Proposal of a method for assessing combined flood risk reduction effect by hazard control measures and exposure reduction measures based on limited data

This article verifies the applicability of an assessment method on flood risk reduction, combining and assessing hazard control measures and exposure reduction measures together. The method develops collated flood risk curves and uses limited data, so it is an approach which can be readily applied in developing countries, where an understanding of flood risk reduction measures are become increasingly important. The method was proposed as a result of studies conducted by the National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure, Transport and Tourism, Japan. When applying the method to a river improvement and relocation scheme with land mounding in Mindanao, the Philippines, the advantages and limitations of the method are considered.

The authors presented the flood risk reduction effect by the project, and the results were in agreement with questioner survey results conducted by JICA after the project. The method seems useful for assessing combined flood risk reduction effect of hazard control measures and exposure reduction measures in the field in the cases where flood hazard maps for multiple scales of flood, population or asset data of each area with area boundary data, and general open access satellite image are available. But, the method is not applicable for evaluating cost–benefit ratio of a project. In addition, the method is not applicable to the case where flood risk transfer from upstream to downstream is not negligible. Besides, the applicability of the method is examined only for river improvement and relocation project with land mounding in this article.