Sea level rise impacts to the Bay Area are much more significant if sea level rise is three feet or more
As of 2024, 23% of Bay Area residents at risk from four feet of sea level rise live in Alameda County
As of 2024, 207,997 Bay Area residents lived in neighborhoods that would be at risk from just one foot of sea level rise
Introduction
How will sea level rise affect Bay Area communities?
As a result of global climate change caused by greenhouse gas emissions, sea levels are expected to rise over the coming decades. The Bay Area is not immune to this global trend that may seriously affect low-lying coastal areas across the world. Understanding which neighborhoods are most vulnerable from rising tides can help the region set key priorities when it comes to local and regional resilience planning, adaptation and future growth patterns.
Regional Performance
Bay Area development patterns are neither increasing nor decreasing the share of regional population at risk from sea level rise.
Depending on the magnitude of sea level rise over the coming decades, between 2.7% and 6.5% of Bay Area residents may be vulnerable to sea level rise. While this is just a small share of the region's population, the impacts to these communities may be dramatic. There may be broader consequences felt beyond these communities' borders from impacts to infrastructure and other regional assets. Looking at historical growth patterns since 1990, the share of the region's population living in areas that are projected to be inundated by sea level rise has increased slightly.
In 1990, 371,438 Bay Area residents (6.2% of total regional population) lived in areas at risk from four feet of sea level rise
In 2024, 493,980 Bay Area residents (6.5% of total regional population) lived in areas at risk from four feet of sea level rise
Historical Trend for Vulnerability to Sea Level Rise
Local Focus
While no Bay Area county is immune from sea level rise, residential development in Marin and Solano counties is particularly impacted.
The unique geography of each Bay Area county, combined with the location of existing residential development, strongly influences how many residents may be vulnerable to future sea level rise. Marin County faces the greatest risk, with much of its population concentrated in low-lying areas along the Bay shoreline. Based on 2024 estimates, approximately 18 percent of Marin's population could be exposed to inundation from a one-foot rise in sea level. Conditions are only slightly better in neighboring Solano County, where the corresponding figure is 11 percent.
As of 2024, 18% of Marin County residents live in neighborhoods that are considered vulnerable to just one foot of sea level rise
As of 2024, 11% of Solano County residents live in neighborhoods that are considered vulnerable to just one foot of sea level rise
Population at Risk of Impacts from Sea Level Rise (2024) - 1 Foot
Impacted Land Area
Population at Risk of Impacts
of Neighborhoods at Risk
Sources & Methodology
Projected areas of inundation for the Bay Area were developed by the San Francisco Bay Conservation and Development Commission (BCDC) as part of its Adapting to Rising Tides (ART) Bay Area Sea Level Rise and Shoreline Analysis Mapping Project (2017), at one-foot intervals ranging from one to four feet of sea level rise. This mapping covers the nine Bay Area counties and reflects the most detailed, locally modeled sea level rise projections available for the region. Note that the inundation data covers only the eight bodies of water under the jurisdiction of BCDC: Suisun Bay, San Pablo Bay, Honker Bay, Richardson Bay, San Rafael Bay, San Leandro Bay, Grizzly Bay and San Francisco Bay itself. Inundation along the Pacific Ocean and the Sacramento–San Joaquin Delta is not covered here.
BCDC's original inundation data are delivered as high-resolution rasters; these were converted to footprint polygons and intersected with water-clipped 2020 U.S. Census tract boundaries to determine the acreage of each tract inundated under each scenario. Because water-clipped tract boundaries already exclude existing open water (e.g., bays, sloughs), the resulting land area — rather than the tract's total (unclipped) area — is used as the denominator when calculating the percentage of a tract inundated under each future sea level rise scenario. A tract's residents are considered affected by sea level rise if at least 10 percent of the tract's (water-clipped) land area is inundated under a given scenario.
Population by census tract is drawn from multiple sources spanning 1990 to the most recent year available (currently 2024): 1990–2010 population comes from the Integrated Public Use Microdata Series National Historical Geographic Information System (IPUMS NHGIS) (originally reported for 2010 census block groups), and 2013 onward comes from the Census Bureau's American Community Survey 5-year estimates (Table B01003). All years are converted to a consistent set of 2020 census tract boundaries using a population-weighted crosswalk from IPUMS NHGIS, so that population and inundation figures can be compared consistently over time on the same tract geography.
This analysis does not attempt to model periodic or temporary flooding from extreme weather events, storm surge or king tides — it reflects only the permanent inundation scenarios modeled by BCDC's ART project. More information on the underlying methodology is available from the Bay Area Sea Level Rise Analysis and Mapping Project (2017).
San Francisco Bay Conservation and Development Commission/Metropolitan Transportation Commission ART (Adapting to Rising Tides) Bay Area Sea Level Rise Analysis and Mapping Project (2017)
IPUMS NHGIS, University of Minnesota
1990-2020
U.S. Census Bureau: American Community Survey
2013-2024
Table B01003