LANDSLIDE LOCATIONS AND VULNERABILITY ASSESSMENT IN RS/GISENVIRONMENT.E.Rakesh Reddy, PG Student, Veer Surendra Sai University of Technology, Odisha, India, rakesh15794@gmail.comB.Haritha Reddy, PG Student, Veer Surendra Sai University of Technology, Odisha, India, harithareddy1293@gmail.comABSTRACT:The study involves identifying landslide prone locations on State Highway No.72 between Poladpur and Mahabaleshawar, region from Western Ghats in Maharashtra. RS data and GIS tools have been used along with software ILWIS-3.3 for this purpose. Analysis involves DEM and developing various thematic maps using information value method based on ILWIS-3.3 software in GIS environment. Using above information probable immediate trouble locations have been identified on State Highway No.72 between Poladpur and Mahabaleshawar.Cross verification for few of such spots has been made by visiting locations proper, making observations and collecting data as well as photographs from site. Good agreement between these identified trouble locations and actual site-spots is noticed confirming the utility of method. The information can be useful for planning disaster preventive / mitigation measures.INTRODUCTIONThe possibility of natural hazard should berecognized in advance and efforts should be made tominimize threat to human life andproperty. Landslide is such type of hazard usually triggered by the tectonic movements, earthquakes, heavy precipitation and those factors induced due to change in land use such as felling of trees, agriculture, mining and road cutting in hilly terrain. Landslides may result in loss to property and life as well as may disrupt traffic in hilly region by blocking the roads.In Western Ghats (recently declared as World Heritage by UNESCO) many human habitats, tourist places and roads/highways are vulnerable to landslide-hazards. With this background study area/region is chosen as Mahabaleshwar-Poladpur Road (State Highway No.-72) which runs through hilly ghat region in Western Maharashtra. This highway is blocked many times in rainy season because of landslides and hence due attention must be given to assess probable sites/spots i.e. geographically critical areas prone to landslides hazard. Remotely Sensed (RS) data and tools from GIS with software ILWIS 3.3 have been used for the analysis with an objective to identifyprobable immediate trouble locations on this State Highway No.-72. OBJECTIVE OF STUDYThe Western Ghats from Maharashtra, along the Konkan coast, though located in a relatively stable domain, experience the fury of the landslide hazard due to steep hill slopes, greater overburden and high intensity rainfall. Landslide is a general term used to describe the down-slope movement of soil, rock and organic material under the influence of gravity. Though most slopes appear stable and static; they actually may not be stable systems. It is with this background that study region is selected as State Highway No.72 between Poladpur and Mahabaleshawar, region from Western Ghats in Maharashtra.The objective is to develop landslide hazard zonation map for this region and identify immediate trouble points along State Highway No.72 between Poladpur and Mahabaleshawar.The map has an inbuilt element of forecasting and is of probabilistic nature. Depending upon the methodology adopted and the comprehensive nature of the input data used, a landslide hazard zonation map can be used to provide the type and occurrence time aspect of landslide, extent of the slope area likely to be affected and rate of mass movement of the slope mass. The vulnerability assessment can be done from the landslide hazard zonation map and the physical, social, economic vulnerability can also be assessed. ProperPage 1 of 3preventive measures can be suggested according to severity and vulnerability at a location.The utility of remote sensing and GIS technic for generation of the thematic layers and an integrated approach to evaluate layer wise influence on landslide occurrence [1,2,3] has been described and illustrated. RS data and GIS tools can be used along with software ILWIS-3.3 for this purpose. Analysis leads to DEM and developing various thematic maps using information value method based on ILWIS-3.3 software in GIS environment. Using above information probable immediate trouble locations can be identified on State Highway No.72 between Poladpur and Mahabaleshawar. Immediate trouble locations are site-spots which are prone to landslide-hazard in near future.DATA AND PROCESSThe region selected for the study is geographically located between Poladpur (17 59 07. 45 N -73 27 59. 89 E) and Mahabaleshawar (17 55 08. 76 N - 73 39 32 .64 E).The geology of this hilly region comprises of sloping basaltic trap overlaid by a light capping of lateritic overburden. Lithomarch clay is present between sloping basaltic trap and lateritic overburden.The region has steep Westwards slopes and experiences heavy rain-fall during monsoon.Data from Cartosat-1, DEM 2012 with spatial resolution 2.5m and IKONOS -1M PAN sharpened MSS from Google Earth have been used.Analysis involves DEM and developing various thematic maps using information value method based on ILWIS-3.3 software in GIS environment.OUTPUTRS data from Cartosat-1, DEM 2012 with spatial resolution 2.5m and IKONOS -1M PAN sharpened MSS from Google Earth have been used and processed in GIS environment with software ILWIS-3.3 so that DEM and various thematic maps are obtained as output. Output consists of :Digital Elevation Model Slope mapSlope direction map Lithology Map Flow Accumulation map Flow Direction map Flow Type Map Landslide Risk zone map Road Vulnerability mapLandslide Susceptibility map Road Immediate Trouble zone mapImmediate Trouble PointLocation Road map Immediate trouble locations are site-spots, along the State Highway stretch between Mahabaleshwar and Poladpur, which are prone to landslide-hazard in near future.Immediate Trouble Point/spot Locations in terms of the Longitudes and Latitudes are given below in Table 1.Table 1Immediate Trouble Point LocationsPoint No.LatitudeLongitude11705529.9 N7303811.1 E21705449.2 N7303755.7 E31705458.7 N7303732.5 E41705510.7 N7303738.9 E51705531.7 N7303726.7 E61705639.8 N7303515.0 E71705651.6 N7303450.1 E81705656.4 N7303433.3 E91705646.1 N7303430.2 E101705624.1 N7303419.3 E111705613.7 N7303402.3 EHere only two maps as Landslide susceptibility map and Immediate Trouble Point Locations map are included in the paper.Photograph -1: Landslide susceptibility map.Page 2 of 3Landslide locations and vulnerability assessment in RS/GIS environment.Red -- Very high susceptibility Yellow High susceptibilityGreenish Blue Very low susceptibilityIt is seen that there is a vast region having very high susceptibility and a considerable part of it is nearby the existing State Highway.Photograph -2: Immediate Trouble Point Locations map.CONCLUSIONSThe immediate Trouble Points, eleven in number, have been interpretedalong Mahabaleshwar-Poladpur Road (State Highway No.-72) from analysis with use of RS and GIS and software ILWIS-3.3.Good agreement between these identified immediate trouble points and actual locations at site is noticed confirming the utility of method.Debris flow, Rock avalanche and creep due to plastic outflow of lithomarch clay are common types of landslide features observed at site.The landslide hazard zonation map can help planners to prepare and plan mitigation against, the effects of landslides on communities and infrastructure. The landslide hazard zonation map can help planners to assess and analyze different types of vulnerabilities, for minimizing the risks associated with new developments. The information obtained can be useful for NDMA in planning mitigation strategy.It is felt that landslide hazard zonation mapping may be carried out for the Western Ghat region from Maharashtra, especially for vulnerability assessment of settlement along high altitudes of Sahyadri upper reaches.The need is felt to develop the continuous monitoring system, with the help of high resolution data and GIS technology, which can monitor the probable movements of the hazardous area leading to disasters.REFERENCESKanungo, D.P. and Sarkar, S., (2003).Landslides and terrain parameters in Darjeeling Himalaya. Himalayan Geology,Dehradun, Vol.24. pp.55-62.Sarkar, S. and Kanungo, D.P., (2004), An integrated approach for Landslide Susceptibility Mapping using remote sensing and GIS. Photogrammetric Engineering and Remote Sensing, Vol.70, No.5 pp.617-625.Deshpande, P.K. , Patil J.R., Nainwal, D.C.andKulkarni, M.B., Landslide hazard zonation mapping in Gopeshwar, Pipalkoti and Nandprayag areas of Uttarakhand.Proceedings of Indian Geotechnical Conference-2009, Guntur, Volume-I,pp-808-814.Page 3 of 3