Book excerpt: Flooding is one of the most frequent and severe disasters in Hoi An City. The analysis of flood events in Hoi An revealed the impacts of flooding on many aspects of human life in this area including severe health risk. However, through literature review, the research showed that few studies about health risk assessment were performed in Vietnam in general and in Hoi An City specifically. Therefore, assessment of the health risk due to flooding is conducted in this research. The goal of this study is to develop a method to assess human health risk due to flooding with a focus on communicable diseases. It also aims to reduce health risk due to flooding by exploring areas that are most at risk. The methodology consists of (i) creating the health susceptibility map based on the Health Susceptibility Index (HSI); (ii) integration of health susceptibility with exposure information into vulnerability information; (iii) spatial analysis of health risk by the combination between health vulnerability and flood hazard information; (iv) evaluating the research results with the incidence of diseases in reality. The health risk map is the first holistic map of its kind for defining the spatial distribution of risk areas in Hoi An City.