This study reconstructs the historical landscape of the Petaluma River watershed and documents the major landscape changes that have taken place within the watershed over the past two centuries. Prior to Spanish and American settlement of the region, the Petaluma River watershed supported a dynamic and interconnected network of streams, riparian forests, freshwater wetlands, and tidal marshes. These habitats were utilized by a wide range of plant and animal species, including a number of species that are today listed as threatened or endangered such as Ridgway’s Rail, Black Rail, salt marsh harvest mouse, California red-legged frog, Central California Coast steelhead, and soft bird’s beak (CNDDB 2012, SRCD 2015). Agricultural and urban development beginning in the mid-1800s has significantly altered the landscape, degrading habitat for fish and wildlife and contributing to contemporary management challenges such as flooding, pollutant loading, erosion, and sedimentation. While many natural areas and remnant wetlands still exist throughout the watershed—most notably the Petaluma Marsh—their ecological function is in many cases seriously impaired and their long-term fate jeopardized by climate change and other stressors. Multi-benefit wetland restoration strategies, guided by a thorough understanding of landscape history, can simultaneously address a range of chronic management issues while improving the ecological health of the watershed, making it a better place to live for both people and wildlife.
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.
A Delta Renewed User Guide aims to increase the accessibility of the technical findings in A Delta Renewed for easier application to restoration and conservation efforts across the Delta. The recommendations in A Delta Renewed focus on landscape-scale ecological guidance. We present three examples of how the information in A Delta Renewed might be used to address different management and restoration questions. Because of the complexity of the Delta system, this guide does not address all possible questions and does not replace the need for detailed, site-specific data and expertise. Rather, it shows how the information in A Delta Renewed might provide a common foundation for restoration planning.
The User Guide was written for a broad audience, including restoration practitioners, landowners, and local, state and federal agencies. The guide provides a step-by-step path through A Delta Renewed; a user is walked through how to apply the findings of the report via a series of steps to address each of the three restoration and management questions. This process is intended to help the user access regionally-specific recommendations and strategies to plan and manage future Delta landscapes that can support desired ecological functions over the long term.
The goal of A Delta Renewed and this guide is not to recreate the Delta of the past. Rather, the objective is to understand how we can re-establish or mimic important natural processes and patterns within this altered system to support desirable ecological functions (such as healthy native fish populations, a productive food web, and support for endangered species), now and into the future.
This study synthesizes a diverse array of data to examine the ecological patterns, ecosystem functions, and hydrology that characterized a central portion of the Laguna de Santa Rosa during the mid-19th century, and to analyze landscape changes over the past 150 years. The primary purpose of this study was to help guide restoration actions and other measures aimed at reducing nutrient loads within this portion of the Laguna de Santa Rosa watershed.
In this report, we investigate how re-integrating components of oak woodlands into developed landscapes — “re-oaking” — can provide an array of valuable functions for both wildlife and people. Re-oaking can increase the biodiversity and ecological resilience of urban ecosystems, improve critical urban forest functions such as shade and carbon storage, and enhance the capacity of cities to adapt to a changing climate. We focus on Silicon Valley, where oak woodland replacement by agriculture and urbanization tells a story that has occurred in many other cities in California. We highlight how the history and ecology of the Silicon Valley landscape can be used as a guide to plan more ecologically-resilient cities in the Bay Area, within the region and elsewhere in California. We see re-oaking as part of, and not a substitute for, the important and broader oak woodland conservation efforts taking place throughout the state.
This study investigates the relative distribution, health, and regeneration patterns of two major stands of sycamore alluvial woodland (SAW), representing managed and natural settings. Using an array of ecological and geomorphic field analyses, we discuss site characteristics favorable to SAW health and regeneration, make recommendations for restoration and management, and identify next steps. Findings from this study will contribute to the acquisition, restoration, and improved management of SAW as part of the Santa Clara Valley Habitat Plan (VHP).
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.
With rising sea levels and the increased likelihood of extreme weather events, it is important for regional agencies and local municipalities in the San Francisco Bay Area to have a clear understanding of the status, composition, condition, and elevation of our current Bay shore, including both natural features and built infrastructure.
The purpose of this Bay shore inventory is to create a comprehensive and consistent picture of today’s Bay shore features to inform regional planning. This dataset includes both structures engineered expressly for flood risk management (such as accredited levees) and features that affect flooding at the shore but are not designed or maintained for this purpose (such as berms, road embankments, and marshes). This mapping covers as much of the ‘real world’ influence on flooding and flood routing as possible, including the large number of non-accredited structures.
This information is needed to:
- identify areas vulnerable to flooding.
- identify adaptation constraints due to present Bay shore alignments; and
- suggest opportunities where beaches, wetlands, and floodplains can be maintained or restored and integrated into flood risk management strategies.
The primary focus of the project is therefore to inform regional planners and managers of Bay shore characteristics and vulnerabilities. The mapping presented here is neither to inform FEMA flood designation nor is it a replacement for site-specific analysis and design.
The mapping consists of two main elements:
- Mapping of Bay shore features (levees, berms, roads, railroads, embankments, etc.) which could affect flooding and flood routing.
- Attributing Bay shore features with additional information including elevations, armoring, ownership (when known), among others.
SFEI delineated and characterized the Bay shore inland to 3 meters (10ft) above mean higher high water (MHHW) to accommodate observed extreme water levels and the commonly used range of future sea level rise (SLR) scenarios. Elevated Bay shore features were mapped and classified as engineered levees, berms, embankments, transportation structures, wetlands, natural shoreline, channel openings, or water control structures. Mapped features were also attributed with elevation (vertical accuracy of <5cm reported in 30 meter (100ft) segments from LiDAR derived digital elevation models (DEMs), FEMA accreditation status, fortification (e.g., riprap, buttressing), frontage (e.g., whether a feature was fronted by a wetland or beach), ownership, and entity responsible for maintenance. Water control structures, ownership, and maintenance attributes were captured where data was available (not complete for entire dataset). The dataset was extensively reviewed and corrected by city, county, and natural resource agency staff in each county around the Bay. This report provides further description of the Bay shore inventory and methods used for developing the dataset. The result is a publicly accessible GIS spatial database.
Over the past 150 years, lower San Francisquito Creek and the adjacent baylands have been modified for the sake of land reclamation and flood control. This study focused on developing an understanding of the magnitude of habitat change since the mid-19th century through comparisons of key historical and contemporary landscape-scale habitat features, as well as several key landscape metrics that relate to ecological functions and landscape resilience. The major findings from the analyses conducted for this study are as follows:
• Historically, the San Francisquito Creek Baylands included a mosaic of habitat types, including an extensive tidal marsh plain with salt pannes and an expansive tidal channel network, a broad bay flat, and a relatively wide contiguous low-gradient tidal-terrestrial transition zone.
• Since the late 19th century, a combination of land reclamation and the inland migration of the shoreline has resulted in a 55% decrease in tidal marsh area, a 67% decrease in total tidal channel length, a 40% reduction in channel flat area, a 20% increase in bay flat area, and a 95% decrease in tidal-terrestrial transition zone length.
• Land reclamation has also resulted in the creation of new features that did not exist in the area historically including tidal lagoons, non-tidal open water features, and non-tidal wetlands.
The findings from this study provide insight into the drivers for and magnitude of habitat change within the San Francisquito Creek Baylands, and can therefore help inform climate-resilient approaches for regaining some of the lost landscape features and ecological functions. Specific management recommendations developed from the study findings are as follows:
• The dramatic decrease in tidal marsh area and associated tidal channel length since the mid-1800s make tidal marsh restoration a high priority. To make restored areas sustainable over the long-term, restoration should include reestablishing regular tidal inundation as well as reestablishing a connection with San Francisquito Creek and the delivery of freshwater and fine sediment. Restoration efforts should focus on large contiguous areas with minimal infrastructure and should ideally be done sometime over the next decade to ensure the restored areas will have a chance of surviving the sharp increase in the rate of sea level rise that is predicted to occur around 2030 (Goals Update 2015).
• Similarly, the dramatic decrease in the tidal-terrestrial transition zone makes it a high priority for any restoration vision for this area. The transition zone provides distinct ecological services and marsh migration space, and is in need of restoration throughout the South Bay. Since most of the upland land along the historical tidal-terrestrial transition zone is currently developed, near-term restoration efforts should focus on creating transition zone habitats on the bayside of flood risk management levees (Goals Update 2015).
• The landscape metrics used in this study (tidal habitat area, tidal channel length, and tidal-terrestrial interface length) can be used to help design resilient landscape restoration and adaptation strategies around the mouth of San Francisquito Creek. Specifically, the metrics can be used to assess the long-term ecological benefit associated with various processes-based restoration approaches (i.e., approaches that create habitat features and establish physical processes required for habitat resilience). Additional useful landscape metrics are being developed as part of the Resilient Silicon Valley project (see Robinson et al. 2015).
Over the past century and a half, lower Novato Creek and the surrounding tidal wetlands have been heavily modified for flood control and land reclamation purposes. Levees were built in the tidal portion of the mainstem channel beginning in the late 1800s to convey flood flows out to San Pablo Bay more rapidly and to remove surrounding areas from inundation. Following levee construction, the wetlands surrounding the channel were drained and converted to agricultural, residential, and industrial areas. These changes have resulted in a considerable loss of wetland habitat, reduced sediment transport to marshes and the Bay, and an overall decreased resilience of the system to sea level rise.
In addition to tidal wetland modification, land use changes upstream in the Novato Creek watershed have resulted in several challenges for flood control management. Dam construction and increased runoff in the upper watershed have resulted in elevated rates of channel incision, which have increased transport of fine sediment from the upper watershed to lower Novato Creek. Channelization of tributaries and construction of irrigation ditches have likely increased drainage density in the upper watershed, also potentially contributing to increased rates of channel incision and fine sediment production (Collins 1998). Downstream, sediment transport capacity has been reduced by construction of a railroad crossing and loss of tidal prism and channel capacity associated with the diking of the surrounding marsh. As a result of the increased fine sediment supply from the watershed and the loss of sediment transport capacity in lower Novato Creek, sediment aggradation occurs within the channel, which in turn reduces the flood capacity of the channel, necessitating periodic dredging.
Currently, the Marin County Department of Public Works (MCDPW) is coordinating the Novato Watershed Program, which includes Marin County Flood Control and Water Conservation District, Novato Sanitary District, and North Marin Water District. Within lower Novato Creek, the Program is seeking to implement a new approach to flood control that includes redirecting sediment for beneficial use, reducing flood channel maintenance costs, restoring wetland habitat, and enhancing resilience to sea level rise. Included as part of this goal is the re-establishment of historical physical processes that existed before major channel modification, which in turn will re-establish historical ecological functions and help to create a tidal landscape that is resilient to increasing sea level.
This report explores the potential for integrating ecological functions into flood risk management on lower Novato Creek. It presents an initial vision of how ecological elements could contribute to flood protection, based on a broad scale analysis and a one day workshop of local and regional experts. The Vision is not intended to be implemented as is, but rather adapted and applied through future projects and analysis. Other actions (e.g., floodwater detention basins) may also need to be implemented in the interim to meet flood risk objectives.
As sea level rise accelerates, our shores will be increasingly vulnerable to erosion. Particular concern centers around the potential loss of San Francisco Bay’s much-valued tidal marshes, which provide natural flood protection to our shorelines, habitat for native wildlife, and many other ecosystem services. Addressing this concern, this study is the first systematic analysis of the rates of marsh retreat and expansion over time for San Pablo Bay, located in the northern part of San Francisco Bay.
• Over the past two decades, more of the marshes in San Pablo Bay have expanded (35% by length) than retreated (6%).
• Some areas have been expanding for over 150 years.
• Some marsh edges that appear to be retreating are in fact expanding rapidly at rates of up to 8 m/yr.
• Marsh edge change may be a useful indicator of resilience, identifying favorable sites for marsh persistence.
• These data can provide a foundation for understanding drivers of marsh edge expansion and retreat such as wind direction, wave energy, watershed sediment supply, and mudflat shape.
• This understanding of system dynamics will help inform management decisions about marsh restoration and protection.
• This study provides a baseline and method for tracking marsh edge response to current and future conditions, particularly anticipated changes in sea level, wave energy, and sediment supply.
Recommended next steps:
• This pilot study for San Pablo Bay marshes should be extended to other marshes in San Francisco Bay.
• These initial marsh expansion and retreat findings should be further analyzed and interpreted to improve our understanding of system drivers and identify management responses.
• A program for repeated assessment should be developed to identify and track changes in shoreline position, a leading indicator of the likelihood marsh survival.
The Sacramento-San Joaquin Delta has been transformed from the largest wetland system on the Pacific Coast of the United States to highly productive farmland and other uses embodying California’s water struggles. The Delta comprises the upper extent of the San Francisco Estuary and connects two-thirds of California via the watersheds that feed into it. It is central to the larger California landscape and associated ecosystems, which will continue to experience substantial modification in the future due to climate change and continued land and water use changes. Yet this vital ecological and economic link for California and the world has
been altered to the extent that it is no longer able to support needed ecological functions. Approximately 3% of the Delta’s historical tidal wetland extent remains wetland today; the Delta is now crisscrossed with agricultural ditches replacing the over 1,000 miles of branching tidal channels.
Imagining a healthy Delta ecosystem in the future and taking bold, concrete steps toward that future requires an understanding and vision of what a healthy ecosystem looks like. For a place as extensive, unique, and modified as the Delta, valuable knowledge can be acquired through the study of the past, investigating the Delta as it existed just prior to the substantial human modifications of the last 160 years. Though the Delta is irrevocably altered, this does not mean that the past is irrelevant. Underlying geologic and hydrologic processes still influence the landscape, and native species still ply the waters, soar through the air, and move across the land. Significant opportunities are available to strategically reconnect landscape components in ways that support ecosystem resilience to both present and future stressors.