Profile Dynamics and Particle Tracer Mobility of a Cobble Berm Constructed on the Oregon Coast

In response to the erosion of Cape Lookout State Park on the Oregon coast, a cobble berm (dynamic revetment) was constructed for shore protection, designed to be similar to a natural cobble beach. For added protection it is backed by an artificial dune reinforced with a core of sand-filled geotextile bags. We have monitored these structures since 2001, including periodic surveys and measurements of cobble mobility through particle tagging. The surveys have demonstrated profile responses to storms that are the same as found for natural cobble beaches, while the particle tagging has documented a high degree of cobble mobility, including a significant net longshore transport. To date the structures have survived five winters, including several major storms that have resulted in periodic overtopping, providing the desired level of protection to the park. However, due to the loss of cobbles from the cobble berm, its long-term stability is uncertain.