LANDSLIDES

LANDSLIDES

Landslides are simply defined as the mass movement of rock, debris, or earth down a slope and have come to include a broad range of motions whereby falling, sliding, and flowing under the influence of gravity dislodges earth material.

LANDSLIDES IN INDIA

Landslide proneness in India (data and spatiality)

• In India, this hazard affects at least 15% of the land area of the country (approx 0.49 million square km).
• Landslides triggered by human activities are on the rise around the world, and India is among the most-affected countries, accounting for at least 28% of such events over the last 12 years.
• All countries in the top 10 for fatal landslides triggered by human activity are located in Asia. India accounts for 20% of these incidents.
• Landslides Vulnerability Zones:
  • Very high Vulnerability Zones:
    • The highly unstable and young mountainous area in the Himalayas and Andaman Nico bar region.
    • High rainfall with steeper slopes in Western Ghats and Nilgiri, and the North-Eastern States.
    • Areas with frequent ground shaking due to human activities and natural causes like earthquakes.
  • High Vulnerability zones:
    • Northeastern states except Assam plains.
    • Moderate to Low vulnerable zones:
      • Areas that receive less precipitation such as trans Himalayas Ladakh Spiti valley in Himachal Pradesh.
      • Low rainfall areas of Aravali.
      • Rainshadow zones of Western Ghats and the Eastern Ghats.
      • Landslides due to mining are common in the Chhotanagpur region, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Goa, Kerala.

Important landslide events

• Malpa landslide in Uttarakhand in August 1998.
• Kedarnath landslide in Uttarakhand in June 2013.
• Landslide in Idukki in Kerala in 2019.
• Landslide in Kodagu in Karnataka in August 2020.

CAUSES OF LANDSLIDES

Natural Causes:

• Geological Weak material: Weakness in the composition and structure of rock or soil may also cause landslides.
• Intense rainfall: Storms that produce intense rainfall for periods cause erosion of the slopes that trigger abundant landslides.
• Heavy melting of snow: In hilly terrains, this also results in landslides.

• Earthquake shaking has triggered landslides: In many different topographic and geologic settings.
• Volcanic eruption: Deposition of loose volcanic ash on hillsides commonly is followed by accelerated erosion and frequent mud or debris flows triggered by intense rainfall.

Man-made Causes:

• Mining, Quarrying, and Road cutting: The continuous extraction of coal, minerals, and stones from the mines and quarries and the development of roads by cutting the steep slopes in the folded mountains create conducive conditions for the occurrence of landslides.
  • For example: Observed throughout the Himalayas and in the Eastern and Western Ghats.
• Loading by the construction of houses: The unplanned growth of towns and cities in the hilly areas without testing soil and rocks is also an important cause of landslides.
  • For example: The eastern slope of Nainital (Uttarakhand) is sinking because of the heavy load of hotels and residential structures.
• Deforestation: Poorly planned forest clearing may increase rates of surface water run-off or groundwater.
• Wrong practices: Inefficient irrigation or sewage effluent disposal practices may result in increased ground-water pressures, which in turn can reduce the stability of rock and sediment.
• Shifting agriculture: In the Northeastern part of India, the number and frequency of landslides have increased due to the practice of shifting agriculture.

EFFECTS OF LANDSLIDES

Short-term:

• Loss of lives: Landslide in habited areas can cause massive loss to human lives.
  • For example: Kedarnath landslide in Uttarakhand in June 2013, caused by flash floods that resulted in over 5,000 deaths.
• Destruction of property: Especially in mountainous regions where houses are constructed on slopes.
  • For example: Landslides in Kerala (Idukki) have caused massive damage to life and property.
• Economic costs: Massive loss due to inundated buildings and post-disaster efforts has cost economically.
• Destruction of the natural environment: Debris flows usually uproot trees and wipe out vegetation and wildlife in its path.

Long-term:

• Changes in landscape: Landslides can potentially destroy forested tracts of land and also those under farming, further they can block river channels and cause flooding of lands.
• Loss of cultivable land: Lands under farming are destroyed once the top soil is covered from landslide debris.
• Soil erosion and soil loss: The tracts of land facing landslides lose their topsoil which may take many years to come back and in the meantime the land becomes barren and deforested.
• Relocation of population: Habitations around areas prone to landslides are often relocated and create an issue of environmental refugees.

Impact on Rivers:

• Diversion of river courses due to landslides can also lead to flooding and loss of life and property.
• Impede Transportation: Especially in mountainous regions, landslides can cut off critical road transport for many years at a time depending on the severity of the slide.

LANDSLIDE MANAGEMENT FRAMEWORK IN INDIA

1. NDMA Guidelines for Landslides

• Landslide Hazard, Vulnerability, and Risk Assessment.
• Multi-Hazard Conceptualisation.
• Landslide Remediation Practice.
• Research and Development, Monitoring, and Early Warning.
• Knowledge Network and Management.
• Capacity Building and Training.
• Public Awareness and Education.
• Emergency Preparedness and Response.
• Regulation and Enforcement.

2. Recent Government’s Measures

• Training programme: IIT Mandi in collaboration with NDMA conducted a five-day training program on ‘Landslide Mitigation and Detailed Project Report Preparation.’ 

• Aim: The training program aimed at creating awareness about the potential hazards and the various risk mitigation measures for landslides.

• National Landslide Susceptibility Mapping Programme: Under Pre-disaster studies, GSI has already formulated and carried out a National Landslide Susceptibility Mapping Programme on a macro-scale in various parts of the country, including NER and Sikkim.

3. Landslide Hazard Mitigation

• Adopt area-specific measures.
• Restriction on construction and other developmental activities such as roads and dams.
• Limiting agriculture to valleys and areas with moderate slopes.
• Control on the development of large settlements in the high vulnerability zones.
• Promoting large-scale afforestation programs.
• Construction of bunds to reduce the flow of water.
• It is always advisable to adopt area-specific measures.
• Hazard mapping should be done to locate areas commonly prone to landslides.
• Terrace farming should be encouraged in the northeastern hill states, replacing Jhuming or shifting cultivation measures to deal with landslides.
• Retaining walls can be built on mountain slopes to stop the land from slipping.

Challenges

• Technical/Scientific: Integrating landslide concerns in the development of disaster management plans at different levels, i.e., national, state, district, municipal/panchayat.
• Financial Issues: Criteria for disbursement of funds for servicing different areas of landslide mitigation.

Legal Issues:

• The techno-legal regime for the introduction of sound slope protection, planned urbanization, regulated land use, and environment-friendly land management practices.
• Zero tolerance against deliberate environmental violence and unhealthy construction practices.

Way Forward

• International Landslides Risk Reduction and Resilience Conference
  • Aim: To bring together all stakeholders, including relevant ministries, organizations, universities/departments, and experts, to discuss, debate, and disseminate practically useful knowledge, information, experiences, and innovations for landslides risk reduction and resilience at national and international levels.
  • The conference will develop a road map towards landslide risk reduction and resilience through networking, collaboration, and coordination among different stakeholders.
• Hazard mapping locates areas prone to slope failures: This will help to avoid building settlements in such areas. These maps will also serve as a tool for mitigation planning.
• Retaining Walls: Can be built to stop land from slipping (these walls are commonly seen along roads in hill stations).
• Surface Drainage Control Works: The surface drainage control works are implemented to control the movement of landslides accompanied by infiltration of rainwater and spring flows.
• Increasing vegetation cover: It is the cheapest and most effective way of arresting landslides. This helps to bind the top layer of the soil with layers below while preventing excessive run-off and soil erosion.
• Insurance: To assist individuals whose homes are likely to be damaged by landslides or by any other natural hazards.

Increasing human interference with nature has led to a rise in the number of natural disasters. However, the NDRF has conducted several successful rescue operations by providing aid and assistance to the affected state. They have also worked to increase awareness among people to reduce the effect of such natural calamities by organizing preparedness campaigns.