Exploring sustainable watershed flood risks management: an innovative TFAHP-TOPSIS methodology in the Georges River Basin, Australia

Floods occur frequently in low-lying coastal and riverine areas, making it crucial to effectively identify the distribution of flood risks in flood-prone areas. Traditional risk assessment models based on Multiple-Criteria Decision-Making (MCDM) method have limitations in both accuracy and effectiveness, particularly in identifying potential risks in watershed floodplains. To refine the flood measurement process, an optimized integrated MCDM model is proposed in this paper. Taking the Georges River Basin in Australia is chosen as an example, twelve risk indicators were identified, considering factors related to hazard, exposure, and vulnerability. To more accurately describe the characteristics of watershed floods, the flood hazard indicators were separated into sub-basins. The Triangular Fuzzy Analytic Hierarchy Process (TFAHP) is employed to optimize the weight calculation, and in combination with the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), the spatial distribution of flood risks was determined. The results indicate that high-risk areas are concentrated in the central-eastern part of Liverpool, the eastern part of Fairfield, and the central part of Bankstown-Canterbury. Medium to very-high potential risk areas identified by the integrated TFAHP-TOPSIS model are 17.3 % more than the single TFAHP method and 12.7 % more than the TOPSIS method, indicating that the integrated model performs better in identifying potential risks in floodplains. The results can provide decision support for disaster prevention strategies making in flood-prone areas.