Coastal erosion and sea level rise have become common issues along the coast of Southern California not only from an environmental standpoint, but also from a geotechnical standpoint.
This paper presents a case study of coastal erosion that resulted in the partial reactivation and movement of an ancient landslide along the Orange County coastline. The reactivated landslide resulted in the damage of several homes within the Cyprus Shore Community Association and the shutdown of critical railroad infrastructure for nearly 8 months. GMU – Engineers & Geologists (GMU) performed subsurface investigations, landslide movement monitoring, and slope stability analyses to determine the likely cause of the partial ancient landslide reactivation. Based on our investigation, monitoring, and analyses, we derived a geologic model that indicated beach sand erosion was a primary factor in the reactivation. Our geologic model was utilized in the stabilization measures implemented by Orange County Transit Authority (OCTA)/Metrolink.