Real-Time Monitoring of an Active Landslide above U.S. Highway 50, California

During January 1997, several large landslides closed Highway 50 between Placerville and South Lake Tahoe, California. The photograph above shows the catastrophic Mill Creek landslide that closed Highway 50 for 4 weeks. A number of other landslides are currently active in this corridor.

The U.S. Geological Survey, in cooperation with the Eldorado National Forest, has installed monitoring instruments on one currently active landslide that has the potential to affect Highway 50. Data from these instruments are used to detect changes in local conditions including:

• Rainfall
• Groundwater data from pressure sensors
• Movement data from displacement sensors
• Ground vibration from geophones.

Data are collected every 15 minutes and displayed on graphs. In many landslides, infiltration of rainfall or rapid snowmelt increases groundwater pressures. These elevated pressures can, in turn, trigger landslide movement.

For More Information

• Current Highway 50 Landslide status
• Highway 50 Landslide Monitoring Report

Contact Information

• Mark Reid
  mreid [at] usgs [dot] gov

  U.S. Geological Survey
  Landslide Hazards
  345 Middlefield Road MS 910
  Menlo Park, CA 94025

• Rick LaHusen
  rlahusen [at] usgs [dot] gov

  U.S. Geological Survey
  Volcano Hazards
  1300 SE Cardinal Court, Building 10, Suite 100
  Vancouver, WA 98683