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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

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  • 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
Landslide and avalanche hazards

  • Thousands of people killed annually world-wide

  • Annual property damage ~$1.5 billion in USA, probably tens of billions world-wide

  • Small to medium-sized events responsible for most of the property damage

Examples of landslide disasters
Examples of landslide disasters

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.

Examples of landslide disasters1
Examples of landslide disasters

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.

Canada landslide fatalities by province 1840 present
Canada: landslide fatalities by province (1840 - present)

Frank slide

Canada fatalities by source 1840 present
Canada: fatalities by source (1840 - present)

Falls slides slumps and flows
Falls, slides, slumps and flows

  • Slope angle - the steeper the gradient, the more likely it is to fail

  • Substrate - unconsolidated sediments and fractured rocks more prone to failure than massive or well-cemented rocks

  • Water - the more saturated the material, the more likely it is to fail

Rockfall hazards in montane areas
Rockfall hazards in montane areas

Wadi Al-Ayn, Hadramawt Valley, Yemen

Rockfall; Al-Dhafir, Yemen: ~50 people killed

(December, 2005)

Sacred falls park oahu 1999 rockfall 8 deaths many injuries
Sacred Falls Park, Oahu1999 Rockfall8 deaths, many injuries

Rockfall camp curry yosemite n p 1999 1 death
Rockfall, Camp Curry,Yosemite N.P., 1999(1 death)

Camp curry yosemite n p release areas rockfall zones
Camp Curry, Yosemite N.P.Release areas &rockfall zones

Rockfalls bc
Rockfalls: BC

Fraser Canyon

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

  • Rock/debris avalanches - Rubble Creek (January, 1965)

  • Site of two large debris avalanches and several debris flow during the Holocene.

  • Source of the landslides is The Barrier, which is a precipitous rock face formed by a 300 m thick lava flow which abutted against a glacier occupying Cheakamus valley in the late glacial. Much of the landslide debris from this cliff has formed a fan at the mouth of Rubble Creek.

  • The fan consists of 5 - 10 landslide units, each 5 - 10 m in thickness. Total volume ~ 170 million cubic metres.

  • Most recent failure occurred in 1855-56. That avalanche (~ 30 million cubic metres) traveled 6 km down Rubble Creek at a speed of 60 m/s in the upper part of the path, and 25-40 m/s down-valley.

The barrier source of rubble creek rock avalanche
The Barrier : source of Rubble Creek (January, 1965)rock avalanche

Slumps slides etc factors reducing slope strength

rain (January, 1965)


Frictional strength

keeps material on slope




Slumps, slides, etc.factors reducing slope strength


Earthquake induced landslides
Earthquake-induced landslides (January, 1965)

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.

Debris slides in unconsolidated glacial and fluvio-glacial deposits,Puget Sound(Dec 1996)Triggered by record rainfalls in one week

Surficial geology seattle area
Surficial geology: deposits,Seattle area

(or earthquake liquefaction)

“piping” ?



C haracteristic of massive fine textured deposits
C deposits,haracteristic of massive fine-textured deposits

Escarpments and landslide risk areas in the gvrd
Escarpments and landslide risk areas in the GVRD deposits,

Source: Eisbacher and Clague, 1980

La conchita earthflow california
La Conchita deposits,earthflow,California

Landslide videos deposits,

Slump after heavy rains (Japan)

La Conchita earthflow

Flowslides rapid earthflows e g in leda clays qu bec norway
Flowslides deposits,= rapid earthflows(e.g. in leda clays)Québec, Norway

Landslides in glaciomarine clays of the champlain sea
Landslides in glaciomarine clays of the Champlain Sea deposits,

Extent of the Champlain Sea (black dots = whale fossils in GM deposits)

Slides predominantly along river banks

Flowslide st jean vianney qu 1971 31 deaths 40 houses destroyed
Flowslide deposits,St.-Jean-Vianney, Qué., 1971(31 deaths, 40 houses destroyed)

Aerial photo of flowslide nicolet qu bec 1955 the church circled was later demolished
Aerial photo of flowslide, Nicolet, Québec (1955) deposits,The church (circled) was later demolished

Debris flows typhoon durian philippines dec 2006
Debris flows, Typhoon Durian, Philippines deposits,(Dec. 2006)

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

  • Hurricane Stan (and other storms) dumped upwards of 500 mm 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.

  • >1500 people died in Guatemala. Most of the deaths occurred in the small town of Panabaj, which was engulfed in a mudslide up to 12m thick. As in the Phillipines, the mudslides were derived from recent volcanic deposits.

Debris flows northern venezuela in dec 1999 30 000 deaths

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.






Debris 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

Settlements in canyons and on alluvial fans along narrow coastal strip
Settlements in canyons and on alluvial fans along narrow coastal strip


Note debris flow scars and deposits in valleys

Note size of boulders and height of debris flow damage

Debris flow in north vancouver dec 2005
Debris flow in North Vancouver, Dec. 2005 coastal strip

  • 1 death

  • North Van. District purchased properties at risk; installed piezometers to monitor water-table fluctuations.

  • Cheekye Fan coastal strip

  • Site of many large debris avalanches and several moderate to large debris flows during the Holocene.

  • Source of the landslides is the west flank of the volcanic cone of Mt. Garibaldi, which may have been partly built on top of valley ice in the late glacial. This flank is therefore subject to collapse. Much of the landslide debris from this cliff has formed a fan at the mouth of the Cheekye River.

  • The fan consists of many landslide units, only some of which have been adequately dated. Total volume ~ 2.5 - 3 billion cubic metres.

  • Debris flows have continued in historic times. In 1958 a debris flow swept down the Cheekye River and formed a 5 m dam across the Cheakamus at its mouth. A similar event occurred in the 1930’s. Flow volumes were ~100 000 cubic metres.

Stump lake cores
Stump Lake cores coastal strip

From: Clague et al., 2003. Environmental and Engineering Geoscience 9, 99-115.

Landslide dams
Landslide dams coastal strip

  • Large landslides may form temporary dams across valleys; e.g. oral traditions describe Native Americans crossing the Columbia River on the “Bridge of the Gods” slide complex (product of AD1700 megaearthquake?)

  • Landslide dams may fail catastrophically

Landslides sichuan earthquake may 2008
Landslides, Sichuan earthquake: May 2008 coastal strip

after (2008) before (2006)

Images: NASA Earth Observatory

Lake formed by landslide dam sichuan may 2008
Lake formed by landslide dam, Sichuan, May 2008 coastal strip

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

Landslide dam failures
Landslide dam failures coastal strip

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.

landslide scar

lake outlet

Sketch of Lago Cari Lauquen on the Río Barrancas, Argentina after the dam was breached(Groeber, 1916)

Preventive measures rockfalls
Preventive measures: rockfalls coastal strip

  • Rock bolts (tie loose rocks to stable base)

  • Shotcrete (debris adheres to stable base)

  • Guard mesh (captures rockfall material)

  • Drainage pipes (relieve pore pressure in basal rocks)

  • Rockfall sheds (deflect material over highways, etc.)

Protection mitigation rockfall shed on highway taiwan
Protection/mitigation coastal strip(rockfall shed on highway, Taiwan)

Protection mitigation hybrid hard soft landscaping solutions
Protection/mitigation: coastal striphybrid “hard-soft” landscaping solutions

Source: Baumann Engineering (Laguna Beach CA, project)


mesh + planting

Monitoring of high risk landslides e extensiometers b instrumented boreholes
Monitoring of high-risk landslides coastal stripE=extensiometersB= instrumentedboreholes

Woodway (no longer continuously monitored)

Woodway coastal strip

Daily precipitation (green) and water table fluctuations

Extensiometersmeasure creep downslope (units = cm)

Equipment malfunctionat E-1

Prevention mitigation trench drainage of toe of active slide scotland
Prevention/mitigation coastal strip(trench drainage of toe of active slide, Scotland)

Mitigation debris torrent chute in alps
Mitigation coastal strip(debris torrent chute in Alps)

La conchita ii ventura co ca jan 10 2005
La Conchita II, coastal stripVentura Co. [CA]: (Jan. 10, 2005)


10 cmof rain in 24h

4 dead27 buried

La conchita ii why
La Conchita II: why? coastal strip

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?