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The goals of the Mission Bay Historical Ecology Reconnaissance Study were to collect and compile high-priority historical
data about the Mission Bay landscape, identify sources that could help to develop a deeper understanding of early
ecological conditions, and to identify future possible research directions based on the available data. This technical
memorandum is intended to document the archives consulted during the reconnaissance study, summarize the collected
and compiled data, and to identify potential next steps. A separate technical presentation to project staff and advisors will
summarize the preliminary findings and questions generated from a review of the historical dataset. Ultimately, this
research is intended to support the San Diego Audubon Society’s Mission Bay Wetlands Conceptual Restoration Plan (CRP)
and the ReWild Mission Bay project.
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.
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.
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.
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.
This report proposes a multi-faceted redesign of the South San Francisco Bay shoreline at the interface with Calabazas and San Tomas Aquino creeks. Recognizing the opportunities presented by changing land use and new challenges, such as accelerated sea-level rise, we explore in this report a reconfigured shoreline that could improve ecosystem health and resilience, reduce maintenance costs, and protect surrounding infrastructure.
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.
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).
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.
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).
The Tijuana River Valley Historical Ecology Investigation addresses a regional data gap by reconstructing the landscape and ecosystem characteristics of the river valley prior to the major modifications of the late 19th and 20th centuries. The research presented here, funded by the California State Coastal Conservancy, supplies foundational information at the regional and system scale about how the Tijuana Estuary, River, and valley looked and functioned in the recent past, as well as how they have changed over time. The ultimate goal of this study is to provide a new tool and framework that, in combination with contemporary research and future projections, can support and guide ongoing restoration design, planning, and management efforts in the valley.
This document provides some of the scientific foundation needed to guide planning for urban biodiversity in the Santa Clara Valley region, grounded in an understanding of landscape history, urban ecology and local setting. It can be used to envision the ecological potential for individual urban greening projects, and to guide their siting, design and implementation. It also can be used to guide coordination of projects across the landscape, with the cooperation of a group of stakeholders (such as multiple agencies, cities and counties). Users of this report may include a wide range of entities, such as local nonprofits, public agencies, city planners, and applicants to the Open Space Authority’s Urban Open Space Grant Program.