Development of a risk assessment methodologyfor landslides in Sri Lanka

Abstract

The central hilly areas of Sri Lanka underlaid by highly folded and fractured metamorphic rocks of different grades of weathering have a high probability for landslides. Intense precipitation is a major factor contributing to the landslides. Despite repeated occurrences of landslides in Sri Lanka inflicting losses in terms of life and property, very little has been done towards introducing scientific practices for delineating the degrees of hazard, identifying elements at risk, and landslide risk assessment. A National Building Research Organisation (NBRO) has already commenced production of landslide hazard zonation maps (1 : 10,000) covering the areas prone to landslides. The proposed methodology for risk assessment in this paper will facilitate determination of risk through scientific analysis of landslide hazards in future. The demonstration of method was based on a case study carried out at Yatiyantota in Kegalle district. The expected annual total risk cost due to landslide disaster at specific site and/or annual risk cost on specific element at risk (property or person) could be calculated through the given methodology. It may assist in the designing of cost effective solutions and mitigation actions for the area It is also expected to help non-technical decision-makers to assess the situation before taking appropriate futuristic measure. This methodology may be used for assessment of the risk at any specific site in landslide-prone areas in Sri Lanka. Assessment of risk before commencement of major infrastructure development projects and establishment of human settlements in landslide-prone areas based on the risk criterion will be essential for sustainable development of the central hills of Sri Lanka.