CATCHMENT RESTORATION AND
SUSTAINABLE URBAN WATER MANAGEMENT : A NEW PARADIGM
*Anne M. Powell and **Leslie Jones
*Birkby Hall, Cark in Cartmel, Grange over Sands, Cumbria LA11 7NP, United Kingdom.
E-mail: 100654.1073@compuserve.com ; ** Panda House, Weyside Park, Godalming GU7
1XR
ABSTRACT
This paper suggests a new paradigm; that sustainable development must first consider the
environment upon which economic and social factors ultimately depend and sustainable
management of the environment requires an integrated approach. It recognises that the basin, or
catchment, is the best unit for management and emphasises the interdependence of the urban and
the rural parts of each catchment. The paradigm recommends that management is best done using
the ecosystem approach which includes the human residents of the river basin as integral
components of the ecosystem, and dependent upon it. Restoring and rehabilitating the functionality
of ecosystems is the key to a sustainable future.
KEYWORDS:
Basins, Catchment, Ecosystem, Integration, Management, SUDS (Sustainable Urban
Drainage Systems).
SUSTAINABLE WATER MANAGEMENT
This paper is about restoring habitats, especially those associated with water. The case is
made that restoration based on the catchment ecosystem which aims to restore function has
many benefits, and that restoration can make a contribution to sustainable water management
in the urban as well as the rural context.
Since Rio people have struggled with the concept of sustainable development and
sustainability, usually taken to mean – “development that meets the needs of the present
without compromising the ability of future generations to meet their own needs.” (United
Nations, 1992). Deciding what actions are sustainable is difficult. Recently, the UK
Government has tried to turn the concept into action and has produced a “Strategy for
Sustainable Development for the UK – a Better Quality of Life” and a number of subsidiary
strategies. These papers contain messages suggesting there are three “legs” supporting
sustainable development, namely economic, social and environmental, and that there are
trade-offs between these three. In these papers and in other documents emanating from the
UK Government the environment is listed third, and the implication sometimes is that, of the
three, the environment might be optional. In reality the opposite is true, a healthily
functioning environment underpins the long-term, sustainable social and economic wellbeing
of people.
INTEGRATED MANAGEMENT AND THE WATER BASIN AS A UNIT OF
MANAGEMENT
It is sometimes suggested that sustainable development can be delivered through integrated
management. This is a common theme in policy statements from regulators, including the
Environment Agency for England and Wales. Its Corporate Plan states its primary aim is to protect
or enhance the environment and make a contribution towards the delivery of sustainable
development through the integrated management of air, land and water. The Finnish Environment
Agency is another example of an organisation which, by its structure and its range of
responsibilities (it deals with all facets of the environment), demonstrates the capacity for integrated
management.
Many environmental managers accept that water is best managed in an integrated way on the basis
of the catchment or the water basin. Integrated River Basin Management, or as in Agenda 21,
Integrated Water Basin Management, treats the river and its tributaries together with the land and
underground water as a unit. It recognises the need to manage the river basin as an entity, and
implies the importance of land use, as well as the value of ponds, lakes and wetlands within the
basin. Many authors agree, e.g. Nienhuis et al, 1998, that rivers constitute ecological continua from
the source, via upper and lower basins to the estuary and the sea. Although ecological connectivity
in basins of most large European rivers is weakened by human impact, (particularly dams and
weirs, and the disconnection of the river from its flood plain) there is benefit to be gained from the
consideration of the whole.
There are many examples of this way of thinking, referred to as “catchment consciousness” by
Newson et al (2000), which has the advantage of linking people and economics to the more familiar
technical aspects of water management. The same author gives examples of many others who have
advocated the catchment as a management tool and countries with catchment planning experience,
and indicates that adoption of the catchment as the basis for legislation and management is
happening in many parts of the world. Catchments are physically bounded, stable (unlike political
boundaries) and comprise functional entities. The catchment is central to the new Water Framework
Directive, which requires EU member states to develop administration and prepare management
plans for river basins.
Some authorities, probably in order to split problems into manageable sizes, appear to divide rather
than integrate. The World Water Vision, launched by the World Water Council in August 1998
developed “sector visions”; Water for People, Water for Food and Rural Development, Water and
Nature and Water in Rivers, which were discussed at the World Water Forum in The Hague in
March 2000.
The new paradigm, suggested in this paper, is that sustainable development must first consider the
environment upon which economic and social factors ultimately depend. It invokes an integrated
approach for catchment-ecosystem thinking, that is; recognition of the interdependence of the urban
and the rural parts of the catchment; the interactions between air, land and water; the importance of
relevant disciplines (including social and economic) and the interconnectedness of standing,
flowing and underground parts of the water system.
The paradigm recommends that this is done using the ecosystem approach, and that restoring
aquatic ecosystems is key to future sustainable management of freshwaters.
ECOSYSTEM STABILITY, HEALTH AND PEOPLE
The arguments for using the catchment as a basis for management together with the ecosystem
approach require explanation. The ecosystem concept assists in understanding the way in which
living organisms (including humans), non-living chemical and physical components and energy
interact. All ecosystems have characteristics in common. Firstly, they are largely self-contained
and most of the materials (such as nitrogen, phosphorus and carbon), re-cycle within the system.
Ecosystems are not completely isolated and relatively small quantities of materials and biota move
between them – in the case of adjacent ecosystems this occurs mainly at the edge or ecotone (for
example the sea and the land in the littoral zone).
Secondly, following the original idea of Lindeman (Deevey, 1984) the sun’s energy, which powers
each ecosystem, can be considered to flow through it. Sunlight is captured by plants in
photosynthesis, transformed from light energy into chemical energy and stored in the tissues of
plants to be released when the plant is consumed by herbivores or by detritivores or microorganisms when the plant is dead. All the levels in the food web use some of this energy for
respiration (thus liberating energy from the ecosystem in the form of heat) and pass some on,
usually about 10% of intake, to the next trophic (feeding) level.
An individual ecosystem has been likened to an engine and its continued “running” relies on an
energy supply and the availability of suitable materials (simple chemical substances) for plants to
grow. Materials (and energy) are passed on to herbivores and carnivores in the food chain during
which the chemicals are transformed into amino acids, proteins and other larger molecules of which
bodies are built. Decomposition pathways in the food web break large molecules down into simple
chemicals to be recycled once again. The implications of the above is that ecosystems (rather like
engines) have finite limits and can be measured in terms of inputs, efficiency and production. It also
implies that ecosystems re-cycle raw materials and, given an energy supply, are sustainable.
Ecosystems are diverse – they contain many species – their biodiversity. Equally important are;
genetic diversity within species; age groups within populations; habitat diversity and the number of
different niches or “life styles” available in an ecosystem. Some ecosystems are naturally and
inherently less biodiverse than others. For example, desert ecosystems are naturally less diverse
than tropical rainforests but in both cases, as the living components are studied and described their
interdependence becomes obvious.
Over the long-term (to human time scales) ecosystems are normally self-sustaining and seem
stable. They may have marked seasonal or cyclical changes but they only change slowly over
the years. Size affects stability and small lakes and ponds change more rapidly than larger
ones; filling in and disappearing to become land through a series of stages (succession).
Although they seem stable, even large ecosystems can change dramatically when they are
upset by large-scale natural events e.g. volcanic eruptions, meteoritic impacts, floods, fires or
by human impacts such as pollution, dams and irrigation on a large scale.
In the 60’s and 70’s, a number of authors (see Deevey, 1984), were working on small model
systems and discussed ecosystem stability, defining it as resistance to perturbation or homeostasis implying feedback and self-regulating mechanisms. The suggestion was made that diversity
influenced stability and that less diverse ecosystems were less robust and more likely to crash.
Some of this discussion related to lake systems where nutrient inputs, when increased by man,
appear to accelerate the evolution of a lake to a more eutrophic state, (anthropogenic
eutrophication). Eutrophic lakes have high biomass of fewer species and it was suggested that they
were unstable. The search was on for a quantitative theory of ecosystem stability. It is now
generally agreed that although eutrophic lakes do have less species diversity they cannot be said to
be unstable. Rather, they show a departure towards a new equilibrium which is reversible on
reduction of the driving stress as discussed by Bailey-Watts et al, 2000.
Although understanding is growing, we still do not know how much damage a catchment can take
before collapsing nor do we know how much water a river needs to avoid lasting damage.
Similarly recovery after treatment is unpredictable in both organisms and ecosystems. “Dead”
rivers, so described because no life could be seen, have come back to life (e.g. the River Thames).
Recognising that the basins on which we depend are damaged, it may be that rehabilitation and
restoration can contribute to restoring them to “health”; thus allowing further (sustainable)
exploitation.
Ecosystems are convenient, if complex, units for study. It has been argued (Newson et al, 2000) that
the best conceptual approach we have is the catchment scale ecosystem model and that removal of
the spontaneous regulation functions constitutes “damage”. It follows that the best route to
sustainable management is to restore the catchment ecosystem’s functionality.
A fundamental issue, which has been addressed by religions and traditions throughout history, is the
relationship between man and the rest of nature. A strong theme running through the classical and
Christian tradition is that humans are dominant over nature as presented in Ponting (1991). A less
arrogant attitude is growing as the recognition of the human dependence on nature emerges, but the
ecosystem approach demands that we see ourselves as part of a close knit system on which we
depend. The language of politicians’ sustainability rhetoric sometimes, unfortunately emphasises
the separation of man from the ecosystem, as reflected in the apparent allocation of “water for
people” as different from “water for nature” and reference to trade-offs between social benefits and
environmental benefits. Using the ecosystem approach encourages us to think of ourselves as an
important biological component, not as controllers.
CAN URBAN AREAS BE CONSIDERED AS PART OF THE ECOSYSTEM ?
Many cities, for example London, (6.9 million people) have made progress in improving water
quality over recent years by taking an integrated approach. London’s sewage system is now being
studied as an important part of the water cycle for the city with consideration being given to
artificial recharge of both the River Thames and some parts of the aquifer instead of the effluent
being lost by discharge to sea. Some propose that large urban areas could be considered as
ecosystems in their own right as the problems of urban areas, such as flooding and waste disposal,
appear at first sight to be unrelated to areas outside their limits. Also the characteristics of urban
areas seem to be different from undeveloped parts of a river catchment, for example the high degree
of modification of the recharge system in cities due to non-porous coverage of the soil. There may
be benefits from such an approach, but if it is true that catchments are functional entities, it may be
more fruitful to consider a city in the context of its total catchment ecosystem.
There has been a recent change in the institutional arrangements in London with the appointment of
a Mayor, who has a vision of London as a sustainable world city. His aim is to improve both the
quality of life for Londoners and London’s environment and, at the same time address London’s
responsibilities in terms of its use of resources and its effects on global climate change. He wants
London to lead the way in creating a world city for the 21st Century that combines environemtnal
enhancement, protection and habitat creation with innovation and modern design. Statements like –
“poor health and poverty are linked to the quality of the environment” and “a healthy environment
for a healthy population” underline his view that improvement in the environment will contribute to
the well-being of London’s citizens. The relationship between green spaces and human health is
increasingly realised; more than 20% of urban London is protected green space accessible to the
public.
Aspects of London’s environment are in need of attention but its quality is generally good. The
Thames is one of the cleanest metropolitan rivers in the world supporting over a hundred 100
species of fish and the estuary is internationally important for wading birds and wildfowl. The
recent re-establishment of commercial fishing for eel and marine fish species indicates that water
quality is suitable, and one of the best indicators of improvement, compared to the earlier part of the
20th Century, is the return of the Atlantic Salmon (Salmo salar). London recognises it has an
enormous asset in its river and the mayoral pronouncements include the suggestion that it is made
into a “Blue Belt” with special provision for its further protection and enhancement. London’s tidal
defences are amongst the best in the world protecting more than 150 square km of London.
The threat of flooding from the sea has always been present but has recently increased with the
recognition of possible sea level rise due to climate change and the gradual tilting of SE England. It
is estimated that the Thames Barrier, which has closed 39 times since 1983, may be needed 200
plus times per year by 2100. Flood risk from rivers in London, (compounded by rising ground water
in the London basin) and in upstream urban areas, is also increasing and it may be useful to look at
the entire catchment in which London lies instead of restricting oneself to the city alone. To some
extent this is already happening with the development of major schemes in the mid-Thames valley
such as the Maidenhead Flood Alleviation Scheme which embraces urban and rural areas and
creates a new river channel similar to the Thames, increasing biodiversity and protecting
Maidenhead.
London lies in the valley of the River Thames and its dependency on its catchment is considerable.
For example its water supply comes from all parts of the basin - from the Cotswolds to Surrey and
Bedfordshire and its waste is disposed of outside the City. Upstream water retention could have a
bearing on the flood risk to the city as could the behaviour of water in the city itself. The output
from the Mayor’s office includes reference to SUD’s (Sustainable Urban Drainage) schemes and
promotes SUDS in all new developments to reduce flood risk.
RESTORING CATCHMENT ECOSYSTEMS
In this section some major types of impact are considered together with the possibilities for
ecosystem restoration which could have an impact on urban areas.
Vegetation cover
Deforestation and growth in agriculture for over 5000 years in the UK has been dramatic and has
changed water quantity and quality. Currently 70% of the UK is agricultural crops and grassland,
10% is wooded (about half being coniferous), 10% urban and 10% derelict land and mineral
workings, (Robinson et al, 2000). On valley slopes changes in vegetation can result in instability of
soils and erosion, adding silt to watercourses which coats the stones and fills up the interstices
between the components of the substrate, changing its nature and the types of organisms it can
support, for example fish eggs and fry. Soil instability is compounded by a decrease in organic
matter content since the 50’s which makes soils more vulnerable to erosion.
Significant reforestation of parts of catchments and re-vegetating margins of the rivers (buffer
zones) has resulted in an estimated doubling of woodland in England since the 1930s. Tree planting
in the headwaters of the River Severn and other rivers in England is being undertaken in order to
protect the lower (often urban) parts of catchments. However, tree planting is not always beneficial
and there is still considerable debate about how woodlands influence river flows. Trees generally
have higher evaporation rates than grassland or arable land and this gives rise to fears that the
extensive reforestation planned for the English lowlands (Community and National Forests) may
reduce recharge of aquifers which are a major part of supply.
Ponds, wetlands and floodplains
River valleys have been consistently drained to make way for agriculture or for development so that
England is one of the most extensively drained countries in the world first. English Nature
(Acreman and Jose, 2000) concludes that since the 1930’s huge losses of wet grassland have taken
place especially in the southern and eastern parts of the country, for example 64% of the wet
grassland in the Thames Valley has disappeared. 75% of the ponds existing at the end of the 19 th
century have gone, and many that remain are impacted by pollution (Williams et al, 1998). Getting
the water off the land as quickly as possible with the aim of “improving” the land has cost UK
taxpayers huge sums of money in the last 100 years. The loss of wet meadows, water meadows,
ponds and wetlands (referred to as the “kidneys of landscape”) has reduced biodiversity and cost
society in lost products, functions and services, especially that of protecting downstream urban
areas, as shown by Acreman and Jose (2000). Although theoretically protected by a number of
conventions and regulations many wetlands in the UK are still at risk from abstraction.
Restoration of wetlands is popular and many good examples exist. This is done by reconnecting the
flood plain with the river, allowing over-topping so that flood meadows are revived, non-renewal of
under-field drainage in selected catchments, (or parts of catchments) and digging still waters temporary and permanent. The usual motive for aquatic habitat restoration is for wildlife
enhancement purposes, although ponds and artificial wetlands are being increasingly constructed in
connection with flood alleviation schemes and to improve water quality. Ponds, because many have
small catchments, can easily be protected and restored. Recent work has shown that ponds support
more species and more unusual species of conservation importance than rivers so these restorations
are of particular biodiversity significance. Many ponds are being created by community and NonGovernmental Organisations projects (such as those of the Ponds Conservation Trust, in the UK)
for amenity and education, and by local authorities and water undertakings to balance flood flows in
urban areas and to assist “source control” of pollutants. These new small water bodies are often
used for many activities, including fishing and shooting.
Changing the course and shape of rivers
The River Habitats Survey (Raven et al 1997) showed less than 10% of the river reaches sampled in
England and Wales were unmodified. Straightening, widening, and deepening rivers was, like
wetland drainage seen as an “improvement” as it helped to transmit water more quickly
downstream. The industrial revolution resulted in thousands of dams, mill lakes, weirs and sluices
being constructed interfering with the behaviour of rivers and wildlife, particularly fish.
Straightened and deepened rivers are remarkably unattractive, contain low species diversity, support
less valuable fisheries and increase the risk of flooding for downstream sections of the same system.
There is a large literature on river restoration techniques (Royal Society for the Protection of Birds,
1994). Most authors agree that river restoration has many benefits and is being widely undertaken.
In some case it can be inexpensive for example, excluding grazing animals from riverbanks allows
plants to grow and the channel to narrow and meander, cleaning gravel and encouraging fish. Re-
meanders can be brought about by “letting the river go” to find its natural bed, although in low
energy channels active restoration is required. A meandering natural river holds more water and
protects urban areas downstream as well as having lower maintenance costs. At present in the UK
the maximum advantage is not achieved because schemes are small, often exclude the floodplain
and are hardly ever catchment-wide.
Restoring function to flood plains
Relatively recently, housing and industrial development has had a particularly important impact on
many catchments in Western Europe. The floodplain is economically attractive for building because
the land is flat. However, the cost of protecting from floods (dikes and bunds) is high and, when
upstream development expands or other factors increase flood risk, the cost becomes even higher.
Maintenance and upkeep costs are a liability on future generations The major problem is that
development in the flood plain greatly reduces its capacity for storing water and usually involves
covering the ground with impervious surfaces, speeding up run-off and adding to downstream
problems. The water quality of the run-off from concrete and asphalt surfaces, especially when
storms follow a dry spell, is poor. Storm waters are usually directed away from sewage works,
which would be quickly overwhelmed, and go straight into the river.
Flooding in the UK, Ireland, Italy, Spain and France in recent years has highlighted the impact of
climate change and the importance of the Kyoto principle. The meeting of signatories to the United
Nations Convention on Climate Change in The Hague (Nov 2000) failed to reach agreement but
indicated that, contrary to the commitments made by EU countries, the levels of greenhouse gas
emissions in most Member States are set to rise. It is estimated that there will be an overall increase
of 6% by 2010 which may imply an increase in the frequency and severity of flooding in some
places and demands re-thinking strategies for flood alleviation.
It is interesting to see how far utilisation of the natural floodplain and channel processes can be used
to manage flood waters as opposed to using “hard” engineering solutions. In the UK there have
been recent recommendations from aprliamentary committees that there should be a clear
presumption against future development on flood plain land and the European Parliament has
recently called on national governments to update their legislation so as to prevent unsustainable
spatial planning.
The Environment Agency is being encouraged to intervene in all stages of the planning process in
such a way as to deter inappropriate development. The recommendations encourage building on
derelict land in flood plains (brownfield sites) if adequately defended against floods. However,
these sites are usually porous until built on, after which they become impervious and this could
contribute to flooding problems unless they are adequately provided with porous surfaces.
Sustainable Urban Drainage Systems (SUDS)
This approach aims to bring water back into the community and considers all aspects of amenity,
flooding, pollution, biodiversity, landscape, safety and water resources. It is another example of an
integrated approach to water management. In urban parts of catchments SUDS schemes intercept
rain as near the source as possible and store it for use. Schemes include porous car parks and paved
areas that re-connect surface water with ground water and aquifers whilst, at the same time reduce
risk of flooding. SUDS are techniques that move away from traditional piped drainage systems and
mimic natural drainage processes. They are widely considered to be a good idea and the technology
is not difficult to apply. The main obstacles to their widespread use are administrative, namely the
questions of liability and long term maintenance. In the UK new Planning Policy Guidelines (PPG)
will replace of the present DOE (Department of the Environment) Circular 30/92 “Development
and flood risk” which requires local authorities to take flood risk consideration into account in
determining planning applications. The new guidelines make a presumption against development in
the flood plain and will ask local authorities to encourage the use, adoption and maintenance of
SUDS. The law (planning control, building regulations and land drainage) will also need to be
overhauled to allow the construction of, and maintenance arrangements for, SUDS when new
developments take place. The question of retrofitting schemes in existing urban developments will
also need to be addressed.
Some ecological survey work has been done on SUDS ponds (Biggs, personal communication) in
order to assess their value. The main conclusion of the work is that SUDS ponds have considerable
potential to deliver ecological benefits in addition to their functional and aesthetic benefits,
particularly if care is taken over their site design, location and planting regimes.
CONCLUSIONS
Unmodified rivers which are hydrologically connected to their flood plains have a patchwork of
habitats forming a complex and diverse ecosystem with many self regulating functions that have
benefits for flood peak attenuation, sediment storage and nutrient recycling. Man’s interventions in
catchments, generally result in ecological, social, economic and aesthetic impoverishment, and are
examples of non-sustainable activities, compromising the future and costly. One might say that
cities, considered on their own and from an ecological point of view, are also unsustainable.
Further, interventions (often engineering-based) of the past to solve flooding and other water
problems have sometimes created problems of their own. There are signs that things are changing;
large-scale projects are increasingly out of favour and programmes and innovative, smaller scale
and “soft” engineering solutions which are ecologically valid are proving as effective, and
sometimes cheaper, than “hard” engineering. These approaches are working with the water system,
not against it, but we need to go further.
To achieve sustainable management of freshwater we need a new paradigm – to regenerate the
system to as near a natural state as possible. The action required is to strengthen and restore
ecosystems using a more natural, ecological approach to repair and restore catchments. Restoring
the health of catchment ecosystems includes reforestation, renewal of wetlands, ponds, wet
meadows, allowing natural recharge of soil water and aquifers to take place. Restoration should aim
to retain water in the catchment, stabilise soils, reduce sedimentation, maximise infiltration,
recharge aquifers, and reduce surges and amplitude of river hydrographs. The benefits of this
approach will be increased stability and sustainability. There are economic benefits, including more
clean water, flood protection, the saving of maintenance money for flood defence and improved
fisheries. Climate change brings all of these matters into higher relief. Translating the effects of
climate change into impacts depends on how the water is managed and catchment restoration is
only one (at present under-utilised) form of management, but it deserves consideration.
As others have pointed out there is no absolute baseline against which to measure anthropogenic
effects in catchments and research into land use impacts on water resources is needed to achieve an
integrated understanding of water ecosystems. Most importantly, a robust scientific understanding
of the interactions between ecological, hydrological and geomorphological processes across the
catchment is required, with cost benefit knowledge of the long-term responsibilities of future
generations.
We have to accept that there are three inter-related factors for sustainable development; social,
economic and environmental. People’s attitudes and economic systems can change and are under
human control whereas the environment can only be managed within certain limits. If these are
exceeded we suffer. There is more importance in understanding the “ecosystem facts of life” than
the “economic and human behaviour facts of life”. It has to be clear that the environment is the
least negotiable factor, not one to be dispensed with in the face of high costs.
Restoration of ecosystems is already happening now but in a small scale and piece-meal way
because the implications of a healthy ecosystem have not been widely realised and the way in
which grants for habitat work are obtained mitigates against “joined up” activity. Many schemes
have concentrated on individual water bodies, stretches of streams, small areas of wet grassland or
marsh; the entire catchment seeming to be too ambitious, too expensive or someone else’s
responsibility. Farmers change land-use in a catchment in a largely piece meal way as individual
firms respond to changes in legislation and market forces, there being no inducement for them to
co-operate.
To achieve catchment-wide demonstrations of the benefit that can accrue, estates or owners with
control over entire catchments should be targeted. The need to invest to strengthen river catchment
ecosystems must be articulated more actively to politicians and the public, pointing out that this is
not a peripheral exercise but enlightened self-interest. Perhaps Europe should launch a decade of
ecosystem restoration – a programme to strengthen catchments (rural and urban) in a holistic way?
This could form part of a fully integrated catchment restoration initiative tackled through a process
of public participation based on catchment plans of the type proposed in the Water Framework
Directive.
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