established villages along the Feather River and its tributaries in the vicinity of the site. No prehistoric resource sites have been recorded in this area.

The Nelson Slough Unit lies within the region deeded to John Sutter under the New Helvetia Land Grant in the 1840’s. He built Hock Farm, a rancho near the site which allowed cattle to graze freely along the Feather River (Josselyn et al. 1988). A property ownership map of the Feather River from approximately 1880 shows Sam Brannon as the property owner. A 1912 U.S. Army Corps of Engineers map shows that the area had not yet been cleared for agriculture at that time, with willows and cottonwoods throughout. The exact dates are unknown, but men by the names of Mr. Richards and Mr. Hamatani owned the property prior to Mr. Tom Nevis purchasing it (Whitmore, personal communication). Based on historical aerials, the majority of the riparian

River Partners Page 6 woodland on site was cleared sometime between the 1950’s and mid-1960’s (Figures 3 & 4). Up until the late 1970’s, the property remained primarily fallow and was used for cattle grazing, which was the primary land use along the Feather River at that time (Figures 4 & 5). The property was developed for agriculture in the late 1970’s to early 1980’s by Mr. Nevis. The land was partially cleared and rice fields were put in Cell II and the southern portion of Cell I, as shown in the 1987 aerial (Figure 6). The business proved to be unsustainable for commercial production and the high value that rice had in the early 1980’s fell in the late 1980’s, causing the practice to be unsuccessful (Whitmore, personal communication). After this happened, the insurance company that loaned the money to Mr. Nevis to establish the rice fields, Aetna Insurance Company, repossessed the property. In 1989, DFG purchased the property from Aetna Insurance Company (Whitmore, personal communication).

The Nelson Slough Unit is located in an area of the Central Valley that floods regularly.

Early European settlers built simple dirt levees to combat seasonal floods (SBFCA 2008). Due to major flooding that occurred during the beginning of the 20th century, an intricate network of levees and bypasses where created in the Sutter Basin, including the Sutter Bypass. In 1917, levees were constructed along the Sutter Bypass to help control flows and prevent flood damage. The Sutter Bypass was completed in 1930 and collects Sacramento River flood overflow water that has passed through Butte Slough and the Butte Sink (SBFCA 2008). The Sutter Bypass originates at Highway 20 and runs through the Sutter Basin, rejoining the Sacramento River near the Feather River and Sacramento River confluence. To prevent flood waters from overtopping levees by holding sudden storm water surges, dams were built along the main rivers in the area, including Oroville Dam on the Feather River in 1968 (SBFCA 2008). Although major construction occurred to control floods, levee breaches still occurred in 1917, 1955, 1986 and 1997, including a break at Yuba City and Nicolaus in 1955 which flooded almost 100,000 acres and caused 38 deaths and 3,200 injuries (SBFCA 2008).

River Partners Page 7

Figure 1. Location Map, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

River Partners Page 8

Figure 2. Project Boundary, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

River Partners Page 9

Figure 3. 1949 Aerial Photograph, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

Woodland community with mature trees were still present on the majority of the site, with sand depositions scattered throughout.

River Partners Page 10

Figure 4. 1968 Aerial of Nelson Slough Unit Restoration Project, Feather River

The woodland community has been cleared from the majority of the site, with mature trees only remaining in the northeastern corner. During this time period, the main land use along this section of the Feather River was livestock grazing.

River Partners Page 11

Figure 5. 1975 Aerial of Nelson Slough Unit Restoration Project, Feather River

The majority of the site remains cleared of mature trees and a woodland community, with livestock grazing still the primary land use.

River Partners Page 12

Figure 6. 1987 Aerial of the Nelson Slough Unit Restoration Project, Feather River

Rice fields were constructed in the late 1970’s to early 1980’s and farmed for only a few years. The mature trees in the northeastern corner of the site were also cleared, roads were installed and the ground was altered. The land usage on this portion of the property during this time period is unknown.

River Partners Page 13

C. Soils

1. General Soil Series Information

There are three official soil series found on site, Columbia, Holillipah and Shanghai.

The project area is made up almost entirely of Holillipah soils (Figure 7). This series consists of deep sand, which is stratified and somewhat excessively drained. They are derived from mixed alluvium and are frequently flooded (USDA 1988). Table 3 describes typical soil properties of the series’ found at the Nelson Slough Unit. A full description of each soil series can be found in Appendix I.

Table 3. Summary of Typical Soil Conditions from the Soil Survey of Sutter County (USDA 1988) on Soils Found on the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, California.

Soil Property Columbia fine sandy loam, frequently flooded

Holillpah loamy sand, frequently flooded

Shanghai fine sandy loam, channeled

Mapping Unit 121 135 161

Percent Slope 0-2% 0-2% 0-2%

Texture sandy loam loamy sand sandy loam

Depth of Soil very deep very deep very deep

Drainage moderately well somewhat excessively somewhat poorly

Permeability moderately rapid moderately rapid moderate

Available Water Holding Capacity moderate low high

Plant Growth Limitations

Long periods of flooding in December to April.

Long periods of flooding in December to April.

Soils may develop tillage pans. Long periods of flooding in December to April.

River Partners Page 14

Figure 7. Soils Map, Nelson Slough Unit Restoration Project, Feather River

River Partners Page 15

2. Soil Pit Results In addition to the information provided by the Sutter County Soil Survey, River Partners excavated 5 soil pits in 2008 within the Nelson Slough Unit (Appendix II). Observations from these samples include:

• Soil texture and structure,

• Stratification,

• Depth to water table, and

• Rooting depth of vegetation

Sampling occurred mostly in Cell 2 (4 pits) where most of the active restoration activities will be concentrated. In areas closest to the river, predominantly silt to silt loams with alternating layers of sand were observed, demonstrating exposure to river processes.

Less deposition and sand layering was observed in pits closer to the Feather River levee. Soil textures transitioned into more of a homogeneous layer of silt. No barriers to root growth were found as roots reached down to the bottom of the pits (approximately 10 feet). Evidence of mottling depicted seasonal flooding or inundation for a period of time. The last pit, located in Cell 3, along the edge of an existing elderberry grove and open annual grasslands area, exhibited layering of 3 feet of silt on a 2 foot layer of sand.

D. Topography The topography on the Nelson Slough Unit is relatively flat, with a slight change in gradient in a few locations (Figure 8). The elevation on site ranges from 30 to 40 feet above mean sea level. The highest points on site occur along the bank of the Feather River, creating a natural levee along the property. This levee ranges from 5 to 10 feet tall and was created by overbank deposition during flood events. In the southeastern portion of the site (Cells II and III), there is a gradual decrease in elevation, which causes these areas to flood during high flow events. In Cells I and II, remnant rice checks still exist from past agricultural practices on the site, which will be removed during the restoration process.

River Partners Page 16

Figure 8. Topography Map, Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

River Partners Page 17

E. Hydrology The average annual rainfall in the area of the Nelson Slough Unit is 17.63 inches (DWR 2007). The approximate flood recurrence is every 5-10 years (Whitmore, personal communication). Flood waters enter the site from the north and are slowed by the rock weir built along the southwestern boundary of the property. The rock weir was designed to filter out the sediment and silt from the Feather River during flood events prior to the water entering the Sutter Bypass (Whitmore, personal communication). This structure significantly slows down the water on the south end of the property and deposits large amounts of silt and sediment into Cell III. The exact construction date of the rock weir is unknown but dates back to at least the 1940’s, as shown on the 1949 aerial photograph (Figure 3).

1. Flood Stages Extremely high flows resulting in the loss of life and billions of dollars in damages in California’s Central Valley have occurred in 1917, 1955, 1964, 1986 and 1997. Most recently, large storms hit northern California in 2005-2006 and caused regional flooding.

Coined the New Years Eve Storms, they brought substantial amounts of precipitation.

Small and quick-responding rivers such as the Russian and Napa experienced heavy flooding. However, dam releases on large and highly controlled rivers such as the Sacramento and Feather in anticipation of the heavy rains lessened the impacts, but high water still occurred. The Feather River water levels in the vicinity of the project area reached monitor stage (above 40.0 feet), resulting in the river rising above bankfull and flooding areas within the levees. The river crested at 45.86 feet near Nicolaus, which is just north of the project site, the morning of January 1, 2006 (Figure 9) (DWR 2007).

Figure 9. Graph Depicting River Gage Height Near Nicolaus During the New Years Eve Storms of 2005-2006.

River Partners Page 18

2. Hydraulic Modeling

As part of the Encroachment Permit Application for the project, MBK Engineers conducted a hydraulic analysis of the proposed restoration project to ensure that the planting design is flood neutral (MBK Engineers 2008, Appendix III). A 1-D HEC-RAS model was used to determine the hydraulic impacts associated with the proposed restoration at Nelson Slough. The HEC-RAS model was calibrated to the January 1997 flood event and includes the completed Bear River setback levee and the Feather River setback levee from RM 18 to 24. A 1-D model rather than a 2-D model was used due to insufficient amounts of data along this stretch of the Feather River. Although 2-D modeling exists along the Nelson Slough project area, the data stops at the southern boundary of the project area. However, in addition to evaluating the project site, a hydraulic analysis must review potential impacts that may result upstream and downstream. Because the 2-D modeling stops at the project boundary, only a 1-D model was possible.

To simulate the proposed planting plan, the Manning’s roughness coefficient, which is the degree of flow resistance caused by vegetation during a flood event, was modified to reflect the long term vegetation condition at each planting area. In addition, a sensitivity analysis, which accounts for uncertainty in the selection of the Manning’s roughness coefficient, was performed for the proposed planting areas by increasing the predicted roughness by 20%. Both 100-year flood events and 200-year flood events were simulated. Based on the simulation results, MBK concluded the following:

• The modified roughness coefficient of the riparian planting on the Nelson Slough Unit would have less than significant impacts to the water surface elevations. For example, at river mile 9.27 there would be a 1/10th of a foot increase in water surface elevation during a 100 or 200 year flood event, which is within the margin of error and considered insignificant.

• The increase in water surface elevation would not have a significant impact on the freeboard along the east and west levee of the Feather River. The minimum freeboard at river mile 9.75 would be approximately 4.5 feet in a 100-year flood event and approximately 2 feet in a 200-year flood event.

F. Vegetation The majority of the site is dominated by annual herbaceous non-natives, including annual ryegrass (Lolium multiflorum), ripgut brome (Bromus diandrus), soft chess (Bromus hordeaceus), yellow starthistle (Centaurea solstitialis), wild radish (Raphanus sativus) and black mustard (Brassica nigra), as well as perennial pepperweed (Lepidium latifolium) (Figure 10). In portions of the site, especially in Cell I, there are stands of native herbaceous species, including telegraph weed (Heterotheca grandiflora), mugwort (Artemisia douglasiana), Santa Barbara sedge (Carex barbarae), gumplant (Grindelia camporum), creeping wildrye (Leymus triticoides), Spanish clover (Lotus purshianus), dogbane (Apocynum cannabinum), evening primrose (Oenothera elata), lupine (Lupinus spp.) and California poppy (Eschscholzia californica). Remnant riparian forest occurs in the northern portion of Cell I, the northwestern portion of Cell III and

River Partners Page 19 borders the levee along the northern portion of the site and the weir along the western portion of the site. Native tree and shrub species include Fremont cottonwood (Populus fremontii), valley oak (Quercus lobata), box elder (Acer negundo), Oregon ash (Fraxinus latifolia), Mexican elderberry (Sambucus mexicana) and coyote brush (Baccharis pilularis). California blackberry (Rubus ursinus), creeping wildrye, mugwort and Santa Barbara sedge make up portions of the understory. The remainder of the understory is non-natives, including Himalayan blackberry (Rubus armeniacus) and perennial pepperweed. Sparse remnant riparian forest occurs along the shore of the Feather River, including sandbar willow (Salix exigua), white alder (Alnus rhombifolia), arroyo willow (Salix lasiolepis), box elder, Fremont’s cottonwood, Mexican elderberry and black willow. The southern portion of Cell III is dominated almost exclusively with mature Mexican elderberry and an annual grassland understory with large patches of Santa Barbara sedge interspersed without. Over 200 elderberry shrubs are present in this portion of the site.

Figure 10. Photos of Current Vegetation Conditions on the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

Annual grasslands composed of primarily invasive non-native species dominate the site.

River Partners Page 20

Remnant riparian with native understory occurs in the northern portion of Cell I.

Elderberry grove with annual grassland understory is the dominant habitat in Cell III.

River Partners Page 21

G. Wildlife Numerous wildlife species have been observed on site, including coyote, California quail, lark sparrow, wood duck, Cooper’s hawk, spotted towhee, Bullock’s oriole, western kingbird, western bluebird, black-headed grosbeak, California towhee and house wren. The property supports a number of different raptor species that utilize open habitat for foraging, including Swainson’s hawk, great-horned owl, barn owl, red-tailed hawk, white-tailed kite and northern harrier. Cliff swallow, house finch and great-horned owl were observed nesting in the Highway 99 Bridge which passes over Cell I.

Table 4 lists the federally and state-listed species that occur or have a potential to occur at the Feather River Wildlife Area.

Table 4. Federal and State-listed Endangered, Threatened, and Candidate Species Occurring or Potentially Occurring at the Feather River Wildlife Area.

Name Scientific Name Status

Valley elderberry longhorn beetle Desmocerus californicus diamorphus FT Chinook salmon, Sacramento River winter-run ESU

Oncorhynchus tshawytscha FE, CE

Chinook salmon, Central Valley spring-run

ESU

Oncorhynchus tshawytscha FT, CT

Chinook salmon, Central Valley Fall-run and late fall-run ESU

Oncorhynchus tshawytscha CSC

Green sturgeon SDP Ascipenser medirostris FT, CSC Steelhead, Central Valley ESU Oncorhynchus mykiss FT Western red bat Lasiurus blossevillii CSC Bald eagle Haliaeetus leucocephalus CE Least Bell’s vireo (extirpated) Vireo bellii pusillus FE, CE Peregrine falcon Falco peregrinus anatum CE Swainson’s hawk Buteo swainsoni FSC, CT Western yellow-billed cuckoo Coccyzus americanus occidentalis FC, CE Willow flycatcher Empidonax trailii FSC, CE ESU – Evolutionary Significant Unit CE – California State-listed Endangered Species FE – Federal-listed Endangered Species CT – California State-listed Threatened Species FT – Federal-listed Threatened Species CSC – California Species of Concern FC – Federal Candidate Species FSC – Federal Species of Concern

River Partners Page 22

III. CONCEPTUAL SITE MODEL

This conceptual site model:

• Presents our understanding of the physical and biological factors that influence site ecology,

• Outlines our restoration strategy,

• Provides an overview of the plant design, and

• Identifies ecological benefits and targeted wildlife species.

The principles described in this section will guide the implementation of the project.

A. Past Environmental Conditions During the 1800’s, gold mining operations, including hydraulic mining, occurred along the upper Feather River. Hydraulic mining practices blasted mountainsides with water, introducing large quantities of sediment into the river system. Each winter, unnatural proportions of sand were washed downriver and deposited along the river bank. When the dams and levee systems were built in the 20th century, the natural flow regime and structure of the Feather River was altered from a meandering system of oxbow lakes to an immobile river with relatively consistent flows that were regulated by water discharge from the dams. The altered flooding regime inhibited the sand from washing away as quickly as it would under natural flood conditions, resulting in sandy banks and floodplains. Because sand is much more erodible than the naturally occurring fine textured soils, large amounts of bank incision have occurred.

Throughout most of the 20th century, land-use on the Nelson Slough Unit consisted primarily of livestock grazing. This destroyed much of the native vegetation on site, leaving the area exposed to invasive, non-native species. The remaining native trees and shrubs in Cells I and II were cleared for agricultural crops in the late 1970’s. These practices stripped the majority of the site of its native vegetation, leaving the soil exposed during flood events. Without the native vegetation to protect the soils during flood events, erosion occurs at a higher rate than normal.

B. Likely Successional Patterns without Restoration The Nelson Slough Unit has remained fallow since agricultural practices on the site ended in the late 1980’s. Since that time, the property has been invaded by aggressive, non-native species, including yellow starthistle, ripgut brome and wild radish. Of particular concern is perennial pepperweed, which forms dense monocultures that easily displace desirable vegetation. It is a persistent weed and can spread by sprouting from its roots. There are numerous large patches within the project area and if left unchecked will likely become established throughout the site.

The alteration of the natural river processes, loss of historic disturbance regime, especially floods and fire, and the destruction of the native vegetation on site have made it almost impossible for a natural plant community to passively restore itself. The lack of flows has created a fairly static community, inhibiting the natural recruitment of vegetation by limiting seed dispersal and not providing water to seedlings at the

River Partners Page 23 required development stage. In addition, heavy flood events and fire that would occur in natural conditions would destroy the existing non-native species, leaving the area open for reestablishment and activating the regenerative processes. New tree recruitment, primarily cottonwood and willow, on lower terraces is unlikely with the disturbed hydrograph. The abundance of non-natives creates heavy competition for the native recruits, this coupled with poor regeneration of natives results in conditions un-conducive for passive restoration.

C. Comparison to Nearby Vegetation (Reference sites) The Bobelaine Audubon Ecological Preserve is directly upstream of the Nelson Slough Unit. This property is dominated with mixed riparian and valley oak woodland habitats, with mature riparian tree species, including cottonwood, valley oak and willows.

Although the Nelson Slough Unit contains less woodland than the Bobelaine property, a 1912 U.S. Army Corps of Engineers topographic map and a 1949 aerial photograph shows that the site was historically as vegetated with woodland habitat as it’s neighboring property (Figure 3).

D. Restoration Strategies for the Nelson Slough Unit We recommend the following strategies for the Nelson Slough Unit:

• Employ active restoration techniques to establish riparian vegetation. The poor recruitment of native woody species and the site’s strategic location near existing riparian vegetation makes the Nelson Slough Unit a good candidate for active restoration. Active restoration employs modern farming techniques to efficiently and rapidly establish riparian vegetation.

• Develop a plant design based on current site conditions, flood management and management objectives to address wildlife habitat. River Partners will develop a plant design to address wildlife needs, hydraulic considerations, neighbor requirements and other factors. The plant design is not based strictly on a “historical” or “climax” vegetation target, but is intended to provide high quality early succession-stage habitat for targeted wildlife.

• Use an adaptive management approach to the project. River Partners uses an adaptive management approach (River Partners 2008) to provide a framework to evaluate project progress and respond to new information.

These practices have resulted in high plant survival rate, accelerated natural recruitment of native species (through changes in microclimate and presence of seed sources) and documented wildlife benefits in short periods of time (three years).

E. Identification of Ecological Benefits and Targeted Wildlife Species Riparian ecosystems harbor the most diverse bird communities in the arid and semi-arid portions of the western United States (Knopf et al. 1988, Dobkin 1994, Saab et al.

1995), and may also provide the most important avian habitat in California (Manley & Davidson 1993). Therefore, a restored site will provide vital habitat and conditions for neo-tropical migratory birds and other riparian dependent avian species (Figure 11).

The Riparian Habitat Joint Venture (RHJV) has identified several species of birds as indicators of ecologically healthy riparian systems (RHJV 2004). These species are

River Partners Page 24 termed riparian focal species and collectively their habitat requirements serve as an umbrella for all riparian bird habitat needs. Table 5 presents some of the habitat requirements for each of these species. There is a wide range of spatial and structural habitat requirement among this diverse assemblage of riparian bird species.

Habitat requirements for other targeted species will be incorporated into the plant design. For example, to provide habitat for the western yellow-billed cuckoo, we may plant a cottonwood forest in close proximity to riparian scrub (scattered elderberries, coyote brush with tall herbaceous forbs). Planting elderberry shrubs, which are the host plant for the valley elderberry longhorn beetle (VELB), in a mixed riparian forest will benefit this species. Additionally, the plant design, which may integrate habitat elements such as shaded riverine aquatic (SRA) and large woody debris (LWD), coupled with floodplain reconnectivity will enhance and restore native fish populations.

River Partners Page 25

Figure 11. Habitat Value of Native Riparian Plants (RHJV 2000).

River Partners Page 26

Table 5. Summary of Neotropical Migrant Bird Habitat Requirements (RHJV 2004).

Bird Species Territory/Patch Size Proximity to

Water Vegetation Structure Nesting

Least Bell's vireo (Vireo bellii pusillus)

0.8-1.2 ha (2-3ac);

>250m wide patch

Within 300m Dense willow shrubs 3-5m tall; mugwort understory

Nest low, within 1m of ground

Black-headed grosbeak (Pheucticus melanocephalus)

200m x 50m 50-300m Vertical complex - Cottonwood, willows, wild grape

Nest height 3-4m

Blue grosbeak (Guiraca caerulea)

---- In riparian zone Low herbaceous, upright stems, open canopy

Nest height 0.6-3m

Common yellow-throat (Geothlypis trichas)

0.4-2 ha (1-5 ac) In riparian zone Tall emergent wetland edges Nest height 0-0.6m

Song sparrow (Melospiza melodia)

Variable Near, within 50m Open canopy; dense herbaceous layer;

gumplant, evening primrose

Low to ground; <1m

Swainson's hawk (Buteo swainsoni)

Variable, depending on proximity to foraging habitat

Not riparian obligate

Tall trees in riparian zone near open foraging areas

Nest in tall trees

Willow flycatcher (Empidonax traillii)

<1.0 ha (<2.5 ac) Nests near water

Dense willows; 0-3m height of dense cover, low tree cover

Nests near water; height 0.6-3m

Yellow-breasted chat (Icteria virens)

<5 ha (<12 ac) Prefers near wetlands

Dense thickets of willows and blackberries

Nests in vines and shrubs

Yellow-billed cuckoo (Coccycus americanus)

8-40 ha (19.8-98.8 ac) Nests near or over water

Willow-cottonwood thickets Nest 1.3-13m high

Yellow warbler (Dendroica petechia)

0.06-0.75 ha Wet areas Willows, cottonwoods, early successional

River Partners Page 27

IV. PLANTING DESIGN

River Partners has developed a site-specific planting design that represents a synthesis of the available information on site conditions, using the principles of landscape ecology (Silveira et al. 2003, USFWS 2005), project objectives and PRBO recommendations (Geupel et al. 1987).

Plant communities are based on the terrestrial natural community descriptions of the Holland classification system (Holland 1986). The Holland classification system includes descriptions of site factors and distribution that allows us to fit the appropriate vegetation with site specific characteristics. The community concept provides a useful descriptive label but does not specify arrangement, density or other quantifiable factors that must be addressed to translate the conceptual design to field implementation.

Plant communities of the same name will differ in species composition (especially plant species frequency) and density due to physical factors and management considerations. The following sections will layout those factors for this project.

A. Design Considerations River Partners considered the physical factors (soils, topography and hydrology) and historical vegetation of the site to determine what vegetation would potentially grow on site. The design also incorporates essential habitat elements to conserve, restore and enhance riparian habitat for threatened and endangered species, songbirds, other migratory birds, anadromous fish, resident native wildlife and plants, which is consistent with the mission of DFG. Additionally, recommendations from PRBO Conservation Science (PRBO) (Geupel et al. 1997) are integrated into the design in order to provide quality habitat for focal bird species. The plant design also accommodates the need for transitory storage and allows the conveyance of floodwaters across the floodplain.

Thus, plant communities will describe the densities for trees and shrubs. For hydraulic considerations, we classify woody plants based on structural resistance to flows. Trees will be defined as plants with rigid structures and shrubs as plants with flexible structures. Table 6 lists key considerations of the plant design of the Nelson Slough Restoration Project.

River Partners Page 28

Table 6. Key Plant Design Considerations of the Nelson Slough Unit Restoration Project, Feather River Wildlife Area, Sutter County, California.

Objective/Factor Example of Project Design Considerations Maintain general flood flow conveyance patterns

Orient rows parallel to general flow direction and do not direct flows toward levees.

Provide immediate (< 3 years) habitat benefits and high probability of long-term survivorship

In the short term, relatively transient species (cottonwood and arroyo willow) will provide several generations of targeted bird species with nesting and foraging habitat. Planting a mixed riparian forest, maximizes quality habitat as the slow growing, but shade tolerant oaks mature. Coyote brush, rose, elderberry and blackberry grow quickly and will create gallinaceous and passerine bird habitat.

Minimize sources of weeds, provide habitat along project edges

Use native plants to displace weeds in areas outside the main plantable area. We will use spreading plants (e.g., native blackberry) and native understory species to outcompete perennial pepperweed and other invasive species that currently grow on site.

Maintain high plant species and vegetative structural diversity

PRBO data suggests that bird diversity is highest in areas with 5-7 shrub species over a 50-m2 area. Design considerations include varying density across the site to allow light gaps and create structural differences (grouping trees together will create pockets of shade and light gaps), creating vegetation patches (grouping small shrubs together will mimic larger plants and may attract desirable wildlife species faster than if they were grown apart), and considering herbaceous plantings between plant rows.

Provide foraging and nesting sites for Swainson’s hawk

Tall riparian trees will provide nesting and perching areas.

Perennial grassland (RHJV 2000) provides consistent access to and good availability of prey.

Provide valley elderberry longhorn beetle habitat while minimizing potential impacts to neighbors

Elderberry shrubs will be incorporated into the different plant communities across the site. The southern portion of Cell III already has approximately 200 mature elderberry shrubs on site.

This are will be planted as a native grassland in a way to preserve and protect these existing elderberry shrubs.

Provide foraging, roosting and nesting habitat for neotropical and riparian dependant bird species.

Dense shrub clusters will provide cover for roosting and protection from predators. Annual vegetation, such as doveweed, sunflower and fiddleneck, will provide foraging habitat for seed eaters. A 300 foot wide mixed riparian plant community along the curvature of the river and a 92 acre valley oak riparian forest will provide habitat for woodland species. Native grasslands will provide habitat for species who utilize open habitat.

Create migratory and nesting/roosting corridor for yellow-billed cuckoo and western red bat.

Plant a high density of cottonwood trees along the curvature of the river within a 300 foot wide mixed riparian plant community.

Research in the Central Valley of California suggests that red bats are “strongly associated with riparian habitats, particularly mature stands of cottonwood/sycamore” (Pierson et al. 2004).

Minimize disturbance to wildlife

Use vegetation as a screen and plant in curved rows.

Minimize future impacts to maintenance areas.

No woody species will be planted within 30 feet of any levee, road, or other infrastructure.

River Partners Page 29

B. Rationale for Plant Communities Using our knowledge of the site factors and design considerations, River Partners developed six different plant communities. The physical layout or pattern of individual plants will follow the recommendations from PRBO. Studies by PRBO suggest that shrub cover is the most important variable influencing nest site and there is a positive relationship between tree and shrub richness and bird diversity (Small et al. 2000, Geupel et al. 1997).

River Partners expects at least 70% survival for its restoration plantings at the end of the three year maintenance period. Over the years after maintenance, some mortality is expected based on differences of soil textures and water table depths.