1001 Bridgeway, #484,
Sausalito, CA 94965 USA
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Sea levels in California are rising at an accelerating pace. Here's what that means for our coasts, communities, and infrastructure.
We're on track for the intermediate or high scenario.
The State of California Sea Level Rise Guidance (OPC 2024) provides the best available science on SLR for California. The table above is from Appendix 2 (p. 88)
What are now infrequent Bay flood events will become more frequent.
With 3.5 feet of SLR, what is now a 100-year storm event will become an everyday occurrence (high tide). SLR is projected to increase the frequency of nuisance high tide flooding from a couple days per year in 2020 to nearly 20 days per year in 2050 (see graph).
Rates of sea level rise (SLR) have increased three-fold over recent decades.
Future scenarios of SLR
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BCDC recommends planning for 0.8 ft of SLR by 2050 and considering rates of 3.1 to 6.6 ft of rise by the year 2100.
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With 3.5 feet of SLR, what is now a 100-year storm event will become an everyday occurrence (high tide).
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SLR is projected to increase the frequency of nuisance high tide flooding from a couple days per year in 2020 to nearly 20 days per year in 2050.
Subsidence: Land is also shrinking
Vertical land motion (VLM), or subsidence, for San Francisco is -0.1 inches/decade, or -0.25 mm/year of subsidence ((OPC 2024; Appendix 3; Table 15). Small compared to current and projected future rates of SLR.
Rates of rise have increased significantly over the past decades.
Most recent data for Global mean sea level (not adjusted for local vertical land motion, or VLM)
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Over the early to mid-20th C, 0.5 ft/century = 1.5 mm/yr (1900 to 1993)
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By 1993: 2.0 mm/year
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Current Global SLR rate (2024) = 4.4 mm/year
Similar source, different methods:
NASA Analysis Sees Spike in 2023 Global Sea Level Due to El Niño – NASA Sea Level Change Portal