Investigating Relationships Between Australian Flooding and Large-Scale Climate Indices and Possible Mechanism

Flooding is one of the most severe natural disasters in Australia. While flood spatial and temporal variability in the Australian continent has been well documented in the literature, the relationship between seasonal flood magnitude and frequency (FMF) and climatic driving forces influence, and the possible physical mechanism behind the relationship remain unclear. This study attempts to quantify relationships between four climatic indices (Nino-Southern Oscillation [ENSO], Indian Ocean Dipole [IOD], Interdecadal Pacific Oscillation [IPO], and Southern Annular Mode [SAM]) and seasonal FMF across 413 unregulated Australian catchments during 1975-2010. Results indicate that the climate indices have noticeable impacts on flood variability across Australia. Specifically, ENSO plays a dominant role in influencing summer and spring flood variability. However, IOD and IPO tend to have larger effects on autumn and winter floods, respectively. Relationships between the climate indices and FMF can be well interpreted by atmospheric circulation related to the dominant climate index. Our results provide relevant information for flood risk management and have implications for mitigating flood hazards.