OPC, OST, and a task force release guidance to help California prepare for sea level rise

By Dom Kone

Today, the Council officially adopted and released the State of California Sea Level Rise Guidance: 2024 Science and Policy Update. Developed by the Ocean Protection Council (OPC), in close partnership with OST and a Scientific Task Force, this guidance provides updated scientific knowledge of statewide sea level rise and other coastal hazards (e.g. flooding), as well as practical approaches for state agencies, local governments, and communities to use this new science across their respective planning efforts.

The 2024 update is the fourth iteration of the statewide sea level rise guidance following OPC’s commitment to update the guidance every 5 years to keep pace with scientific understanding. In 2018, OPC released the previous guidance update, which was based on the technical findings of the 2017 Rising Seas Report, developed by an OPC Science Advisory Team Working Group convened by OST. Since 2018, the scientific community has made significant improvements in its ability to understand and project future sea level rise. To take advantage of this progress, OPC and OST convened a Scientific Task Force to update California’s guidance to reflect those advancements. The 2024 guidance, however, is unique from previous iterations because for the first time it presents the science alongside actionable policy recommendations that were developed by OPC and were directly informed by the science update.

The full guidance and detailed findings can be found here, but some key takeaways include:

  • There is greater certainty and a narrowing range of the amount of sea level rise through 2050, with the range of sea level rise projections expanding through the end of the century and beyond. The pathway associated with the extreme sea level rise scenario (i.e. H++) from Rising Seas 2017 is higher than the best available science now supports.
  • Sea level rise, when combined with extreme storms and higher tides, will result in accelerated cliff and bluff erosion, increased coastal flooding, and flooding from groundwater. 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.
  • A precautionary stepwise process for incorporating sea level rise scenarios into planning and project is needed to phase adaptation actions over time. The most precautionary approach, when feasible, is to evaluate Intermediate, Intermediate-High, and High Scenarios to assess a spectrum of potential impacts, consequences, and responses.

The 2024 guidance is a testament to California’s continued commitment to bring the most credible science to the table to set policy direction that is based on and rooted in best available science. This effort additionally underscores the vital importance and role that the scientific community and their continued progress can play in supporting sound policy guidance. We, at OST, are very proud to have played a role in helping California lead with science in addressing this crucial issue.

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