California Landslides

Types of Landslides: Image

• Falls
• Topples
• Slides
• Lateral Spreads
• Flows

Yosemite National Park: Image

• Happy Isles Rock Fall, 1996
• 70,000 cubic yards fell 2,000 feet
• Damages caused by winding effect
• Dust spread for miles around the impact site

La Conchita Landslides: Images

• History
  • 1930s Survey: Lowest priced parcels built entirely on mud flow debris.
  • As far back as the 1800's there have been recorded histories of landslides
  • 1865 merchant account
  • 1899 Southern Pacific Railroad relocates tracks
• 1995
  • Claimed $24 million in damages
  • 1.7 million cubic yards of earth slid more than 600 feet
  • 3 confirmed fatalities
  • Dramatic loss in property value
• 2005
• Re-activation of landslide of 1995
• Much more viscous flow
• 13 homes destroyed, 23 others deemed unlivable
• 10 confirmed fatalities

San Francisco Bay Area

• 1997-98 El Nino Winter caused 1,800 recorded landslide events
• President Clinton declared it an emergency deserving of FEMA.
• Some areas in the 10 county region experienced 240% of their annual rainfall
• Slides measured from 33 cubic yards to 17 million cubic yards
• 6,500 homes in disrepair, 1,000 businesses damaged and 33 people died

Mitigation Efforts

• Avoid building in seriously prone areas
• Build culvert streams to drain groundwater
• Build safety walls with anchors deep in slopes
• Place slide sensors in prone areas
• EDUCATE THE PUBLIC !!!