Integrated post-earthquake Flood Risk Assessment model for Kota Belud, Sabah

This study has developed a comprehensive integrated post-earthquake Flood Risk Assessment (FRM) model for Kota Belud, Sabah. The area faces increased risk of floods due to rapid development activities and natural disasters, such as the 2015 Ranau Earthquake. The frequent occurrence of floods, compounded by events such as landslides, erosion, and debris flows, particularly after the earthquake, calls for a more systematic risk management approach. Research on the relationship between earthquakes and flood risk is limited in Malaysia. This model considers earthquakes and other external factors in flood management. The proposed FRM involves five key components: Flood Hazard Assessment (FHA) using the Hydrologic Engineering Center’s River Analysis System (HEC-RAS) hydrodynamic model and flood vulnerability indices; identification of Flood Risk Elements (FREI); Flood Vulnerability Assessment (FVA); Flood Risk Analysis (FRAn); and Flood Risk Evaluation and Mitigation (FREv). Results of the FHA map has been validated with an Area Under Curve value of 88% (0.88). The highest density of flood risk elements (FREI) is found near the main rivers, namely Sg. Kadamaian, Sg. Wariu, Sg. Tempasuk, Sg. Abai, and Sg. Gurong-Gurong. The FVAs map shows that a large part of the study area falls under the moderately vulnerable category at 55% (~108.49 km²), with minimal areas in the highly vulnerable category. The FRAn results indicate that areas with high flood hazard and vulnerability levels also have high flood risk levels, such as in Padang Pekan, Kg Lilud, Kg Sangkir, Kg Jawi-jawi, Kg Kota Bunga, Kg Limatok and Kg Tamau, and vice versa. The FREv reveals that the preparedness and resilience levels of residents need to be improved.