Landslide and Debris Flow

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  • Topic: Landslide, Geology, Slope stability
  • Pages : 5 (2605 words )
  • Download(s) : 636
  • Published : January 17, 2013
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What is Landslide?
A. A landslide is when a mass of soil, rocks and other debris moves down a slope, powered by the force of gravity. Sometimes, this movement is so sudden and rapid that it causes devastating loss of life and structural damage. (,34702.asp) B. 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. ( C. Landslides occur in all U.S. states and territories. In a landslide, masses of rock, earth, or debris move down a slope. Landslides may be small or large, slow or rapid. They are activated by storms, earthquakes, volcanic eruptions, fires, and human modification of land. Landslide problems can be caused by land mismanagement, particularly in mountain, canyon, and coastal regions. Land-use zoning, professional inspections, and proper design can minimize many landslide, mudflow, and debris flow problems. ( D. Landslides are a serious geologic hazard that occurs in almost all 50 states. Every year in the United States, they cause significant damages and 25 to 50 deaths. Globally, landslides cause billions of dollars in damages and thousands of deaths and injuries each year. The term “landslide” describes many types of downhill earth movements ranging from rapidly moving catastrophic rock avalanches and debris flows in mountainous regions to more slowly moving earth slides. Some landslides move slowly and cause damage gradually, whereas others move so rapidly that they can destroy property and take lives suddenly and unexpectedly. Gravity is generally the force driving landslide movement. Landslides cause property damage, injury, and death and adversely affect a variety of resources. For example, water supplies, fisheries, sewage disposal systems, forests, dams, and roadways can be affected for years after a slide event. Landslides generally happen where they have occurred in the past, and in identifiable hazard locations. Areas that are prone to landslides include existing old landslides, the bases of steep slopes, the bases of drainage channels, and developed hillsides where leach-field septic systems are used. ( E. Landslides occur when masses of rock, earth, or debris move down a slope. ( Risks or Dangers from landslides

A. The immediate risk to human life from a landslide or mudslide is being caught in its path: sand, and thick mud especially, can cause suffocation, and people can be trapped or crushed by boulders or other debris, or by buildings collapsing under the weight of the flow. (,34702.asp) B. Landslides can also disrupt power lines and water and sewerage pipes, potentially leading to electric shock and contaminated drinking-water. Roads and other transportation arteries may be blocked by debris, raising the risk for accidents and hampering access by rescue and medical services. (,34702.asp) C. Landslides, mudflows and debris avalanches frequently accompany other natural hazards such as floods and earthquakes. The October 17, 1989 earthquake resulted in many areas of unstable land throughout the County which will...
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