State of California Sea Level Guidance

California Ocean Protection Council (COPC) | May 31st, 2024

This report updates and replaces the previous 2018 ‘State of California Sea Level Rise Guidance’ and marks the fourth iteration of statewide guidance since 2010 for s

This report updates and replaces the previous 2018 ‘State of California Sea Level Rise Guidance’ and marks the fourth iteration of statewide guidance since 2010 for state and local decision-makers to incorporate best available science on sea level rise into planning, design, permitting, investments, and other decisions.

State of California Sea Level Rise Guidance

California Natural Resources Agency (CNRA) | March 14th, 2018

The climate across California is changing, and the effects, such as rising average temperatures, shrinking mountain snowpack, more intense storms, and higher sea

The climate across California is changing, and the effects, such as rising average temperatures, shrinking mountain snowpack, more intense storms, and higher sea levels are expected to continue and worsen in the coming decades. Sea-level rise is caused by the thermal expansion of warming ocean water and melting of land ice as the Earth warms. It is one of the most obvious manifestations of the trend of climate change and is an immediate and real threat to lives, livelihoods, transportation, economies, and the environment in California. In April 2017, catalyzed by direction from Governor Brown and the need to ensure that best available science was informing sea-level rise planning decisions in California, a Working Group of the California Ocean Protection Council’s Science Advisory Team (OPC-SAT) released a report, entitled “Rising Seas in California: An Update on Sea-Level Rise.” The Rising Seas Report was prepared and peer-reviewed by some of the nation’s foremost experts in coastal processes, climate and sea-level rise science, observational and modeling science, the science of extremes, and decision-making under uncertainty. The report synthesized the current state of sea-level rise science, including advances in modeling and improved understanding of the processes that could drive extreme global sea-level rise as a result of ice loss from the Greenland and Antarctic ice sheets. The report found that: Scientific understanding of sea-level rise is advancing at a rapid pace. The direction of sea-level change is clear; sea levels are rising. The rate of ice loss from the Greenland and Antarctic ice sheets is increasing, and California is particularly vulnerable to sea-level rise caused by ice loss from West Antarctica. New scientific evidence has highlighted the potential for extreme sea-level rise. Probabilities of specific sea-level increases can inform decisions. Current policy decisions are shaping our coastal future. Waiting for scientific certainty is neither a safe nor prudent option. The increased understanding of sea-level rise projections and polar ice sheet loss warranted an update to the State’s sea-level rise guidance document to ensure decisions were based on the best available science. Additionally, an increased policy focus requiring state and local governments to incorporate climate change into decision making merited an update to address the needs of both state and local audiences. This updated document, the “State of California Sea-Level Rise Guidance” (Guidance), provides a bold, science-based methodology for state and local governments to analyze and assess the risks associated with sea-level rise, and to incorporate sea-level rise into their planning, permitting, and investment decisions. This Guidance provides: 1. A synthesis of the best available science on sea- level rise projections and rates for California; 2. A step-by-step approach for state agencies and local governments to evaluate those projections and related hazard information in decision making; and 3. Preferred coastal adaptation approaches.

State of the Estuary, October 2013

San Francisco Estuary Partnership (SFEP) | October 31st, 2013

State Plan of Flood Control Descriptive Document (2010)

California Department of Water Resources (DWR) | January 15th, 2010

This report provides an inventory and description of the existing flood control works (facilities), lands, programs, plans, conditions, and mode of operations and mainten

This report provides an inventory and description of the existing flood control works (facilities), lands, programs, plans, conditions, and mode of operations and maintenance (O&M) for the State-Federal flood protection system in the Central Valley of California. This flood protection system is composed of federally authorized project levees and related facilities for which the State has provided assurances1 of cooperation to the federal government. These State-provided assurances are an important distinction for what constitutes the State-federal flood protection system since other flood protection facilities in the Central Valley are not covered by State assurances and are not part of the State-federal system. Collectively, the facilities, lands, programs, conditions, and mode of O&M for the State-Federal flood protection system in the Central Valley are referred to as the State Plan of Flood Control (SPFC). This SPFC Descriptive Document is the first time that an inventory of the SPFC has been compiled or referenced in a single document. Until now, much of the information on the SPFC has been individually maintained for each of the many flood protection projects that constitute State-federal flood protection along the Sacramento and San Joaquin rivers and tributaries. For example, much of the information contained in sections of this report originates in 118 individual project (unit-specific) O&M manuals. The O&M manuals provide key information about each project and how it should be operated and maintained (see reference digital versatile disc (DVD) at the back of this report). In addition, since the individual projects for the system were implemented over almost a century, some information may have been lost or never obtained. In those cases, gaps exist in the information presented in this report and further research is required. It is important to note that the SPFC is only a portion of the larger system that provides flood protection for the Central Valley. The SPFC relies on many other features that do not meet the definition of the SPFC. For example, non-SPFC reservoirs provide substantial regulation of flows to levels that SPFC facilities can mostly handle. Private levees, locally operated drainage systems, and other facilities work in conjunction with SPFC facilities. Management practices such as emergency response, floodplain management, and other practices are part of the overall flood protection system. All parts of the system, including the SPFC, depend on other parts of the system to operate as a unit. This report is structured as a reference document for the SPFC. It includes narrative descriptions, tables, and figures, especially maps, to help the reader find information for this complex flood management system. Some sections include summary sections for readers who only need an overview of the subject. RELATED DOCUMENT: State Plan of Flood Control Descriptive Document 2016 Update

State Plan of Flood Control Descriptive Document 2016 Update

California Department of Water Resources (DWR) | December 14th, 2016

The November 2016 State Plan of Flood Control (SPFC) Descriptive Document Update (2016 Update) is intended to serve as a reference for flood management planners and opera

The November 2016 State Plan of Flood Control (SPFC) Descriptive Document Update (2016 Update) is intended to serve as a reference for flood management planners and operators at the local, State, and federal levels. It is not a stand-alone document; rather, it works in conjunction with the November 2010 SPFC Descriptive Document, builds upon information presented in the original report, and documents changes to the SPFC that have occurred between November 2010 and July 2016. The 2016 Update documents the inventory of flood control projects and works (facilities), lands, programs, plans, conditions, and mode of operations and maintenance for the State-federal flood management system in the Sacramento River and San Joaquin River watersheds of California, as well as informs the 2017 Central Valley Flood Protection Plan Update. In 2006 and 2007, California voters approved the Disaster Preparedness and Flood Prevention Bond Act of 2006 and the Central Valley Flood Protection Act of 2008 respectively. These acts defined the Sacramento River and San Joaquin River federal-State flood control projects as the SPFC, and required DWR to develop, and the Central Valley Flood Protection Board to adopt, a Central Valley Flood Protection Plan. The Central Valley Flood Protection Plan is broader than the SPFC, affecting the entire watersheds of the Sacramento and San Joaquin valleys. A complex system of dams and reservoirs, levees, weirs, bypasses, and other features constructed piecemeal over the last 100 years protects urban and rural areas against most flooding. This system has prevented billions of dollars in damage in its lifetime. A portion of this complex flood protection system includes State and federally authorized projects for which the Central Valley Flood Protection Board or DWR has provided assurances of cooperation to the federal government, known as the SPFC. These statutory authorizations include provisions regarding responsibility for operation and maintenance of the flood control facilities. The California Legislature has authorized funding for numerous flood control projects throughout the Sacramento and San Joaquin River watersheds. As the SPFC evolves, updates to the SPFC Descriptive Document will be useful in determining funding eligibility for funding for facility improvements. RELATED DOCUMENT:  State Plan of Flood Control (2010)

State Plan of Flood Control Descriptive Document Update (2017)

California Department of Water Resources (DWR) | August 10th, 2017

The State Plan of Flood Control (SPFC) Descriptive Document, November 2010, provided the first inventory and description of the flood management projects and features (fa

The State Plan of Flood Control (SPFC) Descriptive Document, November 2010, provided the first inventory and description of the flood management projects and features (facilities), lands, programs, plans, conditions, and mode of operations and maintenance for the State-federal flood management system in the Sacramento River and San Joaquin River watersheds of California. The 2010 Descriptive Document was prepared in response to Proposition 1E (Disaster Preparedness and Flood Prevention Act of 2006), which required that information on the SPFC “…. be updated and compiled into a single document entitled, ‘The State Plan of Flood Control.’” Similar information is required to be a part of the CVFPP pursuant to the Central Valley Flood Protection Act of 2008. Legislation relevant to this document can be found in Appendix A. While much of the information contained in the 2010 Descriptive Document has not changed, it was anticipated that future updates would be necessary to keep the SPFC description current as new or ongoing projects were completed. Also, updates to the SPFC would be appropriate to reflect any additional or new documentation discovered on existing projects that would meet the requirements of the SPFC. The purpose of this update to the 2010 Descriptive Document is to describe changes that have occurred to the SPFC since the 2010 Descriptive Document due to project implementation and other related changes. This document also supports the data and analysis of the 2017 Central Valley Flood Protection Plan Update (CVFPP) and the 2017 Flood System Status Report (FSSR). The SPFC Descriptive Document Update (Update) is structured as a reference document and should be used in conjunction with the 2010 Descriptive Document to represent the SPFC as of June 30, 2016. It includes narrative descriptions, tables, figures, web links, and maps, to help the reader find information for this complex flood management system. Figure G-1 shows a geographic overview of the SPFC. Consistent with the 2010 Descriptive Document level of detail, this report describes changes to the major elements of the SPFC, but only to a level of detail necessary to orient the reader to the SPFC and reference where more information can be found. For example, a given reach of levee may have many encroachments such as pipes that cross under, through, or over the levee. In addition, a given river reach may have associated bridges, stream gages, drainage facilities, etc. No attempt was made to itemize all these encroachments and associated facilities in this Update. Because of the volume of available information, a reference digital versatile disc (DVD) was provided in the pocket at the end of the 2010 Descriptive Document. The DVD provided more details than could be contained in the text of the 2010 report. The contents of the 2010 Reference DVD, excluding the SPFC Mapbook and O&M manual database, is located on the 2012 CVFPP webpage at http://www.water.ca.gov/cvfmp/2012-cvfpp-docs.cfm.

Storm rainfall conditions for floods and debris flows from recently burned areas in southwestern Colorado and southern California

Geomorphology (Elsevier) | April 15th, 2008

Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unli

Debris flows generated during rain storms on recently burned areas have destroyed lives and property throughout the Western U.S. Field evidence indicate that unlike landslide-triggered debris flows, these events have no identifiable initiation source and can occur with little or no antecedent moisture. Using rain gage and response data from five fires in Colorado and southern California, we document the rainfall conditions that have triggered post-fire debris flows and develop empirical rainfall intensity–duration thresholds for the occurrence of debris flows and floods following wildfires in these settings. This information can provide guidance for warning systems and planning for emergency response in similar settings. Debris flows were produced from 25 recently burned basins in Colorado in response to 13 short-duration, high-intensity convective storms. Debris flows were triggered after as little as six to 10 min of storm rainfall. About 80% of the storms that generated debris flows lasted less than 3 h, with most of the rain falling in less than 1 h. The storms triggering debris flows ranged in average intensity between 1.0 and 32.0 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for floods and debris flows sufficiently large to pose threats to life and property from recently burned areas in south-central, and southwestern, Colorado are defined by: I = 6.5D− 0.7 and I = 9.5D− 0.7, respectively, where I = rainfall intensity (in mm/h) and D = duration (in hours). Debris flows were generated from 68 recently burned areas in southern California in response to long-duration frontal storms. The flows occurred after as little as two hours, and up to 16 h, of low-intensity (2–10 mm/h) rainfall. The storms lasted between 5.5 and 33 h, with average intensities between 1.3 and 20.4 mm/h, and had recurrence intervals of two years or less. Threshold rainfall conditions for life- and property-threatening floods and debris flows during the first winter season following fires in Ventura County, and in the San Bernardino, San Gabriel and San Jacinto Mountains of southern California are defined by I = 12.5D−0.4, and I = 7.2D−0.4, respectively. A threshold defined for flood and debris-flow conditions following a year of vegetative recovery and sediment removal for the San Bernardino, San Gabriel and San Jacinto Mountains of I = 14.0D−0.5 is approximately 25 mm/h higher than that developed for the first year following fires. The thresholds defined here are significantly lower than most identified for unburned settings, perhaps because of the difference between extremely rapid, runoff-dominated processes acting in burned areas and longer-term, infiltration-dominated processes on unburned hillslopes.

Storms, Floods, and the Science of Atmospheric Rivers

American Geophysical Union (AGU) | August 9th, 2011

Imagine a stream of water thousands of kilometers long and as wide as the distance between New York City and Washington, D. C., flowing toward you at 30 miles perhour.

Imagine a stream of water thousands of kilometers long and as wide as the distance between New York City and Washington, D. C., flowing toward you at 30 miles perhour. No, this is not some hypothetical physics problem—it is a real river, carrying more water than 7–15 Mississippi Rivers combined. But it is not on land. It’s a river of water vapor in the atmosphere.

Strategic Forest Reserves can protect biodiversity in the western United States and mitigate climate change

Nature Portfolio (Springer Nature) | December 14th, 2021

Forest preservation is crucial for protecting biodiversity and mitigating climate change. Here we assess current forest preservation in the western United States using sp

Forest preservation is crucial for protecting biodiversity and mitigating climate change. Here we assess current forest preservation in the western United States using spatial data and find that beyond the 18.9% (17.5 Mha) currently protected, an additional 11.1% (10.3 Mha) is needed to achieve 30% preservation by 2030 (30 × 30). To help meet this regional preservation target, we developed a framework that prioritizes forestlands for preservation using spatial metrics of biodiversity and/or carbon within each ecoregion. We show that meeting this preservation target would lead to greater protection of animal and tree species habitat, current carbon stocks, future carbon accumulation, and forests that are important for surface drinking water. The highest priority forestlands are primarily owned by the federal government, though substantial areas are also owned by private entities and state and tribal governments. Establishing Strategic Forest Reserves would help protect biodiversity and carbon for climate adaptation and mitigation.

Stratigraphic Analysis of Corte Madera Creek Flood Control Channel Deposits

U.S. Geological Survey (USGS) | September 3rd, 2019

Sedimentation in a channel can reduce flood conveyance capability and potentially place nearby property and life at risk from flooding. In 1998, Marin County Public Works

Sedimentation in a channel can reduce flood conveyance capability and potentially place nearby property and life at risk from flooding. In 1998, Marin County Public Works dredged the concrete-lined segment of Corte Madera Creek, which drains a hilly and largely urbanized watershed that terminates in San Francisco Bay, California. From then through 2015, approximately 4,100 cubic meters of sand and gravel infilled the concrete-lined segment. Determining when and under what conditions this material was deposited informs dredging operations for the Corte Madera Creek Flood Control Project and increases understanding of sediment delivery timing and mechanisms from this and other San Francisco Bay tributaries. Two hypothesized scenarios were investigated: (1) complete flushing during high flows and re-deposition of channel fill afterward and (2) more steady, gradual channel infilling. Stratigraphic analysis of eight sediment cores collected from the flood-control channel deposits in August 2017 was used to identify the most likely scenario. In addition, sediment elevation profiles, grain-size data, and a one-dimensional hydrodynamic model were used to assess the potential for longitudinal-channel scour and deposition following the wet winter of water year 2017 in the intertidal reach of the concrete channel in Corte Madera Creek. Results indicated the channel is undergoing gradual infilling. Storm flows of water year 2017 did not completely scour the concrete channel fill. Sediment cores, stratigraphic analysis, and sediment elevation profiles indicated 0.23 meter of scour at the downstream end of the concrete-lined section and that roughly 0.5 meter of channel fill remained in the channel. The hydrodynamic model demonstrated that sediment deposition in the concrete channel is expected to start downstream from the point where the channel bed reaches mean lower low-water level. High flows can carry most of the sediment through this segment of channel, depositing the bed-material load downstream from the transition to a wide channel, where velocity and bed shear stress decrease abruptly. Although the storm flows of 2017 did not completely scour the channel fill, subsequent material deposited in the channel could be transported downstream from the concrete channel if the sediment elevation profile is in equilibrium with present (2019) mean sea level. A calibrated, coupled hydrodynamic-sediment transport model could be used to test the present equilibrium between sediment elevation profiles and mean sea level, such that additional sediment build-up in the concrete channel is remobilized during subsequent wet-season flows and deposited downstream from the concrete-lined segment.