Landslide susceptibility mapping along Tulsipur-Kapurkot road section and its surrounding region using bivariate statistical model

Abstract

The Tulsipur-Kapurkot road is the main highway connecting the northern part of Rapti zone to the rest of Nepal. It suffers from numerous mass movements obstructing the traffic every monsoon. This paper describes the development of landslide susceptibility map of the road section and its surrounding regions based on bivariate (frequency ratio) statistical model. Geologically, the road section passes through the rocks of Lesser Himalaya, Siwaliks and Quaternary deposits. Several large and small scale thrusts present within the area making it unstable. For the susceptibility evaluation of the region, first a landslide inventory map consisting more than 187 landslides was prepared. These landslide locations were then randomly partitioned into a ratio of 80/20 for training and validating the models. Second, nine landslide causative factors were prepared. They include slope, aspect, elevation, curvature, geology, land use, distance from fault, distance from river and distance from major road sections. Finally, a landslide susceptibility map of the region was obtained and it was validated using area under curve (AUC). From the analysis, the success rate of the model is found to be 85.18% and predictive accuracy is 78.76%. The resultant susceptibility map shows that the highway in between Ranagaun to Khamari and Ramri to Kapurkot falls within very high to high susceptible zone. Besides, it is observed that the Kapurkot Bazar is also under high landslide susceptible zone. Furthermore, the northern part of the watershed lies in high landslide susceptible zone. The result of this study is useful for land use planning and decision making in landslide management activities.