Proceedings of the IConSSE FSM SWCU 2015, pp. SC.55–60 ISBN: 978-602-1047-21-7
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Meteorological analysis of the Banjarnegara Landslide on 12 December 2014
Suaydhi and Bambang Siswanto
Center for Atmospheric Science and Technology PSTA, LAPAN, Jl. dr. Junjunan 133, Bandung 40173, Indonesia
Abstract
Hydro-meteorological disasters, such as floods and landslides, occur frequently in Indonesia. In the case of landslides, there are controlling and triggering factors. This paper
analyzes the meteorological condition, which is the controlling factor to a landslide event. Observations and simulated data are used to analyze the meteorological condition prior
the landslide event that occurred in Banjarnegara on 12 December 2014. This event took many casualties because there was no warning system available. The results of the
analysis showed that prolonged heavy rainfall occurred days before the landslide event. Cumulonimbus clouds were also observed around Central Java. This cloud can be used as
indication of heavy rainfall. However, observation of clouds can only valid for a very short time. Longer and at frequent interval weather forecasts are needed to see if the rainfall
persists and has enough intensity to trigger a landslide. The analysis of this paper showed that a numerical model can simulate rainfall event considerably well. Therefore,
simulation of rainfall forecast for 24 hours ahead from a numerical model can be used as early warning system to mitigate the impact of a landslide event.
Keywords Banjarnegara, cloud, early warning system, landslide, model, rainfall
1. Introduction
A concise definition of landslide is the downward and outward gravitational displacement of slope-forming materials Gutierrez et al., 2010. A more comprehensive
definition of landslide, according to Agliardi 2012, is the mass movement of rock, soil, or debris material forming a natural or man-made slope towards the lower and external part of
the slope, along a defined sliding surface. From the latter definition, it can be inferred that causes of landslides can be generally categorized into natural and anthropogenic factors. The
natural factors include gravity, geological factor, meteorological factor, earthquakes, forest fire, volcanoes, and waves Cruden Varnes, 1996. The anthropogenic factors could be in
the form of inappropriate drainage system, cutting and deep excavations on slopes, and change in slope land use pattern. The geological factor which describes the conditions of the
Earths surface can be considered as the controlling factor. The meteorological factor, which refers to events happening in the atmosphere, can be considered as the triggering factor.
Both factors are important in the event of landslide.
Landslides mostly occur in rainy season in Indonesia, where there are a lot of heavy and prolonged rainfall. Landslide is a type of hydro-meteorological disasters. Between 2003 and
Corresponding author. Tel.: +62 878 2135 8934; E-mail address: suaydhilapan.go.id
Meteorological analysis of the Banjarnegara Landslide on 12 December 2014
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2005 more than 50 of about 1429 disasters in Indonesia are related to hydro-meteorology, with landslide accounting for 16 Bappenas Bakornas PB, 2006. Therefore, analysis of the
meteorological factor on a landslide event is as important as analysing the geological factor. An accurate prediction of the weather on sites that are prone to landslide can save property
as well as human lives considerably.
Banjarnegara is surrounded by mountains and hills. The area has high rainfall records, especially during the rainy season. These features make Banjarnegara vulnerable to
landslides. There have been 22 landslide events in Banjarnegara between 2005 and 2014 Firdaus, 2014. The latest landslide in Banjarnegara is one of many such events in Indonesia
that had many casualties. A landslide event is difficult to predict. One way to mitigate the impact of a landslide is to identify the meteorological condition, as variations in rainfall and
potential evaporations control indirectly control the initiation and movement of a landslide occurrence Coe Godt, 2012. In Sipayung et al. 2014, landslide is triggered by the rainfall
accumulation 15 days and 3 days before the event. This paper presents the analysis of the meteorological condition before the landslide in Banjarnegara that occurred on 12 December
2014.
2. Data and method
