Landslides In India

Abstract

Landslides and slope failures are common features affecting the southern face of the Lesser Himalaya. Northeastern ranges including the Naga-Lusai ranges, hills of Mizoram are no exception. Western Ghats also face this problem during southwest monsoon months. It is a chronic problem for a sloping land subject to heavy seasonal rainfall preceded by a hot dry summer.

Landslide may be defined as a form of crustal displacement of rock- mass under the influence of either surface runoff, groundwater seepage or due to earthquake or by some other factors. It causes a rapid dislocation of the mass of rock/debris or residual soil or sediments along or adjoining a slope where the centre of gravity of the moving mass advances in a downward and outward direction. Landslides on a slope formed due to human activities are usually referred to as ‘slope failure’.

The magnitude of damage caused by the sudden and unexpected earth movements is huge and it is becoming costlier day by day to tackle the problems associated with these hazards. It is aggravated during and soon after a heavy rainfall. Various corrective and protective measures have been adopted by engineering geologists and civil engineers from time to time. In the process it has been observed that each landslide is unique by itself and, therefore, to control mass wasting and slope failure it is essential to understand the mechanism of slide initiation and its downward propagation together with the causes responsible for these hazards.

The phenomena of landslides and slope failures are studied from two different viewpoints - one that from geomorphological and the other from engineering point of view. Geomorphologists consider landslides as a natural process co-acting in sculpturing the land surface where such phenomena are studied as a significant exogenic denudation process. Whereas an engineer is concerned about the safety of a construction and stability of the base-rock at the site of the structure erected.

Hydrological investigations of landslide areas have attained immense urgency after recent frequent landslides over hills and mountain slopes immediately after a heavy downpour. Rate of surface runoff, percolation and penetration of surface water at landslide spots and along the roads prone to landslides need to be analyzed and effective designs of drainage systems are necessary. Anthropogenic disturbances like bursting of bed rocks by dynamite explosion, movement of heavy vehicles through highways across the hills, deforestation and urban expansion need restriction.