Journal of Applied Geology, vol. 4(1), 2019, pp. 1–8 DOI: http://dx.doi.org/10.22146/jag.48735 Landslide Risk Assessment for Designing Monitoring and Early Warning System Tuan Anh Bui 1 , Teuku Faisal Fathani * 2,4 , and Wahyu Wilopo 3,4 1 Master Program in Natural Disaster Management, Department of Civil and Environmental Engineering, Faculty of Engineering, Universitas Gadjah Mada 2 Department of Civil and Environmental Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta 3 Department of Geological Engineering, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta, Indonesia 4 Center for Disaster Mitigation and Technological Innovation (GAMA-InaTEK) ABSTRACT. Landslide is the most frequent natural disaster in Yogyakarta, Indonesia. In the mid-March 2018, a few cracks appeared in the north of the hill in the Pendoworejo Village, Kulon Progo District, Yogyakarta Special Province. The landslide movement of this area still threatens the residents and makes them evacuated due to their fear upon potential landslide disaster. In order to reduce the risk, landslide investigation and risk assessment were conducted. The stability analysis focused on the relationship of the dis- placement, the velocity and the fluctuation of groundwater level due to the rainfall inten- sity. Then, a monitoring and warning system was designed as a non-structural mitigation effort. Based on the preliminary investigation on April 2018, there was no evidence of mass movement on the west and south part of the hill. On the other hand, the north part area was estimated to have risk as indicated by the occurrence of many cracks. Based on the result of analysis, the fluctuation of the groundwater level rose or dropped substantially before and after heavy rainfall. In the rainy season, the velocity and the displacement in- creased slightly in the first three months and grew rapidly afterward. In fact, the landslide risk increased in every rainy season. Therefore, the risk could be more dangerous in the future. Keywords: Slope stability analysis · Groundwater · Rainfall intensity · Movement velocity · Mitigation · Monitoring devices. 1 I NTRODUCTION In the mid-March 2018, a few cracks appeared in the north of the hill in the Pendoworejo Vil- lage, Kulon Progo District, Yogyakarta Special Province. Especially, there was a serious crack across a residential house that happened in the end of March 2018. Hence, fearing the poten- tial landslide hazard to happen due to the land- slide movement in this area, the residents had to evacuate themselves. As shown in the Figure 1, the research area included the hill of Pendoworejo Village which * Corresponding author: T.F. FATHANI, Department of Civil and Environmental Engineering, Gadjah Mada Uni- versity. Jl. Grafika 2 Yogyakarta, Indonesia. E-mail: tfathani@ugm.ac.id covered approximately 1 km 2 . The location was situated between latitudes of -7.755° to - 7.757° and longitudes of 110.192° to 110.189°. The morphology of the area consisted of terrain with steep hill and narrow valleys. The slope inclination of the research area varied from gen- tle to steep (15° to 58°) with minimum and max- imum of altitude that varied from 145 m to 270 m above the sea level. The study area was dominated by hilly morphology with landslide occurrence in addition to homogenous lithol- ogy composition (Karnawati, 1998). It was also in humid tropical climate condition and sensi- tive for landslide occurrence. Interaction be- tween geology and long-term climate condi- tion resulted in significantly different landform 2502-2822/© 2019 Authors