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2017 Flood System Status Report
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2017 Flood System Status Report
Department of Water Resources | August 10, 2017...
Summary
This report is intended to assist flood management planners and engineers in characterizing facilities within the State Plan of Flood Control (SPFC) and...
This report is intended to assist flood management planners and engineers in characterizing facilities within the State Plan of Flood Control (SPFC) and to inform the 2017 Central Valley Flood Protection Plan Update (2017 CVFPP Update). The 2017 FSSR provides a concise repository of the status of SPFC Facilities as noted in related DWR evaluation and inspection efforts, along with the efforts of our local and federal partners. The 2012 CVFPP laid the foundation necessary for compliance with the Central Valley Flood Protection Act of 2008 and a new approach to flood management in the Central Valley.

As a supporting and informational document to the 2017 CVFPP Update, the 2017 FSSR includes information about inspecting and evaluating SPFC facilities. It also details and quantifies major components of existing flood risk within the Sacramento and San Joaquin river watersheds, and the factors that influence flood risk in relation to the various flood control structures within the SPFC. Additionally, the 2017 FSSR informs and details the current conditions of levees and channels within the SPFC, and includes finalized project information from DWR’s Levee Evaluations Program. Through updating the status of SPFC facilities, the State of California can continue to make informed decisions related to flood risk management.

This document is a collaborative effort by DWR, local, and federal partners, signifying a step forward in gaining deeper understanding of the flood system’s current status and condition in the Central Valley.

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Adapting California’s Water Management to Climate Change
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Adapting California’s Water Management to Climate Change
Public Policy Institute of California | January 12, 2009...
Summary
Among the potential impacts of climate change, accelerated sea level rise and a reduced Sierra snowpack are the most certain. Both will pose...
Among the potential impacts of climate change, accelerated sea level rise and a reduced Sierra snowpack are the most certain. Both will pose significant challenges for water supply and flood management. Water utilities have already begun to plan for these changes, but flood control agencies are lagging behind and face greater regulatory constraints. State leadership is needed to resolve some threats, including the risk of catastrophic failure in the Sacramento-San Joaquin Delta. This report was prepared as part of the Preparing California for a Changing Climate project.

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California’s Flood Future: Recommendations for Managing the State’s Flood Risk
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California’s Flood Future: Recommendations for Managing the State’s Flood Risk
Department of Water Resources | November 1, 2013...
Summary
California is at risk for catastrophic flooding that could have wide-ranging impacts due to the size of its economy and the number of...
California is at risk for catastrophic flooding that could have wide-ranging impacts due to the size of its economy and the number of people residing in the state. The State’s economy ranks ninth globally; therefore, the consequences associated with its potential exposure to property damage, economic harm, and loss of life are great.

California is the nation’s most populous state, ranks third largest in land size, and has widely varying climates and topographies, all of which make developing one-size-fits-all solutions to flood risk management impracticable.

In California, 20 percent of the almost 38 million residents live within 500-year floodplains (i.e., have a 0.2 percent chance of flooding in a given year). Four of the nation’s 15 largest cities are in California (Los Angeles, San Diego, San Jose, and San Francisco), and all are at risk for some type of flooding. These factors make decisions regarding California’s flood risk management policies and financial investments vital to the State and the nation.

This report, California’s Flood Future: Recommendations for Managing the State’s Flood Risk (Flood Future Report) presents an overview of the flood threats facing the state, approaches for reducing flood risk, and recommendations for managing California’s flood risk. The Flood Future Report is the first statewide report to be developed through collaboration between the California Department of Water Resources (DWR) and the United States Army Corps of Engineers (USACE). As a joint report by the State and Federal governments, the document represents an unprecedented level of intergovernmental cooperation, including tribal entities.1 Additionally, this report would not have been possible without the participation of and information shared by more than 140 local flood management agencies.

The Flood Future Report represents the first characterization of flood management activities and exposure to flood hazard throughout each county and hydrologic region of the state. This statewide assessment is intended to provide valuable information for local, State, and Federal decision makers as they chart California’s complex flood management future.

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California’s Water: Preparing for Floods
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California’s Water: Preparing for Floods
Public Policy Institute of California | October 1, 2016...
Summary
One in five residents and billions of dollars in assets are vulnerable to flooding. Climate change brings new vulnerabilities. This brief describes new...

One in five residents and billions of dollars in assets are vulnerable to flooding. Climate change brings new vulnerabilities. This brief describes new tools and approaches that can reduce these risks.

This publication is part of a briefing kit that summarizes a dozen of the state’s most pressing water management issues.

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Central Valley Flood Protection Plan (2012)
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Central Valley Flood Protection Plan (2012)
Department of Water Resources | June 12, 2012...
Summary
The Central Valley Flood Protection Plan (CVFPP) is a critical document to guide California’s participation (and influence federal and local participation) in managing...
The Central Valley Flood Protection Plan (CVFPP) is a critical document to guide California’s participation (and influence federal and local participation) in managing flood risk along the Sacramento River and San Joaquin River systems. The CVFPP proposes a system-wide investment approach for sustainable, integrated flood management in areas currently protected by facilities of the State Plan of Flood Control (SPFC).

The CVFPP will be updated every five years, with each update providing support for subsequent policy, program, and project implementation.

The State of California (State) conducted planning and investigations for the 2012 CVFPP from 2009 through 2011, representing the most comprehensive flood evaluations for the Central Valley. Following the anticipated adoption of the CVFPP in 2012 by the Central Valley Flood Protection Board (Board), preparation of regional- and State-level financing plans will guide investments in the range of $14 billion to $17 billion during the next 20 to 25 years. These financing plans are critical to CVFPP implementation, given the uncertainty in State, federal, and local agency budgets and cost-sharing capabilities.

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Central Valley Flood Protection Plan Update 2017
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Central Valley Flood Protection Plan Update 2017
Department of Water Resources | August 29, 2017...
Summary
The Central Valley Flood Protection Plan (CVFPP) has guided the State’s participation in managing flood risk in areas protected by the State Plan...
The Central Valley Flood Protection Plan (CVFPP) has guided the State’s participation in managing flood risk in areas protected by the State Plan of Flood Control (SPFC) since the plan’s adoption pursuant to the Central Valley Flood Protection Act of 2008 in 2012. A strategic, long-range plan, the CVFPP and its updates describe a programmatic vision for flood system improvements over time in accordance with the requirements of the 2008 Act.

The CVFPP was prepared by the Department of Water Resources (DWR) and adopted by Central Valley Flood Protection Board (CVFPB) through Resolution 2012-25. As conceived by the legislature, the CVFPP is updated every 5 years, beginning in 2017.

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Central Valley Flood Protection Plan: Conservation Strategy

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Central Valley Flood Protection Plan: Conservation Strategy
Department of Water Resources | August 8, 2017...
Summary
In the Central Valley of California, flood risks, water supplies, and the functioning of ecosystems are linked, with actions in one area affecting...
In the Central Valley of California, flood risks, water supplies, and the functioning of ecosystems are linked, with actions in one area affecting the other areas. The majority of flows that pass through the State Plan of Flood Control (SPFC) are regulated by reservoirs operated for flood management, water supply, water quality, power generation, wildlife and fisheries habitat, and recreation. Similarly, the system of river and bypass channels, levees, and water control structures in the Central Valley does more than just contain floodwaters that previously flooded the valley floor for months at a time. It supports agricultural uses in the bypasses, serves as valued recreational areas and open space, helps in the management of surface water supplies and management of groundwater and water quality, and provides critical remnant riparian and floodplain habitats for numerous fish and wildlife species.

The Central Valley Flood Protection Plan (CVFPP) recognizes these interconnections in its approach to flood management. The CVFPP is a long-term planning document that provides a framework for prioritization of investments in the SPFC. It seeks to improve flood risk management (the primary goal), as well as improve operations and maintenance (O&M), promote ecosystem functions, improve institutional support, and promote multi-benefit projects where feasible (supporting goals) (California Department of Water Resources [DWR] 2012a).

This Conservation Strategy (or Strategy) is an integral part of the CVFPP. It supports the attainment of all CVFPP goals, but focuses on the improvement of ecosystem functions through the integration of ecological restoration with flood risk reduction projects where feasible. This Conservation Strategy, including Appendices A?L, describes the basis for recommending various conservation actions and setting long-term objectives for the Central Valley flood management system as a whole. The integration of specific environmental restoration features with DWR’s proposed flood management system improvements is summarized in Chapters 2 and 3 of the CVFPP and will also be described further in the 2017 CVFPP update and supporting documents, such as the Sacramento River Basin-Wide Feasibility Study (BWFS) and the San Joaquin River BWFS.

The Conservation Strategy and CVFPP as a whole would contribute to achieving the California Water Action Plan’s overarching goals of reliability, restoration, and resilience (California Natural Resources Agency, California Department of Food and Agriculture, and California Environmental Protection Agency 2015, 2016). In particular, this Strategy and the CVFPP as a whole are integral to three of the 10 “key actions” identified in the California Water Action Plan:

Increase flood protection.
Protect and restore important ecosystems.
Increase operational and regulatory efficiency.

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Changing Channels: Regional Information for Developing Multi-benefit Flood Control Channels at the Bay Interface
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Changing Channels: Regional Information for Developing Multi-benefit Flood Control Channels at the Bay Interface
San Francisco Estuary Institute | May 26, 2017...
Summary
Over the past 200 years, many of the channels that drain to San Francisco Bay have been modified for land reclamation and flood...
Over the past 200 years, many of the channels that drain to San Francisco Bay have been modified for land reclamation and flood management. The local agencies that oversee these channels are seeking new management approaches that provide multiple benefits and promote landscape resilience. This includes channel redesign to improve natural sediment transport to downstream bayland habitats and beneficial re-use of dredged sediment for building and sustaining baylands as sea level continues to rise under a changing climate.

Flood Control 2.0 is a regional project that was created to help develop innovative approaches for integrating habitat improvement and resilience into flood risk management at the Bay interface. Through a series of technical, economic, and regulatory analyses, the project addresses some of the major elements associated with multi-benefit channel design and management at the Bay interface and provides critical information that can be used by the management and restoration communities to develop long-term solutions that benefit people and wildlife.

This Flood Control 2.0 report provides a regional analysis of morphologic change and sediment dynamics in flood control channels at the Bay interface, and multi-benefit management concepts aimed at bringing habitat restoration into flood risk management. The findings presented here are built on a synthesis of historical and contemporary data that included input from Flood Control 2.0 project scientists, project partners, and science advisors. The results and recommendations, summarized below, will help operationalize many of the recommendations put forth in the Baylands Ecosystem Habitat Goals Science Update (Goals Project 2015) and support better alignment of management and restoration communities on multi-benefit bayland management approaches.

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Delta Levees – Types, Uses, and Policy Options
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Delta Levees – Types, Uses, and Policy Options
Delta Vision | August 7, 2008...
Summary
This document was developed to support Delta Vision discussions on the role of levees in the Delta’s future. It is to clarify the...
This document was developed to support Delta Vision discussions on the role of levees in the Delta’s future. It is to clarify the different types (or design standards) of levees that now exist for the Delta and what improvements could be considered. It is especially oriented toward an improved understanding of what types of levees are suitable for protecting various land uses or for other applications.

Based on understanding the levee types, policy options are identified for a) selecting levee improvements to be included in the vision of the Delta’s future and b) implementing the improvements selected.

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Delta Region Integrated Flood Management: Key Considerations and Statewide Implications
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Delta Region Integrated Flood Management: Key Considerations and Statewide Implications
California Department of Water Resources (DWR) | September 1, 2012...
Summary
This Background / Reference Memorandum (BRM) presents highlights from flood-related technical, legislative and funding information regarding the Sacramento-San Joaquin Delta (Delta), with emphasis...
This Background / Reference Memorandum (BRM) presents highlights from flood-related technical, legislative and funding information regarding the Sacramento-San Joaquin Delta (Delta), with emphasis on activities by the California Department of Water Resources (DWR).

The BRM is intended to provide historical and existing conditions (year 2011) context for DWR’s use in conveying strategies for future investments in integrated flood management in the Delta under a separate document.

The State of California has entrusted DWR as the agency with the responsibility for managing water flow through the Delta and for representing State interests in Delta levees.

DWR invests in the Delta levee system to protect clear and identifiable State interests, including but not limited to:
• Human life, public health, and property within the Delta;
• Water quality and water supply for agriculture, ecosystem, and municipal and industrial water users within the Delta and water users outside of the Delta;
• Ecosystem protection and enhancement, including protection and recovery of threatened and endangered species;
• Critical infrastructure such as highways, railroads, aqueducts, and pumping plants;
• Other infrastructure such as transmission lines (electric & petroleum), shipping channels, and public infrastructure (water and wastewater treatment plants);
• Agriculture and recreation; and
• Cultural, historical, aesthetic, and other values included in “Delta as a place.”

State legislation and modifications to the California Water and Public Resources codes have repeatedly demonstrated the State’s interest in preserving the Delta and the importance of Delta levees. The legislation and modifications to the codes have made strong statements about the importance of the Delta, provided direction for the DWR’s levee programs, and provided funding for flood management activities and environmental stewardship in the Delta.

This BRM should be considered a reference document. Due to the large number of existing documents on the Delta and its levees, this BRM provides highlights of important material with references to other documents for more detailed information.

This base information should be useful when considering modifications to investment strategies for integrated flood management in the Delta.

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Emergency Response To Flood Threats in California
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Emergency Response To Flood Threats in California
Department of Water Resources | April 8, 2011...
Summary
An explanatory memo on the Flood Operations Branch, Department of Water Resources, Division of Flood Management During the flood season, a number of...
An explanatory memo on the Flood Operations Branch, Department of Water Resources, Division of Flood Management

During the flood season, a number of public agencies combine their efforts to provide high water warnings and minimize flood damage in California. The Department of Water Resources (DWR) is responsible for coordinating local, State and federal flood operations. The State-Federal Flood Operations Center, located on El Camino Avenue in Sacramento, is the focal point of this effort. State, federal and local flood operations on the North Coast streams are coordinated through the DWR Eureka Flood Center in Humboldt County.

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Flood Control System Status Report
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Flood Control System Status Report
Department of Water Resources | December 12, 2011...
Summary
This Flood Control System Status Report (FCSSR) describes the current status (physical condition) of SPFC facilities at a systemwide level. DWR prepared the...
This Flood Control System Status Report (FCSSR) describes the current status (physical condition) of SPFC facilities at a systemwide level. DWR prepared the FCSSR to meet the legislative requirements of California Water Code Section 9120, and to contribute to development of the Central Valley Flood Protection Plan (CVFPP). The CVFPP will guide future State investments through projects to address identified problems in the SPFC.

The FCSSR is primarily intended to present information on the physical condition of SPFC facilities, and to help guide future inspection, evaluation, reconstruction, and improvement of the facilities. Information contained in the FCSSR should not be used to predict how a levee orassociated facilities may perform in a specific flood event. More detailed information (such as additional geotechnical explorations and analyses at a greater frequency) would be necessary to meet other purposes, such as assessing whether a levee could be certified under Federal Emergency Management Agency (FEMA) standards to provide base flood protection under the National Flood Insurance Program.

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Flood Management (Resource Management Strategy)
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Flood Management (Resource Management Strategy)
Department of Water Resources | July 29, 2016...
Summary
This resource management strategy report for flood management is unique to the other resource management strategies in that it contains multiple approaches within...
This resource management strategy report for flood management is unique to the other resource management strategies in that it contains multiple approaches within a single resource management strategy report.

Flood management is complex and still relatively new. This flood management strategy provides local and regional water managers a broader perspective of the flood management tools that are available and their interrelationships within one report. In future updates to this resource management strategy report and as flood management becomes more integrated more than one resource management strategy report for flood management could be developed.

This flood management resource management strategy report has been subdivided into four approaches:
• Nonstructural.
• Restoration of natural floodplain functions.
• Structural.
• Flood emergency management.

The report discusses flood management in general terms followed by specific subsections related to the four approaches identified above, as necessary.

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Flood-Risk Reduction and Resilience: Federal Assistance and Programs
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Flood-Risk Reduction and Resilience: Federal Assistance and Programs
Congressional Research Service | November 15, 2017...
Summary
Recent flood disasters have raised congressional and public interest in not only reducing flood risks, but also improving flood resilience, which is the...
Recent flood disasters have raised congressional and public interest in not only reducing flood risks, but also improving flood resilience, which is the ability to adapt to, withstand, and rapidly recover from floods.

In the United States, flood-related responsibilities are shared. States and local governments have significant discretion in land-use and development decisions, which can be major factors in determining the vulnerability to and consequence of hurricanes, storms, extreme rainfall, and other flood events. Congress has established various federal programs that may be available to assist U.S. state, local, and territorial entities and tribes in reducing flood risks.

Among the most significant federal activities to reduce communities’ flood risks and improve flood resilience are

? assistance with infrastructure projects (e.g., levees, shore protection) and other flood mitigation activities that save lives and reduce property damage; and
? mitigation incentives for communities that participate in the National Flood Insurance Program (NFIP).

This report provides an overview of these assistance programs and the NFIP-related mitigation incentives; it also raises flood-related policy considerations associated with federal programs and practices.

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Handbook for Assessing Value of State Flood Management Investments
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Handbook for Assessing Value of State Flood Management Investments
Department of Water Resources | June 8, 2014...
Summary
Millions of people and over half a trillion dollars in assets are exposed to flood risk in California (DWR 2013a). This remains the...
Millions of people and over half a trillion dollars in assets are exposed to flood risk in California (DWR 2013a). This remains the case even as State, federal, and local flood management agencies have worked for decades to reduce the risk and consequences of flooding in the State. The people of California have shown that they understand the increasing flood risk due to population growth, environmental concerns, climate change, and land use practices, and they are willing to invest in flood risk management projects.

This requires the public agencies responsible for California’s flood risk management to demonstrate the value of those investments both before and after they are implemented. This Handbook for Assessing Value of State Flood Management Investments (HAV) supports that effort.

The California Department of Water Resources (DWR) has identified foundational goals that shape the State’s water management investment strategy.

Those goals are:

Improving public safety
Fostering environmental stewardship
Supporting economic stability

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Implementing California Flood Legislation into Local Land Use Planning: A Handbook for Local Communities
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Implementing California Flood Legislation into Local Land Use Planning: A Handbook for Local Communities
Department of Water Resources | October 1, 2010...
Summary
The potential for flooding is a significant risk for many localities in California. Flood events can cause substantial economic, social, and environmental damage....
The potential for flooding is a significant risk for many localities in California. Flood events can cause substantial economic, social, and environmental damage. In addition, many flood management practices can be costly and have considerable effects on the environment. One of the most effective ways to reduce the vulnerability to potential flooding is through careful land use planning that is fully informed by and reflective of applicable flood information and flood management practices. This Handbook supports the Department of Water Resources (DWR) FloodSAFE California initiative, which is a statewide initiative to improve public safety through an integrated approach to flood management.

Several bills were signed by Governor Schwarzenegger in 2007 adding to and amending State flood and land use management laws. These new laws are intended to improve local land use and other planning decisions by strengthening the link between land use and flood management. The laws contain requirements and considerations that outline a comprehensive approach to improving flood management at the State and local levels.

This Handbook includes the 2007 California flood risk management legislation affecting cities’ and counties’ responsibilities related to local planning requirements such as general plans, zoning ordinances, development agreements, tentative maps, and other actions. It does not address all flood management related legislation passed in 2007. For a complete summary of California flood legislation passed in 2007, refer to the 2007 California Flood Legislation Summary and Companion Reference issued by DWR at http://www.water.ca.gov/legislation/2007-summary.
pdf and http://www.water.ca.gov/legislation/2007-reference.pdf.

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Managing Floods in California
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Managing Floods in California
Legislative Analyst's Office | March 22, 2017...
Summary
This report is intended to provide basic information about floods and flood management in California. (Whereas previous generations referred to “flood control” or...
This report is intended to provide basic information about floods and flood management in California. (Whereas previous generations referred to “flood control” or “flood prevention” activities, experts now prefer the term “flood management” in acknowledgement that floodwaters are recurring and inevitable.) We begin by summarizing the history, causes, and risk of floods across the state. We then describe flood management agencies, infrastructure, and strategies, as well as how governmental agencies typically respond when floods occur. Next, we describe the spending levels and funding sources currently supporting flood management efforts, as well as estimates for how much additional funding may be needed to improve those efforts. We conclude by highlighting some key challenges confronting the state in contemplating how best to manage floods in California.

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Protocol for Closure of Delta Waterways
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Protocol for Closure of Delta Waterways
Office of Emergency Services | November 21, 1997...
Summary
This protocol describes the process for placing restrictions on vessel traffic on the San Joaquin/Sacramento Delta waterways during periods of high water levels...
This protocol describes the process for placing restrictions on vessel traffic on the San Joaquin/Sacramento Delta waterways during periods of high water levels and flood events that involve conditions of disaster or extreme peril to the safety of persons and property. Restrictions will provide for flood fight priorities and control of vessel wakes that may exacerbate levee erosion or overtopping.

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Regional Governance of Flood Management in the Central Valley
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Regional Governance of Flood Management in the Central Valley
Department of Water Resources | May 30, 2014...
Summary
California faces significant challenges in managing its highly variable water resources, particularly as climate change and a growing population exacerbate drought and flood...
California faces significant challenges in managing its highly variable water resources, particularly as climate change and a growing population exacerbate drought and flood risks. The California Department of Water Resources (DWR) and other state agencies have been encouraging
integrated approaches to water management, taking into account the connections between water supply, water quality, flood protection, and ecosystem health. The recent California Water Action Plan calls for improved coordination between local, state and federal agencies and tribal
governments in order to develop multi-?benefit water management strategies. Regional-?scale planning has become a crucial avenue for advancing these efforts. Initiated in 2002, the Integrated Regional Water Management Planning (IRWM) process has led to the formation of 48 water planning regions statewide, in which diverse local agencies have developed integrated plans for managing all aspects of a region’s water management.

More recently, a Regional Flood Management Planning (RFMP) process was created in the context of the Central Valley Flood Protection Plan to advance integrated approaches to reducing flood risks. Six flood planning regions, overlapping with nine IRWM regions, were formed in 2012.

This study analyzes the origins and functioning of the IRWM and RFMP processes, and the degree of coordination between them to address flood risks in the Central Valley. In particular, it examines how each is working to generate multi-?benefit strategies, and how they account for climate
change. It also discusses opportunities for future coordination between the IRWM and RFMP processes, and DWR’s role in supporting this.

This study is primarily based upon an analysis of publicly available documents related to the IRWM and RFMP processes. It is also informed by meeting observations and conversations with staff at DWR and the Central Valley Flood Protection Board, and participants in IRWM and RFMP processes. Since RFMPs were not yet completed at the time of this writing, this study’s findings are preliminary.

Nonetheless, this report provides an indication of the overall functioning of these RFMP and IRWM regions, and some general considerations for DWR as it assesses next steps in supporting these programs.

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Resilient landscape vision for Lower Walnut Creek
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Resilient landscape vision for Lower Walnut Creek
San Francisco Estuary Institute-Aquatic Science Center | November 30, 2016...
Summary
Lower Walnut Creek (Contra Costa County, CA) and its surrounding landscape have undergone considerable land reclamation and development since the mid-nineteenth century. In...
Lower Walnut Creek (Contra Costa County, CA) and its surrounding landscape have undergone considerable land reclamation and development since the mid-nineteenth century. In 1965, the lower 22 miles of Walnut Creek and the lower reaches of major tributaries were converted to flood control channels to protect the surrounding developed land. In the recent past, sediment was periodically removed from the lower Walnut Creek Flood Control Channel to provide flow capacity and necessary flood protection.

Due to the wildlife impacts and costs associated with this practice, the Contra Costa County Flood Control and Water Conservation District (District) is now seeking a new channel management approach that works with natural processes and benefits people and wildlife in a cost-effective manner. Flood Control 2.0 project scientists and a Regional Science Advisory Team (RSAT) worked with the District to develop a long-term management Vision for lower Walnut Creek that could result in a multi-benefit landscape that restores lost habitat and is resilient under a changing climate.

Development of the Vision began with technical analyses focused on understanding past and present landscape functioning and the changes to key processes and landscape features over the past 150 to 200 years. The key findings from these analyses include the following:

• Landscape change – During the mid-19th century, lower Walnut Creek was surrounded by a continuous expanse of tidal wetlands occupying approximately 5,000 acres. Perennial freshwater marsh, willow thicket, and alkali meadow formed a large non-tidal wetland complex that adjoined the tidal marsh on its southern end. Over the past century and a half, the non-tidal wetland complex has been lost completely and the tidal wetland area has decreased by 40%. The remaining marsh areas are highly fragmented and cut-off from Walnut Creek by engineered levees. The loss of tidal wetland area has resulted in a substantial decrease in tidal prism and contributed to current in-channel sediment accumulation issues. Around the mouth of Walnut Creek, sediment accumulation has caused the position of the shoreline to expand into the Bay by up to half a mile.

• Sediment accumulation – Since 1965, approximately 1.4M cubic yards of sediment have been removed from lower Walnut Creek, with approximately 70% coming from the tidal zone downstream of head of tide (i.e., the inland extent of tidal inundation at mean higher high water). Repeat channel cross-section surveys indicate that the channel quickly fills in with sediment following dredging events (due in large part to decreased tidal prism and associated channel scour capacity) and that the channel bed elevation is currently at or near “quasi-equilibrium.” A channel sediment budget for 1965-2007 indicates that approximately 80% of the watershed-derived sediment made it through lower Walnut Creek and out to the Bay, while the remaining 20% was likely deposited directly following channel construction and subsequent dredging events.

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