[Note: Answer is elaborately explained as “Landslides” is a very important and repeating topic in UPSC exam ]
INTRODUCTION:
A landslide is defined as the movement of a mass of rock, debris, or earth down a slope. Landslides are a type of “mass wasting,” which denotes any down-slope movement of soil and rock under the direct influence of gravity.
The term “landslide” encompasses five modes of slope movement: falls, topples, slides, spreads, and flows.
Natural Causes of Landslides
1. 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.
2. 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 occasions, the soil slips leading to landslides. In addition, ashen debris flows instigated by earthquakes could also cause mass soil movement.
3. 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.
4. 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.
5. Volcanoes: 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 a volcano responsible for most landslides across the globe.
6. Forest fires: Forest fires instigate soil erosion and bring about floods, which might lead to landslides
7. Gravity: Steeper slopes coupled with gravitational force can trigger a massive landslide.
Human causes of landslides
7. 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.
8. Clear cutting: Clear cutting is a technique of timber harvesting that eliminates all old trees from the area. This technique is dangerous since it decimates the existing mechanical root structure of the area.
Effects of Landslides
1. 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.The annual loss as a result of landslides in the U.S. stands at an estimated $1.5 billion.
2. 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.
3. 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 kill lots of people on impact.
4. 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 utilised by the community for agricultural or social purposes.
5. Impacts river ecosystems: 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.
Important components of the National Landslide Risk Management strategy
1. Generation of User-Friendly Landslide Hazard Maps
2. Development of Landslide Monitoring and Early Warning System
3. Awareness Programmes
4. Capacity Building and Training of Stakeholders
5. Preparation of Mountain Zone Regulations & Policies
6. Stabilisation and Mitigation of Landslides and Creation of Special Purpose Vehicle (SPV) for Landslide Management.
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