Preliminary Results of Subsurface Exploration and Monitoring at the Johnson Creek Landslide, Lincoln County, Oregon

The Johnson Creek landslide is a translational, primarily bedrock landslide located along the Oregon coast about 5 km north of Newport. The landslide has damaged U.S. Highway 101 many times since construction of the highway and at least two geological and geotechnical investigations of the landslide have been performed by Oregon State agencies. In cooperation with the Oregon Department of Geology and Mineral Industries and the Oregon Department of Transportation, the U.S. Geological Survey upgraded landslide monitoring systems and installed additional monitoring devices at the landslide beginning in 2004. Monitoring devices at the landslide measured landslide displacement, rainfall, air temperature, shallow soil-water content, and ground-water temperature and pressure. The devices were connected to automatic dataloggers and read at one-hour and, more recently, 15-minute intervals. Monitoring results were periodically downloaded from the dataloggers using cellular telemetry. The purposes of this report are to describe and present preliminary monitoring data from November 19, 2004, to March 31, 2007.