WHY REHABILITATE URBAN RIVER SYSTEMS?
Sophia Jane Findlay1, Mark Patrick Taylor2
1
Department of Physical Geography, Macquarie University, NSW 2109, Australia
Ph: 02 9850 8344; Fax: 02 9850 8420; [email protected]
2
Department of Physical Geography, Macquarie University, NSW 2109, Australia
Ph: 02 9850 6319; Fax: 02 9850 8420; [email protected];
www.es.mq.edu.au/physgeog/staff/mt
Accepted in March 2006 for publication in the journal Area http://www.blackwellpublishing.com/journal.asp?ref=0004-0894&site=1
1
Abstract
This paper addresses the philosophical question: ‘why rehabilitate urban river
systems’ within an Australian context. Rehabilitation of river systems has become an
important objective of many local, state and national governments around the world,
who allocate substantial investment into various river projects. An understanding of
the various factors influencing stream condition and potential rehabilitation options is
essential in order to determine how the process is undertaken, and how success is
measured. This paper examines the triple bottom line (economic, social and
environmental) factors that influence decision-making with respect to urban stream
rehabilitation and management and considers their relative value and importance.
Keywords: Australia; Legislation; Prioritisation; Rehabilitation; Rivers; Urban
2
Introduction
Urban river systems are often heavily degraded, a situation that is not confined to a
particular geographic region of the world, but common to all areas subject to
urbanisation (Morley and Karr 2002). Initially, such waterways were managed as a
resource for human benefit including water supply, flood mitigation, disposal of
wastewater and minimisation of disease (Walsh 2000; Paul and Meyer 2001; Morley
and Karr 2002). However, this has led to the degradation of stream ecological
functioning, an issue that was initially ignored (Paul and Meyer 2001). In recent
decades the world has witnessed many reforms in the way the environment is viewed.
The physical integrity of the world’s freshwater ecosystems is now an important issue
and supported by many international, national and regional programs and legislation.
Tangible socio-economic or biophysical reasons for why urban streams should be
rehabilitated are often hard to identify, since maintenance of ecological integrity and
ecosystem services are not readily achieved or are identifiable in urban areas.
Questions relating to social, political and economic issues can be extremely relevant
in these urban stream systems where ecological integrity is compromised for flood
mitigation and waste water control. Frequently the solutions to these questions are
specific to individual situations, however collectively they are integral to the
overriding question which is to determine whether or not urban river rehabilitation is
justified. Urban stream rehabilitation decisions are usually dominated by conflicting
triple bottom line pressures of social (including political), economic and
environmental factors. These factors are gaining increasing significance in many
fluvial areas, including dam management as outlined by Graf (2005) and emerging
water management policies such as the European Water Framework Directive (WFD)
(European Commission 2000). This paper discusses the issues that arise from the
conflicts between these drivers, and examines the justification for the rehabilitation of
urban stream systems within the Australian landscape, however the specific examples,
3
discussions and implications outlined here can be extended to other areas of the
world, particularly where they have previously been explored (eg, Graf 2005), or
where tools such as the WFD are in force.
In addressing the arguments for and against stream rehabilitation, the following major
variables are considered: physical integrity (hydrology, geomorphology, water quality
and ecology); political; social; and economic determinants.
What is an urban stream?
‘Urban’ has been defined as vaguely as ‘built up’ (Erskine 1992) to as precisely as ‘an
area with >2500 people (620 individuals/km2)’ (USBC 1995), depending on the
context in which the term is being defined (McIntyre et al. 2000). Since there is not
one generally accepted term to define ‘urban’ the following definition will be used to
describe what is meant when the term ‘urban stream’ is used:
‘A stream where a significant part of the contributing catchment consists of
development where the combined area of roofs, roads and paved surfaces
results in an impervious surface area characterising greater than 10% of the
catchment.’
The value of 10 % impervious surface was used because it is accepted that this
amount of catchment imperviousness commonly results in the degradation of stream
systems (Beach 2003; Ladson et al. 2004).
What is Rehabilitation?
Rutherfurd et al. (2000) provide a summary of the definitions associated with
restoration and rehabilitation. The relationship of rehabilitation to ecosystem structure
and function is schematically represented in Figure 1. In Australia these definitions
are generally accepted by practitioners (Abernethy and Wansbrough 2001; Bennett et
4
al. 2001; Brierley and Fryirs 2001; and Brooks et al. 2001). Restoration describes the
return of a system to a fully recovered natural ecosystem. In contrast, rehabilitation
describes a condition along the same vector as restoration, where elements of the
natural biophysical system are returned, but not all (Rutherfurd et al. 2000). For
example, restoration projects may effectively target channel morphology and riparian
vegetation, but not the magnitude and frequency of flows, often an essential step for
achieving complete stream restoration. The final definition, and probably the most
important and pragmatic solution for the majority of urban river systems, is that of
remediation, where a river is managed to develop along a different vector of
ecosystem improvement (Fryirs and Brierley 2000). Although this process does not
result in total restoration of a system, it promotes improvement in terms of increased
ecosystem function and species richness.
INSERT FIGURE 1 HERE
In this paper the term rehabilitation is used to describe ‘ecosystem enhancement’, as it
is shown in Figure 1, rather than the ultimate goal of complete system recovery
(restoration). Rhoads et al. (1999) viewed this issue in a similar way however,
referring to the process as ‘stream naturalisation’.
Physical Integrity
Riverine management has evolved from a predominately engineering focus towards
one where geomorphology and ecology is now taking a more prominent role in the
decision making process (Hooke 1999; Douglas 2000; Logan 2001; Morley and Karr
2002). The physical integrity of a stream is now seen by many as the fundamental
scale on which to base river rehabilitation (Brierley and Fryirs 2000; Taylor et al.
5
2000; Lake 2001; Gregory 2002). Features that were once considered expendable in
order to ensure human assets (Hooke 1999) are now considered assets in their own
right. These include stream ecology, stream hydrology, stream geomorphology and
water quality. Recently, these aspects have formed the basis of many river
classifications (Whiting and Bradley 1993; Rosgen 1994; Chessman 1995; Brierley
and Fryirs 2000), including those specific to urban areas (Anderson 1999; Gregory
and Chin 2002; Chin and Gregory 2005). As such, it is essential that the complex and
influential impacts of urbanisation on stream characteristics and processes (Nanson
and Young 1981; Morley and Karr 2002) is thoroughly understood.
Stream Hydrology
The hydrological characteristics of urban catchments are often a primary determinant
influencing how a system, as a whole, responds to urbanisation. Increases in the
impervious surface cover that accompanies urbanisation alters stream hydrology,
forcing runoff to occur more readily and quickly during rainfall events, thus
decreasing the amount of time it takes water to reach streams (Leopold 1968; May et
al. 1997; Finkenbine et al. 2000; Paul and Meyer 2001; Walsh et al. 2001). This
process subsequently increases the flows for any given rainfall event, causing runoff
of peak flows with a recurrence interval of 2 years to increase by factors of two, three
and five with 10, 15 and 30 percent impervious development respectively (Hammer
1972; Hollis 1975), or a 1 in 5 year event occurring twice a year (Wong et al. 2000).
The decrease in the amount of infiltration results in a reduction in the amount of water
that is being recharged to groundwater systems, causing additional impacts to stream
ecological health via a decrease in the base flow of a system (Paul and Meyer
2001).Thus, as a consequence of urbanisation, changes to the form and function of a
stream system are inevitable.
6
The increase in the amount, and ‘peakiness’, of flows in urban areas is seen to cause
many detrimental effects to the geomorphology, water quality and habitat value of
urban streams. Consequently, discharge (quality and quantity) is often the focus of
restoration activities (Walsh 2004). While it is often unrealistic to significantly
decrease the amount of imperviousness that is present in established urban areas, the
concept of “effective impervious area’ (EIA) (the area of impervious surfaces
connected directly to natural drainage systems (Booth and Jackson 1997)), has
recently been identified as a significant factor in determining the hydraulic
characteristics of a system (Walsh 2004). Recent research in Melbourne, Australia,
has indicated that some positive benefits may be gained by retrofitting catchments
with systems designed to capture and delay peak runoff and increase infiltration
(Ladson 2004). However, the application of EIA as a proxy for stream condition is
only in the initial phases of development.
Water Quality
Water quality of urban streams, particularly with respect to pollutants is often the
most variable characteristic of stream health and a significant control of overall
condition (Paul and Meyer 2001). The quality of water, both in chemical and physical
terms, is often a limiting factor on the abundance and diversity of stream ecological
systems and on how the stream can be used for recreation (Paul and Meyer 2001).
Indeed, urban runoff is often thought to be no better than secondary treated effluent
(Ellis 1979). This is often the case in Sydney, Australia, where the capacity of
sewerage systems is exceeded during peak flows, resulting in overflows to creeks and
rivers. Rehabilitation programs focussing on water contamination are popular as they
often have a simple cause and effect relationship and solutions are relatively easy to
implement. For example, factories or sewerage treatment plants often produce point
source pollution that can be directly alleviated and gross pollutants can be detained
7
using various traps, such as sediment and water detention basins and end of pipe
netting, depending on the issue at hand. However, non-point source pollution is more
problematic and the costs of rehabilitation need to be carefully weighed against the
value of improvements that can be achieved for a system. Costs may include
educating a community about non-point source pollution in addition to the hidden
costs absorbed by the community when behavioural changes to their lifestyle are
required to facilitate environmental improvements. Despite these costs and
limitations, it is important to note that the rehabilitation of water quality is essential if
other factors such as recreation and ecology are to be enhanced (ANZECC 1994).
Stream Geomorphology
Wolman (1967) observed that a cycle of sedimentation and erosion takes place during
the construction and development stage of urban catchments. Neller (1988) found that
although there was an increased rate of erosion in the urban system studied, it did not
necessarily mean that the urban stream was inherently unstable, but adjusted to a new
state of ‘equilibrium’. The changes in the rate and magnitude of sediment delivery
cause urban stream systems to reach a new state of stability, or a ‘response’ state over
time, as conceptualised in Figure 2. The suggestion that a fluvial system is in a state
of equilibrium is problematic because rivers are an inherently disturbed environment
(Schumm and Lichty 1965; Stevens et al. 1975; Hughes and Rood 2001),
nevertheless, the new regime should form the focus of rehabilitation plans. It is highly
unrealistic to expect a return to the pre-existing, non-impacted condition due to the
irreversible changes in catchment boundary conditions (impervious surface area,
hydrology, vegetation cover, etc). Thus, rehabilitation programs in such
circumstances should focus on creation or naturalisation in order to improve the
health and value of a system (Rhoads et al. 1999).
8
Simplification of channel structure, often associated with the removal of large woody
debris and dredging, will result in a dramatic decrease in the habitat value of a stream
(Brooks et al. 2003). Available habitat is often seen as a limiting factor for urban
stream health (Moses and Morris 1998) and in many rehabilitation schemes the focus
is on returning habitat characteristics to the system in the hope that ecological health
will improve (Rosgen 1994; Morris and Moses 1999; Brierley and Fryirs 2000;
Gregory and Chin 2002). However, simple improvements in the habitat value of
stream systems will not necessarily produce the desired improvements in ecological
health because habitat value alone is not the sole determinant of stream ecological
health (Walsh and Breen 1999). Therefore, management plans need to recognise the
range of potential limiting factors in order to set realistic goals (Morley and Karr
2002). Some considerations may include the antecedent conditions of the landscape,
magnitude and frequency of events along with the various hydrological and
geomorphic characteristics of the system. These local characteristics and processes
must be understood in order to implement effective planning strategies.
Essential urban infrastructure both affects and is affected by the geomorphic
adjustments of stream systems. Issues regarding the stability of infrastructure such as
bridges, cables and stormwater pipes are often important in urban stream
rehabilitation scenarios, influencing the aims and potential outcomes of a project.
Thus in terms of geomorphology there is often a complex list of competing
requirements. These include the need to rehabilitate urban streams, or at minimum
ensure that they do not deteriorate and destabilise civil infrastructure, preserve useful
land by mitigating erosion and controlling flooding, and provide suitable habitat for
the ecological communities that may be present.
9
These relationships are further complicated by natural disturbance, such as flooding,
upon which many species depend on in order to survive and propagate (Fox 1990;
Hughes and Rood 2001). This is contradictory to the aims of traditional best
management practise that endeavours to keep disturbance to a minimum (eg. flood
mitigation). Thus, in urban situations a balance between minimising anthropogenic
disturbance whilst maintaining natural disturbance patterns exists.
INSERT FIGURE 2 HERE
Stream Ecosystems
Traditionally the ecological health of urban streams was given little attention relative
to social and economic concerns. However, in recent years the concept of ‘sustainable
development’ (SD) has taken a prominent position in the international arena. This is
epitomised in the international report Our common future (Bruntland report) (WCED
1990), which has helped emphasise the importance of maintaining healthy
ecosystems. Consequently, the lack of consideration towards the ecological health and
functioning of stream systems was deemed unacceptable. This resulted in a shift in
attitude toward the value and methods of river management. Therefore, no longer can
urban stream rehabilitation be a reaction to a crisis, but proactive management
systems are required that account for ecosystem value and significance (Morley and
Karr 2002).
One of the principle problems of focussing on the natural ecology of an urban riparian
area is that urbanised systems are commonly devoid of the most sensitive and rare
species due to the prevailing unnatural disturbance regimes that encourage invasion
by noxious species (Naiman and Decamps 1997). In order to overcome this limitation,
10
these areas need to be connected to near-intact reaches that can serve as species
sources to support and sustain re-colonization, and ultimately rehabilitation (Palmer et
al. 1997; Brierley and Fryirs 2000; Morley and Karr 2002). The liner aspect of
riparian corridors is often viewed as an important characteristic as these provide a
potential to link isolated habitats and populations (Eckstein 1984; Gardiner 1991),
whilst simultaneously controlling the movements of water, nutrients, sediment and
species (Malanson 1993; Forman 1995). The connective nature of many urban
riparian systems means that in essence they can be viewed as ‘bio-highways’.
Remnant riparian zones act as ‘bio-highways’ because they are often the only areas of
the urban landscape where many naturally occurring species can live and migrate
(Eckstein 1984; Gardiner 1991). Acknowledging these links is critical to ensuring that
rehabilitation strategies are successful. Areas that are connected to near-intact reaches
have a greater likelihood of success as flow and sediment are likely to be in balance
(Brierley and Fryirs 2000) and native species more likely to migrate as the linkages
between areas are exploited.
In Australia, the rehabilitation of urban stream systems to pre-European diversity and
abundance is often an unrealistic goal due to the complexity of factors that impact on
their potential for existence (Walsh and Breen 1999). Instead of immediately
attempting to re-establish diverse ecological communities in already degraded urban
streams, funding and attention may be more effectively utilised if first spent on areas
that have not yet been subject to human landscape changes. In Australia, for example,
many of the freshwater macroinvertebrate species have been found to be highly
endemic (Chessman and Williams 1999). Thus, it can be argued that stream reaches
that remain largely free of negative impacts from the urbanisation process must be
high priority for conservation to ensure that endemic species and their communities
remain intact. Thus, these areas can be used as ‘source zones’, or cornerstone reaches,
11
aiding the rehabilitation of physical function or species (Brierley and Fryirs 2000;
Morley and Karr 2002).
The Lane Cove, Ku-ring-gai Chase and Garigal National Parks of Sydney are all
protected areas under the National Parks and Wildlife Act 1974 (NSW). These have
urbanised stream reaches contributing to their waterways and in some cases also have
parts of the sewerage system either within or adjacent to creek lines, such as those
described by Warner (2000), where any break could have devastating effects. The
impacts of urbanised streams on these areas can range from the hydrological impacts
of increased erosion or sedimentation, to reductions in water quality from sewerage
leaks and invasion of exotic plant species (Leishman 1990; King and Buckney 2000).
If these threats are not properly managed and mitigated at the source, they can cause a
significant decrease in the ecological integrity of the system with the potential to
propagate throughout the catchment. Although preservation is important and should
take priority, it is often hard to preserve an area that is being impacted from an
adjacent or neighbouring degraded area. Thus, while conservation of pristine and
near-pristine areas is important, it must be accompanied by rehabilitation of the
degraded areas to ensure that the biological and physical longitudinal connectivity of
‘bio-highways’ are preserved, enhanced and maintained.
Ecosystem services are another important benefit provided by healthy ecosystems in
urban areas that cannot be ignored. There are many different types of services that
allow ecosystems to contribute to the health and well being of urban residents, many
of which are outlined in Bolund and Hunhammar (1999). These services not only
include the ‘triple bottom line’ values but also recreational activities (Ehrenfeld
2000), air purification and interactions with the urban heat island effect (McPherson
et al. 1997). Therefore, any small improvement in the ecological integrity of an urban
stream will be beneficial because it will continue to provide, or even improve the
12
social amenity as well as the ecosystem services that are essential to urban riparian
corridors. The discovery that locally generated ecosystem services have a substantial
impact on the quality of life in urban areas (Bolund and Hunhammar 1999) is further
incentive and justification to initiate as many ecological improvements as possible.
Political Influences
In Australia, environmental programs, legislation and policy have become an
important political component in recent decades, as evidenced by the growing
legislative and policy framework regarding the environment. The most important
legislative controls for the New South Wales (NSW) environment, particularly
catchment areas, are shown in Table I. Table II details the most important policies for
NSW catchment areas. Environmental concerns were traditionally given minimal
consideration and it was not until the late 1960’s to early 1970’s that people started to
acknowledge that ecology and the natural environment has an intrinsic value, that is
“something that has value or worth in its own right rather than because it provides a
function or service for humans” (Harding 1998, 354). This was mainly because the
abuses of industrialisation and development paid for by the environment were
becoming increasingly evident, and resources that were taken for granted were rapidly
disappearing. Since the 1970’s, concerns voiced by both the general public and the
scientific community have resulted in a number of political controls being set up in
order to ensure that certain environmental aspects are conserved and improved rather
than degraded beyond the point of recovery. A classic example of the changing
environmental perspectives within Australian politics is the Lake Pedder and Franklin
Dam cases in the late 1960’s through to the early 1980’s. Widespread public
opposition to dam building in the Tasmanian wilderness resulted in the Federal
Government challenging the State of Tasmania in the High Court to its right over
environmental decisions. A decision in favour of the Federal Government meant the
13
cessation of the dam construction program on the grounds that it was being built in a
World Heritage area (Harding 1998). This landmark case signalled the beginning of
effective environmentalism in Australia.
Since environmentalism has become a major issue in global politics many
organisations and programs have been set up to deal with the issues and ensure
stakeholder concerns are acknowledged and accounted for during decision making. A
significant non-government global organisation is the United Nations Environment
Programme (UNEP), established in 1972. The UNEP aims to act as a “catalyst,
advocate, educator and facilitator to promote the wise use and sustainable
development of the global environment” (UNEP 2004). As a result, many global
programs such as the UN GEMS/Water Programme have been established, which
aims to promote sustainable use of the world’s freshwater systems (GEMS 2005).
Other influential reports and agreements include the Bruntland Report (WCED 1990),
the Kyoto Protocol (UNFCCC 2005) and the WFD (European Commission 2000).
These have been instrumental in determining political and social attitudes as well as
providing a catalyst for public and scientific debate, often resulting in enhanced
policy for improvement and protection of the environment.
In Australia, the Rivers and Foreshores Improvement Act 1948 (NSW) was initially
enacted to facilitate the removal of obstructions from rivers and foreshores and to
prevent erosion caused by tidal and non-tidal water. These development objectives
were countered to some extent by the supplementary objectives encapsulated within
the Rivers and Foreshores (Amendment) Act 1991 (NSW) which incorporated Part 3A
into the Act requiring a person or company to obtain permit for any activity that
obstructs or detrimentally affects the flow of a river. However, as part of the social
and political shift towards conserving and managing Australia’s resources, the NSW
Government has introduced the Water Management Act 2000 (NSW). The title of the
14
Rivers and Foreshores Improvement Act 1948 (NSW) indicates that the act is aimed
toward the ‘improvement’ of rivers and foreshores, which was often achieved through
the removal of obstructions (e.g. woody debris). In contrast, the Water Management
Act 2000 (NSW) is aimed towards to ‘ecological sustainable development,’ such that
it seeks to protect and conserve the water resources of the State. This newer act
reflects a paradigm shift in attitudes towards the environment.
Legislative definitions are often fraught with problems when viewed against the
realities of local landscapes. For example, one specific management problem
encountered within the New South Wales legislation (Rivers and Foreshores
Improvement Act 1948 (NSW), Water Management Act 2000 (NSW), Environmental
Planning and Assessment Act 1979 (NSW), Crown Lands Act 1989 (NSW)) states the
definition of a bona fide river (including inter alia streams, creeks, brooks etc.)
includes only streams with intermittent and perennial flow (Taylor and Stokes 2005a;
Taylor and Stokes 2005b). Consequently, many of the watercourses in NSW are not
automatically protected because in such a dry landscape, many have an ephemeral
flow regime and thus fall outside legislative and common law legal definitions. This
results in a range of subsequent problems covering inappropriate land use practices,
loss of riparian zones and sometimes the total loss of the drainage network to urban
development. Numerous disputes regarding the true definition of a river have to be
settled by the Land and Environment Court (Taylor and Stokes 2005a, Taylor and
Stokes 2005b), often at great expense to local councils, developers or community
groups. This legal ambiguity is one example where a lack of scientific involvement
with the development of legislation has resulted in the failure of legislation to provide
for the proper management and protection of a system.
Despite such shortcomings, the Local Government Act 1993 (NSW) does effectively
15
encourage integrated triple bottom line environmental management. Section (13:4c)
stipulates that local governments are responsible for producing State of the
Environment reports for the administrative area, effectively ensuring that
management is carried out under a SD framework . This process ensures that
environmental impacts are identified and accounted for through the development
application process, management plans are put in place, special projects carried out
and procedures to mitigate against problems established. However, despite such
positive regulations, the legislative shortcomings mentioned above reveal the need to
further integrate science, management and legislation.
INSERT TABLE I HERE
INSERT TABLE II HERE
Community Values
The intensity of environmental impact and the social value of Australia’s urban areas
is demonstrated by the fact that they represent 85 % of the nation’s population, even
though they only account for 0.5 % of the total land area (Warner 2000). Thus, in
urban areas, the community will have a significant influence on how urban streams
are rehabilitated, as catchments are much more densely populated than their rural and
forested counterparts. The importance of community participation in the stream
rehabilitation process is well documented. Many papers (Rhoads et al. 1999; Barratt
et al. 2004; Mc Donald et al. 2004) highlight the importance of engaging the
community in the environmental management process. In many cases, local
knowledge, attitudes, and requirements of a community with respect to a system are
extremely influential in developing the management options that are implemented.
Rhoads et al. (1999) stress the importance of exercising a bottom-up procedure
16
whereby watershed management is regarded as being fundamentally social in nature,
despite the dependence on science and engineering. Those involved in the
management process need to understand that communication with the community is a
necessity, not an option. The local community, often mobilised in groups such as
Bushcare, Landcare or Rivercare is commonly the main workforce that performs
rehabilitation. Therefore, their opinions, experience and knowledge are important in
resource management and the planning process (Rhoads et al. 1999). In some cases
the options available to managers following community consultation may not be ideal,
but they do encompass the combined scientific, technical and social issues that are
fundamental for socially acceptable and efficient environmental management
(McDonald et al. 2004). Community opinions on issues of environmental
rehabilitation are also politically influential. This was clearly demonstrated in the
Franklin dam case (Harding 1998).
In urban areas the recreational, aesthetic and civil aspects of riparian systems are the
primary concern for the community. Ecological priorities are also often highly
regarded however community desires are frequently dependant on the current state of
the riparian systems. In areas where there is a large amount of bushland and the
streams appear to be in a ‘natural’ state, communities are more likely to be
sympathetic towards ecological factors and be receptive to rehabilitation projects.
However, where streams systems are largely channelised and have minimal
resemblance to natural systems, flood mitigation and associated recreational activities
are more important. The most successful projects are those that integrate community
stakeholders and provide demonstrable improvements, such as the Bannister Creek
‘living stream’ project in south west Western Australia (Torre and Hardcastle 2004),
or those that perform surveys to gauge community aspirations, understanding and
17
views on the local environment in order to produce a more holistic management plan
(e.g. KC 2004; Chin and Gregory 2005).
Economic Constraints
One of the fundamental controls on the initiation and progress of rehabilitation is
project funding. Rehabilitation can only occur where funding is available, and where
funding ceases or is withdrawn, projects can be left incomplete and potentially
undermine any improvements. This is one of the problems that affected river
rehabilitation in the Lane Cove Valley, Sydney during the 1990’s (UBMC 1998),
leaving many of the rehabilitated reaches susceptible to re-infestation by weeds.
One of the many advantages of proposing stream rehabilitation in an urban setting is
the abundant resources (monetary and personnel) available due to the larger
population (Ladson 2004). Thus in urban areas, even if personal intrinsic ecological
values are relatively small, the total benefits associated with simultaneous enjoyment
from a large population can be quite substantial. Even in rural areas with a sparse
population can remediation be economically viable. Conservative willingness to pay
estimates are often more than adequate to cover the costs of rehabilitation initiatives
(Loomis et al. 2000). Many of the benefits that arise from the rehabilitation of stream
systems, particularly those in many urban areas, are highly intrinsic in nature and thus
cannot be directly associated with cost. Although they may not provide a direct
monetary economic benefit to the community, riparian systems are important for
recreation and aesthetics (enjoyment of a feature), existence (knowledge that a feature
is present) and bequest value (willingness to ensure availability for future generations)
(Loomis et al. 2000). An excellent example, from a rural situation, is the $300 million
agreement struck between the Federal, NSW and Victorian governments to restore 28
% of the natural flow to the Snowy River. In addition to the return of environmental
18
flows, a program involving the removal of noxious weeds and the re-establishment
native fish and appropriate geomorphic structure in the channel has been established
(DEH 2004). However, difficulties in estimating a monetary value for ecosystem
services, recreation, existence or bequest values often limit the validity of using this
approach to promote environmental restoration programs.
In rural areas a cost benefit approach, focussing on travel cost and willingness to pay
for a recreation service is one way of prioritising and evaluating community desire for
environmental rehabilitation (McDonald et al. 2004). Another common method used
to value the benefits of restoration in urban areas is the hedonic property method,
where the price of a home located near a system with improved water quality is
compared to that of a home located near a system with degraded water quality
(Loomis et al. 2000). An example of indirect benefit is the 17 % increase in value for
properties adjacent to a rehabilitated stream in Perth, Australia compared with other
properties in the area (Torre and Hardcastle 2004).
Conclusion
This paper outlines the range of factors that must be considered by Environmental
Managers when planning potential stream rehabilitation projects. While each of these
factors (e.g. social, political and environmental) can be considered as discrete entities,
in reality they are intimately linked (as conceptualised in Figure 3) and are interdependent. The significance, influence and linkages between these factors show that
collectively, they provide a sound justification for urban stream rehabilitation
projects. The demonstrable benefits that arise from integrating all of the
aforementioned factors within a decision-making process reveal that there are very
few reasons for not rehabilitating urban river systems. Even if a stream reach cannot
be returned to a natural non-impacted condition, in most situations there are good
19
opportunities improve the ecological functioning and within system linkage of an
urban river network. These outcomes can be achieved while simultaneously
minimising the impacts of development and adding genuine social and economic
value to the urban environment.
There are many valid and tangible reasons for the rehabilitation of urban streams.
Some of these factors are abundantly obvious and include for example, water quality
and erosion, while others are more obscure and less tangible, such as social and
indirect economic benefits, but are often equally important. It is the combination of
these factors (Figure 3) that determine whether or not a stream should be rehabilitated,
the level and extent to which the system should be rehabilitated, and the
environmental goals that are set. Ultimately, catchment managers are accountable for
waterway planning and associated outcomes need to be supported by value-based
judgments in order to justify environmental expenditure.
→ INSERT FIGURE 3 HERE
20
Acknowledgements
The authors would like to thank their colleagues who have contributed to the
development of their thoughts and ideas on the topic of urban rivers. We are
particularly grateful to Peter Davies (Ku-ring-gai Council, Sydney) for his
collegiality, feedback and general support with facilitating research into urban rivers
via Ku-ring-gai Council. Rob Stokes (Macquarie University, Business Law) is also
thanked for his assistance in clarifying the relevant legislation and policies at both
State and Commonwealth levels of government.
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Figure 1
Created/modified Ecosystem
Ecosystem Function: biomass
Original Ecosystem
Restoration
Remediation
Degradation
Rehabilitation
Partially Re-instated
Ecosystem
Degraded Ecosystem
Ecosystem Structure: species richness
30
Figure 2
Pristine/Nonimpacted river
system
Restored
condition
Point of irreversible change
A
B
Human Intervention –
created condition
Perturbation and
response condition
Human Intervention –
created condition
Vector of
degradation
31
Figure 3:
32
FIGURE CAPTIONS
Figure 1: A schematic diagram showing the distinction between restoration,
rehabilitation and remediation.
In this diagram the number of sides of each shape signifies the complexity of the system it represents
with original ecosystems displaying a greater biodiversity and complexity than created/modified
ecosystems. This diagram recognises that rehabilitation, although primarily a process aiming to reinstate the original ecosystem often does not succeed and thus may result in a created/modified
ecosystem. Ecosystem structure or species richness is represented by the number of different species
present within a system where a natural system has more diversity of species compared to when it is
degraded. Ecosystem function or biomass is represented by the number of individuals present within a
system and is essentially an indication of productivity (figure adapted and modified from Rutherfurd et
al. 2000).
Figure 2: A conceptual representation of the possible states and responses of a fluvial
system to human influence.
A and B in the diagram represent turning points along the vector of change from a pristine/nonimpacted river system to a degraded river system. At point A or anywhere along the vector a system
can continue to degrade, be restored or managed following human intervention. Below point A the
dashed line represents the vector of irreversible change due to human influences in the catchment.
Below this point, restoration to an intact river system is unlikely, due to irreversible and permanent
changes in catchment conditions (e.g. increases in impervious surfaces due to development). Along this
vector of irreversible change, theoretical turning points such as that represented by B are possible
where the system can either naturally adjust to the new boundary conditions (i.e. perturbation and
response condition), be managed and/or created by humans or continue along the vector of degradation
until the channel stabilises under a new ‘equilibrium’ (adapted and modified from Fryirs and Brierley,
2000).
Figure 3: A conceptual illustration of the different factors that combine to affect
management decisions relating to urban stream rehabilitation.
33
Table I: The main environmental Legislation regarding streams in NSW,
Australia
Level of
Government
Legislation
Purpose
Commonwealth
Natural Heritage
Trust of Australia
Act 1997
Manage environmental funds to conserve, repair
and replenish Australia’s Natural capital
infrastructure
Environment
Protection and
Biodiversity
Conservation
Act 1999
To protect the environment and streamline
national environmental assessment and approvals
processes, protect Australian biodiversity and
integrate management of important natural and
cultural places (DEH 2005)
Murray Darling
Basin Act 1993
The purpose of this Agreement is to promote and
co-ordinate effective planning and management
for the equitable efficient and sustainable use of
the water, land and other environmental
resources of the Murray-Darling Basin
Native Title
Act 1993
To provide for the recognition and protection of
native title, to establish ways in which dealings
may proceed (amongst others)
Rivers and
Foreshores
Improvement
Act 1948
Established to control development on riparian
lands (this act was repealed in January 2001)
National Parks and
Wildlife Act 1974
The conservation of nature and cultural heritage
Environmental
Planning and
Assessment Act
1979
The proper management , development and
conservation of natural and artificial resources,
including agricultural land, natural areas, forests,
minerals, water, cities, towns and villages for the
purpose of promoting the social and economic
welfare of the community and a better
environment
Land and
Environment Court
Act 1979
An Act to constitute the Land and Environment
Court and to make provision with respect to its
jurisdiction
Crown Lands Act
1989
Management of Crown Lands
Protection of the
Environment
Administration
Act 1991
To constitute the Environment Protection
Authority; to provide integrated administration
for environment protection and to require the
Authority to perform particular tasks in relation
to the quality of the environment, environmental
audit and reports on the state of the environment
Local Government
Act 1993
To provide the legal framework for an effective,
efficient, environmentally responsible and open
system of local government in New South Wales
State
(New South Wales)
34
(table I continued)
Level of
Government
Legislation
Purpose
Fisheries
Management Act
1994
The objects of this Act are to conserve, develop
and share the fishery resources of the State for
the benefit of present and future generations
Water
Management Act
2000
To provide for the sustainable and integrated
management of the water sources of the state
for the benefit of both present and future
generations
Catchment
Management
Authorities Act 2003
To ensure that decisions about natural resources
take into account appropriate catchment issues
Native Vegetation
Act 2003
To protect native vegetation of high conservation
value having regard to its contribution to such
matters as water quality, biodiversity, or the
prevention of salinity or land degradation
Natural Resources
Commission Act
2003
To establish an independent body with broad
investigating and reporting functions for the
purposes of natural resource management
35
Table II: The main environmental Policies regarding streams in NSW, Australia
Level of
Government
Policy
Purpose
Commonwealth
Commonwealth
Wetlands Policy
1997
For managing wetlands on Commonwealth land,
implementing commonwealth policy,
cooperation between all levels of government,
acting as a scientific basis for policy &
management and international action
State
(New South Wales)
NSW Sand and
Gravel Extraction
Policy for
Non-Tidal Rivers
Control the extraction of sand and gravels from
riverine systems
NSW Wetlands
Management
Policy1996
To encourage wetland management to stop
degradation and promote rehabilitation and
habitat improvements
NSW Estuary
Management Policy
1992
For the Protection of estuaries
NSW Weirs
Policy 1997
Established to help reduce and remediate the
environmental impact of weirs
NSW Groundwater
Dependant
Ecosystems Policy
- draft
Protection of groundwater dependant ecosystems
NSW Flood Prone
Land Policy
Aims to reduce the impact of flooding on
individual owners and occupiers of flood prone
property
NSW Coastal
Policy 1997
ESD of the coast through water quality
management, through monitoring, research and
protection
NSW Fisheries
Policy and
Guidelines –
Aquatic Habitat
Management and
Fish Conservation
1999
Identifies activities that impact on aquatic
habitats along with guidelines for appropriate
environmental assessment and management.
Also provides background information of
habitats and resources
NSW State Rivers
and Estuaries
Policy 1993
Sets out principles of sustainable management
to improve the management of rivers and
floodplains
State Environmental
Planning Policy
No. 14 (SEPP14)
Coastal Wetlands
For the protection of mapped wetlands
SEPP19 Bushland
Bushland in Urban
Areas
Protection of listed natural bushland areas,
requirement for development application
36
37