An emergency-oriented risk assessment method for typhoon storm surge disasters

Abstract. Typhoon storm surge disaster (TSSD) is one of the most severe marine disasters affecting China's coastal areas, and risk assessment plays a crucial role in disaster prevention and mitigation. Existing studies primarily focus on risk zoning and long-term disaster reduction strategies, whereas risk assessment for an imminent TSSD, which is essential for pre-disaster emergency response, remains insufficient. The main challenges lie in quantifying hazard uncertainty and in representing the multiple dimensions of vulnerability. To address these challenges, this study develops an emergency-oriented risk assessment method for an imminent TSSD that integrates ensemble forecasting into a complete risk assessment framework. For hazard assessment, ensemble forecasting techniques are employed to address hazard uncertainty. A controlled scenario is generated by integrating multi-source forecast data, and perturbed scenarios are derived based on historical forecast errors. These scenarios form an ensemble of 15 scenarios for hydrodynamic simulations, with the mean and maximum water depths characterizing the hazard intensity grade. For vulnerability assessment, land use types and densely populated facilities are selected as two categories of vulnerability. The water depth-loss relative grade relationship for 11 land use types is established, and Point of Interest (POI) density is introduced to represent potential casualty vulnerability. Comprehensive risk is calculated by combining the results of hazard and vulnerability assessments. The method is validated through a case study of the Hato TSSD (2017) in Zhuhai, with the forecast initialization time set at approximately 24 hours before landfall. The proposed method can be re-executed to provide dynamic risk assessment updates as forecast data evolve, providing timely support for emergency decision-making.