Geospatial Analysis of Mass Wasting Susceptibility in Siwalik Region; A Case of Nawalparasi (Bardaghat Susta West), Nepal

Abstract

Siwalik hills are occupied in the southern Himalayas and connect to Nepal’s Southernmost Terai bounded by Main Frontal Thrust in the south and the Main Boundary Thrust in the north. Landslides, Debris flow and Erosion are Mass wasting phenomena that remobilize sediments deposited on weak and brittle Siwalik hill slopes. This study aims to analyze mass wasting phenomena and prepare Mass-wasting susceptibility map by using frequency ratio model. Total 680 polygon of mass waste incident were recognized from Google earth and by field investigation. Study area cover 250 sq. km, out of which mass waste incidents cover 7.24 sq. km (2.89%). Landslide, Debris flow and Erosion contributes 36.60%, 57.04% and 6.36% respectively to total mass waste incidents. Susceptibility map was categorized into five classes as very low, low, medium, high and very high class covered 42.38%, 28.52%, 22.94%, 4.19% and 1.95% respectively. Performance of model was evaluated using area under curve (AUC). Success rate curve showed 82.15 % and prediction rate curve showed 78.30 % of the area lying under the curve. Mass-wasting susceptibility maps can be used as a planning tool by prioritizing areas for controlling the mass waste effects. District boundary has been selected for this study so that district individually can implement action plan may reduce coordination issues.