Landslides

Landslides are a significant natural disaster in India, causing loss of life as well as damage to communication lines, human settlements, agricultural areas, and forest regions.

• The Himalayas and Western Ghats regions of India are particularly vulnerable to landslides
•   Since the Himalayas are the youngest and most powerful mountains in the world, it is estimated that only about 30% of the world’s landslides occur in the Himalayas

Consequences and Control of Landslides

• At the base of the slopes, landslides are triggered by the action of water induced by heavy rainfall or snowfall, excess groundwater, and other factors.The downward movement of soil and rocks on slopes is caused by fractures across thin layers, especially with high shear stresses associated with these landslides
• Roadblocks in steep and mountainous areas obstruct normal communication, tourism, and the delivery of daily necessities
• The expense of rebuilding roads and embankments is extremely high. Current projects are also delayed, resulting in significant cost and time overruns.Dams built in hills can break down and flood the plains
• It has a negative influence on the environment and biodiversity, which takes a long time to recover from
• Landslides can bypass river waterways, causing floods and  loss of life and property
• Example: In India, a landslide in Uttarakhand killed 5,700 people in 2013. This is the fifth highest number of landslide deaths in the world. Flash floods and landslides in Ladakh  2010 are another example   

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Landslide Prevention and Mitigation

• In landslide-prone locations, regulations and restrictions on construction and other developmental activities such as roads and dams are in place, with cultivation restricted to valleys and places with moderate slopes
• The growth of large settlements in high-vulnerability zones should be strictly regulated
• Promoting large-scale afforestation programmes and the construction of water-control bunds
• Encourage terrace farming in the northeastern hill states, where Jhum (Slash and Burn/Shifting Cultivation) is still widely practised. Installing protective covers over the sensitive zone, such as metal meshes

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•   Other measures:

 Structural measures:

Planting (Avalanche Prevention Forest): They prevent the movement of avalanches due to the resistance of tree trunks and branches, increase the stability of the  snow cover due to their uniform distribution, and control sudden changes in the avalanches.

Stepped Terraces: These help in stabilising the snow cover. Stepped terraces are easy to construct but are not effective in controlling surface layer avalanches.

Avalanche Control Piles: Avalanche control piles are a collection of single piles driven into the slopes in the avalanche zones  to control surface layer avalanches. The distance between the piles depends on the type of snow or the topographical features. The average distance is about 5 metres.

Avalanche Control Fence: Avalanche Control Fence is installed on slopes of avalanche zones to prevent full depth or surface layer avalanches.

Suspended Fences: Suspended fences are used in steep slopes or in areas where foundations cannot be properly installed because of poor ground conditions. These are useful in small area.

Snow Cornice Control Structures: These structures are installed at tops of mountain areas to prevent the development of snow cornices that can cause avalanches.

Stopping, deflecting, and retarding structures are examples of protection structures.

• Non-structural measures include blasting snow off slopes, anticipating avalanches, and evacuating people from dangerous places
• The launch of the ‘National Landslide Risk Mitigation Project’ (NLRMP) has been planned
• This project seeks to improve structural and non-structural landslide mitigation efforts, reducing landslide risk and susceptibility in hilly areas prone to landslides and mudflows, and reducing the dangers associated with landslide disasters
• Use of technology- Emergency response equipment, geological reconnaissance of landslide-prone areas, local monitoring services, site investigation with boring and test pits, slope stability analyses, seismic analysis of slopes, technical assistance in the construction of buildings, roads, pipes, and other structures, drainage system design assistance, and erosion modelling etc.

NDMA Guidelines on Landslides

•   The country’s landslide storage inventory should be updated on a regular basis
•   Mapping of landslide hazard zones at the macro and meso dimensions, in collaboration with the Border Roads Organisation (BRO), state governments, and local populations
•   Pilot projects will be carried out around the country in various regions for extensive study, monitoring, and assessment of the stability status and associated risk
•   Establishing institutional structures to raise awareness and preparation among various stakeholders

•   Setting up early warning systems based on the cost-benefit ratio and risk assessment as a result of the slide
•   Professionals and organisations engaged in the subject of landslide management might benefit from training and capacity building. Existing landslide courts and guidelines will be amended, and new codes should be formed
•   To help and provide scientific guidance and interventions for managing the occurrence of landslides, an autonomous centre for research and study in landslide management will be established

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Recent technological advancements include:

•   Amrita Vishwa Vidyapeeth established a wireless sensor-based landslide detection system in the Western Ghats of Kerala in 2009, which has delivered multiple successful warnings
•   The same institution took on the second project in Sikkim in 2018, installing sensors in an area encompassing roughly 150 acres of Chandmari, a heavily inhabited village in the Gangtok district

Hazard Zone Mapping

•   Landslide Hazard Zone maps were created for some of the country’s pilgrim routes. Geological, topological, and anthropogenic elements are used to define these zones. Lithology, soil, slope, drainage, lineament, land use, and other characteristics are among them
•   Currently, pilgrimage routes in Himachal Pradesh, Uttarakhand and Meghalaya can be found on these maps. In addition, landslide inventory is carried out from event to event and from season to season. The data on landslide inventory and hazard zones assists decision-makers in making better decisions in these regions

Conclusion

Landslide is a major natural disaster which causes loss of life, property and infrastructure. Landslide is generally referred to as the sudden moment of rock mass and Debris due to gravitation. It can be natural as well as manmade. Loss of life, agriculture, forest, human property, communication lines etc are major ill effects of it. Landslides  depend on the geological, topographical and climatic factors. Regions with steep slopes, high precipitation, devoid of vegetation, etc are more prone to landslides. For  effective handling of landslides, the hazard zone mapping must be done regularly. Adequate  prevention and mitigation measures help to reduce the damage of landslides. Regulated construction, afforestation, terrace farming,  fences, usage of Geographical information systems, etc will help to mitigate and prevent us from landslides.