Landslide susceptibility mapping in Mahakam Ulu, East Borneo, by using an MCDA-based factor of safety

Abstract

Landslide hazard mapping has been performed in Mahakam Ulu regency in order to support disaster risk reduction and targeted mitigation efforts. The mapping was done by using topographical slope gradient, soil type, and maximum rainfall intensity data. Maximum rainfall used in this research comprises of daily rainfall data with a 20-years return period, which is assumed to be spatially uniform across the entire region. The slope parameter is calculated based on maximum rate of elevation change between a raster cell and its surrounding cells. Meanwhile, soil type is obtained by combining information from geological maps of Long Iram and Long Pahangai. The aforementioned parameters were used to calculate Factor of Safety (Fs) that indicates slope stability and were integrated using a weighted average-based multi-criteria decision analysis. The resulting Fs values are varied from 0.230-1.500. Low Fs values of 0.230 to 0.738, showing landslide-prone area, can be seen along the northern border between Long Apari and Long Pahangai districts. Areas with low Fs values are also observed along the eastern border between Long Bagun and North Borneo province, the southern part of Long Hubung, and a small area in northern Laham. The Fs values were also used to construct a landslide susceptibility map with three hazard levels: low, moderate, and high. Areas with low level of landslide hazard prevail throughout Mahakam Ulu. Nevertheless, large portion of landslide-prone areas in Long Apari and Long Pahangai point to the importance of hazard risk reduction and targeted mitigation efforts tailored for the mentioned regions.