Landslides, a gravity induced geological phenomenon, are primarily associated with the mountainous terrains. However, they can also occur in areas where activities such as surface excavations for highways, buildings and open pit mines take place. Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low permeable bottom soils or weathered rock. Sudden and heavy downpours over a short period of time, which are often localised in nature termed as cloudbursts, can sometimes lead to landslides. Deep-seated landslides usually involve deep weathered rock or bed rock and include large slope failure (Fig. 1). Some landslides are rapid, occurring in seconds, whereas others may take hours, weeks, or even longer to develop.
Landslides are one of the natural hazards that affect at least 15 per cent of India’s land area exceeding 4,90,000 sq km. Landslides of different types occur frequently in the Himalaya, northeastern India and also in the stable domains like in Western Ghats and Nilgiri Hills of southern India (Table 1). About 0.098 million sq km of the North Eastern Region, comprising the Arakan Yoma ranges, and 0.392 million sq km of parts of the Himalaya, Nilgiri, Ranchi Plateau and Eastern and Western Ghats are affected by landslides. Landslides sometimes can be a disastrous consequence; over 500 people were killed due to landslides in 2005 in different parts of India. Landslide hazard analysis and mapping can provide useful information for catastrophic loss reduction, and assist in the development of guidelines for sustainable land use planning.