Land slidesMade by :Aditya Julka And Paritosh . deep failure of slopes and shallow debris flows. which can occur in offshore. . Although the action of gravity is the primary driving force for a landslide to occur. Typically. there are other contributing factors affecting the original slope stability. whereas the actual landslide often requires a trigger before being released. preconditional factors build up specific subsurface conditions that make the area/slope prone to failure. A landslide is a geological phenomenon which includes a wide range of ground movement. coastal and onshore environments. such as rock falls. They can occur along a slope where the internal resistance of the rocks are reduced or they loose their holding capacity. The scar above a landslide is easily visible. particularly for construction of roads. Large block known as a slump block moves during the landslide. . Common after earthquakes or after removal of part of the slope due to construction. are failure of unconsolidated material on a surface. lakes etc. strength (a resisting decreases and the weight (a force increases). Rock slide or Rock Fall – where movement of large rock block rolls They are also common along the steep banks of rivers. key to Shear force) driving . During the movement landslide can result into the Debris slides . Pore Water Pressure is the monitoring landslides. Talus – accumulation formed by the coarser rock fragments resulted from the mechanical weathering along a slope under influence of gravity . g. or heavy rains earthquakes adding loads to barely-stable slope earthquake-caused liquefaction destabilizing slopes volcanic eruptions . after a wildfire) erosion of the toe of a slope by rivers or ocean waves weakening of a slope through saturation by snowmelt. Natural causes of landslides include: groundwater pressure acting to destabilize the slope Loss or absence of vertical vegetative structure. soil nutrients.Landslides occur when the stability of a slope changes from a stable to an unstable condition. glaciers melting. and soil structure (e. acting together or alone. A change in the stability of a slope can be caused by a number of factors. the removal of deeprooted vegetation that binds colluviums to bedrock Construction. cultivation and construction. .landslides are aggravated by human activities. Human causes include: deforestation. agricultural or forestry activities (logging) which change the amount of water which infiltrates the soil. or which imposes new loads on an existing slope in shallow soils. which destabilize the already fragile slopes vibrations from machinery or traffic blasting earthwork which alters the shape of a slope. what may have triggered the landslide. GIS is an appropriate tool because it has functions of collection. The factors that have been used for landslide hazard analysis can usually be grouped into geomorphology. land use/land cover. estimate the relative contribution of factors causing slope failures. manipulation. geology. and analysis of large amounts of spatially referenced data which can be handled fast and effectively. and factors like slope. and to predict the landslide hazard in the future based on such a relationship. and land use/land cover to be used to help predict future events. Before and after imagery also helps to reveal how the landscape changed after an event. and shows the process of regeneration and recovery. Before and after aerial photographs and satellite imagery are used to gather landslide characteristics. Since many factors are considered for landslide hazard mapping. Landslide hazard analysis and mapping can provide useful information for catastrophic loss reduction. lithology.Remote sensing techniques are also highly employed for landslide hazard assessment and analysis. . display. like distribution and classification. storage. and hydrogeology. establish a relation between the factors and landslides. 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. Because so many variables are involved. manipulate. Sustainable land management and development is an essential key to reducing the negative impacts felt by landslides. 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. extremely detailed maps can be generated to show past events and likely future events which have the potential to save lives. Early predictions and warnings are essential for the reduction of property damage and loss of life. Using satellite imagery in combination with GIS and on-the-ground studies. 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. and display large amounts of data quickly and effectively. to predict landslides. Because landslides occur frequently and can represent some of the most destructive forces on earth. Natural disasters are a dramatic example of people living in conflict with the environment. property. Therefore. and that future landslides will occur under the same conditions as past events. store. GIS offers a superior method for landslide analysis because it allows one to capture. and money. it is possible to generate maps of likely occurrences of future landslides. one must assume that their occurrence is determined by certain geologic factors. analyze. it is necessary to establish a relationship between the geomorphologic conditions in which the past events took place and the expected future conditions. Such maps should show the locations of previous events as well as clearly indicate the probable locations of future events. Researchers need to know which variables are the most important factors that trigger landslides in any given location. Using GIS. In general. . 25 km2 (9.7 sq mi). Cheekye Fan. Canada. the largest so far described in the alps and on dry land that can be easily identified in a modestly eroded state. some 10000 years ago in post-glacial Pleistocene/Holocene. the largest ever discovered on land. In the 48 million years since the slide occurred. Rhine cutting through Flims Rockslide debris. erosion has removed most of the portion of the slide. The landslide around 200BC which formed Lake Waikaremoana on the North Island of New Zealand. forming a natural reservoir up to 248 metres deep. Flims Rockslide. . Switzerland Landslide which moved Heart Mountain to its current location. Late Pleistocene in age. 13. ca.100 cu mi). Switzerland. British Columbia. where a large block of the Ngamoko Range slid and dammed a gorge of Waikaretaheke River.000 km3 (3. ca. Indonesia 32 dead Landslide caused by collapse of caldera wall 10 January 2005 17 February 2006 La Conchita. California. Egypt 2008 Cairo landslide 119 . India 40 dead Supposedly worst landslide in Kerala state's history. individual boulders up to 70 tonnes Southern Leyte.Date Place name Casualties comments 9 November 2001 Amboori.Philippines 1. Rock-debris avalanche triggered by ten day period of heavy rain Series of landslides caused by illegal hillside cutting and monsoon rains Rockfall from cliffs.United States 2005 La Conchita Landslide 2006 Southern Leyte mudslide 2007 Chittagong mudslides 10 dead Remobilization of colluvium from 1995 slide into a debris flow. 26 March 2004 Mount Bawakaraeng.Bangladesh 123+ 6 September 2008 Cairo.South Sulawesi.126 11 June 2007 Chittagong. Kerala. China 2010 Jiangxi train derailment The landslide was caused by previous days of heavy rain and flooding in the region.Taiwan 439 to 600 4 January 2010 Attabad. British Columbia. Gilgit-Baltistan. Quebec 4 dead 6 August 2010 Meager Creek.Kaohsiung County. 2010 Gansu. China Zhouqu county mudslide 1287 killed and 457 missing .9 August 2009 Xiaolin (or Hsiao-Lin). 10 May 2010 Saint-Jude. Pakistan Hunza Valley Landslide 20 Formed Attabad Lake by dammingHunza River. Canada Second-largest landslide in Canada history August 8.Uganda 2010 Ugandan landslide 100-300 dead 23 May 2010 Jiang Zhidong Jiangxi. blocked Karakoram Highway 1 March 2010 Bududa District. . causes triggered by anthropic activities such as adding excessive weight above the slope. often individual phenomena join together to generate instability. slope stabilisation methods in rock or in earth. to classify the work as a function of the phenomenon or of more important phenomena. Landslides can be triggered by many often concomitant causes. at different times. In addition to shallow erosion or reduction of sheer strength caused by seasonal rainfall. It is therefore pointless. other than in well-instrumented limited areas. renouncing any attempt to precisely describe all the causes or the conditions which. can also be included.Landslide mitigation refers to lessen the effect of landslides by constructing various man made projects at the slopes which are vulnerable to landslides planning for landslides hazard mitigation as its phenomenon is instant. which. digging at mid-slope or at the foot of the slope. also after some time has elapsed. can be collocated into three types of measure: . for the purpose of planning landslide hazard mitigation measures. Therefore. contribute to the occurrence of the landslide. However. do not allow a reconstruction of the evolution of the occurred landslide. in which attempts are made to increase the shear strength of the unstable mass or to introduce active external forces (e. Chemical and mechanical methods. rock or ground nailing) or passive (e.g. in principle. structural wells. Geometric methods. The different type of material conditions the engineering solution adopted. .g. anchors. in which the geometry of the hillside is changed (in general the slope). in which an attempt is made to lower the groundwater level or to reduce the water content of the material. Hydrogeological methods. to the previously introduced classification. although It always comes back. piles or reinforced ground) to contrast the destabilising forces.