Palo Alto staff told the Climate Action and Sustainability Committee they have advanced vulnerability assessment tools, are constructing a horizontal levee pilot at the regional water quality control plant and will participate with Santa Clara County in a county-led subregional shoreline adaptation plan funded by an Ocean Protection Council grant.

Julie Weiss, the city's watershed protection manager, reviewed the city's vulnerability assessment and explained that planning now for long-term conditions is appropriate because both higher bay elevations and rising shallow groundwater will affect utilities, foundations, transportation and urban forest over the coming decades. "There is a lot of interesting content in the vulnerability assessment, but the key takeaway is that it's appropriate for us to start planning now for future conditions that we'll see near the end of the century," Weiss said.

Staff described a horizontal levee pilot that has broken ground at the regional water quality control plant, calling it a nature-based alternative to traditional levees, planted with native species and irrigated with treated wastewater. Weiss said the pilot is less than an acre but "mighty in its importance to the Greater Bay Area" because it will inform how future horizontal levees are permitted, designed and maintained. The city will monitor the pilot for five years post-construction and expects to use early lessons to inform subregional planning.

Elise (policy and public education manager) summarized SB 272, passed in 2023, which requires local governments along the Bay to develop sea-level-rise adaptation plans by 2034 and noted the Bay Conservation and Development Commission's Regional Shoreline Adaptation Plan (RSAP) provides detailed subregional plan elements. Santa Clara County has been awarded $2,600,000 from the Ocean Protection Council to lead development of a countywide subregional plan; staff said the county-led effort will include CEQA work, community engagement and economic impact assessment and is planned to run roughly 2026-2029. Staff said Palo Alto's existing vulnerability assessment will be incorporated into the county-led effort.

Public comment raised a technical question about the 36-inch sea-level-rise scenario shown on maps. Stephen Rosenblum asked whether that 36-inch figure was based on a 1.5'C or 2.0'C warming scenario. Staff replied that 36 inches is considered reasonable under current emissions projections, that the map uses 2024 projections (updated about a year ago) and offered to provide the Ocean Protection Council table used as a source.

Council members asked how the county plan specifically helps Palo Alto. Staff said partnering with the county provides resources Palo Alto lacks (a spending strategy, economic analysis and CEQA coverage) and fosters regional coordination on strategies and roles. Staff also noted that a prior U.S. Army Corps feasibility study did not account for the value of some local assets in its cost-benefit model, and that new approaches and regional engagement could prompt a re-opening of that analysis.

Staff said committee members will see more detailed work as the county-led planning effort begins next month and that the city will continue monitoring and staff education around sea-level-rise adaptation.