In the winter of 2015-16, waves chewed away so much sand from Pacifica’s coastal bluffs that apartment buildings teetered over the edge, forcing emergency evacuations. Farther south, Malibu homeowners watched storm surge push seawater into living rooms. Both disasters unfolded during what scientists ranked as one of the strongest El Niño events in roughly 145 years. Now, with NOAA’s Climate Prediction Center flagging rising odds of another powerful El Niño forming by late 2026, researchers and emergency planners are asking an uncomfortable question: What happens when a comparable storm cycle hits a coastline where sea levels are already higher than they were a decade ago?
What the measurements show
Two past El Niño episodes form the backbone of California’s coastal risk evidence. During the 2015-16 event, the U.S. Geological Survey deployed lidar flights, GPS surveys, wave instruments, and sand-height sensors along the state’s 1,100-mile shoreline. The resulting USGS analysis documented record shoreline retreat across large stretches of central and northern California, providing the most detailed erosion dataset ever assembled for a single West Coast storm season.
A separate peer-reviewed study, archived through a NOAA repository, used airborne lidar to examine roughly 300 kilometers of Southern California coastline during the same cycle. That research revealed a more complicated picture: some beach segments lost dramatic amounts of sand while neighboring stretches actually gained it. The pattern depended on local geology, the orientation of the shoreline, and whether nearby coastal structures redirected wave energy. The finding matters because it shows that even under the same broad climate signal, impacts can vary sharply over just a few kilometers.
The 1997-98 El Niño offers its own cautionary record. USGS tide gauge data and NOAA observations showed abnormally elevated sea levels in the San Francisco Bay area, which amplified storm-driven flooding and caused costly damage to waterfront infrastructure. That same winter, USGS geospatial surveys documented clusters of storm-triggered landslides across Northern California hillsides, where weeks of heavy rain saturated slopes and sent debris into neighborhoods and across highways.
NOAA’s Pacific Marine Environmental Laboratory has compiled monthly sea-level anomalies from both the 1997-98 and 1982-83 El Niño events, illustrating a core physical mechanism that drives much of the danger. During a strong El Niño, warmer ocean water and shifting atmospheric pressure raise the seasonal baseline sea level along the West Coast. Every high tide and every storm surge then starts from that elevated platform. A tide that would normally lap harmlessly at a seawall can instead overtop it, and a moderate storm can push water into areas that flooded only during extreme events in the past.
State agencies treat this threat as concrete, not theoretical. The California Coastal Commission’s public guidance on extreme weather and El Niño states directly that El Niño raises coastal water levels and intensifies storm impacts, citing the 2015-16 cycle as the event that caused record erosion along many California beaches. The California Department of Water Resources, meanwhile, has emphasized flood readiness through its annual Flood Preparedness Week, stressing coordination around atmospheric river science and community-level response planning.
Why higher baselines matter now
One factor that separates any future super El Niño from its predecessors is the steady climb in background sea level. NOAA tide gauges along the California coast have recorded a long-term rise that means today’s “zero line” for tides and storm surge sits higher than it did during either the 1997-98 or 2015-16 events. The exact increment varies by location because of differences in tectonic uplift, subsidence, and ocean circulation, but the direction is consistent: every centimeter of baseline rise effectively lowers the threshold at which a storm tide causes flooding or overtops coastal defenses. No single agency has yet published a combined model that layers El Niño sea-level anomalies on top of the updated 2026 baseline to produce region-specific flood projections, so the precise numerical gap between past and present baselines remains an area where more granular analysis is needed.
What remains uncertain
The central unknown is whether the current ENSO cycle will actually produce a strong or “super” El Niño. NOAA’s Climate Prediction Center publishes regularly updated probability outlooks for El Niño, neutral, and La Niña conditions across overlapping three-month windows. As of its most recent monthly outlook, the center’s probability estimates have drawn increased attention to the possibility of a significant event forming by late 2026, though those figures describe likelihood ranges, not guarantees. Even when the odds tilt toward El Niño, the eventual peak strength, duration, and geographic pattern of ocean warming can diverge from early signals, and those details determine how storms track into California.
The tools used to measure El Niño strength are themselves evolving. NOAA’s drought information system noted in early 2026 that updated ENSO indices are being developed for better decision support, acknowledging that older metrics sometimes overstated or understated event intensity. Different indices can characterize the same ocean conditions slightly differently, which means the labels “strong” and “super” should be read alongside more granular forecasts of wave height, storm timing, and local sea level rather than treated as standalone predictors.
No publicly available primary source currently projects specific 2026 landslide risks tied to a super El Niño scenario. The USGS landslide maps from 1997-98 document what happened during that winter but do not model forward probabilities for the next strong cycle. Vegetation, wildfire burn scars, and development footprints have all shifted since the late 1990s, so assuming a repeat of past slide locations would be misleading. Similarly, no primary dataset yet combines El Niño sea-level anomalies with long-term sea-level rise to produce region-specific flood projections for 2026. Planners are working from historical analogs, not tailored forward models that account for today’s higher baseline seas and denser coastal development.
Quantitative cost estimates for a future super El Niño are also absent from agency publications. Past damage figures from 1997-98 and 2015-16 appear in news accounts and secondary reports, but no state or federal agency has published an updated model calibrated to current property values, population density, and infrastructure conditions along the California coast.
Voices from the field
The California Coastal Commission has stated in its public El Niño guidance that the combination of elevated sea levels and intensified storm activity “increases storm impacts including coastal flooding and erosion.” USGS researchers who led the 2015-16 beach monitoring effort described their lidar-based erosion measurements as evidence of “record erosion” along many California beaches, language the Coastal Commission subsequently cited in its own advisories. The Department of Water Resources, in materials released during its annual Flood Preparedness Week, has urged residents in flood-prone areas to “know your risk” and to review local hazard maps before storm season begins.
For residents seeking specific guidance, the Coastal Commission’s El Niño preparedness page links to county-level resources and erosion advisories. The Department of Water Resources maintains a flood preparedness portal with evacuation route information and sandbag distribution sites organized by county. Local county offices of emergency services, reachable through California’s Governor’s Office of Emergency Services website, publish community-specific hazard maps and alert sign-up tools. Residents in hillside areas affected by recent wildfires should consult their county’s post-fire debris flow warnings, which are typically updated by the National Weather Service before each significant storm.
How to read the evidence
The most reliable evidence comes from direct physical measurements. USGS lidar surveys, GPS topographic data, and NOAA tide gauge records are repeatable observations that capture how beaches, bluffs, and water levels actually responded during past El Niño winters. When those measurements show record shoreline retreat or unusually high sea levels, they establish a firm baseline for assessing what similar conditions could produce today, particularly given that background sea level along the California coast has continued to rise since the 1990s.
Peer-reviewed studies that analyze these measurements add depth. The Southern California lidar work, for example, does more than map sand loss; it compares spatial erosion patterns between 1997-98 and 2015-16, revealing how local geology and coastal structures can amplify or buffer El Niño impacts from one stretch of shoreline to the next. That level of detail is critical for communities like Imperial Beach, where low elevation and limited natural barriers make even modest sea-level increases dangerous, or Pacifica, where bluff-top homes sit on geology that has already proven unstable under heavy wave attack.
Agency guidance documents, such as the Coastal Commission’s El Niño advisories and the Department of Water Resources’ flood preparedness materials, translate technical findings into practical recommendations: where to reinforce infrastructure, how to prepare for king tides combined with heavy surf, and which communities may need evacuation support. When those documents cite specific past events as analogs, they are signaling that the physical processes behind those impacts have not changed.
The gaps in forward-looking models and cost estimates should not be mistaken for evidence that the risk is low. They reflect the complexity of slope stability, sediment transport, and economic modeling, not a conclusion that hillsides will hold or that flooding will stay within historical bounds. For the millions of Californians who live in coastal and flood-prone areas, the prudent approach is straightforward: where decades of measurements and two major El Niño events point to a clear hazard, preparation should not wait for the next generation of models to confirm what the data already suggest.
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*This article was researched with the help of AI, with human editors creating the final content.
