As climate change intensifies, major cities like San Francisco, East Palo Alto (EPA), and San Rafael are increasingly threatened by sea level rise. As a result, low-lying cities are at increased risk of flooding—a danger that many cities are proactively working to address.
The science behind this process lies in the buildup of greenhouse gas emissions over recent decades, which trap thermal radiation at Earth’s surface, melt permafrost and glaciers, and intensify oceanic thermal expansion. Although carbon dioxide naturally helps support life on Earth by keeping the planet warm enough for ecosystems to survive, excessive amounts trapped in the atmosphere amplify the greenhouse effect and cause harmful warming. In the worst-case scenario, if emissions continue to rise, the Pacific Ocean surrounding the Bay Area could rise by about a foot by 2025 and by three feet by 2100.
EPA is particularly vulnerable because they were built on former wetlands, which naturally sink and already experience flooding during high tides. They also have a limited storm drain system to mitigate flooding impacts.
Similarly, San Rafael, home to around 12,000 residents, faces similar risks due to its location besides a canal that flows into San Francisco Bay. Parts of the city are built on soil added to fill in wetlands, leaving the community at risk of substantial sinking.
Historic marshlands surrounding the San Francisco Bay are also under threat, facing more frequent flooding due to intensified tidal patterns. Because of sea-level rise, marshes are turning into open water or mudflats. The marshes along the northern and southern shores of the Bay are estimated to be underwater by 2100.
Despite the grim possibilities, local governments have established plans to prevent major damage. In Palo Alto, the city has created the Palo Alto Horizontal Levee Pilot Project, which utilizes nature-based flood protection systems that create slopes with marsh plants to protect communities from rising tides and storms. Unlike seawalls, living levees allow water to spread over the slope, reducing flood risk while also supporting wildlife habitats.
EPA is working with the San Francisquito Creek Joint Powers Authority and Menlo Park on the SAFER Bay Project. The project aims to reduce tidal flooding by installing levees and seawalls and to restore more than 550 acres of wetlands for protection and ecological benefits. California state bill 272 requires local shoreline cities, including East Palo Alto, San Francisco, and San Rafael, to create sea level rise adaptation plans by 2034.
“We are working on a bridge project and working on the SAFER Bay project. […] All working together to try to resolve the issue from upstream all the way to the downstream,” EP A’s city engineer Anwarbeg Mirza said.
In the late 1990s, East Palo Alto purchased Cooley Landing Park, adjacent to Bay Road, which has since been converted into an education center. In recent years, the city has conducted various studies, such as soil testing to measure contamination and assessing how groundwater rise with sea-level rise will impact the area.
“We are concerned about both things, not only sea level rise (SLR) but also about groundwater rise. We recently performed the addendum for the sea level rise around two months ago. […] The goal is to follow the original SLR long-term adaptation plan. This particular task is having to monitor groundwater, to see the rise of groundwater over time,” Mirza said.
“[Short adaptation plans] we are talking about raising the elevation in the north of the Bay Road and then adding more wetland areas south of the Bay Road,” Mirza added. Outside governmental programs, nonprofits like Save The Bay have helped protect and restore the San Francisco Bay. Save The Bay leads tidal marsh and wetland restoration, helps fund flood protection projects, and advocates for political change.
The cost of necessary adaptation and mitigation strategies is hefty. A regional report estimates that protecting Bay Area shorelines from sea level rise by 2050 will cost around $110 billion. Local governments can only fund five billion dollars, leaving a gap of approximately $105 billion. If governments fail to adopt a sea-level rise plan promptly, the estimated cost could soar to over $230 billion.
