Causes And Effects Of Landslides Pdf
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This work is based on a structuralexploration of the landslide areas mainly by seismicmethods. Information about the status of deformationis obtained by comparison of the actual topographywith a reconstruction of the original topography, byGPS, and by SAR interferometry. Geologic andgeomorphological evidence, as well as relevantinformation from other geo-scientific disciplines, isconsidered.
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- Landslides - Causes, Types and Effects.pdf
- Cause-Effect Models of Large Landslides
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The term landslide or, less frequently, landslip    refers to several forms of mass wasting that may include a wide range of ground movements, such as rockfalls , deep-seated slope failures, mudflows , and debris flows. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event such as a heavy rainfall , an earthquake , a slope cut to build a road, and many others , although this is not always identifiable.
Landslides occur when the slope or a portion of it undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the shear strength of the slope material, an increase in the shear stress borne by the material, or a combination of the two. 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:. In traditional usage, the term landslide has at one time or another been used to cover almost all forms of mass movement of rocks and regolith at the Earth's surface.
In , geologist David Varnes noted this imprecise usage and proposed a new, much tighter scheme for the classification of mass movements and subsidence processes. Under this classification, six types of movement are recognized. Each type can be seen both in rock and in soil. A fall is a movement of isolated blocks or chunks of soil in free-fall. The term topple refers to blocks coming away by rotation from a vertical face.
A slide is the movement of a body of material that generally remains intact while moving over one or several inclined surfaces or thin layers of material also called shear zones in which large deformations are concentrated. Slides are also sub-classified by the form of the surface s or shear zone s on which movement happens. The planes may be broadly parallel to the surface "planar slides" or spoon-shaped "rotational slides".
Slides can occur catastrophically, but movement on the surface can also be gradual and progressive. Spreads are a form of subsidence, in which a layer of material cracks, opens up, and expands laterally. Flows are the movement of fluidised material, which can be both dry or rich in water such as in mud flows. Flows can move imperceptibly for years, or accelerate rapidly and cause disasters. Slope deformations are slow, distributed movements that can affect entire mountain slopes or portions of it.
Some landslides are complex in the sense that they feature different movement types in different portions of the moving body, or they evolve from one movement type to another over time.
For example, a landslide can initiate as a rock fall or topple and then, as the blocks disintegrate upon the impact, transform into a debris slide or flow. An avalanching effect can also be present, in which the moving mass entrains additional material along its path. Slope material that becomes saturated with water may produce a debris flow or mud flow. However, also dry debris can exhibit flow-like movement.
This phenomenon is particularly hazardous in alpine areas, where narrow gorges and steep valleys are conducive of faster flows. Debris and mud flows may initiate on the slopes or result from the fluidization of landslide material as it gains speed or incorporates further debris and water along its path.
River blockages as the flow reaches a main stream can generate temporary dams. As the impoundments fail, a domino effect may be created, with a remarkable growth in the volume of the flowing mass, and in its destructive power.
An earthflow is the downslope movement of mostly fine-grained material. Though these are a lot like mudflows , overall they are more slow-moving and are covered with solid material carried along by the flow from within.
Clay, fine sand and silt, and fine-grained, pyroclastic material are all susceptible to earthflows. These flows are usually controlled by the pore water pressures within the mass, which should be high enough to produce a low shearing resistance. On the slopes, some earthflow may be recognized by their elongated shape, with one or more lobes at their toes. As these lobes spread out, drainage of the mass increases and the margins dry out, lowering the overall velocity of the flow.
This process also causes the flow to thicken. Earthflows occur more often during periods of high precipitation, which saturates the ground and builds up water pressures. However, earthflows that keep advancing also during dry seasons are not uncommon.
Fissures may develop during the movement of clayey materials, which facilitate the intrusion of water into the moving mass and produce faster responses to precipitation. A rock avalanche, sometimes referred to as sturzstrom , is a large and fast-moving landslide of the flow type.
It is rarer than other types of landslides but it is often very destructive. It exhibits typically a long runout, flowing very far over a low-angle, flat, or even slightly uphill terrain. The mechanisms favoring the long runout can be different, but they typically result in the weakening of the sliding mass as the speed increases.
Especially for the largest landslides, it may involve the very quick heating of the shear zone due to friction, which may even cause the water that is present to vaporize and build up a large pressure, producing a sort of hovercraft effect. Slides can occur in any rock or soil material and are characterized by the movement of a mass over a planar or curvilinear surface or shear zone.
It is usually triggered by the saturation of thickly vegetated slopes which results in an incoherent mixture of broken timber, smaller vegetation and other debris. This is usually a result of lower shear resistances and steeper slopes. Debris slides generally begin with the detachment of rock chunks high on the slopes, which break apart as they slide towards the bottom. Clay and silt slides are usually slow but can experience episodic acceleration in response to heavy rainfall or rapid snowmelt.
They are often seen on gentle slopes and move over planar surfaces, such as over the underlying bedrock. Failure surfaces can also form within the clay or silt layer itself, and they usually have concave shapes, resulting in rotational slides. A landslide in which the sliding surface is located within the soil mantle or weathered bedrock typically to a depth from few decimeters to some meters is called a shallow landslide.
Debris slides and debris flows are usually shallow. Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low permeable soils. The low permeable soil traps the water in the shallower soil generating high water pressures.
As the top soil is filled with water, it can become unstable and slide downslope. Deep-seated landslides are those in which the sliding surface is mostly deeply located, for instance well below the maximum rooting depth of trees. They tend to form along a plane of weakness such as a fault or bedding plane. They can be visually identified by concave scarps at the top and steep areas at the toe. Landslides that occur undersea, or have impact into water e.
Massive landslides can also generate megatsunamis , which are usually hundreds of meters high. In , one such tsunami occurred in Lituya Bay in Alaska. 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.
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. Using satellite imagery in combination with GIS and on-the-ground studies, it is possible to generate maps of likely occurrences of future landslides.
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. 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 also 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.
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 planets. 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. From Wikipedia, the free encyclopedia. Type of natural disasters involving ground movements, often caused by slope instability triggered by specific event. This article is about the geological phenomenon. For other uses, see Landslide disambiguation.
Play media. Main article: Causes of landslides. Main article: Landslide classification. See also: Slope stability analysis. Main article: List of landslides. Main article: Landslide mitigation. This article should include a summary of Landslide mitigation. See Wikipedia:Summary style for information on how to incorporate it into this article's main text.
July Roget's 21st Century Thesaurus. Retrieved 16 March Marine Geology. Siva; Fan, X. Journal of Geophysical Research: Earth Surface. Engineering Geology.
Landslides - Causes, Types and Effects.pdf
It can be rapid, very slow, or in between. It can involve large or small areas and volumes of material. The principal types of movement are falling, sliding, and flowing, but combinations of these are common. As human impact on the land increases, we both cause more landslides and are increasingly affected by natural ones. In some parts of Pennsylvania, landslides are a significant hazard.
Landslides: Causes, Types and Effects - MASS MOVEMENTS IN ADRIATIC CENTRAL ITALY: ACTIVATION AND EVOLUTIVE CONTROL FACTORS. January.
Cause-Effect Models of Large Landslides
Know how the COVID pandemic can affect disaster preparedness and recovery, and what you can do to keep yourself and others safe. Landslides occur when masses of rock, earth, or debris move down a slope. Debris flows , also known as mudslides , are a common type of fast-moving landslide that tends to flow in channels. Landslides are caused by disturbances in the natural stability of a slope.
Landslides - Causes, Types and Effects. The publisher has taken reasonable care in the preparation of this digital document, but makes noexpressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. Noliability is assumed for incidental or consequential damages in connection with or arising out of informationcontained herein. This digital document is sold with the clear underst and ing that the publisher is not engaged inrendering legal, medical or any other professional services.
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The term landslide or, less frequently, landslip    refers to several forms of mass wasting that may include a wide range of ground movements, such as rockfalls , deep-seated slope failures, mudflows , and debris flows. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event such as a heavy rainfall , an earthquake , a slope cut to build a road, and many others , although this is not always identifiable. Landslides occur when the slope or a portion of it undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the shear strength of the slope material, an increase in the shear stress borne by the material, or a combination of the two. A change in the stability of a slope can be caused by a number of factors, acting together or alone.
What is a landslide? A landslide is defined as the movement of a mass of rock, debris, or earth down a slope due to gravity. The materials may move by falling, toppling, sliding, spreading, or flowing. What causes a landslide? Almost every landslide has multiple causes.
Geographers are commonly called upon to diagnose the causes of natural disasters and provide guidance for policy makers. Causes were sought on a 7. Individual landslides were surveyed along with a suite of potential environmental indicators. These results show that the numbers of landslides on the roadbed were not unusual, so research switched to exploring factors that may have enhanced their volumes. Local opinion considers that the major causes were human impacts, especially recent urban development, or geological weaknesses.