Bari, M.A.; Amirthanathan, G.E.; Woldemeskel, F.M.; Feikema, P.M. Changes in Magnitude and Shifts in Timing of Australian Flood Peaks. Water2023, 15, 3665.
Bari, M.A.; Amirthanathan, G.E.; Woldemeskel, F.M.; Feikema, P.M. Changes in Magnitude and Shifts in Timing of Australian Flood Peaks. Water 2023, 15, 3665.
Bari, M.A.; Amirthanathan, G.E.; Woldemeskel, F.M.; Feikema, P.M. Changes in Magnitude and Shifts in Timing of Australian Flood Peaks. Water2023, 15, 3665.
Bari, M.A.; Amirthanathan, G.E.; Woldemeskel, F.M.; Feikema, P.M. Changes in Magnitude and Shifts in Timing of Australian Flood Peaks. Water 2023, 15, 3665.
Abstract
We analysed changes in magnitude and timing of the largest annual observed daily flow (Amax), in each water year, for 596 stations in high-value water resources catchments and flood risk locations across Australia. These stations are either included in the Bureau of Meteorology's Hydrologic Reference Stations, or used in its operational flood forecasting services. Monotonic trend (which are either consistently increasing or decreasing) analyses of the magnitude and timing of flood peaks (estimated using Amax) were performed using Theil-Sen and Mann-Kendell approach and circular statistics to identify strength of seasonality and timing. Regional significance at the drainage division scale was analysed using the Walker test. Monotonic decreasing trends in Amax flood magnitude were detected in the Murray-Darling River basin and in other drainage divisions in Victoria, south-west and mid-west of Western Australia and South Australia. No significant obvious pattern in Amax magnitude was detected in northern Queensland, coastal NSW, central Australia and Tasmania. Only the Tanami-Timor Sea Coast drainage division in northern Australia showed monotonic increasing trends. Monotonic trends in Amax magnitude were regionally significant at the drainage division scale. We found two distinct patterns in flood seasonality and timing. In the northern and southern parts of Australia, flood peaks generally occur during February to March and August to October, respectively. The strength of this seasonality varies across the country. Weaker seasonality was detected for locations in the Murray-Daring River basin, and stronger seasonality was evident in northern Australia, south-west of Western Australia, South Australia, Victoria and Tasmania. The trends of seasonality and timing reveal that in general, flood peaks are occurring later in the water year in recent years. In northern Australia, flood peaks are generally occurring earlier – at a rate of 12 days/decade. In Victoria, New South Wales and Tasmania, trends in timing are generally mixed. However, in the south-west of Western Australia, the largest change in timing was evident – with Amax peaks commencing later at a rate of 15 days/decade. Decadal variability in flood timing was found at the drainage division scale as well. Most stations show a decreasing trend in Amax magnitude, but how that trend is associated with the change in timing is not clear.
Keywords
flood peaks; seasonality and timing; monotonic trends; annual maxima; Mann-Kendell tests; walker test; Australia
Subject
Environmental and Earth Sciences, Water Science and Technology
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
