Flood Risk Assessment in Asian Flood Prone Area with Limited Local Data – Case Study in Pampanga River Basin, Philippines –

Abstract

Disaster risk assessment is vital to determining needs for disaster countermeasures and promoting their implementation. However, it is difficult to conduct evidence-based risk assessment in flood-prone areas of Asia due to area-specific characteristics such as limited local data on natural and societal conditions and local lifestyles of persons who have adapted to frequent floods. This paper proposes basic flood risk assessment considering these characteristics and explores a case study conducted in a flood-prone area of the Pampanga River basin in the Republic of the Philippines to verify our method. We surveyed local household members as part of the study to understand local situations, finding that past flood damage cost little thanks to building structures adapted to frequent flooding and to local ways of protecting property during floods. We also found that the use of depth-damage curves developed for urban areas may overestimate anticipated damage expected in future floods when these curves are applied to flood-prone rural areas. For this reason, we propose a method of flood risk assessment for evaluating the societal impact on residents’ lives using observed thresholds of inundation depth by flood simulation, rather than using a method that estimates damage cost. Application of our proposal to the case study area confirmed its applicability and effectiveness in evidence-based planning for reducing flood risk.