Probabilistic landslide susceptibility analysis and verification using GIS and remote sensing data at Penang, Malaysia

The aim of this study is to generate and evaluate the landslide hazard map for Penang Island using a Geographic Information System (GIS) and remote sensing techniques. Landslide locations were identified in the study area from imagery and aerial photograph interpretations followed by field surveys. The topographic and geologic data and satellite images were collected, processed and constructed into a spatial database using GIS and image processing. The factors that influence landslide occurrences such as topographic slope, topographic aspect, topographic curvature and distance from drainage were retrieved from topographic database whereas, geology and distance from lineament were retrieved from the geologic database; land use from TM satellite images and vegetation index value from SPOT satellite data. Landslide hazard areas were analysed and mapped using the landslide occurrence factors by probability - likelihood ratio method. Several areas are considered as hazardous, such as Paya Terubung, Bukit Relau, Bukit Gemuruh and Teluk Bahang. The results of the analysis then were verified using the landslide location data. The validation results showed satisfactory agreement between the hazard map and the existing data on landslide location. Abstrak: Tujuan kajian dijalankan adalah untuk menjana dan menilai peta bencana tanah runtuh dengan menggunakan kaedah Sistem Maklumat Geografi (GIS) dan remote sensing. Data lokaliti tanah runtuh diperolehi dan dikenalpasti hasil interpretasi data-data satelit, foto-foto udara dan juga maklumat kerja lapangan. Data-data topografi, geologi dan juga imej-imej satelit pula dikumpul, diproses dan dijana dengan menggunakan GIS dan kaedah pemprosesan imej serta disimpan di storan database. Peta-peta parameter seperti peta cerun, peta aspect, peta bentuk cerun serta peta jarak daripada sungai dijanakan daripada database topografi manakala peta geologi dan peta jarak daripada lineamen dijanakan daripada database geologi. Disamping itu pula penggunaan data-data satelit menghasilkan parameter­ parameter seperti peta nilai indeks tumbuhan yang diperolehi daripada data satelit SPOT dan peta guna tanah hasil interpretasi ke atas data satelit Landsat TM. Kesemua peta-peta parameter tersebut dianalisa dengan menggunakan kaedah kebarangkalian likelihood. Hasil pengkelasan jumlah kebarangkalian kesemua peta parameter tersebut menghasilkan peta bencana tanah runtuh. Di antara kawasan-kawasan yang dikenalpasti sebagai kawasan berpotensi tinggi bencana tanah runtuh ialah Paya Terubung, Bukit Relau, Bukit Gemuruh dan Teluk Bahang. Analisa selanjutnya mendapati bahawa kejituan peta bencana tanah runtuh yang dihasilkan ini adalah tinggi.