Flood disaster risk analysis based on variable fuzzy sets theory

Based on the disaster system theory and the consideration of natural properties of hazard and environmental as well as socioeconomics of hazard-affected bodies, the primary risk assessment system and grading standard for flood diversion district were established. Then taking the towns as the basic assessment units, on the basis of variable fuzzy sets theory, the corresponding model for variable fuzzy assessment was established, which could reasonably identify the relative membership degree between the index of assessment unit and its standard interval, thus properly determine the comprehensive assessment grade of each unit by varying the parameters of the model. In this way, the flood hazard grade and flood vulnerability grade for each unit could be calculated, respectively. After that, the flood risk grade for each unit was achieved from flood hazard and vulnerability grade with the flood risk grade classification matrix, which was divided into five grades, i.e. very high, high, medium, low, and very low respectively. Finally, taking the case study in Jingjiang flood diversion district for example, the practical application showed that the method was flexible and its results fitted with the actual situations. The method can also be applied for risk assessment of other natural disasters.