The study used newly developed analysis techniques to track shoreline positions measured from satellites across numerous beach segments and littoral cells—the coastal compartments that govern how sand moves. While some areas experienced measurable beach expansion, others remained stagnant or even eroded, revealing a high degree of variability in shoreline change across the region.

Southern California’s beaches rely on a sediment supply chain that’s fed by rivers, bluffs, and engineered inputs. But dams, urban development, and coastal armoring have long disrupted that flow, leaving many natural beaches starved of sand. At the same time, sediment accumulation behind structures like jetties and breakwaters, as well as localized beach nourishment projects, are artificially inflating certain shorelines.

The study’s results offer new potential for smarter coastal sediment management, by highlighting where interventions have worked and where sand redistribution could better protect vulnerable areas. As sea-level rise accelerates and erosion risks grow, such insights are vital to keeping California’s beaches—and the communities behind them—intact.