Landslides are caused by mechanical disturbances, in which large mixed mass of rock, earth, and debris move down a slope. Debris flows, also known as mudslides, are a common type of fast-moving landslide that tends to flow in channels.
These are typically steeper slopes with less stable soils or bedrock, slow flows with high sediment content, or high water content in the slope.
Landslides are likely to occur when the change in stress exceeds the strength of the materials that make up the slope.
High Vulnerability Zone:
Ecologically fragile areas are generally denoted as ‘Highly vulnerable zones’. These are areas that could be affected by human interference which could lead to drastic changes in the ecological balance.
Areas that are ecologically fragile should not be disturbed indiscriminately by human activities that are likely to disrupt an area’s natural state or cause it to become irreversibly damaged.
Highly unstable, relatively young mountainous areas in the Himalayas and Andaman and Nicobar, high rainfall regions with steep slopes in the Western Ghats and Nilgiris, the north- eastern regions, along with areas that experience frequent ground-shaking due to earthquakes, etc. and areas of intense human activities, particularly those related to construction of roads, dams, etc. are included in this zone.
Moderate to Low Vulnerability Zone:
Areas that receive less precipitation such as Trans- Himalayan areas of Ladakh and Spiti (Himachal Pradesh), undulated yet stable relief and low precipitation areas in the Aravali, rain shadow areas in the Western and Eastern Ghats and Deccan plateau also experience occasional landslides.
Landslides due to mining and subsidence are most common in states like Jharkhand, Orissa, Chhattisgarh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, Tamil Nadu, Goa and Kerala.
Consequences of Landslides
Landslides have relatively small and localised area of direct influence, but roadblock, destruction of railway lines and channel- blocking due to rock-falls have far- reaching consequences.
Diversion of river courses due to landslides can also lead to flood and loss of life and property.