CAUSES AND EFFECTS OF LANDSLIDES

The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failure
A landslide is the movement of rock, earth, or debris down a sloped section of land. Landslides are caused by rain, earthquakes, volcanoes, or other factors that make the slope unstable. s, mudflows and debris flows

1. Disaster management TOPIC- CAUSES AND EFFECTS OF LANDSLIDES NAME- NITHIN KALLEPALLY

2. What Is A Landslide? The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failure A landslide is the movement of rock, earth, or debris down a sloped section of land. Landslides are caused by rain, earthquakes, volcanoes, or other factors that make the slope unstable. s, mudflows and debris flows

3. CAUSES OF LANDSLIDES While landslides are considered naturally occurring disasters, human-induced changes in the environment have recently caused their upsurge. Although the causes of landslides are wide ranging, they have 2 aspects in common; they are driven by forces of gravity and result from failure of soil and rock materials that constitute the hill slope:

4. NATURAL CAUSES OF LANDSLIDES CLIMATE - Long-term climatic changes can significantly impact soil stability. A general reduction in precipitation leads to lowering of water table and reduction in overall weight of soil mass, reduced solution of materials and less powerful freeze-thaw activity. A significant upsurge in precipitation or ground saturation would dramatically increase the level of ground water. When sloped areas are completely saturated with water, landslides can occur. If there is absence of mechanical root support, the soils start to run off. EARTHQUAKES - Seismic activities have, for a long time, contributed to landslides across the globe. Any moment tectonic plates move, the soil covering them also moves along. When earthquakes strike areas with steep slopes, on numerous occasion, the soil slips leading to landslides. In addition, ashen debris flows instigated by earthquakes could also cause mass soil movement

5. WEATHERING Weathering is the natural procedure of rock deterioration that leads to weak, landslide-susceptive materials. Weathering is brought about by the chemical action of water, air, plants and bacteria. When the rocks are weak enough, they slip away causing landslides

6. VOLCANIC ERUPTIONS - Volcanic eruptions can trigger landslides. If an eruption occurs in a wet condition, the soil will start to move downhill instigating a landslide. Stratovolcano is a typical example of volcano responsible for most landslides across the globe. EROSION - Erosion caused by sporadic running water such as streams, rivers, wind, currents, ice and waves wipes out latent and lateral slope support enabling landslides to occur easily due to heavy rainfalls and excessive deforestation .

7. FOREST FIRES - Forest fires instigate soil erosion and bring about floods, which might lead to landslides Forest fires occurring naturally or due to human errors could lead to this landslides GRAVITY - Steeper slopes coupled with gravitational force can trigger a massive landslide. The downward attraction of earth pulls down the weak layers of the soil on a mountain or hill which causes the landslides

8. HUMAN CAUSES OF LANDSLIDES MINING - Mining activities that utilize blasting techniques contribute mightily to landslides. Vibrations emanating from the blasts can weaken soils in other areas susceptible to landslides. The weakening of soil means a landslide can occur anytime. DEFORESTRATION – Deforestation is the permanent removal of trees to make room for something besides forest. This can include clearing the land for agriculture or grazing, or using the timber for fuel, construction or manufacturing.  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

9. Change in slope/land use pattern, deforestation, agricultural practices on steep slopes: contributed to creep and withdrawal of toe support in many cases COMBINATION OF FACTORS : For example, an earthquake may trigger a landslide, which in turn may dam a valley causing upstream flooding and subsequent dam burst. This will lead to flooding in lower catchments areas . OTHER FACTORS - building roads and structures without adequate grading of slopes, poorly planned alteration of drainage patterns, and disturbing old landslides And many more human errors….

10. EFFECTS OF LANDSLIDES Landslides have affected both the human beings as well as the wild life 'adversely. Every year there are reports of casualties of humans and animals and destruction of human property worth crores of rupees. This has disturbed the normal life of people. The magnitude of the damages caused by these hazards every year is very large and it becomes costlier to overcome these problems. The study of the impact of landslides on man and nature in the study district is important as human interference with nature becomes more pronounced during the last decade

11. EFFECTS OF LANDSLIDES LEAD TO ECONOMIC DECLINE - Landslides have been verified to result in destruction of property. If the landslide is significant, it could drain the economy of the region or country. After a landslide, the area affected normally undergoes rehabilitation. This rehabilitation involves massive capital outlay. For example, the 1983 landslide at Utah in the United States resulted in rehabilitation cost of about $500 million. The annual loss as a result of landslides in U.S. stands at an estimated $1.5 billion. LOSS OF LIFE - Communities living at the foot of hills and mountains are at a greater risk of death by landslides. A substantial landslide carries along huge rocks, heavy debris and heavy soil with it. This kind of landslide has the capacity to kills lots of people on impact. For instance, Landslides in the UK that happened a few years ago caused rotation of debris that destroyed a school and killed over 144 people including 116 school children aged between 7 and 10 years. In a separate event, NBC News reported a death toll of 21 people in the March 22, 2014, landslide in Oso, Washington.

12. DECIMATION OF INFRASTRUCTURE The force flow of mud, debris, and rocks as a result of a landslide can cause serious damage to property. Infrastructure such as roads, railways, leisure destinations, buildings and communication systems can be decimated by a single landslide AFFECTS BEAUTY OF LANDSCAPES The erosion left behind by landslides leaves behind rugged landscapes that are unsightly. The pile of soil, rock and debris downhill can cover land utilized by the community for agricultural or social purposes.

13. IMPACT ON ECOSYSTEM - The soil, debris, and rock sliding downhill can find way into rivers and block their natural flow. Many river habitats like fish can die due to interference of natural flow of water. Communities depending on the river water for household activities and irrigation will suffer if flow of water is blocked. 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 . Geological Factors - Many slides occur in a geologic setting that places permeable sands and gravels above impermeable layers of silt and clay, or bedrock. Water seeps downward through the upper materials and accumulates on the top of the underlying units, forming a zone of weakness

14. OTHER CONSEQUENCES - 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. The negative economic effects of landslides include the cost to repair structures, loss of property value, disruption of transportation routes, medical costs in the event of injury, and indirect costs, such as lost timber and fish stocks. Water availability, quantity, and quality can be affected by landslides. Geotechnical studies and engineering projects to assess and stabilize potentially dangerous sites can be costly.

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