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WHY REHABILITATE URBAN RIVER SYSTEMS?

Sophia Jane Findlay1, Mark Patrick Taylor2

1Department of Physical Geography, Macquarie University, NSW 2109, Australia

Ph: 02 9850 8344; Fax: 02 9850 8420; sfindlay@els.mq.edu.au

2Department of Physical Geography, Macquarie University, NSW 2109, Australia Ph: 02 9850 6319; Fax: 02 9850 8420; mark.taylor@mq.edu.au;

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

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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

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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,

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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

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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.

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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.

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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

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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).

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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.

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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,

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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,

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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

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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

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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

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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

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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

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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

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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

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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 inter-

dependent. 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

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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

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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

Rehabilitation

Degraded Ecosystem

Partially Re-instated Ecosystem

Original Ecosystem

Created/modified Ecosystem

Degradation

Restoration

Remediation

Ecosystem Structure: species richness

Ecos

yste

m F

unct

ion:

bio

mas

s

31

Figure 2

Perturbation and response condition

Restored condition

Pristine/Non-impacted river

system

Human Intervention – created condition

Vector of degradation

Human Intervention – created condition

A

B

Point of irreversible change

32

Figure 3:

33

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 re-

instate 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/non-

impacted 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.

34

Table I: The main environmental Legislation regarding streams in NSW, Australia Level of Legislation Purpose Government Commonwealth Natural Heritage Manage environmental funds to conserve, repair Trust of Australia and replenish Australia’s Natural capital Act 1997 infrastructure Environment To protect the environment and streamline Protection and national environmental assessment and approvals Biodiversity processes, protect Australian biodiversity and Conservation integrate management of important natural and Act 1999 cultural places (DEH 2005) Murray Darling The purpose of this Agreement is to promote and Basin Act 1993 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 To provide for the recognition and protection of Act 1993 native title, to establish ways in which dealings

may proceed (amongst others) State Rivers and Established to control development on riparian (New South Wales) Foreshores lands (this act was repealed in January 2001) Improvement Act 1948 National Parks and The conservation of nature and cultural heritage Wildlife Act 1974 Environmental The proper management , development and Planning and conservation of natural and artificial resources, Assessment Act including agricultural land, natural areas, forests,

1979 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 An Act to constitute the Land and Environment Environment Court Court and to make provision with respect to its

Act 1979 jurisdiction Crown Lands Act Management of Crown Lands 1989 Protection of the To constitute the Environment Protection Environment Authority; to provide integrated administration Administration for environment protection and to require the Act 1991 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 To provide the legal framework for an effective, Act 1993 efficient, environmentally responsible and open

system of local government in New South Wales

35

(table I continued) Level of Legislation Purpose Government

Fisheries The objects of this Act are to conserve, develop Management Act and share the fishery resources of the State for 1994 the benefit of present and future generations

Water To provide for the sustainable and integrated Management Act management of the water sources of the state 2000 for the benefit of both present and future

generations Catchment To ensure that decisions about natural resources Management take into account appropriate catchment issues Authorities Act 2003 Native Vegetation To protect native vegetation of high conservation Act 2003 value having regard to its contribution to such

matters as water quality, biodiversity, or the prevention of salinity or land degradation

Natural Resources To establish an independent body with broad Commission Act investigating and reporting functions for the 2003 purposes of natural resource management

36

Table II: The main environmental Policies regarding streams in NSW, Australia

Level of Policy Purpose Government Commonwealth Commonwealth For managing wetlands on Commonwealth land, Wetlands Policy implementing commonwealth policy,

1997 cooperation between all levels of government, acting as a scientific basis for policy & management and international action

State NSW Sand and Control the extraction of sand and gravels from (New South Wales) Gravel Extraction riverine systems

Policy for Non-Tidal Rivers

NSW Wetlands To encourage wetland management to stop Management degradation and promote rehabilitation and Policy1996 habitat improvements NSW Estuary For the Protection of estuaries Management Policy

1992 NSW Weirs Established to help reduce and remediate the Policy 1997 environmental impact of weirs NSW Groundwater Protection of groundwater dependant ecosystems Dependant Ecosystems Policy - draft NSW Flood Prone Aims to reduce the impact of flooding on Land Policy individual owners and occupiers of flood prone

property NSW Coastal ESD of the coast through water quality Policy 1997 management, through monitoring, research and

protection NSW Fisheries Identifies activities that impact on aquatic Policy and habitats along with guidelines for appropriate Guidelines – environmental assessment and management. Aquatic Habitat Also provides background information of Management and habitats and resources Fish Conservation 1999 NSW State Rivers Sets out principles of sustainable management

and Estuaries to improve the management of rivers and Policy 1993 floodplains State Environmental For the protection of mapped wetlands Planning Policy No. 14 (SEPP14) Coastal Wetlands

SEPP19 Bushland Protection of listed natural bushland areas, Bushland in Urban requirement for development application Areas

37