Catchment Descriptions and
Data
2.1 Catchment Description
On Saturday 7 February 2009, the state of Victoria Australia experienced
the highest temperature on record with 46.4°C followed by severe
bushfires that burnt an area of over 350,000 hectares and caused 173
deaths, which was the second severest among Australia’s worst natural
disasters (Biondi & De Luca, 2015; Foster et al., 2011). According to
Cai et al. (2009), the 2009 bushfire event was preceded by a positive
Indian Ocean Dipole (pIOD) event more so than El Niño events. More
specifically, the lower rainfall and higher temperatures produced by
pIOD aggravated the dry conditions that finally caused the wide range of
bushfire in Victoria. As a result, around 363 km2 of
forests in the Melbourne water supply catchments (Feikema et al., 2013)
and approximately 24 gauged catchments in Victoria were affected by this
severe bushfire event.
<Figure 1 Here Please>
This study selected 14 unregulated catchments that without major water
storages or extraction for human use burnt during the 2009 Victorian
bushfire. These catchments are located within the southern part of
Victoria, Australia (Figure 1). They are small to medium in size,
ranging from 84.76 km2 to 629.16
km2. Their mean slope ranges from 14.2% to 32% and
their mean elevations range from 273.1 m – 968 m. Soils in these
catchments are characterized by deep gradational friable earths or loams
as well as some shallow stony earths (Feikema et al., 2013), and they
are generally deep with high hydraulic conductivities (Campbell, 1999).
The vegetation types in this area are mainly wet sclerophyll Eucalyptus
forests known as ash-type eucalypt forest dominated by E. regnans F.
Muell. and E. delegatensis R.T (Feikema et al., 2013). More detailed
catchment information is summarized in Table 1.
<Table 1 Here Please>
Apart from the preliminary summary of selected burnt catchment
attributes, detailed various fire severity proportions of total burnt
percentage for burnt catchments were also collected (see Figure 2).
Burnt area in majority of catchments are classified as high fire
severity such as Crown Burn and Crown Scorch, except some lightly burnt
catchments (e.g. Frenchman Ck Jun and Jamieson). Some catchments with
relatively low burnt percentage have more severe burns. For example, the
Murrindindi above Colwells only has 58.9% burnt percentage, but it is
mainly composed of crown burn and crown scorch.
<Figure 2 Here Please>
2.2 Streamflow and meteorological
data
The daily streamflow data used in this study were obtained from the
Australian Bureau of Meteorology
(http://www.bom.gov.au/water/).
The climate data including daily precipitation (P), daily incoming solar
radiation, daily vapour pressure, daily minimum air temperature, and
daily maximum air temperature came from the SILO Data Drill produced by
the Queensland Department of Environment and Resource Management
(https://legacy.longpaddock.qld.gov.au/silo/). The SILO data has
reasonably good quality since its mean absolute error between gridded
and gauged data at gauged locations is 1.0°C, 1.4°C, 0.15 kPa and 0.40
mm/day for maximum daily air temperature, minimum daily air temperature,
vapour pressure, and precipitation, respectively (Jeffrey et al., 2001).
The daily PET was calculated from Morton’s wet environment algorithms
(Morton, 1983). Catchment attributes and boundaries were obtained from a
dataset generated by Zhang et al. (2013). Apart from the above, this
study also used bushfire severity maps obtained from the Victoria
Department of Environment, Land, Water & Planning
(https://www.data.vic.gov.au/data/) with an estimated accuracy of
95%, which are shown in red in Fig 1.