INTRODUCTION
Landslides have become more severe especially with increase of human intervention on unstable hill slopes. Academicians argue over which hazard is the most frightening and awesome. But the most important is the necessity to evaluate them in terms of their suddenness, severity, areal extent, potential economic losses, degree of warning possible and the level of possible mitigatory measures. Realising such importance, the 44th General Assembly of the United Nations has adopted the resolution proclaiming the decade starting 1990 as the International Decade for Natural Disaster Reduction (IDNDR).
Landslides
Landslides belong to that family of short lived and suddenly occurring natural phenomenon that can cause extraordinary landscape changes and destruction of life and property. In the strict sense, landslides are relatively rapid down slope movement of soil and rock, which takes place characteristically on one or more discrete bounding slip surfaces which define the moving mass (Hutchinson, 1988).
Causative factors
Changes in the slope gradient both natural and man-made, changes in antecedent moisture content, vegetation, lithological assemblage etc. are some of the factors that have a direct bearing on the stability of a region. Normally the calamity is triggered by a sufficiently strong mechanism which overcomes the natural stability of a segment i.e. the shear resistance threshold is exceeded. Seismic events and excessive precipitation are considered to be common triggering mechanisms.
Landslide Hazard Zonation
The term Landslide Hazard Zonation applies in a general sense to divide the land surface into discrete zones and rank them according to degrees of actual or potential hazard from landslides or slope instability (Varnes, 1984). All zonation studies carried out till date relies on three fundamental assumptions. (a) The slope failures in future will most likely be in similar terrain conditions that have led to past and present failures. (b) In a given area the main conditions that cause landsliding can be identified . (c) A summary of the degree of potential hazard in areas can be built up, depending on the number of failure inducing factors present, their severity and their interaction. However, the overall accuracy of Landslide Hazard Zonation mapping for discrete areas still remains unevaluated and it is only rarely possible to predict the exact location and time of a probable landslide.
Mitigatory measures
Detailed study involving geological, geomorphological, hydrological, meteorological, soil and rock mechanics parameters along with other relevant terrain factors and socio-economic factors determines the most appropriate control and prevention measures
Community participation
In disaster situations it is the community which responds first before any other agency. The accumulated experience of the community and the resistance built by it are valuable assets in the effective management of a disastrous situation. Local community may be equipped through effective public awareness programmes to develop adequate skills to combat the hazard