McWay Landslide - Big Sur, California

Manipulated and natural landslides are common disturbances along the slide prone coast of California. They can affect marine intertidal and subtidal communities by direct burial, scouring by coarse sediments, and deposition of fine sediments. They also may increase turbidity in marine waters. The McWay landslide, on the Big Sur coast, caused by heavy winter rains in 1992-93, closed Highway One for almost two years. It is the largest landslide manipulated by CalTrans in recent years. In order to reopen the highway, CalTrans removed over three million cubic meters of sediment and debris. Much of the sediment was deposited onto the face of the slide on the west side of Highway One where it continues to erode and slump into the ocean. Since 1986, the Benthic Lab group has investigated the movement of this sediment into the ocean and its impacts on nearshore marine communities. Surveys of biological and physical conditions in the slide affected areas, (terrestrial, intertidal and subtidal) are conducted annually and will continue through 1998, providing an important long-term data set. Biological communities are assessed by photographic and video techniques. The seafloor affected by the slide has been mapped as to sediment type and distribution through the use of sidescan sonar and grain size analyses. Profiles track topographic changes in beach and intertidal areas. Additionally, baseline biological data has been collected to describe other slide-prone sites in the region. These data are essential in developing environmentally sound and defensible highway construction and maintenance strategies. View Full Report

Contact the Web Master: sperry@mlml.calstate.edu