Landslides are a recurring phenomenon that disrupts the natural environment and causes yearly property damage, economic losses, and fatalities. The damage is expected to increase due to deforestation rates, population growth, agriculture, slope-building infrastructure expansion, and global climate change. This study assesses the susceptibility to landslides through Weight of Evidence (WoE) and Frequency Ratio (FR) methods in the Temanggung Regency, Central Java Province, Indonesia, that located on the slopes of two active volcanoes. Initially, a landslide record and the input parameters of the landslide controlling factors were prepared from field surveys, remote sensing data, and secondary data and processed by a geographic information system (GIS). Six landslide parameters in thematic layer maps were selected to develop landslide susceptibility: slope, lithology type, geological structure density, land cover, and rainfall. According to the WoE and FR models, a landslide susceptibility zoning map was classified into four landslide-prone zones from low to very high. Finally, the success and predictive rate curves method confirmed the landslide susceptibility maps to check the model accuracy. The results showed that the landslide susceptibility map using the WoE method had better accuracy than the FR method, with a success rate of 78.48% and a prediction rate of 81.1%. In comparison, the FR method was 74.53% for the success rate and 78.48% for the prediction rate. These landslide susceptibility maps can be used as a guideline to develop land-use planning and landslide disaster mitigation.

Bantul Regency is an area of the Special Region of Yogyakarta Province prone to earthquakes, mainly due to plate tectonic activity. On May 27, 2006, an earthquake of 6.3 Mw hit the Special Region of Yogyakarta and caused considerable damage in Bantul Regency. One of the impacts of the earthquake liquefaction, therefore, it is necessary to analyze the potential for liquefaction in the southern part of Bantul Regency. This research aims to determine the potential for liquefaction at the research location by considering the value of the liquefaction safety factor from the cone penetration test (CPT) data. The method used in this research is potential liquefaction analysis using the calculation method from the NCEER1998 consensus. The results of the potential liquefaction analysis are based on CPT data at three test points and correlated with core drilling data. The liquefaction potential zones in the CPT-1 are at a depth of 0.2 meters to 5.4 meters with a thickness of 5.2 meters. Whereas in CPT-2 potential for liquefaction zone that has the is at a depth of 0.2 -9.4 meters with a thickness of the liquefied layer of 8.4 meters, then in CPT-4, it is at a depth of 0.2 -11.2 meters with a layer thickness of 8.2 meters. Based on the three CPT data, the liquefied layers are in a layer of fine sand to coarse sand.

Imogiri District is one of the areas located at the foot of the southern mountains, with many rivers crossing the area. The Cempaka Cyclone in March 2019 caused a big flood in the Imogiri district and its surrounding area. Flood may affect various sectors of the socioeconomics life of a society, such as sectors of the economy, and agriculture, especially a severe effect on environmental and surface/groundwater systems in areas. The research objective is to assess flood hazards and their impact in the Imogiri District, Bantul Regency, Yogyakarta Special Region. The research was conducted by field survey and interview with an impacted community from the flood. The outcome of this study revealed that the area with high flood-prone potentials is distributed in the eastern and central part of the study area, along the river flood zone. The flood disaster caused property and agricultural losses but did not cause any casualties. The community was unprepared for the flood disaster, which had not occurred as big as in 2017.

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