The Study Area is located within the Swan Coastal Plain region in the South-West of Western
Australia, near the border of the Northern Sandplains region. The area experiences a dry,
warm Mediterranean climate with predominantly winter rainfall (300 – 500 mm) and seven to
eight dry months per year (Beard 1990). The long term average precipitation for Dandaragan
West (approximately 15 km east of the Cooljarloo minesite) is 604.3 mm (years 1953 –
2012); mean yearly rainfall at this station has not exceeded the mean in the years 2000 – 2012
(Bureau of Meterology (BOM) (2013).
Figure 2 displays average monthly maximum and minimum temperatures, and average
data), recorded for Cooljarloo West (Tronox 2013a). The highest average maximum
temperature at Cooljarloo West occurs in January and February (approximately 34
C). The average
from May to August with July receiving the highest level of rainfall (109.3 mm).
Max. Temp. °C
Min. Temp. °C
The Study Area is located within the Perth Basin, which extends from the Murchison River to
the south coast of Western Australia, and is defined on the eastern boundary by the Darling
Fault, with the western boundary lying under the continental slope. The Perth Basin contains
a Silurian to Pleistocene sedimentary succession. According to Mory and Iasky (1996), the
onshore Perth Basin is divided into 13 structural units, with the Study Area occurring on the
Cadda Terrace and the Coomallo Trough units, which lie to the west of the Eneabba Fault.
Much of the Perth Basin is mantled by Quaternary deposits, up to 75 m in thickness,
dune sands, lake and swamp deposits, alluvium and colluvium (Playford et al. 1975). The
Study Area is located on the Swan Coastal Plain physiographic unit, which is comprised of
four north-south oriented systems; the Study Area located on the Bassendean Dune System
(Mory and Iasky 1996). The Bassendean Dunes represents a belt of coastal dunes and other
associated shoreline deposits with local concentrations of heavy-mineral sands, the
identification of which from surface features is virtually impossible (Mory and Iasky (1996).
This system is composed of Bassendean Sands, which are almost completely leached of
calcium carbonate, represented by subdued hummocks of quartz sand with intervening
swamps (Playford et al. 1975).
Figure 3 displays the approximate Study Area boundary atop the Dongara Hill River
Bassendean Sand comprising ancient coastal quartz-sand dunes, scattered with areas of
swamp and lacustrine deposits of sand, clay and diatomite. A small section in the south-east
of the Study Area consists of alluvium with sand, silt and clay with the very north-east corner
consisting of colluvium with quartz sand. Small areas of ferruginous laterite are also present
in this section of the Study Area. The south western corner of the Study Area is comprised of
coastal limestone covered by residual quartz sand with occasional patches of eolian limestone
and kankar (Lowry et al. 1969).
At Cooljarloo West, the main stratigraphic units in terms of influence on vegetation are the
between 1 – 3 m in thickness, consisting of very fine to coarse grained, well sorted quartz
sand with some organic material; seasonal wetting and perching was indicated by moisture
recorded in the sandy horizons as well as the presence of mottled clays at the base of this unit
(Worley Parsons 2013). This layer is underlain by the Guildford Formation, which consists of
blue-grey to brown silty to slightly sandy clay, which can be separated into an upper clayey
facies (maximum thickness 27 m) and a lower sandier facies (nominally to 22 m thickness)
(Worley Parsons 2013). The upper clay facies acts as an aquitard, with a perched water table
above this unit; however, although the permeability of the clay facies is generally low, there
are areas with significantly higher hydraulic conductivity where sandier portions of the
Guildford Formation occur (Worley Parsons 2013); these sand lenses may form an important
function in terms of soil moisture availability for vegetation (Syrinx 2013).
The vegetation of the region was initially mapped at a broad scale (1:250 000) by Beard
during the 1970’s. This dataset has formed the basis of several regional mapping systems,
including physiographic regions defined by Beard (1979); the biogeographical region dataset
(IBRA) for Western Australia (Department of the Environment (DoE) 2013a); and vegetation
system associations which are currently used to determine extents of clearing since European
arrival (Government of Western Australia 2013).
2.3.1 Regional Vegetation Mapping by Beard (1979; 1990)
The Study Area is located in the Drummond Subdistrict of the Darling Botanical District
(Swan Coastal Plain Subregion) (Beard 1979), the northern boundary of which is the northern
limit of Banksia Low Woodland (Beard 1990). It traverses four physiographic systems within
this subdistrict: the Bassendean, Guilderton, Jurien and Lesueur Systems (depicted in Figure
5). The Study Area is comprised predominantly of the Bassendean System with small areas
of the Guilderton and Jurien Systems in the south-west and the Lesueur System in the north-
east and south-east, reflecting the geological composition described in Section 2.2.
The Bassendean System is a flat undulating plain with low ridges of bleached sand
woodlands are dominant, with trees ranging from 3 – 6 m in height. Beard noted that in the
Banksia Low Woodlands there was considerable consistency in the overstorey, but less so in
the understory (pg. 34, Beard 1979). The swampy areas give rise to heaths of a mix of species
including Acacia lasiocarpa, Melaleuca acerosa, Banksia telmatiaea, Calytrix aurea, Calytrix
flavescens, Verticordia densiflora and Verticordia drummondii. Samphires and Frankenia
spp. are found within salt pans, whereas deeper swamps typically consist of woodlands of
The Guilderton System features the recent sand dunes of the coastal belt and is the northern
sands succeeded by thickets of Acacia cyclops. In areas with frequent burning the vegetation
is typically heath or low scrub dominated by Acacia lasiocarpa and Melaleuca acerosa. On
flats and interdunes the vegetation climaxes to thickets of Allocasuarina lehmanniana and on
salt flats saltbush, samphire and Melaleuca thyoides are dominant. Unvegetated drift sands
are a feature within the Guilderton System (Beard 1979).
The Jurien System is located within the older coastal limestone belt and is the northern
Banksia Woodlands on deep white sands and stunted Eucalyptus gomphocephala in
depressions (Beard 1979).
The Lesueur System includes prominent breakaway slopes (up to 100 m high) and flat-topped
colluvial sand and gravel with some areas of yellow, sandy clay over weathered sandstone.
The vegetation is dominated by Low to Moderate Heath of Banksia attenuata, B. menziesii
and Eucalyptus todtiana, up to 2 m high on the mesas and up to 0.5 m on slopes and
breakaways. Drainage channels and gullies ranging from coarse-sand to yellow (mottled)
sandy-clay soils support low heath with a diverse range of dominant species including
Beard mapped the phytogeographic regions of Western Australia based on natural
delineations in vegetation and landscape, divisible into regions and further broken down in to
Botanical Districts. The boundaries of Western Australia’s IBRA (Interim Biogeographic
Regionalisation for Australia) regions are broadly compatible with those of Beard’s
phytogeographic regions. Figure 4 presents the location of the Study Area in relation to the
The Study Area is located in the northern extent of the Swan Coastal Plain IBRA Region,
Subregion is characterised by colluvial and aeolian sand, alluvial river flats and coastal
limestone, with vegetation generally featuring heath and/or Tuart Woodlands on limestone,
Banksia and Jarrah-Banksia Woodlands on Quaternary marine dunes, and Marri on colluvial
and alluvials, and includes a complex series of wetlands. Within this subregion there are areas
of a high degree of ecosystem and species diversity, notably on the eastern side of the coastal
plain. It has also been noted that although there has been quadrat-based floristic survey
throughout the subregion, the floristics of the northern half of the subregion has not been as
well surveyed as the southern half, and a systematic and consolidated analysis of floristic data
is required throughout (Mitchell et al. 2002).
The SWA02 Subregion is bordered by the GES02 – Lesueur Sandplain Subregion to the
Subregion further to the east/north-east (DoE 2013a; Beard 1979). GES02 contains mainly
proteaceous scrub-heaths (kwongan) which are rich in endemics on undulating lateritic
sandplain, and exhibits high floristic endemism (Desmond and Chant 2001). SWA01 is
characterised by Banksia Low Woodland, Jarrah-Marri Woodland and Marri Woodland and
Scrub-heath on laterite pavement and gravelley sandplains (Desmond 2001).
2.3.3 Vegetation System Associations
Shepherd et al. (2002) mapped and described vegetation system associations related to
physiognomy, expanding on mapping originally undertaken by Beard (1979), at a scale of
1:250,000. These vegetation system associations were further refined in 2012 (Government
of Western Australia 2013). The Study Area traverses five such vegetation system
associations as presented in Table 1 and in Figure 5. Table 1 also presents the current extent
of each vegetation system association in relation to the pre-European extent, and the extent
within Department of Parks and Wildlife-managed (DPaW) lands (formerly Department of
Environment and Conservation), including conservation reserves.
Low Woodland; Banksia attenuata &
Shrublands; Dryandra (now Banksia)
Mosaic: Shrublands; Acacia rostellifera,
Melaleuca acerosa heath
Jurien – 1029
Bare areas; drift sand
Mosaic: Shrublands; Hakea Scrub-heath /
Shrublands; Dryandra (now Banksia)
A 30 % threshold level as the proportion of a vegetation community below which the
community is considered at risk of decline has been set by the EPA (EPA 2000). The
vegetation system associations present in the Study Area have >30 % of the pre-european
mapped extents remaining, with the exception of Bassendean – 1031 which has only just over
8 % of the original extent remaining (Table 1). This vegetation system association occurs
within the Study Area along the southern edge of the existing Cooljarloo mining area; the
majority of the pre-european extent of this vegetation system association occurred to the east
of the Study Area and was cleared for agriculture. The extent of each vegetation system
association currently reserved for conservation present within the Study Area range from just
over half the current extent reserved (Guilderton – 1026), to none of the current extent
reserved (Bassendean – 1031).
The DPaW Threatened Ecological Communities (TEC) and Priority Ecological Communities
(PEC) databases were interrogated (April 2013) for information regarding any occurrences of
TECs or PECs within or in the vicinity (10 km buffer) of the Study Area (DEC 2013a). There
are no known occurrences within the Study Area; however, one TEC and one PEC occur
within 2 km of the boundary of the search area:
PEC-006 (Swan): Claypans with mid dense shrublands of Melaleuca lateritia over
Commonwealth TEC 121: Claypans of the Swan Coastal Plain).
TEC-018 is restricted to Lake Thetis, which is approximately 30 km to the north-west of the
small locations through the south-west, the nearest of which in relation to the Study Area is
located at Lake Walyengarra, which is approximately 10 km south of the Study Area.
Appendix A presents definitions, categories and criteria for TECs and PECs (DEC 2010).
The Study Area is located within the Minyulo and Mimegarra Wetland Suites as defined by
consists of a series of sumplands, damplands and creeks within the Bassendean System. The
creek transports sediment and flushes water from the associated floodplains and palusplains.
The presence of an undisturbed buffer of vegetation surrounding the Mullering Brook
enhances the biological values of this Suite.
The Mimegarra Suite is represented north of private property located north of Woolka Rd.
damplands within a generally water deficient area (Semeniuk 1994). The basins provide
habitat nodes for fauna, with the undisturbed vegetation which surrounds the majority of these
basins providing hydrological buffers. Both the Minyulo Brook and Mullering Brooks are
considered to be locally to regionally significant (Semeniuk 1994).
Biodiversity hotspots are areas that support natural ecosystems that are largely intact and
they are also areas with a high diversity of locally endemic species, which are species that are
not found or are rarely found outside the hotspot (DoE 2013b). The Southwest Australia
Hotspot is comprised of the Southwestern Botanical Province, and includes 2 948 endemic
species; the forest, woodlands, shrublands and heaths of this area are characterised by high
endemism among both plants and reptiles (Conservation International 2013); in addition,
some areas within the Swan Coastal Plain subregion are of known high ecosystem and species
diversity (Mitchell et al. 2002).
Along with occurring in proximity to the junction of several land systems and vegetation
Biodiversity Hotspot, which is one of fifteen Australian hotspots recognised by the Australian
Government in 2003. This area is known to support a large number of distinct, species-rich
and endemic communities (DoE 2013b).
Numerous flora studies have been undertaken throughout the region, providing good
contextual information regarding flora taxa known of the region and their distribution. On a
regional scale, a total of 624 taxa were recorded in a study of vegetation between the Moore
River and Jurien (Griffin and Keighery 1989); 2 847 flowering vascular plant taxa (including
1964 native taxa) were subsequently recorded in 649 sites in the northern sandplain region
between Geraldton and Perth (Griffin 1994). It was noted by Griffin and Keighery (1989)
that it is likely that the flora in the northern sandplains region represents one fifth of the flora
of Western Australia. Current regional information on FloraBase (DPaW 2013a) shows that
approximately 4 165 current vascular plant taxa are known in the SWA02 subregion, of which
3 322 are native taxa.