LANDSLIDE SUSCEPTIBILITY MAPPING WITH HEURISTIC APPROACH IN MOUNTAINOUS AREA A CASE STUDY IN TAWANGMANGU SUB DISTRICT, CENTRAL JAVA']JAVA, INDONESIA

Landslide susceptibility mapping is one of the required activities in landslide prone area. This is intended to recognize the spatial probability of landslide as an action to minimize the upcoming impact. Landslide susceptibility map can be used as supporting information in spatial planning process as well, particularly in restricting landslide prone area as free of development zone. Currently, landslide susceptibility mapping had not been done yet in Tawangmangu Sub District. In fact, this area was often suffered by landslide. Thereby, this research was focused on generating landslide susceptibility map for this area in order to improve the current spatial plan and to guide local government in managing present and future land utilization Landslide susceptibility information was developed by harnessing heuristic approach with weighted-score method. Six parameters utilized were slope, lithology, soil depth, texture, permeability, and land use. Some parameters related to soil properties were obtained from field survey with landform based while land use information was achieved from visual interpretation of Ikonos imagery followed by field checking. All parameters were assigned a certain weight and score based on expert judgment. The weight was automatically processed through rank method which is available in ILWIS (Integrated Land and Water Information System) software whereas the score was given in the range of 1 - 4. Apart from that, landslide inventory mapping was also conducted by visual interpretation of Ikonos imagery and field survey. Study area is mostly classified as high and very high susceptible zone (50%). Moreover, 36% of total study area is categorized as moderate susceptible to landslide. The rest area is included in low and very low susceptible zone. Based on this result, it can be also identified that more than one third (47%) of settlement area in this location is situated under landslide threat. It is only 25% of total settlement area located in very low and low susceptible zone. To overcome this circumstance, the comprehensive landslide mitigation strategies must be developed to enhance the recent landslide mitigation activities and to supplementary reduce the possible damages and destructions.