Kalitelaga Landslide

A pilot area for landslide monitoring, prediction and early warning program has been established in Banjarnegara Regency, Central Java Province, since year 2007. Based on the site investigation, it is clarified that not only the rain intensity but also the morphology and geological conditions of study area significantly control the occurrence of landslides. The unstable zone in the study area is situated at lower slope of mountains with the slope inclination of 20 degrees to 60 degrees. The moving materials consist of colluvial deposits of silty clay overlying the inclined impermeable layer of clay, which is situated at the lower part of the andesitic breccias mountain. The clay layers are inclined at the same direction of the slope (i.e. 85 degrees) and this becomes the sliding failure for the above colluvial soils. The moving zone is saturated at most of the rainy season due to the lower position of the zone comparing to the surrounding mountainous slopes. The existence of impermeable clay layer underneath the colluvial soils creates the saturation condition within colluvial soil gradually increased and maintained during the rainy season, until then the rise of pore water pressure within this soil induces the movement. Therefore, monitoring of the pore water pressure (groundwater table) in response to the rain infiltration should be the main concern in establishing early warning for the slope movement. The Asian Joint Research Project for Early Warning of Landslides consisting of International Consortium of Landslide (ICL), Gadjah Mada University (GMU), and Disaster Prevention Research Institute of Kyoto University (DPRI/KU) has conducted a preliminary investigation and established a real-time monitoring and early warning system at that pilot area. The outdoor unit of fieldserver gathers the data from multiple sensors (two long-span extensometers, raingauge, IP camera and water pressure sensor), whereas indoor processing unit will store data on the monitor, and send the data through GPRS modem to be displayed in a webserver. Source: Teuku Faisal Fathani, Dwikorita Karnawati, Kyoji Sassa, Hiroshi Fukuoka, Kiyoshi Honda. Development of Landslide Monitoring and Early Warning System in Indonesia.