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Case Studies

Case Studies. 1963 Vaiont Disaster. Case Studies. Ancient slide and recent small slide gave reason to worry. Case Studies. Geology of the area led to problems . Rainfall and water level led to earth movement. Slumgullion. Translational Slide: goes along existing weakness

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Case Studies

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  1. Case Studies 1963 Vaiont Disaster

  2. Case Studies Ancient slide and recent small slide gave reason to worry

  3. Case Studies Geology of the area led to problems

  4. Rainfall and water level led to earth movement

  5. Slumgullion

  6. Translational Slide: goes along existing weakness This one cost taxpayers $400 million

  7. Thistle, Utah: 1983 Snowmelt Town was flooded Lake was drained slowly Railroad/Highway moved Slide is still moving

  8. Landslides Create Dams and Lakes Failure is inevitable: • Time before failure and size of flood depends on • Size, height and geometry of dam • Material making up dam • Rate of stream flow, how fast lake rises • Use of engineering controls (artificial breaches, spillways or tunnels) • Dams from mudflows, debris flows and earth flows are noncohesive and erode quickly

  9. 2008 Earthquakein China

  10. Failure of Landslide Dams • Most landslide dams fail when water overflows and erodes spillway that drains lake • If dam-failure flood incorporates significant sediment, can turn into debris flow – much more dangerous • Useful dams can be constructed on top of rock dams • China solution: Use explosives to remove the dams

  11. Landslides are a major problem • Not covered by insurance • In U.S., $2 billion and 25-50 deaths/year • Globally, $20 billion, 7500 deaths/year • Disasters increase with population

  12. Mitigation of Damages from Landslides Colorado Springs

  13. Cities Can Map Ancient Slides Colorado Springs 1995: Rainfall and Landslides abundant Clay-rich rock and steep slopes of the Rockies 1999 major slides and flooding City purchased landslide-affected properties ($4.5M) GIS maps of old slides and potential slides Will this be used wisely?

  14. Oakland, CA

  15. Oakland, CA

  16. Oakland, CA

  17. USGS Landslide Hazard Program Research the causes of landslides Suggest mitigation strategies

  18. Wildfires increase susceptibility

  19. San Diego: 2003 and 2007 • 2003 Fires led to 16 deaths from landslides • $10sM in damage • Moderate rainfall on burned areas • Runoff increases, infiltration decreases • San Diego: 2” rain in 3 hrs is 10 year storm

  20. Fire and Rain Lead to Slides Variables include: • 30% slopes or steeper are vulnerable • % of area burned • Average storm intensity • Clay volume in soil • How much water can be absorbed by soil

  21. Videos

  22. Chemical Weathering-dissolving rocks

  23. Chemical Weathering-dissolving rocks

  24. Carbonic acid forms when CO2 and H2O molecules combine. Carbonic acid ionizes to form hydrogen and bicarbonate ions. Bicarbonate ions react with feldspar. Feldspar KAlSi3O8 + Kaolinite clay Al2Si2O5(OH)4

  25. EROSION BY GROUNDWATER

  26. Artesia: 7/19/08

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