4. Creek Corridor Environments
4.1. Protected Flora and Fauna in the Catchment
Condition of Bushland
Remnant bushland has been identified along Hunts Creek, Darling Mills
Creek and its tributaries and along Toongabbie Creek. These areas are very
significant biodiversity reserves, but are generally subject to the presence of
invasive bushland weed species. In some areas, only the large canopy trees
remain and there is a dense sub-canopy of woody weeds and exotic
(introduced) vines.
Threatened Flora Species
Flora species of conservation significance have been identified by
James/NPWS (1997) and Oculus (1998) for each of the four (4) corridors
supporting significant areas of remnant vegetation. These include species
and communities listed under the Schedules of the Threatened Species
Conservation Act 1995, and those identified by the Urban Bushland
Biodiversity Study (James/NPWS 1997).
Species of conservation significance are listed in Figure 4.1. Significant
species listed were recorded in the general vicinity of the proposed multi-use
pathway, and do not necessarily occur in the area directly affected by the
proposed pathway. No further investigations were undertaken during the
brief field survey carried out as part of the current study.
Figure 4.1
Threatened Flora Species Known to Occur Within the Vicinity of the Proposed Bike Path
Endangered
Gazettal Date
Toongabbie Creek Corridor
Persoonia hirsuta
12.6.98
Darling Mills Creek Corridor
Asterolasia elegans
Hunts Creek Corridor
Asterolasia elegans
Acacia bynoeana
Leucopogon fletcheri
ssp fletcheri
Acacia gordonii
17.9.99
Vulnerable
Epacris purpurascens
var purparescens
Darwinia biflora
Tetratheca glandulosa
Grevillea juniperina
Zieria involucrata
Leucopogon exolasius
Epacris purpurascens
var purparescens
Epacris purpurascens
var purparescens
Zieria involucrata
Leucopogon exolasius
Olearia cordata
Lasiopetalum joyaceae
Melaleuca deanii
Darwinia biflora
Tetratheca glandulosa
Darling Mills Tributary Corridor
Pterostylis saxicolia
Gazettal Date
24.12.99
24.12.99
24.12.99
26.2.99
Epacris purpurascens
24.12.99
var purpurascens
Darwinia biflora
Tetratheca glandulosa
Pimelea curviflora var
curviflora
NB: Full details, including lists of regionally significant species not listed under the TSC Act, but
considered of conservation significance (James/NPWS 1997) are provided in Appendix C
 Jamieson Foley Traffic & Transport
Threatened Ecological Communities
Several ecological communities listed under the TSC Act 1995 occur along
targeted creek corridors within the Upper Parramatta River Catchment
(Figure 4.2).
All remnant vegetation in the Upper Parramatta River catchment is of
significant conservation value. The impacts of pathways on these values
can be managed through sympathetic track location, design, material
selection, construction techniques, drainage control and consideration of
bushland needs. The 8-part test of the Threatened Species Conservation
Act must be applied to all areas including vegetation meeting the definitions
under this Act.
Figure 4.2
Threatened ecological communities listed under the TSC Act occurring
along the route of the proposed multi-use pathway
Community
Toongabbie Creek Corridor
Shale Sandstone Transition Forest
Sydney Coastal River Flat Forest
Cumberland Plain Woodland
Darling Mills Creek Corridor
Shale Sandstone Transition Forest
Hunts Creek Corridor
Sydney Turpentine Ironbark Forest
Darling Mills Creek Tributary
Shale Sandstone Transition Forest
Gazettal Date
11.9.98
12.2.99
13.6.97
11.9.98
16.10.98
11.9.98
4.2. Potential Pathway Effects
Where the proposed pathway traverses or cuts through an area of remnant
bushland, there is the potential for fragmentation, which will produce a range
of negative edge effects. Such effects include increased runoff from hard
surfaces, the potential for increased nutrient input (depending on materials
used for the pathway), and an increased level of weed invasion. Pathway
location should wherever possible, avoid fragmentation of bushland areas,
unless there are pre-existing pathways or access tracks which can be
utilised (eg service tracks).
Where the proposed pathway skirts remnant bushland, these negative
effects will be concentrated on one edge, particularly if the pathway is
located up-slope. Where this occurs, care must be taken to redirect runoff
from the exposed edge, and to establish a protective buffer zone between
the pathway and the bushland. Special drainage structures maybe required
to provide the protection required.
 Jamieson Foley Traffic & Transport
4.3. Protecting the Environment
Weed Control
Creeklines are by definition areas of constant disturbance, particularly in the
urban environment. It is therefore not surprising that riparian vegetation in
the catchment has suffered more severely from the impacts of development
than off-stream bushland.
The invasion of weeds and introduced plants affects the physical,
hydrological and ecological aspects of the plant community, altering
structure, floristic and habitat values. Aggressive weeds will displace native
species as the introduced plants gain a competitive advantage from the
increased level of soil nutrients and the changed flow of both surface and
ground waters. Furthermore, many species declared as ‘noxious’ also
possess characteristics potentially harmful to humans and to the
environment.
In order to lessen impacts on good quality bushland, and to rehabilitate
degraded areas along the route of the proposed pathways, a bush
regeneration/weed control program is highly recommended.
Similar
programs incorporating pathway construction and bushland regeneration
have been successfully undertaken elsewhere in the Sydney Region. Based
on experience on those areas, it is recommended that a minimum area of six
(6) metres be targeted for rehabilitation, that is, for weeding and replanting
for three (3) metres on either side of any new cycleway or walking track.
Pre-construction weeding along the pathway corridor will be particularly
important in reducing weed spread during construction.
Following
construction, rehabilitation work will include replacing topsoil, sculpting
landforms, and replanting using local indigenous species. A maintenance
program will be set in place until such time as new plants are established.
Where a local Bushcare or Landcare group already exists, efforts should be
made to incorporate the care of the pathway environs into the pre-existing
works program.
Control of noxious weeds (Noxious Weeds Act 1993) in Hawkesbury,
Blacktown, Baulkham Hills, Penrith and Windsor LGAs is carried out by
Hawkesbury River County Council (HRCC), which is a single purpose
authority funded through its constituent councils. However, most available
resources are expended on aquatic weed control in the Hawkesbury-Nepean
River and other water bodies, and very little noxious weed control is carried
out by HRCC in remnant bushland areas of the Upper Parramatta River
catchment. The control of noxious and environmental weeds is usually
carried out by local Councils and in some cases by volunteer bushcare
groups.
Appendix B provides a series of generic guidelines for development
adjacent to or in remnant native bushland.
 Jamieson Foley Traffic & Transport
Pathway Materials
The choice of surfacing materials for pathways is of significant importance
from a number of perspectives, including:
◦ Users – hard surfaces for wheeled users; softer surfaces for running
and jogging; most require smooth surfaces that are free of potholes
and good maintenance
◦ Pathway authorities – low installation and maintenance costs, good
access for maintenance vehicles to the pathway and adjacent areas;
there is a balance between installation costs and maintenance costs
◦ Environmental impacts – visual intrusion of straight and wide
pathways; leaching of chemicals from paving materials; run-off
stormwater
Figure 4.3 provides an overview of a number of potential materials that
could be used for the pathways, including installation and maintenance
costs, total lifecycle costs and potential environmental impacts.
It is noted that all pathway materials selected are not known to be reactive or
cause leaching effects.
It is evident that although materials such as decomposed granite may have
lower visual impacts and lower construction costs, their lifecycle costs are
considerably higher than say bitumen or concrete. It may be appropriate to
consider the use of more durable materials to minimise lifecycle costs, while
managing visual impacts in environmentally significant areas by choosing an
alternate pathway cross section, with smaller radii and more frequent
horizontal curves.
Boardwalks and fibreglass reinforced plastic surfaces are expensive and not
appropriate for general use. These materials should only be used for special
applications, such as in areas subject to inundation, wetland areas or for
short distances adjacent to bridge structures (eg Lennox Bridge).
 Jamieson Foley Traffic & Transport
Figure 4.3
Pathway Materials
Surfacing
Material
Construction
Cost1
Annual
Maintenance
Cost2
$27,000
Lifecycle Cost1
Environmental
Impacts
$391,000
Reduced run-off
and visual
intrusion
Visual intrusion
due to path width
Visual intrusion
due to path width
and colour
Visual intrusion
varies, depending
on location
Reduced visual
intrusion,
depending on
colour and width.
Minimal run-off.
Decomposed
Granite3
$105,000
Bitumen
$120,000
$3,000
$152,000
Concrete
$195,000
$1,500
$210,000
Boardwalk4
$1,200,000
$2,000
$1,221,000
Fibre Glass
Reinforced
Plastics5
$900,000
$2,000
$921,000
Notes
1 Assuming 20 year period, 3.0m wide pathway, 1 km length, no structures
2 Assuming regular periods of significant rain/flooding, requiring 30% replacement of the surface
annually
3 Alternatives such as blue stone and limestone were also considered, but there were concerns
about leaching effects; shell grid is widely used in The Netherlands as a surfacing material for
pathways through forested areas, but it is not commonly used in Australia
4 For use in special areas, where cross section constraints exist
5 eg as used on the John Whitton Bridge at Rhodes
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