Adapting to Sea Level Rise in Hayward, California
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Posted byJessica Hitt
The Hayward shoreline, located along east San Francisco Bay, is susceptible to inundation from wave action and flooding. Increasing sea level, which could rise by 13 inches in 2050 and 32 inches in 2100 in San Francisco, further threatens the area. To assess the impacts of anticipated sea level rise along the Hayward shoreline, the Hayward Area Shoreline Planning Agency (HASPA) commissioned a study by an engineering consulting firm, Philip Williams and Associates (PWA; now ESA), to evaluate vulnerable infrastructure and examine strategies to protect wetlands and shoreline development. HASPA and partners have also recently released the Hayward Regional Shoreline Adaptation Master Plan to address recommendations set forth in PWA’s report and further prepare the shoreline for sea level rise.
In the San Francisco Bay, sea levels are estimated to rise between 7–13.2 inches by 2050 and between 14–32.4 inches by 2100 under moderate emissions scenarios (RCP 4.5), which could expose the shoreline to escalating wave action and flooding. These sea level rise projections, provided by the 2018 update of the State of California Sea Level Rise Guidance report, represent a 67% probability of sea level rise above 1991–2009 mean sea levels.
The Hayward shoreline extends from San Leandro Creek to the Alameda Creek Flood Control Channel in east San Francisco Bay. In 1970, HASPA, which consists of the City of Hayward, the Hayward Area Park and Recreation District, and the East Bay Regional Park District, was established to “coordinate agency planning activities and adopt and carry out improvement of the Hayward shoreline for future generations.” HASPA has helped purchase, preserve, and restore over 3,150 acres along the Hayward shoreline. Several successful wetland mitigation areas are located along the shoreline and form a tidal buffer that helps protect public and private infrastructure.
In response to projected sea level rise scenarios, HASPA commissioned a preliminary study by ESA to evaluate the impact of anticipated sea level rise on shoreline resources and the actions that can be taken to protect wetlands and shoreline development.
The HASPA Sea Rise Study Area comprises a 4.3 mile-long stretch of land, north of Highway 92 to San Leandro Creek. In order to assess the impact of anticipated sea level rise on the Sea Rise Study Area, ESA compared various sea level rise predictions and their appropriate interpretations; explored shoreline, marsh, and channel responses to sea level rise; and identified vulnerable properties. ESA also looked at state guidance for adaptation planning and developed four potential adaptation strategies for HASPA to implement:
- Hold the Line: protect land and infrastructure from erosion, inundation, and flooding through the use of levees and seawalls;
- Realignment: move the levee to a new location further inland to allow marshes and mudflats to naturally migrate landward;
- Gradual Steepening: combine the “hold the line” and “realignment” options to create a more sustainable shoreline that can accrete vertically and does not migrate landward too rapidly; and
- Diffuse Armoring: use a modified “hold the line” option where wave erosion buffers that emulate natural backshore buffering processes are utilized.
More descriptive results of the ESA assessment, as well as cost estimates for the adaptation strategies, are summarized in their report.
ESA also recommended conducting a more detailed assessment of coastal hazards to specific infrastructure and, using this information, develop a Shore Realignment Master Plan that includes the design and implementation of specific adaptation measures. To address these recommendations, HASPA kicked off a project in 2019 to develop a Shoreline Adaptation Master Plan to determine the policies and projects necessary to prepare the area for the impacts of sea level rise. HASPA member agencies collaborated to secure a $509,000 grant from Caltrans to develop the plan. HASPA has worked with a number of partners to develop this project, including the San Francisco Bay Conservation and Development Commission (BCDC), U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, South Bay Salt Pond Project, Oro Loma Wastewater Treatment Plant, East Bay Dischargers Authority, and the University of California, Berkeley. Arcadis and Scape were hired to develop a background study, conduct a public online survey, and develop a sea level rise model that included groundwater emergence. The plan examines transportation, natural systems, and infrastructure along the shoreline and has four major goals: (1) create a resilient shoreline environment for people and ecology; (2) enhance the shoreline to reduce risk to critical infrastructure and built assets; (3) build social resilience in the community; and (4) build capacity for future generations to adapt to climate change.
Adaptation strategies developed for the plan range from engineered solutions to non-structural (e.g., managed retreat, grants, and policies) and nature-based strategies (e.g., marsh restoration and beach nourishment). Engineered strategies include FEMA-certified levees with pump stations that are accompanied by horizontal and ecotone levees to create a transitional zone between the ocean and upland areas. In addition, a local bridge will be transitioned into a causeway so that water can flow under the elevated structure.
Outcomes and Conclusions
The Hayward Regional Shoreline Adaptation Master Plan was released in October 2020. Once an Environmental Impacts Report is released for the plan, HASPA will create operations and management plans to detail implementation steps, including task responsibilities and monitoring processes.
HASPA and partners are currently looking at a phased approach for implementing adaptation strategies with the hope of beginning small pilot projects within the next 10 years. They are looking at funding sources such as the San Francisco Bay Restoration Authority for these projects. Aside from funding and staffing limitations, implementation has been challenged by local regulations that slow the permitting process for levee repairs and maintenance. In some cases, obtaining permits to do repair work on levees has taken years, and beach nourishment technically constitutes “filling” of the Bay, which is restricted. BCDC has considered amending some of these regulations. However, they have said that permitting would occur first for the pilot projects before larger projects are allowed to take place. HASPA has found that engaging stakeholders early and often helped to facilitate adaptation action. Due to COVID-19, there have been some recent challenges associated with virtual outreach (e.g., no virtual community meetings), however, HASPA has still received substantial survey input in the midst of the pandemic.
Kershner, J. (2021). Adapting to Sea Level Rise in Hayward, California [Case study on a project of ESA]. Version 2.0. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: https://www.cakex.org/case-studies/adapting-sea-level-rise-hayward-california (Last updated October 2021 )