Flood risk assessment in Kelantan State, Malaysia based on the weighted integrated spatial evaluation model

Kelantan State, northeastern Peninsular Malaysia, a monsoon-affected region characterized by complex terrain and recurrent flooding. This study proposes a Weighted Integrated Spatial Evaluation for Flood Risk (WISE-Flood) model to improve regional flood risk assessment by addressing the limitations of single weighting approaches and spatial heterogeneity representation. The model integrates the Analytic Hierarchy Process and the Entropy Weight Method to optimize the weighting of 20 indicators covering topographic, hydrological, geological, climatic, and anthropogenic factors. A Flood Hazard Index was constructed and optimized for spatial risk classification. Model performance was evaluated using observed flood events from 2015 to 2022 and Receiver Operating Characteristic analysis. The results reveal a well-defined core–transition–periphery flood-risk structure within the Kelantan River Basin, with high-risk zones concentrated along the lower river reaches, moderate risk in hill–plain transition areas, and low risk in the upstream highlands. Flood susceptibility is primarily controlled by the coupled effects of terrain-driven saturation processes—represented by the Stream Transport Index, Topographic Wetness Index, and Surface Soil Moisture—and human exposure, underscoring the dominant role of hydrological–anthropogenic interactions in monsoon-dominated basins. These region-specific insights advance the understanding of flood generation mechanisms in monsoon river basins and provide a hydrologically informed basis for spatially differentiated flood mitigation, land-use regulation, and basin-scale flood risk management in Kelantan and similar Southeast Asian monsoon regions. • A WISE-Flood model integrating AHP and entropy weighting was developed. • The model was validated against multi-year flood records with 90.6 % accuracy. • Terrain saturation (STI, TWI, SSM) and exposure jointly dominate flood risk. • A core–transition–periphery flood-risk pattern was identified in Kelantan.