IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) Landslide Hazard Zonation and Vulnerability Assessment Of Western Ghats - A Case Study in Taluk of ,

Raveendran.S1

Research Scholars,

University College, Thriuvananthapuram

Dr. Mani.K2

Associate Professor,

University College, Tthiruvananthapuram

Aneesh.M.R3

Research Scholars,

University College, Thriuvananthapuram

Abstract

Landslide hazard analysis and mapping can provide useful information for catastrophic loss reduction, and assist in the development of guidelines for sustainable land use planning. The present analysis is an attempt to demarcate landslide hazard zones in Devikulam Taluk of Idukki in GIS platform. The investigation incorporated Geomorphology, Geology, Drainage density, Slope, Soil and Land use layers .These thematic layers were overlaid with appropriate weights to generate landslide hazard zones in Devikulam taluk. The study area falls in the ecological sensitive Zone of the Western Ghats. It has a highly undulating topography with ridges intervening valleys, high peaks, and steep slopes leading to narrow gorges like valleys with gradient streams and plateau. The study area result could be classified into five vulnerable zones namely Class I, Class II, Class III, Class IV, and Class V. Among them Class I is a very low vulnerable zone while Class V is very high vulnerable zone. Analysis revealed that 43.72 % of the area falls under Class V, 25.55% of area falls under Class IV, 23.79 % of area falls under Class III, 6.12% of area falls under Class II, 0.01% of area falls under Class I. When on superimposing the pre-occurred landslide locations with our result, we find that most of the landslide Vulnerability locations fall under Class V and Class IV.

Keywords: Landslide hazards Zone Mapping, Raster Calculation, Devikulam, GIS

Introduction

Landslides are among the most widespread geological hazards that threaten lives and property, especially on the mountainous region of the world (Huabin, et al., 2005: jamali & Abdolkhani 2009). A landslide hazards map depicts an area prone to landslide by integrating the cause and trigging factors of the landslide with data concerning the past distribution of slope

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IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) failure. (Brabb 1984; Fall et al, 2006). In general terms it is used to describe a wide range of land forms and process involving the movement of the soil and rock down the slope under the influence of gravity (Reed, 1992). In recent times the occurrence of landslide have increased in both frequency and intensity resulting from a combination of several attributes include geological, gemorophological, morphometric, climatic, and anthropogenic that directly or indirectly cause slope instability (singh 2010). Landslide results in injuries and death induce environmental, physical and economical damage that impede the development of wealthy as well as poor nations and region of the world over (jamil & Abodkhani, 2009). The Landslide tend to dislocate objects that they come in conduct with by the way of uprooting trees, destroyed utility lines, such as telephone, gas, electricity and sewages tossing vehicle off the roadway and destruction of the road railway and bridges (shafri, et., 2010).

1.1 Study area

The area selected for the present study is Devikulam taluk of Idukki district in Kerala. It is situated in the Western Ghats, which is considered as one of the sixteen threatened ecological locations in the world. The study area stretched between the latitudes of 9 056’56” to 10021’24”N and longitudes of 770 48’ 31” to 770 16’ 14” E and covers an area of 1140.29 sqkm and is inhabited by 1, 77,000 persons (2011). This taluk is bordered on the north by Thrissur district and Coimbatore district (Tamil Nadu), on the east by Theni district (Tamil Nadu), on the south by Udumbanchola and Thodupuzha taluks of Idukki district, on the west by Ernakulam district The River Periyar and the Chinnar are the major rivers in the study area.

1.2 Aims and objectives

The major objectives of the present study are as follows:

 To develop and demonstrate some newer techniques of analysis for mapping the geohazards using remote sensing and GIS  Evaluate landslide susceptibility zonation map using weighted overlay method.  To suggest strategies for mitigation measures on the basis of controlling parameters for landslides

1.3 Materials and Methodology

The base map was prepared from SOI toposheets with 1:50,000 scales. Drainage, settlement, locations and roads were digitized and the thematic layers were generated from the SOI toposheets using Arc GIS software. The soil map was collected from SSOI (Soil Survey of ), Geology maps were collected from Geological Survey of India (GSI), Triangulated Irregular Network (TIN) and Digital Elevation Model (DEM) were prepared from SRTM-DEM, and LISS-IV image was used to generate land use and land cover map which was processed using ERDAS 9.2 imagine software. Proper weights were assigned to all the thematic raster layers. Finally, weighted Raster Calculation Analysis was carried out and landslide vulnerability zonation map was prepared.

Data Layer Preparation

This study is mainly focused to prepare a zonation map, Strategies and Mitigation for the landslide vulnerable zones in Devikulam Taluk. The preparation of landslide vulnerability zoning (LVZ) map is a major step in hazard management. After the creation of the primary layers, namely geomorphology, drainage density, slope, geology, soil and land use by using various advanced GIS

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IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) and Remote Sensing Techniques. To analyze the relationship between landslides and their influencing parameters, logic operation for Multicriteria overlay techniques were used for preparation of LVZ maps in the study. A direct mapping approach was used to establish the five different landslide vulnerable zones using classical raster calculation operations after having established maps representing major landslide influencing factors (Saha et al., 2002).Table No: 1

Geomorphology Sl.No Weightage 1 Denudation Structure Hill 8 2 Flood Plain 3 3 Pediplain 6 4 Pediment Zone 10 5 Rock exposure 4 6 Water body 0 Drainage Density Sq.km 1 0-1.08 Very Low 2 1.08-2.16 Low 3 2.16-3.24 Moderate 4 3.24-4.32 High 5 4.32-5.40 Very High Slope in Degree 1 0-0.6.69 1 2 0.6.69-15.40 2 3 15.40-25.25 8 Soil Classes 1 Clay 10 2 Gravelly Clay 8 3 Gravelly Loam 4 4 Loam 6

Landuse/Landcover 1 Water body 0 2 Tea plantation 3 3 Degraded Forest 10 4 Grassland 8 5 Built-up area 6 6 Plantation crop 4

Landslide Vulnerability Index

For landslide vulnerability analysis using the weights the Landslide Vulnerability Index (LVI) values were computed by summation of each factor’s rating multiplied by the weight of each of the factors by using the following as,

“LSZ = Slope*0.4+LU/LC*0.2+Geomorphology*0.15+Geology*0.1+Soil*0.08+Drainage Density*0.07” Where LVZ = Landslide Vulnerability Zone

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IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) From the calculation, it was found that the Landslide Vulnerability Zone had a minimum value of 8.78 and a maximum value of 1.5 The LVZ represents the relative vulnerability of a landslide occurrence. Therefore higher the index, the more susceptible the area is to landslide.

Results and Discussion The weighted themes were analyzed using Raster Calculation method in GIS platform. From this calculation we derive the cumulative map, which is classified based on mean, standard deviation and sum. The study area was classified into five vulnerable zones. They are Class I, Class II, Class III, Class IV, and Class V. Class I is a Very Low Vulnerability Zone where as a Class V is a Very High Vulnerability Zone. In this study area 43.72 %, of area falls under Class V, 25.55% of area falls under Class IV, 23.79 % of area falls under Class III, 6.12% of area falls under Class II, 0.01% of area falls under Class I. Overlay the pre-occurred landslide locations on LVZ map, we find that most of the landslide locations occurred in Class V and Class IV Zones. An analysis reveals that such areas have terrain characteristic like undulating topography, soil erosion, wrong land-use practices, and land encroachment due to population density, environmental fragmentation due to tourism development, deforestation, rock fracture zone and steep slopes.

Categories Area(sq.km) Percentage 1 (Very Low) 0.17 0.01 2 (Low) 69.47 6.12 3 (moderate) 289.98 25.55 4 (High) 496.25 43.72 5 (Very High) 270.01 23.79 TOTAL 1135 100

CONCLUSION

GIS and Remote Sensing have proved to be an effective tool for integrating various thematic layers for generating landslide hazard zone map and vulnerability assessment of the study area. The analysis could delineate five landslide hazards zones in Devikulam Taluk. The identification of hazard zones is an important pre-requisite to implement appropriate management strategies and mitigation in the study area.

Suggestion and Mitigation:

1. Research: To develop a predictive understanding of landslide processes and triggering mechanisms.

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IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981) 2. Hazard Mapping and Assessments: To delineating susceptible areas and different types of landslide hazards at a scale useful for planning and decision-making

3. Real-Time Monitoring: Monitoring active landslides that pose substantial risk.

4. Loss Assessment: Compiling and evaluation of information on the economic impacts of landslide hazards.

5. Information collection, Interpretation, and Dissemination: To establish an effective system for information transfer.

6. Developing guidelines and training for scientists, engineers, and decision-makers.

7. Public Awareness and Education: To developing information and education for the user community.

8. Implementation of loss reeducation measures: Encourage mitigation action.

9. Emergency preparedness, Response and Recovery: Building resilient communities.

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IJREAS VOLUME 5, ISSUE 6 (June, 2015) (ISSN 2249-3905) International Journal of Research in Engineering and Applied Sciences (IMPACT FACTOR – 5.981)

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