Geo-spatial approach with frequency ratio method in landslide susceptibility mapping in the Busu River catchment, Papua New Guinea

With the exacerbated kinetic energy of high volume of flowing water, the middle and lower catchment zones of a rugged terrain often become more prone to landslide. Almost half of Lae city, the second largest city in Papua New Guinea falling in the lower end of the catchment remains variably vulnerable to landslides. The study deliberates on the mapping of landslide sustainability, utilizing the geographical data sets such as terrain aspect and slope, land use land cover, site soil-geology, distance from river and distance from existing fault lines as input data for frequency ratio analysis culminating in delineation of susceptible landslide potential zones within the catchment area. The location of previous and recent landslide occurrence zones within the study region were identified and demarcated by dint of high resolution Google earth imagery complimented with the data gathered through field visit. All the thematic layers were prepared and organised for assignment of weights. The calculated frequency ratio values were assigned as weightage to each factor class. By using the weightage sum and raster calculator spatial analyst tool in ArcGIS 10.2.2 the results was generated. The result was then verified with known landslide occurrence and the cumulative % graph was constructed through calculated values. Furthermore the area under curve was calculated and validated with the ground truth information.