CA Sea Change Atlas
CA Sea Change Atlas
County Profiles San Mateo County
Data as of 2026-10-22

Sea level rise · San Mateo County, CA

Sea level rise

Visualize sea level rise exposure with this snapshot. Consider incorporating this data into all community planning strategies. In many communities, rising sea levels are already increasing the impacts of high tide flooding and storm surge events.

Projections for the Alameda tide gauge, assigned to San Mateo County · Exposure at 2, 4, 6, 8, 10 ft above MHHW

In this profile

  1. People at Risk 01
  2. Flooded Facilities Can't Provide Critical Services 02
  3. Being Underwater Is Not a Good Business Plan 03
  4. Creating a Better Future: Yes, It Can Be Done 04
  5. When Is the Time to Act? Now! 05
  6. Digging Deeper 06
  7. About this data 07

People at Risk

Rising population numbers exacerbate potential flooding risk; impacts can be even greater when social vulnerability factors (age, income, capabilities) are involved, as these citizens may not be able to adequately prepare and respond.

View on map for People at Risk: opens the sea level rise layer and population density for San Mateo County in a new tab

11.5%

(85,484 people) of San Mateo County’s total population lives in areas exposed to just 2 ft of sea level rise. As is already the case in many parts of the country, these areas are the first to experience impacts.

Residents exposed at each increment of sea level rise.

Population: 2 ft 85,484, 4 ft 107,427, 6 ft 124,244, 8 ft 138,861, 10 ft 152,673. Aged 65 and over: 2 ft 13,404, 4 ft 16,045, 6 ft 17,966, 8 ft 19,609, 10 ft 21,305. Below the poverty line: 2 ft 5,577, 4 ft 7,179, 6 ft 8,369, 8 ft 9,308, 10 ft 10,421. 0 50k 100k 150k 200k 85,484 Population 13,404 Aged 65 and over 5,577 Below the poverty line
Sea level rise
2 ft

Residents exposed at each increment of sea level rise: data table

Category2 ft4 ft6 ft8 ft10 ft
Population, ocean-connected4,77721,483122,610137,899152,444
Population, including low-lying areas85,484107,427124,244138,861152,673
Aged 65 and over, ocean-connected5462,21617,72119,46721,277
Aged 65 and over, including low-lying areas13,40416,04517,96619,60921,305
Below the poverty line, ocean-connected3651,2398,2469,26010,410
Below the poverty line, including low-lying areas5,5777,1798,3699,30810,421
Sources Census ACS 5-year estimates (2020–2024) (2024) Census 2020 tabulation blocks (TIGERweb) (2020) NOAA Sea Level Rise Viewer inundation extents (2026)

Flooded Facilities Can't Provide Critical Services

Fire and police stations. Hospitals. Shelters. These facilities play a central role in response and recovery. Understanding future exposure can help reduce damages and the conditions that make these services unavailable.

View on map for Flooded Facilities Can't Provide Critical Services: opens the sea level rise layer and critical facilities for San Mateo County in a new tab

5.1%

(16 of 312 facilities) of San Mateo County’s critical facilities are in areas exposed to just 2 ft of sea level rise. These areas are the first to experience impacts.

Facilities exposed at each increment of sea level rise.

Schools (222 total): 2 ft 0 exposed (13 with low-lying areas), 4 ft 5 exposed (19 with low-lying areas), 6 ft 28 exposed (28 with low-lying areas), 8 ft 29 exposed (29 with low-lying areas), 10 ft 30 exposed (30 with low-lying areas). Police stations (21 total): 2 ft 0 exposed (1 with low-lying areas), 4 ft 0 exposed (1 with low-lying areas), 6 ft 4 exposed (4 with low-lying areas), 8 ft 4 exposed (4 with low-lying areas), 10 ft 6 exposed (6 with low-lying areas). Fire stations (61 total): 2 ft 0 exposed (2 with low-lying areas), 4 ft 5 exposed (8 with low-lying areas), 6 ft 11 exposed (11 with low-lying areas), 8 ft 12 exposed (13 with low-lying areas), 10 ft 16 exposed (16 with low-lying areas). Medical facilities (8 total): 2 ft 0 exposed (0 with low-lying areas), 4 ft 1 exposed (1 with low-lying areas), 6 ft 1 exposed (1 with low-lying areas), 8 ft 1 exposed (1 with low-lying areas), 10 ft 1 exposed (1 with low-lying areas). 0 50 100 150 200 13 1 2 0 Number of facilities of each type Schools Police stations Fire stations Medical facilities
Sea level rise
2 ft

Facilities exposed at each increment of sea level rise: data table

CategoryTotal2 ft exposed4 ft exposed6 ft exposed8 ft exposed10 ft exposed
Schools22205282930
Schools, including low-lying areas2221319282930
Police stations2100446
Police stations, including low-lying areas2111446
Fire stations6105111216
Fire stations, including low-lying areas6128111316
Medical facilities801111
Medical facilities, including low-lying areas801111
Sources USGS National Structures Dataset (2025-05-09) NOAA Sea Level Rise Viewer inundation extents (2026)

Being Underwater Is Not a Good Business Plan

Flood-related losses of services, revenues, and salaries can hit a community hard.

View on map for Being Underwater Is Not a Good Business Plan: opens the sea level rise layer and jobs density for San Mateo County in a new tab

18.0%

(76,641 jobs) of San Mateo County’s jobs are in areas exposed to just 2 ft of sea level rise.

Jobs in areas exposed at each increment of sea level rise.

2 ft: Ocean-connected 10,068 jobs, Additional, in low-lying areas 66,573 jobs. 4 ft: Ocean-connected 64,902 jobs, Additional, in low-lying areas 56,559 jobs. 6 ft: Ocean-connected 171,763 jobs, Additional, in low-lying areas 1,169 jobs. 8 ft: Ocean-connected 191,665 jobs, Additional, in low-lying areas 977 jobs. 10 ft: Ocean-connected 205,277 jobs, Additional, in low-lying areas 322 jobs. Total jobs 0 50k 100k 150k 200k 76,641 121,461 172,932 192,642 205,599 2 ft 4 ft 6 ft 8 ft 10 ft

Jobs in areas exposed at each increment of sea level rise: data table

CategoryOcean-connectedAdditional, in low-lying areas
2 ft10,068 jobs66,573 jobs
4 ft64,902 jobs56,559 jobs
6 ft171,763 jobs1,169 jobs
8 ft191,665 jobs977 jobs
10 ft205,277 jobs322 jobs
Sources LEHD LODES8 workplace area characteristics (2023) Census 2020 tabulation blocks (TIGERweb) (2020) NOAA Sea Level Rise Viewer inundation extents (2026)

Creating a Better Future: Yes, It Can Be Done

Make it a goal: more natural areas (wetlands, forests, parks, dunes, etc.) to absorb floodwaters and protect the community, and less development in flood-prone areas. Consider not only today’s floodplain, but also the floodplain extent projected for the future.

View on map for Creating a Better Future: Yes, It Can Be Done: opens the sea level rise layer and natural areas for San Mateo County in a new tab

32.3%

(7.5 of 23.2 square miles) of the land inundated in San Mateo County at 2 ft of sea level rise would be natural: wetland or upland.

Land cover inundated at each increment of sea level rise.

2 ft: Wetlands 7.4 sq mi, Upland 0.1 sq mi, Other 15.7 sq mi. 4 ft: Wetlands 8 sq mi, Upland 0.2 sq mi, Other 21.5 sq mi. 6 ft: Wetlands 8.3 sq mi, Upland 0.2 sq mi, Other 25.6 sq mi. 8 ft: Wetlands 8.4 sq mi, Upland 0.3 sq mi, Other 28.1 sq mi. 10 ft: Wetlands 8.4 sq mi, Upland 0.4 sq mi, Other 30.3 sq mi. % natural 0 10 20 30 32.3% 27.6% 24.9% 23.6% 22.5%Square miles inundated 2 ft 4 ft 6 ft 8 ft 10 ft

Land cover inundated at each increment of sea level rise: data table

CategoryWetlandsUplandOther
2 ft7.4 sq mi0.1 sq mi15.7 sq mi
4 ft8 sq mi0.2 sq mi21.5 sq mi
6 ft8.3 sq mi0.2 sq mi25.6 sq mi
8 ft8.4 sq mi0.3 sq mi28.1 sq mi
10 ft8.4 sq mi0.4 sq mi30.3 sq mi
Sources NOAA C-CAP regional land cover (1996–2021) NOAA Sea Level Rise Viewer inundation extents (2026)

When Is the Time to Act? Now!

Because a number of factors are involved, sea level rise projections are often expressed as scenarios. For projects involving structures with a long lifespan or where a loss would be catastrophic (power plants, ports, hospitals), the higher sea level rise scenarios should be considered. For projects with a shorter lifespan (bike paths, golf courses, parks), lower sea level rise scenarios may be appropriate.

Projections at the Alameda gauge, by scenario

Feet above 2000, by year

Projected sea level rise at the Alameda tide gauge, 2000 to 2150, by scenario Feet of sea level rise above 2000, for the Intermediate, Intermediate-High and High scenarios. The year each increment is reached is in the table. 2000 2020 2040 2060 2080 2100 2120 2140 4 ft 6 ft 8 ft 10 ft 2 ft Intermediate reaches 2 ft in 2088 Intermediate-High reaches 2 ft in 2070 High reaches 2 ft in 2062
Sea level rise
2 ft

2 ft is reached in:

Intermediate
2088
Intermediate-High
2070
High
2062

Feet above 2000, in 2050 and 2100

Projected sea level rise at the Alameda tide gauge in 2050 and 2100, by scenario Feet above 2000. 2050: Intermediate 0.6¤ ft, Intermediate-High 0.9¤ ft, High 1.1 ft. 2100: Intermediate 2.8 ft, Intermediate-High 4.4 ft, High 6.2 ft. 0 2 4 6 8 0.6¤ 0.9¤ 1.1 2050 2.8 4.4 6.2 2100

¤ Under 1 ft, the lowest level the map shows.

Year each increment is reached

Sea level riseIntermediateIntermediate-HighHigh
2 ft208820702062
4 ft212020962082
6 ftafter 215021222098
8 ftafter 2150after 21502115
10 ftafter 2150after 21502137
Sources California Ocean Protection Council, State of California Sea Level Rise Guidance: 2024 Science & Policy Update, Appendix 2 (2024)

Digging Deeper

Go further with San Mateo County's sea level rise in the atlas's other tools.

See San Mateo County on the map

Opens the map on the county, highlighted, with the sea level rise layer switched on.

Compare the flood and sea level rise resources

Explore descriptions fo the different resources available, including those listed in the OPC guidance.

About this data

Data, methods and citation

Snapshot
2026-10-22 · all snapshots
Methodology
Version 1 · what changed
Tide gauge
Alameda (OPC 2024, Appendix 2)
Scenarios
Intermediate, Intermediate-High, High

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Recommended citation

California Sea Change Atlas. (2026, October 22). San Mateo County coastal county profile: Sea level rise. https://seachangeatlas.org/county-profiles/county/san-mateo/2026-10-22/sea-level-rise/

SourcePeriod coveredRetrieved
Census ACS 5-year estimates (2020–2024)20242026-10-22
Census 2020 tabulation blocks (TIGERweb)20202026-10-22
NOAA Sea Level Rise Viewer inundation extents20262026-10-22
USGS National Structures Dataset2025-05-092026-10-22
LEHD LODES8 workplace area characteristics20232026-10-22
NOAA C-CAP regional land cover1996-01-01 to 2021-12-312026-10-22
California Ocean Protection Council, State of California Sea Level Rise Guidance: 2024 Science & Policy Update, Appendix 220242026-10-22