Rapid Assessment of Waterlogging Risk Induced by Typhoon Rainfall: A Case Study of Typhoon Haikui (2311) in South China
Typhoon rainfall can trigger urban waterlogging within hours, but hydrodynamic modelling is impractical for rapid screening. For Typhoon Haikui (2311) across Guangdong, Guangxi, and Hainan, we integrated half-hourly Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) Final Run V07 precipitation, LandScan population exposure (E), and an impervious-surface factor (I) derived from the China Land Cover Dataset into a Typhoon Rainfall Risk Index (TRRI). Rainfall hazard (H) combines event-total rainfall, rainfall duration, and maximum 3 h rainfall. Hazard clustered along the Guangdong coast, where maximum event-total and 24 h rainfall reached 529.7 and 272.8 mm, respectively. TRRI high-risk zones occupied 12.45% of the three-province land area. Defined by the largest weighted component, H-, E-, and I-dominated cells accounted for 60.5%, 33.4%, and 6.1% of the high-risk class. Of 22 reported waterlogging locations in the event-focused domain, 19 fell in high-risk zones; the 86.36% hit rate versus a 26.09% background area yielded an enrichment ratio of 3.31 (p < 0.001). In a descriptive full-domain check, all 49 distinct locations were medium or high. Relative to H alone, TRRI reclassified 20.59% of land upward and 20.64% downward, while 58.77% remained unchanged. TRRI supports rapid event-scale screening and risk prioritization for targeted disaster-prevention decision-making.