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19 02 massive landslides 1
- 1. Things are going downhill fast: understanding massive landslides Dave Petley Vice-President, Research and Innovation Twitter: @davepetley Blog: https://blogs.agu.org/landslideblog/
- 2. What is a landslide? • A landslide is the process that occurs when a slope collapses • The dominant material is rock, debris or soil 11/03/2019 © The University of Sheffield
- 3. Landslides have a huge range of scales 11/03/2019 © The University of Sheffield
- 4. Three massive landslides: 1. Aberfan, Wales 1966 11/03/2019 © The University of Sheffield
- 5. Three massive landslides: 2. Anak Krakatau, 2018
- 6. Three massive landslides: 3. Brumadinho, Brazil 2019
- 7. Five key slope processes: 1. the role of water • Friction is a key control • Water creates buoyancy, reducing friction • As slopes become saturated they are more likely to slide
- 8. 2: As earth materials deform they can go from solid to fluid
- 9. Alaska 2018 11/03/2019 © The University of Sheffield New Zealand 2011
- 10. 3: Rocks with defects are much weaker than those without
- 11. 4: Earthquakes in mountains generate many slope failures
- 12. 5: We don’t understand why the biggest landslides travel far and fast
- 13. 11/03/2019 © The University of Sheffield GNS Science interpretation of the Mount Haast (Mount Dixon) rockslide
- 14. 11/03/2019 © The University of Sheffield Landslides are often a part of a highly complex chain of events Palu, Sulawesi earthquake, 2018
- 15. The 2008 Wenchuan earthquake in China: a true landslide crisis Final toll: 69,181 killed and 18,498 missing
- 16. 2008 Wenchuan (Sichuan) earthquake, China 14:28 12 May 2008; Mw = 7.9; Depth = 19 km
- 21. Landslides: before and after Landsat 5 18/09/2007 SPOT5 13/10/2008
- 25. Case study – Beichuan Town Beichuan town 2007
- 27. Beichuan Middle School landslide Location of school 700 people killed
- 28. Old Town Landslide (10 mins after main shock)
- 29. Hattian landslide, Pakistan Kashmir earthquake 2005
- 30. 11/03/2019 © The University of Sheffield
- 33. The 2010 Attabad crisis in Northern Pakistan
- 35. Slope identified as unstable in 2003
- 36. Collapse event: 4th January 2010
- 38. 1. Progressive failure over >7 years, scar height = 1175 m 2. Catastrophic failure event in Jan 2010 with no trigger 3. Emplacement of rockslide onto lake sediments triggered secondary high velocity mudflow event Cross valley runout = 1300 m Deposit height = 120 to 200 m
- 42. Wenchuan Earthquake barrier lake risk table Yang et al 2010
- 43. Management of the hazard • Initial management response was the construction of a spillway. • Original intention: 30 metres deep • Actual depth at time of overtopping: 15 metres • Final spillway was very narrow and unlined
- 44. ∂ Water level rise -1 0 1 2 3 4 5 6 7 8 0 20 40 60 80 100 120 Rateoffilling(metresperday) Waterdepth(metres) Date Water depth (m) Height of lowest point of completed spillway Filling rate
- 45. Evacuations • After the landslide, Focus installed sirens in 15 villages • People in most hazardous areas relocated into camps • Boat service established on lake, but enormous hardship upstream • One month before overtopping NDMA evacuated 15,000 people downstream of barrier
- 46. Seepage
- 51. 11/03/2019 © The University of Sheffield 0 20000 40000 60000 80000 100000 120000 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Cumulativenumberoffatalities Date 111,000 fatalities since Sept 2002
- 52. 11/03/2019 © The University of Sheffield
- 53. Dave Petley Vice-President, Research and Innovation Twitter: @davepetley Blog: Search “landslide blog” Email: d.n.petley@sheffield.ac.uk