Wayanad landslides

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Context:  Over 100 people died, and hundreds are feared trapped after the landslides struck Chooralmala and Mundakkai villages in Wayanad district.

Details

The Phenomena 

• Landslides occur when gravity forcespushing on hill slope material exceed the frictional forces holding the material in place, causing slope failure. Landslide susceptibility represents this potential for slope failure. 

Occurrence Area

• Due to steep slopes and heavy rainfallmost of the landslides occur in the northwest Himalayas followed by the northeast Himalayas and the Western Ghats. 
• Approximately 42 million sq. km (12.6% of land area), excluding snow covered area, is prone to landslide hazard in India.

Types of landslides

Landslides in India are divided into four categories –

• Topples: This occurs due to fracture in rocks. It causes tilting for gravitational pull without collapsing.
• Falls: This involves the collapse of rocks or debris from a cliff or slope. It results in the collection of debris at the base of a hill.
• Spread: It occurs in gentle slopes where soft debris or other materials are widely available
• Slides: It occurs when debris, rocks or soil slide through a slope.

 Causes of Landslides

Landslides have three major causes: geology, morphology, and human activity.

• Geology refers to characteristics of the material itself.
• The earth or rock might be weak or fractured, or different layers may have different strength and stiffness.
• Morphology refers to the structure of the land. For example, slopes that lose their vegetation to fire or drought are more vulnerable to landslides.
• Vegetation holds soil in place, and without the root systems of trees, bushes, and other plants, the land is more likely to slide away.
• A classic morphological cause of landslides is erosion, or weakening of earth due to water.
• Tectonic or volcanic uplift.
• Human activity, such as agriculture and construction, can increase the risk of a landslide.
• Irrigation, deforestation, excavation, and water leakage are some of the common activities that can help destabilize, or weaken, a slope.

Landslide Prone Areas

 Impact

Immediate impact

• Loss and damage to property, loss of lives, Destruction to agricultural crops, Damages to Vegetation, Obstruction of vehicular movement, temporary loss of livelihood for the poor people etc.

Long term impact

• Increase in the sediment load of the river which can lead to floods.
• Reduce the effective life of hydroelectric and multipurpose projects by adding an enormous amount of silt load to the reservoirs.
• Loss of cultivable land and infrastructure.
• Environmental impact in terms of erosion and soil loss.
• Demographic impact in terms of relocation of population towards other areas.
• Frequent disruption of transportation networks leads to geographical isolation and hence perpetuates under-development.

Challenges in prediction

• Unlike other disasters that are largely controlled by macro or regional factors, landslides are largely controlled by highly localized factors.
• Hence, gathering information and monitoring the possibilities of landslide is so difficult and cost-intensive.
• Slopes often contain varied layers of rock and soil with different strengths. Mapping these materials in three dimensions is currently impossible with existing technology.

National Disaster Management Authority (Ndma) guidelines for The Management Of Landslides

• Hazard mapping: Pilot projects to be taken up in different regions of the country to carry out detailed studies and monitoring of selected landslides to assess their stability status and estimate risk.
• Early warning systems:The NDMA emphasizes the need for early warning systems that can provide alerts about impending landslides, allowing people to evacuate and take other precautionary measures.
• Land-use planning:Should be take into account the risks of landslides, and appropriate measures should be taken to minimize the risks.
• Slope stabilization: The construction of retaining walls or the use of vegetation to hold the soil in place.
• Preparedness measures: communities and organizations should develop and implement preparedness measures, including emergency response plans and training programs.Establishment of an autonomous national centre for landslide research, studies and management.

Initiatives

• National Landslide Susceptibility Mapping (NLSM) Programme: Launched in 2014-15, under it Geological Survey of India has completed landslide susceptibility mapping of 4.3 lakh sq. km. of landslide-prone areas in the country.
• The Landslide Risk Mitigation Scheme: to provide financial and technical support to landslide-prone states for site-specific landslide mitigation.
• Landslide-risk mitigation was highlighted in the National Disaster Management Plan of 2016.
• National Landslide Risk Management Strategy released by National Disaster Management Authority (NDMA): The strategy document brings out the message of the need to strengthen and mainstream landslide disaster preparedness, mitigation, response and relief mechanisms through
• Landslide Hazard Zonation: It covers aspects of reliability and validation of landslide zoning maps in the Indian scenario and proposes a plan of activities for landslide zoning.
• Landslide Atlas of India: The database covers landslide-vulnerable regions in 17 states and 2 UTs of India in the Himalayas and Western Ghats.
• IIT Delhi created the first hi-resolution Indian Landslide Susceptibility Map (ILSM).

Land slide in Wayanad

• According to the Kerala Disaster Management Authority’s landslide hazard profile map, over forty per cent of Wayanad district is susceptible to landslides.

Recent Land slide

Reason:

• Anthropogenic activity: Quarrying, hill levelling for construction, extensive road building, expansion in hilly areas, and mono-crop farming, extensive tourism infrastructure due to its proximity to the Meenmutti Waterfalls.
• Soil piping: This hydraulic process creates large air-filled voids in the subsurface, often associated with landslides and collapse subsidence. The recent landslides exhibit all the characteristics of soil piping.
• Peak monsoon: Rainwater seeps into the subsoil, loosening the connection between mud and rocks. This leads to landslides as water-soaked earth and large rocks tumble down.
• Climate change: Rainfall patterns in Kerala and the surrounding Western Ghats have drastically changed over the past six years.

What needs to be done

• Kerala must come up with a governmental policy for people in ecologically fragile areas prone to annual landslides and floods.
• There is a need to relocate and rehabilitate people from such areas.
• Micro-level landslide hazard mapping statewide must be urgently taken up.
• Urgent need for Kerala to establish clear land management and water utilisation policies.
• The state needs to have zoning regulations for land use, including “landslide susceptibility data”.

 Details about landslide: https://www.iasgyan.in/daily-current-affairs/bhusanket-web-portal 22 July 2024.

https://www.iasgyan.in/daily-current-affairs/landslide-risk-map-for-india

https://www.iasgyan.in/daily-current-affairs/landslides-47

https://www.iasgyan.in/daily-current-affairs/landslide-atlas-of-india

Sources:DowntoEarth.