Assessing Landslide Susceptibility in the Northern Stretch of Arun Tectonic Window, Nepal

Abstract

The northern stretch of the Arun watershed in East Nepal is dominated by steep slopes and rugged topography and experiences extensive landslides each year. Reliable landslide susceptibility assessment can potentially be an important tool for risk evaluation and mitigation in the Himalayas. The present study explores two GIS-based bivariate statistical methods, the weight of evidence method and the frequency ratio method to assess the landslide susceptibility of the study area. Seven major variables including slope angle, slope aspect, slope shape, geology, stream proximity, stream power index and land use were examined as the major contributing factors to landslide occurrences in the assessment. The landslide susceptibility map produced from these two methods are characterized by four zones of very low, low, moderate and high susceptibility. The landslide percentage of each zone turns out to be consistent with the order of its susceptibility. The results suggest that the weight of evidence method is more sensitive to the spatial variation of relevant factors; both methods produced fairly reliable results, as confirmed by a success rate of 75% for the weight of evidence method and 71% for the frequency ratio method. The present study demonstrates that the quantitative assessment methods explored may have a promising potential for landslide assessment and prediction in the Himalayas.