Yosemite Slough Neighborhood Adaptation Plan

What is the Yosemite Slough Neighborhood Adaptation Plan?

The Yosemite Slough Neighborhood Adaptation Plan (YSNAP) will recommend strategies to protect Bayview residents, businesses, and infrastructure from projected sea level rise and flooding between Hunters Point and Candlestick Point (see map). Strategies will include a mix of policy, engineered, event-based and nature-based solutions tailored to the neighborhood. The plan is a critical first step to obtaining state and federal funding related to sea level rise in the neighborhood.

Why is this work needed? Why is it important?

Bayview Hunters Point suffers from a history of inequitable planning and policy decisions. The YSNAP project aims to address this history by building community awareness, creating adaptation strategies with the neighborhood, and preparing for rising tides. Bayview Hunters Point is already vulnerable to stormwater and coastal flooding, today, and at risk to significant flooding from sea level rise in the near future. The latest science projects rising tides that are nearly one foot higher than current levels by the year 2050 and between 3 and 6.6 feet higher by 2100.

What is Yosemite Slough?

Yosemite Slough (rhymes with “blue”) is a water channel located between Hunters Point Naval Shipyard and Candlestick Point. It was part of a broader watershed, originating from what is now McLaren Park, that connected the former Yosemite Marsh and other natural springs with the San Francisco Bay. Yosemite Slough was once a biologically rich ecosystem that supported a variety of wildlife, including many migrating birds. (Source: California State Parks)

How does this relate to Candlestick Point State Recreation Area?

The immediate shoreline and some areas to the North and South are part of the Candlestick Point State Recreation Area (see map). The adjacent residential and commercial parcels are under the jurisdiction of the City and County of San Francisco. This planning process is sponsored by the City, but will be coordinated with State Parks plans.

What work has already been done at Yosemite Slough?

California State Parks and the California State Parks Foundation restored wetlands and built core infrastructure along the north shore of Yosemite Slough, including trails, perimeter boundary markers, and a parking lot. Literacy for Environmental Justice, a Bayview-based organization, helped plant thousands of native trees, shrubs, and perennials. In 2024, State Parks completed a shoreline stabilization study to inform future projects along the Park waterfront.

How is this related to the Hunters Point Shipyard?

Yosemite Slough is adjacent to the Hunters Point Naval Shipyard (HPNS). The Navy is responsible for environmental remediation of the Shipyard, which is considered a federal “superfund” site. Yosemite Slough is a separate superfund site with a different contamination profile.

What is being done about contamination?

The State Park area to the north of Yosemite Slough was remediated as part of the wetland restoration project. The U.S. Environmental Protection Agency (EPA) is working with various parties to design a cleanup strategy for the slough itself. The cleanup is expected to remove contaminated mud and replace it with clean materials. To maintain the restored wetland habitat and avoid recontamination, the cleanup plan must align with the cleanup of the HPNS Superfund Site. As of Fall 2024, the EPA estimates the cleanup of Yosemite Slough to begin in 2028.

What is sea level rise?

As the planet warms, glaciers and polar ice sheets melt, and ocean water expands in volume. Both factors are causing sea levels to rise. The warmer the planet, the faster sea levels will rise in response. When accounting for high tides and more extreme storms, San Francisco Bay levels are expected to rise between 3 and 6.6 feet by 2100.

How does sea level rise interact with stormwater flooding (flooding from rain) and groundwater flooding (flooding from water emerging above the land’s surface)?

Rain from extreme storms can exceed the capacity of the City’s stormwater infrastructure, leading to flooding and combined sewer discharges into the Bay. The intensity, duration, and frequency of extreme storms is expected to increase with climate change.

In areas with shallow groundwater, the water table will generally rise with sea level rise. Rising groundwater may mobilize subsurface contaminants in soils, expose underground infrastructure to corrosive saltwater, and put freshwater aquifers at risk of water intrusion. These risks depend on local conditions and require further study. The risks are of particular concern in the Bayview, much of which is at low elevation and built on porous landfill. (Source: Ocean Protection Council)

What is an adaptation plan? What does it mean to plan for “3.5 to 7 feet of projected sea level rise by 2100”?

A sea level rise adaptation plan is meant to limit damage to homes, communities, and assets related to sea level rise. A Plan’s strategies can include policy, engineered, event-based, and nature-based solutions.

The sea level rise planning process is incremental across a long timeframe (e.g., end of century) to account for uncertainty in projected future warming and physical processes (e.g., rapid ice sheet melt). In the San Francisco Bay Area, the State of California recommends planning for 3.1 to 6.6 feet of sea level rise by 2100, which also accounts for wave-driven processes and storm surge.

Due to the complexities of each neighborhood and climate change, there is no “one size fits all” approach. The adaptation plan will therefore mix and match different strategies to best suit the needs of the Yosemite Slough neighborhood.

What is a nature-based adaptation strategy?

Nature-based adaptation strategies enhance ecosystems and their resilience to climate change. When successful, nature-based solutions can protect and restore habitat, prevent wildlife loss, and create greener cities. In coastal areas, like around Yosemite Slough, nature-based solutions can help stabilize the shoreline, reduce erosion, filter pollutants, trap sediments, and provide wave breaks. (Source: Nature Based Exchange).

If the shoreline elevation is raised to adapt to sea level rise, will that trap water inland from stormwater flooding (“bathtub effect”)?

Coastal adaptation plans are required to reduce combined risks from rising tides, groundwater and stormwater inundation. Strategies that increase those risks will not be considered. One way to frame this work is that San Francisco has already benefitted from sea walls and elevated shorelines for more than 100 years. The difference now is that risks are increasing due to climate change.

What are Hunters Point Shipyard and Candlestick Point doing about sea level rise?

The development at Hunters Point Shipyard and Candlestick Point is required to have setbacks that respond to up to 5.5 feet of sea level rise above the Total Water Level (Base Flood Elevation + wave runup).

California State Parks recently completed a shoreline stabilization study to guide future adaptation within the State Recreation Area.

Both of these efforts will address sea level rise adaptation in the Alice Griffith neighborhood.