State Investments in Delta Levees: Key Issues For Updating Priorities

Delta Stewardship Council (Delta Council) | January 9th, 2015

This paper outlines 15 issues that will need to be considered as the Council updates the Delta Plan’s 36 provisions regarding State investment in the Delta’s levees.

This paper outlines 15 issues that will need to be considered as the Council updates the Delta Plan’s 36 provisions regarding State investment in the Delta’s levees. It summarizes background information 37 about these issues, provides references for further information, and highlights key points that will need 38 to be addressed over the coming months.

State of the Estuary 2019 Update

San Francisco Estuary Partnership (SFEP) | October 22nd, 2019

The San Francisco Estuary is a large and diverse system. Hundreds of miles of coastline stretch from the wide valleys of the Sacramento and San Joaquin Rivers to the stee

The San Francisco Estuary is a large and diverse system. Hundreds of miles of coastline stretch from the wide valleys of the Sacramento and San Joaquin Rivers to the steep headlands of the Golden Gate, with vast agricultural fields in the Delta and urbanized shorelines in Silicon Valley and many of the region’s cities. The complexity and scale of this system means it can take years to detect and assess changes. This interim State of the Estuary Report checks in on a few indicators of health and explores where the assessment should head over time. In the four years since the 2015 State of the Estuary Report, two issues have emerged as critical to how we assess the health of the estuarine ecosystem at the heart of the Bay Area and the Delta. First, the health of the Estuary and of the people who live near it and depend on it are inextricably linked. We need a healthy Bay and Delta to protect our shorelines from sea level rise, help keep our waters clean, provide food and habitat for fish and wildlife, and give people a place to enjoy nature. We also need to think more about human communities as we assess the health of natural communities. This focus means addressing environmental injustices that are deeply embedded in our culture and patterns of development. The second critical issue to emerge is the need for a greater focus on landscape resilience—how well the Bay and the Delta are equipped to respond to change—so that people and wildlife can thrive as climate change progresses. Taking these two ideas together, this report focuses on the nexus of social and ecological resilience as we look toward the future. The first section of the Report updates indicators of ecological health that span the entire extent of the San Francisco Estuary (Bay and Delta). Recent data show continued progress along the trajectories of the past decade. Tidal marsh restoration is proceeding at a brisk pace in the Bay and gaining traction in the Delta, while urban water conservation continues to meet mandated benchmarks, even during the drought. On the other hand, flows through the Estuary and across its floodplains continue to be well below levels that could increase and restore ecosystem health. Freshwater flows are a lynchpin of ecosystem processes that sustain physical habitats, fuel the food web, and regulate water quality. Creative approaches to using and re-using fresh water for environmental purposes are needed. Long-term trend analysis shows that fish communities in the Bay are declining. This analysis scores an index of 10 attributes of a healthy fish community. The index focuses on fish in offshore areas, and may not capture benefits to fish from near-shore wetland restoration projects. Despite this slow decline, fish communities in the saltier parts of the Estuary remain in good condition, while those in the brackish and freshwater areas are in poor condition. The next section of the report discusses three emerging indicators of Estuary health, offering options for how to assess resilience in future reports. Here, for the first time, the resilience of the Estuary’s shores is evaluated through the lens of subsidence and nature-based features. Elevation relative to sea level is a basic currency that must be tracked as the Pacific Ocean rises into the Estuary. The potential for the Estuary shore to be resilient to climate change and continue to provide benefits to people is related to how much of the shore zone is nature-based. The final emerging indicator, urban green space, is a first attempt to assess how access to nature is distributed across more and less advantaged communities. More work is needed to finalize all these emerging indicators before they can be included in any future quantitative assessment of the State of the Estuary. These emerging and updated indicators will help focus efforts to restore the Estuary’s health. In addition to continuing the successful aspects of restoration and conservation that this report describes, we need more investment in creative ways to use and restore flows for environmental health, to expand and build resilient shorelines and to weave considerations of social equity more strongly into efforts to improve environmental health. - J. Letitia Grenier, Lead Scientist

Sustainable floodplains through large-scale reconnection to rivers

American Association for the Advancement of Science (AAAS) | December 11th, 2009

Flooding is the most damaging natural disaster worldwide, and the flood-vulnerable population is expected to grow in coming decades. Flood risks will likely increase beca

Flooding is the most damaging natural disaster worldwide, and the flood-vulnerable population is expected to grow in coming decades. Flood risks will likely increase because of both climate change and shifting land uses, such as filling of wetlands and expansion of impervious surfaces, that lead to more rapid precipitation runoff into rivers. In the United States, annual river flood losses continue to rise, punctuated by major events in the Midwest (1993, $30 billion in total costs; 2008, $15 billion) and California's Central Valley (1995 and 1997; $4 billion each event). Meanwhile, pressure to develop new housing in floodprone areas near rivers (floodplains) continues , even as levee-system maintenance is chronically underfunded.

The effects of aquatic area abundance, buffer, and hydrology on depressional wetland condition based on CRAM

San Francisco Estuary Institute (SFEI) | April 1st, 2016

The hidden influence of terrestrial groundwater on salt marsh function and resilience

Nature Portfolio (Springer Nature) | February 3rd, 2025

Salt marshes are hotspots of nutrient processing and carbon sequestration. So far, studies addressing spatiotemporal variability in and drivers of salt marsh biogeochemic

Salt marshes are hotspots of nutrient processing and carbon sequestration. So far, studies addressing spatiotemporal variability in and drivers of salt marsh biogeochemical function, carbon storage and resilience have focused on ocean-driven surface hydrologic influences, neglecting effects of terrestrial hydrology through subsurface connections. Here we evaluate drivers of salt marsh redox potential, a proxy for biogeochemical state, through wavelet analyses and information theory using data from seven marshes. The results point to terrestrial groundwater level as a dominant control on redox variability across all sites. Because redox is a key driver of biogeochemical processes, and specifically oxidation of organic matter that sequesters carbon and maintains marsh elevation, these terrestrial influences are critical to understanding marsh function and evolution. The newly identified links between onshore groundwater levels and marsh redox conditions shift the traditional paradigm and suggest that terrestrial hydrology is a primary control on salt marsh carbon sequestration potential and resilience.

The impact of vegetation on meandering rivers

Nature Portfolio (Springer Nature) | January 25th, 2022

The Palaeozoic evolution of land plants revolutionized river geomorphology. However, the relationships between biotic forcing and channel dynamics are still debated and,

The Palaeozoic evolution of land plants revolutionized river geomorphology. However, the relationships between biotic forcing and channel dynamics are still debated and, as such, the impacts of anthropogenic stressors such as climate change, reduced biodiversity and aridification on modern meandering rivers and their biogeochemical fluxes remain poorly understood. In this Review, we propose a unifying framework based on field and modelling data that describes the stability and dynamics of meandering rivers in both the presence and the absence of land plants. Based on evidence from the pre-vegetation rock record and from modern systems, we emphasize that meandering streams can indeed arise in the absence of land plants. However, plant evolution provided widespread settings suitable for stable meandering systems through retention of floodplain mud, sediment baffling and mechanical strengthening of channel banks. Altogether, these processes slowed the characteristic rates of meander growth and floodplain-soil reworking by up to an order of magnitude. Continued anthropogenic removal of riparian and watershed vegetation due to increased urbanization, deforestation, aridification and pollution could revert streams to pre-vegetation functioning, thereby increasing their channel and sediment mobility. Future research can use this framework to constrain the pace of ancient landscape processes on Earth and Mars, in addition to modern terrestrial rivers impacted by humans.

The value of marsh restoration for flood risk reduction in an urban estuary

Nature Portfolio (Springer Nature) | March 21st, 2024

Toward Natural Infrastructure to Manage Shoreline Change in California

California Natural Resources Agency (CNRA) | August 27th, 2018

Flooding and erosion caused by rising sea levels and powerful storms threaten property throughout coastal California. To protect against these climate-change related thr

Flooding and erosion caused by rising sea levels and powerful storms threaten property throughout coastal California. To protect against these climate-change related threats, landowners will certainly take action, and the default industry standard response has been to try to “hold the line” against the encroaching sea by constructing seawalls, dikes, levees and other forms of coastal armoring. While armoring may in some cases provide acceptable short-term protection, armoring also tends to accelerate shoreline erosion, exacerbating hazards to people and leading to the eventual loss of critical wildlife habitat and public beaches. Natural Shoreline Infrastructure can be as effective as armoring, while having the added benefits of preserving coastal habitat and public access. Recognizing this, California agencies have mandated that decision-makers prioritize its use in planning and investment decisions. Yet, planners have encountered many stumbling blocks as they have tried to incorporate these approaches into coastal resilience plans. Major obstacles include: a lack of a common definition and shared terminology; lack of expertise; lack of precedent; and the absence of siting guidance and technical design standards. Here, we set out to enable planners to adopt Natural Shoreline Infrastructure by filling in the missing information. With the input of dozens of coastal managers who served on our Technical Advisory Committee, we developed a definition and collected a list of case studies where Natural Shoreline Infrastructure has already been successfully deployed in California. Drawing from these and other projects, we collected into one place the first detailed technical guidance for implementation, including siting criteria and design thresholds. These criteria inform decisions about where and when to use six types of Natural Shoreline Infrastructure (e.g. sand dunes, seagrass beds). Using Monterey Bay and Ventura County projects as examples, we demonstrate how to use the technical guidance in tandem with spatial data to match a particular shoreline environment with appropriate Natural Shoreline Infrastructure options, creating “blueprints” for action. The information in this report is intended to facilitate the use of Natural Shoreline Infrastructure along California’s coast, improving the resilience of communities and habitats in the face of climate change.

Translating Science-Based Restoration Strategies into Spatially-Explicit Restoration Opportunities in the Delta (2018 Bay-Delta Science Conference Presentation)

San Francisco Estuary Institute (SFEI) | July 2nd, 2018

In a previous report titled “A Delta Renewed” we offered a collection of guidelines for science-based ecological restoration in the Sacramento-San Joaquin Delta that

In a previous report titled “A Delta Renewed” we offered a collection of guidelines for science-based ecological restoration in the Sacramento-San Joaquin Delta that emphasized restoring or emulating natural processes, anticipating future changes associated with climate change, establishing appropriate configurations of habitat types at the landscape scale, and utilizing a variety multi-benefit management strategies. In this talk, we present on our recent work to support regional restoration planning efforts by developing a repeatable process for using these guidelines to identify spatially-explicit restoration opportunities. The process is largely GIS-based and utilizes spatial data on existing land cover and conservation status, habitat configuration (including patch sizes and distances), surface elevations (including depth of subsidence), and future changes in tidal elevations associated with sea-level rise.  By distilling generalized guidelines into spatially-explicit opportunities, we hope to provide a practical tool for incorporating science into planning. To that end, these new methods are currently being piloted through planning efforts focused on the Central Delta Corridor and the McCormack Williamson Tract, and are also being used to assist with the quantification of ecological restoration potential in the Delta Plan Ecosystem Amendment.

Valuing Urban Nature – Implications for Flood Resilience

Stanford University | June 3rd, 2019

Sea-level rise and extreme weather events such as torrential rain storms are having devastating consequences in the United States and globally. Researchers, prac

Sea-level rise and extreme weather events such as torrential rain storms are having devastating consequences in the United States and globally. Researchers, practitioners, and policymakers are increasingly calling for the use of natural and nature-based approaches to protect urban areas from flooding which has increased in frequency and intensity as a result. Natural features can help stabilize shorelines and protect communities from river flooding while, providing other co- benefits for people and ecosystems. In a new study, scientists at the Natural Capital Project developed a framework for valuating urban nature and examined different factors cities must consider when making infrastructure and other investment choices. This brief is part of a series based on that research which looks at nature’s abilityto provide resilience to flooding and the various co-benefits associated with nature-based solutions.