Information Sheet (sub-catchment)
S2 - Darling Mills Creek Sub-Catchment
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1. General Description
Darling Mills Creek is one of the two main tributaries of
the Upper Parramatta River draining the north and north east
parts of the catchment, the other being Hunts Creek. Darling
Mills creek is mainly in natural condition running along the
bottom of a long steep sandstone valley lined with sandstone
boulders and riparian vegetation. The creek corridor contains
the most substantial and intact bushland in the Upper Parramatta
River catchment. Darling Mills Creek flows from West Pennant
Hills, through North Rocks and Northmead to join the Parramatta
River near Cumberland Hospital.
The sub catchment of Darling Mills Creek includes the tributaries
Bidjigal, Sawmill, Excelsior, Blue Gum, Bellbird and Bellamy
Farm Creeks.
Increasing urbanisation has had its effect on the creek.
The installation of main sewage lines and overflow points
along the creek have resulted in water pollution during high
rainfall. Residential development at the headwaters, in Castle
Hill and West Pennant Hills, has caused weed invasion and
siltation.
2. Map Title
Darling Mills Sub-Catchment Map
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Darling Mills Creek, West Pennant Hills
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3. Geology
Darling Mills Creek and its tributaries, which flow from the north
east of the catchment, are incised into Hawkesbury Sandstone which
makes up the Hornsby Plateau. The ridge tops, such as at West Pennant
Hills, are capped by Ashfield Shales belonging to the Wianamatta
Group. In some isolated areas discontinuous beds of the Mittagong
Formation, interbedded sandstones and shales, can be seen between
the Ashfield shales and the Hawkesbury Sandstone.
The Hawkesbury sandstone was laid down as a very thick sheet of
sand by energetic, braided streams flowing from the south west during
the mid Triassic. Sandstone cliffs and boulders are characteristic
of the gullies through which the creek flows.
4. Geomorphology
Darling Mills Creek and its tributaries in the north are deeply
incised into the Hawkesbury Sandstone with the creeks flowing in
steep V-shaped valleys lined by sandstone cliff faces. The hilly,
rocky topography contrasts with the undulating Cumberland Plain
in the south west of the Upper Parramatta River catchment.
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Little alluvium naturally flows out of this system. However
very large deposits of sand along the middle and lower reaches
of Darling Mills Creek have filled in most waterholes forcing
the creek to migrate and erode adjoining banks. This is causing
major erosion of private land at locations such as Speers
Road in North Rocks. Evidence uncovered as part of the Environmental
Impact Statement (EIS), for the Loyalty Road Flood Retarding
Basin shows that a lot of the sand in Darling Mills Creek
is not of local origin but has been washed off building sites
over decades of residential development.
5. Soil Types
In the sub catchment of Darling Mills Creek the soil is generally
coarse to medium grained sands and sandy loams. This tributary
flows over Hawkesbury Sandstones, which are generally quartz
rich, coarse grained sandstones. The soil landscapes occurring
in the Darling Mills Creek sub-catchment include Hawkesbury,
Gymea, Glenorie and Lucas Heights. These soils are generally
less than 100 cms in depth, easily eroded even in low flow
conditions and of low fertility.
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Steep valleys lined by sandstone walls are typical in the
Darling Mills Sub-Catchment
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6. Vegetation communities
Darling Mills Creek vegetation is mainly in a natural state with
the most substantial and intact bushland in the Upper Parramatta
River catchment. Large areas of bushland remain in steep sided sandstone
valleys and gullies, typical of Hawkesbury Sandstone landscapes,
and on isolated shale capped Hornsby Plateau in West Pennant Hills.
In the Fauna Impact Study for the Darling Mills Creek Stormwater
Management Study, Mount King Ecological Surveys concluded that "the
bushland of Darling Mills Valley is of regional conservation significance
as it includes plant communities and species which are of restricted
distribution in Western Sydney. It is an important habitat for an
unusually high number of plants which are inadequately conserved
in Western Sydney." The vegetation communities associated with Darling
Mills Creek and Excelsior Reserve includes:
· Sydney Sandstone Gully Forest on south facing slopes
· Coachwood Rainforest in moist, sheltered areas
· Blue Gum River-flat Forest along the creek edges in deeper
soils
· Sandstone Ridgetop Woodlands on the drier slopes and ridges
where soils are shallow and low in nutrients. This woodland is dominated
by Red Bloodwood (Corymbia gummifera), Smooth-barked Apple (Angophora
costata), Narrow-leafed Apple (A bakeri) and Sydney Peppermint (Eucalyptus
piperita). Other species include Scribbly Gum (E. haemastoma) and
Yellow Bloodwood (C. eximia). Over 230 species were recorded in
a survey conducted in 1992.
· Blue Gum High Forest is found on the north eastern edge
of the corridor along Castle Hill Road and in the Cumberland State
Forest. The forest is associated with clay soils derived from the
shales capping the Hornsby Plateau. Main species are Sydney Blue
Gum (E. saligna), Grey Ironbark (E. paniculata) Forest Red Gum (E.
tereticornis) and White Mahogony (E. acmenioides). Blue Gum High
Forest is now rare in the Sydney region. Small remnants of Blue
Gum High Forest occur in Bellamy's Farm Reserve and Richard Webb
Reserve. These reserves have been mown which means that much of
the understorey is missing and only canopy trees remain.
· Transition communities occur where species more typical
of sandstone overlap with the clay adapted species on the shale/sandstone
interface such as in the central section of the Cumberland State
Forest, the IBM site and the fringes of sandstone gullies along
the Darling Mills Creek.
7. Biodiversity
The Darling Mills Creek corridor is a significant regional habitat
linking with the Berowra Bushland Park in Hornsby and further on
to Kurringai Chase National Park and Brisbane Waters. It has the
highest biodiversity in the Upper Parramatta River catchment and
the most potential for wildlife migration and genetic exchange.
The substantial bushland communities within the Darling Mills Creek
catchment provide excellent habitat for native animals. Animals
located in the catchment include:
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three arboreal marsupials, the Common Ringtail
Possum, Common Brushtail Possum and the Sugar Glider
· sixty seven bird species including 4 vulnerable and rare
species.
· nine species of bat
· rare amphibians such as the green and golden bell frog
The habitat is typical for such animals as the long nosed
bandicoot, water rats, platypus and echidna which could occur
but no direct evidence has been found recently.
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8. Hydrology
Flow regime is the long term pattern of high flows and low flows
in creeks and rivers.
Generally there is very little flow in catchment creeks for the
majority of the time. 98% of total flow volume leaves the catchment
2% of the time, (Master Thesis, Downes, 1998).
Dry weather, (base) flows are generally greater in Darling Mills
Creek, Hunts Creek and their tributaries which rise in the Hawkesbury
Sandstone areas in the north east of the catchment. In contrast
creeks such as Blacktown Creek, Coopers Creek, Grantham Creek and
Greystanes Creek that originate in the Wianamatta Shale country,
that is, in the Cumberland Plain to the west and south, have very
little dry weather flow.
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Darling Mills Creek in heavy flood, January 1999
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Since the mid 1980's floodwaters have
caused considerable damage along Darling Mills Creek and the
Upper Parramatta River. Areas most affected have been Northmead,
North Rocks and North Parramatta. Between 1986 and 1991 some
properties were flooded repeatedly. In 1889 a flood greater
than these invaded the low lying areas of Parramatta township.
However in 1889 the upstream catchment was mainly farms and
orchards. With the catchment almost fully urbanised the same
rainfall today would result in much higher flood levels. In
a major flood such as the 100 year flood, a third of Parramatta
CBD would be inundated. |
As most of the elevated plateaux and flatter sandstone ridges are
developed for housing, increased urban run off has impacted on the
downstream sections of the creek. This has caused sedimentation
and severe flash flooding which was threatening the Parramatta CBD.
To remedy this a large flood control structure has been built across
the creek near Loyalty Road.
9. Rainfall
Rainfall measurements between 1969 and 1996 show that there is
a significant regional variation in the rainfall intensity and average
in the catchment. The highest average rainfall occurs in the north-east
section of the catchment, (headwaters of Darling Mills Creek, 1200mm
per year) and the lowest in the south-west, (headwaters of Toongabbie
and Greystanes Creek, 800mm per year).
10. Landuse
The Darling Mills Creek corridor contains the most substantial
and intact bushland in the Upper Parramatta River catchment. It
includes remnant bushland and open space in the area from West Pennant
Hills down through North Rocks and Northmead in the Parramatta LGA.
The corridor is bound by Old Northern Road and Castle Hill Road
at Castle Hill in the north, by Pennant Hills Road in West Pennant
Hills to the east and by North Rocks Road in Baulkham Hills in the
south. The corridor includes several major reserves such as Excelsior
Park Reserve, Darling Mills State Forest, Ted Horwood Reserve, the
Eric Mobbs Recreation Reserve and the Cumberland State Forest.
The areas with remnant vegetation in council managed reserves are
zoned Open Space (6a). Darling Mills State Forest and Cumberland
State Forest are zoned Special use Forestry (5a), the IBM Forest
is zoned light industrial, whilst some of the upper reaches, in
Baulkham Hills LGA, are in private ownership. The M2 Freeway easement
is zoned 5b. The corridor provides a significant recreation area
in the region and offers opportunities for bush walking and relaxation
in the natural environment. Cumberland State Forest is used for
research into revegetation and forest management.
11. Social History and impacts on landuse and the environment
(incl. Aboriginal history)
The Upper Parramatta River catchment was originally home to the
Dharug Aboriginal people who had inhabited the area for more than
forty thousand years before British settlement in 1788. The local
clan in the catchment was the Burramatta, from which the name Parramatta
came, (burra meaning place and matta meaning eels). Many significant
items of Aboriginal cultural heritage can be seen in the catchment,
specifically in Lake Parramatta and Parramatta Parks, including
such things as middens, tree scars, cave paintings and stone flakes.
The early settlement in Port Jackson faced many difficulties, not
the least of which was the poor soil which would not support imported
strains of wheat and other staple crops. Governor Phillip, who had
explored the upper tidal reaches of the Parramatta River in 1788,
encouraged establishment of new farms on the low lying river flats
by giving land and convicts to the white settlers. This resulted
in the development of the township of Rose Hill which later became
known as Parramatta, the Aboriginal name meaning "the place where
the eels lie down." Parramatta is Australia's second oldest settlement,
having been established on November 2nd 1788. Lake Parramatta provided
a clean and reliable water supply for the orchards and market gardens
so the township flourished. With the introduction of rail transport
in the 1850's Parramatta became the main metropolis of NSW.
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Swimming near Speers road in 1954
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As late as the 1940's the area which is now West Pennant
Hills was mainly a patchwork of agricultural fields. Residential
development was slower in this area due to difficult terrain,
more dense bushland and easier access along the Parramatta
River and onto the Cumberland Plain.
Today Parramatta and Blacktown are only two of the town centres
in the catchment which has become a thriving urban areas and
major regional centre. The catchment area of 107 km2, is 70%
urbanised and contains approximately 80,000 properties and
a population of 220,500 (Australian Bureau of Statistics,
1999). The cities of Parramatta and Blacktown are located
at the perimeter of the catchment, Parramatta Central Business
District being at the outlet, and Blacktown at the western
extremity.
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The long history of intensive use of the catchment has resulted
in significant environmental management problems. Today factories,
residences and commercial businesses cover the area, impervious
surfaces such as roads, roofs and car parks result in more frequent
flooding and all forms of land use, (residential, commercial, recreational
and industrial), have caused severe deterioration in water quality.
The Darling Mills Creek corridor has fared better than most as
it contains the most substantial and intact bushland corridor in
the Upper Parramatta River catchment. This is in part due to the
steepness of the terrain which resulted in much later development
of residential and industrial areas. However recent developments,
upstream in Baulkham Hills are impacting severely on the lower reaches
of the creek.
12. Community Groups
The bushland reserves throughout the Darling Mills Creek sub catchment
are well used by residents. The corridor provides a significant
recreation area in the region and offers opportunities for bush
walking and relaxation in the natural environment. Local residents
should be encouraged to join or form Bushcare or Landcare groups
to monitor, revegetate and remove weeds from the forests in the
catchment.
Local schools test water quality in the creek through the Streamwatch
program, they could also be encouraged to "adopt" sections of the
creek for care and maintenance. The creek corridor could become
a valuable educational tool for local school and community groups.
13. Management Measures in Place
Since the mid 1980s, floodwaters have caused considerable damage
along Darling Mills Creek and the Upper Parramatta River. Hardest
hit have been areas at Northmead, North Rocks and North Parramatta.
Between 1986 and 1991 some properties were flooded repeatedly.
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The damage
bill from these floods has been high with residents and businesses
suffering distress, hardship and personal loss. In 1994 the
Upper Parramatta River Catchment Trust proposed to build a
flood retarding basin on Darling Mills Creek near Loyalty
Road. This is now in place and at a cost of $8 million has
reduced the likelihood of downstream flooding.
Retarding
Basin is not a dam, it is a concrete wall 25 metres high with
a short tunnel in its base. During heavy rain, when all the
stormwater in the creek cannot flow through the tunnel, excess
water will be temporarily stored behind the wall. Once the
rain eases or stops the stored water will drain away quite
quickly.
During heavy rain the temporary storage of water will increase
the creek depth and the area of flooding upstream of the wall
but reduce the area flooded downstream of the wall by a similar
amount.
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Loyalty Rd Flood Retarding Wall
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Structure
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Creek
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Location
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Detention Basin
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Bellbird Creek
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Avonleigh Way, West Pennant Hills
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Detention Basin
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Excelsior Creek
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Bron Close West Pennant Hills
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Detention Basin
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Bellbird Creek
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Glenroe Avenue, West Pennant Hills
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Detention Basin and sediment trap
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Darling Mills Creek
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Loyalty Road, North Rocks
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Detention Basin
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Darling Mills Creek
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Northmead Reserve, Elizabeth Crescent, Northmead
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Detention Basin
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Rifle Range Creek
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Muirfield Golf Course, North Rocks
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Gross Pollutant Trap
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Christmas Bush Creek
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Cnr Cross & Carey Streets, Baulkham Hills
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Pit Insert Trap
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Darling Mills Creek
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Old Northern Road, Seven Hills
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14. Management Issues
The greatest opportunity for this corridor is the adequate
protection and enhancement of the existing biological diversity.
The corridor provides the highest diversity and the largest
area of habitat in the Upper Parramatta River Catchment. The
most significant quality and use of this corridor is the experience
of a completely natural landscape and associated ecological
processes. The valley is substantial enough to cater as a
weekend destination and allows for half day bushwalks. Compared
with other cosmopolitan cities of the size and population
of Sydney this is a rare opportunity.
Even though the creek is in a close to natural state, increasing
urbanisation has had its effect.
· The installation of main sewage lines and overflow points
along the creek have resulted in water pollution during high
rainfall
· residential development in the headwaters, at Castle Hill
and West Pennant Hills has caused weed invasion and siltation.
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Sewer overflow points in Darling Mills Creek
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Protection and enhancement of this corridor should
proceed as follows:
· Maintain the creeks as rocky, natural creek beds with riparian
vegetation
· Prevent the construction of paved pathways or bridges
· Continue weed removal
· Control and prevent run off from surrounding developments
· Continue bush regeneration programs to increase habitat for native
wildlife
· Enhancement of reserves for nature based recreation such as bush
walking, bird watching and scenic enjoyment
· Discourage unsympathetic uses such as mountain bikes, trail bikes
and ball games
· Use the reserve as an educational tool
· Revegetate smaller parks and streetscapes with native vegetation
to increase the bushland links
· Installation of nesting boxes and shelter for small animals
· Control of cats to prevent predation of small native animals
15. Other Resources and Links
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