Identifikasi dan penentuan faktor-faktor utama penyebab tanah longsor di Kabupaten Garut, Jawa Barat

Abstract

According to the data of mass movement disaster in Indonesia from 1990 to 2002, West Java Province (including Banten Province) frequentcy experienced landslide disaster. The map of mass movement of Garut District (Peta Gerakan Tanah Kabupaten Garut) made by Directorate of Vulcanology and Geological Disaster Mitigation (Direktorat Vulkanologi dan Mitigasi Bencana Geologi – DVMG), showed that there were several areas in Garut District classified in Susceptible Zones of high mass movement such as Banjarwangi District, Singajaya and Peundeuy. This study aims to 1) identify and analyze the characteristics of landslide in Garut District particularly in 3 municipals (Banjarwangi, Singajaya, and Peundeuy), 2) develop a model of relationsh ip between various causes of landslide and its conditions. In the preliminary stage of the study, literatures study on various factors of landslide were conducted and it is established in check list form as the field manual. The factors of landslide were then identified and analyzed. Based on analyzed data Principal Component Analysis (PCA) was conducted as well as cluster analysis and regression analysis to develop model of the landslide. Based on the observation, there were 32 spots of landslides occurred in the study area. There were 2 (two) characteristics of landslide found : 1) earth flow (30 cases or 94%), and 2) subsidence (2 cases or 60%). The high landslide as found in rice field area (25 spots) and followed by mixture garden/agroforestry (4 spots), 2 spots in housing area and 1 spot in the annual crops planted area. Analysis of PCA resulted 5 cluster with >40% similarity index. The multiple regression has generated an equation as followed: Y = 1.55 + 0.00186 v1 - 0.061 v3 + 0.038 v4 + 0.0216 v9 - 0.100 v13 where; Y : conditions of landslide zones, v1: soil thickness, v3: erosion conditions, v4: soil texture, v9: slope, and v13 : landuse (rice field).