Context: Indian Institute of Technology Delhi has made the first high-resolution landslide susceptibility map for India and the map data is available for free.

Background

• In late 2023, torrential rain during the northeast monsoon triggered heavy floods and landslides in multiple States in India, killing hundreds of people.

• It highlights the need for a national landslide susceptibility map to identify the most dangerous areas and help allocate resources for mitigation strategies better. 

About Landslide Susceptibility Map

• The team from IIT Delhi built a national landslide susceptibility map that uses the latest data and data collection and mapping techniques. 

• High Resolution: The map, could plot the susceptibility at a resolution of 100 m. 

• Identified Region: The map acknowledged some high landslide susceptibility, like parts of the foothills of the Himalayas, the Assam-Meghalaya region, and the Western Ghats. 

• New Insight: It also revealed some previously unknown places with high risk, such as some areas of the Eastern Ghats, north of Andhra Pradesh.

Uniqueness of Landslide Challenges in India

• Data Challenges: Unlike floods, landslides in India are more localized and affect only about 1-2% of the country. Tracking and studying them is difficult due to the scarcity of high-quality data.

The Research Approach

• Data Collection: Graduate students collected data on nearly 1.5 lakh landslide events from sources including the Geological Survey of India (GSI) and other global databases.

• Factors Considered: Sixteen landslide conditioning factors were identified, including soil cover, tree density, and proximity to roads or mountains.

Technology and Machine Learning

• Utilizing Latest Techniques: The research aimed to not only use available data but also incorporate state-of-the-art techniques.

• Ensemble Machine Learning: Using ensemble machine learning methods, the researchers analyzed 150,000 data points for known landslide events and the 16 identified factors.

Developing the National Landslide Susceptibility Map

• Resolution and Coverage: The resulting high-resolution map, named the 'Indian Landslide Susceptibility Map,' covered the entire country with a resolution of 100 m, estimating susceptibility for each 100 sq. m parcel.

Identifying High-Risk Areas

• Known and Unknown Susceptibility: The map confirmed known high-risk regions like the Himalayan foothills but also revealed previously unknown vulnerable areas, such as parts of the Eastern Ghats.

• Policy Implications: The map is expected to assist policymakers in assessing vulnerability and formulating effective mitigation measures.

Future Initiatives

• Early Warning System: Building on the map, the researchers aim to develop a 'Landslide Early Warning System' for India.

• Infrastructure Vulnerability Map: In addition to the landslide map, efforts are underway to create an infrastructure vulnerability map depicting areas susceptible to landslides.

Public Accessibility

• Online Availability: The map is available online for public access, providing a user-friendly interface for exploring regions of interest.

• Community Engagement: Encouraging people to utilize the data, the researchers emphasize the map's accessibility without requiring technical knowledge.

About Landslides

• Definition of Landslide: It is a movement of a mass of rock, earth or debris down a slope. 

• Landslide Prone Regions: The regions with fewer trees, closer to road-building activity, and steeper local slopes are more unstable and prone to landslides.

• Causes: They can occur on many types of terrain given the right conditions of soil, rock, geological structure, drainage and slope.

• Natural Causes: Rainfall, undercutting of slopes due to flooding or excavation, earthquakes, snowmelt etc. 

• Anthropogenic Causes: Overgrazing by cattle, terrain cutting and filling, excessive development, etc. 

• For example, land use changes lead to deforestation and exposure of slopes cut for the development of a key railway project likely contributed to a deadly landslide in the  western Manipur in 2022.

Types of Flows

• Debris Flow: It is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, and slurry flows downslope. They are commonly caused by intense precipitation or rapid snow melt. 

• Earth Flow: It is a downslope viscous flow of fine-grained material saturated with water. 

• Mudflow: A mudflow is a wet or viscous fluid mass of fine and coarse-grained material that flows rapidly along drainage channels. 

• Creep: Creep is the slow, steady, downward movement of material under gravity that occurs in a large area.

Road Ahead

• The creation of India's first national landslide susceptibility map represents a significant leap in understanding and addressing the unique challenges posed by landslides.

• With applications ranging from early warning systems to infrastructure planning, the map is poised to play a crucial role in mitigating the impact of landslides across the country.