IIT Delhi team makes first hi-res landslide risk map for India.

Landslide Susceptibility

• Landslide susceptibility is the likelihood of a landslide occurrence in an area depend on the terrain condition.
• It is an estimate of where landslides will have occurred.
• Relative susceptibility to land sliding is used as a measure of the potential hazard within an area.
• It is applicable to regions with different geomorphologic and vegetation characteristics.

National Landslide Susceptibility Mapping (NLSM) programme

• Geological Survey of India has launched and undertook a national programme on landslide susceptibility mapping with an aim to cover the 0.42 million sq. km landslide prone areas of the country.
• This national programme was formally launched in 2014.
• Objectives - To create a dynamic National Landslide Susceptibility Geodatabase for India.
• To prepare GIS based seamless Landslide Susceptibility Maps of India on 1:50,000 scale.
• To prepare a nation-wide repository on GIS-based Landslide Inventory.

The Map

• A landslide susceptibility map identifies areas which are subject to landslides and is measured from low to high.

Landslides are a unique and deadly problem in India and unlike floods, they are less widespread and harder to track and study with satellites.

• The landslide susceptibility map takes into account where the landslides occur and what causes them (slope, soil type and the impact of the flow of water in an area).

The Indian Landslide Susceptibility Map is the first of its kind by virtue of being on a national scale, leaving out no locations in the country.

• Process - Nearly 1.5 lakh landslide events were obtained via the Geological Survey of India (GSI) and other, global sources.
• GeoSadak, an online system that has data on the national road network in India, was particularly helpful in preparing the map, because it displayed data on roads even outside cities.

The fewer trees there are in a place, the closer it is to road-building activity, and the steeper the local slope, the more unstable the place will be and thus more prone to landslides.

• Applications - The map will help the policymakers to assess vulnerability and take appropriate measures for mitigation.
• The map is also expected to be useful for organisations involved in investigating and mitigating landslides, like the GSI, the Ministry of Mines, and the National Disaster Management Authority.
• High risk regions - The map acknowledged some well-known regions of high landslide susceptibility, like parts of the foothills of the Himalaya, the Assam-Meghalaya region, and the Western Ghats.
• It also revealed some previously unknown places with high risk, such as some areas of the Eastern Ghats, just north of Andhra Pradesh and Odisha.

A cartogram is called a thematic map in which a mapping variable, such as travel time, population, or GNP, is substituted for land area or distance.