Landslide Vulnerability and Risk Assessment: A Study at Kiriketioya and Belihuloya Watershed

Abstract

Sri Lanka is a continental island consisting of 65,610 km2 of land. The country is highly likely to affect by both natural and man-made hazards. Landslides can be identified as one of the major natural hazards. As a developing country, it is very important to identify landslide vulnerability and risks because that can influence future development activities and disaster mitigation programmes. Kiriketioya and Belihuloya watershed areas are located in the second and third pen plain of the country. It belongs to the Imbulpe Divisional Secretariat Division and approximately covers 72km2 of land. The main objective of the study is to identify the landslide vulnerabilities and risks in the study area. The study was based on the data collected from both primary and secondary sources. Secondary data and information were collected through many sources as an extension to the literature review. Primary data were collected through field observations. Arc GIS 10.3 software was used for digitizing, modelling, data analysis and interpretation. Landsat 8 OLI/TIRS (30m resolution) satellite images were used to calculate Normalized Different Vegetation Index (NDVI) and to analyze the land-usage. Weighted overlay methods in Arc GIS was used mainly to create landslide vulnerability map and the risk map. Landslide vulnerable and risk areas were identified and classified into high, medium and moderate zones. Areas of high risk of landslides are located in the high elevation areas. Approximately 60% of the lands of the study area have a moderate to high risk for landslides. Hence, it is essential to implement mitigatory measures to reduce landslide risks for the high and moderate landslides vulnerability lands.