Urban risk assessment of lahar flows in Merapi Volcano :: Study case: in Muntilan Area, Central Java, Indonesia

SUKATJA, Cosmas Bambang, Dr. H. Hartono, DEA.,DESS

2007 | Tesis | Magister Geo-Informasi Manajemen Bencana

Penelitian ini dimaksudkan untuk menanaiisa keinwigkinaìi terjadinya banjir lahar di daer.ah urbanMunlilan. Jawa lengah. Dengan mcmadukan beherapa metode. diantaranya dengan program simulasi angka. Sislem GecgmIì Informasi (SIG), Remote Sensing (RS) dan ditambah dengan dala lapangan untuk rnenghasilkan Pela Bahaya dan Peta Risiko liencana Banjir Lahar dan Ciunung Merapi. Daerah urban Muntilan terletak di lereng sebelah barat (runung Merapi dan di huir K. I.arnat. mertipakan sungai laharan yang berhulu dari Gunung Merapi. Sungai tersebut mengalir membelah daerah urban yang saal ini seperti daer.th tainnyn juga mengalami perkembangan. Sehingga banyak warga masyrarakal yang membungun peinukiman bani. bahkan karena terbatasnya dana dan pemahaman bencana tidak sedikit dan mcnka yang mendirikan hangunan pemukimun di hantaran sungai. Maka daerah ¡ni merupakan daerah rawan dan baiijir lahar G. Merapi. Banjir lahar terjadi karena .idanya material endapan volcanik yang berada di hulu sungai ama lereng gunung mengalami kejenuhan akihat disirain air hujan. Banjir lahar yang mempunyni daya rusak tinggi sangat bcrbahaya hagi masyarakat yang tinggal di daerah hUir karena kckuatan banjir dupai menghancurkan tebing sungai yang mcnghalanginya, memporakparandakan pernukiman, strukiur dan infrastrukiur yang dilewatinya seria akhimya menimbunan daerah pemukinmn dan ìsilitas umum lainnya yang hcmda di daerah paling akhir. Hasil penelitian ini meinprediksì bencana hanjir lahar yang membahayakan daerah urban Muntilan akan terjadi pada periode I (M) tahwìan. Hencana banjir Jahar tcrscbut dipetakan dalam Peta Bahaya dan Petit Risiko [‘encima banjir lahar unluk keniudian dipergunakan sehagal perkiraan nsiko yang akan tenjadi nantinya bila banjir lahar icijadi di daerah urban Muntilan.

Lahar flows, also referred to as mudflows, which generally occur during intense rainfall on saturated volcanic deposit in upper stream of river or wall of volcano. Lahar flows are extremely dangerous especially to those living in valley areas near a volcano, which can undercut banks and cause houses destruction situated on the banks, and can bury and destroy structures, infrastructure facilities including roads and bridges. Meanwhile, when the developing of city will be done without good spatial planning caused many illegal settlements appears surrounding that area. Occasionally, un-benefit people constructing house in disaster prone area, such as down stream of river side that have lahar flows risk. Development of Geographic Information System (GIS) and remote sensing technology is incorporation of a set of computer-based tools can make easily for disaster risk assessment. In this case, introduces a new perspective in the lahar flows risk map production, increasing the analysis and modelling capabilities available through the application of a conventional methodology. A methodology adapted to the requirements and characteristics of the new operating environment is applied in Merapi volcano, Central Java, Indonesia. GIS role of lahar flows in urban risk assessment has been the discussed, keeping in mind the selected hazard-level and risk level of lahar flows in the risk area. The research was concluded that lahar flow occurrence in 100 years return period will be buried the Muntilan urban area. And with the methods integrating of GIS, RS, field verification can be done analysing of lahar flows hazard map, and risks map to produce risk assessment in Muntilan urban area.

Kata Kunci : Banjir Lahar,Daerah Urban,Perkiraan Resiko, lahar flows, urban area, risk assessment