Scaling relationships between catchment area and peak discharge across the Fitzroy Basin, eastern Australia

Specific discharge – the flow rate per unit catchment area – highlights the spatial variability of rainfall–runoff events. These events rarely affect entire catchments uniformly, particularly in large river systems such as the Fitzroy Basin in eastern Australia. Using peak historical flow rates from 136 stream gauges, this study evaluates log–log scaling relationships between catchment area and specific discharge across the entire basin and nine major, nested subcatchments. The site-specific historical peaks across such a large and hydrologically diverse basin are used to assess how scaling behaviour varies with operational record length, rainfall extent and subcatchment characteristics. Peak specific discharge exhibits a strong inverse relationship with catchment area, consistent with power-law scaling. However, this relationship is more robust for gauges with longer operational records. Short operational periods reduce the likelihood of capturing rare, high-magnitude flow events and can substantially weaken scaling regressions. The analysis identifies specific gauges that exert disproportionate influence on the fitted exponents, offering practical guidance for gauge selection in future scaling and flood-frequency studies. Accurate estimation of extreme flows is further complicated by highly complex, non-stationary riverbed cross-sections, with some floodplains spanning several kilometres, reducing the reliability of rating curves during major floods. Improved characterisation of peak specific discharge enhances the predictive capacity for extreme flow rates, particularly under projected increases in atmospheric moisture that are likely to amplify peak flows during extreme rainfall events.

Journal of Hydrology

Journal of Hydrology

675

0022-1694

N/A

N/A

12