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Asia-Pacific Network for Global Change Research

Asia-Pacific Network for Global Change Research

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Peer-reviewed publication

Copula-Probabilistic Flood Risk Analysis with an Hourly Flood Monitoring Index

Floods are a common natural disaster, with severity varying significantly across geographical regions in terms of duration, water resource volume, peak, and accumulated rainfall-based damage. This study introduces a novel hourly flood index (SWRI24-hr-S), derived by normalizing the existing 24-hourly water resources index (WRI24-hr-S), to monitor flood risk on an hourly scale. The SWRI24-hr-S is used to identify flood situations and determine their characteristics, including duration (D), volume (V), and peak (Q). Analysis at seven study sites in Fiji (2014–2018) demonstrates the index’s utility in identifying flood situations and extracting their characteristics.

Additionally, a vine copula-probabilistic risk analysis system is developed to model the joint distribution of flood characteristics (D, V, and Q), enabling probabilistic flood risk assessment. This approach introduces a novel probabilistic framework tailored to Fiji’s context. The results highlight moderate spatial differences in the joint exceedance probability of flood characteristics under various scenarios. In the worst-case scenario, the probability of extreme flood events (where D, V, and Q exceed the 95th-quantile) is under 5% for all sites.

The proposed hourly flood index and vine copula approach offer cost-effective tools for flood risk monitoring and assessment, applicable in data-scarce regions reliant on rainfall data. These methodologies provide critical insights for flood risk mitigation strategies.