Landslides
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Content
Introduction
Landslide is defined as the movement of a mass of rock, debris or earth down a slope. This is a type of mass wasting, which denotes any down-slope movement of soil rocks under the direct
influence of gravity.
- The term “landslide” encompasses five modes of slope movement: Falls, topples, slides, spreads, and flows.
- There are two landslide hotspots that exist in India – along the southern edge of the Himalayan arc and the Western Ghats region.
Key causes of landslides:
- Himalayas are prone to landslides because of several morphological and geological factors like:
- Tectonic movement
- Glacial movements
- Freeze and thaw effect
- Unstable rock structure
- Steep slopes etc.
- Most regions with more than 20 degrees are prone to landslides.
- Types of rocks, weaknesses, zone of rupture etc.
Destabilizing Geological Processes – Soil Piping, Land Subsidence, Lateral Spread etc. But in recent years, we have also seen the stable Peninsular Hills like in Western Ghats becoming vulnerable because of the human made factors.
Human Induced Causes
- Climate Change: Extreme Rainfall Events trigger slope failure where lateral spread and soil
piping have occurred.- For instance, unusually high rainfall in Kerala since Aug 2018 has destabilized the already vulnerable hill slopes in the high ranges and has caused many landslides.
- Illegal Mining, deforestation etc have made the surface weak and vulnerable to landslides
- For e.g. the railways have blamed two successive land slides along their project site in Manipur on the traditional practice of Jhum or shifting cultivation.
- Unscientific Farming and Construction Activities
- UNDP’s assessment after the 2018 flood says that changes in land cover, blocking of natural drains, and poor agricultural practices such as monocropping have all exacerbated the risk of landslides in Kerala.
- Since 19th century, 50% of the land with tropical forests and grasslands has been converted to monoculture plantations and agricultural fields.
- Illegal landgrab using fake deeds have contributed to unscientific land use and thus landslides.
- Inadequate Early Warning Systems makes the impact of the disaster worse.
Government Efforts and Way Forward
- A national landslide susceptibility map has been created by Geological Survey of India (GSI) under the National Landslide Susceptibility Mapping Project. This national landslide susceptibility map should be integrated with infrastructure development and planning in hilly areas.
- Union Ministry of Earth Science has also initiated steps to establish a network of landslip monitoring stations in the highlands.
- The units which will be based on acoustic emission technology will also have an early warning mechanism to alert the local community.
- NDMA guidelines for management of Landslides
- Inventorization and regular update
- Landslide Susceptibility Map at macro and meso scales
- Awareness Generation and preparedness among various stakeholders through setting up of institutional mechanisms.
- Capacity Building to deal with Landslides
- Enhancing education and training of professionals involved in landslides management.
- Capacity development of organizations working in the field of landslides
- Create an Autonomous National Centre for landslide studies research and management.
- Other steps that can be taken
- Deploy Early Warning Systems based on rainfall thresholds in various vulnerable regions.
- Note: In way forward also suggest things like increase afforestation, banning of mining in sensitive areas, sustainable forms of agriculture etc.
Example Questions
- While the Himalayan region was always vulnerable to landslides, the recent years have seen the peninsular hills also becoming increasingly prone to this natural disaster. Give reasons. What are the NDMA guidelines for management of landslides? [15 marks, 250 words]