Geology and landslide hazard zonation by using GIS of Gedangsari Area, Gunungkidul, Yogyakarta, Indonesia

Gunungkidul is located in Central Java Province, Indonesia which are vulnerable to geological hazard such as floods and earthquake. However, it is also susceptible to landslide in some areas of Gunungkidul which contributes to damage and loss. The study area is located in Gedangsari Area of Gunungkidul with the area covered of 5km2 which aligned along latitude 7° 49’ 30’’S to 7° 52’ 00’’S and longitude 110° 34' 00’’E to 110° 36' 30’’E. This research aims to update a geological map of Putat Area with scale of 1:25 000 and to produce a landslide hazard map. The factors that triggered the landslide in Gunungkidul, Special Region of Yogyakarta were also analysed. The research involves the study of geomorphology, stratigraphy, structural geology and historical geology of the study area. The study area composed of three formations which is Nglanggeran Formation, Semilir Formation and Kebobutak Formation which were divided into six lithology units. The parameters that caused the occurrence of landslide were determined and the landslide susceptibility map was produced using Weightage Overlay Method (WOM) in ArcGIS software. Results showed that the zonation map was classified into three zones which is low, moderate and high zone. The factor that triggered the landslide were identified which is heavy rainfall intensity and earthquake. As a recommendation, the ability to detect landslide susceptibility led to a better understanding of landslide mechanisms for the research area, thus leading to an enhanced identification of the most likely failure sites within a landslide-prone area.