Landslide presentation
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1) A landslide is the downward or outward movement of soil, rock, or vegetation under the influence of gravity. It occurs when the resisting forces that prevent sliding are less than the driving forces that cause it. 2) Landslides can be caused by both natural factors like heavy rainfall, earthquakes, and steep slopes, as well as human factors like deforestation and construction activities. 3) Landslides can have devastating direct effects like physical damage, casualties, and flooding, as well as indirect economic impacts. Proper drainage, retaining walls, reforestation, and land use planning can help minimize landslide hazards.
Landslide presentation
- 1. PRESENTATION ON LANDSLIDES Presented By :- Ranjit Subba Dept. Of E.S.S Msc. IIIrd Sem.
- 2. A landslide is a downward or outward movement of soil, rock or vegetation, under the influence of gravity.
- 3. INTRODUCTION • A landslide is a downward or outward movement of soil, rock or vegetation, under the influence of gravity. • Factor of Safety(F); Resisting Force(R) F = Driving Force(D) When, F< 1 = landslide occur • Resisting forces(R) preventing the mass from sliding down the slope are inversely proportional to the same hill slope angle and directly proportional to the friction angle of the material. 3
- 4. In addition, the resisting forces can be significantly reduced in case of rain or earthquake vibrations. Three distinct physical events occur during a landslide: 1) The initial slope failure, 2) The subsequent transport, and 3) The final deposition of the slide materials. Types of landslide:
- 5. The speed of the movement may range from very slow to rapid. The speed of the landslide will make an even more or less avoidable and therefore, more or less risky. It is important to distinguish the different types of landslides to be able to understand how to deal with each of them.
- 6. a) Rotational slides move along a surface of rupture that is curved and concave. b) Translational slides occurs when the failure surface is approximately flat or slightly undulated
- 7. c) Rock Fall Free falling of detached bodies of bedrock (boulders) from a cliff or steep slope. d) Rock toppling occurs when one or more rock units rotate about their base and Collapse.
- 8. e) Lateral spreading occurs when the soil mass spreads laterally and this spreading comes with tensional cracks in the soil mass. f) Debris Flow Down slope movement of collapsed, unconsolidated material typically along a stream channel.
- 9. A) Natural Factors: Gravity: Gravity works more effectively on steeper slopes. Geological factors: Geology setting that places permeable sands and gravels above impermeable layers of silt and clay or bedrock. Heavy and prolonged rainfall: slides occur often with intense rain by creating zone of weakness, also water tables rise with heavy rain makes some slopes unstable. Earthquakes: Ground vibrations created during Earthquakes.
- 10. Waves: Wave action can erode the beach or the toe of a cliff, cutting into the slope, and setting the stage for future slides. Volcanoes: volcanic ash deposits (sometimes called as lahars deposits) are prone to erosion and subjected to mud flows due to intense rainfall. Fluctuation of water levels due to the tidal action.
- 11. B) Anthropogenic Factors: Inappropriate drainage system: Surface runoff of irrigated water on slopes exposes soil under cultivation to erosion. Part of this water is absorbed by soil increasing its weight, which can put an additional load on the slope. Cutting & deep excavations on slopes for buildings, roads, canals & mining: causes modification of natural slopes, blocking of surface drainage, loading of critical slopes and withdrawal to toe support promoting vulnerability of critical slopes.
- 12. A) Direct Effects Physical Damage Debris may block roads, supply lines (telecommunication, electricity, water, etc.) and waterways. Causalities Deaths and injuries to people and animals. B) Indirect Effects Influence of landslides in dam safety Failure of the slopes bordering the reservoir, Flooding caused by movements of large masses of soil into the reservoir.
- 13. Landslides and flooding Debris flow can cause flooding by blocking valleys and stream channels, forcing large amounts of water to backup causing backup/ flash flood. C) Direct losses Loss of life, property, infrastructure and lifeline facilities, Resources, farmland and places of cultural importance. D) Indirect losses Loss in productivity of agricultural or forest lands, Reduced property values, Loss of revenue, Increased cost, Adverse effect on water quality and Loss of human productivity
- 14. How to Minimize Landslide Hazards A) Passive Intervention • Choose a safe location to build your home, away from steep slopes and places where landslides have occurred in the past. • Prevent deforestation and vegetation removal. • Avoid weakening the slope. B) Active Preventive Intervention • Reforestation: Root systems bind materials together and plants do both prevent water percolation and take water up out of the slope. • Proper water runoff must be ensured by providing a proper canalization network. • Drainage: good ground drainage is essential to prevent saturation and consequent weakening. Drainage is also needed in civil work, like retaining walls.
- 15. • Proper land use measures: Adopt effective land-use regulations and building codes based on scientific research. • Structural measures: Nets, Retaining walls and major civil works to mitigate landslides. C) Non- Structural measures: • Awareness generation: Educate the public about signs that a landslide is imminent so that personal safety measures may be taken. • Financial Mechanisms: Support the establishment of landslide insurance. • Legal and Policy: legislation to direct a governmental or private program to reduce landslide losses should be strengthened. D) Landslide Hazard Mapping and Use of GIS: • Landslide Hazard Zones of the Vulnerable Areas. • Use of remote sensing and ground truth data for making landslide hazard zone map. • Here, such maps are used to develop mitigation plans in consultation with experts.
- 16. CONCLUSION Always stay alert and awake!!! Listen to radio/television for warnings of intense rainfall, storm and damp weather. These usually trigger landslides/debris or mudflow. ii) Do not cut down trees or remove vegetation or avoid slope weakening. If the house cannot be relocated, then ensure proper drainage and proper retaining walls. Make an evacuation plan in case of a landslide with all the emergency items.
- 17. • Help neighbours who may require special assistance– infants, elderly people and disabled people. • Listen to local radio/television stations for the latest emergency information. • Look for and report broken utility lines to appropriate authorities. • Check the building foundation, walls and surrounding land for damage. The safety of the areas needs to be assured before reoccupation. 17
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- 19. References ; • Landslide Hazard Manual (www.engineering4theworld.org/LAP) • Learning to live with landslides, Ministry of Education and National Institute of Education for Social Cohesion, Disaster Risk Management and Psycho-social Care, Srilanka. • Landslides Preparedness and Safety Measures, Department of Disaster Management, Bhutan. • Action Plan for Landslide Risk Mitigation, Ministry of Home Affairs , Office Memorandum, November 3, 2004, India.