Abstract
Abstract. In a high-rainfall, landslide-prone region in this tropical mountain region, a landslide database was constructed from high resolution satellite imagery (HRSI), local reports and field observations. The landslide data was divided into training (80%) and validation sets (20%). From the digital elevation model (DEM), scanned maps and HRSI, twelve landslide conditioning factors were derived and analysed in a GIS environment: elevation, slope angle, slope aspect, plan curvature, profile curvature, distance to drainage, soil type, lithology, distance to fault/lineament, land use/land cover, distance to road and normalized difference vegetation index (NDVI). Landslide susceptibility was then estimated using the frequency ratio method as applied on the training data. The detailed procedure is explained herein. The landslide model generated was then evaluated using the validation data set. Results demonstrate that the very high, high, moderate, low and very low susceptibility classes included an average of 86%, 7%, 4%, 3% and 1% of the training cells, and 84%, 7%, 5%, 3% and 1% of the validation cells, respectively. Success and prediction rates obtained were 90% and 89%, respectively. The sound output has discriminated well the landslide prone areas and thus may be used in landslide hazard mitigation for local planning.
Highlights
In the Global Landslide Catalog (Kirschbaum et al, 2015), the Philippines and its Asian neighbors are considered landslide hotspots
Located in the Circum-Pacific Ring of Fire and the western North Pacific basin, the Philippines face landslides triggered by earthquakes and high rainfall from tropical cyclones
The results confirm that the frequency ratio (FR) method applied on the twelve factors can adequately model the landslide susceptibility in the area
Summary
In the Global Landslide Catalog (Kirschbaum et al, 2015), the Philippines and its Asian neighbors are considered landslide hotspots. Located in the Circum-Pacific Ring of Fire and the western North Pacific basin, the Philippines face landslides triggered by earthquakes and high rainfall from tropical cyclones. The passage of tropical cyclones and/or southwest monsoon activity coincide with the annual occurrence of rainfall-induced landslides (RIL). Most RIL occur during the months May to October. For the years 1951-2013, an annual average of 19.4 tropical cyclones cross the Philippine area of responsibility (PAR) (Cinco et al, 2016). Predisposing geologic features, together with high rainfall (~ 3892 mm per year) and human activities have placed the area at high risk for landslides and related hazards (NolascoJavier et al, 2015). Among the most damaging landslide events were those during Typhoon Parma in October 2009
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