Dr Jasmine B.D. Jaffres1, Dr Chris Cuff1, Dr Cecily Rasmussen1
1C&R Consulting, Townsville, Australia
Planning and mitigation measures often assume that flood risk remains mostly invariable over time. Variations are mostly expected on a seasonal scale, although La Niña events are known for their greater tendency of above-average rainfall in many Australian regions. For this study, the historic flood events in the Fitzroy Basin (Queensland) were evaluated, focussing on the near-coastal city of Rockhampton. By accessing a wide range of historic records from 1859 to 2018, 56 streamflow events were identified that resulted in minor to major flooding in the city. Approximately 91% of these events were possibly related to tropical cyclones. When cross-referencing these incidences with the El Niño – Southern Oscillation (ENSO) pattern, a significant bias towards La Niña events or La Niña-transition periods was revealed. Consequently, flood risk is substantially higher during these phases, while threat during an El Niño or neutral stage is significantly reduced. Therefore, a greater emphasis towards flood prevention measures is recommended during La Niña events and associated transition periods.
Dr Jasmine Jaffrés is a natural systems analyst with C&R Consulting, a small, Townsville-based environmental consulting firm. Jasmine specialises in data quality, climatology and extreme weather events.