Qualitative Flood Risk assessment for the Western Province of Sri Lanka

Abstract

The Western Province of Sri Lanka, is comprised of the 03 most densely populated districts, and is home to the administrative and business capital of the country. The Province contributes the highest share, around 41.2%, to the GDP. The mega scale development projects implemented in this province are often challenged by urban flooding, which is caused by heavy rainfall coupled up with urban expansion, deficiencies in the drainage systems, insufficient retention capacity etc., and there is a prioritized need to reduce the impact of floods. This paper presents the results of a qualitative flood risk assessment at the scale of Grama Niladhari (GN) Division, which is the lowest administrative unit in the country. The essence of the method applied for delineating the combined flood risk levels is a statistical expression of hazard, exposure and vulnerability. Three types of vulnerabilities, namely, social, economic, and physical (housing), have been considered. The results influence to conclude that the flood risk of population is more sensitive to economic vulnerability than to social vulnerability; also that the type of housing units is a reasonable indicator for assessing the risk of housing. The application of risk information in the decision making process reduces the future flood risk as it allows integration of flood mitigation options during development planning, reduce the vulnerability of population and allocate sufficient funding for relief and rehabilitation.