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Methodology
Various thematic maps like geology geomorphology, landuse, rainfall. Lineament density, drainage, soil and slope were prepared in the scale of 1:50, 000. Toposheets, satellite images and published maps were used to compile the themes. The maps were scanned and input into the system. Each map was geometrically corrected for latitude and longitude. The thematic maps were digitized and polygons and each feature in as there was given an identity. A sample of 25 landslides from the inventory map was taken and the number of landslides occurring in each feature of a thmatic map was counted.

The map layers were considered as separate entities and each feature in a map layer was ranked according to the frequency of occurrence of landslides. High the number of landslide occurs higher the rank. Thus, rank I indicates low susceptibility and rank 4 indicates a high susceptibility analysis was done by overlay. The eight thematic maps were overlaid on one another successively. The eight thematic maps were taken as 4 pairs and each pairs was overlaid were item successively overlaid.

Landslide Susceptibility ranking

Landslide susceptibility value	Susceptibility rank
29-32	Very high
23-28	Moderate to high
17-22	Low to Moderate
8-16	Very low

The maps thus devices the area in to form zones of varying slope stability. The map was used for analyses the control of slope land used geomorphology and lineament density in triggering slides. The slope map, lineament density map and drainage density maps were also ranked according to expected occurrence of landslides to landslide susceptibility increases with increasing slope, lineament density and drainage density. Thus higher slope percentages were given a higher rank as they are usually more susceptible to sliding. Overlay of all the terms were done and a landslide hazard zonation map was prepared. This was compared with the landslide hazard zonation map based on past slides.

Analysis And Information
The landslide hazard zonation map for the study area covering 500 square kilometers clearly indicates that there are few zones of low susceptibility. Landslides can occur through out major portion of the study area. Nearly 18% of the total study area falls in the very high susceptibility zone. Fifteen landslides from the landslide inventory map were overlaid on the map. Nine landslides fell in the highly susceptible zone, three in the moderately susceptible and two in the low to moderate zones are also susceptible areas and sliding may be triggered.

Recommendations
The following recommendations are given for landslides hazard mitigation based on the present work for the regions, where slope in the main triggering factor the upper parts of the slope can be unloaded or the lower slopes can be loaded. A general flattening of the slope can be achieved. Boulders on the upper slops can be removed to arrest their movement.
Rainfall is an important cause for landslides surface water should be deviated and not allowed to infiltrate in to the ground. Horizontal drains and drainage galleries can be made for the purpose. The run-off can be intercepted by cut-of drains or through the nearest culvert. The conduit of the culvert slopes should not be allowed to get choked up and proper care should be taken to remove the block periodically.
Retaining and strengthening structures like retaining walls and cribs can be used to protect unstable slopes. Hill slopes are cut at the toe and provide space for construction of building and rocks stability. Reinforced earth retaining walls are capable of strengthening slopes.
Afforestation ploys a key role in increasing the stability of the slopes. The barrier slops can be planked with tree a number of grasses like lemon grass have been known to protect slopes from sliding.

Refrences
Gupta R. P, Joshi B. C. 1990. Landslide Hazard Zoning using GIS approach - a case study from the Ramganga catchment - Himalayas, Engineering Geology 28 119 - 131.
Hydro geological conditions in Nilgiri district 1984, Central Ground Water Board, Dept. of Irrigation Tamil Nadu India
Nilgiri landslide. 1982. Geological Survey of India Miscellaneous publications No 57.
Pachouri A. K , and Pant. M. 1992 Landslide hazard mapping base on geological attributes. Engineering Geology. 32, 81 - 100.
Report on the study of landslides of no Vol 993 in Nilgiri District 1993, The Geotechnical cell Coonoor.

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