Landslide Susceptibility Zone using Frequency Ratio Method in Karangkobar Catchment, Merawu Watershed, Banjarnegara District, Central Java Province

Abstract

Karangkobar catchment is located in the upstream area of Merawu watershed, classified as one of the most critical watershed in Indonesia. Land use change from forested area to agricultural land has changed the hydrological process in the catchment. A huge landslide disaster has occurred at the end of 2014 and causing 95 people deaths. It is important to have a landslide susceptibility map for disaster risk mitigation in this area. The purpose of this study is to apply the frequency ratio method to analysis the landslide susceptibility in Karangkobar catchment. Actual landslide data is obtained from the results of field survey. Frequency ratio method is used to assess the landslide susceptibility using 70% of total landslides data while 30% is used for model validation. The results shown that the highest FR value is found in the distance from the road at range of 0-25 m, distance from the river at range of 100-125 m, flat curvature and garden land use. The broad percentage of low landslide susceptibility is 38%. moderate susceptibility is 48% and high susceptibility is 14%. The results of validation for landslide susceptibility showed that the resulting susceptibility model is very effective for assessing the landslide susceptibility.