USGS maps, measures huge landslide on California's Big Sur coast

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USGS scientists analyzing before-and-after air photos have calculated the size of the May 20 landslide on California’s Big Sur coast, about 140 miles south of San Francisco. 

Cutout view of Mud Creek landslide area

Credit: USGS. Public domain.

USGS scientists analyzing before-and-after air photos have calculated the size of the May 20 landslide on California’s Big Sur coast, about 140 miles south of San Francisco. They are sharing their information with California Department of Transportation (Caltrans) engineers assessing the slide. Preliminary calculations indicate that the landslide moved approximately 2 million cubic meters of material, enough to fill 800 Olympic-sized swimming pools. It buried State Highway 1 more than 20 meters (65 feet) deep and added more than 50,000 square meters (about 13 acres) of new land to the coast. USGS scientists shot air photos of the Big Sur coast in March and May 2017. Using “structure-from-motion” software, they transformed these and earlier photos into 3D maps that allow them to precisely measure areas and changes in ground elevation. They plan to keep monitoring the slide area via weekly airplane flights and, starting in June, drone flights.

For additional information and images, please visit the USGS Remote Sensing Coastal Change website.

A series of images takes a tour of the area of a large catastrophic landslide and shows the unstable slope before the event.

Imagery shows topographic point clouds generated by the USGS from photos:

  1. September 11, 2015 courtesy of California Coastal Records Project,
  2. March 8, 2017 (USGS photo),
  3. May 19, 2017 (USGS photo), and
  4. May 27, 2017 (USGS photo) 7 days following the catastrophic Highway 1 landslide.
  5. Last image shows the change in topography from the 2015 photo til the May 27 photo, with deep red colors showing greater loss of elevation (up to 40 meters lost) and deep purples showing the greater increase in elevation (up to 40 meters gained).

Provisional Data Subject to Revision. Credit: Andy Ritchie, USGS Pacific Coastal and Marine Science Center. Public domain.

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