To prepare a landslide susceptibility map of Shivkhola watershed, one of the landslide prone parts of Darjeeling Himalaya, remote sensing and GIS tools were used to integrate 10 landslide triggering parameters: lithology, slope angle, slope aspect, slope curvature, drainage density, upslope contributing area (UCA), lineament, settlement density, road contributing area (RCA), and land use and land cover (LULC). The Analytical Hierarchy Process (AHP) was applied to derive factor weights using MATLAB with reasonable consistency ratio (CR). The frequency ratio (FR) model was used to derive class frequency ratio or class weights that indicate the relative importance of individual classes for each factor. The weighted linear combination (WLC) method was used to determine the landslide susceptibility index value (LSIV) on a GIS platform, by incorporating both factor weights and class weights. The Shiv-khola watershed is classified into five landslide susceptibility zones. The overall classification accuracy is 99.22 and Kappa Statistics is 0.894.
The Remote Sensing and GIS tools have opened new paths in land and water resource studies, presently. Satellite images are increasingly used in ground water exploration because of their utility in identifying various geomorphic features. In the present study, all the prepared thematic data layers such as slope, relief, soil, geology, geomorphology, drainage, land use and 'NDVI' are integrated using the Spatial Analyst Tool in Arc GIS 9.2 implying weighted overlay methods to delineate the Ground Water Potential Zones in Kangshabati Irrigation Command Area (KICA). In weighted overlay analysis rank value assigned for each class of all thematic data layers according to their influence on ground water hydrology and factor weighted values are assigned according to analytical hierarchy process (AHP). Finally, an accuracy study is being performed in ERDAS Imagine Software by ground truth verification of 30 training sites with GPS readings for major land use/ land cover information which states the overall classification accuracy of the present study is 86.66%.
River bank erosion is a hazardous and common phenomenon in diara region near Malda district of North East India during monsoon and post-monsoon periods of every year. One of the significant causes behind the erosion is the textural composition and its arrangement along the river bank. The left bank of Ganga River is texturally very weak along diara region of Malda district. In the present study, the nature of riverbank soil textural composition has been measured by basis parameters analysis and mechanical analysis of soil and its erodibility level. Sieve analysis has been done on all collected soil samples and determines soil basic parameters. The nature of the soil has been derived through the mechanical analysis of particles after Folk and Worst method. Besides that, the degree of soil erodibility has been analyzed through the Bouyoucos Erodibility Index and ROM scale after Roslan and Mazidah. The results show that the erodibility levels become high to the moderate condition along the middle to lower extension of left bank line and relatively low along with upper extension according to ROM scale. Nature of soil along the left bank is dominantly sandy which also indicates the vulnerable condition of bank sites. Basic parameters of soil and its mechanical analysis also reveals that unstable condition exists along with the whole extension of the riverbank line but instability condition is increasing from upper to lower segment of bank line. So the risk of riverbank failure can be measured by determining the textural composition of the soil.
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