Recently, More than 50 people were killed after landslides swept through tea estates and homes in Kerala

What is Landslide?

• Landslides: Sudden movement of rock, boulders, earth or debris down a slope is termed a landslide.
• Factor: When the pull from gravity exceeds the strength of the geomaterial forming the slope of a hill or mountain.

Reason for Landslides – Human Pressure

• Due to Natural Factors: Occurs mainly in mountainous terrains where there are conducive conditions of soil, rock, geology and slope. 
  • Natural causes that trigger it include heavy rainfall, earthquakes, snow melting and undercutting of slopes due to flooding. 
• Due to the Anthropogenic activities:  Such as excavation, cutting of hills and trees, excessive infrastructure development, and overgrazing by cattle
  • Excess Load: The risk from landslides has been exacerbated by the failure to remain mindful of the terrain’s ability to withstand the load.
  • Lack of Regulations: Many hilly areas do not have building regulations. Often, regulations are not implemented effectively.
  • Construction and Development: New constructions, infrastructure development, and even agricultural practices can increase the risk of landslides.
  • Exceeding Carrying Capacity: Every mountainous area has a carrying capacity. Development is essential, and one cannot stop the creation of infrastructure or new facilities or economic activity for local populations.
    • But these have to be regulated. Sustainability has to be factored in, so that the load does not exceed the carrying capacity.
    • This is where zoning regulations come in. These have to be finalised and implemented strictly.

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Landslide Concerns & Vulnerability

India is among the top five landslide-prone countries globally, where at least one death per 100 sq km is reported in a year due to a landslide event.

• According to the Geological Survey of India (GSI), About 0.42 million square km of India’s landmass, or about 13% of its area, spread over 15 states and four Union Territories, is prone to landslides 
• This covers almost all the hilly regions in the country. 
  • North Eastern States: About 0.18 million square km, or 42% of this vulnerable area is in the Northeastern region, where the terrain is mostly hilly.
  • Between 2015 and 2022, the eight states in this region, including Sikkim, recorded 378 major landslide events which resulted in loss of life or damage to property. 
• These events constituted 10% of all major landslides in India during this period.
• In the country as a whole, Kerala saw the largest number of landslides 2,239 most of which occurred after the disastrous 2018 floods in the state. 

Why is it difficult to predict landslides?

• Complexity of Geomaterials: Underneath the ground, geomaterials consist of multiple, intertwined layers of various rocks and particulate materials like sand, silt, and clays. 
  • Their strength can vary significantly, from a factor of one to 1,000, and their spatial distribution influences slope stability.
• Incomplete Data and Uncertainty: Accurate slope stability assessment necessitates three-dimensional mapping of these materials and their strengths. 
  • No sensor can provide this comprehensive information that forces geologists and geotechnical engineers to rely on partial data from select locations and extrapolate it to the entire slope.
• Runout Distance and Safe Zones:  While it is known that larger landslides have longer runout distances, predicting the exact size of a landslide is difficult, making the determination of runout distances and safe zones uncertain. 
• Timing of Landslides: To Determine when a landslide will occur is also uncertain. 
  • Only Mechanical analysis can estimate the vulnerability of a slope under specific scenarios, including earthquake magnitude and groundwater distribution. 
  • However, To predicate the timing of these triggers is as challenging as predicting weather and seismic activity.

Anthropogenic Reasons for Extreme Weather Conditions in India: 

1. Greenhouse Gas Emissions:

• Burning of Fossil Fuels: The combustion of coal, oil, and natural gas for energy and transportation releases large amounts of carbon dioxide (CO2) and other greenhouse gases (GHGs) into the atmosphere.
• Industrial Activities: Manufacturing and industrial processes contribute significantly to GHG emissions.
• Effect: 
  • Glacial Lake Outburst Floods: GLOF events have increased due to rising global temperatures as Warmer temperatures can weaken the ice or sediment barriers holding back the water, making them more susceptible to breaking.
    • According to a 2021 study titled ‘Locked Houses, Fallow Lands: Climate Change and Migration in Uttarakhand, India’: The hill’s annual average maximum temperature may increase by 1.6-1.9 degrees Celsius.
    • This temperature rise is projected to occur between the years 2021 and 2050.
  • Heatwave: For every region, a heatwave is determined based on the degree of difference from its usual temperatures. 

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2. Deforestation and Land Use Changes:

• Deforestation: The clearing of forests for agriculture, urban development, and logging reduces the Earth’s capacity to absorb CO2, exacerbating global warming.
• Agricultural Practices: Intensive farming practices, including the use of synthetic fertilizers and pesticides, contribute to nitrous oxide emissions, a potent greenhouse gas.
• Effect:
  • Flooding: Loss of natural vegetation and increased impervious surfaces hinder infiltration, causing rapid runoff and overwhelming drainage system
  • Example:  According to the ICED 2022 report, the country has experienced a significant increase in annual runoff by approximately 1.3 billion cubic meters due to reduced infiltration and increased surface runoff.

3. Urbanization:

• Urban Heat Islands: Rapid urbanization leads to the creation of heat islands, where concrete and asphalt absorb and re-radiate heat, increasing local temperatures.
• Water Management: Poor urban planning and inadequate drainage systems exacerbate the impacts of heavy rainfall, leading to urban flooding.
• Effect: 
  • Flooding: The major cause of frequent urban floods is unplanned urbanization. 
    • The State of Kerala, Madhya Pradesh, Karnataka, Maharashtra and Gujarat were the most severely affected. 

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4. Industrial and Agricultural Pollution:

• Air Pollution: Emissions from industries, vehicles, and agricultural burning contribute to air pollution, which can influence weather patterns and increase the severity of weather events.
• Water Pollution: Industrial discharge and agricultural runoff contaminate water bodies, affecting the hydrological cycle and contributing to extreme weather events.

5. Unsustainable Water Management

• Overextraction of Groundwater: Excessive extraction of groundwater for agriculture and domestic use can lead to depletion of water tables, contributing to drought conditions.
• Inefficient Irrigation: Traditional and inefficient irrigation practices lead to water wastage and reduced resilience to droughts.

Way Forward: Mitigating and Adapting to Extreme Weather Conditions

• Urban Planning and Infrastructure Development:
  • Resilient Infrastructure: Build and upgrade infrastructure to withstand extreme weather events, such as flood-resistant buildings and efficient drainage systems.
  • Green Spaces: Incorporate green spaces and urban forests to mitigate the urban heat island effect.
• Water Resource Management:
  • Integrated Water Management: Implement integrated water resource management practices that ensure the sustainable use of water resources.
  • Rainwater Harvesting: Promote rainwater harvesting and groundwater recharge to enhance water availability during dry periods.
• Disaster Preparedness and Response:
  • Early Warning Systems: Develop and deploy early warning systems for floods, cyclones, and droughts to enhance preparedness and minimize damage.
  • Community-Based Approaches: Empower local communities with the knowledge and tools to respond effectively to extreme weather events.
• For Glacial Lake Outburst: 
  • Controlled Breaching of Moraine Dam: Intentional Breaching of moraine dam controls water release from the glocal lake. 
  • Construction of Outlet Control Structure: This technique includes building an outlet control structure. This structure helps to regulate water and controls water release. 
  • Pumping or Siphoning Water: Using pumps to reduce water helps to control water volume. In this way, it reduces hydrostatic pressure on the moraine dam which further reduces GLOF event. 
  • Tunnelling Through Moraine Barrier or Under Ice Dam: This technique provides an alternative path for water to flow, leading to reduction in sudden outburst of GLOF events. 

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