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Landslide zonation for hill area development
GIS analysis
In order to generate the landslide prone areas map for Kothagiri area, a model has been developed in a GIS environment. Data in the form of thematic maps such as slope, soil and landuse were input in to GIS. The detailed method of assigning weights has been discussed below. Finally the landslide prone areas map has been prepared.
- Slope
Slope is a very important parameter in any landslide hazard zonation mapping. In the study area slope varies from 0 to grater than 54 deg. The entire slope contour map was divided in to four categories as follows:
> 54 deg - very steeply sloping
36 - 54 deg - steeply sloping
18 - 36 deg - moderately sloping
0 - 18 deg - gently sloping
Thus, the slope contour map has got four categories and suitable weights are assigned.
(Figure - 5)
- Soil
The occurrence of landslide is mainly due to the presence of huge thickness of loose soils when mixed with water, it triggers the landslide. In the study area, based on the soils erodable nature, it is divided in to four categories as follows:
- Very highly erodable
- Highly erodable
- Moderately erodable
- Poorly erodable.
Thus, the Soil map has got four categories and suitable weights are assigned.
(Figure- 4)
- Geology
In the Nilgiri district, the lithology is the charnockite group of bedrocks, covered by the ubiquitous red laterite or lateritic soil. This is taken as a common factor for the whole district. Because of its uniform nature, it is not taken in to account for our study.
- Landuse
Landuse / land cover map of an area under investigation has got direct or indirect influence in triggering the landslides. Different types of landuse /land cover features are identified in the study area are such as tea, tea+tree, agriculture, grassland, road, settlement and forest. Suitable weights are assigned.
(Figure - 3)
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