EVALUATION OF RAINFALL-INDUCES LANDSLIDES IN BANJARNEGARA, CENTRAL JAVA, INDONESIA USING TRIGRS
Abstract
Severe landslide followed by debris on 12 December 2014 ruined infrastructures and buried hundreds of peoples in subdistrict Karangkobar, District Banjarnegara, Central Java. A high daily rainfall reached about 200 mm for two days prior to the disaster. This paper presents the prediction and evaluation the landslide area using TRIGRS (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability) version 2.0 model. The model was applied to calculate pore water pressure and the factor of safety (FS) during rainfall infiltration. The model used DEM, geological and geotechnical properties, infiltration variables and rainfall intensity. At the initial condition, before rainfall infiltration, the lowest FS value ranges from 1 to 1.2, where is distributed at the steep slope area near the Jemblung. The simulation results obtained that the steep slope area, where the inclination angle is greater than 30o, are susceptible to failure (FS < 1.2) during the rainfall infiltration. However, in some locations of steep slopes were likely not fail (FS > 1.2). In general, this study concluded that the predicted location of slope failure by TRIGRS agreed with the field observation of the landslide occurrences