sea level rise

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Analysis of the costs and benefits of using marsh restoration as a sea level rise adaptation strategy in San Francisco Bay
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Analysis of the costs and benefits of using marsh restoration as a sea level rise adaptation strategy in San Francisco Bay
The Bay Institute | February 22, 2013...
Summary
The purpose of this study is to examine opportunities to protect San Francisco Bay’s recovering tidal marsh ecosystems while helping bayshore communities to...
The purpose of this study is to examine opportunities to protect San Francisco Bay’s recovering tidal marsh ecosystems while helping bayshore communities to manage the impacts of sea level rise. Specifically, it considers the flood risk management functions that tidal marshes perform naturally and evaluates the possibility of integrating those functions into a co-beneficial shoreline management strategy. The study’s intended audience is planners, politicians, regulators, and other stakeholders with the authority to make or affect decisions that influence the configuration and use of the San Francisco Bay shoreline. The study examines the current functions of San Francisco Bay tidal marshes as well as existing flood risk management strategies. It considers how environmental conditions are likely to change in the era of climate change, and how we can adapt our marshes and our flood risk management practices to accommodate these changes.

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California’s Future
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California’s Future
Public Policy Institute of California (PPIC) | January 18, 2018...
Summary
Water management in California has always been challenging. The state’s variable climate is marked by long droughts and severe floods, with stark regional...
Water management in California has always been challenging. The state’s variable climate is marked by long droughts and severe floods, with stark regional differences in water availability and demand. California has adapted by building a vast network of storage and conveyance facilities to deliver water from the wetter parts of the state to population and farming centers in the Bay Area, the San Joaquin Valley, and Southern California. The Sacramento–San Joaquin Delta is a fragile link in the state’s water supply network, and a plan to address supply reliability, known as California WaterFix, faces many hurdles. California’s extensive network of dams is aging. Agricultural demand is becoming less flexible, as farmers are increasing tree crops (especially nuts), which must be watered every year. Conflicts are growing between human water use and water needed to support fish and other wildlife. And the latest cycle of droughts and floods provides a glimpse of an uncertain future under climate change. California’s water management challenges are complex, but they can be addressed. Solutions will involve difficult and sometimes costly trade-offs, as well as contentious legal and political changes.

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Climate Change and the Delta
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Climate Change and the Delta
San Francisco Estuary and Watershed Science | October 1, 2016...
Summary
Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability,...
Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated.

Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. Future precipitation changes are less certain, with as many climate models projecting wetter conditions as drier. Warmer temperatures will likely enhance evaporation and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks.

Effects on the Delta ecosystem that are traceable to warming include sea level rise, reduced snowpack, earlier snowmelt and larger storm-driven streamflow, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas.

Although the effects of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful preparation for the coming changes will require greater integration of monitoring, modeling, and decision-making across time, variables, and space than has been historically normal.

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Climate Change and the Delta: A Synthesis (Public Review Draft)

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Climate Change and the Delta: A Synthesis (Public Review Draft)
Delta Stewardship Council | March 23, 2018...
Summary
The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to...
The Delta Reform Act of 2009 (Water Code Section 85066) requires that the Delta Stewardship Council adopt a Delta Plan (the Plan) to achieve the coequal goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem (Water Code Section 85000). In the time since the Plan was adopted in 2013, a significant shift in State planning for Delta ecosystem protection, restoration, and enhancement has occurred, prompting review of the Delta Plan to examine whether its strategies are still suited to achieve the ecological goals of the Delta Reform Act. As such, the Delta Stewardship Council (Council) is developing an amendment of the Plan’s Chapter 4, Protect, Restore, and Enhance the Delta Ecosystem.

Council staff are reviewing the best-available science to inform amendment of Chapter 4 of the Delta Plan. To support this effort, Council staff have developed three science synthesis papers. This paper focuses on the effects of climate change in the Delta and is accompanied by two other papers focused on the Delta ecosystem (terrestrial and aquatic resources) and restoration. Climate change is of interest for the Chapter 4 amendment given recent rapid advancements in research on climate change and its effects on the Delta ecosystem that have occurred since the Delta Plan was adopted in 2013 (Dettinger et al. 2016).

Climate change has the potential to significantly affect the Delta ecosystem by raising air and water temperatures, changing the timing and volume of flows into and through the Delta, increasing tidal inundation with sea-level rise (SLR), and increasing salinity intrusion into the Delta. Climate change is recognized as a global stressor in Chapter 4 of the 2013 Delta Plan, but the effects of climate change on Delta ecosystems are discussed only briefly and with limited consideration of management strategies that address the issue. Chapter 4 of the Delta Plan identifies five key stressors to the Delta ecosystem and core strategies for addressing each. Climate change has interrelated effects on all five core strategy areas: Delta flows, habitat, water quality, non-native 28 species, and hatcheries and harvest management.

The Delta Reform Act specifies consideration of “the future impact of climate change and sea-level rise” (Water Code Section 85066), and identifies a restoration timeline horizon of 2100 (Water Code Section 85302). More generally, Executive Order B-30-15, signed by Governor Brown in April 2015, requires that State agencies incorporate climate change into planning and investment decisions, and that they prioritize natural infrastructure and actions for climate preparedness.

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Coastal flooding – potential projections: 2000–2100
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Coastal flooding – potential projections: 2000–2100
California Energy Commission | July 31, 2012...
Summary
The change in flooding potential along the California coast over the twenty?first century was estimated from both ocean wave and sea level rise...
The change in flooding potential along the California coast over the twenty?first century was estimated from both ocean wave and sea level rise projections produced from global climate model data.

Changes in flooding potential were inferred from changes in wave runup (the vertical height reached by wave?driven water levels), which depends on the instantaneous sea level (or still water level), beach slope, and wave height and wave period. The still water level is the superposition of regional (or relative) mean sea level, the tide, and non?tide sea level fluctuations. Non?tide sea level fluctuations include both the steric response associated with El Niño–related variability that can persist up to a year or more, and local storm–forced variability (storm surge).

The potential for greatest coastal flooding occurs when extremes in waves and still water level occur nearly simultaneously. Wave activity provides the primary driving force for coastal flooding. Wave model significant wave height (Hs) and non?tide sea level projections were generated for a seven global climate model simulations. Comparison of the Hs and nontide projections with wave model hindcast Hs and observed non?tide fluctuations suggest that the characteristics and incidence of extreme Hs and non?tide fluctuations will not increase appreciably over the twenty?first century.

Thus, because astronomical tide?forcing will not increase, increases in relative mean sea level will largely determine the potential for increased ocean?driven flooding along the California coast. If relative mean sea level along the California coast reaches global mean sea level rise projections associated with climate change, extreme flooding events expected to occur once in about 100 years under stationary relative mean sea levels will occur annually.

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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 Levees Investment Strategy: Sea Level Rise Methodology

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Delta Levees Investment Strategy: Sea Level Rise Methodology
Delta Stewardship Council | August 21, 2015...
Summary
This memorandum describes the methodology used to account for the impact of potential future sea level rise on the Delta Levees Investment Strategy...
This memorandum describes the methodology used to account for the impact of potential future sea level rise on the Delta Levees Investment Strategy (DLIS) metrics and how those impacts are incorporated into the DLIS planning tool. A description of the approach used to account for the spatial variation of tide effects in the Delta and Suisun Marsh and prediction uncertainties are also included in this memorandum.

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Factors and Processes Affecting Delta Levee System Vulnerability
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Factors and Processes Affecting Delta Levee System Vulnerability
San Francisco Estuary and Watershed Science | December 1, 2016...
Summary
The authors appraised factors and processes related to human activities and high water, subsidence, and seismicity. Farming and drainage of peat soils over...
The authors appraised factors and processes related to human activities and high water, subsidence, and seismicity. Farming and drainage of peat soils over time has caused a gradual sinking which contributed to internal levee failures. Although these subsidence rates have decreased with time, they still contribute to levee instability. Additional data is needed to assess spatial and temporal effects of subsidence caused by peat thinning and deformation. Since the mid-1970s large-scale, State investments in levee upgrades have increased conformance, however accounts continue to conflict on how these investments correspond to the numbers of failures.

Both modeling and history suggest that the projected increases of high-flow frequency associated with climate change will increase levee-failures rates. Quantification of this increased threat requires further research. A reappraisal of seismic threats resulted in updated ground motion estimates for multiple faults and earthquake occurrence frequencies. The immediate seismic threat, liquefaction, is the sudden loss of strength due to an increase in the pressure of the pore fluid and corresponding loss of contact forces. However, levees damaged during an earthquake that do not immediately fail, may eventually breach.

Consequences for future levee failure are estimated to cost up to billions of dollars. The analysis of future risks will benefit from more detailed descriptions of levee strength and upgrades, consideration of subsidence, climate change, and earthquake threats. Ecosystem benefits of levee habitats in this highly altered system are thin. Better recognition and coordination is needed among the creation of high value habitats, levee needs, costs, benefits of levee improvements, and breaches.

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Rising seas in California: An update on sea-level rise science
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Rising seas in California: An update on sea-level rise science
California Ocean Protection Council | April 22, 2017...
Summary
Key findings of this report: Scientific understanding of sea-level rise is advancing at a rapid pace. Projections of future sea-level rise, especially under...
Key findings of this report:

Scientific understanding of sea-level rise is advancing at a rapid pace. Projections of future sea-level rise, especially under high emissions scenarios, have increased substantially over the last few years, primarily due to new and improved understanding of mass loss from continental ice sheets. These sea-level rise projections will continue to change as scientific understanding increases and as the impacts of local, state, national and global policy choices become manifest. New processes that allow for rapid incorporation of new scientific data and results into policy will enable state and local agencies to proactively prepare.

The direction of sea level change is clear. Coastal California is already experiencing the early impacts of a rising sea level, including more extensive coastal flooding during storms, periodic tidal flooding, and increased coastal erosion.

The rate of ice loss from the Greenland and Antarctic Ice Sheets is increasing. These ice sheets will soon become the primary contributor to global sea-level rise, overtaking the contributions from ocean thermal expansion and melting mountain glaciers and ice caps. Ice loss from Antarctica, and especially from West Antarctica, causes higher sea-level rise in California than the global average: for example, if the loss of West Antarctic ice were to cause global sea-level to rise by 1 foot, the associated sea-level rise in California would be about 1.25 feet.

New scientific evidence has highlighted the potential for extreme sea-level rise. If greenhouse gas emissions continue unabated, key glaciological processes could cross thresholds that lead to rapidly accelerating and effectively irreversible ice loss. Aggressive reductions in greenhouse gas emissions may substantially reduce but do not eliminate the risk to California of extreme sea-level rise from Antarctic ice loss. Moreover, current observations of Antarctic melt rates cannot rule out the potential for extreme sea-level rise in the future, because the processes that could drive extreme Antarctic Ice Sheet retreat later in the century are different from the processes driving loss now.

Probabilities of specific sea-level increases can inform decisions. A probabilistic approach to sea-level rise projections, combined with a clear articulation of the implications of uncertainty and the decision support needs of affected stakeholders, is the most appropriate approach for use in a policy setting. This report employs the framework of Kopp et al. (2014) to project sea-level rise for three representative tide gauge locations along the Pacific coastline: Crescent City in northern California, San Francisco in the Bay area, and La Jolla in southern California. These projections may underestimate the likelihood of extreme sea-level rise, particularly under high emissions scenarios, so this report also includes an extreme scenario called the H++ scenario. The probability of this scenario is currently unknown, but its consideration is important, particularly for high-stakes, long-term decisions.

Current policy decisions are shaping our coastal future. Before 2050, differences in sea-level rise projections under different emissions scenarios are minor but they diverge significantly past midcentury. After 2050, sea-level rise projections increasingly depend on the trajectory of greenhouse gas emissions. For example, under the extreme H++ scenario rapid ice sheet loss on Antarctica could drive rates of sea-level rise in California above 50 mm/year (2 inches/year) by the end of the century, leading to potential sea-level rise exceeding 10 feet. This rate of sea-level rise would be about 30-40 times faster than the sea-level rise experienced over the last century.

Waiting for scientific certainty is neither a safe nor prudent option. High confidence in projections of sea-level rise over the next three decades can inform preparedness efforts, adaptation actions and hazard mitigation undertaken today, and prevent much greater losses than will occur if action is not taken. Consideration of high and even extreme sea levels in decisions with implications past 2050 is needed to safeguard the people and resources of coastal California.

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Sediment Supply to San Francisco Bay, Water Years 1995 through 2016: Data, trends, and monitoring recommendations to support decisions about water quality, tidal wetlands, and resilience to sea level rise
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Sediment Supply to San Francisco Bay, Water Years 1995 through 2016: Data, trends, and monitoring recommendations to support decisions about water quality, tidal wetlands, and resilience to sea level rise
San Francisco Estuary Institute | June 11, 2018...
Summary
Knowledge of the status and trends of sediment supply to San Francisco Bay is critically important for management decisions about dredging, marsh restoration,...
Knowledge of the status and trends of sediment supply to San Francisco Bay is critically important for management decisions about dredging, marsh restoration, flood control, contaminants, water clarity (in relation to primary production), and sea level rise. Several sitespecific studies of sediment supply to San Francisco Bay have been conducted, but no synthesis of recent studies is available. The purpose of this report is to synthesize the best available data and knowledge to answer a few of the key study questions related to sediment supply to the Bay (listed below). This synthesis report was prepared jointly by the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) and the U. S. Geological Survey (USGS) with funding from both organizations. The project is meant to be a step in the development of a more comprehensive sediment management and monitoring strategy for the Bay.

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