Temporal Landslide Susceptibility Assessment Using Landslide Density Technique

In this study, a temporal landslide assessment was carried out in a landslide prone areaalong the Ranau-Tambunan road in Sabah, Malaysia. The assessment was based on landslides interpreted from 1978 and 1994 aerial photographs and also from fieldworks which were done in 2009 and 2011. A total of 148 landslides were recorded from those four years with 24, 47, 56 and 21 landslides respectively for the year 1978, 1994, 2009 and 2011. Based on these landslides, a landslide density map was produced for each year which consist of three classes; low (1 landslide/km2); moderate (2-3 landslides/km2); and high (= 4 landslides/km2). Based on the combination of landslides occurred throughout the assessment years, 22 sections of the road were indicated to have high landslide density. Intersection with high lineament density zone shows that 16 of the high landslide density areas are located inside within the high lineament density zone. From both of these maps, a landslide susceptibility map was generated. Landslide records acquired from aerial photographs captured in 2005 was use to validate the map. The validation result shows that 83% of the total landslides in 2005 are within the high susceptibility zone and this value indicates that the accuracy of the susceptibility map is acceptable. The high susceptibility zone in the study area can be categorized as ‘highly susceptible’ with moderate hazard based on the International guideline on susceptibility and hazard zonation. In terms of landslide density, it is expected that 5.4 landslides can be observed for every km2 in the high susceptibility zone. .