Weir 1 Final Appendices Flattened.pdf

Appendix A Hydrology and Hydraulics Analysis

Butte Creek – Sutter Bypass Weir 1 1 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

1. INTRODUCTION

The Butte Creek – Sutter Bypass Weir 1 Feasibility and Alternatives Analysis Project (Project) proposes to remove or modify Weir 1 to restore fish migration within the West Borrow Canal (WBC) of the Sutter Bypass (Figure A-1) without compromising agricultural operations, channel stability, and adjacent wetlands. ESA has evaluated five project alternatives for addressing fish passage at Weir 1:

• Alternative 0: No Action – No modifications to Weir 1

• Alternative A: Remove Weir – Completely remove weir and fish ladder structures

• Alternative B: Remove Weir with Roughened Channel - Completely remove weir and fish ladder structures, and construct new roughened channel structure

• Alternative C: Replace Weir with Rock Ramp – Partial removal of weir and fish ladder structures, and construct passable roughened ramp

• Alternative D: Operable Weir and Fish Ladder - Completely remove weir and fish ladder and construct an operable Obermeyer weir and pool-chute fish ladder. Alternative D was not explicitly included in the modeling analysis, as the anticipated hydraulics of the alternative can be inferred by the results of Alternative 0 (similar to a closed operable weir) and Alternative A (similar to an open operable weir) to a level suitable for comparisons between alternatives.

As part of the Project, hydrology and hydraulic analyses were assessed in relation to the existing and proposed conditions for fish passage at a level adequate for assessing project alternatives. A hydrologic analysis was conducted using estimated flow data of the WBC to better understand the duration and frequency of flows and stages relevant for fish passage. The hydrologic analysis was focused on dry and low-flow conditions within the WBC when fish passage is most limited by the hydraulic performance of the existing weir and fish ladder. During high flow events, the weir becomes submerged, no longer impeding fish passage.

A two-dimensional (2D) hydrodynamic model was developed to analyze the hydraulics of the WBC under the existing and alternative scenarios and evaluate each alternative’s ability to provide fish passage and avoid negative side effects.

Weir #5

Weir #3

Weir #1

East-West Diversion Weir

Weir #2

Guisti Weir

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SOURCE: ESRI Service Layers Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-1 System Overview

N 0 3

Miles

Sutter NWR

Structure Type Bridge

Weir

Tisdale Bypass

Sutter Bypass

West Borrow Canal

Sacramento River

Sutter Buttes

Tisdale Weir

Butte Slough Near Meridian Gage

Butte Slough

East Borrow Canal

Butte Creek – Sutter Bypass Weir 1 3 ESA / D202001164.00

2. HYDROLOGY

The Butte Slough near Meridian (BSL) DWR gage is the closest surface water gage to the project area (Figure A-1). The BSL gage is upstream of the East-West Diversion weir that diverts flow between the East and West Borrow Canals within the Sutter Bypass. A 60/40 flow split between the east and west canals, respectively, has been reported in previous studies (ICF 2008). Downstream of the East-West Diversion, and upstream of Weir 1, there are several operable weirs (Weir 3 and Weir 5) that divert water for irrigation with limited flow diversion records.

Because of data limitations within the West Borrow Canal, modeled data from the Tisdale Bypass Fish Passage Improvement Project (ESA 2020) was used to assess flow conditions at Weir 1. The Tisdale Bypass Fish Passage Improvement Project used a TUFLOW hydrodynamic model (TUFLOW model) to simulate conditions within the Sutter Bypass and adjacent canals for a period of 22 years (1997 – 2018).

The West Borrow Canal was modeled as a 1-D channel within the TUFLOW model and included weir gate operations for upstream structures. The hydraulic results from the TUFLOW model served as an initial assessment of flow conditions within the West Borrow Canal under several seasons and water year types.

Flow results from the TUFLOW model for several critical and dry years were assessed. Because fish passage is not a concern when the weir and adjacent bypass are inundated, relatively dry water years with minimal overtopping of Tisdale weir were determined to create the most difficult fish passage conditions at Weir 1. Ultimately, TUFLOW model results from water year 2014 were used to determine critical flow rates within the West Borrow Canal within the spring-run Chinook salmon migration window (January through June). Water Year 2014 was a critically dry year with limited inundation of the Sutter Bypass and had no spill events over the Tisdale Weir (Figure A-2). These characteristics are expected to create difficult fish passage conditions at Weir 1.

2. Hydrology.

Butte Creek – Sutter Bypass Weir 1 4 ESA / D202001164.00

Figure A-2

Fremont and Tisdale Weir Spill Plot by Water Year

Butte Creek – Sutter Bypass Weir 1 5 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

TUFLOW flow data within the West Borrow Canal for Water Year 2014 was used to calculate the high-, median- and low-fish passage flows for spring-run chinook (Table A-1). The passage flow values were calculated based on their relevancy to the spring-run adult Chinook salmon. The migration period was refined from prior studies to span January through June based on communication with Tracy McReynolds from CDFW and observations from the Butte Creek Parrot-Phelan Canal Diversion Trap Daily Catch and Effort Summaries published by CDFW in 2021, 2022, and 2023.

TABLE A-1

FISH PASSAGE FLOWS FOR HYDRAULIC MODEL

Flow (cfs) Spring-Run Chinook Salmon

Season Description

356 Low passage flow (90% exceedance for spring-run Chinook salmon)

380 Median passage flow (50% exceedance for spring-run Chinook salmon)

953 High passage flow (5% exceedance for spring-run Chinook salmon)1

1 The recent publication, NOAA Fisheries Pre-Design Guidelines for California Fish Passage Projects, suggests using a 1% exceedance value for the high flow design discharge (NMFS 2023) instead of the 5% exceedance value suggested in prior publications (NMFS 2011). The high flow design discharge can be updated in future phases of the work to use the 1% exceedance flow. The 1% exceedance flow for the WBC based on TUFLOW model results for WY 2014 would be approximately 1,100 cfs.

The fish passage flows were used as the input hydrology for the 2D-HECRAS model. A rating curve derived from the TUFLOW model results was utilized as the downstream boundary condition (Figure A-3).

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Preliminary − Subject to Revision

3. HYDRAULIC ANALYSIS – ALTERNATIVE 0

(NO ACTION)

The HEC-RAS modeling platform (version 6.4.1) was used to develop a 2D quasi-steady hydrodynamic model for the study. The following sections describe how the model was developed.

3.1 Computational domain

The computational domain extended from approximately half a mile upstream of Guisti Weir to approximately half a mile downstream of Weir 1 and extends from levee to levee on the west and east sides. The 2-dimensional domain was discretized within these limits using a nominal mesh cell sizes of 50 feet for the Sutter Bypass and 10 feet for the West Borrow Canal (Figure A-4). A nominal 10-foot mesh was applied to the West Borrow Canal and adjacent wetlands to capture the details of the hydraulics in this area. Additionally, break lines for the top of the levees (on the east and west side), channel banks, and channel centerline were used to help align the mesh faces parallel to the flow.

3. Hydraulic Analysis – Alternative 0 (No Action).

Butte Creek – Sutter Bypass Weir 1 8 ESA / D202001164.00

Figure A-3

Two-Dimensional HEC-RAS Model Downstream Boundary Rating Curve

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SOURCE: Levees (DWR 2012)

N

2D Domain

Mesh Cell Size 10 ft

50 ft

Model Verification Locations

Boundary Conditions

Surveyed Wetland Inverts (ESA 2023)

Sutter National Wildlife Refuge

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-4 Two-dimensional HEC-RAS Model Computational Domain

Sutter Bypass East Borrow Canal

West Borrow Canal

Weir 1

Guisti Weir

Tisdale Bypass

Butte Creek – Sutter Bypass Weir 1 10 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

3.2 Terrain

Several sources of bathymetry and topography data were used to develop the underlying terrain for the existing conditions 2D hydraulic model. Details of the terrain development are described below.

Survey Data In 2020 ESA developed a 1D/2D TUFLOW model of the Sutter Bypass including the East and West borrow canals modeled in 1D. As part of the 2020 Tisdale study, ESA (2020) performed RTK-GPS cross-section surveys to develop 1D cross-sections for the Tisdale model, which had sufficient resolution for answering questions centered around flooding in the Sutter Bypass. For evaluating fish passage at Weir 1, which requires understanding how depth and velocity vary spatially at a resolution small enough to estimate passage width, ESA performed additional RTK-GPS and echosounder surveys to more accurately define bathymetry. After supplementing the data with the CDFW (2020) survey of Weir 1 and the Quantum Spatial (2021) Light Detection and Ranging (LiDAR) survey to represent the island at Guisti Weir the cross-section surveys from ESA (2020) were interpolated and scaled based on the dimensions of the assumed water surface to create supplemental points. The Sutter Bypass was represented using the Central Valley Floodplain Evaluation and Delineation Program (CVFED) LiDAR survey (DWR 2010; Fugro Earth Data 2010; Photo Science 2009) that was used previously in the Tisdale model. Refer to Figure A-5 for the extents of these surveys.

Existing Conditions To create a surface fitting the bathymetry points and edges of the LiDAR, Functional Data Analysis with Partial Differential Equations (fdaPDE)—a bathymetry technique currently used by the DWR Bay-Delta Office (Wang et al. 2018)—was employed to fit a smooth spline through the bathymetry points and supplemental points within the wet area of the LiDAR as well as the shoreline of the CVFED LiDAR to create a smooth transition. Upon completion, fdaPDE was reapplied until both a satisfactory fit was achieved and overfitting artifacts were sufficiently small based on professional judgement. An additional edit to reinforce the weir crest elevation at Weir 1 was applied using the footprint of the PSOMAS (2020) Weir 1 structure survey. Refer to Figure A-6 for the resulting combined surface representing existing conditions and the extent of the interpolation mesh.

ESA (2023)

ESA (2020)

CDFW (2020)

CVFED (2008) LiDAR Shoreline Points

Quantum Spatial (2021)

Supplemental Points

Wet Area

2D Model Domain

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Weir 1 West Notch Dimensions Estimated from PSOMAS (2020) Survey

Guisti Weir

Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-5 Topography and Bathymetry Data Sources

West Borrow Canal

W es t B or ro w

C an al

Ea st

B or ro w

C an al

Weir 1

Guisti Weir

Sutter Bypass

Su tte r B yp as s

Fl ow

Flow

Hughes Road Bridge

Hughes Road Bridge

2D Model Domain fdaPDE Mesh Boundary

Combined Existing Conditions Surface (ft NAVD88)

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61.4

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-6 Existing Conditions Topobathymetry

SOURCE: Existing Elevations (ESA 2023; Quantum Spatial 2021; PSOMAS 2020; CDFW 2020; ESA 2020; DWR 2010; Fugro Earth Data 2010; Photo Science 2009).

West Borrow Canal

Sutter Bypass

Su tte r B yp as s

W es t B or ro w

C an al

Ea st

B or ro w

C an al

Weir 1

Guisti Weir Fl ow

Flow

Hughes Road Bridge

Hughes Road Bridge

Butte Creek – Sutter Bypass Weir 1 13 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

3.3 Roughness

Landcover types and roughness values from the Tisdale Weir Fish Passage Improvement Project TUFLOW model were used within the 2D domain (Table A-2 & Figure A-7). The WBC channel was modeled with a 0.03 roughness (“Toe Drains” landcover category), while the floodplains were modeled with a range of roughness values from 0.06 to 0.1 (Table A-2). The flows assessed with the model are primarily contained in the channel, though under the high passage flow (discussed below in section 2.4) there are several areas where adjacent floodplains are activated.

TABLE A-2

MANNING’S ROUGHNESS FOR HYDRAULIC MODEL

Landcover Manning’s Roughness

Agricultural 0.03

Dense Vegetation 0.1

Medium Vegetation 0.08

Natural Grasses 0.05

Riparian Corridors on Levees 0.06

SNWR Seasonal Marsh 0.04

SNWR Watergrass 0.04

Sparse Vegetation 0.06

Toe Drains 0.03

3.4 Model Verification

Due to data limitations within the West Borrow Canal and the scope of this study, the HECRAS model was not calibrated against real-time data. However, in the absence of calibration the model was verified using the TUFLOW model results and was determined to produce reasonably sufficient results for a comparative analysis of fish passage conditions under the various alternatives.

Verification of the hydraulic model was performed by comparing the 2D HEC-RAS model results with the TUFLOW model time-series results for a flood event from March 4th 2014 to March 21st 2014. This flood event was chosen because of the range of flow includes the passage flows (Table A-1) and flows that are expected to inundate adjacent wetlands.

Water surface elevations were compared for several locations (Figure A-4), upstream and downstream, of Weir 1 between the 2D HECRAS and TUFLOW model results (Figure A-8 & Figure A-9). In general, the 2D HECRAS model underpredicted the water surface upstream of the weir by approximately one foot, and overpredicted the water surface downstream of the weir by approximately one-quarter to one-half of a foot.

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SOURCE: Levees (DWR 2012)

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2D Domain

Landcover Agricultural (n = 0.03)

Dense Vegetation (n = 0.1)

Medium Vegetation (n = 0.08)

Natural Grasses (n = 0.05)

Riparian Corridors on Levees (n = 0.06)

SNWR Seasonal Marsh (n = 0.04)

SNWR Watergrass (n = 0.04)

Sparse Vegetation (n = 0.06)

Toe Drains (n = 0.03)

Levee 0 8,000

Feet

Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-7 Two-dimensional HEC-RAS Model Landcover and Roughness

Sutter Bypass East Borrow Canal

West Borrow Canal

Weir 1

Guisti Weir

Tisdale Bypass

Butte Creek – Sutter Bypass Weir 1 15 ESA / D202001164.00

Figure A-8

Two-dimensional HEC-RAS Model Verification Upstream of Weir 1

Butte Creek – Sutter Bypass Weir 1 16 ESA / D202001164.00

Figure A-9

Two-dimensional HEC-RAS Model Verification Downstream of Weir 1

Butte Creek – Sutter Bypass Weir 1 17 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

The difference in WSE between the TUFLOW and 2D HEC-RAS could be attributed to several factors.

Namely, the representation of the weir in a two-dimensional verses a one-dimensional hydraulic model (i.e. terrain feature vs. explicit weir equations) and the downstream boundary conditions for each model.

The 2D HEC-RAS model uses a rating curve as the downstream boundary conditions that was developed from the TUFLOW model results. In the development of the rating curve a best-fit line was used (Figure A-3), therefore variations in downstream stage between the 2D HEC-RAS model and the TUFLOW model are expected and are likely to influence the stage directly downstream of Weir 1.

Butte Creek – Sutter Bypass Weir 1 18 ESA / D202001164.00

Butte Creek – Sutter Bypass Weir 1 19 ESA / D202001164.00

Preliminary − Subject to Revision

4 HYDRAULIC ANALYSIS – ALTERNATIVES A,

B, AND C

Proposed hydraulic conditions for Alternatives A, B, and C were evaluated using the 2D HEC-RAS model. The model terrain input for each alternative was adapted from the existing conditions terrain model and modified to reflect the proposed improvements. Section 1 summarizes key design elements for each of the respective alternatives. Additional break lines were added for each alternative terrain to reinforce the computational mesh and reflect key grading features. Alternatives 0 and D were assessed on a comparative basis, as their geometries are comparable to several of the modeled alternatives (i.e. the no action alternative is the existing conditions scenario, and an operable weir will have similar hydraulics to the full weir removal scenario when the weir is down and existing conditions when the weir is raised).

Appendix C provides an overview of each alternative’s specific geometry and grading footprints.

4.1 Terrain

Alternative Conditions Surfaces To model proposed conditions, the respective alternative terrain surfaces were creating using the grading tools in Autodesk Civil 3D software and then imported and merged with the existing conditions surface using the RAS Mapper module within the HEC-RAS software. Proposed conditions terrain surfaces were created for alternatives A, B, and C (Figure A-10). A proposed conditions surface was not developed for Alternative D.

4.2 Roughness

Hydraulic roughness for roughened channel (Alternative B) and rock ramp (Alternative C) features were set to a value of 0.05 based on Manning’s n for cobbles and large boulders in mountain streams (Chow 1959). The extent of the increased roughness can be seen in Figure A-10. No additional changes to roughness values were made for the alternative conditions surfaces.

4.3 Channel Bed Sediments

As described in Section 1, Alternative A proposes to remove the weir and fish ladder structures and smooth the channel bed between upstream and downstream bed elevations allowing for unimpeded fish passage. A primary concern with this alternative is that because of the difference in grade between upstream and downstream, the channel may become unstable, incising and widening in response. To assess the potential for channel instability, a characterization of bed sediments in the WBC was required.

On August 23, 2024, ESA collected a series of 5 sediment samples from the bed of the WBC, between Hughes Road to the north and Weir 1 to the south (Figure A-11). Sediment samples were collected via a canoe using a Petite Ponar sampler, which uses a spring loaded, mechanical jaw that snaps shut, capturing loose sediments, once it is dropped onto the channel bed. Sampling in the WBC was complicated by the

4 Hydraulic Analysis – Alternatives A, B, and C.

Butte Creek – Sutter Bypass Weir 1 20 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision presence of consolidated “hardpan” sediments, but the field team was able to collect more recent deposits on top of the hardpan. Two sediment samples were collected at WB3 due to a departure in sediment characteristics relative to other sampling locations.

As seen in Figure A-12 & Table A-3, sediment gradations from the WBC were combined into two groupings: Group 1 comprises the sediments collected from WB1, WB2, and WB4, while Group 2 includes sediments from WB3A and WB3B. These groupings confirm our field observations regarding a change in sediment character at the WB3. Sediments from Group 1 were classified as “silty sand” with a median size class conforming to “medium sand”. Sediments from Group 2 were classified as “silt with sand” with a median size class conforming to “fine silt”. The hardpan bed sediment wasn’t sampled directly, but it’s likely comprised of the fine sediments (silts and clays) observed within these sediment samples, that have settled and consolidated over time.

TABLE A-3

SEDIMENT GRADATION AND CLASSIFICATION

Percentile Group 1 Size (mm)

Group 1 Size Class

Group 2 Size (mm)

Group 2 Size Class

D90 0.81 coarse sand 0.21 fine sand

D85 0.68 coarse sand 0.13 fine sand

D60 0.44 medium sand 0.02 medium silt

D50 0.39 medium sand 0.01 fine silt

D30 0.29 medium sand 0.003 clay

D15 0.13 fine sand

D10 0.04 coarse silt

NOTES: Group 1 (silty sand) = WB1, WB2, and WB4; Group 2 (silt with sand) = WB3A and WB3B

SOURCE: Levees (DWR 2012) th

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-10 Two-dimensional HEC-RAS Model Terrains

Levee (State-Federal SPFC)

Existing Conditions Alternative A Remove Weir

Alternative B Remove Weir with

Roughened Channel

Alternative C Replace Weir with

Rock Ramp

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Weir 1 Headcut

Butte Creek – Sutter Bypass Weir 1 22 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-11

(A) Sediment Sample Locations, (B) Petite Ponar Sediment Sampler, and (C) Sediment Samples

Sutter Bypass

West Borrow Canal

Weir 1

Guisti Weir

Tisdale Bypass

East Borrow Canal

A B

C

Butte Creek – Sutter Bypass Weir 1 24 ESA / D202001164.00

Figure A-12

Sediment Gradations for WBC Sampling Locations

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Preliminary − Subject to Revision

5. MODEL RESULTS

5.1 Fish Passage Assessment

Fish Passage Criteria Table A-4 summarizes the hydraulic criteria used to assess fish passage of each alternative. These criteria were derived from the Yolo Bypass Salmonid Habitat Restoration and Fish Passage Project (DWR, 2017;

USBR, 2017) and the Tisdale Weir Rehabilitation and Fish Passage Project (ESA, 2020).

TABLE A-4

SUMMARY OF FISH PASSAGE CRITERIA

Species

Adult migration time

Minimum flow depth (short distance, <60 ft)

Minimum flow depth (long distance, 60-200 ft)

Minimum channel width

Maximum flow velocity (short distance, <60 ft)

Maximum flow velocity (long distance, 60-200 ft)

Adult sturgeon Jan-May 3 5 10

6 4 Adult salmon Nov-May 1 3 4

SOURCE: DWR, 2017; USBR, 2017

Passage conditions were assessed for alternatives 0, A, B, and C using the 2D HEC-RAS model.

Alternatives B and C each have roughened structures with a length greater than 60 ft. The following figures (Figures A-13 through A-15) depict the depth and velocity predicted by the model for existing conditions and alternatives A, B and C for each passage flow listed in Table A-4.

With design refinement each alternative is expected to provide passage for adult spring run Chinook salmon. Under high passage flow conditions, alternatives A & B provide unrestricted passage for fish as the hydraulic results meet all of the passage criteria. Under the high passage flow conditions, alternative C nearly meets all passage criteria, and the results suggest that with design refinement can be passable by adult Chinook salmon. The hydraulic results have a minimum of one-foot depth at the ramp crest but spans a distance greater than 60 feet and does not pass the passage criteria as designed and modeled.

However, with improvement in the ramp design, and subsequent model refinement, alternative C is expected to provide more favorable passage conditions. The rock ramp was modeled using a continuous roughness, and improvements to the design could include iterating the size and placement of boulders, creating variable roughness along the ramp to increase hydraulic complexity and create a low flow channel with a depth-varying flow path along the ramp and between the boulder crests. An example of boulder crests arrangement is included in Appendix C, though for purposes of this comparative analysis was not included in the HEC-RAS modeling.

5. Model Results.

Butte Creek – Sutter Bypass Weir 1 26 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

Similar to the results of Alternative C for the high passage flow, alternative B for the medium and low passage flows did not meet the passage criteria due to the lack of minimum flow depth. At the upstream end of the roughened channel, the minimum modeled depth is approximately 2.4 ft for the low passage flow for a distance greater than 60 feet. Though this doesn’t meet the passage criteria, the alternative is expected to meet the criteria upon model and design refinement.

5.2 Wetland Activation

There are several wetlands adjacent to the West Borrow Canal in the Sutter National Wildlife Refuge, as depicted in Figure A-4. These wetlands are activated by the West Borrow Canal during instances of overbank (bankfull) flow. Utilizing the 2D HEC-RAS model, the minimum flow rate required to activate the wetlands was estimated for existing conditions and each alternative (Table A-5). Figure A-16 depicts the WSE profiles for the median and high passage flows as well as surveyed wetland inverts surveyed by ESA in 2023. It should be noted that the surveyed wetland inverts are generally one-half to two feet lower than the HEC-RAS existing conditions model surface. The survey conducted by ESA in 2023 captured the invert location along the bank of the WBC. For wetland activation the invert on the WBC bank and wetland itself would need to be inundated, requiring additional flow. The 2D HEC-RAS terrains use LiDAR elevations for the overbank areas including the wetlands which contain thick vegetation which may be classified as ground. Because of this, the minimum required flows for wetland inundation may be lower than what is stated below. More detailed survey data (i.e. wetland boundary and transects) would need to be taken and incorporated in the terrains to provide a more accurate assessment. That said, the flows reported below serve as a comparative tool to assess the various alternatives and their effect on wetland activation.

Using the 2D HEC-RAS model, under existing conditions a discharge of 650 to 750 is required to inundate the various wetlands. Due to broader wetland activation, a discharge of 750 cfs was used to represent the bankfull flow under existing conditions. More discharge (~1000 cfs) is required to activate the wetlands for Alternatives A and B due to removal of the weir, an inline hydraulic control within the WBC. Although Alternative C maintains the existing sill elevation of Weir 1, additional roughness elements (boulders and large cobble on the ramp) downstream of the weir raises the upstream water surfaces profile. Approximately 550 cfs is required to inundate the wetlands under Alternative C.

Although not explicitly modeled, it is expected that Alternative D would result in a similar or slightly higher upstream water surface profile as Alternative C. The water surface profile under Alternative D may be higher due to the slight constriction from the fish ladder and embankment structures.

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-13 Two-dimensional HEC-RAS Model Hydraulic Results

Low Passage Flow (356 cfs)

Velocity ≥ 7 ft/s

6 ft/s ≤ Velocity < 7 ft/s

5 ft/s ≤ Velocity < 6 ft/s

4 ft/s ≤ Velocity < 5 ft/s

Velocity < 4 ft/s

Velocity Categories

Depth ≥ 3 ft

Depth < 1 ft

Depth Categories

Levee (State-Federal SPFC)

Existing Conditions Alternative A Remove Weir

Alternative B Remove Weir with

Roughened Channel

Alternative C Replace Weir with

Rock Ramp

0 200

Feet N

Weir 1 Headcut

West Borrow Canal

Flow

1 ft ≤ Depth < 3 ft

Grading Footprint

Low Flow 356 cfs th

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-14 Two-dimensional HEC-RAS Model Hydraulic Results

Median Passage Flow (380 cfs)

Velocity ≥ 7 ft/s

6 ft/s ≤ Velocity < 7 ft/s

5 ft/s ≤ Velocity < 6 ft/s

4 ft/s ≤ Velocity < 5 ft/s

Velocity < 4 ft/s

Velocity Categories

Depth ≥ 3 ft

Depth < 1 ft

Depth Categories

Levee (State-Federal SPFC)

Existing Conditions Alternative A Remove Weir

Alternative B Remove Weir with

Roughened Channel

Alternative C Replace Weir with

Rock Ramp

0 200

Feet N

1 ft ≤ Depth < 3 ft

Grading Footprint

Median Flow 380 cfs

West Borrow Canal th

: U :\G

IS

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IS

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W

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Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternatives Analysis

Figure A-15 Two-dimensional HEC-RAS Model Hydraulic Results

High Passage Flow (953 cfs)

Existing Conditions Alternative A Remove Weir

Alternative B Remove Weir with

Roughened Channel

Alternative C Replace Weir with

Rock Ramp

0 200

Feet N

High Flow 853 cfs

Velocity ≥ 7 ft/s

6 ft/s ≤ Velocity < 7 ft/s

5 ft/s ≤ Velocity < 6 ft/s

4 ft/s ≤ Velocity < 5 ft/s

Velocity < 4 ft/s

Velocity Categories

Depth ≥ 3 ft

Depth < 1 ft

Depth Categories

Levee (State-Federal SPFC)

1 ft ≤ Depth < 3 ft

Grading Footprint

West Borrow Canal

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Butte Creek – Sutter Bypass Weir 1 31 ESA / D202001164.00 Feasibility Study and Alternatives Analysis April 2024

Preliminary − Subject to Revision

TABLE A-5

ESTIMATED BANKFULL FLOWS AND PERCENT EXCEEDANCES FOR WETLAND INUNDATION

Scenario Estimated Bankfull Discharge

(cfs) Percent Exceedance in WY

2014 (October through July)a

Existing Conditions 750 6

Alternative A 1,000 2

Alternative B 1,000 2

Alternative C 550 10

NOTES:

a Estimated from the TUFLOW model results within the West Borrow Canal. The TUFLOW model simulation period extends from October through July.

In the context of percent exceedance, the flow rates in Table A-5 signify the percentage of time or frequency with which the actual flow exceeds the specified values, informing the estimated inundation in the wetlands during a critical water year. Assessing the TUFLOW model results for water year 2014 shows that the minimum flow to provide wetland inundation occurred approximately 6% of the time under existing conditions, 2% under alternatives A and B, and 10% of the time under Alternative C.

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Figure A-16

Two Dimensional HEC-RAS Model Longitudinal Profiles for the Median and High Passage Flow

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Preliminary − Subject to Revision

5.3 Channel Stability

The “Copeland Method” of stable channel design (Copeland, 1994) was selected to assess the relative stability of the WBC at the Weir 1 location under a full weir removal and natural channel configuration as described in Alternative A. The Copeland Method is applicable to stability investigations for the WBC due to its foundation in the Brownlie sediment transport function, which was calibrated for labile, sand-bed channels (Brownlie, 1981). The Copeland Method uses the Brownlie depth prediction equation and other empirically derived hydraulic geometry relationships to determine stable channel dimensions given an incoming sediment concentration and gradation.

Because no sediment load data is available for this segment of the Butte Creek drainage, incoming sediment concentration was calculated using typical channel dimensions upstream of the weir (supply reach), where:

• Bottom width = 40 feet

• Bank height = 10 feet

• Energy slope = 0.0002 feet/feet

• Left side slope = 4H:1V

• Right side slope = 9H:1V

• Bank roughness (n) = 0.06

A discharge of 1000 cfs was used since the associated water surface profile in the WBC resulted in the initial inundation of most wetlands between the canal and refuge. This discharge represents our preliminary estimate of bankfull or effective discharge under the Alternative A scenario. Because most of the sediments sampled in the WBC could be characterized as “silty sand”, the average of Group 1 sediment gradations were used to define the incoming sediment load, where d84 = 0.68mm, d50 = 0.39mm, and d16 = 0.13mm.

Results of the stability analysis indicate that Alternative A, as currently designed, would not result in aggradation of degradation of the channel. If the channel bottom is gradually transitioned from upstream to downstream, a bed slope equivalent to the average valley and channel slope of 0.0002 feet/feet is achievable. Maintaining the valley slope and average bottom width of 40 feet results in a stable channel design (Figure A-17). This configuration of slope and depth supports channel depths in the ballpark of those observed under existing conditions (Figure A-18). As anticipated, the stability charts indicate that a bed slope steeper than the valley slope may result in degradation (incision) of the channel bed. It is unlikely that the bed slope would flatten below 0.0002 feet/feet if the average channel geometry is maintained throughout the upstream to downstream transition of the channel bed as currently designed.

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Figure A-17

Stability Curve for Width and Slope

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Figure A-18

Stability Curve for Depth and Slope

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6. MODEL LIMITATIONS

The model, validated against the TUFLOW flood flow model, lacks calibration due to insufficient gage data. While this limitation is acceptable for the current feasibility study focused on alternative scenario comparisons, it is crucial to note that calibration, supported by flow and stage gage data, is vital for refining the model's precision, accuracy, and future design development.

In subsequent stages of design, there are several actions that could significantly improve the hydraulic evaluation of Weir 1. The first action includes refining the input hydrology of the WBC, ideally from the collection of flow and stage data which could also be used to calibrate the hydraulic model and refine passage scenario flows. Subsequent model refinement should include the incorporation of gaged hydrology data for passage flows and model calibration, and the incorporation of flow-varied roughness values and spatially varied roughness values throughout any roughened channel features where applicable. If alternative A is selected additional sediment data should be collected to conduct additional stability analyses within the reach. If Alt C is selected, model refinement with gaged data and design iterations of boulder placement and associated roughness will be needed to improve passage hydraulics.

6. Model Limitations.

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7. CONCLUSION

For the purposes of alternative comparisons, the modeling analysis suggests that with refinement Alternatives A, B, and C can all be designed to improve fish passage. Alternatives A and B (full weir removal) may adversely affect adjacent wetlands due to lower water surface in the WCB resulting from removal of the inline hydraulic control at Weir 1. Alternative C however, would maintain a similar water level within the WBC, resulting in no expected effects to the adjacent wetlands.

7. Conclusion.

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8. REFERENCES

Brownlie, W. R. (1981). Prediction of flow depth and sediment discharge in open channels. Report No.

KH-R-43A, California Institute of Technology, W. M. Keck Laboratory, Pasedena, CA, 232 pp.

California Department of Fish and Wildlife (CDFW). 2009. California Salmonid Habitat Restoration Manual, Part XII Fish Passage Design and Implementation. CDFW, Sacramento, CA.

California Department of Fish and Wildlife (CDFW). (2020). Weir 1 survey data. Mark Gard personal communication.

California Department of Water Resources (DWR). (2010). Central Valley Floodplain Evaluation and Delineation (CVFED) Program LiDAR.

California Department of Water Resources (DWR). (2017). Yolo Bypass Salmonid Habitat Restoration and Fish Passage Project: Adult fish passage criteria for federally listed species within the Yolo Bypass and Sacramento River

Chow, V.T., 1959, Open-channel hydraulics, McGraw-Hill Book Co., New York, NY

Copeland, Ronald R. 1994 (Sep). "Application of Channel Stability Methods—Case Studies." US Army Engineer Waterways Experiment Station, Vicksburg, MS. TR-HL-94-11

ESA. 2020. Tisdale Weir Rehabilitation and Fish Passage Project. Flow Analysis – Baseline Model Calibration and Validation Report. Prepared for the California Department of Water Resources, September 2020.

ICF Jones & Stokes (2008). Draft Butte Slough/Sutter Bypass Fish Passage and Entrainment Assessment

NMFS. 2011. Anadromous Salmonid Passage Facility Design, NMFS, Northwest Region, Portland, OR.

NMFS. 2023. NOAA Fisheries Pre-Design Guidelines for California Fish Passage Projects, West Coast Region, Portland, OR.

PSOMAS. (2020). Topographic Survey Tisdale Weir Project Sutter County, California.

U.S. Department of the Interior Bureau of Reclamation (USBR). (2017). Yolo Bypass Salmonid Habitat Restoration and Fish Passage Project: Plan Formulation Report

Quantum Spatial. (2021). Tisdale Bypass, California Lidar Technical Data Report.

8. References.

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Appendix B Preliminary Geotechnical Assessment

Preliminary Geotechnical

Assessment Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternative Analyses

Butte County, CA

November 6, 2023

Prepared under the responsible charge of

Mark H. Stanley

GE 2397

No. 2397

EXP. 09/30/2023

Geotechnical hdrinc.com

Introduction As part of the project team, led by Environmental Science Associates (ESA), HDR is providing this preliminary Geotechnical Assessment that evaluates geologic and geotechnical conditions in the immediate area of Weir 1 located along the west edge of the Sutter Bypass in Butte County, California. The weir is located near the southern boundary of the Sutter National Wildlife Refuge approximately 2,500 feet upstream of the confluence with the Tisdale Weir (Figure 1). This assessment summarizes information gathered and presented in a team presentation on September 22, 2023, which consisted of a site visit and a limited desktop review of available information regarding performance of the Sutter Bypass and geotechnical and geological information in the site vicinity specifically to provide input into the alternative analysis process. Geotechnical exploration or analysis for any of the proposed alternatives was not included as part of this effort.

Background The Sutter Bypass is a constructed water conveyance that transmits excess flows from the Sacramento River to the Feather River. The Sutter Bypass begins west of the town of Sutter and extends in a southeast direction to the Feather River, east of the Town of Nicholaus. The Sutter National Wildlife Refuge was established in 1968 by the California Fish and Game Commission and is located in the northern portion of the bypass, between the Tisdale Weir on the south and McClatchy Road on the north, approximately 5 miles in length. Tisdale Weir is located to the south of the site, a west-east flowing conveyance that also transmits flow from the Sacramento River to the Sutter Bypass. The Sutter Bypass West Levee, adjacent to the wildlife refuge, is maintained by Reclamation District 1660.

Site Condition The bypass is approximately 4,000 feet wide. It was constructed by United States Army Corps of Engineers in the early 1930s across existing farmlands and is contained by earthen levees. The levees were constructed by borrowing soil in long excavations that parallel the toe of the levees.

Weir 1 is located at the southern end of one of these long borrow excavations. A review of Google Earth imagery and other available online aerial imagery shows the delineation of the remnant and current field boundaries inside and outside of the bypass, depicted in Figure 1. Farms in this region have been active for several generations and likely follow surveyed section lines dividing each township into 36 sections that are each 1-mile square, with farms broken into full, half or quarter sections. Therefore, other than excavation of the levee borrow area, the area within the bypass is relatively unchanged.

The available aerial photographs and review of historical topographic maps indicate that the levee west borrow area is approximately 150 feet wide and started (or stopped) at the location of Weir 1, leaving a narrow width (estimated to have once been 50 to 60 feet wide) of native material, likely maintained as farm access from the east to west side of the bypass. The borrow excavation then continued south of this crossing. The borrow cuts were likely made by drag line excavation methods.

Aerial photographs from 2014/2015 show drought low water levels exposing shallow borrow excavation along the east side of the west borrow cut; therefore, the deeper excavation is limited to the western portion of the borrow cut.

Preliminary Geotechnical Assessment Butte Creek - Sutter Bypass Weir 1 Feasibility Study and Alternative Analyses

Figure 1 – Current and former agricultural field boundaries

The west side of the west-east access was later abandoned, and a bridge is located where it crosses the east borrow excavation. The current weir and fish ladder was constructed through the embankment located towards the bypass west bank and an overflow cut weir section (cut weir) excavated to the east of the weir. A small portion of the former remnant embankment is located between the cut weir and the eastern edge of the borrow area. The cut weir appears to have progressed upstream over the years due to backward erosion.

Levee Past Performance and Evaluation A review of available documentation provided little information about the west levee performance. In 1997, the west levee breached north of the wildlife refuge and the levee at the intersection of the bypass and Tisdale Weir was cut to allow flood water to drain out of the Meridian Basin (within RD 1660). Prior historical floods in the region also occurred in 1940, 1955 and 1986. The 1955 flood affected levees located south of the Tisdale Weir but not the west levee adjacent to Weir 1.

The State of California Department of Water Resources (DWR) included an assessment of the bypass levees as part of the Non-Urban Levee Evaluation (NULE) program, documented in a report entitled, “Geotechnical Assessment Report, North NULE Study Area” (URS, 2011). DWR also assessed the east bypass levee as part of the Urban Levee Evaluation (ULE) documented in separate report (URS 2014). For the NULE study no explorations were performed though they likely relied on the exploration program of the east bypass levee and assessed the hazard level for the west levees based on projected performance from the east levee evaluations. The study ranked the flood hazard for each levee using a four-letter Hazard Classification as follows:

• Hazard Level A. When water reaches the assessment WSE, there is a low likelihood of either levee failure or the need to flood-fight to prevent levee failure.

• Hazard Level B. When water reaches the assessment WSE, there is a moderate likelihood of either levee failure or the need to flood-fight to prevent levee failure.

• Hazard Level C. When water reaches the assessment WSE, there is a high likelihood of either levee failure or the need to flood-fight to prevent levee failure.

• Lacking Sufficient Data (Category LD). The segment is currently lacking sufficient data regarding levee past performance or hazard indicators to be able to assign a hazard level, or there is poor correlation between past performance and hazard indicators.

Weir 1 will be inundated during large flood flows in the bypass. However, the assigned hazard level from the NULE study provides insight into the subsurface conditions. Also, the hazard levels look at the entire levee reach as a whole and not any specific location and, therefore, may not be representative of all portions of the levee. The west levee is classified as a Hazard Level C by DWR due to under seepage (ranked the highest hazard risk), stability (ranked the second highest hazard) and erosion (ranked the lowest hazard risk). The overall rank is based on the highest hazard level found for the levee reach. It should be noted that the west levee reach includes the 1997 breach that occurred due to under and through seepage. No other areas of the west levee within the wildlife refuge were noted as having past distress in the available records reviewed in this study.

Surface Geology and Near Surface Conditions DWR performed a detail mapping of the surface geology for each levee area assessed. The mapping is based on a review of aerial photography from 1937. A portion of this map is reproduced as Figure 2. The approximate weir location can be determined based on the agricultural field boundaries shown in in Figure 1.

The near surface geology in the Sutter Bypass area is generally characterized as follows:

• Fine-grained Holocene basin and/alluvium deposits overlie coarser late Pleistocene deposits of the Modesto and Riverbank formations.

• Typically, a well-developed soil with impervious horizons (hardpan) is found at the top of the late Pleistocene deposits, the basin and/or alluvium deposits from the underlying coarser deposits.

• Fine-grained basin and/or alluvium deposits and the hardpan generally have much lower hydraulic conductivity than the underlying late Pleistocene deposits.

More recent Holocene aged and historical channel deposits (map units Hch and Rch) are incised into the basin deposits. These southwest-trending alluvial channel deposits locally underlie the bypass levee and result in local differences in material textures beneath the levee. The mapped channels are about 250 feet wide. In this area, the channels are estimated to be about 6 to 8 feet deep, and are typically filled with sand, silt, and clay in a fining-upward sequence, i.e., coarser-grained and overlain by about 1 to 2 feet of silt and clay. This sedimentary sequence may be conducive to seepage where relatively more-permeable channel sands are overlain by a relatively thin, fine-grained blanket layer (Source URS 2014).

A review of Figure 2 suggests that the incised channel deposits were not mapped beneath the west levee and may be a factor in the lack of notable levee performance issues in this immediate area.

Figure 2 – Surface geology, excerpt (URS 2011), weir location approximate, no scale

The DWR-sponsored geotechnical investigations for the bypass east levee indicate that there is a fine-grained lower permeability blanket layer overlying coarser late Pleistocene deposits. Due to their age, layers of very hard soil, or hard pan, can develop and were identified in the east levee exploration performed within this reach of the bypass. The borrow excavations would have extended through the hardpan layers.

After performing a review of available area photography and the available information from prior studies, the following can be concluded regarding current site conditions:

• The central portion of the wildlife refuge is substantially unchanged from the original farming section and subsection boundaries.

• Weir 1 is constructed on an access road remnant that extended across the refuge, and the access is still in use (bridge) at the east levee borrow area.

• The southern limit of east dragline borrow cut is deepest parallel to the levee with a shallower, variable width bench to the east exposed in 2014/2015.

• Near vertical borrow cut slopes are still in place along both the east and west cut banks.

• The weir head cut section may be formed along the top of the hardpan layer (approx. Elev.

+27 feet) with the weir extending into the underlying stiff to hard clay and silt.

Weir 1

Proposed Weir Alternatives The project has evaluated several weir replacement alternatives consisting of:

• Alternative A - Weir Removal

• Alternative B - Roughened Channel

• Alternative C - Partial Weir Removal with Rock Ramp

• Alternative D - Operable Weir and Fish Ladder

For this assessment, only two alternatives were considered (Alternatives B and C) as presented in Figure 3.

Figure 3 – Alternatives B and C (Source ESA, 2023)

HDR developed the following geotechnical conclusions considering the above information.

Alternative B: Roughened Channel Pro

• Removes remnant barrier and weir.

• Provides continuity for flow.

• Does not impact west side of borrow cut along toe of levee with placement of erosion protection.

• Uniform surface elevation will not create a potentially adverse seepage condition along the channel.

• Fill thickness is limited.

• Foundation primarily in cut…