Landslide: Landslide R.Jayashree Definition: Definition Landslides are the mass movement of rock, debris or earth ,down a slope ,under the influence of gravity which dislodges earth material. They often take place in conjunction with earthquakes, floods and volcanoes. Slide 3: The land slides caused after a prolonged rainfall may even block the flow of rivers and thereby cause havoc to the settlements downstream on it's bursting. Morphological Causes : Morphological Causes Ground uplift -(volcanic, tectonic etc) Erosion -(wind, water) Deposition loading in the slope crest. Vegetation removal -(by forest fire, drought etc) Natural causes of landslides: Natural causes of landslides Groundwater pressure Loss or absence of vertical vegetative structure Erosion of the toe of a slope Weakening of a slope by glaciers melting, or heavy rains Earthquakes Volcanic eruptions Human causes: Human causes Deforestation - Construction Vibrations from machinery or traffic Blasting, Mining Earthwork which alters the shape of a slope. In shallow soils, the removal of deep-rooted vegetation . Agricultural or forestry activities. Types of Landslides: Types of Landslides Debris flow Earth flow Debris avalanche Sturzstrom Shallow landslide Deep-seated landslide 1. Debris flow: 1. Debris flow Slope material becomes saturated with water. Slurry of rock and mud may pick up trees, houses and cars, thus blocking bridges and tributaries causing flooding along its path. Amboori debris flow, occurred on 9 November 2001 in Kerala, India. The event killed 39 people. [1 Damages caused due to Debris flow: Damages caused due to Debris flow Interruptions due to deposits Complete removal of bridges or roadways or railways -Uganda (Bududa)-2010- 400+ deaths, 200,000 displaced -Brazil (city of Rio De Janeiro)-2010, 350 deaths, 61 houses destroyed Both these were caused due to heavy rainfall 2. Earth flow : 2. Earth flow Viscous flows of saturated, fine-grained materials,. Can move at speeds from 0.17 to 20 km/h. Clay, fine sand and silt, and fine-grained are all susceptible to earth flows. 3.Debris avalanche : 3.Debris avalanche Characterized by the chaotic movement of rocks soil and debris mixed with water or ice (or both). Triggered by the saturation of thickly vegetated slopes which results in mixture of broken timber, smaller vegetation and other debris. Goodell Creek Debris Avalanche, Washington 4.Sturzstrom : 4.Sturzstrom Unusually mobile, flowing very far over a low angle, flat, or even slightly uphill terrain. Actual cause of this is not understood. 5. Shallow landslide : 5. Shallow landslide 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). 6.Deep-seated landslide : 6.Deep-seated landslide The sliding surface is mostly deeply located below the maximum rooting depth of trees. This involves deep regolith, weathered rock, and/or bedrock and include large slope failure associated with translational, rotational, or complex movement Under sea landslides: Under sea landslides Generate tsunamis. In 1958, one such tsunami occurred in Lituya Bay in Alaska. Slide 17: Region Incidences of Landslides Himalayas High to very high North-eastern Hills High Western Ghats and the Nilgiris Moderate to high Regions most vulnerable to landslides in India: Regions most vulnerable to landslides i n India The Himalayas mountain - tectonically unstable younger geological formations. The Western Ghats and Nilgiris are geologically stable but have uplifted plateau margins influenced by neo- tectonic activity. Slide 19: 24 September -2003 Varunavat Parvat,Uttarkashi , 3,000 people -loss of property worth Rs. 50 crore . 5 July 2004 Badrinath , Chamoli District, Uttarakhand -cloudburst triggered massive landslides -16 persons killed, 200 odd pilgrims stranded 14 August2007 Dharla Village, H.P. -Burial of the entire village. Major disaster :
Major disaster In 2005
& India -Kashmir earthquake, Magnitude 7.6 -Total deaths was 25,500. -Blocked 2 tributaries of the Jhelum river - buried a village,.
Landslide Hazard Mitigation:: Landslide Hazard Mitigation: A National Core Group Chairman-Secretary, Border Management Members- Secretaries of Department of Science and Technology, Road Transport & Highways -Heads of Geological Survey of India - National Remote Sensing Agency for drawing up a strategy and plan of action for mitigating the impact of landslides. Landslide Warning Signs: Landslide Warning Signs Springs, seeps, or saturated ground New cracks or unusual bulges Soil moving away from foundations. Tilting of ancillary structures Cracking of concrete floors and foundations. Landslide Warning Signs-Contd.: Broken water lines and other underground utilities. Leaning telephone poles, trees, retaining walls or fences. Sunken or down-dropped road beds. Rapid increase or Sudden decrease in water levels in ponds, accompanied by increased turbidity (soil content). Landslide Warning Signs-Contd. Unusual sounds, such as trees cracking or boulders knocking. Landslide hazard mapping: Landslide hazard mapping GIS is an appropriate tool Remote sensing techniques Before and after aerial photographs and satellite imagery Precautions: Precautions Do not build near steep slopes. Get a ground assessment of your property. Contact concerned departments/ professional referral for information on landslides. Cautious when there is any abnormality in the flow of storm water drains Slide 26: Minimize hazards: Have flexible pipe fittings installed to avoid gas or water leaks. Plant ground cover on slopes and build retaining walls. In mudflow areas, build channels or deflection walls to direct the flow around buildings. During a Storm/Landslide : During a Storm/Landslide Stay alert and awake. Listen for warnings. Live away from areas susceptible to landslides. Avoid driving during an intense storm. Listen for any unusual sounds that might indicate moving debris. If you are near a stream or channel, be alert for any sudden increase or decrease in water flow and for a change from clear to muddy water. What to Do if You Suspect Imminent Landslide Danger: What to Do if You Suspect Imminent Landslide Danger Contact your local fire, police, or public works department. Evacuate. Inform affected neighbors & Help neighbors to evacuate. Curl into a tight ball and protect your head if escape is not possible. After a Landslide : After a Landslide Stay away from the slide area. There may be danger of additional slides. Listen to local radio or television stations for the latest emergency information. Floods sometimes follow landslides and debris flows. Check for injured and trapped persons near the area. Elderly people and people with disabilities may require additional assistance. References: References http://landslides.usgs.gov/learning/majorls.php http://www.vliz.be/imisdocs/publications/35254.pdf . http://www.ndmindia.nic.in Slide 32: Computer simulation of a "slump" landslide in San Mateo County , California (USA) in January 1997 Thank you