A comprehensive coastal vulnerability assessment warns that Malibu's critical Highway 1 corridor, thousands of homes, and the city's narrow beaches face significant threats from rising sea levels, with potential impacts becoming severe as water levels rise 2.5 to 6.6 feet in coming decades.
The assessment, presented to the Malibu City Council on Monday, identifies four major areas of vulnerability along the city's 21-mile coastline: residential and commercial development, septic systems in low-lying areas, the Pacific Coast Highway, and the city's already narrow beaches.
Environmental Science Associates, the consulting firm that conducted the study, used U.S. Geological Survey modeling to project coastal hazards including tidal inundation, shoreline erosion, storm flooding and wave runup under current conditions and future sea level rise scenarios.
"Development, including residential and commercial development along the coast, are exposed to shoreline and bluff erosion as well as tidal inundation and coastal storm flooding and wave runup," said James Jackson, a civil engineer and hydrologist with Environmental Science Associates.
The study takes on new urgency following the January Palisades Fire, which destroyed numerous coastal homes previously identified as vulnerable in the assessment. Council members raised concerns about how the disaster affects both immediate rebuilding efforts and long-term coastal planning.
"A lot of the homes that were identified as vulnerable in the study are obviously not there, but the results of the vulnerability assessment are still valid," Jackson told the council.
City Council member Steve Uhring expressed particular concern about Highway 1's vulnerability, warning that the critical transportation corridor could be lost during a major storm. "If we get a big storm, PCH is gone," Uhring said, urging staff to share risk information with the California Department of Transportation.
The assessment reveals that Highway 1 faces exposure to both shoreline erosion and coastal storm flooding. Jackson noted that the modeling assumes coastal hazards without considering protective infrastructure, providing a worst-case scenario for planning purposes.
Council member Bruce Silverstein highlighted a potential conflict between rebuilding efforts and future coastal regulations. He noted that structures being rebuilt after the fire likely would not meet stricter standards that might be applied to new development based on the vulnerability findings.
"Nothing that the council is going to do is going to require anyone with a house on the beach to take their house down or make a material change to it because of these vulnerabilities," Silverstein said. "Going forward, those same reasons and rules would dictate with respect to undeveloped properties that it's going to be much more difficult."
The study examined sea level rise projections that have shifted timing based on updated state guidance. The 2.5-foot scenario now projects to occur between 2070 and 2075 under current planning approaches, representing a shift further into the future from earlier projections.
Septic systems present another significant concern, particularly in low-lying areas where existing high groundwater conditions will worsen with additional sea level rise. The city's beaches, already narrow under current conditions, face additional pressure that could result in widespread beach loss along the coastline.
The project, which began in 2019 and was delayed by COVID-19, will move into its adaptation planning phase in 2026. Environmental Science Associates will compile potential mitigation measures ranging from nature-based solutions like dune restoration to traditional engineering approaches including coastal armoring and structural elevation.
Jackson said the next phase will identify "a range of possible adaptation measures that may be suitable along the city's shoreline and to identify near term measures that should be explored further."
The final report, expected in 2026, will include coastal hazard maps for each sea level rise scenario and could inform future amendments to the city's Local Coastal Program. Jackson emphasized that the current study is intended as an educational foundation rather than a comprehensive adaptation plan.
Mayor Marianne Riggins expressed interest in beginning mitigation efforts before the study's completion, noting that other coastal communities are already implementing protective measures. "There's a half a dozen cities up and down the coast right now that are doing various things along their coastline," she said.
The assessment aligns with California Coastal Commission sea level rise policy guidance and will help inform the city's long-term planning and resilience efforts. Public engagement included workshops, surveys, and an online mapping tool where residents can access vulnerability data.
Project information and resources are available at MalibuCity.org/Coastal.