San Francisco Bay Shoreline Adaptation Atlas

As sea levels continue to rise, communities will need to adapt the San Francisco Bay shoreline to create greater social, economic, and ecological resilience. A critical tool for this process is a science-based framework for developing adaptation strategies that are appropriate for the diverse shoreline of the Bay and that take advantage of natural processes. This project proposes such a framework: Operational Landscape Units for San Francisco Bay.

About the Operational Landscape Unit (OLU) framework

Operational Landscape Units (OLUs) are a practical way to manage the physical and jurisdictional complexity of the Bay shoreline. Home to beaches, wetlands, marinas, ports, landfills, lifeline infrastructure, residential neighborhoods and more, San Francisco Bay’s 650-kilometer (400-mile) shoreline is diverse, which means there is no one-size-fits-all solution to rising sea levels. The OLU framework divides the Bay shoreline into 30 distinct OLUs, geographic areas that share common physical characteristics. OLUs cross traditional jurisdictional boundaries of cities and counties, but adhere to the boundaries of natural processes like tides, waves, and sediment movement. Taken as a whole, OLUs encompass the entire Bay shoreline, cover the region’s land area potentially vulnerable to future sea level rise, and represent areas along and adjacent to the shore for which geographically specific and science-based sea level rise adaptation strategies can be developed.

A key purpose of the OLU framework is to identify where natural and nature-based approaches, such as beaches, marshes, and subtidal reefs, can help create a resilient shoreline with multiple benefits. Nature-based approaches and hybrid measures that integrate nature with engineered structural approaches, may perform better than traditional engineered infrastructure, while costing less and providing co-benefits like new recreational opportunities and habitat for native species. Adaptation in each OLU will most likely require a combination of nature-based measures, traditional engineering, and non-structural or policy strategies.

Within the next few decades, flood events signaling sea level rise will likely trigger more efforts around the Bay to plan for adaptation, to control flooding, and to modify the shoreline. Using OLUs as a planning framework and prioritizing appropriate nature-based solutions within them, can help ensure that future adaptation actions are sustainable and confer the most benefits per dollar spent.

The San Francisco Bay Shoreline Adaptation Atlas report presents information about OLUs in four major chapters that summarize both the process of developing the OLUs and how the OLUs might be applied.

What is an Operational Landscape Unit?

Operational Landscape Units (OLUs) are connected geographic areas sharing certain physical characteristics that would benefit from being managed as a unit to provide particular desired ecosystem functions and services. OLUs can be identified anywhere across the earth’s surface, with their size and composition depending upon the landscape in question and the ecosystem functions and services of interest. For this project, we identify Baylands OLUs which we define as connected areas along the shoreline of San Francisco Bay with particular physical characteristics that should be managed as coherent units for nature-based sea-level rise adaptation.  

Baylands OLUs consist of landscape features such as rivers, floodplains, and wetlands, as well as elements of the built environment such as parking lots, landfills, and residential neighborhoods. The connections between the features of the Baylands OLUs are important: altering the movement of sediment or water in one part of an OLU is likely to have an impact elsewhere in the OLU. Because of these close connections, effective management of one feature within the OLU should require the consideration and management of the other connected features within the OLU.

Why natural and nature-based adaptation?

Natural and nature-based adaptation measures work with natural processes and landforms to provide protection for both ecosystems and the built environment and to support coastal resilience and risk reduction. Along our highly modified shorelines, natural and nature-based measures are also inherently hybrid approaches—engineered to mimic natural processes and also provide specific services such as coastal risk reduction and critical habitat.

Natural and nature-based approaches may have lower whole-life costs, provide more benefits to people, plants, and wildlife, and be more adaptable over time than conventional alternatives. However, knowledge about and confidence in the performance of natural and nature-based measures varies. Because nature-based measures have so much promise, they should continue to be piloted and monitored around the Bay, and their performance analyzed to inform continuous improvement in their design and implementation.

How to use the OLU framework

The OLU framework can be applied to adaptation planning at several levels, including by users with a regional view who are interested in understanding the places in the Bay where specific nature-based adaptation measures are suitable. This group may include federal and state government permit analysts and project applicants, non-governmental organizations, regional planners and agencies, and local government staff and officials who want to understand the range of suitable nature-based and other policy-based adaptation opportunities when evaluating project permits, investing in shoreline changes, and developing climate change policies and regulations. This report can also help these users identify opportunities for habitat restoration and endangered species recovery. In addition, the OLU concept can serve as a spatial framework for monitoring the health of wetlands over time, or as an organizing framework for governance and decision making for adaptation in general.

Adaptation measures explored in this project

Adaptation measures are specific interventions or ways to manage the shoreline, flooding, and sea level rise. They can be combined and implemented over time in a planned sequence (or “pathway”) that is appropriate to the landscape setting and, over time, helps to manage and reduce various coastal risks, including erosion, fluvial flooding, sea level rise, and combined (fluvial and tidal) flooding.

This project defines and describes more than two dozen adaptation measures that are potentially appropriate to the Bay’s OLUs. Four categories of adaptation measures are explored:

• Structural, natural and nature-based measures: physical landscape features that are created and evolve over time through the actions of environmental processes, or features that mimic characteristics of natural features but are created by engineering and construction (in concert with natural processes) to provide coastal protection and other ecosystem services.
• Structural, conventional physical (grey) infrastructure: physical features constructed by humans to provide coastal protection. Usually constructed with relatively hard materials such as concrete, rock, and steel, and without incorporation of biological components.
• Non-structural, policy and regulatory measures: utilizing laws, policies, and regulations such as permits, zoning, and general plans to influence future land use and the built environment to manage risk.
• Non-structural, financial measures: non-physical ways of creating financial incentives and disincentives to enable implementation of other structural and policy measures.

For more information, see Chapter 4: Adaptation measures in the San Francisco Bay Shoreline Adaptation Atlas report.