landslide

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Ferguson Slide on California State Highway

A landslide (or landslip) is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.

Causes of landslides

The Mameyes Landslide, in barrio Tibes, Ponce, Puerto Rico, which buried more than 100 homes, was caused by extensive accumulation of rains and, according to some sources, lightning.

Landslides occur when the stability of a slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include:

• groundwater (porewater) pressure acting to destabilize the slope
• Loss or absence of vertical vegetative structure, soil nutrients, and soil structure (e.g. after a wildfire)
• erosion of the toe of a slope by rivers or ocean waves
• weakening of a slope through saturation by snowmelt, glaciers melting, or heavy rains
• earthquakes adding loads to barely-stable slopes
• earthquake-caused liquefaction destabilizing slopes (see Hope Slide)
• volcanic eruptions

landslides are aggravated by human activities, Human causes include:deforestation, cultivation and construction, which destabilize the already fragile slopes

• vibrations from machinery or traffic
• blasting
• earthwork which alters the shape of a slope, or which imposes new loads on an existing slope
• in shallow soils, the removal of deep-rooted vegetation that binds colluvium to bedrock
• Construction, agricultural or forestry activities (logging) which change the amount of water which infiltrates the soil.

The landslide at Surte in Sweden, 1950. It was a quick-clay slide killing one person.

Types of landslide

The following text needs to be harmonized with text in Landslide classification.

Debris flow

Amboori debris flow, occurred on 09^th November 2001 in Kerala, India. The event killed 39 people^[1].

Slope material that becomes saturated with water may develop into a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses and cars, thus blocking bridges and tributaries causing flooding along its path.

Debris flow is often mistaken for flash flood, but they are entirely different processes.

Muddy-debris flows in alpine areas cause severe damage to structures and infrastructure and often claim human lives. Muddy-debris flows can start as a result of slope-related factors and shallow landslides can dam stream beds, resulting in temporary water blockage. As the impoundments fail, a "domino effect" may be created, with a remarkable growth in the volume of the flowing mass, which takes up the debris in the stream channel. The solid-liquid mixture can reach densities of up to 2 tons/m³ and velocities of up to 14 m/s (Chiarle and Luino, 1998; Arattano, 2003). These processes normally cause the first severe road interruptions, due not only to deposits accumulated on the road (from several cubic metres to hundreds of cubic metres), but in some cases to the complete removal of bridges or roadways or railways crossing the stream channel. Damage usually derives from a common underestimation of mud-debris flows: in the alpine valleys, for example, bridges are frequently destroyed by the impact force of the flow because their span is usually calculated only for a water discharge. For a small basin in the Italian Alps (area = 1.76 km²) affected by a debris flow, Chiarle and Luino (1998)^{[citation needed]} estimated a peak discharge of 750 m³/s for a section located in the middle stretch of the main channel. At the same cross section, the maximum foreseeable water discharge (by HEC-1), was 19 m³/s, a value about 40 times lower than that calculated for the debris flow that occurred.

Earth flow

A rock slide in Guerrero, Mexico.

Earthflows are downslope, viscous flows of saturated, fine-grained materials, which move at any speed from slow to fast. Typically, they can move at speeds from 0.17 to 20 km/h. Though these are a lot like mudflows, overall they are slower moving and are covered with solid material carried along by flow from within. They are different from fluid flows in that they are more rapid. Clay, fine sand and silt, and fine-grained, pyroclastic material are all susceptible to earthflows. The velocity of the earthflow is all dependent on how much water content is in the flow itself: if there is more water content in the flow, the higher the velocity will be.

These flows usually begin when the pore pressures in a fine-grained mass increase until enough of the weight of the material is supported by pore water to significantly decrease the internal shearing strength of the material. This thereby creates a bulging lobe which advances with a slow, rolling motion. As these lobes spread out, drainage of the mass increases and the margins dry out, thereby lowering the overall velocity of the flow. This process causes the flow to thicken. The bulbous variety of earthflows are not that spectacular, but they are much more common than their rapid counterparts. They develop a sag at their heads and are usually derived from the slumping at the source.

Earthflows occur much more during periods of high precipitation, which saturates the ground and adds water to the slope content. Fissures develop during the movement of clay-like material creates the intrusion of water into the earthflows. Water then increases the pore-water pressure and reduces the shearing strength of the material.^[2]

Debris avalanche

Goodell Creek Debris Avalanche, WA.

A debris avalanche is a type of slide characterized by the chaotic movement of rocks soil and debris mixed with water or ice (or both). They are usually triggered by the saturation of thickly vegetated slopes which results in an incoherent mixture of broken timber, smaller vegetation and other debris.^[3] Debris avalanches differ from debris slides because their movement is much more rapid. This is usually a cause of lower cohesion or higher water content and commonly steeper slopes

Movement

Debris slides generally begin with large blocks that slump at the head of the slide and then break apart as they move towards the toe. This process is much slower than that of a debris avalanche. In a debris avalanche this progressive failure is very rapid and the entire mass seems to somewhat liquefy as it moves down the slope. This is caused by the combination of the excessive saturation of the material, and very steep slopes. As the mass moves down the slope it generally follows stream channels leaving behind a V-shaped scar that spreads out downhill. This differs from the more U-shaped scar of a slump. Debris avalanches can also travel well past the foot of the slope due to their tremendous speed.^[4]

A "slump" landslide in San Mateo County, January 1997

Sturzstrom

A sturzstrom is a rare, poorly understood type of landslide, typically with a long run-out. Often very large, these slides are unusually mobile, flowing very far over a low angle, flat, or even slightly uphill terrain.

Shallow landslide

: Hotel Limone at the Garda Lake

. Part of a hill of Devonian shale was removed to make the road, forming a dip-slope. The upper block detached along a bedding plane and is sliding down the hill, forming a jumbled pile of rock at the toe of the slide.]]

Landslide in which the sliding surface is located within the soil mantle or weathered bedrock (typically to a depth from few decimetres to some metres). They usually include debris slides, debris flow, and failures of road cut-slopes. Landslides occurring as single large blocks of rock moving slowly down slope are sometimes called block glides.

Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low permeable bottom soils. The low permeable, bottom soils trap the water in the shallower, high permeable soils creating high water pressure in the top soils. As the top soils are filled with water and become heavy, slopes can become very unstable and slide over the low permeable bottom soils. Say there is a slope with silt and sand as its top soil and bedrock as its bottom soil. During an intense rainstorm, the bedrock will keep the rain trapped in the top soils of silt and sand. As the topsoil becomes saturated and heavy, it can start to slide over the bedrock and become a shallow landslide. R. H. Campbell did a study on shallow landslides on Santa Cruz Island California. He notes that if permeability decreases with depth, a perched water table may develop in soils at intense precipitation. When pore water pressures are sufficient to reduce effective normal stress to a critical level, failure occurs.^[5]

Deep-seated landslide

Landslide of soil and regolith in Pakistan.

Landslides in which the sliding surface is mostly deeply located below the maximum rooting depth of trees (typically to depths greater than ten meters). Deep-seated landslides usually involve deep regolith, weathered rock, and/or bedrock and include large slope failure associated with translational, rotational, or complex movement.

Causing tsunami

Landslides that occur undersea, or have impact into water, can generate tsunamis. Massive landslides can also generate megatsunamis, which are usually hundreds of metres high. In 1958, one such tsunami occurred in Lituya Bay in Alaska.

Related phenomena

• An avalanche, similar in mechanism to a landslide, involves a large amount of ice, snow and rock falling quickly down the side of a mountain.
• A pyroclastic flow is caused by a collapsing cloud of hot ash, gas and rocks from a volcanic explosion that moves rapidly down an erupting volcano.

Landslide prediction mapping

Global landslide risks.

Landslide hazard analysis and mapping can provide useful information for catastrophic loss reduction, and assist in the development of guidelines for sustainable land use planning. The analysis is used to identify the factors that are related to landslides, estimate the relative contribution of factors causing slope failures, establish a relation between the factors and landslides, and to predict the landslide hazard in the future based on such a relationship ^[6]. The factors that have been used for landslide hazard analysis can usually be grouped into geomorphology, geology, land use/land cover, and hydrogeology ^[7]. Since many factors are considered for landslide hazard mapping, GIS is an appropriate tool because it has functions of collection, storage, manipulation, display, and analysis of large amounts of spatially referenced data which can be handled fast and effectively ^[8]. Remote sensing techniques are also highly employed for landslide hazard assessment and analysis. Before and after aerial photographs and satellite imagery are used to gather landslide characteristics, like distribution and classification, and factors like slope, lithology, and land use/land cover to be used to help predict future events ^[9]. Before and after imagery also helps to reveal how the landscape changed after an event, what may have triggered the landslide, and shows the process of regeneration and recovery ^[10].

Using satellite imagery in combination with GIS and on-the-ground studies, it is possible to generate maps of likely occurrences of future landslides ^[11]. Such maps should show the locations of previous events as well as clearly indicate the probable locations of future events. In general, to predict landslides, one must assume that their occurrence is determined by certain geologic factors, and that future landslides will occur under the same conditions as past events ^[12]. Therefore, it is necessary to establish a relationship between the geomorphologic conditions in which the past events took place and the expected future conditions ^[13].

Natural disasters are a dramatic example of people living in conflict with the environment. Early predictions and warnings are essential for the reduction of property damage and loss of life. Because landslides occur frequently and can represent some of the most destructive forces on earth, it is imperative to have a good understanding as to what causes them and how people can either help prevent them from occurring or simply avoid them when they do occur. Sustainable land management and development is an essential key to reducing the negative impacts felt by landslides.

GIS offers a superior method for landslide analysis because it allows one to capture, store, manipulate, analyze, and display large amounts of data quickly and effectively. Because so many variables are involved, it is important to be able to overlay the many layers of data to develop a full and accurate portrayal of what is taking place on the earth’s surface. Researchers need to know which variables are the most important factors that trigger landslides in any given location. Using GIS, extremely detailed maps can be generated to show past events and likely future events which have the potential to save lives, property, and money.

Prehistoric landslides

The Hope Slide in British Columbia, Canada.

• The Agulhas slide, ca. 20,000 km³, off South Africa, post-Pliocene in age, the largest so far described^[14]
• The Storegga Slide, Norway, ca. 3,500 km³, ca. 8,000 years ago
• The Ruatoria debris avalanche, off North Island New Zealand, ca. 3,000 km³ in volume, 170,000 years ago[1].
• The landslide around 200BC which formed Lake Waikaremoana on the North Island of New Zealand, where a large block of the Ngamoko Range slid and dammed a gorge of Waikaretaheke River between the Ngamoko and Panekiri ranges, forming a natural reservior up to 248 metres deep.
• Landslide which moved Heart Mountain to its current location, Park County, Wyoming, the largest ever discovered on land.

Historical landslides

19th Century

• Cliff landslip of the Undercliff near Lyme Regis, Dorset, England, on 24 December 1839
• The Cap Diamant Québec rockslide on September 19, 1889

20th Century

• Frank Slide, Turtle Mountain, Alberta, Canada, on 29 April 1903
• Gros Ventre landslide in Wyoming, United States, on June 23, 1925
• Mount Serrat landslide in Santos, Brazil on March 1928.^{[citation needed]}
• Ricardo Calma landslide in Peru on February 1932^{[citation needed]}
• Tantaday landslide in Peru on March 1933^{[citation needed]}
• Lokchang (present day of Lechang) landslide in Shaoguan, Guangdong, China on May 1934^{[citation needed]}
• Tsumagoi mudslide with Kogushi sulphur mine damage in Gunma, Japan on November 1937.^{[citation needed]}
• Mount Rokko mudslide by heavy rain in Kobe, Hyogo, Japan on July 1938.^{[citation needed]}
• Mongui village landslide in Boyaca, Colombia on November 1941.^{[citation needed]}
• Guwahati Landslide in Assam, India on September 1948.^{[citation needed]}
• Khait landslide, Khait, Tajikistan, Soviet Union, on July 10, 1949
• Condor Hill landslide in Ancash, Peru on January 1951.^{[citation needed]}
• Mapou landslide by Hurricane Hazel in Haiti on October 1954.^{[citation needed]}
• Molina di Vietri and Ponte Romano landslide in Salerno, Italy on October 1954.^{[citation needed]}
• Shillong landslide in Meghalaya, India on June 1958^{[citation needed]}
• The Riñihuazo landslide in Chile after the Great Chilean Earthquake, on 22 May 1960
• Babi Yar landslide in Kurenivka, Ukraine on April 1961.^{[citation needed]}
• Ranrahirca landslide in Peru on January 1962.^{[citation needed]}
• Tara landslide in Kyushu, Japan, on July 1962^{[citation needed]}
• Tampayacta landslide in Peru on March 1963.^{[citation needed]}
• Changsungpo village landslide in Koje Island, South Korea on June 1963.^{[citation needed]}
• Chepe Ghat landslide in Gorkha District, Nepal on August 1963.^{[citation needed]}
• Monte Toc landslide (260 millions cubic metres) falling into the Vajont Dam basin in Italy, causing a megatsunami and about 2000 casualties, on October 9, 1963
• Hope Slide landslide (46 million cubic metres) near Hope, British Columbia on January 9, 1965.^[15]
• El Cobre landslide with El Soldado cooper mine damage in Atacama, Chile on February 1965.^{[citation needed]}
• The 1966 Aberfan disaster
• Santa Teresa landslide in Rio State, Brazil on February 1967.^{[citation needed]}
• Caraguatatuba landslide in State of São Paulo, Brazil on March 1967.^{[citation needed]}
• Kure mudslide by Typhoon Billie in Hiroshima, Japan on July 1967.^{[citation needed]}
• Hida River landslide with two charter buses plunge in Gero, Gifu, Japan on August 1968.^{[citation needed]}
• Darjeeling landslide in West Bengal on October 1968.^{[citation needed]}
• Amherst and Nelson landslide by Hurricane Camille in Virginia on August 1969.^{[citation needed]}
• the May 31, 1970 slide from Cerro Huascaran that buried the town of Yungay.
• Cauca River valley landslide in Caldas, Colombia, on December 1970^{[citation needed]}
• Chungar landslide by avalanche in Peru, on March 1971.^{[citation needed]}
• Saint-Jean-Vianney, Quebec, Canada. Small village near Saguenay river destroyed in May 1971.^[16]
• Khinjan Pass landslide in Baghian, Afghanistan on July 1971.^{[citation needed]}
• Tosayamada landslide in Shikoku, Japan on July 1972.^{[citation needed]}
• Amakusa mudslide in Kumamoto, Kyushu, Japan on July 1972.^{[citation needed]}
• Moyomarca hill mudslide in Huancayo, Peru on April 1974.^{[citation needed]}
• Quebradablanca avalanche with swept 33 vehicle in Boyaca, Colombia on June 1974.^{[citation needed]}
• Pahire Phedi landslide in Nepal on June 1976.^{[citation needed]}
• Baliem Valley landslide by 1976 Papua earthquake in Irian Jaya, Indonesia on July 1976.^{[citation needed]}
• Nilgiri Hills landslide in Tamil Nadu, India on November 1978^{[citation needed]}
• The 1979 Abbotsford landslip, Dunedin, New Zealand on August 8, 1979.
• Landslides associated with the Mount St. Helens eruption on May 18, 1980.
• Mount Semeru landslide by heavy rain in East Java, Indonesia on August 1981^{[citation needed]}
• Nakajima landslide in Nagasaki, Kyushu, Japan on July 1982^{[citation needed]}
• Ataco mudslide in El Salvador on September 1982^{[citation needed]}
• Dongxing landslide in Gansu, China, on March 1983^{[citation needed]}
• Thistle, Utah on 14 April 1983
• Chunchi mudslide in Chimborazo, Ecuador on April 1983^{[citation needed]}
• Almora landslide in Uttar Pradesh, India on July 1983^{[citation needed]}
• Dongchuan landslide in Yunnan, China on May 1984^{[citation needed]}
• The Mameyes Disaster - Ponce, Puerto Rico on October 7, 1985
• Val Pola landslide during Valtellina disaster (1987) Italy
• El Limon mudslide in Aragua, Venezuela on September 1987.^{[citation needed]}
• Villatina mudslide in Colombia on September 1987.^{[citation needed]}
• Wuxi County landslide in Sichuan, China on September 1987.^{[citation needed]}
• Macka landslide in Trabzon, Turkey on June 1988^{[citation needed]}
• Darwang and Niskot landslide in Myagdi, Nepal on September 1988.^{[citation needed]}
• Sharora landslide by 1989 Tajikistan earthquale in Hisor District, Tajikistan on January 1989.^{[citation needed]}
• Tsablanca landslide in Georgia on April 1989.^{[citation needed]}
• Bhaji landslide in Maharashtra, India on July 1989^{[citation needed]}
• Calama mudslide in Atacama, Chile on June 1991.^{[citation needed]}
• 1991 Punjabi landslide, [India] on 11 June, 1991.
• Zhaotong landslide by torrential rain, in Yunnan, China on September 1991^{[citation needed]}
• Ninghai mudslide in Zhejiang, China on September 1992.^{[citation needed]}
• Nambija Bajo mudslide in Zamora, Ecuador on May 1993.^{[citation needed]}
• The Pantai Remis landslide in 1993 in an abandoned coastal tin mine in Malaysia, forming a new cove
• Kagoshima mudslide in Kyushu, Japan on August 1993.^{[citation needed]}
• Yuangyang mudslide in Yunnan, China on July 1994^{[citation needed]}
• Khooni Nallah and Banihal tunnel avalanche in Jammu and Kashimir region, India on January 1995.^{[citation needed]}
• Wakhan landslide in Badakhshan, Afghanistan on April 1995.^{[citation needed]}
• Cheorwon landslide in Gangwon, South Korea on July 1996.^{[citation needed]}
• Tamburco mudslide by torrential rain in Apurimac Region, Peru on February 1997.^{[citation needed]}
• Thredbo landslide, Australia on 30 July 1997, destroyed hostel.
• Pithoragarh mudslide in Uttar Pradesh, India on August 1998^{[citation needed]}
• Lishui landslide in Zhejiang, China on September 1999^{[citation needed]}
• The Vargas tragedy, due to heavy rains in Vargas State, Venezuela, on December, 1999, causing tens of thousands of casualties.

21st Century

• Payatas, Manila garbage slide on 11 July 2000.^{[citation needed]}
• Mianning landslide by torrential rain in Liangshan, Sichuan, China on July 2000^{[citation needed]}
• Amboori landslide, in Kerala, 2001
• Danba mudslide in Sichuan, China on July 2003^{[citation needed]}
• Zuojiaying landslide in Nayong, Guizhou, China on December 2004^{[citation needed]}

• La Conchita mudslide in California, United States on January 10, 2005, killed 10 people and destroyed 18 homes
• Jaigaon mudslide in Maharashtra, India on July 2005^{[citation needed]}
• Southern Leyte landslide in the Philippines on 17 February 2006
• Devil's Slide, an ongoing landslide in San Mateo County, California
• Landslide in Sulawesi, Indonesia, June 2006.^[17]
• Liangshan mudslide in Sichuan, China on May 2007^{[citation needed]}
• 2007 Chittagong mudslide, in Chittagong, Bangladesh, on June 11, 2007.
• 2008 Cairo landslide on September 6, 2008.
• Xiangfen County mudslide with unlicensed Tashan coal mine collapse in Shanxi, China on September 2008.^{[citation needed]}
• Lincang mudslide in Yunnan, China on November 2008^{[citation needed]}
• Wulong mudslide in Chongqing, China on July 2009^{[citation needed]}
• Hofu mudslide in Yamaguchi, Japan on July 2009.^{[citation needed]}
• Liuzhou, Guangxi Region, China - derailed train, killing 4 ^[18]
• Shiaolin landslide by Typhoon Morakot in Tainan County, Taiwan on August 2009^{[citation needed]}
• Nile Valley Landslide, no injuries but destroyed some houses, obliterated a quarter mile of Washington State Route 410 and redirecting the Naches River 10 miles west of Naches, Washington on 11 October 2009.
• Bayambang and Alcala landslide in Benguet, Philippines on October 2009.^{[citation needed]}
• San Vicente and San Salvador mudslide by Hurricane Ida in El Salvador on November 2009.^{[citation needed]}

Extraterrestrial landslides

Before and after radar images of a landslide on Venus. In the center of the image on the right, the new landslide, a bright, flow-like area, can be seen extending to the left of a bright fracture. 1990 image.

Landslide in progress on Mars, 2008-02-19.

Evidence of past landslides has been detected on many bodies in the solar system, but since most observations are made by probes that only observe for a limited time and most bodies in the solar system appear to be geologically inactive not many landslides are known to have happened in recent times. Both Venus and Mars have been subject to long-term mapping by orbiting satellites, and examples of landslides have been observed on both.

See also

An infra-red view of a landslide in the Valley of the Geysers.

• Automatic Deformation Monitoring System
• Deformation monitoring
• Earthquake engineering
• Geotechnics
• Geotechnical engineering
• Landslide dam
• Landslide mitigation
• Mass wasting
• Slope stability
• Sturzstrom
• Submarine landslide
• Washaway
• Mudslide
• California landslides

References

• Pudasaini, Shiva P., Hutter, Kolumban, Avalanche Dynamics: Dynamics of Rapid Flows of Dense Granular Avalanches. Springer, Berlin, New York, 2007, ISBN 3-540-32686-3
• Pradhan, B., Lee, S. Use of geospatial data for the development of fuzzy algebraic operators to landslide hazard mapping: a case study in Malaysia. Applied Geomatics, Springer, Berlin, 2009, DOI 10.1007/s12518-009-0001-5
• Chen,Z. and J. Wang. 2007. Landslide hazard mapping using logistic regression model in Mackenzie Valley, Canada. Natural Hazards 42:75-89.
• Lee, S. Pradhan, B. Probabilistic Landslide Risk Mapping at Penang Island, Malaysia. Earth System Science, 2006, vol. 115, No. 6, December, pp. 1-12. (Springer publication)
• Pradhan, B., Singh, R.P., Buchroithner, M.F. Estimation of Stress and Its Use in Evaluation of Landslide Prone Regions Using Remote Sensing Data”. Advance in Space Research, 2005, vol. 37, pp: 698 – 709, Elsevier publication, http://dx.doi.org/10.1016/j.asr.2005.03.137
• Pradhan, B., Lee, S. Utilization of optical remote sensing data and geographic information system tools for regional landslide hazard analysis by using binomial logistic regression model. Applied Remote Sensing, 2008, SPIE, Vol. 2: pp:1-11
• Clerici, A.; S. Perego; C. Tellini; P.Vescavi. 2002. A procedure for landslide susceptibility zonation by the conditional analysis method. Geomorphology 48(4):349-364.
• Metternicht, G.; L. Hurni; R. Gogu. 2005. Remote sensing of landslides: An analysis of the potential contribution to geo-spatial systems for hazard assessment in mountainous environments. Remote Sensing of Environment 98: 284-303.
• De La Ville, N.; A.C. Diaz; D. Ramirez. 2002. Remote sensing and GIS technologies as tools to support sustainable management of areas devastated by landslides. Environment, Development, and Sustainability 4: 221-229.
• Fabbri, A.; C. Chung; A. Cendrero; J. Remondo. 2003. Is prediction of future landslides possible with a GIS? Natural Hazards 30: 487-499.
• Lee, S. and J.A. Talib. 2005. Probabilistic landslide susceptibility and factor effect analysis. Environmental Geology 47: 982-990.
• Olmacher, G.C. and J.C. Davis. 2003. Using multiple logistic regression and GIS technology to predict landslide hazard in northeast Kansas, USA. Engineering Geology 69(3-4): 331-343.

External links

Wikimedia Commons has media related to: Landslide

• United States Geological Survey site
• British Geological Survey landslides site
• European Soil Portal, Landslides
• British Columbia government landslide information
• Slide!, a program on B.C.'s Knowledge Network, with video clips
• Geoscience Australia Fact Sheet [2]
• Pictures of Slope Failure
• JTC1 Joint International Technical Committee on Landslides and Engineered Slopes