State of California Sea Level Rise Guidance
The State of California Sea Level Rise Guidance: 2024 Science and Policy Update, developed and adopted by the Ocean Protection Council (OPC), is a key resource as California coastal and shoreline communities confront the growing challenges of sea level rise. This guidance updates and replaces the previous 2018 Guidance to incorporate the latest scientific research and offer a comprehensive framework for resilience planning. With projections showing that sea levels could rise nearly a foot by 2050 and potentially up to twelve feet by 2150, the document underscores the urgency of proactive planning and measures to prepare for a changing coastline. It provides updated scenarios and policy recommendations tailored to California’s unique coastline, ensuring that communities, planners, and decision-makers have the best available science to protect both people and ecosystems.
The 2024 Guidance is a forward-looking integration of the latest national projections and California-specific science to address the compounded risks of coastal storms, high tides, and groundwater rise. By offering updated scenarios and a precautionary approach, the guidance supports local governments and stakeholders in making informed decisions about adapting to the accelerating impacts of sea level rise. It also highlights the importance of equitable adaptation strategies to protect vulnerable communities. This comprehensive document is essential for safeguarding California’s coast and ensuring that its residents and natural systems can thrive amid rising seas.
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.
Topline 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.
Staff Contact
Justine Kimball
Senior Climate Change Program Manager
Justine.Kimball@resources.ca.gov