Conclusion

This study selected 14 bushfire impacted catchments during the 2009 Victoria bushfire event and analysed the effects of the bushfire as well as climate variability on annual streamflow. Relationships between rainfall and streamflow in all catchments have been constructed and evaluated during the calibration period. Then the relationships were applied to estimate the annual streamflow changes due to bushfire in the time-trend analysis method. The calculated streamflow increase due to vegetation change caused by bushfire (ΔQveg) ranges from 1.6 mm (Frenchman Creek Junction) to 125.9 mm (Traralgon South), which illustrates that the bushfire caused an increase in streamflow during the post-fire (testing) period in all burnt catchments. The streamflow changes due to climate variability (ΔQclim) were determined from the sensitivity-based method. The result shows that streamflow changes caused by climate variability in the majority of catchments has relatively smaller proportions of total streamflow change compared with that caused by bushfire. The relationship between burnt percentage and percentage of mean annual streamflow increase due to bushfire was constructed and the results indicate that the percentage increase in mean annual streamflow due to bushfire is linearly related to percentage burnt areas. This relationship can be used to estimate the annual streamflow changes caused by bushfire in small-medium size catchments in Australia.