L1-Landslides_Significance

L1-Landslides_Significance - The Unstable Earth Landslides...

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Unformatted text preview: The Unstable Earth: Landslides Part 1: SocioSocio-Economic Impact of Landslide Hazards 1972 Po Shan Road Landslide, Hong Kong 1 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 All roads lead to Rome … “And as a rock falls precipitate from some mountain-crest, torn thence by the wind, or washed forth by the swollen rains, or loosened by the stealthy lapse of years; under mighty impulse the destroying cliff crashes in abrupt descent and bounds over earth earth, involving in its train forests and herds and men…” Virgil (20 BCE), “The Aeneid” 2 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 1 Introduction … the 1999 Vargas landslides in Venezuela claimed more than 30,000 lives. Throughout the world, valleys in mountainous regions have experienced accelerated economic development in response t general population to l l ti growth and associated demands for increased mining, forestry and agricultural activities. … landslides in the Alps resulted in 37 deaths and $600 million in damage during 2000. 3 of 34 This growth has required the expansion of communities and civil infrastructure into “marginal” land. marginal land Our short history of development in these new regions, however, makes the evaluation of potential landslide hazards and appropriate countermeasures very difficult. Landslides: Erik Eberhardt EOSC 114 – 2009/10 Landslide Learning Goals I By the end of this lecture, you will be able to: 1) Explain how the socio-economic impact of landslides depends on th t l d lid d d the type and characteristics d h t i ti of the landslide hazard. 2) Define the chief components of landslide risk. 3) Distinguish the different modes of failure (falls, slides and flows) and how they are influenced by y y geology. 4 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 2 Social Impact of Landslides Huascaran, Peru (1970) – 25,000 dead 5 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 Social Impact of Landslides Vargas, Venezuela (1999) – 30,000 dead 6 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 3 Social Impact of Landslides 1911 Usoi Rock Avalanche, Tajikistan (volume = 2.2 km3, no fatalities) 2002 Lutzenberg Landslide, Switzerland (volume = 4000 m3, 3 fatalities) 7 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 Social Impact of Landslides Rockfalls 8 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 4 Social Impact of Landslides Rockfalls 9 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 SocioSocio-Economic Impact of Landslides Slow Moving Landslides 10 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 5 Landslides Mass movement: refers to the downslope motion of soil and/or rock materials under the influence of gravity. f Landslide: is a general term used to refer to all mass movements. Kansu (China) Madison (Montana) Vaiont (Italy) Aberfan (Wales) Huascaran (Peru) Nevado del Ruiz (Colombia) Casitas (Nicaragua) Venezuela 11 of 34 1920 1959 1963 1966 1970 1985 1998 1999 Loess flow Rockslide Rockslide Debris-slide Complex Debris flow Debris flow Complex 200,000 killed >100 killed 2,600 killed 144 killed 25,000 killed 23,000 killed >2,000 killed >30,000 killed Landslides: Erik Eberhardt Major l M j slopeinstability related catastrophes of the 20th century EOSC 114 – 2009/10 Influence of Geology Geological Planes of Weakness - e.g. foliation, jointing, faults rockfall 12 of 34 Landslides: Erik Eberhardt sliding EOSC 114 – 2009/10 6 Rock Falls Falls occur on steep slopes with loose rock that periodically detach from a surface on which little or no shear/sliding takes place. The material then descends mainly through l h h the air by falling, bouncing or rolling. 13 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 Slides Slides involve large volumes of rock or soil moving as an initially coherent mass on a sliding surface. These may occur as: Rotational slides: where soil or weak rock collapse along a curved rupture surface that forms due to the shear forces in the slope exceeding the shear strength of the soils/rocks. Translational slides: where blocks of strong rock move along a weak fracture in the rock (e.g. jointing, bedding planes, etc.), or weak soil moves on top of a hard bedrock interface. 14 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 7 Rotational or Translational? 15 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 Flows Flows: occur when there is a large volume of water present in a mixture of soil and debris. Rather than moving downslope as a coherent mass, the material flows downhill as a chaotic mixture. 16 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 8 Debris Flows – Sea to Sky Debris flows are common in our coastal mountains because heavy rains fall on y steep slopes covered by loose sediments. Highway 99 (Sea-to-Sky) has a long history of destructive debris flows. 17 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 Debris Flows – Sea to Sky Since 1921 there have been over 50 deaths and millions of dollars in damage to private property and public infrastructure, related to debris flows in the area between Horseshoe Bay and Squamish. Aerial view (looking north) of the 1983 debris flow in Lion's bay that killed two people. Note damage to roads, the railway and to buildings. M-Creek; nine people were killed after their cars plunged into the creek during the night after a debris flow had destroyed the bridge. 18 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 9 Definitions (Forming Names) Type of Material Type of Movement Rock Fall Debris Slide Rock Fall Flow Earth Slope Classification Name Rock Slide Debris Slide Earth Slide 19 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 Learning from the Past Turtle Mountain X-Section Frank Slide, Alberta (1903) – 70 dead Slide … Turtle Mountain was known to the First Nations people as the “Mountain that Walks”. 20 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 10 Learning from the Past 21 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 “Not” Learning from the Past La Conchita Landslide, CA (1995) – no fatalities Reactivation of La Conchita Landslide (2005) – 10 fatalities 22 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 11 Learning from the Past: Socio-Economic Impact Socio- Compared to the European Alps, we have a much shorter historical record and lower population density in our mountains. 23 of 34 Vulnerability increases by: • increasing population density • use of marginal land • rapid land-use change Landslides: Erik Eberhardt EOSC 114 – 2009/10 SocioSocio-Economic Impact: Vancouver Impact: Riverside Drive (2005) – 1 fatality 24 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 12 SocioSocio-Economic Impact: Hong Kong Impact: Po Shan Road, Hong Kong (1972) - 67 fatalities Sau Mau Ping, Hong Kong (1972) - 79 fatalities 25 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 SocioSocio-Economic Impact increasing population density Canada: ~3 lives/yr USA: ~30 lives/yr Japan: ~200 lives/yr Developing countries??! Globally, Globally landslide fatalities are reported to be about 7500/year, but are typically underestimated as many fatalities are associated with the landslide trigger (earthquakes, floods, etc.) and not the landslide itself. 26 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 13 SocioSocio-Economic Impact Porteau Cove Rockslide (2008) – highway closed 1 week 27 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 SocioSocio-Economic Impact Duweiqa Rockslide, Egypt (2008) – 500+ fatalities 28 of 34 Landslides: Erik Eberhardt EOSC 114 – 2009/10 14 ...
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