Unlike other disasters, landslides are largely controlled by highly localised factors. Landslides of different types are frequent in geodynamically active domains in the Himalayan and Arakan-Yoma belt of the North-Eastern parts of the country. Landslide hazard zonation mapping has categorized the Himalayan region as Very High Vulnerability Zone.
Factors that make the Himalayan region more prone to the occurrence of landslides:
- Geological factors o Tectonically active – Himalayan mountain ranges and hilly tracts of the North-Eastern region have high seismicity resulting from proximity to the plate margins. Co-seismic landslides are triggered or induced by earthquakes. o Steepness of Slope – Himalayan regions are highly susceptible to slope instability due to the immature and rugged topography, fragile rock conditions. They are mostly made up of sedimentary rocks and unconsolidated and semi-consolidated deposits.
- Climatic factors o Intense Rainfall – Heavy rains result in substantial soil erosion and can trigger frequent landslides.
- Anthropogenic factors o Deforestation – Decrease in natural vegetation cover has disturbed the stability of the slope as a result of change in surface and groundwater regime. It has loosened the soil and increased soil erosion. o Population Pressure and Developmental Activities – Unscientific land use due to urbanisation, construction of roads and dams, mining, increase in grazing activities etc. has increased the hazard manifold.