Landslides. FALLS - material falls through air AVALANCHES - material in air or on surface SLIDES or SLUMPS - material slides across surface FLOWS - material flows across surface. Landslide and avalanche hazards. Thousands of people killed annually world-wide
1970 - Yungay, Peru A minor earthquake loosened a small mass of glacial ice and rock on the flanks of Mt. Huascaran in the Peruvian Andes. It fell ~650 m and landed on a mass of unconsolidated rock. The resultant debris avalanche cascaded downvalley for a distance of 65 km, reaching speeds of >400 km/h. Some 25,000 to 45,000 people died in the town of Yungay and neighbouring villages.
1903 - Frank, AlbertaA rock avalanche (30 M m3) slid off the eastern face of Turtle Mountain, covering 3 km in about 100 seconds. The avalanche buried the outskirts of the mining town of Frank. Some 75 people died.
Monitored since 1933.
Wadi Al-Ayn, Hadramawt Valley, Yemen
Rockfall; Al-Dhafir, Yemen: ~50 people killed
This rockfall near Furry Creek in July 2008 covered 75 metres of the Sea to Sky Highway in rubble 10 metres deep and also took out the railway line below the highway. The highwaywas closed for 3 days.
The slope was stabilized by blasting.
Photos: Natural Resources Canada and Canadian Press
Canada’s largest rock avalanche in the historic period (January, 1965)
46 million cubic meters of rock debris avalanched down a the side of a mountain in SW BC in January 1965 forming a fan up to 80 m thick and 3 km wide, Four people driving on the Hope-Princeton Highway were killed. There is no known triggering event for this slide.
Photos: Natural Resources Canada
rain (January, 1965)
keeps material on slope
quakeSlumps, slides, etc.factors reducing slope strength
This shallow debris slide near Tacoma (WA) was initiated by the Olympia earthquake of 1949. The failure occurred several days after the earthquake. The landslide generated a small tsunami in the Narrows.
(or earthquake liquefaction)
Source: Eisbacher and Clague, 1980
Landslide videos deposits,
Slump after heavy rains (Japan)
La Conchita earthflow
Extent of the Champlain Sea (black dots = whale fossils in GM deposits)
Slides predominantly along river banks
Heavy rain from Typhoon Durian unleashed mudslides from the flanks of Mt. Mayon in the Phillipines, which had been active in July-August (top right). Photos: BBC News
3 of rain in southern Mexico - El Salvador in a 6-day period in October 2005. Debris flows and mudslides occurred in the highlands and floods in the valleys.
3Debris flows, northern Venezuelain Dec. 1999 (30 000 deaths)
Debris flow scars on hillsides
Sediment deposition on alluvial fans
Triggered by 1200 mm of rainfall in one month, including 500 mm in two days
Note debris flow scars and deposits in valleys
Note size of boulders and height of debris flow damage
From: Clague et al., 2003. Environmental and Engineering Geoscience 9, 99-115.
after (2008) before (2006)
Images: NASA Earth Observatory
At least 20 lakes were formed behind seismically-triggered landslide dams in the area affected by the Sichuan earthquake. The inhabitants of towns downstream of the dams (e.g. Beichuan) were evacuated because of the risk of debris flows and floods if the dams failed catastrophically.
Images: NASA Earth Observatory
The Río Barrancas, in northwestern Argentina, was dammed in prehistoric time by a large landslide, forming a 21-km-long lake. In 1914, the Río Barrancas breached this dam; overnight the lake surface was lowered about 95 m. The resultant debris flow/flood had an estimated volume of 2 billion m3. No data are available on casualties or damage costs downstream, but cattle ranches and farms along the 60-km canyon and valley of the Río Barrancas completely disappeared. In addition, two small towns in the valley were devastated.
Sketch of Lago Cari Lauquen on the Río Barrancas, Argentina after the dam was breached(Groeber, 1916)
Source: Baumann Engineering (Laguna Beach CA, project)
mesh + planting
landslides.usgs.gov/woodway/ (no longer continuously monitored)
Daily precipitation (green) and water table fluctuations
Extensiometersmeasure creep downslope (units = cm)
Equipment malfunctionat E-1
10 cmof rain in 24h
4 dead27 buried
Mitigation: $400,000 retaining wall (destroyed)Preparedness: some recent residents claimed to be unaware of the slide danger! Did anyone move from this subdivision to a safer location after1995?