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.