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The California Ocean Protection Council (OPC) adopted the State of California Sea Level Rise Guidance: 2024 Science and Policy Update (2024 Guidance), providing updated science and policy recommendations that will help California coastal communities and ecosystems build resilience to the impacts of sea level rise.

The latest update builds on a previous draft released in 2018. Since then, there have been significant advancements in scientific understanding and abilities to project future sea level rise levels—and this latest guidance document provides communities and the public the latest up-to-date information. For example, a National Report was released updating sea level rise scenarios for the United States, based on global projections.

This national update served as an opportunity for updating and revisiting California’s sea level rise guidance, merging new findings with the best available science specific to California. Now, the latest 2024 Guidance includes updated sea level rise scenarios and a precautionary stepwise process for incorporating the impacts of rising seas into planning and projects for a range of communities.

“Sea level rise is happening across the world, and California is no exception,” said OPC Chair and California Natural Resources Agency Secretary Wade Crowfoot. “Our updated Guidance will help our coastal communities and land managers understand these impacts so that we can protect our residents, infrastructure and natural systems. With clear planning and decisive action, we can ensure that residents, the economy and environment along our incredible coast can continue to thrive as sea levels rise.”

The latest 2024 Guidance was updated by OPC, in partnership with the California Ocean Science Trust and an interdisciplinary Sea Level Rise Science Task Force. Today’s adoption follows a 45-day public comment period where feedback was provided from throughout the state, and state agencies, local governments, private sector partners, non-profit organizations, and California Native American tribes contributed time and expertise to help shape the final draft.

“Failure to adequately prepare now will have consequences for public health and safety, wildlife and habitats, public access, and critical infrastructure,” said OPC’s Executive Director Jenn Eckerle. “It will also disproportionately impact communities already burdened by social and environmental injustice. Taking meaningful and proactive adaptation actions now is essential to reduce costs in the future, and this Guidance provides an important roadmap for how we do that in California.”

Additional information on the 2024 Guidance can be found at the link, under Item 4 of the June 4 OPC meeting agenda.

Top line findings from the 2024 Guidance:

• Land movement, either rising or sinking, is the primary driver of local variations in sea level rise across the state.
• There is now greater certainty in the amount of sea level rise expected in the next 30 years, with a statewide average of 0.8 feet of rise projected by 2050. By 2100, statewide sea levels are expected to rise between 1.6 feet and 3.1 feet, and even higher amounts cannot be ruled out.
• Beyond 2100, the range of sea level rise becomes increasingly large due to uncertainties associated with physical processes, such as earlier-than-expected ice sheet loss and resulting future sea-level rise. By 2150, statewide sea levels may rise from 2.6 feet to 11.9 feet, although even higher amounts are possible.
• Today’s coastal storms provide a glimpse into our future in which storm events will become more damaging and dangerous as climate change and sea level rise continues. When combined with extreme storms and higher tides, sea level rise will result in accelerated cliff and bluff erosion, coastal flooding and beach loss, and mobilization of subsurface contaminants. Sea level rise will increase the exposure of communities, assets, services and culturally important areas to significant impacts from coastal storms.
• Sea level rise will increase the frequency of coastal flooding events, which occur when sea level rise amplifies short-term elevated water levels associated with higher tides, large storms, El Niño events, or when large waves coincide with high tides. California communities need to be aware of and prepared for a likely rapid increase in the frequency of coastal flooding in the next decade, even beyond the increases in coastal flood frequency already occurring.
• Groundwater rise poses a threat to below-ground infrastructure and freshwater aquifers under future sea level scenarios. In areas with shallow unconfined groundwater, the water table will generally rise with sea level, depending on local geomorphology. Rising groundwater may mobilize subsurface contaminants in soils, expose underground infrastructure to corrosive saltwater, and put freshwater aquifers at risk of saltwater intrusion. The low-lying Sacramento-San Joaquin Delta, which supplies fresh water to two-thirds of the state’s population and millions of acres of farmland, is particularly vulnerable to saltwater intrusion into groundwater aquifers.