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Fauna sensitive road design guidelines
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Fauna sensitive road design guidelines
Fauna Sensitive Road Design Guidelines
Revision 0 / August 2012
Document ID: 1447218
VicRoads Fauna Sensitive Road Design Guidelines
© VicRoads 2012
This document is an uncontrolled copy and may be
updated from time to time. The issue date on the front
cover and inside cover of this document will be updated
following any revisions to this guideline. Please refer to
the VicRoads website or intranet for the most current
version of this document.
The information contained in these guidelines is
for general information only and is not intended
to constitute legal advice. VicRoads accepts no
responsibility for any loss arising out of reliance
on any information contained in this document.
Acknowledgements
These guidelines were prepared by VicRoads
Environmental Sustainability. VicRoads would
like to acknowledge the assistance of all who
provided comments on these guidelines.
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Glossary
Aquatic – Animals living in waterways.
Arboreal – Adapted for living and moving about in trees.
Invertebrates – Animals such as insects that
lack a backbone.
Baffle – Flat plate that controls or directs the flow of
water or energy through aquatic culverts.
Landscape - Total spatial and visual entity that includes
all the physical elements of landforms including manmade environments.
Barrier Effect – A road which acts as a barrier or physical
obstacle which results in the increased likelihood of
levels of animal mortality due to animal/ vehicle collision.
Landscaping – This is the modification of the existing
landscape and includes visible features of an area of land.
Biodiversity – A number, variety and genetic variation
of plants and animals found within a specific
geographic region.
Connectivity – Where plants and animals are able
to disperse/move through the landscape without
obstruction to maintain genetic diversity.
DSE – Victoria Department of Sustainability
and Environment.
Ecosystem – A biological system consisting of all
living organisms or biotic components.
Edge Effect – Term used to describe the [conjunction
of] a boundary between natural habitats (e.g. forests)
and disturbed or developed land.
EPBC – Environment Protection and Biodiversity
Conservation Act 1999 (Cth).
Fauna Fence – Free standing structure and/or barrier
designed to prevent wildlife from moving beyond a
specific point or boundary.
Macropod - Herbivorous group of hopping mammals
including kangaroos and wallabies.
Marsupial - Any mammal of the order Marsupialia,
in which young are born in an immature state and
continue development in the pouch.
Mulch – Protective cover of chipped plant material
placed over the soil to retain moisture, reduce erosion
and suppress weeds.
Riffle – A rocky shoal lying just below the surface
of a waterway, often forming rest pools.
Sandbar – Ridge of sand or fine gravel in a river or
along a shore formed by the action of waves or currents.
SEWPaC – Department of Sustainability, Environment,
Water, Population and Communities.
Substrate – Surface or layer of sediment on an
object such as a bridge, river or within a culvert.
Terrestrial – Animal or plants living on the land
(not aquatic).
Fragmentation – Breakup of continuous habitat
into smaller populations.
Vertebrate – All animals which have a backbone
including amphibians, birds and mammals.
Indigenous – Plants endemic to a given area
or geological zone.
Wetland – A land area that is saturated with water.
Wetlands can be permanent or seasonal and often
have a distinct ecosystem.
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Fauna sensitive road design guidelines
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Contents
Introduction6
1. Purpose
1.1 Implementing fauna sensitive road design
6.4 Culverts to aquatic animals
21
7
Locating aquatic crossings
21
7
Culvert designs
22
Baffles22
2. Conduct biodiversity assessments
8
Culvert rehabilitation
23
Culvert maintenance
23
8
Fish ladders
23
2.3 Targeted flora and fauna survey
8
Rock ramps
23
2.4 Early/pre-installation monitoring
9
2.1 Desktop flora and fauna investigations
8
2.2 Detailed flora and fauna assessments
3. Design and installation of fauna sensitive
road design treatments
10
3.1 Minimise biodiversity impacts
and habitat fragmentation
10
3.2 Determining fauna sensitive road
design treatments
11
3.3 Evaluate landscape objectives
12
3.4 Incorporate relevant biodiversity management
requirements into contract specification
12
4. Construction
13
4.1. Contractors Environmental Management
Plan (cemp)
13
4.2 Fauna protection during construction
13
5. Managing and monitoring fauna sensitive
road design installations
5.1 Ongoing monitoring surveys
14
14
6.2Overpass
24
6.2.1Canopy bridge
24
Maintenance27
6.2.2Canopy connectivity
27
6.2.3Land bridges
28
Target species
28
Design specifications
29
Maintenance29
6.3.Fencing
Kangaroo and Koala resistant fencing
30
Arboreal resistant fencing
30
Frog resistant fencing
30
Maintenance31
6.4 Habitat enhancement
32
6.4.1Frog ponds
32
Banks32
Shape and size
6. Fauna sensitive road design
15
6.1Underpasses
15
6.2 Bridge underpasses
15
6.3 Culverts for terrestrial animals
16
Entry landscaping
16
Culvert furniture
17
Large culverts
18
Multiple culverts
18
Fauna culverts along waterways
19
Approaches to crossings
20
30
32
Vegetation32
6.4.2Nesting boxes
33
Maintenance33
6.4.3Traffic management
34
Maintenance34
6.4.4Other considerations
35
Light mitigation
35
Fauna relocation
35
Appendix A. Types of fauna mitigation
36
References41
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Fauna sensitive road design guidelines
Introduction
Road infrastructure covers vast areas of land; it traverses
rivers, wetlands, valleys, deserts, coastlines, mountains
and forests. In addition, roads in the landscape create
new habitat edges, alter hydrological dynamics, and
disrupt natural processes and habitats. Roads and their
traffic can impose significant dispersal barriers to most
non-flying fauna, and vehicle traffic can cause the death
of large numbers animals per year (refer Figure 1).
Issues associated with the impact of roads
on biodiversity can include:
Habitat loss - Construction of roads and railroads
usually involves a net loss of wildlife habitat. The
physical encroachment on the land gives rise to
disturbance and barrier effects that contribute to
overall fragmentation.
Disturbance - Roads and traffic disturb and pollute
the physical, chemical and biological environment
and consequently alter habitat suitability for many
plant and animal species for a much wider zone than
the width of the road itself.
Corridor - Roadsides can provide refuges, new
habitats or serve as movement corridors for
wildlife. These beneficial effects of infrastructure
are a major challenge to planners and ecologists,
as management and design must consider the
wider landscape context.
Figure 1: Roads have significant impact on wildlife movements.
Mortality - Traffic can cause the death of many
animals that utilise verge habitats or try to cross the
road. Traffic mortality has been growing constantly
over the years, but is considered a severe threat to
only a few species. Collisions between vehicles and
wildlife are also an important traffic safety issue.
Barrier - For most non-flying terrestrial animals,
road infrastructure can create movement barriers
that restrict the animal’s range, make habitats
inaccessible and can lead to an isolation of
populations. The barrier effect is the most
prominent factor in the overall fragmentation
caused by road infrastructure.
These guidelines aim to promote the movement of
wildlife across roads whilst helping to find solutions
to ongoing public concerns about fauna mortality
around roadkill. The treatments outlined here are
intended to connect local wildlife linkages and keep
fauna away from high risk areas. Going forward,
fauna sensitive road design will enable animals to
move between habitats and discourage them from
setting up home ranges within road reserves where
they would be at risk.
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1. Purpose
Objective 2.3 of the VicRoads Sustainability and
Climate Change Strategy 2010-2015 relates to
Improved Biodiversity Values, which incorporates
the need to address habitat fragmentation and roadkill
as referenced below:
Reduced habitat fragmentation and roadkill
through improved implementation of
fauna crossings
The road network has the potential to have a significant
effect on wildlife and ecosystems through habitat
fragmentation, reduced dispersal and mortality by
collision with vehicles.
VicRoads is committed to investigating opportunities
to facilitate fauna movement, where possible, through
the provision of fauna crossings (underpasses or
overpasses), aiming to reduce fragmentation of
habitats and improve and maintain species diversity.
This will involve the investigation of best practice in this
area to inform the development of detailed guidelines
on fauna crossings to assist in more consistent
implementation.
Installed crossings will be subject to a monitoring
regime that will yield information on their effectiveness,
enabling better decisions to be made on future
mitigation measures.
1.1 Implementing fauna sensitive
road design
VicRoads Projects and Regions must demonstrate that all
aspects of fauna sensitive road design are considered in
project planning through to maintenance (refer Figure 2).
INVEST is a VicRoads tool which can be used to
assess the sustainable aspects of a road project.
It sets the standards for best practice and innovation
in sustainability road design and construction. Going
forward, all new VicRoads projects will implement
INVEST from the planning phase to incorporate
sustainability initiatives throughout design and
construction.
To assist projects and regions, Section 3 of the
Biodiversity category of INVEST discusses innovation
by way of design and construction of fauna sensitive
roads. Projects that have incorporated fauna sensitive
road design will receive points for innovation. All of these
considerations are detailed within different stages of
these guidelines.
Step 1
Conduct Biodiversity
Assessments
Has native fauna
been identified
No
Yes
Step 2
Design and installation of
fauna sensitive road design
No fauna
migration required
Step 3
Construction
A Lace monitor in roadside tree in north eastern
Victoria (Source: VicRoads)
Step 4
Managing and Monitoring
fauna sensitive road
design installations
Evaluate maintenance
and monitoring
plan results
Modify as required
Figure 2: Fauna Sensitive Road Design Process.
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Fauna sensitive road design guidelines
2. Conduct biodiversity assessments
2.3 Targeted flora and fauna survey
More information on undertaking biodiversity
assessments, including guidance on the engagement
of biodiversity consultants, can be found in the
VicRoads Biodiversity Guidelines.
Projects are encouraged to carry out broader targeted
flora and fauna surveys in areas of high quality
vegetation, environmentally sensitive locations and
identified fauna movement hotspots.
VicRoads contract shell briefs include the requirements
itemised in relation to fauna sensitive road design.
These briefs can be accessed in Exchange: How To
> Build and Maintain Sustainable Roads.
2.1 Desktop flora and fauna investigations
In some cases, there may be the need for more than one
targeted survey. It is often recommended that surveys be
undertaken more than once leading up to construction
to obtain a better understanding of existing conditions
prior to implementing any fauna mitigation.
Targeted surveys should include:
The consultant should begin the assessment with a
desktop investigation to determine the level and findings
of previous research. The minimum requirements for
this search are outlined in the contract shell briefs and
include accessing the Flora Information System (FIS),
the Atlas of Victorian Wildlife, DSE Ecological Vegetation
Classes (benchmarks), Biodiversity Interactive Maps and
Environmental Protection and Biodiversity Conservation
(EPBC Act) Protected Matters Search Tool. In some
cases, use of previous surveys together with brief field
investigations may be adequate to meet the requirements
of the biodiversity assessment brief.
Details on the habitat, species richness and
population size, dispersal, life cycle, reason for
movement, prey, food, and behaviour.
The desktop investigation will identify fauna species,
or suitable habitat for those species, that have
previously been recorded in the study area.
Detail what other monitoring requirements may
be required post construction
of a fauna crossing.
2.2 Detailed flora and fauna assessments
Discuss any recovery plans and other relevant
published species information.
In most cases, a second level of investigation is required
involving thorough field assessment aimed at identifying
specifically what is on site. This may involve a seasonal
vegetation assessment and trapping and recording of
fauna present.
NB. It is important to ensure that any consultants
undertaking fauna trapping have all relevant permits
under the Wildlife Act 1975 (Vic), prior to commencement
of fieldwork.
Details on the potential impacts from the project
(i.e mortality, loss of connectivity, indirect and
direct impacts).
What a fauna crossing would be provided for,
ie dispersal, annual migration, foraging etc.
What is the best type of fauna crossing?
How many and how far apart should fauna
crossings be?
Detail any discussions with key stakeholders or
relevant groups who have expert local knowledge.
Other recommendations such as signage, light
mitigation or habitat enhancement.
Again, VicRoads contract shell briefs must be utilised
to engage a consultant to undertake targeted surveys.
As a part of this assessment, consideration needs
to be given to the opportunity to incorporate fauna
mitigation methods to improve connectivity and reduce
wildlife mortality. Environmentally sensitive locations,
including identified fauna movement hotspots, need
to be discussed and recommendations provided on
the following:
What potential species may utilise the corridor?
What species will be impacted on a wider
landscape scale?
What is the distance to core and other
vegetation patches?
Are any additional targeted surveys of key species
(or areas) required?
What are some design options, such as fauna
crossings, for consideration by VicRoads?
Wallaby (Source: ES Link Services)
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2.4 Early/pre-installation monitoring
Monitoring is the most important part in achieving
effective fauna sensitive road design and can help
determine connectivity within a given area. Fauna species
move across land for a number of reasons including to
colonise new territory, find mates and forage for new
food sources.
As discussed in Section 3 of this document, VicRoads
should develop goals in response to the impact a
potential road will have on fauna. Pre-installation
monitoring should be conducted during project
planning within a 5-10 km radius of the area in
question in order to give a better understanding
of landscape connectivity, especially how local
fauna species move through the landscape.
Where possible monitoring should be carried out
as early as possible at the beginning of the planning
process; the earlier that monitoring is undertaken the
better the understanding of fauna movements within
a given landscape.
Fauna underpass on the Calder Freeway (Source:VicRoads)
Southern Brown Bandicoot (Source: ES Link Services)
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Fauna sensitive road design guidelines
3. Design and installation of fauna
sensitive road design treatments
Many wildlife and ecosystem processes operate at
landscape scales with some animals moving many
hundreds of kilometres.
Maintaining wildlife connectivity in highly cleared
landscapes is equally as important as maintaining
connectivity across large areas of intact land. As shown
in Figure 3, animals have limited opportunities to move
around landscapes. Where small patches and narrow
corridors of native vegetation remain, these play
a very important role for maintaining wildlife connectivity.
Sugar Glider (Source: VicRoads)
Projects should consider the wider landscape when
planning roads. Goals should be set that consider known
animal movement corridors (eg. drainage lines, creeklines
and strips of native vegetation) that have the potential to
be used by a number of species as part of a landscape
scale perspective when making decisions about wildlife
connectivity measures.
a) Wildlife movements b) Avoidance
c) Fragmentation d) Mitigation
Figure 3: Representation of wildlife movements when considering road design on a)
wildlife populations b) avoidance c) fragmentation and d) mitigation.
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3.1 Minimise biodiversity impacts
and habitat fragmentation
There are a wide variety of techniques and measures
available to mitigate the effects of a new road or the
upgrade of an existing road on flora and fauna. Mitigation
must be designed to meet the requirements of the
specific site and to address the identified problem.
For example, it is not worthwhile installing a structure
designed for arboreal fauna, such as a canopy bridge
or gilder pole, if the issue is with ground fauna; likewise
a culvert crossing is not suitable if the road is in a cut.
In balancing decisions of changes to road design,
VicRoads staff needs to consider the:
As outlined in the S.M.A.R.T model detailed below, goals
must be specific, measurable, achievable, realistic and
timely and agreed upon between biodiversity specialist
and project managers. Separate goals should be
developed to address the different target species
or types of impacts.
Table 1: The S.M.A.R.T model for assessing wildlife connectivity
Objectives
Key Questions
Specific
What species are concerned and
what are we trying to achieve?
Measurable
What is the criterion to measure
our success?
Achievable
Have the objectives been agreed
with relevant Stakeholders?
Realistic
Is there sufficient funding provided?
Time Frames
What is the end point?
Significance of the biodiversity impacted by the road.
Advice of DSE (and SEWPaC where relevant) regarding
whether approval of the unchanged design element
is likely.
The preferences of other stakeholders such as
‘friends of…’ groups and Local Councils.
Cost/benefit ratio of the design adjustment. (NB.
Ensure that any native vegetation or fauna offset
cost estimates are included in this analysis).
A project may evaluate numerous fauna sensitive road
design options (refer to Section 6) throughout the design
process and should consult with relevant stakeholders
such as DSE and local friends of groups to obtain the
best outcome.
3.2 Determining fauna sensitive road
design treatments
Once all assessments and analysis has been undertaken,
members from the project team should meet with both
the Regional Environmental Officer and the Biodiversity
Policy Officer from Environmental Sustainability to help
determine fauna mitigation outcomes.
The meeting will need to establish:
What are the expectations and what are we trying
to achieve?
Which fauna species have been identified in
target surveys?
Do the fauna structures under consideration improve
connectivity in the landscape?
Will mitigation methods encourage fauna movement
and reduce wildlife mortality?
The outcome of these discussions will influence what
fauna mitigation will be appropriate for the project.
Discussions will also need to identify realistic objectives
and targets in order to ensure the fauna mitigation is
practical, feasible and cost effective.
It is important that these goals and objectives be
discussed early in order to measure success of fauna
sensitive road design down the track.
Section 6 of this document outlines a number of
different fauna mitigation measures available to projects
to prevent access to the road, or to facilitate the
movement of animals from one side of the road to the
other. They include bridges, culverts, canopy bridges,
land bridges, fencing, habitat enhancement and local
fauna management. This information will help VicRoads
facilitate more feasible and practical fauna sensitive road
design going forward.
VicRoads currently has numerous existing crossings
which have had varying degrees of success. These have
used a combination of culverts, amphibian underpasses,
koala crossings and rope bridges.
Various studies have been conducted throughout
Australia to measure the success of different fauna
sensitive road design. Evidence has concluded that the
following treatments, used independently, have had
limited success rates:
Chemical replants.
Reflectors.
Signage – fauna crossing and reduced
speed limit signs.
Amphibian underpasses.
It is important that projects take this into account when
designing structures, and reviewing consultant reports.
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Fauna sensitive road design guidelines
3.3 Evaluate landscape objectives
Obtain design drawings
Once the project team have received the consultant’s
fauna and flora report and the targeted surveys, which
detail proposed options, and have discussed the goals
and objectives, the next step is to engage a consultant
to complete design drawings for these options. In some
instances this can also be done in-house. The design
should take into account the following:
Number, size, location, type of each
mitigation measure.
What additional landscaping, revegetation, fauna
furniture, and fencing is required with the structure.
Additional points that should be reviewed by the project
team in consultation with the consultant are:
Making sure the fauna structure is buildable.
Location of the fauna crossing should consider soil,
location and topography.
What is the overall cost to build the structure?
How often will fauna structures need to be
maintained, including making sure the overall cost of
maintenance has been calculated for transferring over
to the region.
Structures should have easy access for future
maintenance.
Any design should include the cost of landscaping
and revegetation around fauna crossings.
Consideration needs to be taken with regards to
likely fauna impacts if the project decided not to
incorporate fauna sensitive road design.
In some cases more than one fauna sensitive
structure may be required.
Alternative options should also be included and
considered. These may include fencing, deterrents
or nesting boxes for example.
3.4 Incorporate relevant biodiversity
management requirements into contract
specification
VicRoads contract shell briefs provide standard clauses
that aim to ensure that environmental impacts are
addressed by the contractor. The extent of these
varies depending on the contract type and will usually
involve minimising areas of native vegetation removal
and establishing no-go zones. It is at this stage where
projects add additional contract specific clauses to
address any biodiversity or fauna specific aspects
significant to the particular project.
It is important to ensure that any fauna sensitive road
design requirements stemming from the planning
process, including any permit requirements or
Environmental Effect Statements (EES) outcomes, which
may impact on construction activities, are incorporated
into contract documents where relevant. For example:
Identifying preferred fauna mitigations.
The types of preferred fauna crossings.
The number of crossings to be installed.
Contract specification clauses should be reviewed
(and preferably prepared) by someone with appropriate
biodiversity knowledge. Projects that are unsure should
seek advice for either the Regional Environmental
Officers and/or Environmental Sustainability
Biodiversity Officer.
Prior to handing over all the information to the Delivery
team, a project should ensure clear details are provided
in VicRoads Project Environmental Protection Strategy
(PEPs). Additionally, any specific requirements should be
detailed in the contract specifications relevant to fauna
mitigation. This may include, for example, putting aside
removed trees as fauna habitat, specific fauna monitoring
requirements, recommended design treatments, and
translocation or relocation recommendations.
At this stage of the project, the planning and design of
fauna sensitive road design is largely complete. There is
limited ability to change the design once construction
begins. There is also a limit to the amount of funding
available to change or add to fauna mitigation at this
stage, especially if any issues have not been identified
during the planning and design phase.
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4. Construction
4.2 Fauna protection during construction
4.1 Contractors Environmental Management
Plan (CEMP)
In order to ensure that protection of fauna occurs during
the pre-construction and construction stages, there
should be a predetermined number of site inspections
carried out by the project Environmental Officer.
It is important to ensure that the contractor has
incorporated all biodiversity objectives, including any
fauna sensitive road design requirements, into their
Environmental Management Plan.
In general the Contractors Environmental Management
Plan (CEMP) should include the following:
All fauna sensitive road designs identified during
the planning stage.
All relevant information regarding the fauna
sensitive road design including flora/ fauna
assessment reports, targeted surveys and
landscape plans (including information that
identifies connectivity between habitats).
Required ‘no-go zones’ including available
habitat for fauna during construction.
Matters to be monitored and reported should include
all recommended fauna mitigation identified in the PEPs
and CEMPs. It should be noted that the requirements for
each project will be different depending on the proposed
impacts of construction activities. Any changes to site
conditions or impacts which may arise from changes
should be updated in approved plans.
If a non-compliance with fauna safety measures occurs,
a timeframe for compliance and remedial works should
be specified by the Contractor and signed off by the
VicRoads Contract Superintendent. All incidents that
arise on site should be recorded in VicRoads Enviro
Tracker system available on Exchange: How To>Build
and Maintain Sustainable Roads.
Requirements for planting and rehabilitation at the
end of construction including providing adequate
connectivity and in accordance with landscape plans.
The project Environmental Officer should monitor the
impacts of demolition, earth works, and installation of
temporary infrastructure including site fencing, drainage
works and vegetation removal works.
It is important to note that CEMPs are essential for
construction, maintenance and monitoring contracts
and should ensure all fauna sensitive road design
maintenance and monitoring requirements are
adequately addressed by VicRoads.
Monitoring of construction works should occur at regular
intervals and in consultation with the site manager to
check fauna protection is adhered to on site at all times.
Red Kangaroo (Source: ES Link Services)
14
Fauna sensitive road design guidelines
5. Managing and monitoring fauna
sensitive road design installations
The long term maintenance and monitoring of installed
fauna sensitive road design treatments is important to
verify if the installation has actually been successful.
The success of fauna mitigation is measured in terms of:
Compliance.
Maintaining landscape connectivity.
Use of the structures by fauna.
Ongoing success is dependent on maintaining
installations. Projects and Regions should make sure that
funding is available for fauna mitigation maintenance.
5.1 Ongoing monitoring surveys
Post construction monitoring determines whether
fauna species are actually using the structures put
in place. Factors such as population dynamics and
behaviour may influence the outcome of it success
of the structure. This monitoring also helps VicRoads
to develop a better understanding of which structures
work best in varying situations.
Monitoring of connectivity measures can:
Improve our understanding of the effects that
proposed roads and expected traffic volumes
may have on wildlife.
Ensure wildlife mitigation methods are evaluated
on the effectiveness in maintaining connected
landscapes.
Assess value for money by measuring the success
of the outcome.
Quantify potential impacts of roads on wildlife.
Failure to undertake monitoring may impact and
jeopardise the success of fauna mitigation in road
design. This is particularly important in the long term
as monitoring also identifies previous failures.
More often than not consultants will recommend the
need for a number of studies after the implementation
of fauna structures. This requirement can often be
time-consuming and expensive for projects to
implement. Before committing to ongoing monitoring
it is the responsibility of the project, Regional
Environmental Officer and Biodiversity Policy Officer
to understand what the overall objectives are for postconstruction monitoring.
In some cases, if the previous planning steps have
been correctly followed, and the right structures
have been implemented, then monitoring may not be
required. For example, the state of the science is such
that for some species we already know that culverts
will facilitate the movement of individuals across roads.
VicRoads along with other States road authorities now
have a number of reports in place supporting a good
knowledge based on the effectiveness of previous
fauna structures.
Monitoring has shown that at least 23 species of native animals
have used this wildlife crossing under the Slaty Creek Bridge,
Calder Highway at Macedon. The crossing connects two large
patches of remnant vegetation (Source: VicRoads)
15
6. Fauna sensitive road design
There are a number of different fauna mitigation
measures available to facilitate the movement of animals
from one side of the road to the other they include;
bridges, culverts, canopy bridges, land bridges, fencing,
habitat enhancement and local fauna management.
6.1 Underpasses
An underpass is a structure that allows wildlife to cross
the road beneath the road surface. It includes culverts,
tunnels or pipes, bridges and viaducts. The size or
“openness” of the underpass appears to be the primary
factor influencing crossing rates. Wherever possible, the
height and width of underpasses should be maximised.
6.2 Bridge underpasses
Of the various wildlife crossing types available, the bridge
underpass is acknowledged as the most effective but also
the most costly. The structure maintains the grade of the
road or elevates the traffic above the surrounding land,
allowing animals to pass under the road. Bridges typically
traverse watercourses and can be the chosen preference
when building a road through flood-prone areas.
A few factors to consider when choosing this
option for fauna mitigation include:
Different types of bridges can be used to
accommodate a number of fauna species including
both terrestrial and aquatic. Bridges are suitable for
a vast array of fauna including fish, crustaceans,
platypus, native water rats, small to medium sized
marsupials, frogs, flightless birds (emu), large
macropods (kangaroo) and reptiles.
In general, the bridge crossing should be designed
to accommodate koalas and larger macropods such
as kangaroos.
If accommodating larger macropods, the bridge
crossing should provide a minimum clearance of
three metres in height with a span of 10 metres.
Smaller spans are suitable for smaller species such
as echidnas, wombats, reptiles and bandicoots.
Bridges can be built to encompass both water bodies
and dry passage to allow for both terrestrial and
aquatic fauna movement.
For dry passage, a minimum of three meters will
support the movements for most terrestrial animals.
When designing bridges, projects should consider two
lanes where possible, as the gap between lanes (Figure 4)
allows the continued ingress of light to the forest floor,
allowing plants to continue to grow. Projects should
also consider providing shelter (e.g. logs, rocks and
leaf litter). This is particularly important when designing
underpasses for target species.
Finally, it is important that projects implement
appropriate fencing in conjunction with bridge
underpasses. Correct fencing guides fauna to the right
locations allowing them to cross under the roads safely
and reducing roadkill (refer Section 6.3 page 30).
Bridge limitations
Figure 4: Two lanes, Slate Creek Underpass, Calder Freeway.
Very high cost.
Needs to be located within a known fauna
movement corridor.
Requires targeted landscaping and fencing.
May require other structures or retention of large
trees to encourage usage by arboreal fauna.
It may be difficult to establish vegetation under
some structures.
16
Fauna sensitive road design guidelines
6.3 Culverts for terrestrial animals
A culvert is largely used to channel water under roads,
railway lines and embankments. They come in many
shapes and sizes including round, square, rectangular
and arching. Culverts can be made of a variety of
different materials with steel, polyvinyl chloride (PVC)
and concrete being most common. In the right situation,
culverts can be designed to accommodate and be
modified to allow for wildlife passage.
The culvert is typically a three metre x three metre
precast concrete unit positioned on a cast in-situ
base and located along ephemeral lines, thus serving
as a drainage culvert as well as potentially a wildlife
underpass. Ideally the length of a culvert should not
exceed 25 m to allow light penetration and avoid a cave
like appearance which can often deter animals from
moving through the system.
Where possible projects should maintain a practical
‘openness measure’ when designing culverts to
accommodate wildlife movements.
Further factors to consider when designing wildlife
friendly culverts:
The openness of the culvert will need to increase
as the culvert length increases.
Culverts are best located in areas where the road
has been built on fill.
Three metre x three metre box culverts are
considered optimal for allowing the movement
of a wide variety of fauna including (macropods,
koalas and flightless birds).
Incorporate appropriate fencing to help guide
fauna to culverts.
Culverts which have been designed to drain
floodwater, should not retain water after flood events.
Culverts that retain water are ineffective as the
water deters terrestrial fauna from moving through
the structures. If this is likely to be a problem, then
projects should consider multi-celled systems (see
Figure 10, page 19).
Figure 5: Standard culvert with natural substrate.
(Source: Transport Roads and Maritime Services,
Wildlife Connectivity Guidelines. November 2010).
As discussed in Section 6.4 provided water movements
on creek and river flows are not impeded, correct culvert
design can accommodate a number of aquatic species
including native water rat and platypus.
When designing culverts, projects should consider the
types of species they expect to accommodate. For
example, larger culverts are suitable for a number of
fauna species including low flying birds, small flightless
birds, bats, invertebrates, macropods, reptiles and small
to medium mammals. Small-medium sized culverts are
more suitable for animals that are familiar in underground
or burrowing environments, these species include
wombat and echidna.
Entry landscaping
It is very important that culverts retain as much of a
natural appearance as possible. Projects should make
sure that vegetation is established as close as possible
to the ends of the culverts; this would also include small
local logs, rock and natural leaf litter (refer page 20).
Terrestrial culvert limitations
high cost
cannot be used where the road is in cut
should not be used where the total tunnel length
is greater than 25 metres
might encourage the predation of some fauna
requires the added costs of targeted landscaping
and fencing to encourage fauna use.
17
Culvert furniture
Culvert furniture installed correctly can facilitate the
movement of arboreal species such as possums sugar
gliders and even koalas in larger culverts. By providing a
dry ledge or similar structure that allows arboreal species
to move through the landscape, dual purpose culverts
can provide safe passage for a variety of fauna species.
Substrate design
Culverts without dry ledges or poles are known
to be avoided by arboreal fauna.
Substrate design is important when considering
ground dwelling species; culvert furniture should be
designed to encourage a number of small mammals
and reptiles. Underpasses are more likely to be used
by fauna if the base is a natural substrate such as
dirt or mulch. Likewise, culverts that hold water over
extended periods or are often muddy often deter
use by some species. Ideally if the area is known or
likely to be wet then a multi-level culvert should be
considered or culverts should be shifted slightly to
drier locations.
Horizontal logs placed strategically in culverts can
provide dry passage for a number of species whilst
providing refuge from predators.
General furniture for reptiles and small
marsupials include:
VicRoads Projects and Regions should consider
the following when adding furniture to culverts:
Include horizontal and vertical poles and netting
attached to pylons where appropriate to
target species.
Place horizontal logs for passage as high above
the base of the opening as practical, allowing
1 metre clearance from the culvert ceiling.
Tiles, logs, mulching and rocks.
Note: you can add too much furniture to culverts.
Fauna friendly culverts need a healthy balance of open
ground, small rocks and logs. Too many large rocks for
example can deter animals as well.
Vertical logs should be secured to the invert of the
base of the underpass using attachment brackets.
Arboreal species will only use large culverts three
metres x three metres or greater. Anything smaller
will not be used by these species due to the treat
from predators and because they prefer not to
travel along the ground where possible.
At either end of the culvert, lead-up logs should be
used to allow movement of species. Ideally lead-up
logs should connect to trees or other off ground
structures, so arboreal species can move freely while
avoiding the ground and possible attack by predators
(refer to Figure 6 below).
Figure 6: If correctly positioned, arboreal species such as koalas and possums should be able to move
through structures and along horizontal logs without going on the ground.
18
Fauna sensitive road design guidelines
Large culverts
Multiple culverts
For larger culverts under four or six lane roads, it is
preferable to provide a break in the middle of the culvert
(if a median exists), to maximise the amount of natural
light entering into the culvert. Strategically placed light
wells may also be used to achieve this (refer Figure 7).
Installation of several underpasses at one location
deceases the possibility of interference caused by other
fauna movements, including predators such as the fox.
In some cases there may be a requirement of projects
to build culverts for targeted species (refer Appendix A).
Light wells should be built higher than the surrounding
ground, and should never be designed with drainage in
mind. Ideally water should flow either side of the light
well ensuring the culvert stays as dry as possible.
Any water that does enter these culverts should drain
quickly away.
Small culverts will only be used by smaller animals
such as echidna, bandicoot and reptiles (refer Figure
8). Multiple underpasses also increase opportunities for
species interaction by providing alternative routs and
decreasing travel time from one side of the road to the
other. Small culverts should have entrances as natural
as possible and be free of human disturbance and
artificial light.
Light wells are good for providing natural light in long
culverts however there is the potential ‘especially if
poorly designed’ that they become a focal point to
collect litter, road pollution, and increase noise with in
the structure. Some studies question the effectiveness
of light wells so projects should seek expert advice if
such structures are being considered.
Fencing
It is important that culverts are constructed early
before erection of permanent fencing, as with all
wildlife crossings fencing helps funnel fauna to the
underpass (refer Figure 8). Fencing is discussed further
in Section 6.3 page 30.
It is possible to plant out some small vegetation in
the middle of a culvert as long as plants get maximum
exposure to sunlight and rainfall. Vegetation (if possible)
is culvert furniture alongside rocks, logs and mulch and
could provide safety for native fauna against predators.
Figure 7: Cross section of a multi lane culvert. The light well
in the middle of the median allows natural light to entre a long
dark culvert. Also the well is built higher than the surrounding
ground, so water does not drain into the culvert.
Figure 8: Small culverts are used by small mammals and reptiles,
while fencing is important in funnelling wildlife
to underpasses.
19
Fauna culverts along waterways
Wildlife is known to traverse along creeks and rivers.
Water is important for terrestrial fauna especially in
Australia’s dry climate. Roads built over creeks and rivers
often have culverts that maintain water flow or drainage,
but very rarely consider the need for wildlife to move
through the landscape.
In such scenarios, terrestrial fauna is forced to move
up embankments and across roads, leading to increases
in fauna mortality. Fauna culverts along creeks should
be designed with three factors in mind:
maintain water flow
encourage the movement of aquatic animals
maintain terrestrial fauna movement.
Culverts along creeks should be created in as natural
a condition as possible with rocks, logs and riparian
vegetation. Ideally the raised embankment should always
be designed above the main water level (refer Figure 9).
Obviously these embankments will be subject to flooding
from time to time however the designs should ensure
that water drains away quickly allowing the ground to
dry out. Embankments which permanently hold water
or are extremely muddy will deter fauna from moving
through culverts.
Again, natural substrates including rocks, logs and bare
ground are preferred over concrete bases. In this case,
projects should avoid using mulch. Mulch is problematic
in such environments due to the risk of flooding. Finally,
this type of design can make life easier for maintenance
teams needing to access the culverts in the future.
Factors to consider when designing culverts for
terrestrial fauna movements along creeks:
Culverts should be made as wide as possible to
encompass water flow, stream bank and riparian
vegetation, preferably on both sides of the
water course.
A raised section should be considered on both sides
of the creek, encouraging terrestrial fauna
movements.
If the culvert width is narrow, it is better to design one
embankment wider than the other, rather than have
two narrow embankments.
If it is difficult to have two embankments, then one
embankment is better for terrestrial fauna than
providing nothing at all (refer Figure 9).
Figure 9: The raised walkway in this example caters
for both aquatic animals and terrestrial animals.
Figure 10: Series of box culverts with varied floor levels maintain
both creek flows, while allowing dry culvert passage for
terrestrial wildlife passage.
20
Fauna sensitive road design guidelines
Approaches to crossings
The entrance to a culvert is very important in
encouraging wildlife to use fauna mitigation structures.
Ideally, projects should retain as much natural vegetation
as possible and cause minimal disturbance to the
corridor link they are trying to maintain. At times when it
is too difficult to avoid disturbance, careful consideration
should be taken in order to establish as natural a
landscape as possible at the approach to crossings.
The entrance to culverts will need to be enhanced by the
provision of ‘furniture’ including habitat logs and refuges
within the corridor, including the placement of standing
dead hollow bearing trees or ‘stags’ (refer Figure 11).
In some locations it may be necessary to encourage
connectivity with additional indigenous plantings.
Extensive planting should consist of a variety of species
and mimic existing bushland type and Ecological
Vegetation Class (EVC), and plantings should be shaped
to encourage wildlife towards the crossing points.
Strategic habitat creation will enhance the overall
effectiveness of wildlife connectivity and can re-connect
important parts of the landscape away from the road.
Factors to consider when designing the approach
to culverts:
Most plants are a food source of native animals
or attract food such as insects which other species
feed on.
Important or preferred food strategically planted
in corridor links can be used to tempt animals near
or into crossing structures.
Habitat restoration should typically use
indigenous stock.
Some plantings can change dependent on targeted
species or species specific requirements, e.g. for
smaller animals more thick ground cover plantings
with some open spacing should be considered.
For reptiles, more rocks and logs should be placed
in and around culvert entrances.
Culverts for animals
Avoid humanising wildlife friendly structures. Culverts
and bridges that encourage humans and their pets to
walk in, near or across can often discourage
wildlife. Culvert entrances should be free of human
disturbance and artificial light. Close vehicle access
should be considered however for on-going
maintenance requirements.
Figure 11: Landscaping with rocks, logs and revegetation help funnel fauna into culverts.
21
6.4 Culverts to aquatic animals
Locating aquatic crossings
The location of aquatic crossings for species movement
is very important . Ideally, the primary objective during
the planning and investigation stage of a project is to
minimise the total number of road crossings across
creeks and rivers. When locating aquatic crossings,
the following principles should be considered:
Avoid crossing waterways near sharp bends, sections
of unstable banks or naturally strong “riffle” systems.
Riffles are shallow rocky shoals or sandbars lying
just below the surface of the waterway. These areas
act as natural important bank stabilisers and often
provide essential habitat pools. Any alteration of these
systems may impact habitat, change bank stability and
potentially initiate severe riparian erosion.
Avoid locating crossing in areas where the river
is likely to continue meandering into the future.
Naturally meandering rivers undergo natural
reshaping and erosion, especially during times of
strong flow. Meandering rivers cause maintenance
headaches as changing waterways can damage
structures such as culverts. Future misalignment
of the channel crossing may result from natural
reshaping, rendering culvert and aquatic mitigation
structures pointless.
Avoid works that change the frequency and spacing
of existing natural habitat pools and riffle systems.
Avoid the removal of essential shade trees, especially
in areas which have already lost a lot of natural
vegetation cover.
Road construction can have a significant effect on
streams and rivers. Vegetation removal causes enhanced
runoff and soil erosion leading to sedimentation of
natural waterways, generally modifying stream hydrology.
These changes have adverse effects on natural remnant
vegetation and habitat. Projects should avoid disturbance
to sections of a waterway channel or its associated bank
vegetation, particularly where such areas represent either
a unique, endangered or highly valued section of the
water way.
Figure 12: Roads and bridges should be place in areas
that are least likely to have environmental impacts.
22
Fauna sensitive road design guidelines
Culvert designs
When designing culverts for aquatic species most people
naturally think about fish. However Australia’s creeks and
rivers are home to a number of aquatic species including
platypus, native water rats, crustacean and turtles. Where
possible, culverts under creeks and rivers should be
designed to accommodate the movements of aquatic
species and not impede movement from one side of the
road to the other.
Fish passage along our waterways is critical to the
survival of Australian native fish. Of the 83 species of
freshwater fish in southeastern Australia, half migrate at
least once as part of their life cycle. These include; Silver
perch, Murray Cod and Dwarf Galaxias.
Factors to consider when designing culverts
for aquatic species:
Culverts that are not as wide as natural stream
beds restrict water flow and therefore increase
water velocity. This is detrimental to fish passage
as a majority of fish cannot maintain strong burst
speeds for long enough to swim to the other side of
the culvert if the distance is too great. In this scenario,
fish tire before they reach the other side and are
swept back downstream (refer Figure 13).
Small culverts are dark and easily get blocked
with debris, blocking aquatic species movements.
Ideally, culverts should be less than six meters long
especially when no resting areas are available and
given that water velocity is likely to increase after
the construction of new structures.
Maximise natural light by making the dimensions
of culverts as large as possible. Large diameter
culverts provide easy access and are easier to
maintain. Also, the wider the culvert the easier
it is to maintain natural flows.
Baffles
Consider installing baffles on one or both sides of the
culvert (refer Figure 14). Baffles are appropriate for new
culverts designs and projects should seek expert advice
to ensure correct placement.
Baffles act as energy dissipators, slowing water velocity.
They also change the flow pattern in the vicinity of the
culvert, creating zones of fast and slow moving water
zones. This allows fish to use short bursts of energy
while allowing periods of rest.
For multiple parallel culverts, only those fitted near
stream beds should be fitted with baffles (see Figure
10 on page 19).
Figure 13: Water velocity is important for fish movement
upstream (Source: QLD Transport and Main Roads (June 2010)
Fauna Sensitive Road Design Manual Vol 2).
Figure 14: a) A baffle design in a pipe culvert b) Cross–section
of baffles installed on both sides of a culvert. (Source: QLD
Transport and Main Roads (June 2010) Fauna Sensitive Road
Design Manual Vol 2).
23
Culvert rehabilitation
Fish ladders
Existing culverts can be rehabilitated to encourage
aquatic fauna movement, especially fish. One of the
biggest problems with some existing culverts is their
inadequate design and its impact on water level across
inlet and outlet. In these circumstances, water flow varies
from being high and flowing fast during high flows and
low water levels during dry periods. Existing culverts
can be rehabilitated to improve fish passage conditions.
Actions can include:
Fish ladders are structures on or around artificial
barriers such as culverts and weirs and can be used to
facilitate natural migration. The velocity of water falling
over the steps must be great enough to attract the fish
to the ladder, but cannot be too strong that it washes
fish back downstream or exhausts them to the point
that they can’t maintain the energy needed to move
through the stream system. There are several types
of fish ladders including:
Upstream modifications to improve flow in to culverts
by raising low flow water levels within culverts.
fish pools
Where high flow velocity is a concern, baffles could
be installed. This would change flow regimes and
provide various slow and fast water zones.
rock Ramps.
Upstream channel modifications could remove the
issues associated with deep drops or excessively
steep rock ramps.
Culvert maintenance
Maintenance for culverts is important and should be
considered during the planning stages of projects. Funds
will need to be made available at the project bid stage
and handed to regions once the project has moved on.
Culverts designed for aquatic species movement in
general require more maintenance than culverts for
terrestrial species. Creeks and rivers in flood or flowing
fast can move large bodies of water and are renowned
for picking up and moving debris such as vegetation,
wood, litter and even rock over great distances. This
process blocks culverts and can act as a barrier for
aquatic wildlife. Maintenance requirements for aquatic
culverts include:
fish elevators; and
Rock ramps
In Australia, rock ramps are commonly used to facilitate
fish movements and are a good tool for slowing water
velocity down and encouraging fish movement through
culverts. Rock ramps are constructed by placing large
rocks within streams to form a fish ladder type system.
Gradient and designed are determined by maximum
swimming speeds of various fish. Full width rock ramps
are optimal but partial rock ramps are most common.
Rock ramps cater for a variety of fish behaviour and
movement patterns and allow mitigation even during
low flow.
Controlling silt buildup and undertaking inspections
annually as a minimum.
Ensuring vegetation and weeds don’t become
established at entrances to culverts.
As a minimum, maintenance should be ongoing
and occur annually.
Substrate
The substrate should be as natural a possible and
incorporate a wide range of furniture including; large
rocks, deep pools and fine gravel. Where possible,
consider using a three sided culvert with no base.
This maintains a natural streambed instead of hard
concrete base and is more attractive to some species
such as water invertebrates, fish, crustaceans and
platypus. Furniture must not adversely impede water
flow but can be considered in culverts where water
velocity is a problem.
Fish ladder under construction (Source: VicRoads)
24
Fauna sensitive road design guidelines
6.2 Overpass
6.2.1 Canopy bridge
Whilst surface crossings, culverts and bridges address
the needs for ground dwelling fauna, a new road can
introduce a significant break in tree canopy, particularly
along existing vegetation linkages. Canopy bridges
provide for genetic connectivity, dispersal
movements and home range movements. When
designed correctly, daily crossings by some individuals
are common.
Target animals for cable crossings include possums,
phascogale and sugar gliders. There is even evidence
of some arboreal reptiles such as lace monitors using
canopy bridges.
Typically, a canopy bridge consists of a woven
polyethylene cover over a 12 mm diameter steel cable.
The polyethylene provides a surface that allows animals
to secure grip. The cable is supported either side of
the carriageway at the end of the mid point by tension
cables. The tension cables help keep the canopy bridge
clear of traffic lanes and reduce whip. At the mid point
a hooded protective cowl will offer animals refuge from
airborne predators (refer Figure 18 page 26).
Ringtail possum on Hume Highway Rope Bridge
(Source: VicRoads)
Factors to consider when designing canopy bridges:
Canopy bridges must be linked to canopy vegetation.
If targeting specific species, then canopy bridges
should be placed near known habitat trees.
Supports can usually be constructed using recycled
materials such as old electricity poles.
Suitable poles should be placed behind fauna
proof fencing and at a safe distance away from
the roads edge.
Safety requirements must be complied with when
structural supports are placed in the median
(e.g. wire rope barrier).
Crossing opportunities should be provided for
possums every 100-120 metres when possum home
ranges coincide with the road corridor.
The distance between the road and canopy bridge
should be maximised. Ideal minimum distance
from the road is seven metres with a maximum
of 12 metres.
Canopy bridges are shown to be quite successful
in encouraging arboreal movement across roads.
Some studies may recommend building a four sided
rope tunnel (refer Figure 15) however this design is
probably not necessary because most animals generally
don’t climb through such structures and instead
traverse along the top.
Figure 15: Generally there are two types of rope structures,
one is a rope tunnel and the other is a rope ladder. Studies and
monitoring indicate that the tunnel though still doing its job is
less effective because arboreal species such as possums only
cross on top. (Source: QLD Transport and Main Roads (June
2010) Fauna Sensitive Road Design Manual Vol 2).
25
Figure 16: Fauna crossing detail – not to scale.
When designing canopy bridges consider
the following safety requirements:
Potential conflict with powerlines
and other service infrastructure.
Roadway safety and clear zone requirements.
Design must not impede the safety of road users.
Ideally, poles should be placed behind fauna fencing
in vegetation with connection to trees. In the diagram
above the cowl attached to the pole in the median
ensures animals are unable to descend in the middle
of the road between traffic lanes.
26
Fauna sensitive road design guidelines
Figure 17: Typical cable end cowl and optional record Pad (not to scale).
Figure 17 is an example of the type of cable end used for
canopy crossings on the Calder Freeway. It should be
noted that in this instance a replaceable record sheet
was included for the purpose of monitoring wildlife.
It is not always necessary to monitor canopy bridges for
their effectiveness as studies indicate that such structures
have already been proven to be successful in facilitating
arboreal movements.
Figure 19: Avian predator guard and PVC pipes for shelter on
support poles. (Source: NSW Transport and Maritime Services
(Nov 2011) Wildlife Connectivity Guidelines).
Figure 18: Fauna cable details (not to scale).
Possums, phascogale and sugar gliders once out in the
open are very exposed to avian predators such as owls.
Ideally all poles should have avian predator guards (refer
Figure 19).
Predator guards can be made of various materials
including metal, plastic or even shade cloth. Generally
predator guards should be placed 500 mm above the
rope ladder or cable.
For added protection, additional PVC pipes placed along
cross sections also provides predator protection.
Canopy bridge limitations
Minor cost of building but with maintenance
implications.
May be difficult to match cable design to suit
claws of various fauna.
27
Figure 20: Canopy connectivity is a form of non-structural mitigation (Source: QLD Transport
and Main Roads (June 2010) Fauna Sensitive Road Design Manual Vol 2).
Maintenance
6.2.2 Canopy connectivity
Maintenance for canopy bridges is important and should
be considered during the planning stages of projects.
Funds will need to be made available at the project bid
stage and handed to regions once the project has moved
on. Canopy bridges require regular maintenance of rope
tension to maintain clearance above the road and reduce
sway. Ropes that sway too much are likely to not be used
by arboreal animals such as possums. Other maintenance
considerations include:
The diagrammatic example above is a relatively
inexpensive way of maintaining canopy connectivity
in the landscape. Here, vegetation clearing is kept to
a minimum width allowing the tree canopy to remain
continuous, or where not continuous, small enough to
allow species like gliders to move across the road from
one side to the other. This type of mitigation is suitable
for a number of species including arboreal animals, bats,
birds and flying invertebrates.
Inspect on an annual basis as a minimum especially
after storm events (fallen trees etc).
Heavy vegetation should be pruned away from
wire ropes. Vegetation growing on ropes will add
stresses to the structures especially when the
vegetation is wet.
Ropes should be checked for decay and deterioration.
Landscaping
Where trees are unable to be saved during road
widening or maintenance, then VicRoads officers
should consider re-establishing trees through
landscaping. This is not ideal however as trees take
an average of ten or more years to develop a canopy
similar to the one destroyed. This time delay is critical
for some arboreal species that are endangered.
Without canopy connectivity, many of these species
face extinction due to a number of factors including
lack of habitat, reduced home ranges and /or genetic
inbreeding due to the barrier effects from roads
(Source: QLD Transport and Main Roads (June 2010)
Fauna Sensitive Road Design Manual Vol 2).
28
Fauna sensitive road design guidelines
6.2.3 Land Bridges
An overpass or land bridge is similar to an underpass,
except the road goes beneath the bridge which has been
constructed for wildlife. Land bridges are also referred
to as ‘green bridges’ or ‘ecoducts’ and can facilitate the
movement of a number of terrestrial and arboreal fauna.
Land bridges have been used in many countries across
Europe and North America and are considered a very
attractive option for facilitating movement of a large
variety of fauna to cross roads, from invertebrates to
large fauna.
In Australia, there are two known land bridge crossings
used to re-establish connectivity. These include; the
Yelgun to Chinderah Project on the Pacific Highway in
NSW and Compton Road land-bridge in Queensland
(refer Figure 21).
Typically, a land bridge is more expensive to construct
than underpass mitigation. However in the right
circumstances there is the opportunity for land bridges
to incorporate other features such as the opportunity to
pass over drainage lines or gullies.
Factors to consider when constructing a land bridge:
Overpass structures vary in design and come in
various shapes and sizes including hourglass and
rectangular shapes.
Hourglass shape structures should be wider at
the entrance points and taper in towards the
arch of the bridge.
The best location for such structures is where
the road is already in cut.
Fencing should be used to funnel species to the
land bridge and prevent animals from falling on
to oncoming traffic.
Evidence suggests that rather than using one or two
large land bridges, a greater number of smaller land
bridges are preferred.
Land bridge furniture
If designed correctly, land bridges are suitable for
a large variety of wildlife. All land bridges should
incorporate soil, vegetation and be enhanced with
other habitat features such as logs, rocks and even
shallow water bodies. For optimal vegetation growth
and longevity of the projects objectives, soil should be
made as deep as possible. The ideal depth of the soil
will depend on the type of vegetation planted e.g. 0.3
metres of soil for grasses, 0.7 metres for shrubs and
1.5-2 metres soil for trees. Ideally the design should
mimic surrounding bushland or EVC and should
include a mixture of indigenous vegetation.
Some other furniture to consider in land bridge
design might include:
Most plants are a food source of native animals
or attract food such as insects which other
species feed on.
Important or preferred food strategically planted
in land bridges can also be used to tempt animals
near or into crossing structures.
For reptiles, more rocks and logs should be placed
along the stretch of the land bridge.
Consider building a water body such as a wetland
at either side of the structure. Being a dry climate,
water is important in the Australian landscape.
Placing water bodies at each end will encourage
a vast array of animals as they will be drawn to
the water for drinking.
Wetlands can be designed as frog habitat;
encouraging frogs to move over land bridge
structures (refer Section 6.4).
Target species
Land bridges provide one of the most natural crossings
for fauna, particularly disturbance sensitive species.
All species, excluding aquatic use the structures including
kangaroo, wallaby, koala, wombat, echidna, bandicoot,
possums, reptiles, birds (especially emu and Malleefowl),
bats and frogs.
Figure 21: Compton Road land-bridge is a great example
of land bridge design in Australia. Photo: L Harrison
(Source: NSW Transport and Maritime Services (Nov 2011)
Wildlife Connectivity Guidelines).
29
Land bridges for animals
Land bridges that encourage humans and their pets to
walk in, near or across can often discourage wildlife.
Where possible avoid the development of walking
or bike paths. Domestic dogs and cats deter native
wildlife. Land bridges or ecoducts should be designed
with the interests of wildlife in mind.
Maintenance
Figure 22: Wildlife Crossing on the 26 Motorway in the Hardt
Forest in Germany. Javier Martinez de Castilla, Head of the
Environmental Department, Ferrovial Agroman.
Consideration will need to be made for ongoing
maintenance and should be included in the Total
Estimated Cost during the planning stage of projects.
Once handed back to regions, ongoing maintenance
should include:
Minimum yearly and annual maintenance as required.
Design specifications
The success of land bridges is dependent on a number
of factors including width, fauna exclusion fencing,
vegetation, noise disturbance, suitability of vegetation,
provision of artificial shelter and minimised human
disturbance. Currently no standard design principles
have been established in Australia.
Within the first few years, landscaping should be
checked for survival rates, and money set aside for
any failures.
Possible ongoing maintenance for other furniture
including any canopy bridges.
Land bridge limitations
Very high cost.
As a rule of thumb, the following principles should
be considered:
Design is dependent on the purpose of what is
trying to be achieved. Topography, environmental
surroundings, target species, climate should all be
factored into the designs. For example, birds and
larger terrestrial animals such as kangaroo and koala
would prefer a wider bridge.
50 metres or greater width will be used by the widest
variety of species and provide as natural a connection
as possible for animals to exhibit natural behaviors.
Narrower bridges will be used by more targeted
species. The minimum width required is around
5 metres.
Bridges should be located in areas of high wildlife
traffic areas, and should consider all animals including
birds, invertebrates, bats and reptiles.
Approach embankments should be 1 in 3 gradient
and vegetated.
It is important to seek specialist advice when considering
such structures. They are very costly to implement, and
projects spending such a large amount of money would
need to make sure they achieve the goals and objectives
of fauna sensitive road design.
For land bridges, fencing is important. Fencing both
funnels wildlife to use the structures and prevents
animals from falling into traffic below. For further
information on fencing (refer Section 6.3, page 30).
Not yet trialed in Victoria.
High cost for ongoing landscaping and maintenance.
30
Fauna sensitive road design guidelines
6.3. Fencing
Small animals
Fencing forms an integral part of the operation of the
wildlife crossings. When deigned correctly, fencing can
direct fauna to the right crossing locations and prevents
animals from accessing the road. Fencing should be used
along both ends of fauna structures in order to prevent
animal-vehicle collisions.
Both fences discussed in this section have large
mesh that will not prevent smaller species such
as lizards, snakes and frogs from climbing through.
A fence with large mesh for large animals can include
fine mesh at the base to prevent small species from
climbing through.
The type of fencing required changes depending on
species specific requirements. As a general rule the
following basic types are considered acceptable.
All fencing requires a clearance of at least three
metres on the forest side of the fence.
Mesh size for amphibians is less than 4 mm.
Mesh or metal sheeting for smaller species
should be made 400 mm–600 mm high.
Figure 23: Calder Freeway fencing, note the metal sheeting
to stop climbing species such as koala from entering the
road reserve.
Figure 24: Pinned down skirt, Photo: Rodney Abson
(Source: The use by vertebrate fauna of the Slatey Creek
a Wildlife Underpass, Calder Freeway, Black Forest,
Macedon, Victoria).
Kangaroo and Koala resistant fencing
This type of fencing involves a 2,100 mm high standard
chain mesh fence to prevent larger types of wildlife
entering the road reserve. The top 300 mm of the fence
is not secured and is bent over in the form of a ‘floppy
top’. Climbing animals tend to find the floppy top difficult
to negotiate and will either let go or back down. The
fence also has a 600 mm pinned down skirt on the forest
side of the fence to discourage burrowing animals (refer
Figure 24).
This type of fencing will not stop small animals as
the mesh size is approximately 50mm square.
Arboreal resistant fencing
Arboreal resistant fencing is typically made of 1,800 mm
high with the bottom 1,200 mm made of 20 mm square
chain mesh and the top 600 mm rolled metal sheeting.
The smaller mesh prevents passage of adult species
such as possums, sugar gliders and phascogale, while
the metal sheeting discourages climbing. Again, the
fence has a 600 mm pinned down skirt to discourage
burrowing animals (refer Figure 24). This type of fencing
has to be placed in areas known to be frequented by
arboreal animals.
Avoid fencing with barbed wire. Arboreal animals such as
the squirrel glider pictured right can become entangled
in barbed wire fencing.
Squirrel glider mortality, Photo: Rodney van der Ree
(Source: NSW Transport and Maritime Services [Nov 2011]
Wildlife Connectivity Guidelines)
31
Frog resistant fencing
Frog resisting fencing is 400 mm high and dug into the
ground at a depth of at least 100 mm.
The most important factor in determining the success of
frog fencing is the design of a pre-fabricated galvanised
lip along the top of the fence. Materials can consist of
recycled polyethylene sheeting with galvanised star
pickets or plastic Square Hallow Posts (SHS posts),
galvanised roof purlin and galvanised SHS posts or
fine wire mesh of less than 4 mm in diameter.
Overseas studies in relation to use of underpasses or
tunnels by frogs have shown that frogs have difficulty
in finding these structures if fences are not installed.
Frog fencing should be used along both ends of all
underpasses and culverts. Amphibian fencing must
take into account the climbing and digging capabilities
of the target species. Vegetation ideally should be
cleared 1 metre either side of the fence.
Figures 25 and 26 demonstrate the principles
of frog fence design.
Keeping fencing clear
Vegetation plays an important role in the success
of frog fencing. Grass and plants which are allowed
to grow up and over frog fencing will be ineffective
in preventing frogs going onto roads. Frogs are
good climbers and so will more than likely climb up
vegetation avoiding the fence. Projects need to take
ongoing maintenance into consideration and factor
these costs before hand over to the region.
Maintenance
Fencing should always be built using solid quality
products that are study, robust and durable. The better
the materials used in fauna sensitive fencing, the least
amount of maintenance is required going forward.
The following maintenance requirements will need
to be considered:
Maintain the three metre of vegetation clearance
“excluding” grass on the forest side of the fence.
Fencing will require regular inspection.
Fencing will require regular inspection and maintenance.
Vehicle access tracks adjacent to the fence will facilitate
rapid inspection and repair. Vehicles only require 1.5
metre clear-zone on the habitat side of the fence.
Fence limitations
Fencing is mainly associated with underpasses and
culverts, leaving large sections of road unfenced.
Escape from fire may be difficult.
Figure 25: Free standing frog fence (adapted from 3003181
-BFF-020-6003) (PacificLink Alliance 2006d).
All types require ongoing maintenance to ensure
ongoing success.
Unknown life span.
Figure 26: a) Frog fence attached to an existing fence (adapted
from 3003181-BFF-020-6003) (PacificLink Alliance 2006d) and
b) Cross-section of the fence (Source: QLD Transport and Main
Roads (June 2010) Fauna Sensitive Road Design Manual Vol 2).
32
Fauna sensitive road design guidelines
6.4 Habitat enhancement
6.4.1 Frog ponds
Regardless of the presence of key habitat characteristics
at a particular wetland, previous research has shown
that a landscape approach to habitat creation and
management is required . For example, it has been
shown that the likelihood of frogs occupying a particular
wetland is largely dependant upon the distance to nearby
occupied sites. Therefore any frog ponds designed by
VicRoads must be located within close proximity to
existing populations. Generally speaking, studies suggest
that frogs are highly dispersive and given the right
opportunity frogs have a high ability to colonise newly
created habitat.
The creation of frog habitat and the spatial location of
frog ponds are important. The following factors should
be considered when building frog ponds:
Banks
Wetland banks should vary in the degree and slope, from
areas of gentle undulation to steep banks that drop off
sharply. A variety of edge types and the provision of
different microhabitats such as rocks and vegetation
will also create a diversity of habitat.
Shape and size
There is no written rule with regards to the shape and
size of frog ponds. Preferably, ponds which are long
and narrow have been favored in the past, with frog
ponds on Pakenham Bypass being shown to be quite
successful (refer Figure 27). The longer and more
rectangular shaped the wetland is, the more the frogs
will have a high edge to area ratio, and smaller areas
of open water. A general guide for frog ponds applies:
20 metres x 5-10 metres for the smaller ponds;
no less than 40 metres x 10 metres in diameter
for larger ones.
This configuration maximizes the refuge area around
the wetland for frogs and provides a variety of
habitat sources.
Limitations
Generally only possible in areas with a wide
right of way boundary.
Cost may be high.
Limited opportunities due to limited availability
of land in some areas.
Vegetation
Vegetation should be structurally diverse, and areas
around the perimeter of the wetlands should be planted
with a healthy dense aquatic and semi aquatic range of
indigenous wetland species. As with all fauna mitigation
requirements, expert advice from amphibian experts
should be sought during the planning and design phase
of the project.
Landscaping
Figure 27: Packenham Bypass Growling Grass Frog Wetlands
and frog fence (Source:VicRoads).
Dense plantings of trees and shrubs should be
discouraged in close proximity to wetlands, because,
when established, this vegetation may shade out
wetlands, thus rendering them unsuitable for most
frog species. A healthy banks zone with a combination
of sun and shady spots should be considered.
The Growling Grass Frog is a common concern among
VicRoads Projects (Source: VicRoads)
33
6.4.2 Nesting boxes
Nesting boxes are specially constructed boxes that are
placed in trees to provide artificial habitat for hollowdwelling arboreal mammals and birds. The size of the
aperture of the nest box varies according to the species
being targeted (refer Figure 28).
In nature only very old trees provide hollows for arboreal
animals such as Feathertail Glider, Leadbeaters Possum
and Brushtailed Phascogale. For projects where the
removal of important habitat trees in unavoidable,
nesting boxes should be considered in order to replace
this lost resource. Design recommendations to consider
for nesting boxes include:
Highly valuable in some landscapes where nesting
location have become rare.
When a hollow tree is to be removed, carry out
investigations and note the species that potentially
utilize the hollows.
Ensure that replacement nest boxes are species
specific and appropriate for what the project team
is trying to achieve.
Different species utilise different heights and hollows
within trees and so require different styles of boxes.
The height of the nest box will determine its use. As a
rule most nesting boxes should be installed between
three and eight metres above the ground.
Consider the natural nesting habits of the species
under consideration.
Orientation
The orientation of nest boxes needs to consider a
number of surrounding environmental factors such
as wind direction, rainfall and the levels of exposure
to full sun.
For example, nesting boxes placed in the full sun
during the summer months would be far too hot
to support the animals you are trying to create the
habitat for.
On all occasions, it is best to seek specialist advice
with regards to the type of nest boxes required.
Natural nesting habits are species specific and will
require baseline surveys prior to the removal of
tree hollows.
All projects removing trees during construction
will require a qualified fauna specialist or ecologist
on site during clearing to ensure hollows and
replacements are removed and reinstated with
minimal impact and disturbance.
Maintenance
Considerations will need to be made for ongoing
maintenance and should be included in the Total
Estimated Cost during the planning stage of projects.
Maintenance considerations include:
nesting boxes can be damaged during fire and storm
events and will need to be monitored and replaced
control exotic pests including European Wasp
and feral birds
check annually to maintain success
Nest box limitations
Vulnerable to invasion by pest species like
bees and exotic birds.
Monitoring and maintenance required for success.
Figure 28: Sugar Glider using a nesting box provided
after road construction (Source: VicRoads).
34
Fauna sensitive road design guidelines
6.4.3 Traffic management
Traffic management is one of the cheapest forms of
fauna mitigation on roads. Numerous methods can
be incorporated to change local driver behaviour
including road signage, reflector lights, rumble strips
and road closures.
Traffic management is suitable for all animals where
traffic volumes and speed contribute to high levels of
roadkill. In Victoria, warning signage is the most common
method used to reduce fauna mortality on roads.
Limitations
Reduces but does not eliminate risks of roadkill.
Not likely to be practical on highest speed roads
or roads with high traffic volumes.
Success of permanent signage in reducing
roadkill and public awareness diminishes over
time, particularly with local residents familiar
with the signs.
The effectiveness of traffic management is dependent
on a number of factors including:
Adjusting driver speed by installing temporary
or permanent reduce speed signs.
Speeds may be signed or advisory.
Warning signs are most suitable for roads
with low traffic volumes.
Speed reductions are best achieved when used with
other devices such as rumble strips or speed humps
that force drivers to slow down.
Warning signs are probably most suited for use on
tourist roads where protection of fauna is valued
and expected.
VicRoads has a set of standard drawings for animal
warning signs are available on Exchange > Road
Management and Design.
Maintenance
Signage should be kept clear of overgrown
vegetation.
Can become damaged and will need replacing.
Kangaroo warning sign Mickleham Road (Source: VicRoads)
35
6.4.4 Other considerations
Light mitigation
Street lights and vehicle headlights can have both
negative and positive impacts depending on the fauna
species in question. Negative impacts include:
lights attract some fauna including bats as they
are drawn to food sources such as moths at night
illuminated areas potentially attract some species
onto oncoming traffic
some fauna actively avoid artificial light preventing
movement across the landscape
reduces habitat quality in surrounding areas
artificial light potentially increases stress levels
of fauna by changing normal animal behavior
and energy levels.
Light however is thought to have some positive impact
with species which are sensitive to light as it prevents
some animals from heading onto the road. Target species
for light mitigation include frogs, gliders and turtles.
It should be stressed that there are still levels of
uncertainty on the overall effectiveness of light
mitigation, and further study in the area is required.
Limitations
Studies suggest that it has limited effect
on reducing roadkill.
Is not always consistent with the requirements
of other road safety initiatives.
Fauna relocation
Fauna relocation occurs when projects physically
capture and release fauna into alternative habitat sites.
Fauna relocation is a requirement of all projects where
construction impacts on native wildlife, or where the
capture and relocation of fauna is identified within
vegetation zones to be cleared. Fauna relocation:
ensures potentially impacted species are protected
relatively inexpensive
may reduce pain and suffering for individual animals.
Limitations
Can be species dependant.
Doesn’t necessarily address population issues.
Generally inappropriate for territorial animals.
For species that are sensitive to artificial light,
VicRoads Officers should consider:
using fewer streetlights (only where this does
not impact safety)
use streetlights with reduced intensity
consider using barrier mounds, or densely planted
vegetation to limit the intensity of street lights from
penetrating far into the road reserve
decrease the height of light poles
consider reducing glare from streetlights by using
flat glass aeroscreen instead of a reflector glass
cover in streetlights
use alternatives to lighting such as pavements with
light-emitting diodes or fluorescents paint
Increasing the reflectivity of signs and road stripping
(retro-reflectivity) can increase visibility for drivers
(QLD Roads)
Light mitigation can only have limited effect and does
not reduce roadkill. Lighting is one aspect that should
be considered with other forms of mitigation.
Example of one of several fauna crossings developed
along the Calder Freeway (Source: VicRoads)
36
Fauna sensitive road design guidelines
Appendix A. Types of fauna mitigation
Animal
Background
Road impact
Suggested mitigation
Amphibians
(frogs and toads)
Direct impact
Habitat creation including
frog pond and wetland
design.
Road projects often interact
with frogs such as the
Growling Grass Frog.
Growling Grass Frog
Amphibians are found in a
variety of habitats including
rivers, wetlands, trees and drier
terrestrial habitats such as
grasslands.
Different species are adapted
to different habitats with a
majority of species requiring
a mixture of aquatic and
terrestrial habitat.
Frogs are commonly
killed by road traffic.
Indirect impacts
Fragmentation - can lead
to isolation of populations
which may result in reduced
population sizes and an
increased risk of extinction.
Roads can also create
‘barrier effects’ which restrict
movements across roads.
Pollution - Amphibians
are at risk from absorbing
chemicals from pollutants
washing off roads. Chemicals
can retard tadpole growth,
damage their sense of smell
and poison adult species.
Wildlife connectivity should
be maintained where possible
to prevent mortality from
traffic collision.
Frog culverts should be
designed using specialist
advice. Generally speaking
frogs have low levels of
mobility so crossing zones
should be strategically placed.
All crossing zones will need
to be fenced using design
concepts listed in Section
6.3, page 31.
Predication – More vulnerable
when on the road due to
increased visibility on the
roadway.
Arboreal animals – such as
the Squirrel Glider, sugar glider
and Brushed tailed Phascogale
spend most of their time in the
trees and rarely move along
the ground.
Squirrel Glider
Brushed tailed Phascogale
Arboreal animals are well
adapted to living in the trees
and included a number of
endangered species.
Direct impact
Arboreal animals are
commonly killed by road.
Indirect impacts
Fragmentation - road,
construction often create
gaps in the canopy of trees.
Species such as possums may
therefore need to move across
the ground where they could
potentially increase rates of
roadkill.
Habitat removal – many
arboreal animals rely on the
hollows created by old trees.
By removing old trees through
construction activities, projects
are potentially removing
nesting sites.
Several mitigation options
exist including;
▪Where possible maintain
natural canopy connectivity
above the road to facilitate
crossing through branches.
▪If removing trees consider
the installation of canopy
bridges (Section 6.2,
page 24).
▪For species that glide,
canopy gaps should
not exceed their gliding
capacity. Glide distance
is dependent on a number
of factors including; the
glide starting height
(ie tree height) and the
size of the animal.
Nest Boxes – projects
removing old growth trees
with hollows should consider
replacing the hollow with
nesting boxes (Section 6.4.2,
page 33).
37
Animal
Grey Crowned Babbler
Background
Road impact
Suggested mitigation
Birds and Bats
Direct impact
Australia is home to a vast
array of bird and bat species,
many of which are unique to
this country.
Birds and bats are commonly
Animals that fly are affected
by road traffic.
Several mitigation options
are available including;
Birds have colonised almost
every habitat imaginable with
different species adapted to
different habitats.
In Victoria some birds
including emus malleefowl
and lyrebirds are ground
dwelling species that spend
all or a majority of their life
on the ground.
Indirect impacts
Fragmentation – loss of
connectivity and disturbance
of habitat mean many birds
must search for new territory.
The rates of mortality in some
species are high due to the low
flying nature of the species.
Behaviour – traffic noise
interferes with the acoustic
nature of some species, while
streetlights and headlights are
thought to interfere with the
vision of some species.
Attraction – A number of
conditions including storm
water treatment wetlands,
food plants on road reserves
and water that puddles on
the side of roads, attract birds
and bats.
Dwarf Galaxias
▪Where possible maintain
natural connectivity.
▪Consider bridge options
such as Slaty Creek
Underpass or land bridges.
Both options are suitable for
birds and bats as it is easier
to maintain vegetation
connectivity.
For ground dwelling birds,
underpasses such as bridges
and large culverts are suitable.
Natural substrates that
maintain continuous or near
continuous cover are best
(Section 6.1, page 15 and
6.2.3 page 28).
Fish
Direct impact
Mitigation methods include;
Freshwater fish in Victoria are
diverse and geographically
extensive however many native
fish have declined both in their
range and abundance during
the last 100 years and habitat
changes are thought to be the
major cause of the decline.
Roads themselves do not
directly impact fish species,
but road construction does.
Construction activities which
damage aquatic habitats,
impact water quality or
increase turbidity and erosion
into creeks are all detrimental
to freshwater fish.
▪Consider installing baffles
in new and existing culverts.
Fish such as the threatened
dwarf Galaxias are a concern
for VicRoads as many projects
interact with the species.
Indirect impacts
Roads constructed over
waterways have several
impacts:
▪Bridges can shadow riparian
zones and wetlands changing
characteristics and impacting
on vegetation.
▪Roads can change the
flooding characteristics
of waterways, while
stormwater runoff has
impacts on water quality.
▪Where culverts have been
placed under roads, water
velocities can change and
impact on the movements
of aquatic species (Section
6.4, page 21).
▪Create habitat such as rock
ramps which encourage
fish movement along the
waterway.
▪Avoid crossing waterways
near sharp bends, sections
of unstable banks or
naturally strong “riffle”
systems (Section 6.4,
pages 21 – 23).
Construction phase –
establish protocols for
the management of fish
populations at the beginning,
during and after construction.
Protective measures including
No-Go Zones should be
devised, the purpose of which
is to prevent encroachment
into and damage of the
aquatic habitat during both
temporary and permanent
construction works.
38
Fauna sensitive road design guidelines
Animal
Golden Sun Moth
Background
Road impact
Suggested mitigation
Invertebrates
Direct impact
Mitigation methods include;
Invertebrates are animals
without a backbone, and
usually have hard external
shells. Invertebrates are critical
in ecosystem function and
play important roles in the
pollination and seed dispersal
of a variety of native plants.
Road traffic has great impact
on the mortality of slow and
low flying invertebrates.
▪When designing land bridges
and underpasses for larger
species, consider designs
that cater for species such
as the Golden sun moth.
Threatened invertebrates such
as the Golden Sun Moth are a
concern for many VicRoads as
projects regally interact with
the species.
Koala
Indirect impacts
Reduced connectivity is likely to have significant
impacts for species living
along the ground.
Dust - pollution from
construction or along dirt
roads may impact on the
breeding cycle of some
moths and butterflies by
damaging mouthparts
and killing young and their
eggs (eg caterpillars). Also,
vegetation covered in dust
creates difficulties for plant
eating invertebrate species. ▪Landscape using habitat
plants which cater for
species such as the Golden
sun moth. Consider
planting species such
as Short Wallaby Grass
Astrodanthonia carphoides,
Bristly-Wallaby Grass A.
setacea, Lobed Wallaby
Grass A. auriculata and
Clustered Wallaby Grass A.
racemosa. With regards to
pollen, food and habitat.
In general landscape plantings
should use indigenous species
and should consider catering
for invertebrates.
Koala
Direct impacts
Mitigation methods include;
The Koala is a small bear like,
tree dwelling marsupial which
averages around 9kg in weight.
Koalas are commonly killed
annually by road traffic.
▪Koalas have been reported
using a number of fauna
crossing structures.
The Koala lives in social groups
and is quite widespread over
larger areas of Victoria. Their
‘home range’ consists of a
number of eucalypt trees,
some of which are ‘home
range trees’ and others that are
more ‘food trees’.
Of the 600 known eucalyptus
trees, only a small number are
eaten by the Koala.
Indirect impacts
Primary impacts - Koala
mortality from individuals in
search of habitat, especially
food trees.
Barrier effect - Koalas spend
large amounts of time in the
trees however unlike other
arboreal animals, Koalas often
come down and walk along
the ground. Roads and their
traffic act as a ‘barrier effect’ to
these movements.
Habitat removal - VicRoads
would also impact on
the habitat of the Koala
especially during times of
road construction when tree
removal is unavoidable.
▪Large culverts with dry
poles strategically placed as
high above the ground as
practicable is best (Section
6.3, page 17).
▪Consider bridge underpass
structures which maintain
trees and natural vegetation
(Section 6.1, page 15).
▪Land bridges designed with
the correct landscaping
including known Koala food
trees would encourage
these animals to cross the
road at strategic locations
(Section 6.2.3, page 28).
Fencing - Correct fencing
is required to channel the
animals to cross roads and
avoid animal/vehicle collision
(Section 6.3, page 30).
39
Animal
Background
Road impact
Suggested mitigation
Macropods – kangaroos
and wallabies
Direct impact
Kangaroos and wallabies
are the largest groups of
marsupials in Australia.
Fauna crossings should cater
for the size and movement
of the species.
Kangaroos such as the Eastern
Grey Kangaroo live and travel
in groups and typically graze in
open scrub and grassland.
Eastern Grey Kangaroo
Wallabies are more solitary and
tend to be found in areas with
thicker understory vegetation
and scrub.
Kangaroos and wallabies are
commonly killed by traffic on
roads. Kangaroos can cause
significant vehicle damage.
Indirect impacts
Attraction – moisture in
drier areas and freshly mown
grass are known to attracted
macropods to roadsides.
Barrier effect – macropod
species have defined
movement pathways. Roadkill
rates are highest where roads
and pathways cross.
Small to medium sizedmammals
(including echidna,
bandicoots and wombats)
Echidna
Small to medium-sized
mammals mainly travel along
the ground and many species
have adapted to varying
habitats and ecological
requirements.
In Victoria most small
mammals require areas of
thick vegetation; however
some animals including
echidnas and wombats live or
graze in areas where low level
vegetation is sparse.
Southern Brown Bandicoot
Mitigation includes;
▪Large culvert designs no
smaller than 3 metres
X 3 metres (Section 6.3,
page 16).
▪Bridge underpasses.
▪Land bridges should be as
wide as practical (Section
6.2.3, page 28).
Fragmentation – especially
where roads separate grazing
areas from waterways.
Mortality is highest on the
bends of roads.
Fencing – is critical in the
success of overpass and
culvert structures. (Section
6.3, page 30).
Direct impact
Evidence suggests that small
to medium-sized mammals
are known to frequently use
fauna crossing structures.
Small to medium-sized
mammals are impacted
greatly by road and their
traffic. Wombats and
bandicoots account for a
significant number of roadkill
along Victorian roads.
Wombat roadkill has been
associated with bends in
the road, presumably limiting
driver visibility.
Indirect impacts
Fragmentation - loss of
connectivity and disturbance
of habitat. High rates of
mortality are known to occur
in areas where vegetation
is found along the edge of
roadsides.
Barrier effect - Roads can
also create ‘barrier effects’
which restrict movements
across roads.
Existing culverts used for
other purposes (eg drainage)
in some cases have become
known fauna crossings. Both
wombats and echidnas have
been identified using such
structures.
Mitigation structures include;
▪Land bridge structures
are very successful in
encouraging crossing zones
(Section 6.2.3, pages 28).
▪Culverts and tunnels should
be designed with as natural
a substrate as possible
by using rocks, logs and
branches.
▪Natural and continuous
vegetation should be
maintained.
Fencing – is critical in the
success of overpass and
culvert structures (Section
6.3, page 30).
40
Fauna sensitive road design guidelines
Animal
Platypus
Background
Road impact
Suggested mitigation
Semi aquatic fauna
Direct impacts
Such as the Platypus and
Native Water Rat are air
breathing animals that live
in fresh water.
Construction activities can
disturb river banks, burrows
and nesting sites. Construction
activities which damage
aquatic habitats, impact water
quality or increase turbidity
and erosion into creeks are all
detrimental semi-aquatic fauna
The platypus has a home
range up to 4 – 5 km so it
is important projects do not
impede animal movements
during construction and after
construction.
In Victoria, the platypus can
be found in all areas except
for the north-west. While
the native water rat is more
wide spread.
Both species have webbed
feet and commonly shelter
in burrows on the banks.
Platypus usually cross roads
via culverts and pipes however
at times they have been
known to leave the waterways
and cross roads on foot,
sometimes getting run over in
the process.
Incorrect culvert design –
culverts that have strong water
velocity, and flow strong down
stream can get blocked by
debris because of inadequate
maintenance, impede
platypus and native water
rat movements.
Native Water Rat
Striped legless lizard
Indirect impacts
Reptiles (snakes and lizards).
Direct impacts
Are found all over Australia
in a wide variety of habitats
including semi-rural and
suburban locations.
Reptiles are commonly killed
by road traffic because they
often use roads to warm their
bodies.
All reptiles require the warmth
of the sun to maintain body
heat and as a result, a majority
of reptiles are active during
the day. In Victoria, many
reptiles hibernate over winter.
Indirect impacts
Connectivity – can be an issue
as some species avoid the
roads and adjacent disturbed
habitats.
Others become trapped on
the road by infrastructure
including gutters, noise walls
and other fencing.
Mitigation measures include;
▪The most effective aquatic
crossings are where culverts
and bridge underpasses are
as wide as possible.
▪Avoid culverts with a
concrete base. Instead
use a natural stream
bed considering three
sided culverts.
Culvert and underpass
designs for semi-aquatic
animals should follow
guidance under (Section
6.4, page 21-23).
Reptiles can have low levels
of mobility so fauna sensitive
road design should:
▪Provide a natural continuous
cover of vegetation, rocks
and branches leading up to
culvert structures.
▪Include furniture (Section
6.3, page 17).
▪Include mitigation measures
for semi aquatic fauna.
Measures most likely to be
suitable for reptiles include
land bridge structures and
bridge underpasses.
Fencing – fine mesh is
needed at the bottom 400 –
600 mm of any fauna fencing
when catering for reptiles.
41
References
Abson, R. (2004). ‘The use by Vertebrates of the Slaty
Creek Wildlife Underpass, Calder Freeway’, School of
Geography and Environmental Studies, University of
Tasmania.
Abson, R., Lawrence, R. E. (2003). ‘Slaty Creek wildlife
underpass study, Final Report.’ Centre for sustainable
regional communities, Latrobe University,
Bendigo: Kyneton.
Australian Government Department of the Environment
and Heritage (December 2008) Review of mitigation
measures used to deal with the issues of habitat
fragmentation. (Major Linear Infrastructure).
Bond, A. and Jones, D. (2006) Fauna use of Underpasses
and Land Bridges at Compton Road: Results for Six
Months Passive Monitoring. Report for the Brisbane
City Council. Suburban Wildlife Research Group,
Griffith University, Brisbane.
Environmental Institute of New Zealand (9th – 8th
May) Symposium Handbook – Breaking the Barriers:
Engineering Solutions to Ecological Problems
(Environment Institute of Australia and New Zealand).
Fairfull and Witheridge (2003). ‘Why do Fish Need to
Cross the Road? Fish passage Requirements for waterway
Crossings’. Available at dpi.nsw.gov.au
Robertson et al (2002). Hamer et al 2002) Robertson,
2002. Discussion Paper – Design requirements for
structures to ameliorate the potential effects on frog
movements of construction and operation of the
proposed Craigieburn Bypass. Wildlife Profiles Pty Ltd
Report for VicRoads.
Seiler, A. (2001). Ecological Effects of Roads – A review.
Department of Conservation Biology, Swedish University
of Agricultural Sciences.
Transport and Main Roads (2010) Fauna Sensitive Road
Design Manual, Vol 2. Preferred Practices. Queensland
Government. Available at tmr.qld.gov.au
Transport Roads and Maritime Services (2011). Wildlife
Connectivity Guidelines – improving wildlife connectivity
on RTS Projects. New South Wales Government.
Transport Roads and Maritime Services (2011). Wildlife
Connectivity Guidelines – Managing wildlife connectivity
on road projects. New South Wales Government.
Queensland Department of Main Roads (Qld Main
Roads) (2000) Fauna Sensitive Road Design Vol 1 –
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of Main Roads, Technology and Environmental
Devision, Brisbane).
keeping victorians connected
08.12 Authorised and published by VicRoads, 60 Denmark Street, Kew, Victoria, 3101.
For further information please phone 13 11 71
or visit vicroads.vic.gov.au