Information Sheet (sub-catchment)
S4 - Grantham Creek Sub-Catchment
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1.
General Description
Grantham Creek extends from Grantham reserve at the southern
end of Seven Hills to the confluence of Toongabbie Creek on
the northern side of the railway line. The creek corridor
provides an important connection to Seven Hills Railway station.
The creek bed is partially natural at the upper reaches and
channelled at the northern edge of Duncan Park, through Best
Road Park and under the cross streets - Lucrettia and Margaret.
In Duncan Park the creek is in a semi-natural state as it
runs through a remnant of River-flat Forest before being diverted
into a concrete culvert at the northern edge of the park.
2. Map Title
Grantham Creek Sub-Catchment Map
3. Geology
Grantham
Creek along with Greystanes Creek, Pendle Hill Creek, Finlaysons
Creek, and Coopers Creek, drain from the south west of the
catchment to join with Toongabbie Creek north of the railway
line. These creeks flow across the Cumberland Plain which
is a low, undulating plain underlain by horizontally bedded
sediments of the Wianamatta Group, mainly Bringelly Shales.
These shales are generally composed of claystones, siltstones
and carbonaceous shales with sparse sandstone lenses. The
sediments were laid down in a coastal alluvial plain during
the middle Triassic, (200Ma)
4. Geomorphology
The natural channel of the creek has been largely lost due
to engineering however in Duncan Park and Grantham Research
Poultry Station some semi-natural remnants remain. The sub-catchment
of Grantham Creek is generally low lying, undulating territory,
with its height above sea level not exceeding 80 metres throughout
the length of the creek.
5. Soil Types
The Grantham Creek sub-catchment soils are generally fine-grained
silts and clays. The predominant soil landscape in the sub-catchment
is Blacktown which has been formed by residual geomorphic
processes. These soils are generally of low fertility and
less than 100 cms in depth. In the lower reaches of the Creek,
near the confluence with Toongabbie Creek, a much deeper,
fluvial soil is evident along the creek margins. This soil
is also of low fertility and is highly likely to erode in
storm events.
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6. Vegetation communities
There are two important remnants in the sub-catchment:-
- Swamp Oak River-flat Forest along the creek margins
in Duncan Park and the Poultry Research Station. This forest has
potential as a source of seeds for regeneration of other areas
along the creek.
- Grey Box Woodland is found in Duncan Park, Grantham
Park, Natal Place Reserve and most significantly in the old Poultry
research Station. Species such as Spotted Gums, Forest Red Gums
(Eucalyptus tereticornis) and Grey Box (E. moluccana) are typical
of the woodland community. There are few indigenous understorey
species in the park, instead weeds have colonised the understorey
creating a dense habitat for birds and reptiles.
These communities are highly significant and are listed under the
Threatened Species Act. Generally the open spaces and parklands
contain scattered, indigenous canopy trees in grass with little
understorey. In the drainage easements between the parks the channels
are heavily weed infested and the creek banks are colonised with
non-indigenous trees such as Privet and Silky Oak.
7. Biodiversity
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Remnant vegetation in Duncan Park is a valuable habitat
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The areas of scattered remnant vegetation provide habitat
for native animals such as birds, possums and small reptiles
but in general the Grantham Creek corridor does not support
a diverse native ecosystem. In the remnant forests of Duncan
Park and Grantham Research station the understorey of weeds
provides a dense habitat for small reptiles such as skinks
and blue tongued lizards and small birds such as wrens and
willy wagtails.
Aquatic biodiversity has been similarly depleted as water
quality in the channel is poor and riparian vegetation has
been replaced by concrete and non-native vegetation species.
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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, (Downes, Masters Thesis, 1998).
98% of total flow volume leaves the catchment in only 2% of the
time. The average dry weather flow across the catchment is 1890
litres/ha/day.
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. The creeks that
originate in the Wianamatta Shale country, ie in the Cumberland
Plain to the west and south, have very little dry weather flow.
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9. Rainfall
Rainfall measurements between 1969 and 1996 show that there
is a significant 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
Over half of the open space along the corridor is zoned as
recreational reserve such as at Duncan Park, Grantham Park,
Natal Place Reserve and Best Road Park. Drainage easements
run between private land between Grantham Road, Duncan Park
and Best Road.
There is no formal footpath in this area but there is evidence
of informal pathways in the parks and easements connecting
the creek to the Seven Hills railway line.
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Grantham Creek at the bottom of Duncan park with a view of
surrounding housing
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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.
Today Parramatta and Blacktown are thriving urban areas and make
up a 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. 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.
12. Community Groups
Local residents have shown interest in rehabilitating the creek
corridor, groups such as Friends of Duncan Park are actively doing
so. Active involvement of local schools should be encouraged in
tree and understorey planting, weeding and clean up days. Streamwatch
groups can test water quality in the creek. It has been suggested
that "Care for Grantham Creek" days could be initiated.
13. Management Issues
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Blacktown City Council maintains a detention basin on Grantham
Creek in Duncan Park, Seven Hills, to help alleviate flood
problems and improve water quality in the creek. Other management
issues suggested for Grantham Creek sub catchment include:
- Develop a Cumberland Plain Woodland restoration plan for
the area around Duncan Park, Australorp Ave, Grantham Poultry
Research station and the drainage easement between Grantham
Road and Best Road.
- Establish a bush regeneration program for the Swamp Oak
River-flat Forest in Duncan Park, including staged weed
removal, see propagation and replanting of indigenous species
- Fence off areas under remnant trees to encourage natural
regeneration.
- Re-establish riparian species along the drainage easements.
- In the channelled sections of the creek investigate restoration
of the creek to mimic the natural state, introduce pools,
riffles, meanders or constructed wetlands to increase habitat
for aquatic fauna such as frogs.
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Streambank erosion and weed invasion such as this at Grantham
Rd are a constant problem
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14. Other Resources
and Links
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