Landslide vulnerability assessment based on entropy method: a case study from Kegalle district, Sri Lanka

The concept of landslide vulnerability to a given location is hard to quantify. Few studies have been carried to determine susceptibility using social and physical factors. This study is the first attempt in Sri Lanka to quantify level of vulnerability by integrating major physical and social indicators to map the spatial distribution of vulnerability. Considering the limitations of traditional weight evaluation method in calculation of the multiple indicators and ignorance of the associations among evaluating indicators, a new weight evaluation process, entropy method was introduced in this study. This improved method for determination of weight of the evaluating indicators was applied to estimate weight for the 14 selected indicators. The primary data were obtained from a comprehensive questioner survey (n = 402) of households or buildings (elements) with their coordinates based on a spatially balanced approach for ensuring spatial coverage of the entire landslide distribution. The spatial distribution of vulnerability was mapped using Kriging interpolation. According to the map, landslide vulnerabilities in the study area demonstrate notable regional specifications. Besides, the spatial distribution of vulnerability has shown a close relationship with rural and urban settlements. Results of spatial vulnerability reflect discrimination and inequalities in the development of the study area. According to landslide vulnerability analyses, 14.6% (247 km2) of the entire area is found to be the highest vulnerable zone for a landslide and 39.8% (675 km2) of area categorized under the lowest zone to vulnerability. Further, the study revealed a reasonable contribution by entropy method on analysis of social and physical indicators, which is useful for other vulnerability assessments.