Landslide vulnerability and risk assessment :: From geomorphological mapping to object based image analysis (OBIA) in Kayangan catchment Kulon Progo Yogyakarta Special Province

SAMODRA, Guruh, Prof. Dr. Junun Sartohadi, M.Sc

2010 | Tesis | S2 Geografi

Tujuan dari penelitian ini adalah untuk mempelajari kondisi geomorfologi, mengidentifikasi kerawanan tanah longsor, menilai kerentanan tanah longsor dan menilai risiko tanah longsor di DAS Kayangan. Beberapa metode digunakan dalam mempelajari risiko tanah longsor di DAS Kayangan. Interpretasi manual fusi citra SPOT 5 pankromatik dan multispectral digunakan dalam pemetaan geomorfologi terkait dengan deteksi, pengenalan dan identifikasi bentuklahan. Peta geomorfologi terdiri dari informasi morfologi, morfogenesa, morfokronologi dan morfoaransemen. Aplikasi teknik heuristikstatistik berdasarkan metode weight of evidence diaplikasikan untuk untuk mengidentifikasi kerentanan tanah longsor. Success rate digunakan untuk memvalidasi peta kerentanan tanah longsor. Teknik survei dilakukan terhadap 151 responden rumah tangga untuk mengidentifikasi pola keruangan tingkat kerentanan tanah longsor di DAS Kayangan. Analisis citra berorientasi obyek (OBIA) dan Knowledge based GIS ancillary data menggunakan analisis pola keruangan diaplikasikan untuk mengekstrapolasi tingkat kerentanan tanah longsor pada seluruh blok permukiman di DAS Kayangan. Penilaian risiko tanah longsor kemudian dianalisis berdasar tingkat kerawanan dan kerentanan. Hasil penelitian menunjukkan bahwa kondisi geomorfologi DAS Kayangan dapat dibagi menjadi tiga yaitu zone utara, zone tengah, dan zone tenggara. Kondisi morfologi dan aksesibilitas memiliki peranan penting dalam penilaian kerentanan dan risiko tanah longsor di DAS Kayangan. Penduduk yang tinggal di perbukitan dan aksesibilitas rendah memiliki kecenderungan memiliki tingkat ekonomi yang rendah dan tingkat kerentanan tinggi. Kemudian, penilaian kerawanan dan kerentanan tanah longsor digunakan untuk menilai tingkat risiko. Tingkat risiko dapat diklasifikasikan menjadi risiko rendah, sedang dan tinggi. Klasifikasi risiko tanah longsor ini merepresentasikan potensi kerusakan yang ditimbulkan oleh tanah longsor dan kemampuan manusia untuk mengantisipasi bencana tanah longsor Tingkat risiko tanah longsor tinggi memiliki kecenderungan terletak pada kondisi topografi yang curam dan aksesibilitas yang rendah sementara tingkat risiko yang lebih rendah memiliki kecenderungan terletak pada kondisi topografi relatif datar dan aksesibilitas tinggi.

The objectives of this research are to study geomorphological condition, to identify landslide susceptibility, to assess landslide vulnerability and finally to assess landslide risk in Kayangan Catchment. Several methods were used to study the landslide risk in Kayangan Catchment. Interpretation of fused SPOT 5 imagery was applied in geomorphological mapping dealing with detection, recognition, identification and classification of landform. Geomorphology map was represented based on morphology, morphogenetic, morphochronology, and morphoarrangement. Heuristic-statistic based on the weight of evidence method was applied to identify landslide susceptibility. The success rate was used to validate the result of landslide susceptibility map. Therefore, the household survey technique with 151 respondents was applied to derive the spatial pattern of landslide vulnerability. Object Based Image Analysis (OBIA) and Knowledge based GIS ancillary data using spatial pattern analysis were applied in order to extrapolate the landslide vulnerability degree based on the building block in Kayangan Catchment. Thus, landslide risk assessment was analyzed based on the landslide susceptibility and landslide vulnerability. The result of this research shows that geomorphological condition of Kayangan Catchment can be divided into three zones e.g. northern zone, middle and southeast zone. Morphology and accessibility play important role for the landslide vulnerability and risk in Kayangan Catchment. The people living in hilly area and low accessibility were the poor. In consequences, it would increase the vulnerability degree either physical, social or economic vulnerability. Landslide susceptibility and vulnerability assessment were used as an input of risk assessment. Thus, the risk assessment can be classified into low risk, medium risk and high risk. The risk classification represents the potential degree of damage and the capability to cope with landslide disaster. High risk degree of landslide tends to be located in the steep slope and low accessibility, while the low risk tends to be located in the gentler slope and good accessibility.

Kata Kunci : Tanah longsor,Kerawanan,Kerentanan,Risiko,Geomorfologi,OBIA, landslide, susceptibility, vulnerability, risk, geomorphology, OBIA