California: Sea Level Rise Guidance 2024

There has long been interest in Australia of practices adopted in California in coastal management. Various federal inquires going back to 1979 were made aware of what was happening in that US state, but we never received strong federal guidance similar to that in the USA. In 1981, Professor Trevor Langford-Smith, then Chair of the NSW Coastal Council, visited California and on return wrote a report entitled “The Californian Experiment in Coastal Management: A Model for Australia?” (Coastal Studies Unit, University of Sydney, Tech. Report 81/2). By this stage NSW had already picked up aspects of the “experiment” with its Coastal Protection Act, 1979.

Deterioration of the coastal zone in California led to its citizens rebelling against an intransigent legislature using a public initiative via a petition signed by a fixed proportion of voters (325,000 in 1972). If successful it is then balloted at a state election. Proposition 20 was successful and provided for a “Californian Coastal Zone Conservation Commission”, the forerunner of the now California Coastal Commission (CCC) (http://www.coastal.ca.gov/whoweare.html). The proposition also facilitated the passage of the California Coastal Act, 1976, which aimed “to protect, conserve, restore, and enhance the environment of the California coastline”.

CCC is a state agency with quasi-judicial control of land and public access along the 1800km of coast. It is able to regulate land use within a defined coastal zone extending inland for varying distances from a few blocks in urban areas (c.900m) to up to 8km. This use of a mapped zone was replicated in NSW where initially the coastal zone was defined by 1:50,000 map sheets before being reduced to a narrow strip now set out as management areas (see NSW Resilience and Hazards SEPP, Chapter 2). CCC has authority to control construction as well as fire and erosion abatement structures and can issue fines for unapproved construction. Equivalent entities in Australia, where they exist, do not exercise such wide-ranging regulatory controls. Given its powers over private and public assets CCC receives constant criticism. Most recently this has come from those seeking to overcome housing shortages by exempting housing developments from lengthy public hearings and environmental legal challenges. This would limit the role of the CCC in the housing permitting process and thus be in conflict with the CCC role in assessing risk and adverse effects associated with sea level rise.

I have long admired the operation of the CCC and how California state law fits nicely with federal law (which of course we don’t have!). Through the so-called “consistency provision”, the CCC is able to review federal projects and activities. In 1998 I was privileged to spend time in San Francisco at the CCC where I met its legendary Executive Director, Peter M. Douglas. To learn of its successes, its legal challenges, and its funding and political problems was quite illuminating. One matter for discussion was climate change. In 2014, the CCC was directly involved in developing policy guidance on sea-level rise using information emerging from IPCC reports and also federal guidance (e.g. National Research Council 2012 projections for SLR). This role is now the responsibility of California’s Ocean Protection Council (OPC).

The OPC is a cabinet-level body established under the California Ocean Protection Act (COPA) (https://www.opc.ca.gov). It has a role in coordinating activities of state agencies that are related to the ocean and coasts including establishing policies that coordinate the collection and sharing of scientific data. OPC is involved in climate change adaptation aiming to minimize adverse impacts on coastal and ocean ecosystems. Unlike the CCC it is not a regulatory body. On 5 June the OPC officially adopted and released guidance to help California prepare for sea level rise. This is a revision of the 2018 previous guidance working with the California Ocean Science Trust (OST) and a Scientific Task Force. The national report entitled “Global and Regional Sea Level Rise Scenarios for the United States” in 2022 presented an opportunity for OPC to proceed with this 2024 update. It aimed to align the state’s approach with national coastal adaptation efforts, and also to present the science alongside policy recommendations developed by the OPC.

The 2024 guidance report highlights: (1) the greater certainty with the amount of SLR through to 2050 with the range expanding to 2100 and beyond; (2) combining SLR with extreme storms and higher tides, accelerated erosion and flooding (including groundwater); and (3) a precautionary stepwise approach for incorporating SLR scenarios into planning to “phase adaptation actions over time”. All this is not news to Australia. But what is different is the way this state is applying sea level scenarios thereby adapting the scientific framework used in the federal report together with information derived from the sets of probabilistic projections in IPCC AR6.

The essence of the 2024 guidance is contained in five sea level projections which span the plausible range of future sea levels (incorporating local variations due to vertical land motion). Users are encouraged to consider SLR scenarios without first selecting a single emissions future. The scenarios are: LOW (0.3m by 2100); INTERMEDIATE-LOW (0.5m by 2100); INTERMEDIATE (1.0m by 2100); INTERMEDIATE-HIGH (1.5m by 2100); and HIGH (2.0m by 2100). The Intermediate scenario includes low confidence processes such as rapid ice melt and is said to provide “a reasonable upper bound for the most likely range of sea level rise by 2100”.

OPC is recommending agencies and city authorities adopt a “stepwise process” to inform SLR planning and decision making. STEP 1: identify the nearest tidal gauge so that localized effects are incorporated in scenarios. STEP 2: evaluate planning and/project time horizons which may require earlier time horizons for interim adaptation steps. STEP 3: choose multiple sea level scenarios for vulnerability assessment of people, natural resources and infrastructure including analysis of 100-year storm conditions related to wave processes and storm surges. STEP 4: conduct vulnerability assessment by creating exposure maps of SLR-induced inundation and flooding, coastal erosion and groundwater rise; this step includes community engagement to determine adaptive capacity to projected impacts. STEP 5: explore adaptation options and feasibility with affected stakeholders and regulatory bodies on feasible adaptation options (presumably this includes the CCC). STEP 6: select phased adaptation approach and/or implement project.

Those of us who spent years involved in NCCARF projects will recognize much of the intent, approach and structure in the 2024 OPC SLR guidance update. It is expressed with a level of confidence that has resonated with entities such as the California Coastal Cities Group and the State Association of Counties. They have been urging the agency to better recognize local planning and adaptation efforts as integral to addressing issues associated with SLR. Central to their concerns have been negative effects of utilizing extreme sea level rise projections leading to an erosion of public trust. The stepwise approach using scenarios allows more flexibility for local governments to better understand possible impacts and plan, design and implement appropriate responses. It will be interesting to see how the regulatory agency, the CCC, works with cities and counties as they roll out the steps at a specific project or planning level.

Bruce Thom

Words by Prof Bruce Thom. Please respect the author’s thoughts and reference appropriately: (c) ACS, 2024. For correspondence about this blog post please email admin@australiancoastalsociety.org.au

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