Yolo Bypass Comprehensive Study

Study Overview

Problem & Need

The complexities of water management in California are increasing as we face dramatic swings between flooding and drought. The Sacramento River Basin—vital to the nation's 5th largest economy—contains one of the highest residual flood risks in the country. 

Project Scope

The Yolo Bypass is a 40-mile-long federal flood management facility spanning from the Fremont Weir to the Sacramento-San Joaquin Delta. For over a century, local, state, and federal partners have worked to safely develop this region. Today, escalating demands require action to further reduce flood risks, restore natural habitats, improve fish passage, and secure water supply reliability. 

Study Overview

Authorized by Congress through the Water Resources Development Act of 2020 (WRDA), the United States Army Corps of Engineers (USACE) is conducting a Comprehensive Study of the Yolo Bypass system to evaluate flood risk management, ecosystem restoration, water supply, and recreation. 

USACE is consulting with the State of California, applicable federal, state, and local agencies, Tribal nations, non-federal interests, the Yolo Bypass Cache Slough Partnership, and other stakeholders.

iconCalifornia Department of Water Resources (DWR)’s is performing project management on behalf of the CVFPB, including managing the State’s financial contribution to the Study.
 
What will the study deliver?

The Comprehensive Study will develop actionable recommendations for the region's future, which may include:

iconAdaptive Management: Enhanced monitoring and optimization of the existing Yolo Bypass System.

iconNew Infrastructure & Restoration: Follow-on activities to design and construct modernized flood risk management and aquatic ecosystem features.

iconFuture Feasibility: Identifying pathways and new water resource development projects that complement the bypass's authorized purposes.

 

Benefits of the Yolo Bypass

The Yolo Bypass plays a crucial role in protecting the Sacramento region from flooding. It is also central to a significant agricultural economy, a critical water supply delivery system, and an ecosystem of national significance: 


iconFlood Risk Management

Conveys 80% of Sacramento River watershed flows during floods, reducing risk to approximately 950,000 people, 284,000 structures, and $150 billion in critical infrastructure.  


 iconEcosystem of National Significance

The bypass supports 22 threatened and endangered species and is a key stopover on the Pacific Flyway supporting millions of waterfowl annually. The entire bypass, and particularly the 16,800-acre Yolo Bypass Wildlife Area, provides habitat for over 200 bird species. 

The Fremont Weir Wildlife Area provides grassland and riparian habitat. In addition, the bypass is uniquely situated along the migration corridor for federally protected salmon, steelhead, and sturgeon.  

 

iconAgricultural Economy

The Yolo Bypass contains approximately 47,000 acres of agricultural land, making it an important contributor to the nation’s food supply and economy. The surrounding counties of Yolo, Solano, and Sacramento have more than 900,000 acres of farmland in production within the area served by the Sacramento River Flood Control System.   


iconWater Supply Delivery System

Portions of the Yolo Bypass serve as mitigation areas for the State Water Project and Central Valley Project, which provide drinking water to nearly 27 million Californians and irrigation to 2.5 million acres of agricultural land.  


iconRecreation

The Yolo Bypass provides local and regional recreation, tourism, and environmental education opportunities including hiking, fishing, hunting, wildlife viewing, and boating. There are three wildlife areas managed by the California Department of Fish and Wildlife: Yolo Bypass Wildlife Area, Fremont Weir Wildlife Area, and Sacramento Bypass Wildlife Area.  

Map

History

Pre-1849 (Natural Basin): Prior to federal flood management and extensive settlement, the Yolo Basin was a naturally occurring, high-value wetland system in the Lower Sacramento River system. The Yolo Basin was primarily natural land, with limited development and high habitat value. It also has a deep history of cultural significance to 15 Native American Tribes.

The Reclamation Era: As part of the Sacramento River Flood Control Project, the Yolo Basin was reclaimed and de­veloped primarily as farmland. Over the last 100 years, it has functioned primarily as a sin­gle-purpose flood-control facility, with other uses largely restricted.

Modern Recognition: In 2019, Congress designated the Sacramento-San Joaquin Delta as a National Heritage Area (NHA) to preserve its cultural, historical, and agricultural value. The Delta Protection Commission is the local coordinating entity for the NHA. 

Documents & Reports

Sept. 2, 2026 Public Meeting Slides

 

Draft Interim Integrated Comprehensive Feasibility Report and Draft Environmental Assessment Documents

 

Draft Interim Integrated Comprehensive Feasibility Report and Draft Environmental Assessment (August 2026)

Draft FONSI

 

Appendix A 

Appendix A - Public Involvement

Appendix A Enclosure 1 - Cooperating Agency Invitation Letters and Responses

Appendix A Enclosure 2 - Interagency Meeting Files Combined

Appendix A Enclosure 3 - Letters to Tribal Nations

Appendix A Enclosure 4 - Join us for a Yolo Comp Study Public Meeting on 7 July 2025

Appendix A Enclosure 4 - Yolo Bypass Comp Study Public Meeting Presentation Slides_7 July 2025

Appendix A Enclosure 5 - Fact Sheet Yolo Comp Study

 

Appendix B 

Appendix B - Engineering

Appendix B1-HH

Appendix B1-HH_Enclosure - Plates

Appendix B2_Attachment B-2-1 SQRA Method Index Points

Appendix B2_Attachment B-2-2 LST 2.0 Method Index Points

Appendix B2_Attachment B-2-3 CVFPP Adapt Method Index Points

Appendix B2_Attachment B-2-4 Select Background and Supporting Documents

Appendix B2_Geotechnical

 

Appendix C

Appendix C_Cost Engineering

 

Appendix D

Appendix D1_Draft Monitoring and Adaptive Management Plan

Appendix D2_Draft HEP Methodology Report

Appendix D3_Draft Fish and Wildlife Coordination Act Recommendations

Appendix D4_ESA Compliance_Draft Outline BAs

Appendix D5_Draft CWA Compliance

Appendix D6_CAA Draft Preliminary Modeling

Appendix D6_Enclosure_Draft Quantities for Emissions Modeling

Appendix D6_Enclosure_Draft RoadConstructionEmissionsModel_Final Alt 1

Appendix D6_Enclosure_Draft RoadConstructionEmissionsModel_Final Alt 1_Operations and Maintenance

Appendix D6_Enclosure_Draft RoadConstructionEmissionsModel_Final Alt 2

Appendix D6_Enclosure_Draft RoadConstructionEmissionsModel_Final Alt 2_Operations and Maintenance

Appendix D6_Enclosure_Draft_USACE PEAT-Project Emissions Analysis Tool_Final Alt 1 and 2

Appendix D7_Draft Avoidance and Minimization Measures

Appendix D8_NRCS Coord FPPA_1981_FCIR CPA106_Yolo Bypass Comprehensive Study_07092026

 

Appendix F

Appendix F_Economic and Social Considerations

 

 

Review Plan Documents
Approval Memo (October 2024)
Review Plan (September 2024)
Endorsement (June 2024)

Frequently Asked Questions

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Expand List item 41503Collapse List item 41503  What is the status of the Yolo Bypass Comprehensive Study?

The study has successfully achieved the selection of the Tentatively Selected Plan (TSP). Following selection TSP, USACE releases the draft interim integrated comprehensive feasibility report and environmental assessment for a public review and comment period. Concurrently, USACE conducts rigorous technical review to verify the study’s scientific, engineering, and economic integrity while ensuring full compliance with federal laws, executive orders, and civil works policies.

Expand List item 41504Collapse List item 41504  Will the study result in immediate construction or operational changes in the Bypass?

No. Once the Study is complete and an alternative is recommended, it must go to the U.S. Congress for consideration for authorization typically through the biannual Water Resources Development Act (WRDA). Following authorization, additional appropriations are needed before further engineering, design, and construction begins. 

Expand List item 41505Collapse List item 41505  When will the study be completed?

As currently planned, the Yolo Bypass Comprehensive Study will take at least 5.5 years to complete. The Study began in 2023. 

Expand List item 41506Collapse List item 41506  Will the public have opportunities to provide input on the study?

Yes. Community input is essential to the Study. Early outreach began in July 2025. Notice of future public engagements will be provided by USACE and the non-federal sponsors. 

The next public meeting is on Sept. 2, 2026 at 10:30 to 11:30 a.m. and 6:30 to 7:30 p.m. via Microsoft Teams. For more information on the meeting agenda or how to access the meeting, view the Public Meeting Notice. To receive notification about future meetings, send an e-mail to be added to the study’s distribution list: CESPK-YOLOBypass@usace.army.mil.

Public comments on the draft feasibility report and environmental assessment can also be sent to CESPK-YOLOBypass@usace.army.mil.

Expand List item 41507Collapse List item 41507  How are we engaging with local tribes?

USACE is committed to meaningful, early, and ongoing engagement with Tribal Nations and Tribal communities throughout the feasibility study process. Consistent with the USACE Civil Works Tribal Consultation Policy (2023), Tribal coordination and consultation provide opportunities for Tribes to their knowledge, identify concerns, and inform planning. 

USACE initiated Tribal coordination by hosting an inter-Tribal charrette to introduce the study purpose, planning process, and schedule. Tribal Nations were also invited to participate as Cooperating or Participating Agencies under the National Environmental Policy Act and as consulting parties under Section 106 of the National Historic Preservation Act, as appropriate.  

USACE continues engagement through inter-Tribal workshops that provide study updates, discuss milestones, and gather Tribal perspectives on study alternatives, cultural and natural resources, and opportunities to avoid, minimize, or mitigate potential impacts. A virtual site visit further supported discussions of planning alternatives and areas of Tribal interest. 

Tribal perspectives are considered alongside engineering, environmental, economic, and other planning factors to inform the development and evaluation of the study alternatives. 

For more information on our Tribal Nations Program, visit: https://www.spk.usace.army.mil/Missions/Tribal-Nations-Program/  

Expand List item 41508Collapse List item 41508  How will the study impact flood risk management and land use planning in the future?

Findings of the Yolo Bypass Comprehensive study will serve as an important information resource to local, regional, and state agencies when making vital flood risk management decisions.

Expand List item 41509Collapse List item 41509  Who is funding the study?

The Study is funded through a feasibility cost share agreement signed in September 2023 between USACE, CVFPB, and SAFCA. DWR works with CVFPB on behalf of the State of California consistent with a Memorandum of Understanding between the agencies. 

Expand List item 41628Collapse List item 41628  What is an Environmental Assessment under the National Environmental Policy Act?

An Environmental Assessment is a concise public document that provides sufficient evidence and analysis for determining whether the action agency (in this case USACE) should issue a Finding of No Significant Impact or prepare an Environmental Impact Statement. It is designed to help public officials make decisions that are based on an understanding of the environmental consequences of the proposed action.