ASCE Orange County Geo-Institute Technical Presentation - Emergency Stabilization of a Coastal Landslide

Mahdi Sharghi, Ph.D., P.E. and Jim Starick, P.E. of HDR will present a case history of a landslide in a Southern California coastal zone, emphasizing the integration of advanced monitoring technology in an emergency response project. The landslide, driven by coastal erosion and other environmental factors, posed significant risks to public safety, private property, public transit, freight operations, and one of the military’s strategic corridors.

Geotechnical analyses confirmed that erosion of sand at the landslide toe reduced its natural buttressing capacity, ultimately triggering the failure. Emergency mitigation measures involved placing approximately 22,000 metric tons of riprap in three phases to re-establish toe support.

The longer-term stabilization design incorporated two rows of anchored grade beams extending across the full slide area. Execution required extensive coordination and collaboration among multiple stakeholders. Remarkably, the project was completed within six months—during one of the wettest periods Southern California has experienced in recent…