LANDSLIDE RISK MANAGEMENT BY MEANS OF PROPOSED LAND USE IN GINTUNG SUB-WATERSHED, PURWOREJO REGENCY, CENTRAL JAVA PROVINCE, INDONESIA

Abstract

The research was conducted on Gintung sub-Watershed. Gintung sub-Watershed is located among three districts: Loano District, Purworejo District, and Kaligesing District in Central Java Province. Gintung sub-Watershed is one of areas frequently suffered by landslide hazard. This research is aimed to manage landslide risk in the study area. Land allocation based on risk levels is proposed to provide the management of landslide risk. Three methods were applied in this research. First, statistic-probabilistic method was applied to obtain landslide susceptibility level of the study area. Multivariate statistic was used in this step. Logistic regression model was executed as the statistical approach. Slope, landform, soil, geology, land use, and aspect were the variables which were used in this analysis. Second, questioner survey was done to obtain vulnerability level of the elements at risk in the study area. Settlement and road network were the elements at risk which were analyzed in this step. Stratified-random sampling was applied on vulnerability assessment. Third, risk matrix was applied to obtain the risk level of landslide in the study area. The result of this research showed that 59.4% susceptibility level of landslide in Gintung sub-Watershed is categorized into moderate level. Probability of future landslide in the study area is greater than 0.6 respectively. Logistic regression equation stated that land use is the most controlling factor of landslide in the study area. Vulnerability level of settlement in the study area is categorized into moderate level. Vulnerability level of road network is categorized into high level. Based on the risk matrix, landslide risk level in the study area is categorized into moderate level. As a consequence, according to landslide risk levels in the study area, the proposed land uses are to limit settlement expansion in very steep slope area, to reduce garden uses through changing into dryland agriculture in flat up to undulating area and changing into bush and shrub in slightly steep up to steep slope area