Landslide susceptibility mapping of Tevankarai Ar sub-watershed,Kodaikkanal taluk,India, using weighted similar choice fuzzy model |
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| Authors: | Sujatha E Ramani Rajamanickam Victor |
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| Institution: | (1) Thanjavur, India |
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| Abstract: | This paper deals with the landslide susceptibility zonation of Tevankarai Ar sub-watershed using weighted similar choice fuzzy
method in a GIS environment. There has been a rapid increase in landslide occurrences in the Kodaikkanal town and area surrounding
the town specially in the settlements around the town and road links leading to and from the town. This necessitates a detailed
study of slope instability problems in this area. It is observed that these incidences occur frequently during the monsoon
and summer showers. Rainfall is identified as the prime triggering factor. Eleven physical factors that cause instability
are identified as causative factors from the field investigations and landslide occurrences. Land use pattern, slope gradient,
curvature and aspect, weathering index which are evaluated from the weathering ratios of different chemical constituents of
the three major lithological variations, soil type, hydraulic conductivity of soil and soil thickness, geomorphology, drainage,
and lineament have been utilized to prepare the spatial variation. A weighted similar choice fuzzy model which ranks a set
of alternatives by identifying the similarity between the outcome of alternatives and outcome of ideal alternatives is used
to rank the causative factors. Each causative factor is classified into sub-categories and rated based on their effect on
stimulating the landslide event using qualitative judgment derived from field studies and landslide history. The prepared
thematic maps of causative factors are integrated, utilizing the GIS software Arcmap. The outcome has projected the low, moderate,
high, and very high landslide susceptibility zones. The high-hazard and very high-hazard areas fall in the northwestern part
characterized by croplands and agricultural plantations, while the moderate hazard zones are seen in prominent settlements
and low-hazard zones are observed in the sparse settlements and zones of less agricultural activity. The model is verified
using the relative landslide density (R) index, and the susceptibility map is found to be consistent with the mapped landslide
incidences. The results from this study illustrate that the use of weighted similar choice fuzzy method is suitable for landslide
susceptibility mapping on regional scale in growing hill towns as Kodaikkanal town. |
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