Djoko Legono

The Application of Monitoring and Early Warning System of Rainfall-Triggered Debris Flow at Merapi Volcano, Central Java, Indonesia

The 2010 Mt. Merapi eruption has produced approximately 140 million m3 of pyroclastic deposit, in which more than 10 million m3 deposits are potential to move downstream through Boyong/Code River towards Yogyakarta City. The flow behavior of Code River may be affected by the presence of accumulated sediment at the upstream of the river (namely Boyong River). By rainfall trigger, this potential source can cause debris flow disaster that may contribute damage to the settlement areas in Yogyakarta City. This paper presents the application of monitoring and early warning system to mitigate the impact of debris flow disaster along Boyong/Code River as revealed by most adaptive, low cost, and collaborative-based technology. The real-time monitoring equipment consists of automatic rainfall recorder, automatic water level recorder, debris sensor, and interval camera. The system was developed by considering the community aspiration in determining the types and placement of monitoring equipment, and maintaining its sustainability. The information flow of the proposed early warning system has been introduced accordingly. The central station receives the results of the real-time monitoring and the information through radio communication from the focal points located along Boyong/Code River. Afterward, the warning alert is sent to focal points and the debris flow monitoring radio. This newly built system is expected to be integrated with the monitoring system of other volcanic rivers at Merapi Volcano.

TXT-tool 2.062-1.2 A Monitoring and Early Warning System for Debris Flows in Rivers on Volcanoes

Volcanic eruptions may produce large amounts of pyroclastic material. Such material will then be transported down a volcano’s rivers due to slope instability or rainfall, and then settle in alluvial fan areas. Further migration of this deposited sediment along the river may occur through both natural mechanisms (hydraulic phenomena) as well as anthropogenic processes (human interference). This paper presents the application of monitoring and early warning systems to mitigate the impact of debris flows, using adaptive, low-cost, and collaborative-based technology. A long-running and sustainable system for monitoring and early warning of debris flows in the rivers of Mt. Merapi volcano in Indonesia will be used as case study for the implementation of this model. The 2010 Mt. Merapi eruption produced approximately 140 million m3 of pyroclastic deposits, of which more than 10 million m3 deposits have a potential to move downstream through Boyong/Code River towards Yogyakarta City and cause damage to the settlement areas. A real-time monitoring and warning system has been developed by considering community wishes in determining the types and placement of monitoring equipment, and maintaining it sustainably. The equipment consists of an automatic rainfall recorder, automatic water level recorder, debris sensor, and interval camera. The information flow for the proposed early warning system has been set up. The central station receives both the results of the real-time monitoring, and information through radio communication from key persons. Afterward, a warning alert is sent to key persons and the debris flow monitoring radio. This newly built system is expected to be integrated with the monitoring system of rivers, not only at Mt. Merapi but also on other volcanoes in Indonesia.

Rain Behaviour at Mt. Merapi Area as Observed by XMPR and ARR

Short duration rainfall information has now become one of many important aspects to support the development of warning criteria for disaster mitigation. Similar importance is also found in the development of warning criteria against the lahar flow disaster at Mt. Merapi area. The rainfall information obtained from the radar observation has also become a new challenge for the last decade in line with the rapid growth of information and communication technology. However, the accuracy of its estimation needs to be evaluated by considering the correlation between radar rainfall and rain gauge rainfall. In case of radar rainfall can be precisely estimated, this information will contribute to generating appropriate warning criteria. This study was carried out as the first attempt to evaluate the rainfall information as performed by the X-Band Multi Parameter Radar (XMPR) that was installed at Mt. Merapi in the mid-August 2015. Several ground rainfall data obtained from Automatic Rainfall Recorder (ARR) have been adopted to analyze the aforesaid radar rainfall information, and estimated errors between the two are presented. Evaluation of the radar estimated error value as a function or range is taken through a Fractional Standard Error (FSE) index that quantifies the differences between ground rainfall measurement (G) and radar rainfall estimation (R), also the G/R ratio characteristics. The result shows there was a poor correlation between radar estimated and rain gauge measured rainfall located over 14 km from radar. Radar bias (M) is suitable for correcting radar rainfall amount, yet inappropriate for fractional values.

Flash Flood Disaster in Huamual District, West Seram Regency, Maluku Province, Indonesia, Its Potential and Management

Huamual District which is located in west peninsula of Seram Island within Ambon Province is one of the under developed areas since its remote location and limited transport facilities from its regency capital and other developed areas. Therefore, the development program for that area needs to be boasted and secured. One of drawback of the economic development growth in Huamual District caused by current frequent flash flood disaster occurrences. Therefore, disaster resilient of both the local government and communities need to be strengthened. The Provincial Disaster Mitigation Agency of Maluku points that Huamual District was the most severe hit area by flash flood in Maluku beside Ambon City areas in 1^(st) August 2012. In order to prepare a program for increasing disaster resilient in that area, investigation of the disaster risk condition along the west coast of Huamual Peninsula within Huamual District has been conducted and reported in this paper. Reference study has been conducted followed by a field survey in the period of July 14^(th) to July 19^(th) 2014. The field survey was conducted on several sub-villages such as Nasiri, Mange-mange, Amaholu Losi, and Hatawano. The activities in the field survey were secondary data collection, interview to Local Disaster Management Agency (BPBD) of West Seram Regency staffs, to sub-village leaders, to local community members, visual observation survey and river bed material sampling. This paper discusses disaster risk aspect found in the areas which consists of hazard, vulnerability, capacity and also mitigation aspect which consists of pre-disaster, disaster response and recovery phases. The results of this study are the following six findings. 1) The flash flood is the main cause of the natural disaster beside landslide. 2) Although the community settled in the prone area, they do not have knowledge about disaster mitigation but now, they are more aware. 3) BPBD in West Seram Regency has no yearly program related to capacity building, standard operating procedure, and disaster mitigation plan due to limited budget on local government budget and limited employee although 2 years of its establishment. 4) There is no community preparedness dealing with any kind of natural disaster except for their experiences in facing the past disaster. 5) The community still relies on their own members when facing any disaster response. 6) In recovering their sub-village condition the community relies on gotong royong spirit an Indonesian indigenous spirit of working together and also on their own resources.

Development of Debris Flow Early Warning System for Volcanic Rivers at Mt. Merapi Area

The 2010 Mt. Merapi eruption has produced approximately 140 million m3 of pyroclastic deposit, in which more than ten million m3 deposits are potential to move downstream through Boyong/Code River towards Yogyakarta City. The flow behavior of Code River may be affected by the presence of accumulated sediment at the upstream of the river (namely Boyong River). By rainfall trigger, this potential source can cause debris flow disaster that may contribute damage to the settlement areas in Yogyakarta City. This paper presents the development of early warning system to mitigate the impact of debris flow disaster along Boyong/Code River as revealed by most adaptive, least cost, and collaborative-based technology. The system was developed by considering the community aspiration in determining the types and placement of monitoring equipment, and maintaining its sustainability.